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WTP20WORLD BANK TECHNICAL PAPER NUMBER 20 April 1984
Water Quality in Hydroelectric ProjectsConsiderations for Planning in Tropical Forest Regions
Camilo E. Garzon
TD326.5* G371984c2
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WORLD BANK TECHNICAL PAPER NUMBER 20
Water Quality in Hydroelectric ProjectsConsiderations for Planning in Tropical Forest Regions
Camilo E. Garzon
The World BankWashington, D.C., U.S.A.
Copyright Oc 1984The International Bank for Reconstructionand Development / THE WORLD BANK1818 H Street, N.W.Washington, D.C. 20433, U.S.A.
First printing April 1984All rights reservedManufactured in the United States of America
This is a document published informally by the World Bank. In order thatthe information contained in it can be presented with the least possibledelay, the typescript has not been prepared in accordance with theprocedures appropriate to formal printed texts, and the World Bank acceptsno responsibility for errors. The publication is supplied at a token charge todefray part of the cost of manufacture and distribution.
The views and interpretations in this document are those of the author(s)and should not be attributed to the World Bank, to its affiliatedorganizations, or to any individual acting on their behalf. Any maps usedhave been prepared solely for the convenience of the readers; thedenominations used and the boundaries shown do not imply, on the part ofthe World Bank and its affiliates, any judgment on the legal status of anyterritory or any endorsement or acceptance of such boundaries.
The full range of World Bank publications, both free and for sale, isdescribed in the Catalog of Publications; the continuing research program isoutlined in Abstracts of Current Studies. Both booklets are updated annually;the most recent edition of each is available without charge from thePublications Sales Unit, Department T, The World Bank, 1818 H Street, N.W.,Washington, D.C. 20433, U.S.A., or from the European Office of the Bank, 66,avenue d'Iena, 75116 Paris, France.
Camilo E. Garzon is a Doctor of Engineering candidate at the ResourcePolicy Center of the Thayer School of Engineering, Dartmouth College, andan environmental engineering consultant to the World Bank.
Library of Congress Cataloging in Publication Data
Garzon, Camilo E., 1948-Water quality in hydroelectric projects.
'7(World Bank technical paper ; no. 20)Includes bibliographical references.1. Water quality management--Tropics. 2. Hydroelectric
power plants--Environmental aspects--Tropics. 3. Reser-voir ecology--Tropics. 4. Forests and forestry--Environ-mental aspects--Tropics. I. Title. II. Series.TD326.5.G37 1984 333.91'4 84-7312ISBN 0-8213-0363-5
- iii -
ABSTRACT
This paper identifies and describes the studies necessary to
predict water quality changes, at an early state of planning, in large
tropical reservoirs with long retention times. Emphasis is placed on both
the reservoir area and the region downstream. The need for defining the
"baseline" environment is presented as a requirement for conducting
studies associated with the flooding and operating stages. These studies
are classified according to the stage of project development.
In the reservoir area, aspects such as biomass quantification,
reservoir thermal stratification, water circulation, dissolved oxygen
consumption and reservoir recovery are of major importance. Downstream
from the project, the stress is placed on river recovery capacity, water
uses and conflicts, and flow requirements. The results obtained from the
studies serve as the basis for deciding the extent of forest clearing and
other mitigatory measures.
The paper illustrates that biological degradation in tropical
reservoirs follows a significantly different path from that in reservoirs
in temperate zones, thus, conventional approaches to reservoir clearing
and filling may not be adequate for projects in forested tropical
regions. Two approaches - for project feasibility and project design -
are suggested in order to meet the need for successive refinement in the
results, and to take advantage of the increasing availability of project
and environmental information.
- iv -
ABSTRAIT
Ce document identifie et decrit les etudes A effectuer pour predire,
A un stade peu avance de la planification, les variations de la qualite de
l'eau dans les grands reservoirs tropicaux A longue dur6e de retention. I1
met l'accent A la fois sur la superficie du reservoir et sur la region en
aval. La necessite de definir les elements de base de 1'environnement est
pr6sentee comme une condition necessaire A l'ex6cution des 6tudes li6es aux
stades de la submersion et de l'utilisation. Ces etudes sont class6es selon
le stade d'avancement du projet.
Vis-a-vis de l'6tendue couverte par le r6servoir, certains aspects
tels que l'6valuation quantitative de la biomasse, la stratification thermique
du reservoir, la circulation de l'eau, la consommation d'oxygene dissous et la
remontee du niveau de l'eau sont particulierement importants. En aval du pro-
jet, l'accent est mis sur la capacit6 de retablissement du debit du cours
d'eau, sur les utilisations de l'eau et les conflits A ce sujet, ainsi que sur
les besoins en matiere de debit. Les resultats de ces etudes servent de base
aux decisions concernant l'etendue de forat a deboiser et autres mesures des-
tin6es a am6liorer la qualit6 de l'eau.
