The County of North JutlandManagement andrestorationof lakes in DenmarkLakePromoManagement andrestorationof lakes in DenmarkLakePromoMette Bramm & Inge ChristensenCounty of North Jutland Department of Aquaric Environment200623This report concerns the management and restoration of lakes in Denmark. Chapter 1 describes the state and development of Danish lakes and provides a status of past and present lake management and restoration efforts. Methods of restoration and loading reducing initiatives to be applied in lake catchments are pre-sented. The next two chapters of the report deal with administrative issues such as structure, legislation and bodies involved in Danish lake management, and a sta-tus is presented of the ongoing implementation of the EU Water Framework Directive. Chapters 4-6 focus on various aspects of lake restora-tion such as project funding and the actual restoration process, and a detailed description is given of the most frequently applied restoration measures in Denmark using the restoration project undertaken by the County of Aarhus of Lake Stubbe as an example. Finally, Chapter 7 provides a summary evaluating the effects of lake restoration, puts the fndings into a broader perspective and forwards suggestions as to areas in need of further development. The report was elaborated by the County of Northern Jutland as a part of the international EU project Lake-promo in which the County of Northern Jutland is the only Danish participant. Also a Danish version of the report is available. The Lakepromo partners comprise research institutions and regional authorities from Fin-land, Estonia, England, Germany, Hungary, Spain and Russia. All project partners will elaborate status re-ports whose results will be summed up in a conclusive report. This report will serve as the basis of transfer of experiences and knowledge on lake issues between all the Lakepromo partners and thereby between EU countries and Russia.Lakepromo is carried out within the framework of the EU INTERREG IIIC North, which supports transna-tional cooperation between the regional authorities of the EU and border countries. The overall purpose of the project is to promote transnational cooperation on aquatic issues with special emphasis on initiatives de-signed to improve the water quality of lakes, wetlands and other aquatic ecosystems in accordance with the demands of the EU Water Framework Directive.The County of Northern Jutland wishes to thank all parties involved. A special thanks is given to Martin Sndergaard, the National Environmental Research Institute, for his contribution to Chapter 7. We are grateful to Jacob Peter Jacobsen and Jette Mikkelsen, Bio/consult, for their contribution to Chapters 3 and 6, and to the County of Aarhus for their contribution to the section on Lake Stubbe. PREFACE45CONTENTSPrEfACE31. BACKGROUND71.1 The characteristics of lakes suffering from eutrophication in Denmark. . . . . . . . . . . . . . . . . . . . . . . . . . . 81.2 Development of the condition of lakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.3 History and current scope of lake management and restoration in Denmark . . . . . . . . . . . . . . . . . . . . . . 111.4 Current practices and methods available for lake restoration and external nutrient loading reduction . . . . . 122. ADmiNistrAtivE struCturE AND lEgislAtioN iN thE lAkE ArEA152.1 Administrative structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152.2 Essential national legislation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.3 Current state of the national implementation of the Water Framework Directive. . . . . . . . . . . . . . . . . . . 183. ACtors iN thE lAkE ArEA iN DENmArk213.1 Involved actors and their tasks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.2 Overview of research, education and networking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234. sourCEs of fuNDiNg for rEstorAtioN ProJECts255. rEstorAtioN PlANNiNg AND imPlEmENtAtioN ProCEDurEs 276. NAtioNAl bEst PrACtiCEs AND sPECiAl ExPErtisE iN mEthoDs AND ProJECts316.1 National special expertise biomanipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316.2 New methods for lake restoration in Denmark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336.3 Lake Stubbe an example of a completed restoration project. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357. summAry AND NEEDs for DEvEloPmENt 43Background and types of restoration interventions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43rEfErENCEs47671. BACKGROUNDDuring the 20th century the anthropogenic nutrient input, mainly coming from agriculture and sewage, to most Danish lakes was much higher than the natural input. The result was that many lakes became so rich in nutrients that they shifted from a clearwater to a turbid state (fgure 1).To remedy this situation, comprehensive measures have been implemented during the past 20-30 years to reduce the nutrient input, one of the instruments being the national action plans on the aquatic environment. In many lakes these initiatives have led to reduced nu-trient concentrations; however, the majority of Danish lakes are still so nutrient-rich that they are maintained in a turbid state characterised by high phytoplankton growth (Sndergaard et al., 1998). In Denmark, there is a long tradition for monitoring the environmental state of lakes, and this monitoring or lake management is important when tracing the development pattern of Danish lakes. The poor water quality of most Danish lakes may often be due to increased nutrient input, but resilience after a nutrient loading reduction may be another impor-tant factor to consider. This resilience may be either chemical or biological (Sndergaard et al., 1999a,b). Chemical resilience implying continuously high lake water concentrations of phosphorus can be ascribed to release of phosphorus from a pool accumulated over the years in the lake sediment. Biological resilience implying continuously high phytoplankton biomass is often caused by dominance of the fsh stock by species preying on the zooplankton (Daphnia, etc.). This dimi-nishes the potential of zooplankton to graze down the phytoplankton and the turbid water state is therefore maintained.Figure 1.Illustration of the shift from a clearwater to a turbid state. The fgure furthermore shows the different structure of the ecosy-stem in a clearwater lake and a turbid (eutrophic) lake, respectively (Source: Aarhus County). 81. BackgroundVarious kinds of interventions into existing lakes also called lake restoration may be used to precipitate the process towards improved water quality and to disrupt the ecosystem resilience. For this purpose numerous methods have been developed and many lake resto-ration projects undertaken in Danish lakes over the past two decades. Thus, attempts have been made to disrupt the chemical resilience by either removing the large phosphorus pools of the sediment or by improving the sediments retention capacity. To break biological resilience fsh stock manipulations are the most fre-quently used method (Sndergaard et al., 1998).So far (i.e. before implementation of the structural reform), most lake management and lake restoration projects have been undertaken by the Danish counties in co-operation with the municipalities and interest or-ganisations. The research institutions NERI (the Natio-nal Environmental Research Institute) and DIFRES (the Danish Institute for Fisheries Research) have provided valuable advice and guidance. 1.1 The characteristics of lakes suffering from eutrophication in DenmarkDanish lakes have long been a threatened nature type. With time lakes become more shallow, overgrown or transformed into other types of nature such as bogs, wet meadows and forests. However, during the past centuries the largest threat has come from intensifed agricultural exploitation of the soil and urban expan-sion, implying drainage or eutrophication of lakes and ponds (Sand-Jensen, 2001) (box 1.1). Today, however, lakes are protected by Danish legislation (Chapter 2.2), lakes are re-established and there is an increasing awareness of the importance of allocating efforts to protect and preserve the remaining lakes (Sndergaard et al., 1999a). Box 1.1. Eutrophication Eutrophication is increased input of nutrients (phosphorus and nitrogen) to an aquatic ecosystem, leading to increased growth of algae (phytoplankton). Natural eutrophication is the process by which the character of lakes is gradually changed in consequence of natural shallowing, overgrowth or transformation into other lake types such as bogs, wet meadows or forests. Natural eutrophication takes place over a very long period of time, usually centuries. However, the various cultural activities of humans may accelerate the process, entailing the so-called anthropogenic eutrophication. In thousands of Danish lakes, anthropogenic eutrophication has led to increased input of nutrients that thus become available to the phytoplankton populations of the lakes. Enhanced phytoplankton growth adversely affects the animal and vegetation communities of the lakes and restricts their recreational use (see Chapter 1.2). Four trophic levels reflecting the degree of eutrophication are generally assumed (after Wetzel, 1983):trophic levels Oligotrophic Mesotrophic Eutrophic hypereutrophicDefnition Oligotrophic lakes are characterised by low nutrient concentrati-ons and therefore low phytoplankton abun-dance and clear water. Biological productivity is low and so are plant and fsh densities. Mesotrophic lakes are characterised by mode-rate nutrient concen-trations and moderate biological productivity. The water is relatively clear and plant and fsh densities are high. Eutrophic lakes are characterised by high nutrient concentrations, high biological produc-tivity, green water and high abundance or even absence of plants. Fish density is high. Hypereutrophic lakes are characterised by extremely high nutrient concentrations, turbid, green water and high biological productivity. Plants are either abun-dant or absent, and the densities of fsh and other small animals/in-vertebrates are high.Total phosphorus (g/l) 3 17.7 10.9 95.6 16 - 386 750 - 1200Total nitrogen (g/l) 307 - 1630 361 - 1387 393 - 6100 -Chlorophyll a (g/l) 0.3 4.5 3 - 11 3 - 78 100 - 150Secchi depth(m) 5.4 28.3 1.5 8.1 0.8 7 0.4 0.591. BackgroundToday, there are approximately 120,000 Danish lakes larger than 0.01 ha (100 m). However, most lakes are small or can be characterised as ponds. Only 2 %, cor-responding to 2,762 lakes, measure more than 1 ha, and only 6 lakes are larger than 1,000 ha. Denmarks largest lake is Lake Arres with an area of approx. 