DECISION SUPPORT TOOLS FOR INTEGRATED WATER RESOURCES ... · DECISION SUPPORT TOOLS FOR INTEGRATED WATER RESOURCES MANAGEMENT ... data base management systems, water modelling and

DECISION SUPPORT TOOLS FOR INTEGRATED WATER RESOURCES MANAGEMENT

J. Kjelds [email protected]

T Jacobsen

[email protected]

J. Hughes, [email protected]

J. Krejcik

[email protected]

DHI Water & Environment, Agern Alle 5, 2970 Hørsholm, Denmark

ABSTRACT

Water resources and watershed management has to be dealt with in an inte-grated context and on a basin wide level. Integrated watershed management of the available water resource, hydropower, water quality and flood protection constitutes major challenges. It focuses on understanding the conditions of the water resources in order to meet requirements of various usages in the watershed. Numerous aspects have to be considered in order to respond to changes in natural phenomena and provision of adequate and good quality water at a reasonable cost to the public. In-creased focus on watershed protection and sound use of water requires that scien-tists, planners, managers and decision makers are able to quickly produce reliable estimates, assess impacts and efficiency of potential strategies.

Use and integration of sophisticated web based and GIS enabled graphical user interfaces with relational databases, visualization techniques, analysis tools and deci-sion logic greatly enhances and promotes the decision process. It enables users and decision makers focus on transparency and accessibility of results to a broad range of the public including governmental institutions, private and public stakeholders and communities involved/interested in environmental and water resources issues.

BASIN WATER MANAGEMENT 513

Decision support systems (DSS) that integrate the above components have proven reliable and effective tools in the integrated management and also in the communication of conditions and decisions.

The main objective of the paper is to demonstrate the advantages of integrating data base management systems, water modelling and decision support tools in deriv-ing a holistic management approach that is sustainable and viable.

Keywords Integrated Water Resources Management, Decision Support Tools, Modelling

INTRODUCTION

Good water management constitutes a major challenge and calls for integrated and holistic planning. Decision made now affects all and will have great impacts on generations to come. Planners and water managers must focus on obtaining a thor-ough understanding of the available water resource and potential impacts in order to meet current and future demands.

Many aspects have to be considered in order to respond to changes in natural phenomena, increase in demands, and provision of adequate and good quality water at a reasonable cost to the public. The increased competition for a finite resource requires that water managers also consider conservation and wise use of water. New and improved water management tools provide water managers the means to con-sider and assess all these complex issues as they plan for the future.

The concept of IWRM is widely debated and an unambiguous and unanimously agreed definition has yet to be seen. However, The Technical Advisory Committee of Global Water Partnership has adopted the following definition /3/:

IWRM is a process, which promotes the co-ordinated development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems.

514 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT

GOAL:Sustainable water resources utilization and management

Enablingenvironment

Institutionalframework

Planning & prioritization

Informationsystem

Waterresourcesassessment

Managementprocedures

PoliciesLegislationRegulation

Level of actionManagementboundariesCapacitybuilding

Monitoring Databases Information service

ModellingStat. + analytical toolsEIA

GuidelinesPrioritization tools Economic instruments

Water Action Plan elements

Figure1. Framework for IWRM implementation and water action plans

In order to achieve a more efficient management and sustainable development of water resources for multiple uses according to the principles of IWRM, Water Action Plans were called for in Agenda 21. The idea of an action plan, as opposed to a traditional master plan, is to create a flexible planning instrument that takes the resource, not the projected use of one or more specific sectors, as the starting point.

IWRM deals with the management of water under normal conditions as well as under flood and drought conditions. It is increasingly accepted that it is not possible under all circumstances to prevent floods from occurring and a shift has been noticed from flood prevention to flood preparedness and flood management. One important aspect to account for in such management is the trade-off between different interests. Flood prevention initiatives may run counter to irrigation or other agricultural or ecological water use priorities in a river basin and as such IWRM may not favour a maximum possible prevention of floods.