Cette etude montre que la degradation biologique qui se produit dans
les reservoirs tropicaux suit une vole sensiblement differente de celle que
l'on observe dans les r6servoirs des zones temperees, de sorte que les
m6thodes classiques de deboisement et de remplissage pourraient ne pas conve-
nir aux projets d'amenagement de r6servoir dans les regions tropicales. Deux
formules sont preconis6es - pour les etudes de faisabilit6 et la conception
des projets - afin de repondre A la necessite d'apporter plusieurs am6liora-
tions successives aux resultats et de tirer profit de la disponibilite crois-
sante d'informations sur les projets et sur l'environnement.
- v -
EXTRACTO
En este trabajo se identifican y describen los estudios necesarios para
predecir, en una etapa inicial de la planificacion, los cambios de la calidad
del agua que ocurren en los embalses grandes con periodos de retencion prolonga-
dos que se construyen en zonas tropicales, dandose especial importancia a los
estudios tanto de la zona del embalse como de la situada aguas abajo del pro-
yecto. Ademas, se subraya la necesidad de definir el medio ambiente "basico"
para la realizacion de los estudios relacionados con las etapas de inundaci6n y
funcionamiento. Estos estudios se clasifican de acuerdo con la respectiva etapa
de ejecuci6n del proyecto.
En lo que se refiere a la zona del embalse, aspectos tales como la cuanti-
ficaci6n de la biomasa, la estratificaci6n termnica, la circulaci6n del agua, el
consumo de oxigeno disuelto y la recuperaci6n revisten primordial importancia.
En cuanto a la zona situada aguas abajo, se hace especial hincapie en la capaci-
dad de recuperaci6n del rio, en los usos del agua y los posibles conflictos al
respecto y en los requisitos en materia de caudal. Los resultados que se obtie-
nen con los estudios sirven de base para las decisiones relati;vas al alcance del
desbroce de la zona forestal y otros paliativos.
Se muestra graficamente en el trabajo que la degradaci6n biol6gica en los
embalses de las zonas tropicales sigue una trayectoria notablemente diferente de
la que sigue en los de las zonas templadas; por lo tanto, es posible que los
metodos usuales de desbroce y llenado no sean adecuados para los proyectos que
se llevan a cabo en regiones forestales tropicales. Se sugieren dos enfoques
--para la evaluaci6n de la viabilidad y el disefio de los proyectos-- a fin de
satisfacer la necesidad de refinamiento sucesivo de los resultados y de aprove-
char la disponibilidad cada vez mayor de informacion sobre los proyectos y los
aspectos ambientales.
- vii -
TABLE OF CONTENTS
ABSTRACT
PREFACE
INTRODUCTION ........... 1
1. PROBLEM OVERVIEW ... ......................... 3
1.1 Upstream Area .......... 3
1.2 Reservoir Area .......... 3
1.3 Downstream Area ...................... 6
2. RESERVOIR WATER QUALITY PREDICTIONS ..... ................. 8
2.1 Biomass Decomposition .................. 8
2.2 Hydrothermal Behavior and Circulation Patterns ...... 132.3 Oxygen Balance ................. ..................... 20
2.4 Reservoir Recovery .................. ................ 24
3. RIVER WATER QUALITY PREDICTIONS ........... ............... 26
4. SUMMARY OF PROPOSED APPROACHES .................. ......... 30
REFERENCES ............................................... 32
- viii -
TABLES
Table 1 Aspects Related to Water Quality Management .... ...... 4
Table 2 General Composition of Plant Tissues . ................ 9
Table 3 Dissolved Oxygen Balance during the Filling Process .. 21
FIGURES
Figure 1 Water Quality as a Function of Reservoir Retention
Time and Area. 2
Figure 2 Simplified Organic Carbon Cycle of a Typical Freshwater
Lake ................................................ 12
Figure 3 Schematic Arrangement of Thermal Lake Types .... ...... 15
Figure 4 Oxygen Isopleths in a Length Profile of the Reservoir
along the Former Suriname River (dry period) .16
Figure 5 Oxygen Isopleths in a Length Profile of the Reservoir
along the Former Suriname River (rainy period) .17
Figure 6 Temperature and Oxygen Content at Different Depths at
Kabelstation, Suriname ......... ...................... 18
Figure 7 Water Densities for Various Temperatures .... ......... 19
Figure 8 Reservoir Filling Process ....... ..................... 22
Figure 9 Oxygen Consumption ............ ....................... 23
Figure 10 Reservoir Recovery Process ....... .................... 25
Figure 11 Dissolved Oxygen Profile of the Lower Rio Sinu
(flow 400 m3 /sec) .27
Figure 12 Dissolved Oxygen Profile of the Lower Rio Sinu
(flow 50 m3 /sec) ......... ............................ 28
Figure 13 Dissolved Oxygen Profile of a Hypothetical River ..... 29
Figure 14 Proposed Water Quality Considerations .... ............ 31
- ix -
PREFACE
This paper is a summary of material presented at a World Bank
Seminar on March 1, 1983, sponsored by the Energy and Industry Staff, and
by the Office of Environmental Affairs. The intent is to outline tropical
reservoir water quality management as related to the various aspects of
the planning process.