4000 ha. In total, Danish lakes cover an area of 58,000 ha, which corresponds to 1.4 % of the total Danish land area (Sndergaard et al., 1999b).Most Danish lakes are shallow. Half of them have an average depth below 1.6 m, 25% have an average depth >3 m, and only 3 % have an average depth exceeding 10 m. The deepest lake is Lake Fures with a depth of 38 m (Kristensen et al., 1990).About half the Danish lakes exhibit phosphorus con-centrations exceeding 150 g P/l, and in 65 % of the lakes summer Secchi depth is lower than 1 m (Jep-pesen & Sndergaard, 1997). Thus, Danish lakes are generally highly nutrient-rich (eutrophic) and turbid. In many lakes phosphorus is the most important limiting nutrient for phytoplankton growth, in other lakes phos-phorus and nitrogen are equally important or change in relative importance with the season (Sand-Jensen, 2001). If the phosphorus level in a Danish lake exceeds 150 g/l, Secchi depth will always be poor. Is it below 50 g/l the abundance of phytoplankton declines, and Secchi depth will be relatively high. At phosphorus concentrations between 50 and 150 g per litre, shal-low lakes may be either turbid or clear and may shift between the two states from year to year (fgure 1). Almost 40% of the Danish lakes belong to the latter category, which makes them suitable candidates for lake restoration initiatives aimed to promote the pro-cess towards improved water quality. In deep lakes, the phosphorus level must be somewhat lower to obtain an improvement of the Secchi depth (Sndergaard et al., 1999b).1.2 Development of the condition of lakesPast investigations and paleolimnological studies (i.e. investigations of plant and animal remains in the sedi-ment) show that most Danish lakes were clear 50-200 years ago (Amsinck et al., 2003; Jeppesen, 1998). However, during the 20th century, most lakes were he-avily impacted by anthropogenic eutrophication in the form of vast inputs of nutrients, mainly phosphorus and nitrogen. fewer and smallerzooplanktonincrease inplanktivorousfishincreasedsedimentationfewer submergedmacrophytesdecrease inpiscivorousfishincreasedP loadingturbid waterincreasedalgae biomassmore fisheating birdsfewerinvertebratesincreased oxygendemand, possiblyanoxic conditionsincreasedP releasepossibly obnoxioussmells & fauna deathdue to toxic algaereduced recreationalquality & possiblyrestricted bathingdue to toxic algaenegative effect onaquatic organismsFigure 1.2.1. Biological (green), physico-chemical (blue) and recreational (red) consequences of eutrophication. 101. BackgroundConsequences of eutrophicationPhytoplankton abundance increases dramatically in response to high nutrient concentrations (fgure 1.2.1). Phytoplankton blooms adversely affect the lake ecosy-stem in various ways: 1) the water becomes turbid and light penetration thereby decreases (impoverished Sec-chi depth), and submerged macrophytes are replaced by other species at the larger depths. This implies that the forage and refuge opportunities for many aquatic organisms disappear. 2) When the phytoplankton die and decompose a large oxygen demand is created, which negatively affects most aquatic organisms, inclu-ding fsh. 3) The risk increases of toxic algae blooming that may cause fauna depletion and impede the recrea-tional use of the lake.Increased nutrient loading also entails changes in the trophic structure of lakes, these being particularly pronounced at the top of the food chain. Eutrophication may thus cause a shift from dominance of piscivorous fsh such as perch (Perca fuviatilis) and pike (Esox lucius) to dominance of zooplanktivorous non-pre-datory fsh such as roach (Rutilus rutilus) and bream (Abramis brama). Moreover, the biomass of non-pre-datory fsh increases with increasing nutrient loading. Together, this results in enhanced predation pressure on the zooplankton that may then lose its control of the phytoplankton (Jeppesen, 1998). The result is an increase in phytoplankton biomass. The consequences are depicted in fgure 1.2.1 (and fgure 1). Reasons for eutrophicationUntreated or only partly treated sewage was the main source of phosphorus loading to lakes when deter-gents contained large quantities of phosphates. Today, sewage treatment is highly effective, and the main source of nutrient loading of the Danish lakes is the nutrient runoff from agricultural soils (Sand-Jensen, 2001). About 66 % of the phosphorus and 73 % of the nitrogen loading of lakes derive from open land, i.e. agricultivated felds (fgure 1.2.2). Since 1989 the nitrogen and phosphorus input to the Danish lakes has decreased, particularly to the most sewage-impacted sites (Lauridsen et al., 2005).

Figure 1.2.2. Sources of phosphorus and nitrogen loading to 20 intensively monitored Danish lakes in 2004 (Lauridsen et al., 2005).Focus on eutrophicationSewage pollution from urban areas was easily recogni-sable and effcient removal of both organic substances and phosphorus was initiated in the 1970s. The use of fertilizers and imported animal feedstuff, which incre-ased markedly from around 1960 to the mid-1980s, resulted in a dramatic increase in the nutrient loading of the aquatic environment. Political awareness of the problem increased, a contributory factor being several episodes of oxygen depletion and fsh kills in inner Da-nish waters during the 1980s. In autumn 1986, oxygen depletion caused death of lobsters in the Kattegat, PhosphorusWastewater3,9%Rainwater9,2%Open land65,8%Scattereddwellings14,2%Fish farming0,5%Atmosphere6,4%NitrogenScattereddwellings3,9%Rainwater1,5%Atmosphere18,9%Wastewater2,6%Open land73,1%Fish farming0,1%111. Backgroundwhich proved beyond doubt that conditions were poor. The effects of the oxygen depletion were covered in-tensively by the media, which led to a severe pressure on the Danish politicians. Focus was put on the aquatic environment, and the frst of three Action Plans on the Aquatic Environment was launched (Grant et al., 2002).The implementation of Aquatic Action Plan I in 1987 was the initiation of intensive treatment of urban and industrial sewage, and small-scale changes in the structure of agriculture were made with the purpose of obtaining an 80 % reduction of the phosphorus and a 50 % decrease in the nitrogen input to Danish aquatic areas. The reduction targets set by Action Plan I for industrial and municipal sewage works were all met. However, the objective set for reduction of nitrogen leaching from agricultural felds could not be fulflled, which led to the implementation of the Aquatic Action Plan II in 1998. In combination, Action Plan I and II led to the desired 50 % reduction of agricultural nitrogen leaching (Grant et al., 2004). In 2004, the govern-ment passed Aquatic Action Plan III, which is aimed to further reduce agricultural nitrogen leaching and bring down also the agricultural phosphorus leaching (Mini-stry of Environment & Ministry of Food, Agriculture and Fisheries, 2004). 1.3 History and current scope of lake ma-nagement and restoration in DenmarkLake managementIn Denmark, there is a relatively long tradition for monitoring lakes and other aquatic areas. This owes to the introduction of the Environmental Protection Act in 1974 that allocated to the Danish counties the responsibility for monitoring the environment, but only with the implementation of Action Plan I in 1987 was monitoring of the aquatic environment systematised. A national lake monitoring programme was launched to trace the effects of the measures introduced by Action Plan I to reduce the nutrient input. To cover the addi-tional costs incurred in complying with the supplemen-tary monitoring, the Danish Parliament has since 1988 annually allocated approx. 13 million to the counties, the amount being supplemented by funds for research and operation (Andersen et al., 2005). Since 1988, the national lake monitoring programme has been the joint responsibility of county and state authorities. The counties are responsible for sampling, preliminary data analysis and reporting at the local level, while the Na-tional Environmental Research Institute (NERI) collect and treat the county data for the purpose of national reporting (see Chapter 3). The present lake monitoring programme termed NO-VANA was implemented in 2004 under Aquatic Action Plan III and comprises intensive lakes of which most have been monitored since 1989 as well as extensive lakes (table 1.3.1.). The new NOVANA lake programme has a stronger biological focus, implying that more emphasis is now placed on natural elements and biodi-versity. The purpose of this is two-fold, i.e. i) to ensure compliance with the EU Water Framework Directive and EU Habitats Directive, and ii) to provide a detailed general status of the environmental state and develop-ment of Danish lakes. NOVANA will be in operation until 2009 when the programme will be revised (Lauridsen et al., 2005; Svendsen et al., 2005).Lake restorationLake restoration was frst put on the agenda in the mid-1970s when the Danish Environmental Protection Agency received a number of enquiries concerning the potential restoration of lakes with deteriorated env-ironmental quality. In spring 1977 the agency decided to set up a working group to elaborate a report on the potentials of lake restoration (Danish Environmental Protection Agency, 1979). However, lake restoration did not become a serious possibility until 1984 when Dr Erik Jeppesen was asked to form a lake group at the Freshwater Laboratory in Silkeborg (now the National Environmental Research Institute, NERI) (Jeppesen, 1998). The frst large-scale lake restoration project was completed during 1986-1988 in Lake Vng in Central Jutland (Jeppesen et al., 1989), and although lake restoration has thus been applied since the end of the 1980s, most projects have been undertaken during the past 10-12 years. The Danish restoration projects have produced widely varying results; however, there is no doubt that adequate restoration may signifcantly improve water quality. Thus, fsh stock intervention, the most popular method, has often had a positive effect on the re-maining trophic levels and overall water quality. Many Danish examples show that clearwater conditions may be created in shallow lakes if a substantial proportion (approx. 70-80%) of the planktivorous fsh stock is removed, preferably during a period of 1-2 years (Jep-pesen & Sammalkorpi, 2002). If the removal is insuf-fcient and/or external loading remains high, the effect may be limited, though. Preferably, external loading 121. BackgroundTable 1.3.1. The number of intensive and extensive lakes included in the NOVANA programme (2004-2009). The number of extensive lakes will be reduced during the period 2007-2009 when focus will be shifted to environmental hazardous substances. The table gives a survey of parameters, frequency (years) and number of samplings per year (according to Svendsen et al., 2005).Parameters Large lakes > 5 ha Small lakes (0.1-5 ha)Ponds(0.01-0.1 ha)intensive pro-gramme23 lakesExtensive pro-gramme I204 lakesExtensive pro-gramme II414 lakesExtensive pro-gramme III456 lakesPhysico- chemical parametersMass balance and nutrient sources X - - -Environmental hazardous sub-stancesX - - xHeavy metals X - - -Water chemical analyses 19 (every year) 7 (every 3rd year) 5 (every 6th year) 1 (every 6th year)Physical analyses (e.g. oxygen and temperature)19 (every year) 7 (every 3rd year) 5 (every 6th year) 1 (every 6th year)Sediment analyses 1 (every 6th year) - - -Loading and threats (GIS) - x x xBiological parametersPhytoplankton 19 (every year) 1 (every 3rd year) - -Zooplankton 19 (every year) 1 (every 3rd year) - -Submerged macrophytes 1 (every year) 1 (every 3rd year) 1 (every 6th year) 1 (every 6th year)Reeds 1 (every 6th year) - - -Bottom animals 1 (every year) 1 (every 3rd year) - -Fish 1 (every 6th year) 1 (every 6th year) - -Birds 1 (every year) - - -Amphibians 1 (every year) - - 1 (every year)should be reduced to a level corresponding to an equili-brium phosphorus concentration below 50-100 g P/l in shallow lakes and desirably 3 ha specific environmental objectives are set. Three categories exist: stringent (A), basic (B) and moderate (C). The desired environmental state is described using one or more quality objectives (e.g. Secchi depth and phosphorus level). Limits may also be given for the lakes upper tolerance level in terms of nutrient input should the objectives be met. The process of objectives establishment differs from county to county and the quality objectives below are those contained in the regional plan of the County of Northern Jutland. In 2004 the objectives were met in approx. 