DECISION SUPPORT TOOLS

The use of integrated decision support tools is a prerequisite in proper IWRM. DSS provides a custom, flexible and dedicated management system, to assist manag-ers, decision makers and policy makers in:


♦ provide timely, transparent, well informed and reproducible answers to im-portant questions

♦ quickly and effectively streamline workflow, reduce time and cost require-ments

♦ transform data and information into knowledge and produce understand-able results and decisions

Development and implementation of a DSS is typically structured around a number of phases with well-defined functionality and scope. The DSS focuses on specific needs supporting and enabling development and production of timely, well informed and reproducible answers to essential questions. Initial phases focus on data and information management. WEB and GIS technologies are used to link and integrate databases. The water information management system empowers users to transform data and information into knowledge and provide the basis for analysis and decision support. Subsequent phases may involve adding new data, incorporat-ing and linking to other databases, applying more advanced analysis and modelling tools and expanding the decision support functionality. This evolving and dynamic business process mirrors the ever changing requirements of our society and envi-ronment.

Typical DSS interactive and integrated components are: ♦ Data and information management. The data and information component is

key and central in developing a DSS. The focus is integrating database and connecting data islands into a dynamic framework with advanced display, mapping, query and presentation capabilities.

♦ Analysis and modeling. The data framework provides the basis for further analysis and interpretation of data and information. Depending on stage and scope of the DSS the analysis can range from simple to complex including statistical and numerical models, economic and cost/benefit as well as User Defined and Custom tools

♦ Scenario management and alternative formulation. The DSS framework is capable of supporting and providing information (costing and prioritization) for project feasibility and planning projects as well as design and implemen-tation. Upon implementation the project may have an operations component that requires real time and online decision making.

♦ Decision making. Customizable GIS and Web based interfaces are tailored to meet specific needs and requirements. Advanced graphics, on-line access, custom rules and interpretations can be embedded into the DSS to support and provide the basis for decision makers to make timely, reproducible and well informed decisions


The DSS can, depending on specific needs, remain specific in scope to support a very focused and dedicated decision process. The DSS may, on the other hand, also evolve into an enterprise DSS to support a wide range of users and a broad manage-ment scope.

Figure2. DSS Components

A DSS provides for cost-effective information management, which enables pro-fessional communication between colleagues, other technical staff, managers, deci-sion makers, major stake holders and the public.

These components integrate and provide information to formulate the decision logic of the DSS. Rules and interpretations are embedded into the DSS to support and provide the basis for definition of problems and objectives

Decision support systems are frequently build within the framework of a Geo-graphical Information Systems (GIS), which provide a convenient platform for han-dling, compiling and presenting large amounts of spatial data essential to river basin management. Since GIS technology is often linked to information and knowledge management systems and is readily available to most governmental entities, a high degree of transparency in decision-making for stakeholders can be achieved.


Mathematical models are indispensable in providing a stringent and integrated description of the interaction between water-related sector aspects, such as agricul-ture/forestry, municipal and industrial water supply, hydropower, fisheries, tourism and wildlife could thereby be brought together in a framework allowing an integrated analysis. As a part of DSS models provide a sound scientific framework for co-ordinated management and planning. Advanced scenario and gaming tools support application of modelling software for planning and operational use. Technology transfer and capacity building is of paramount importance to ensure sustainability and viability of the DSS. This is provided through provision of hands-on training supported by comprehensive documentation and continued support and maintenance.

The following sections describe example projects using DSS for water manage-ment. The project examples are

♦ Water Management Planning Of The Okavango Delta, Botswana ♦ Comprehensive Everglades Restoration Project (CERP), USA ♦ Decision Support System For Development Of Accession Strategies, Czech

Republic

The projects demonstrate the advantages of integrating data base management systems, analysis, modeling and decision support tools in deriving a holistic man-agement approach that is sustainable and viable.

WATER MANAGEMENT PLANNING OF THE OKAVANGO DELTA, BOTSWANA

The Okavango Delta is located in the north-western part of Botswana, close to the border of upstream Namibia and Angola. The Okavango Delta is the largest inland delta in the world and constitutes a vast and unique wetland system. The basis for the Deltas ecological diversity and abundance of wildlife is the dynamic presence of water distributed across a 4,000-15,000 km2 area surrounded by the con-trasting Kalahari Desert. The entire Okavango Delta including wetlands, islands and the surrounding buffer zone covers roughly 90,000 km2 comprising open water, densely vegetated swamps, riparian fringe vegetation, woodlands, grass land, sa-vannah and barren land. The Okavango Delta and the upstream basins is largely unaffected by development and protection is of key importance, not only from a conservation perspective, but also with respect to economic development of tourism in Botswana relying on wildlife resources.