The paper presents an analytical appraisal and predictions
stemming from poor water quality conditions as a result of the
decomposition of great amounts of biomass flooded by their associated
reservoirs. This issue is important because of the increasing number of
hydroprojects being planned in regions with tropical wet forests. The
predictions presented serve as a basis for the decision and extent of
forest clearing and the need for structural and managerial remedial
measures.
The World Bank Seminar and paper resulted from the World Bank's
requirement for environmental consideration of the Urra Hydroproject,
located in northeastern Colombia, which is expected to begin operating in
1988. The environmental studies conducted by the author clearly show both
the technical aspects of the project layout and the elements of the
surrounding environment. The need for further quantitative analysis and
the complexity of the phenomena involved suggest the need for an
innovative and technologically advanced approach. The efforts made at the
Urra Project represent a step in this direction.
I wish to thank Mr. R. Goodland and Mr. J.J. Fish for their kind
invitation to present the seminar, to write this paper and their most
helpful and detailed improvements. Several people involved with the Urra
Project have contributed to the ideas introduced, and their contribution
is gratefully acknowledged. The views presented here are personal and
should not be attributed to the World Bank.
INTRODUCTION
The water quality problems addressed by this paper refer mainly
to the situation encountered when large amounts of tropical vegetation
(i.e., tropical rain forest) are flooded by new reservoirs. The original
river water quality deteriorates so drastically as to impair human
consumption and most economic uses. In hydroelectric projects which
require relatively large river flows, this situation becomes exacerbated
when the reservoir's retention time (mean volume/mean flow) is also
large. Figure 1 shows the region of main concern. The boundary line
shown between regions is arbitrary. In addition to retention time and
area, other variables such as mean depth, climatic conditions and
reservoir morphometry, can increase or decrease water quality problems.
This particular reservoir category has not been sufficiently
studied mainly because very few hydroprojects have presented those
characteristics. However, the few projects built under these conditions
have developed various kinds of environmental problems--water quality
being one of the most serious. A good example of this is the Brokopondo
Lake (Afobaka Dam) in Suriname, built in 1964, which is illustrated in
Section 2.2 (Heide, 1976; Panday 1977). Several other important
hydroelectric projects are in the planning process in tropical developing
countries, for example in the Amazon basin (Goodland, 1978) and in
Colombia's Pacific Region (DNP, 1979). They will require detailed
analyses if water quality and other environmental disturbances are to be
prevented. The potential for similar water quality problems also is
significant in Equatorial Africa and Southern Asia.
FIGURE 1
Water Quality as a Function of Reservoir Retention Time and Area
Area Covered 1,500by Forest
(kin2 )
Region o ntesWater Qualt
1,000 ~~~~~~~~Problems
500
II I X I ,1 1 1 1
6 12 18 24 30 36 42 48
Retention Time (Months)
World Bank-2521
- 3 -
This paper points out the need for two successive approaches in
predicting water quality changes, and answering the question of how much
forest clearing should be carried out in order to ensure the required
quality of water. Extensive clearing is such a costly remedial measure,
that it could compromise the feasibility of the project itself.
1. PROBLEM OVERVIEW
Aspects directly or indirectly related to the water quality issue
are summarized in Table 1. They are organized both by geographical
location and by stage of project development. The column entitled
'Baseline Environment" comprises the studies which will become the bases
for the predictions listed on the two following columns.
1.1 Upstream Area
Inflowing tributaries acquire their physical, chemical and
biological characteristics in the watershed, upstream from the reservoir.
Parameters such as water temperature, nutrient concentration, pH and
organic content define significant properties of the incoming rivers that
will partially determine the nature of the water quality in future
reservoirs. However, this influence is more noticeable in short
retention-time reservoirs than in stagnant reservoirs. In the latter, the
effect will be manifested over a longer time span, i.e., during the
reservoir "recovery" period. (See Section 2.4) For the same reason,
prediction of future changes in land use and in the ensuing water quality
characteristics will become necessary.