30% of lakes with specific objectives, a level that has remained largely unchanged during the past 20 years.lake objectives Quality measure: Lake water transparency measured as summer mean Secchi depth (m)A1 Site of specifc scientifc interestTransparency to the bottom or > 3 mA2 Bathing lake 2-3 mB Naturral and diverse animal and plant communities> 1-3 mC1 Sewage impacted lake > 05 mC2 Agriculturally impacted lake > 0.5 m2.2 Essential national legislationDanish legislation protects lakes in various ways. The Nature Protection Act and the Watercourse Act ensure the physical state of lakes, while the Environmental Protection Act primarily protects the water quality and thereby the ecological state of the lakes. The Planning Act prescribes that objectives are set for lake quality and use in the county regional plans. The fsh popula-tions in lakes are comprised by the Fisheries Act, whe-reas other animals and plants are indirectly protected through the Nature Protection Act and the Watercourse Act. Besides national legislation the guidelines of the EU Water Framework and Habitats Directives govern the rules for lake management established by the Env-ironmental Objectives Act. Below a more detailed description is given of the acts regulating Danish lakes and Table 2.2.1 provides a brief presentation of their main purposes. The Nature Protection Act covers all natural and artifcial lakes larger than 100 m and protects the lakes from all kinds of physical change of state, such as unregulated digging, weed clearance, lowering of 172. Administrative structure and legislation in the lake areathe water level, etc. The undertaking of such changes requires an exemption according to the acts section 3. Furthermore, according to the acts section 6, a 150 metre wide protection zone is established along lake shores within which erection of buildings, planting, etc are prohibited. To transplant water plants in connection to lake restoration projects, a permit must therefore be obtained, according to the acts section 16.The Watercourse Act protects lakes from lowering of their water level consequent to drainage, water abstraction or land reclamation, according to the acts section 18. The acts section 69 stipulates a two metre wide cultivation-free strip alongside the lakes. the Environmental Protection Act includes provi-sions to prevent and combat pollution of Danish lakes (section 1) and is administered by the Ministry of Environment. Section 27 of the act forbids the use of substances that may cause pollution and change the environmental state of a lake. Thus, for lake restora-tion projects involving addition of aluminium sulphate or iron for the purpose of binding phosphorus a permit must be obtained under the Environmental Protection Act. Section 27 also stipulates that animal manure must not be used on steep slopes when the waste pro-duct is likely to run off to watercourses and lakes in the event of heavy rainfall. This section is important when considering the extension of swine and cattle operati-ons. In addition, according to section 28 discharge of sewage to lakes requires a special permit. According to todays administrative structure, the act imposes on the counties to undertake lake monitoring activities, according to the acts section 66.The Fisheries Act regulates all aspects of fshery and farming in both salty and fresh waters, including lakes. To undertake fsh manipulation in lakes (fsh removal, stocking of piscivorous fsh, etc.) and other investigati-ons of scientifc, environmental and managerial nature, a permit must be obtained from the Danish Directorate of Fisheries (DDF), which is a part of the Ministry of Food, Agriculture and Fisheries. Thus, fshing tools and methods and deviations from prevailing preservation regulations (e.g. the acts section 63 and 109) must be approved by the DDF. Moreover, all fshing activities in connection with lake restoration projects must be presented to and permitted by land owners (cf. section 28). The Ministry of Food, Agriculture and Fisheries is the responsible authority. The Planning Act is the judicial background for the establishment of lake water quality objectives (section 6). Depending on the type of objective (box 2.1.1) the desired environmental state of a lake is described using one or more parameters, for instance the Secchi depth. the Environmental objectives Act facilitates the implementation of the Water Framework Directive and the Habitats Directive in Danish legislation. The act stipulates the set up of specifc objectives for the quality of Danish environment and nature and empowers the authorities to take the necessary measures to ensure that the environmental objectives are met. The overall objective is to adopt quality objectives ensuring a good ecological state of all aquatic ecosystems by 2015. For lakes good ecological state and good chemical state are required, which primarily implies good living conditions for plants and animals. The practical application of the legislation entails the elaboration of measures to ensure compliance with the objectives of the Water Framework Directive (website of Danish EPA: www.mst.dk).The responsibility of implementing the Water Fra-mework Directive lies with the Danish Ministry of Environment which has decided to combine its imple-mentation with parts of the Habitats and Bird Protec-tion Directives. The Water Framework Directives strict demands for protection of aquatic ecosystems contri-bute to the protection of biological diversity through the preservation of nature types, which is the primary goal of the Habitats Directive. Thus, the Habitats Direc-182. Administrative structure and legislation in the lake areative comprises several characteristic Danish lake types such as Lobelia lakes as well as lake-associated plant and animal species. Table 2.2.1. Signifcant acts regulating Danish lake management and lake restoration activities and their functions. The Danish wording of the Acts is found at the website of the Danish Forest and Nature Agency:www.skovognatur.dk/Lovgivning/Love/).signifcant acts regulating lake management activities FunctionThe Nature Protection Act Statutory order no. 884 of October 1, 2004Change of environmental stateLake protection zonesTransplantation of water plantsThe Watercourse Act Statutory order no. 632 of June 23, 2001, with later amendments Change of water levelDrainageCultivation-free stripsthe Environmental Protec-tion ActStatutory order no. 753 of August 25, 2001, with later amendmentsLake restoration via aluminium addition or similar measuresSurface runoff of animal manure to lakesSewage dischargeMonitoringThe Planning Act Statutory order no. 883 of August 18, 2004Establishment of lake objectivesthe Environmental objec-tives ActAct no. 1150 of December 17, 2003 Danish implementation of the EU Water Fra-mework, Habitats and Bird Protection DirectivesThe Fisheries Act Statutory order no. 828 of July 3, 2004Scientifc investigationsRemoval of non-predatory fshStocking of piscivorous fshFishery in generalPermission for lake restoration must be obtained from land owners 2.3 Current state of the national implemen-tation of the Water Framework Directive Present statusThe administrative framework of the Environmental Ob-jectives Act is the water districts. Before the structural reform there were 13 water districts whose boundaries generally followed those of the present counties. After the structural reform, which will become effective as from January 1 2007, the number of water districts will be reduced to 3, and the responsibility for these will be transferred to the regional environment centres. Before 2009 the counties/environment centres must draw up a water plan for each district to ensure cohesion of planning activities. By the end of 2006 at the latest, the general objectives of the Water Framework Direc-tive should be transformed into specifc environmental objectives for each individual water district.The frst step towards implementation of the Water Framework Directive was the conduct of Basis analysis, part I. This analysis was fnalised in December 2004 and comprised the establishment of a classifcation and typology of surface waters (including lakes) and groundwater and the completion of a survey of the im-pacts on aquatic ecosystems (the Danish Environmen-tal Protection Agency & the Danish Forest and Nature Agency, 2004). The next step is the conduct of Basis analysis, part II, which is to include characterisations of environmental state, preliminary objectives for the future state and a risk assessment of whether the aquatic ecosystems (in-cluding lakes) may fulfl the objective of good ecological state by 2015 (the Danish Environmental Protection Agency & the Danish Forest and Nature Agency, 2005). The guidelines for Basis analysis, part II were forwar-ded to the counties in October 2005 and the tasks involved must be completed during March 2006.The Danish Environmental Protection Agency has an-nounced that the future water and nature plans, which must comply with the stipulations of the Water Fra-mework and Habitats Directives, should be elaborated at the regional environment centres (O. Christiansen, Danish Environmental Protection Agency, personal communication). Also, the new municipalities will be 192. Administrative structure and legislation in the lake areagiven the responsibility of implementing the water plans (Danish Forest and Nature Agency & the Danish Environmental Protection Agency, 2005), including potential lake restoration projects. National challenges in connection with the im-plementation of the Water Framework DirectiveThe objectives of the Danish Action Plans on the Aqua-tic Environment are not based on legislation. However, with the implementation of the EU Water Framework Directive all member states are obliged to follow com-mon guidelines for preserving and improving aquatic ecosystems and to elaborate water plans. The so far three Danish Action Plans form a solid basis for this work (see Chapter 1) and the Water Framework Direc-tive has consequently been implemented in the most recent