The Okavango Delta Management Plan project aims at establishing an inte-grated and sustainable plan for water management. The project has several compo-nents including a hydrological component, which is addressed in this paper. The hydrological conditions of the delta and the assessment of potentially adverse effects of future water management scenarios are assessed by means of an integrated hydro-logical modeling tool.

In 1997 Botswana acceded to the Ramsar Convention, and the Okavango Delta was listed as a Ramsar Site. With an area of 55,000km2 it is the largest in the world. As part of its obligations under the convention, the Botswana Government is formu-lating a management plan to ensure the maintenance of the ecological character of the site, with support from international organizations.

The ODMP Integrated Hydrologic Model has been run to simulate natural un-developed conditions in the basin and delta, present development conditions, and development conditions as they may be given a range of water resources develop-ment scenarios in the delta and the basin upstream:

♦ Upstream water resources developments: dams and irrigation schemes in Angola and Namibia

♦ Deforestation in Angola and Namibia ♦ Surface and ground water abstractions from the delta ♦ Clearing major blocked channels in the delta ♦ Regional climate changes ♦ Combinations of the above scenarios

The impacts are expressed in terms of:

♦ the overall water balance among rainfall, evapotranspiration, upstream in-flow, downstream outflow, and surface and subsurface storage changes from one year to the next

♦ the minimum and maximum depth of flooding ♦ the soil moisture and the ground water depth ♦ the minimum and maximum area flooded Results from the alternative management scenarios are made available to key

decision makers and other projects through GIS and WEB interfaces. The impacts arising from the scenarios are briefly summarized as follows:

(1) The basin and delta are presently in a near natural state. To date, land use changes and abstractions from the basin upstream and the delta have a minimal impact on the delta as whole, though local im-pacts may be significant.


(2) Based on water flows, the potential dams in Angola with a combined storage approximately equal to the annual delta inflow do not have a major impact on the delta. There is no net water consumption, and little water is stored in dry years, with correspondingly small re-leases in the dry period. The sediment transport implications could be significant, and have not been analyzed.

(3) Upstream irrigation in Namibia and especially Angola has a signifi-cant impact. The lower envelope of flooding, ie the area that remains flooded throughout, is reduced by 40% in dry years.

(4) Present and future surface and ground water abstractions from the delta are minimally significant, amounting to 0.3% and 0.5% of the inflow respectively. Under future conditions, the upper envelope of flooding, ie the area that may be flooded at some time, is decreased by around 70km2, or 0.6%.

(5) Projected climate change has the most severe impact, reducing both inflows from upstream and rainfall over the delta, and increasing temperature and the rate of evapotranspiration. The lower envelope of flooding is reduced by 68%, from 2,770km2 to 900km2.

(6) The combined water resources developments with climate change have the most severe impact on the delta. In years with normal in-flows, the range of flooded area declines from a maximum of 12,825km2 to 4,695km2, and from a minimum of 2,944km2 to 158km2.

COMPREHENSIVE EVERGLADES RESTORATION PROJECT (CERP), USA

DHI is working on many water resources planning studies in the South Florida Water Management District (SFWMD). Projects are funded by the SFWMD and by United States Army Corps of Engineers (USACE) - Jacksonville District. The remainder of this document will provide project descriptions.

The initial group of projects is called the South West Florida Feasibility Study (SWFFS). This study area consists of multiple projects throughout the area. The SWFFS area consists of four integrated surface water/ground water models that overlap in many areas. The models are referred to as the Big Cypress Basin (BCB), the Estero River Basin (EB), the Tidal Ca-loosahatchee River Basin (TCRB), and the Freshwater Caloosahatchee River Basin (FCRB).


The primary objective of the SWFFS project is to develop a seamless set of sub-regional dynamic surface/groundwater integrated hydrologic-hydraulic models that will be used for comprehensive evaluation of the existing water management facilities. The tools will also be used for to assess the ability of alternative water management strategies to meet the desired goals of flood protection, water supply, and wetland functions.

Figure3. Model Areas

In the BCB Model, the primary goal is to assess alternative strategies to restore

wetlands in the former Southern Golden Gates Estates (SGGE) area. The conceptual alternatives varied from simple (backfilling the canals) to extremely complex (multi-ple pumps and structures). The most effective alternative (Alternative 3D) included partial or total backfilling of four canals, the construction of three spreader canals, and the construction of three pump stations to lift water onto the overland flow plain during high flow conditions. Model simulations indicated that the pumps are neces-sary to prevent flooding upstream of the restoration area.