1.2 Reservoir Area
The reservoir area, which is to be inundated, requires several
descriptive studies. First, it needs a quantification of the amounts and
-4-
TABLE 1
Aspects Related To Water Quality Management- Descriptive and Predictive Studies-
STAGES BASELINE ENVIRONMENT RESERVOIR FORMATION PROJECT OPERATIONLOCATION
UPSTREAM WATERSHED WATERSHEI)Land Use Land Use Changes
RIVER CHARACTERISTICS RIVER CHARACTERISTICSQuantity Quality Changes
Quality
RESERVOIR VEGETATION FLOODING PROCESS RESERVOIR USEAREA Amounts Areas Covered Fishing
Types Duration Recreation
Elemental Composition OthersHYDROTHERMAL BEHAVIOR
Development of Strati- HYDROTHERMAL BEHAVIORSOIL CHARACTERISTICS fication Stratification/
StabilityCLIMATIC ASPECTS DISSOLVED OXYGEN BUDGET
Ambient Temperature Aerobic/Anaerobic CIRCULATION PATTERNSSolar Radiation Conditions MorphometryRelative lHumidityCloud Cover CIRCULATION PATTERNS WATER QUALITYWind Direction/Speed Changing Morphometry Fertilization
RecoveryLOW-LEVEL DISCHARGES
INTAKE CONFIGURATION
DOWNSTREAM RIVER CHARACTERISTICS MINIMUM FLOWS REQUIRED HYDROLOGIC ASPECTSBiochemical Seasonal Requirements "Dry" ReachesHydraulic, Hydrologic Water Uses Flow Fluctuations
QUANTITY-QUAI.TY RELA- WATER QUALITY WATER QUALITYTIONSHIPS Parameter Profiles Parameter Profiles
Tributaries Effect of Tributaries
Delta Assimilation CapacityOther Features
WATER USES RECOVERYHuman ConsumptionFishingIrrigationWaste Water DisposalOthers
-5 -
types of existing vegetation. This task is better conducted in two stages,
as outlined below. At the outset, an estimate of the readily degradable
fraction of the vegetation will suffice. 1/ Later, for more detailed
analyses, the elemental composition of the biodegradable fraction will be
required in order to estimate the input of nutrients into the water. The
input of the superficial soil also has to be taken into account. Although
tropical forest soils are usually nutrient-poor, this characteristic varies
from one region to another. Soil organic content, on the other hand, tends
to be relatively high when compared to temperate forests. Estimates based
on data from forest ecosystem studies conducted in similar regions have
proven useful, even though forest studies are not usually conducted with
the same purpose in mind.
Second, the climatic characteristics of the region should be
evaluated. This is usually an easier task, since most needed data are
collected routinely by weather stations in the area and by engineering
studies. For instance, ambient temperature, relative humidity and wind
direction and speed data are gathered this way. Solar radiation and cloud
cover may require additional measurements on the part of the water quality
analysts. Climatological data serve as the bases for predicting the
hydrothermal and mixing behavior of the future reservoir.
1/ Degradable fraction of vegetation includes leaves, twigs, flowers,
fruits, portions of the bark and other softer outer tissues which
decompose during the first few months. Knowledge of the biodegradable
fraction, expressed in tons/hectares, for example, will allow
calculation of the amount of dissolved oxygen which will be extracted
from the water during the decomposition process following flooding.
- 6 -
During reservoir formation, increasingly larger areas of forest
will be flooded. The longer the reservoir retention time, the longer this
process will last. Topographic characteristics of the area (the future
reservoir morphometry), together with the hydrologic behavior of the
tributaries will determine the probable amounts of organic matter added to
the water mass per unit time. This relatively simple calculation (see
Section 2.3) provides initial estimates of dissolved oxygen content, and
consequently, of other parameters intimately related to this vital
component. The quality of the waters discharged through any low-level
(i.e., deep) outlets will be impaired if anaerobic conditions developed
within the water column.
After filling, the reservoir will behave in a manner resembling
that of a natural lake. If large amounts of vegetation are flooded, the
reservoir will undergo a slow recovery process. Depending on need, this
recovery process can be somewhat accelerated by intake configuration and
reservoir water level control (Garzon, 1983).
1.3 Downstream Area
Additional studies are needed in the areas located along the
river, downstream from the project site as summarized in Table 1, to
determine the river self-purification capacity, and the existing and
potential water uses. The river self-purification capacity can be
reliably estimated from its hydraulic and hydrologic characteristics.