Action Plan III. To demonstrate the effects of Action Plan III, the lake monitoring programme NO-VANA was initiated in 2004, fulflling also the Directives requirement of control monitoring of aquatic areas (including lakes). One of the biggest challenges in connection with the implementation of the Water Framework Directive in Denmark has been the defnition of good and mode-rate in the categorisation of the environmental states of lakes according to the Directives fve ecological qua-lity classes: high, good, moderate, poor and bad (Sn-dergaard et al., 2003a). This defnition is crucial in the future implementation work as all aquatic ecosystems are to obtain good environmental state by 2015. The National Environmental Research Institute was asked to provide a scientifc evaluation and their suggestion for a total phosphorus-based classifcation was a boundary of 25-50 g P L-1 for good state and a boundary of 50-100 g P L-1 for moderate state in shallow lakes, the corresponding boundaries being 12.5-25 and 25-50 in deep lakes. However, this limit was not acceptable for political reasons and was met with strong objections from Danish agricultural organisations. The current position of the Danish Environmental Protection Agency and the Danish Forest and Nature Agency is that the demand of good ecological quality should be based on the quality objectives established by the regional plans (the Danish Environmental Pro-tection Agency & the Danish Forest and Nature Agency, 2005). Thus, the risk assessment should consider whether there is a risk that a lake, classifed for in-stance as B (see box 2.1.1), will not meet the objectives set by the regional plan in force in 2015. However, as the criteria for objective fulflment vary widely between the counties, this position is problematic. Another factor giving rise to criticism is the less strin-gent objectives of the regional plans for lakes impacted by sewage and agricultural waste. As less stringent objectives are a phenomenon unknown to the Water Framework Directive, it is questionable whether nutri-ent-impacted lakes with such objectives will be able to attain good ecological status by 2015. So far, until the EU agrees on the boundaries between the ecological quality classes, which will expectedly be based on the chlorophyll concentration or other simple and frequently used environmental variables, the Danish boundary between good and moderate will be based on the environmental objectives stipulated in the county regional plans (M. Sndergaard NERI, personal communication).202. Administrative structure and legislation in the lake area213. ACTORS IN THE LAKE AREA IN DENMARK3.1 Involved actors and their tasksThis chapter describes the different involved parties and their respective roles and cooperation in relation to planning and implementation of lake management and lake restoration in Denmark until the structural reform of Danish municipal and country structure comes into force by January 1 2007 (table 3.1.1). In addition, this chapter outlines the expected division of roles between the local municipal level and the regional level after January 1 2007 (table 3.1.2).Key players Responsibilitieslocal level 271 municipalities Monitoring of swimming areas and waste water upstream to lakesMaintenance and sign postingParticipation in restoration projectsregional level 13 counties National and regional monitoring, data collection, quality control of data, setting of objectives, reportingNature and environmental consideration in relation to the publicRestorations, water plans, according to the Water Framework Direc-tiveNational levelNational Environmental Re-search Institute (NERI)ResearchResponsible for the national monitoring program, technical advisory services, storing data RestorationsCommunication/educationAdvising politicians, administrators and agenciesDanish Institute for Fisheries Research (DIFRES)ResearchRestorationsCommunication/educationUniversitiesResearchEducationDanish Environmental Protec-tion Agency (DEPA),Danish Forest and Nature Agency (DFNA)Responsible for the implementation and handling of EUdirectives Responsible for setting environmental objectives, the action taken and the economy, all based on the basis analysisAdvising politicians and administratorsCommunication/educationConsultancy levelPrivate expert consultancy companies/advisory servicesAll consultant work: restorations, investigations, monitoring advise, research, modeling, reportsvoluntary levelSport fshing associationsPromoters of environmental improvement and possible participationPointing out environmental problemsPublic awareness raisingSpokesmen for the public and/or specifc interest groups Responsible of restoration projects supported technically and acade-mically by e.g. the countyForestry associationsHouseowners associationsRecidents associationsRecreational usersScouts associationsDanish Society for Nature Con-servationLandownersEnvironmental NGOsInternational levelEU FundingEU regulations and directives dealing with the environmentTable 3.1.1. Before the structural reform. Players in lake management and lake restoration in Denmark and their roles.223. Actors in the lake area in DenmarkToday, the 13 Danish counties are the implementing authorities responsible for handling and approving restoration projects in accordance with existing natio-nal and European legislation. Restoration projects are in most cases initiated because the lake in question does not meet the environmental objectives set in the so-called Regional plan of the county. The county then prepares the necessary action plans for the restora-tion based on existing knowledge and supplementary investigations of the specifc lake, if necessary. Further-more, the county is responsible for rising funding for restoration projects and for issuing necessary permis-sions and exemptions from the Danish law if needed (see Chapter 5).In some cases however, the initiator has been one of the local key players, e.g. a volunteer association and/or the municipality, who has pointed out an env-ironmental problem and hence, developed the project idea. Often, there is co-operation between the county and the municipality on a case-by-case basis, where the municipality mainly contributes with manpower and the county with the overall responsibility including the planning and funding. The volunteers involved in a restoration project are typically the landowners, scouts associations, environmental NGOs or other in-terest groups, who contact the municipality or county, because they wish to improve the condition of their specifc lake. In these cases, local people often contri-bute with important knowledge of the fora and fauna and the history of the lake, which in turn helps the county to gain more insight in and background know-ledge of the condition of the lake. Volunteers also often take part in for instance fsh removal (biomanipula-tion), monitoring of different feld equipment, checking nets, measuring Secchi depth, recording water levels, counting of birds, recordings of recapture of stocked fsh etc.Furthermore, there is a long tradition for counties and municipalities of using private consultancy companies in possession of relevant expertise to carry out many of the different aspects of lake restoration and lake management projects. The consultancy companies Key players Responsibilitieslocal level 98 municipalities Same as before the structural reform plus:Comments/suggestions to the governmental plansImplementing the actions plans, according to the Water Fra-mework DirectiveRestorationsAll administration of nature- and environmental considerationsregional level7 governmental environment centers (replaces the coun-ties)Same as before structural reform plus:Advising politicians and administratorsAdvising the municipalities in relation to for example action plans and restorationsNote! Lake restoration and consideration in relation to the public are transferred to the municipalities5 regions Play no role in connection to lakesNational levelNational Environmental Pro-tection Institute (NERI)Same as before the structural reform plus:Responsible for the regional monitoring program (before underta-ken by the counties)Responsible for a common databaseDanish Institute for Fisheries Research (DIFRES),Universities,Danish Environmental Protec-tion Agency (DEPA),Danish Forest and Nature Agency (DFNA)Same as before the structural reformPrivate levelPrivate expert consultancy companies/advisory servicesSame as before the structural reformvoluntary levelSee table 3.1.1 Same as before the structural reforminternational level EU Same as before the structural reformTable 3.1.2. After the structural reform. Players in lake management and lake restoration in Denmark and their roles. The roles are quali-fed guesses, as the structural reform has not yet been implemented.233. Actors in the lake area in Denmarkthen co-operate closely with the county in both pre-paring and implementing the action plan for the given lake restoration project. Especially in connection to the implementation phase of a project, the co-operation on a case-by-case basis between the expert consultancy company, county, municipality and volunteers is an im-portant driving force when it comes to lake restoration projects carried out in Denmark. Continuation of similar co-operation models is still expected to take place also after the structural reform, although the co-operation between municipalities and governmental environment centres will be considerably closer.In Denmark, there is also a long and strong tradition for co-operation and exchange of experiences between the counties, as the main players in lake restoration, and the research centres (NERI - National Environmen-tal Research Institute & DIFRES - Danish Institute for Fisheries Research and the Danish universities).3.2 Overview of research, education and networkingResearch and educational institutions NERI is a research institution under the Danish En-vironmental Protection Agency, while DIFRES is a research institution under the Danish Ministry of Food, Agriculture and Fisheries. Both institutions carry out research within lake restoration and lake ecology, and the results from this research are published in scientifc journals and reports, or through training courses, via network and advisory services.There are fve universities in Denmark where biology and environmental science are offered. The Master and Ph.D. students often do their thesis in co-operation with the research institutions and the practical work is on few occasions carried out in contact with a county or municipality. Furthermore, the universities and the research institutions often engage foreign students.Maintenance of knowledge and networkingWorking groups are often formed comprising the rele-vant actors within the various aspects of lake manage-ment and restoration to secure a participatory planning process and an exchange of know-how and ideas for new initiatives, methods etc. One example is a group of representatives from NERI, DFNA (Danish Forest and Nature Agency), GEUS (Geological Survey of Denmark and Greenland) and the