Figure4. Comparison of predicted extent of flooding under existing conditions and after system restoration implementation of Alternative 3D and system restoration.

Existing Conditions in BCB

Prediction of Wetland Restoration in BCB

The Picayune Strand Restoration Project, a component of the US Congress’s plan for restoration of America’s Everglades, aims to restore the hydrology of approxi-mately 246 square kilometers of drained wetland areas in Southwest Florida. The restoration of the Picayune Strand is important because of its location and connec-tivity to critical preserved areas that serve as wildlife habitat and also the headwaters of the Ten Thousand Islands estuary. The excessive drainage of this area led to se-vere ecological impacts such as: reduction of groundwater levels increased freshwa-ter loads to critical estuaries, invasion by exotic vegetation, increased fire frequency, and loss of wildlife habitat connectivity. The proposed restoration project consists of converting existing canals to natural wetland areas using a combination of distribu-tion canals, pump stations, canal backfilling, and road degradation.

An integrated surface water and groundwater model for the area has been de-veloped to evaluate the response of the watershed to the proposed restoration plan under a variety of hydrologic conditions. Earlier configurations of the model for the area were updated with newly acquired topographic and aquifer data and include a more detailed representation of the channel hydrography and water control struc-tures. The model has been calibrated to dry, wet, and average conditions and is ca-pable of producing simulated results that correlate well with observed surface water stage and aquifer water levels. Model calibration has also been verified using higher resolution rainfall data during the hurricane season of 1995 and 1999. The calibrated


model was applied to evaluate system responses to the proposed restoration plan. Model results indicate that the plan will restore the historical flow ways in Picayune Strand with desired hydro periods for wetland functions, and without adverse im-pact to the agricultural and urban areas adjacent to the project. The timing, magni-tude, and duration of freshwater discharges to critical estuaries located downstream of the project area will be more similar to historical discharges as a result of the pro-posed restoration activities.

DECISION SUPPORT SYSTEM FOR DEVELOPMENT OF ACCESSION STRATEGIES, CZECH REPUBLIC

The study [Carl Bro 1999] was completed with the general objective of assessing the legal, institutional and technical implications of accession of the Czech Republic to EU as background for evaluating the economic and financial implications for meeting the requirements of the EU legislation in the water sector.

An essential part of the project was to establish a Decision Support System (DSS). The purpose of the DSS was to support the development and assessment of policies and cost efficient strategies for meeting the legal requirements of directives. Moreover, the DSS are going to be used for development of national water manage-ment plans being maintained and applied by Water research Institute under the umbrella of Ministry of Environment. The DSS includes relevant data and informa-tion and adequate modeling tools to:

♦ Provide a national overview of pollution sources, river systems, water qual-

ity conditions, existing water supply and waste water treatment facilities, technical options for improvements and facilities for calculation of associ-ated costs;

♦ Assess water quality conditions as a consequence of implementing various scenarios and estimate the corresponding investment and operation and maintenance (O&M) costs;

♦ Identify least cost strategies for meeting requirements of directives for water supply and wastewater treatment specified as effluent standards and/or wa-ter quality standards.

♦ Estimate economic and financial implications of accession, including effects on investment programmes, recurrent costs and financing options


BASIC DATAPoint sourcesNon-pointsourcesExistingtreatmentTreatment options

DATABASE

WQ SIMULATION

NON-POINT LOAD MODEL

RANKING by WQMODEL

MIKE BASIN

PARAMETRICCOSTS

Investment for:New WWTPRehabilitation/upgrading ofexisting WWTPWater supplyconnection

O&M forElectricitySludge disposal

ECONOMIC ANDFINANCIAL MODEL

Financial modelWWTP optimalizationRanking by effluentsEconomic modelCost allocation and tariffmodelAffordability calculation

GRAPHICAL/GIS USER INTERFACE

SCENARIO DEFINITION

Time frames for complianceSensitive/protected areaWWTP technologyExpansion of water supplyWater qualityobjectives

OUTPUTSTABLES

VIEWS, BASIC DATATHEMATIC MAPS

PopulationPointsourcesLand-useLive stockExistingtreatment facilitiesTreatment options

RiversystemTreatmentWater supplyTownsCatchmentsSubcatchmentsSubbasinsDistricts

Technical cost ofcomplianceInvestment, O&MCost allocation bydictricts and by basinAffordabilitycalculations

Figure5. DSS Components

The user has access to the data bases and modelling tools through a graphi-

cal/GIS interface allowing a user friendly specification of the scenario wanted to be investigated as well as an easy retrieval of the results generated by the models.