Deoxygenation and reaeration coefficients which are functions of molecular
diffusion, water velocity, depth and temperature, will serve to estimate
the dissolved oxygen levels along the river course. 2/ Other features
such as incoming tributaries, interconnected seasonal lakes, estuaries and
salt water intrusion at the river delta will have to be evaluated. The
latter may play an important role if the reservoir filling process is
protracted. During this period, in the absence of major tributaries
downstream from the project site, a substantially reduced river flow can
cause a detrimental increase in salinity concentrations near the delta.
Once the predictions for both the filling and the operational
periods of the reservoir water quality have been made, estimates on the
river water quality can be derived downstream from the project.
Thereafter, possible conflicts with highly demanding uses, such as human
2/ The differential equation (simplified for our case) that describes therate of change of oxygen concentration in the river is of the form:dO = K2 (0*-0) - K1 Ldt
where 0 = concentration of oxygen (mg/l)
0* = saturation concentration of oxygen at the local temperatureand pressure
K2 = reaeration coefficient
K1 = deoxygenation coefficient (temperature dependent)
L = bioquemical oxygen demand (B.O.D.)
Numerous equations have been developed to compute the reaerationcoefficient. An example is the O'Conner and Dobbins approach:
0.5K2 = (Dm v) at 200C
d1.5
where Dm = molecular diffusion coefficientv = mean water velocity in the riverd = mean stream depth
- 8 -
consumption and fisheries, should be identified. Similarly, minimum flows
required during filling, and even during project operation, should be
determined; and lastly, river recovery, corresponding to the slow
reservoir recovery also should be established.
In developing countries, water use downstream will normally
determine the water quality required from the project. River water
quality studies, thus, become a critical task. Fortunately, adequate
technological tools exist to make this a relatively easy and reliable
operation. However, this cannot be said about reservoir water quality
predictions. These predictions still pose a great challenge that will
have to be at least partly circumvented both by ingenuity and by
simplification of the real processes involved. The following sections
deal in more detail with the major aspects to be considered.
2. RESERVOIR WATER QUALITY PREDICTIONS
There are four major topics in the reservoir water quality
prediction process: a vegetation inventory and decomposition study; an
analysis of the thermal stratification and wind-driven circulation
patterns; an estimate of dissolved oxygen consumption within the water
mass; and a projection of the recovery process.
2.1 Biomass Decomposition
Biodegradable Fraction
The great diversity of organic chemical compounds which
constitute the various parts of the vegetation can hardly be
overestimated. After flooding, each substance decays following unique
chemical pathways, producing different intermediate compounds and
interacting at various rates with other substances. Detailed predictions
-9-
of this process is nearly an impossible task. Great simplifications can
be made however, and still reflect the general decomposition trends.
Table 2 is an example of typical ranges in the composition of
plant tissue. It shows that vegetation biomass consists primarily of
substances that are difficult to decompose, such as hemicelluloses,
celluloses and lignin (Goldstein, 1981). Lignin is most resistant to
biochemical degradation. The ability to break it down is possessed
primarily by aerobic fungi. It is regarded as virtually undegradable by
anaerobic processes (Hobson, 1974). In contrast, proteins, sugars and
starches decompose readily and become the substances of immediate
concern. The green parts of the vegetation not only have a higher
proportion of biodegradable substances, but also are more vulnerable to
bacterial attack due to both their large surface area/volume ratios and
their softer tissues.
TABLE 2
General Composition Of Plant Tissues
Component Percentage
Carbohydrates
Sugars and Starches 1 - 05
Hemicelluloses 10 - 28
Cellulose 20 - 50
Fats, waxes, tannins 1 - 08
Lignins 10 - 30
Proteins
Simple water soluble
and crude protein 10 - 15
Brady (1974), Goldstein (1981).
- 10 -
Defining the amount of vegetation (biomass) present within the
future reservoir area should be the starting point in the evaluation
process, since biomass density varies widely from one place to another.
Tropical wet forest biomass is generally high (between 300 and 900
ton/ha), while temperate forest biomass varies between 200 and 400 ton/ha
(Dames and Moore, 1982). Estimates could be obtained by comparing biomass
in similar forest types during the feasibility stage of the project.
Field reconnaissance is needed to check the general validity of the
assumptions. Later, during the design stage, nondestructive and
destructive biomass sampling should be used to refine the initial
estimates.
As mentioned above, the principal reason for the biomass
estimates is to determine the portion of biodegradable organic matter
present in the vegetation. For this reason, the procedures and analysis
will vary slightly with respect to traditional forest studies. Emphasis
should be placed on the green and softer parts of the vegetation, their
biodegradable substances and their elemental (i.e., nutrient)
composition. The green, readily biodegradable portion of the vegetation
normally constitutes 10% or less (by weight) of the total biomass density.
Elemental phosphorus, a key element in fresh water eutrophication, is
often found in amounts of approximately 50 kg/ha of forest (Dames & Moore,
1982).