counties. This group was established to discuss the implementation of the Water Framework Directive in relation to the Danish lakes and how to improve existing Danish monitoring programme for water bodies. The result was a report, which forms the scientifc basis for the implementation of the Water Framework Directive (Sndergaard et al., 2003c). Another example is a group of representatives from NERI, DIFRES, consultancy companies and the coun-ties, which was formed in 1997 with the purpose of collecting all experiences and knowledge achieved from lake restoration projects in Denmark. The fnal report describes many different restoration projects with eva-luations and recommendations for the different met-hods of restoration (Sndergaard et al., 1998).In November 2005, a group of representatives from the counties and NERI took the initiative in gathering the latest knowledge and experiences on restora-tion projects. The report will summarize and give a cross-analysis of the long- and short-term effects of implemented restoration projects together with an evaluation of the methods applied. Furthermore, it is the intention to give a general view of lake restoration projects as well as recommendations for the use of the future work of the municipalities in regard to the imple-mentation of the water plans to meet the requirements of the Water Framework Directive (H. Skovgaard, personal communication). The report is expected ready before the end of 2006.Once every year NERI has a national conference were the counties, the Danish Environmental Protection Agency and the Danish Forest and Nature Agency are in-vited to discuss the current lake monitoring programme and to present the latest research within this feld.In addition, a seminar is arranged by the counties association MINA (the former DAVID) once or twice a year. Here planned as well as completed restoration projects is presented and discussed. To these semi-nars other relevant parties are invited depending on the specifc topic (for example NERI, DIFRES and the consultancy companies).There are continuously workshops on different lake aspects going on in Denmark. One of the latest initia-tives is a network forum where people working with lakes and streams (universities, research institutions, counties, consultancies etc.) are invited to a Freshwa-ter Symposium. The frst symposium will be held in January 2006.243. Actors in the lake area in DenmarkFurthermore, in relation to a comprehensive restora-tion project in Lake Fure, a workshop for exchanging experience from lake restoration in general in Denmark has been planned. The County of Frederiksborg, in co-operation with the Municipality of Farum, is responsible for the restoration project, which is partly fnanced by the EU Life-programme (see Chapter 4). The workshop will be held in May 2006.Internationally, Denmark also co-operates on lake issues with other European countries/partners, for example on two different projects, Lakepromo and Eurolimpacs. This report is a part of the frst mentioned (see the preface). The purpose of Eurolimpacs is to give a general overview of restoration projects in Northern Europe, including short- and long-term effects and pos-sible climatic causes of successes and failures.Research and educational institutions LinksUniversitiesAalborg UniversityUniversity of AarhusUniversity of Southern DenmarkUniversity of Copenhagen Ros-kilde Universityhttp://www.aau.dkhttp://www.au.dkhttp://www.sdu.dkhttp://www.ku.dkhttp://www.ruc.dkResearch institutesDIFRESNERIhttp://www.dfu.min.dkhttp://www.dmu.dkConsultancy companiesBio/consultCarl BroHedeselskabetFiskekologisk LaboratoriumRambllDHICowiNirashttp://www.bioconsult.dkhttp://www.carlbro.comhttp://www.hedeselskabet.dkhttp://www.foel.dk (in preparation)http://www.ramboll.dkhttp://www.dhi.dkhttp://www.cowi.dkhttp://www.niras.dkNational and international collaborations WorkshopsFreshwater SymposiumProject Lake Furehttp://www.ferskvandsbiologi.dkhttp://www.kbhamt.dkNational conferencesMINA (former DAVID)Conference of NERIhttp://www.davi.dkhttp://www.dmu.dkInternational projectsLakepromoEurolimpacshttp://webd.savonia-amk.f/projektit/markkinointi/lakepromo/uk/index_uk.htmlhttp://www.eurolimpacs.ucl.ac.ukTable 3.2.1. Overview of the research and educational institutions in Denmark as well as international co-operations in 2005. Most links refer to Danish web pages - some are, however, also in English. 254. SOURCES OF FUNDING FOR RESTORATION PROJECTSMost frequently, lake restoration projects are fnanced by municipalities, counties or governmental institutions either alone or in combination occasionally supple-mented by EU means. In a few instances land owners or interest groups may provide fnancial support or funding from foundations or other sources may be ob-tained. However, most restoration projects are funded by the counties that also function as project managers. Resources in the form of man-hours from municipality, government and particularly county authorities often constitute a large part of the total costs of lake resto-ration.Nature management fundsLake restoration projects may obtain funding from the state nature management funds. Since 1989, the Danish Parliament has each year allocated additional funds (approx. 9.2 mill ) for nature management pur-poses to the state and to the counties as block grants. The nature management funds are used to: restore nature areas to improve the living conditi-ons for wild animals and plants, increase the areas of state forests as a contribution to the aim of doubling Denmarks forested area, promote the outdoor life of the Danish population, maintain and preserve landscape and culture-histo-rical values. By means of the nature management funds many lakes, moors and commons have been established and new city-near forests created all around the country to the beneft of the Danish population. The Danish Forest and Nature Agency (DFNA) administers the grants programme and distributes the annual means among the various projects. Applications may be forwarded for large-scale projects, i.e. projects amounting to more than 130,000 . The application should con-tain information on background, purpose, preliminary investigations, co-operative partners, national inte-rest and a specifed budget. Most major projects are undertaken by the state forest districts, but also many counties apply for nature management grants. Thus, for lake restoration purposes a county may typically apply for 13,000-27,000 annually for a sequence of years. These funds will cover the necessary costs of consultancy assistance required in connection with, for instance, fsh manipulation initiatives (cf. Chapter 6.3). Grants may also be obtained for small-scale projects at individual dwellings for the purpose of watercourse restoration, ochre removal and establishment of small-scale aquatic ecosystems. (Information is available at: http://www.skovognatur.dk/Emne/Naturbeskyttelse/Natur-pleje/Naturforvaltningsmidler/ (in Danish)).Net and Rod Fishing license fundsThe counties and various organisations - may also apply to the Danish Directorate of Fisheries for the stocking of pike fry. For several years the so-called fshing license funds have been used to pay for the stocking of pike in lakes with no or only few piscivores or in connection with major restoration projects. The Danish Institute for Fisheries Research approves the applications and sets the number of pike to be stocked. Typically, the applications involve pike fry to a value of 130-13,000 , depending on the lake size. On an annual basis, approx. 270,000 of the fshing licence funds are spent at fsh stocking in lakes, of these ca. 110,000 are used in biomanipulation projects involving pike fry stocking (Berg & Jacobsen, 2003).Foundation meansThe largest and most well-known Danish foundation is Aage V. Jensens Fonde, which comprises two separate foundations, the Danish Aage V. Jensens Fond estab-lished in 1977 and the international Aage V. Jensen Charity Foundation established in 1980. The avowed objectives of the Foundations are to contribute to con-serving nature and protecting wildlife. While the Danish Foundation sponsors primarily projects in Denmark and Greenland, the international and somewhat larger foundation domiciled in Liechtenstein operates on the international level with nature conservation and wildlife protection. The income from the capital of the Founda-tions is used to sponsor many different nature projects, including research projects and educational work, and the acquisition and management of nature areas. The Foundations own a number of nature areas in Denmark, including the Vejlerne nature reserve, Lille Vildmose and ble. In principle, all may apply for fnancial support from Aage V. Jensens Foundations. By way of example, the Danish Society for Nature Conservation, Danish Birdlife and Danish Society for Animal Protection have received funding for the projects Endangered and rare breeding birds and Save the stork and for the publication of books, posters, folders, etc. Also the National Environ-mental Research Institute was awarded funds for the 264. Sources of funding for restoration projectsprojects Forestry and biodiversity and Investigations in the Vejlerne, the latter involving also the counties of Viborg and Northern Jutland, which are jointly respon-sible for the monitoring of Vejlerne. The Zoological Museum of the University of Copenhagen was awarded funds for the building of an annex to the museum and for numerous other projects such as Danish Bird Mi-gration Atlas and Danish Mammal Atlas authored in cooperation with the Natural History Museum of Aarhus University.