Within a particular basin the definition of a scenario includes a specification of the most important parameters involved. This e.g. includes the timeframe involved (i.e. an intermediate and final year of compliance), assignment of certain areas as “EU sensitive areas” (requiring nutrient removal) or “Czech protected areas” (requiring other standards), allocation of selected effluent standards to some groups of point sources (by category, size and/or location), assignment of water quality objectives to selected river segments, assumed developments within the industrial and agricul-tural sectors, and others.


DSS components The DSS comprises databases and models and function as an integrated and

user-friendly tool, which is capable to evaluate alternative options for compliance considering legislative requirements, technical options, environmental impacts and economic/financial implications.

The DSS facilitates access to relevant information on the national scale and pro-vides a computational capability for the analysis and evaluation of different options to assist in the identification of viable strategies. This is accomplished by means of the following components:

♦ Data base, providing an overall overview of pollution sources (municipal,

industry and non-point), recipient waters, existing water quality and hydro-logical conditions, water supply and waste water treatment facilities, tech-nical options for improvements; basic statistical data from MOE and hydro-logical and topographical data,

♦ Parametric cost functions for the different technical options showing the re-quired investments and annual O&M costs as a function of the number of person equivalents and required effluent standard; in case of treatment or water supply facilities and connectivity of inhabitants,

♦ Water quality models for determining the load from non-point sources and simulation of the resulting water quality conditions as a consequence of as-signing different treatment levels to the individual point sources. The model also accounts for the corresponding investments and O&M costs. If appro-priate, the simulation models may be used within optimization procedure.

♦ Optimization model to identify least cost strategies for meeting specified ambient water quality objectives, which are accessible in the combination with certain effluent standards for upgraded treatment. There are available two optimization-ranking algorithms, one based on ranking of effluents from point sources related to executed investment through cost matrix, and the second based on emission principle taking into account pollution reduc-tion in rivers due to the target investment based on ranking. The letter is fully dependent on simulation of WQ by the models;

♦ Economic and financial models for determining the net present value of compliance costs covering capital investment plans and associated O&M costs in both economic and financial terms. Further, cost allocation between the public sector and water users is assessed based on the various institu-tional scenarios. The user will have access to the data bases and modeling tools through a graphical/GIS interface allowing a user friendly specification of the scenario, which is to be investigated as well as an easy retrieval of the results generated by the models.


The Decision Support System has been designed to model pre-defined scenarios for accession process and its economical and technical incidence. Relevant data needed for the application of the different models and for the evaluation of defined scenarios have been included in a database, comprising a combined GIS and RDBMS.

The scenario definition is one of the essential parts of using DSS. The user has to decide among many different options and technical parameters in order to define just one selected scenario.

Scenario definition

Three main scenarios were defined and computations by DSS were done for these scenarios. The requirements for wastewater treatment and WQ objectives were defined as follows:

Scenario 1 - EU requirements for NON-SENSITIVE areas were applied for whole country

Scenario 2 - EU requirements for SENSITIVE areas were applied for whole country

Scenario 3 - All basins, where the reservoirs for drinking water supply are situated + all basins where reservoirs assigned for recreation are situated + catchments of all river reaches which are as-signed as a source for water supply exceeding 500.000m3/year were assigned as sensitive areas. According to such definition the sensitive area will be 61% of whole country

For all of three scenarios were basic additional options defined as follows: ♦ EU cost level for the new sewer connections were used. ♦ 20% of the sludge disposal to the landfill side and 80% to incineration was

assigned ♦ Optimization of the new WWTP by the merging was applied ♦ Percentage of the connection to the central water supply was assigned to

94% globally. ♦ Ranking procedure based on load reduction has been applied

The concentrations for all WQ indicators are generated for all of more than 400 computational nodes for all of intermediate stage of compliance. In order to evaluate environmental benefits of each particular scenario and IP matrix the data were as-sorted and processed. In order to present the environmental benefits of the each


intermediate investment programme the change of water quality in selected river branch during the time is presented. The user is able to compare the reduction of the concentration of the selected indicator in any of computational node within the sys-tem. The shape of the “reduction curve” generated by applying the intermediate stages of one scenario could be presented. The relation between environmental bene-fits and total of investments is could be thus demonstrated.