Analogously, the organic matter, including roots and the nutrient
content of the forest superficial soils, also should be measured.
Although tropical forest soils are poor in nutrient concentrations, the
amounts of humus and other decaying organic substances could become a
significant variable.
- 11 -
Chemical Pathways
Initially, enough dissolved oxygen will be available in the water
mass for biomass decomposition to be aerobic. Facultative and aerobic
bacteria will oxidize the organic matter to the stable and relatively
unobjectionable products: CO29 NO3-, SO4=s P04-.
As the available oxygen is used up, anaerobic and facultative
bacteria will convert the organic matter to simpler organic and inorganic
compounds. Substances like CHRV CO2 H 2S, NH3, and H2will be
produced. The methane-forming bacteria are strictly anaerobic and very
sensitive to acidic conditions. Cellulose, which could be decomposed to
hexane, organic acids and CH4, would remain unaltered under acidic
conditions.
A simplified organic carbon cycle is presented in Figure 2. It
illustrates the contrast between aerobic and anaerobic conditions. The
latter normally occur in the sediments of freshwater lakes. When the
water overlying the sediments becomes anaerobic, the general direction of
mineral movement is reversed. Compounds, such as those containing iron,
manganese, phosphorus and sulfur, redissolve in the water and can reach
high concentrations. Additionally, the rates of decomposition decrease
under anaerobic conditions. Similar cycles could also be presented for
other important elements such as sulfur, phosphorus and nitrogen (Goldman,
1983).
The degree of anaerobiosis will also affect the relative
proportion of the products. For example, some authors classify the
existing reducing conditions under the following stages (Gunninson, 1981).
a. Dissolved oxygen exhaustion (Redox potential: 300 - 400 mV)
Nitrates begin to replace oxygen as inorganic electron
acceptors for microbial processes.
- 12 -
Figure 2Simpiffied Organic Carbon Cycle of a Typical Freshwater Lake.
DOC and POC =Dissolved and Particulate Organic Carbon; PSPhotosynthesis; R = Respiration. (Modified from Kuznetsov, 1959,1970.)
rADlochthorK)s ||ouO || DOC, POC | DC O
Dissociatio HO 3
\EternalHumic PSSubstances & Littoral Flora, Phytoplonkton.Piant Residues R Autotrophic & Chemosynthetic Bacteria
Groundwater
n Cellulose Hemicelluloses i 2 -> i) _ U i . L ~~~~~& F'ectins {:
Dissolved O aan,,rganic | |
\ O o 3 & a r H~~~~~~~~~etwrophic |A u d
i f r ~Hum ....ic'_J I LCompounds |o
t < ~~~~~~~~~Bacteri > /
\ \\ I ~~Ancierobic Decomposto L;F gctenim \ \\ ~~~~Heterotrophic Bacter E/
\ Oranic omponds
World Ebank-25122
- 13 -
b. Ammonia accumulation (Redox potential: 220 - 300 mV)
Ammonia produced by nitrate reduction accumulates.
Inorganic phosphorus is released from the sediments and from
phosphorus-bearing organic matter.
c. Manganese accumulation (Redox potential: 200 - 220 mV)
Reduced manganese is released from sediments.
d. Iron accumulation (Redox potential: 120 mV)
Ferrous iron becomes soluble in water.
e. Sulfate reduction (Redox potential: - 120 - - 150 mV)
Reduction of sulfide begins.
f. Methanogenesis (Redox potential: below - 500 mV)
Methane production begins and continues until the carbon
substrate is depleted or the reservoir destratifies.
In lakes and reservoirs where the hypolimnion (the part below the
thermocline) is anaerobic, the "intensity" of the reducing conditions will
usually increase with depth. This is particularly important during the
flooding process when minimum flows in the river downstream may require
the release of poor quality, low-level discharges.
2.2 Hydrothermal Behavior and Circulation Patterns
An important aspect, too complex to be treated in detail in this
paper, is the mixing regime in the reservoir. Two distinct but related
phenomena determine this behavior: the thermal energy transfers and the
wind driven circulation patterns.
Thermal energy is transferred primarily through the air-water
interphase and, advectively, through the inflows and outflows. At the
reservoir surface, evaporation and radiation are the two main exchange
- 14 -
mechanisms. Thus, humidity, ambient temperature, wind speed, cloud cover
and optical characteristics of the water are important variables. Wind
stirring and convective overturns usually mix the heat gained from the sun
to depths greater than the light penetration depth.