(Website of Aage V. Jensens Fonde: http://www.avjf.dk).EU-funds: the LIFE and INTERREG programmesLIFE cofnances environmental initiatives in the Euro-pean Union. LIFE contributes to the implementation, development and enhancement of the Community environmental policy and legislation, the integration of the environment into other EU policies and promotes sustainable development. The LIFE-programme has three components: LIFE-Nature - supports projects designed to im-plement the Birds and Habitats directives, and in particular the implementation of the European Uni-ons Natura 2000 Network that aims to manage and conserve natural habitats and the wild fauna and fora and nature types of European Union interest. LIFE-Environment supports the demonstration and development of innovative and integrated techniques and methods for the protection and enhancement of the environment. LIFE-Third countries supports the development of environmental management capacities in third countries with a coastline bordering the Mediter-ranean or the Baltic, excepting the Central and Eastern European countries that have signed as-sociation agreements with the EU.Companies, institutions, organisations and individuals residing in an EU member country are eligible to apply for LIFE funding. In Denmark, the Danish Forest and Nature Agency is responsible for the management of the Danish LIFE projects. Several Danish projects have received LIFE support: the Skjern River Resto-ration project, the Wetland Restoration Project in Vest Stadil, Fjord, the Restoration of Dune Habitats along the Danish West Coast, the Image project in the coa-stal lagoon Tryggelev Nor (County of Funen) and the Restoration of Lake Fures (Frederiksborg County). (Additional information can be found at: http://www.skovognatur.dk/Emne/Naturbeskyttelse/Naturpleje/LIFE/. (in Danish); http://europa.eu.int/comm/environment/life/home.htm (in English)).The EU INTERREG programmes provide support to transnational cooperation projects that seek to improve territorial development and cohesion in the EU region. The INTERREG-programmes have existed since 1990 and are part of the European structural funds and fnanced by the European Regional Development Fund (ERDF). Regarding nature and environment, support may be obtained for transnational cooperation projects and the establishment of networks and other fora that promote sustainable development, protect nature and improve the regional environment.To obtain funding, the projects must be additional, implying that the funding cannot be used for activities imposed by law or activities that the project partners would have undertaken anyway. Eligible applicants for INTERREG III support projects are public institutions (state, counties, municipalities) or other operators un-dertaking public projects. LAKEPROMO is partly fnanced by EU-funds via a 50 % grant from the INTERREG IIIC North programme to the LAKEPROMO project whose estimated total budget amounts to 1,470,000 distributed between 11 part-ners from 7 countries. The total budget of the County of Northern Jutland amounts to 150.000 of which 50 % is fnanced by EU. (Additional information can be found at: http://www.nja.dk/Serviceomraader/NaturOg-Miljoe/Soeer/LAKEPROMO.htm (in Danish); http://webd.savonia-amk.f/projektit/markkinointi/lakepromo/uk/index_uk.html (in English)).275. RESTORATION PLANNING AND IMPLEMENTATION PROCEDURES As mentioned in section 1.4 various biological and physico-chemical methods of lake restoration exist, the most popular being those involving fsh manipulation. However, a joint characteristic of all types of restora-tion is the preliminary and planning work required to ensure that the project is successful and the expected effects are obtained. Figure 5 depicts the fve phases of restoration actions, involving 1) desire and initiative to improve the environmental state, 2) preliminary investigations, 3) planning, 4) implementation and 5) estimation of effects and monitoring. The fgure focu-ses in particular on biomanipulation that normally invol-ves both removal of non-predatory fsh and stocking of predatory fsh. The tool of fsh stock intervention is described in detail in chapter 6, which also provides a real-life example of such a fve-step restoration project. The duration of a restoration project may vary from six months to several years, depending particu-larly on lake size and potential problems concerning accept from land owners, fnancing, etc. to do something to improve the state of their local lake may also induce local citizens, land owners and organisations to raise an initiative. Finally, the initiative may come from the municipality. No matter who takes the initiative, the counties, which are the implementing authority within the area of lake restoration, will act as project coordinator and manager during the restoration process. Phase 2. Preliminary investigations and poten-tial reduction of external phosphorus loading Well-planned and thorough preliminary investigati-ons are a prerequisite for successful restoration. In this connection knowledge is required on the phos-phorus dynamics of the lake, the composition of the fsh stock, the internal phosphorus loading from the lake sediment, submerged macrophyte coverage, the phytoplankton composition, etc. When the lake has an inlet and an outlet and/or other types of infow (drains, wastewater, rain water, etc.), information on the size of external catchment loading is essential too. Most often, several of these parameters are known already, imply-ing that only supplementary investigations are needed. To obtain permanent effects of biomanipulation in shal-low lakes, the external phosphorus input must be lowe-dialogue fundingpermissions,exemptionsmonitoringeffectassessmentactionplansimplementationinitiativecounty municipality citizens associations landownersexternalP reductionprestudiesphase 1phase 4course of restorationphase 5phase 2phase 3phase 3Figure 5. Illustrates the course of restoration from the iniative to the subsequent effect assessment and monitoringPhase 1. InitiativeMost frequently, the Danish counties take the initia-tive to undertake biomanipulation in a lake as their monitoring activities have supplied them with detailed knowledge of the lakes environmental state. The desire 285. Restoration planning and implementation proceduresred to a level corresponding to a lake water phosphorus concentration of approx. 50-100 g P/l. If the external loading remains high during the restoration process, the effect will most probably be limited. An additional prerequisite is, of course, that the fsh stock is unba-lanced with dominance of non-predatory fsh and low abundance of piscivorous fsh. When these conditions are fulflled or may be fulflled by introducing phospho-rus-reducing activities in the catchment, the prerequi-site for obtaining successful restoration in the present phase of restoration is met. Phase 3. PlanningThis phase tends to be the most time-consuming aspect of the lake restoration process. In fact, many restoration projects never go beyond this planning stage. It may appear, for instance, that funding or permissions were more diffcult to obtain than anticipa-ted. Resistance from land owners is another issue and objections may be raised by societies and organisati-ons. Generally, the need for dialogue increases with the number of private individuals and/or interest organisa-tions involved. Usually agreement between all parties is given high priority; however, if this is not possible land owner objections must be accepted and fshing in his/her part of the lake must be avoided (an example being Lake Stubbe, cf. Chapter 6, section 6.3). Chapter 2, section 2.2, describes the exemptions and permits needed with regard to the actual undertaking of lake restoration, and Chapter 4 treats the funding of restoration projects. It should be added, however, that stocking of piscivores requires approval from The Danish Veterinary and Food Administration, as stocking implies a risk of transfer of infectious fsh diseases.Mass removal of planktivorous fsh by electrofshing as part of a restoration project in Lake Poulstrup in 2003. The lake is situated in the conservation area Dall Heath and is a popular recreational area. Photo: County of North Jutland.295. Restoration planning and implementation proceduresThe planning phase should include the following aspects: selection of fshing tools and methods depending on time of year, fsh species present and lake size, depth and bottom structure, etc. establishment of a quantitative measure for the extent of the fsh removal. Minimum 70-80% of the non-predatory fsh stock must be removed during a short time interval to obtain an adequate ef-fect (Jeppesen & Sammalkorpi, 2002). Insuffcient removal is often the reason for a negative outcome of restoration projects. timing of fry stocking with water temperatures and thus the hatching of non-predatory fry to ensure the frys food supply. prevention of immigration of fsh from non-bioma-nipulated sites, for instance via watercourses and drains. planning of logistics, as several tonnes of fsh are to be removed, disposed of or exploited in biogas plants or as animal feed. When the various permits and approvals have been ob-tained, funding has been secured and agreement exists between all project partners on the project content, the county (or the consultancy company) may elabo-rate a detailed project plan. The plan should contain a detailed description of the timing of project activities, how they will be performed and by whom as well as a description of the project background and its expected outcome. Phase 4. ImplementationCorrectly done, fsh removal is fast and intensive (ma-ximum 1-2 years), whereas the stocking of predators may endure for several years. During the removal pro-cess, progress will be discussed and possible adjust-ments of tools and methods may be made to ensure optimum effciency. Usually, the actual fsh removal will be conducted by the county and/or private consultancy compa-nies, these often being assisted by the municipalities and/or local citizens and organisations; fsh removal is a large-scale, time-consuming task and all efforts are appreciated. Furthermore, participation by local citizens ensures their feeling of joint responsibility. The counties may call for tenders on the project from con-sultancy frms. The stocking of pike fry lasts one day, depending on lake size. It is undertaken in May, usually by the counties. Mass removal of planktivorous fsh by dragnet in Lake Poulstrup in 2003. The catch consisted mainly of crucian. Photo: County of North Jutland.305. Restoration planning and implementation proceduresPhase 5. Effect assessment and monitoring When the restoration projects ends, the effects are estimated. The most important tools in this connec-tion are fsh investigations to be undertaken both before and after removal, analysis of water samples for physico-chemical parameters to determine lake water nutrient concentrations, measurement of Secchi depth and investigations of the abundance and composition of phyto- and zooplankton.The frst criterion of success is enhanced water trans-parency as an immediate response to reduced non-predatory fsh abundance, implying improved growth conditions for the large-sized zooplankton preying on the phytoplankton. This criterion is often met straight away, even in less successful restorations, but fre-quently the positive effect does not last. Other success criteria are the establishment of a healthy population of predatory fsh, a zooplankton community composed of large-sized species, for instance Daphnia, reduction of phosphorus concentrations, increased density of submerged macrophytes, etc.But when is a restoration project a success? How signi-fcant must the effects be and for how long should they endure? How do you distinguish between the effects of simultaneous interventions such as reduction of loading, fsh removal and pike stocking? What can you learn from unsuccessful restorations? If repetition is necessary, is it then restoration or maintenance of the desired state? In conclusion, many questions remain unanswered and many problems need to be addressed, but the experi-ences gained from evaluations of ongoing projects will help tackle these important issues. Thus, prolonged monitoring of restored lakes is crucial for the evalua-tion of the long-term effects of biomanipulation.Monitoring of the environmental state of Lake Poulstrup after ending the restoration project of fsh manipulation in the lake. Photo: County of North Jutland..316. NATIONAL BEST PRACTICES AND SPECIAL