Figure6. Simulated in-stream water quality (BOD) from Scenario3.

The baseline status is shown on the left while on the right water quality reached by implemen-tation of all investments within Scenario 3 is presented.

In order to present environmental benefits of all scenarios within Czech Repub-

lic the maps of WQ for the entire river network were generated directly from DSS. All river branches are drawn and water quality for selected parameter is assorted to user-defined intervals by different colors. The improvement of water quality for any stage of any selected scenario could be investigated directly and “user-friendly”.

CONCLUSION

Successful development and application of Decision Support Tools demonstrates the benefits of integrated use of web based and GIS enabled graphical user interfaces with relational databases, visualization techniques, analysis tools and decision logic. Such powerful DSS enables managers and decision makers to quickly obtain ques-tions to critical questions and to focus on transparency and accessibility of results.

The ever increasing focus on watershed management and sound use of water requires that scientists, planners, managers and decision makers are able to quickly produce reliable estimates, assess impacts and efficiency of potential strategies.


REFERENCES

Bach H.K, Brink H., Olesen K. W., Havnø, K.(1989), “Application of PC- Based Models in river and water quality modelling ” Proceedings of the International conference on computational hydraulics and environmental modelling , University of Bradford, England.

Nielsen S A., Hansen E.(1973), “Numerical simulation of the rainfall runoff process on a daily basis.” Nordic Hydrology, 4 pp. 171-190.

DHI Water & Environment, “MIKE BASIN Users Manual Version 2000 for Windows 95, 2000”, Horsholm

Global Water Partnership, Technical Advisory Committee (TAC): “Integrated Water Resources Management”, TAC Background Papers, No. 4, 2000

Havnø, K., Madsen, M.N., and Dørge, J. “MIKE 11 - A Generalized River Package” V.P. Singh (Ed) Computer Models of Watershed Hydrology, Water Resources Publications, 733-782, 1995.

Jha, M. K., “Application of Mike Basin for Water Management in Mun River Basin, Thai-land”, AIT Thesis no. WM-00-05, Asian Institute of Technology, Thailand.

Madsen, M., Quian-Ming, Lu, Havnø, K., Larsen, H., “The Role of Mathematical Models During Strategy Formulation for Water Resources and Waste Water Management in the Sichuan Province, China”. Int. Conf. On Water, Environment, Ecology, Socio-economics, and Health Eng., Seoul, S. Korea, Oct. 18 - 21, 1999.

Havnø, K., “Integrated River Basin Management in Relation to Flooding”. Int. Confer-ence for Mozambique Flood, Maputo, Mozambique, 25-28 October 2000.

Carl Bro, Hydroinform, DHI, EPE, Nondek/Dusik, Warren, Aquafin, VRV and Masaryk Institute. September (1999). “Pre-accession Planning to Meet the Requirements of EU Legislation in the Water Sector in Czech Republic”. Final Report and 5 Annexes to the Ministry of Environment of Czech Republic. Granted by Danish Environ-mental Protection Agency

McCarthy, T.S., Larkin, P.A., Bloem, A., 1998. “Observations on the hydrology and geohy-drology of the Okavango Delta”. South African Journal of Geology, p. 101–117

Gumbricht T., Wolski P., Frost P., McCarthy T.S., “Forecasting the spatial extent of the annual flood in the Okavango Delta, Botswana”, Journal of Hydrology 290 (2004), p. 178–191

McCarthy, T.S., Cooper, G.R.J., Tyson, P.D. and Ellery, W.N., “Seasonal Flooding in the Okavango Delta, Botswana - Recent History and Future Prospects”. South African Journal of Science, (2000) vol.96, p. 25-33.

Bauer, P., Flooding and Salt Transport in the Okavango Delta, PhD thesis, Swiss Federal Institute of Technology, Zurich (2004)

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DECISION SUPPORT TOOLS FOR INTEGRATED WATER RESOURCES ... · DECISION SUPPORT TOOLS FOR INTEGRATED WATER RESOURCES MANAGEMENT ... data base management systems, water modelling and