In tropical latitudes at low elevations, deep water masses tend
to stratify thermally and to remain stratified for longer periods than in
temperate climates. Oligomictic behavior (i.e., water bodies with little
mixing) constitutes a major difference from the better known dimictic (two
annual mixing) patterns as shown in Figure 3. This fairly permanent
thermal stratification becomes, in turn, an effective barrier to the
transfer of mechanical (i.e., wind induced) mixing and to mass transport.
Oxygen, which could be gained from the atmosphere and from photosynthesis,
is confined to the upper layers by the thermocline. Figures 4, 5 and 6
illustrate the situation that developed in the Brokopondo Reservoir. The
confinement of oxygen to the upper layers and its close correspondence to
the water temperature profile are clearly shown in these figures. The
role of simple molecular oxygen diffusion across the thermocline has not
been fully determined, although most authors contend that it can be
neglected. An example of the small contribution attributed to this mass
transfer mechanism is given by Fisher (1979) with reference to the
Wellington Reservoir in Western Australia. The importance of a five
degree centigrate difference in the water density at different temperature
ranges is illustrated in Figure 7. Clearly, at high temperatures related
to tropical conditions, a five-degree difference imparts more stability to
the stratified water column than at low temperatures.
- 15 -
FIGURE 3
Schematic Arrangement of Thermal Lake Types
'6000-
5000-
4000-
30-0E- -°° I
I-
1000 $..
90 80 70 60 50 40 30 20 10 0DEGREES LATITUDE
Based on Hutchinson and Loffler, 1956.
- 16 -
FIGURE 4
Oxygen Isopleths in a Length Profileof the Reservoir along the Former Suriname River
(dry period)
Mamadam KoenkoenRapids Rapids Grankreek Bedoti Kabelstation Afobaka
Depth
Meters
28 FORMER SURINAME RIVER BED: / / / / /.
*3 000i5n0354 45 50 A5;
.5 10 15 20 25 30 35 40 45 50 55 60 65 70River Kilometers
Note: Reconstruction of oxygen isopleths in a length profile of the lake along the FORMERSURINAMvE RIVER. on 30.XI.-3.X11.1965. Figures refer to mg 02/I. The position ofthe intake gates of the hydra-electric power station was almost completely in thehypolimnion zone. The water passing the turbines contained very lite or no oxygen& caused fish mortality & oxygen deficiency over a large distance downstream. World Bank-26020
- 17 -
FIGURE 5
Reconstruction of Oxygen Isopleths in a Length Profileof the Lake along the Former Suriname River
(rainy period)
Mamadam KoenkoenRa ids Rapids Grankreek Bedoti Kabelstation Afobaka
Depth 0 7
82
16-
txtes f / <~~~~~~.......
20:
24:FORMER SURINAME RIVER BED
28: - 1-5.111.1966-
32
36L --- ' ..:3:::: :.-...5 10 15 20 25 30 35 40 45 50 55 60 65 70
River Kilometers
Note: Reconstruction of oxygen Isopleths in a length proflle of the lake along the FORMERSURINAME RIVER, on 1-5.111.1966. Flgures refer to mg 02/1.
Source: Heide (1976) World Bank-26021
FIGURE 6
Temperature and Oxygen Content at Different Depths at Kabelstation, Suriname
1C temp. KABELSTATION 1964-1967
I ~~~Temperature & Oxygen Content at Dmferent Depths I
340 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~34
32- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~32
b 03
8.5~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~2
26 1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~26
1964 1965 1 1966 1967
omiIiII IV V 1\AlV\ll IX XXI XII I 1 III IV VV\AV\1VIII IX XXI XIII 111III IV VVIVmlllIIX XXI Xi I I IIIIIIV V °2 rng/1
10 I I 10
I 1 Saturation Point 8
5 0
Note: Sampling point kABELSTATION. Temperature & oxygen content at different depths during the whole
obse vatlon perlod, Feb. 1964-May 1967. The data are plotted at intervals of two weeks.
Source: Fbiede (1976) World Bank-26019
- 19 -
FIGURE 7
Water Densities for Various Temperatures
1. coooOO
0.99950 -. , 02
0. 900 00
0.99850 ' \
0.99800 . \
0.99750 -
a.99700 _
0.99B50 I \
0.99808 I I I \
o.sssso . ~~~~~~I I , .
0.99500 I
0.99S000 J 5 10 - 5 20 25 30 35
TEMPERATURE, OC
- 20 -
Hydrothermal analysis and wind driven circulation thus become
crucial aspects in predicting water quality changes. The former has been
studied longer and is easier to simulate (Harleman, 1982; Orlob, 1981).