EXPERTISE IN METHODS AND PROJECTS6.1 National special expertise biomanipu-lationDenmark has many years of experience in lake resto-ration by biomanipulation i.e. removal of planktivorous fsh (particularly roach and bream), which in most cases is done in combination with stocking of pisci-vorous fsh (mainly pike). Removal of planktivorous fsh has shown to be a very effective method to actively shift lakes from a turbid to a clearwater state. This chapter describes removal of planktivorous fsh and stocking of piscivorous fsh as methods for lake restoration. Chapter 1.4 describes less frequently used restoration methods.Removal of planktivorous fish Removal of planktivorous fsh (particularly roach and bream) has the goal of increasing the water quality of the lake. Prior to restoration, an assessment of the speci-fc lake in relation to the fsh stock must be made. The investigation evaluates the composition and biomass of the fsh species, and set the level of mass removal. Mass removal of planktivorous fsh is a relevant method, if the biomass of planktivores constitute more than 80 % of the total fsh biomass. It is well-known that the annual concentration of phosphorus at equilibrium in shallow lakes must be lower than 50-100 g P/l (in deep lakes lower than 20-50 g P/l) to obtain more enduring effects (Sndergaard et al., 1998, 2000; Jeppesen et al., 1990). Another important factor is to ensure removal of at least 70-80 % of the planktivorous fsh stock within 1-2 years or to the point where the fsh stock is reduced to less than 100 kg ha-1. It is crucial for a successful and enduring result that the intensive fshing is followed by supplementary fsh removal in the subsequent years until the piscivorous fsh stock has been strengthen in order to control the biomass of planktivorous fsh (Sn-dergaard et al., 1998, 2000). If the stock of planktivorous fsh is not suffciently reduced during the frst couple of years, the biomass of planktivores is likely to increase, whereby the effect of mass removal may be lost.MethodsMass removal of planktivorous fsh can be done using dragnet or trawl (from boad or bank), gillnets, pound nets, traps and/or electrofshing. The composition and distribution of the planktivorous fsh stock together with the bottom condition and morphometry of the lake will determine when to initiate the removal of planktivores and which method to use (Sndergaard et al., 1998). The choice of method ought to be based on the catch effectiveness in relation to time and energy spent. Thus, during winter when fsh are inactive, ac-tive tools like dragnets or trawls are preferred, whe-reas passive tools like gillnets, pound nets, traps and electrofshing are preferred during spring and summer, when fsh are active.During summer, pelagial trawling in deep lakes is a va-luable supplement to gillnets and pound nets, because fsh will concentrate in the oxygen rich waters above the thermocline. In addition, shoals of particularly large bream can be located with echo sounders and, thereby, caught with high level of effciency.In medium deep (2-4 meters), smaller sized (10-400 hectare) and shallow lakes (< 3 meters) dragnet is a valuable and effective tool due to the fact that dragnets are designed to be used with single pulls in relatively large areas. The dragnets have to be adjusted to the physical conditions in the lake and the fsh stock. Ef-fective use of dragnets demands a lake bottom without submerged obstacles.If the lake has a complex morphometry or many submerged obstacles, the use of pound nets is prefer-red. The pound nets are placed near the banks of the lake or, in lakes with complex morphometry, on sub-merged tongues or reefs, which are spawning ground for bream. The use of pound nets is optimal in spring when planktivorous fsh are swimming towards their spawning ground. Gillnets (mesh size: 60-90 mm) have proofed successful in catching bream during their spawning period in May/June but as these nets demand great effort in checking and cleaning, gillnets are not considered a preferable tool outside the spawning sea-son or to use for smaller species of planktivores.Electrofshing is another effective method in defned areas where fsh crowd. By closing off the area with fne nets, the effectiveness of fsh removal using elec-trofshing is increased signifcantly. 326. National best practices and special expertise in methods and projectsResultsRemoval of planktivorous fsh, particularly roach and bream, will in the short-term strengthen the zooplank-ton community, especially large cladoceran species as Daphnia. The increase in zooplankton biomass will ena-ble zooplankton to control phytoplankton and thereby improve the transparency of the water. Furthermore, removal of bream may reduce the resuspension of the sediment and the internal nutrient loading, which will contribute to the improvement of the water quality. The purpose is to promote the re-establishment and development of submerged macrophytes, as clear water is of vital importance to their existence. In many lakes, an increased distribution of submerged macrop-hytes has been observed within 1-2 years after mass removal. In many situations, however, there has been a resilience towards a shift to the clearwater state. Stocking of pike fryThe mass removal of planktivorous fsh will leave behind a large amount of small planktivorous fsh as well as planktivorous fsh fry as they often escape the nets. The enhanced recruitment of planktivores, increased fecun-dity of the remaining adults and high survival and density of the planktivorous fry themselves are central problems of mass removal of planktivores (Jeppesen & Sammal-korpi, 2002). Release of pike fry (0+, 20-50 mm) in large densities (>0.1 individual/m2) has been used to control small individuals of planktivores in the short-term and to strengthen the piscivorous fsh stock in the long-term.MethodOnly a few fsh farms produce pike fry for stocking. However, it can be done with a fairly good survival rate and at a reasonable cost (approx. 0.13 per individual). The 0+ pikes are transported to their destination in well aerated water containers. The stocking is done from boat using small jugs and are spread carefully along the edge of the reed to avoid stress and cannibalism. The stocking of pike fry must be ended before the native pike fry become bigger than the stocked ones to avoid further cannibalism. Likewise, stocking must coincide with the hatching of the planktivorous fsh fry as these are the primary food source for the pike fry. Today in Denmark, it is recommended to stock before May 25.The result of the mass removal of planktivorous fsh in Lake Klok-keholm Mlle in 2003. Photo: County of North Jutland.Stocking of pike fry in Lake Poulstrup in May. A total of 1,000 pike fry were stocked in the lake (size: 0.6 hectares) in 2003, 2004 and 2005, respectively. Photo: County of North Jutland.336. National best practices and special expertise in methods and projectsResultsStocking of pike fry has been used in many Danish lakes (Berg et al., 1997; Sndergaard et al., 1997; Skov et al., 2003a,b) but the stocking densities and methods (time etc.) have differed widely, making it diffcult to estimate whether effects are completely absent or, if negligible, relate to the scale of intervention. Experi-ences are therefore mixed, but the most recent col-lection of data on pike stocking experiments indicates that the effect is overall poor (C. Skov, DIFRES, per-sonal communication). At best, stocking only affects the water quality the frst year, possible reasons being high mortality caused by cannibalism, the size of the 0+ pikes, time of stocking, risk of predation from perch and birds, lack of hiding places and other stressful physical factors. Also the frys choice of food items can constitute a problem, as fry do not commence to prey until they reach a length of 100-120 mm (Grnkjr et al., 2004, http://www.fskepleje.dk/, Skov et al., 2002, Skov et al., 2003). The effect on the structure of the lake ecosystem is likely to increase if stocking of 0+ pike is continued until a healthy piscivorous fsh stock is achieved together with more stable clearwater condi-tions with increased coverage of submerged macrophy-tes (Sndergaard et al., 2000). 6.2 New methods for lake restoration in DenmarkDuring recent years, new methods for lake restoration have been tried out in Denmark. These experiments have been based upon a scientifc and political desire to develop other suitable and less expensive restoration methods. This section describes these new methods and their effects.Pines and plastic plantsIn combination with stocking projects, conifers have been placed in lakes to provide hiding places for the pike fry and, thereby, enhance their survival in lakes where natural hiding places are limited. In other pro-jects, plastic plants have been used instead. A method of placing conifers upside down, has recently been used with great success as part of a large restoration project in the Inner Lakes of Copenhagen (capital of Denmark). The success may, however, refect a combination of met-hods, as mass removal of planktivorous fsh and planting of submerges macrophytes were also conducted.Stocking of perchA strong stock of piscivorous perch is a precondition of the regulation of the planktivorous fsh stock, and stocking is therefore a possible method in lakes where the native perch stock is small or the number of large piscivorous perch is low. Few attempts have been done in Denmark, and they have been based purely upon perch from other lakes. DIFRES has been able to farm perch with success, which gives opportunities for fu-ture stocking. The farmed perch did not originate from a native Danish strain as they turned out to be quite resistant to stress in relation to farming and transpor-tation (H. Paulsen, DIFRES, personal communication; Overton & Paulsen, 2005). Stocking of marked perch is experimentally conducted in two Put-and-Take lakes in order to follow their growth and survival (L. Overton, DIFRES, personal communication).Removal of planktivorous fish fryIn some lakes there is a tendency towards accumula-tion of small individuals of planktivorous fsh in certain areas and certain periods of the year, for example in inlets and outlets of lakes during winter from where they can be collected in high amounts by electrofshing (up to several tons). The effect of this removal is not yet known, but is it believed that mass removal of small planktivorous fsh has a positive effect on the water quality of the lake. The method is currently being used in Lake Stubbe (see section 6.3).Perch. Photo: County of North Jutland.346. National best practices and special expertise in methods and projectsSpawning nestsThe use of spawning nests has experimentally been tried out as a tool of regulating fsh fry from particu-larly bream and roach. After spawning on the nests in April/May, nests are collected and destroyed together with the eggs. The effect is not yet validated, but there seems to be a good effect on the water quality and it is therefore planned to continue the experiment in the years to come (T. Jakobsen, County of Viborg, personal communication).Treatment of lake waterA high internal concentration of phosphorus in the bottom layer can be reduced by biological water tre-atment. The treatment plant is supplied with bottom water from the lake, cleans the water and returns it to the lake. The great advantage of this method is the permanent removal of phosphorus from the ecosystem, in contrast to the method of adding aluminium, which forces phosphorous to precipitate on the lake bottom. The Municipality of Copenhagen has recently initiated a restoration project in Lake Emdrup, where lake water is purifed by the use of an Actino treatment plant. The plant pumps in water from the lake, removes phospho-rus by adding sand, iron and a polymer and returns the water back into the lake.Use of ultrasoundAccording to the theory, ultrasound destroys the vacu-oles and other structural organelles in the cells of phy-toplankton causing these to die and sink to the bottom of the lake. A transducer (20-30 watts) is placed under the surface creating an effect upon phytoplankton within 10-150 m from the transducer. The ultrasound is allegedly not harmful to humans, animals or plants. The method has been used in the two Put-and-Take lakes. However, there is not yet any documentation of the effect.Mass removal of mainly small roach by electrofshing in Brook Gravlev. The mass removal was one of several methods used in a comprehensive restoration project in Lake Stubbe (Chapter 6.3). Photo: County of Aarhus.Eggs on spawning nests. Photo: County of Viborg.356. National best practices and special expertise in methods and projects6.3 Lake Stubbe an example of a com-pleted restoration projectThe restoration project in Lake Stubbe comprises both mass removal of planktivorous fsh and stocking of pike fry and therefore, excellently illustrates the most common restoration methods applied in Denmark. Moreover, several actions for decreasing the external nutrient loading to Lake Stubbe have been carried out prior to the fsh manipulation.Description of the lakeLake Stubbe is situated in Jutland, Denmark (10o40N, 56o15E) (Figure 6.3.1), and is a large (376 ha) and shal-low lake (maximum depth 6 m, mean depth 2.9 m) by Da-nish standards. The lake has a water volume of 11 M m3. The retention time is approx. 0.9 years and the catchment area is 62 km2. The largest inlet is Brook ksenmlle followed by Brook Ulstrup in the eastern part and Brook Gravlev in the western part. Some small inlets are ente-ring the lake in the southern part. The surroundings of the lake are replanted with conifers. Large parts of the catch-ment area consist of meadow, fen and moor habitats. In the northern and western part several summer cottages are built and smaller parts of the catchment area in the northern part are cultivated. Two other lakes are situated in the catchment area, Lake je and Lake Ulstrup Langs, which are both non-polluted clearwater lakes. Figure 6.3.1. Map over Denmark showing Lake Stubbe and its catchment area. 366. National best practices and special expertise in methods and projectsThe monitoring of the environmental state of Lake Stubbe started in 1972 with monitoring of the water chemistry. Since then the type and number of investi-gations have increased considerably (Table 6.3.1) for-ming the basis for a long and valuable series of chemi-cal and biological data. The results of the investigations are presented in several Danish reports (rhus Amt, 1980, 1982, 1986, 1993a, 1993b, 1998, 1999a,b).Lake Stubbe/year 72 73 75 76 78 84 91 97 98 00 01 02 03 04 05Water chemistry in inlet/outlet X X X XWater chemistry in the lake 9 1 5 4 7 12 19 19 19 10 10 10 12 7Fish stock X X X XSubmerged macrophytes X X XPhytoplankton X X X X X X XZooplankton X X XSediment X X X X X XTable 6.3.1.Review of the investigations conducted in Lake Stubbe in 1972-2005. X = one investigation conducted per year. Figures = indicate the number of investigations conducted in a given year. InitiativeThe intense monitoring of the environmental state of Lake Stubbe formed the basis for the decision to im-plement a restoration project in the lake. Data showed that Secchi depth as an indicator of the water quality remained poor (Figure 6.3.2) despite the fact that the external nutrient loading already had been reduced. In 1999, the County of Aarhus in co-operation with the Municipality of Ebeltoft took the fnal decision to carry out a restoration project in Lake Stubbe.0501001502002501984 1991 1997 2000 2001 2002 2003 2004 2005totalphosphorus(g/l)00,511,52totalnitrogen(mg/l)00,511,521984 1991 1997 2000 2001 2002 2003 2004 2005secchidepth(m)020406080100chlorophylla(g/l)Figure 6.3.2. Top: Long-term changes in total amount of phosphorus (columns) and total amount of nitrogen (curves) in Lake Stubbe in 1984-2005. Bottom: Long-term changes in Secchi depth (columns) and chlorophyll a (curve) in the same period. All values are summer means (May-September) (rhus Amt, 2005).376. National best practices and special expertise in methods and projectsView over Lake Stubbe. Photo: County of Aarhus.Preliminary investigationsPrior to the decision to implement a restoration project in Lake Stubbe, the Municipality of Ebeltoft examined the catchment area for external pollutants by mapping all point sources (see next section). Also, the fsh stock was investigated in 1998 according to the guidance Fish investigations in lakes (in Danish) (Miljstyrel-sen, 1990). The purpose of investigating the fsh stock was to fnd out whether the composition and the struc-ture of the fsh stock was an impediment to the water quality of the lake, and also to assess the possibility of improving the water quality through manipulation of the fsh stock.The investigation of the fsh stock revealed that roach was the dominant species (on a weight basis), whereas perch was the second most abundant species. The cal-culated total biomass of fsh was approx. 237 tonnes of which 156 tonnes consisted of planktivorous fsh. The biomass of fsh per hectare was found to be approx. 632 kg of which roach accounted for 51 %. The percentage of piscivorous fsh (piscivores:plank-tivores) was considered too low in order for the pi-scivorous fsh to control the amount of planktivorous fsh. The water quality in Lake Stubbe would therefore highly depend on the development of the composition of the fsh stock. As a consequence, it was estimated that mass removal of planktivorous fsh would be able to actively shift the lake from a turbid to a clearwater state.Reduction of the external phosphorous loading Mapping of the point sources was conducted by the Municipality of Ebeltoft and resulted in several actions to reduce the pollution from the catchment (see below). Today, probably no sewage is entering Lake Stubbe. The most important historical actions to reduce the external loading of the lake have been: 1989 New statutory order on the fsh farming area resulted in reduced discharge from a fsh farm at Brook ksenmlle upstream the inlet to Lake Stubbe due to tightened requirements on amount and type of feed 1991 Chemical precipitation of phosphorus at a nearby treatment plant 1997 Seepage of treated sewage from a nearby plant 1997 A fsh farm at Brook ksenmlle was sold and closed down afterwards 1998 Sewerage of sites build-up with summer cot-tages 1998 The family park in Ebeltoft established a seepage plantIn that way, the external phosphorus loading was re-duced to what was believed to be an acceptable level, at which the lake in a steady state (without internal loading) would be expected to have an annual mean phosphorus concentration of 50-100 g P/l - a level 386. National best practices and special expertise in methods and projectsrecommended in order to achieve an enduring effect of mass removal of planktivorous fsh (Sndergaard et al., 1998).Model calculations showed that the equilibrium con-centration in Lake Stubbe should be approx. 40 g P/l. The actual summer mean, however, was 100 g P/l in 1997. The difference is ascribed to the increased phos-phorous release from the internal phosphorus pool in the sediment during summer. The phosphorus concen-tration decreased further in the following years rea-ching a level of 80 g P/l in the summer of 2000 before the mass removal of planktivorous fsh started.PermissionsPrior to the implementation of the fsh manipulation in Lake Stubbe, the following permissions were neces-sary: Exemption from the Nature Protection Act, accor-ding to the acts section 3. Permission (according to the Fisheries Act) from the Danish Directorate of Fisheries to remove fsh using different equipments and to stock pike fry. Permissions from the landowners of the lake.One landowner was against the project and therefore did not give permission to remove fsh in his part of the lake. The arguments against the project differed - some meant that money could be used in better ways, for instance for improving the public road system. Others were afraid that the project would be the frst step towards a fully opening of the lake area to the public, the next step being establishment of a trail sy-stem around the lake. Most of the landowners, though, were positive and supportive.FinancingThe project in Lake Stubbe obtained funding from the state nature management funds applied by the County of Aarhus to cover the costs of the technical consul-tancy assistance, i.e. the mass removal of plankti-vorous fsh. The County of Aarhus and the Municipality of Ebeltoft contributed staff in the implementation phase and planning phase. Furthermore, the County of Aarhus is responsible for the subsequent monitoring of the environmental state of Lake Stubbe. Table 6.3.2 shows the budget for the practical part of the project and also for the monitoring.Budget for implementation of the restoration projectAAEurEkEurBCEurTotalEurFish investigation in 1998 including reporting 18,331 18,331Mass removal of planktivores 13,844 140,421 154,265Project management and administration 6,007 6,007Transport, gear renting etc.29,603 29,603Maintenance of equipment 2,521 2,521Disposal of fsh 6,705 6,705Fish investigations in 2000, 2001 and 2002 10,951 10,951Reporting 10,908 10,908Discount -18,357 -18,357Fish removal in Brook Gravlev in 2003, 2004 and 2005 1,006 18,630 19,636Monitoring 27,000 27,000Total 1,006 13,844 225,720 267,570Dialogue In 1999 the County of Aarhus and the Municipality of Ebeltof gave an offcial meeting inviting the pub-lic, landowners, NGOs and other interest groups. The meeting had wide support and many local people participated. The landowners and the townsmen put special emphasis on the importance of the imperturba-bility of the surroundings in connection to the project. Focus was also put on the recreational use of the lake, Table 6.3.2. Estimate of the total costs of the restoration project in Lake Stubbe in 1998-2005 (excluding staff hours) and also the monito-ring of the environmental state of the lake during and after the project. AA = the County of Aarhus, EK = the Municipality of Ebeltoft, BC = Bio/consult (consultancy company).396. National best practices and special expertise in methods and projectsThe result of the mass removal of planktiv