Wind driven circulation, on the other hand, has not been as intensively
studied, because at least two dimensions (i.e., vertical and horizontal)
need to be simulated. This, presently, is a matter of active research
(Bloss, 1980; Johnson, 1980; Krenkel, 1982; Thompson, 1980). Water
quality models for stratified reservoirs could have several degrees of
complexity, depending on the number of parameters
simulated. Therefore, only key parameters, such as oxygen and phosphorus,
should be considered initially in this type of predictive model. 3/
The overall conclusion obtained from the above is that the
hypolimnion behaves like a stagnant body of water with practically one
source of oxygen--the advective underflows caused by the incoming rivers.
2.3 Oxygen Balance
In order to obtain order-of-magnitude estimations on the main
sources and sinks of dissolved oxygen, a simplified oxygen budget can be
derived. The reservoir, as it first fills, resembles a reactor with
varying input streams of river water and biodegradable organic matter
(i.e., the vegetation being flooded). Thus, the outcome of this process
can be easily predicted. An example of this calculation was done for the
Urra Hydroelectric Project in northwestern Colombia. From comparative
studies, a 30 ton/ha of readily biodegradable biomass was assumed. The
area flooded at successive 3-month intervals was obtained from the
3/ An example of this simplified approach is presented by Klomp (1980).Other examples that introduce different perspectives can be found in
Ford (1980), Gunnison and Branon (1980), Shanahan and Harleman (1982),Wang and Harleman (1982) and Wu and Alhert (1980).
- 21 -
project area-capacity curves and the most probable (based on mean monthly
flows) filling curve.
Figure 8 shows the predicted filling process. Area and volume in
this case correspond to organic matter and dilution water, respectively.
Figure 9 illustrates the great oxygen deficits originating from vegetation
decomposition. Table 3 shows the variation for each time period. The
second and fourth columns represent the oxygen inputs and demands for each
time period. For example, between the 3rd and the 6th month, approxi-
mately 240,000 tons of oxygen are required. This high value is due to the
large area flooded during this time span.
TABLE 3
Dissolved Oxygen Balance During The Filling Process(tons of oxygen)
MONTH INPUT TOTAL DEMAND TOTAL OXYGENADVECTED DEMANDED BALANCE
(1) (2) (3) (4) (5) (6)
3 9600 9600 90000 90000 -804006 30400 40000 240000 330000 -2900009 0 40000 0 330000 -29000012 20000 60000 120000 450000 -390000
15 32000 92000 123000 573000 -48100018 8000 100000 19500 592500 -49250021 12800 112800 43500 630000 -52320024 23200 136000 51000 687000 -55100027 25600 161600 34500 721500 -55990030 17600 179200 22500 744000 -564800
33 27200 206400 21000 765000 -55860036 13600 220000 21000 786000 -566000
The curve obtained in Figure 9 has only theoretical value. As
the conditions become anaerobic and the usual biochemical transformations
Figure 8RESERVOIR FILLING PROCESS
100 30
80 4, 2.5
60 2.06
Filling Time (Months
c
40 5
20 Dom ~4.et.I.1.0
0 0.50 6 12 18 24 30 36
Filling Time (Months)
World Bonk-25 123
- 23 -
FIGURE 9
Oxygen Consumption
° -tD Iu I I I . I I I I I I I I I I
xA YM G .20M
O EU NN -30000,
D T -4F 0
NS 1 -
. . . I I I Ila 20 30
- 24 -
take place, some of the products will become gaseous and rise into the
aerobic (superficial) strata. There, the gases will oxidize, or, in the
worst case, some will escape into the atmosphere. This process will,
therefore, satisfy a great part of the biochemical oxygen demand. The
rest will be broken down through the anaerobic pathways previously
mentioned. The transformation and product accumulation rates should be
more closely scrutinized in detailed water quality analysis.
2.4 Reservoir Recovery
Having made a prediction of the balance of oxygen during the
filling period, it would be useful to forecast the reservoir recovery
period. This depends on the former predictions. A few calculations
provide an order-of-magnitude estimation in order to gain some insight on
the general process. As an example, the concentration of a hypothetical
conservative substance was simulated for the Urra Project. This, in fact,
could be any substance that does not decay or decompose (e.g., sulfates,
chlorides, etc.). A perfectly mixed reservoir was assumed with a
residence time of 36 months. 4/ An arbitrary initial concentration of 100
units (e.g., mg./l) was considered (Figure 10). This simple calculation
showed that several years are required for complete renewal of the water
mass. Assuming "recovery" at 10% of the initial value, seven years would
4/ The mathematical formulation, in its simplest form, can be representedas follows:
C = Coe- (t/to) where CO : initial concentration (mg/l)
C : concentration at time t
to residence time (months or years)
e : base of natural logorithms
- 25 -
FIGURE 10
Reservoir Recovery Process
100
90
80
70
z0 60
o 50
40
30 I
20 -
a I 1 L I f I 1 2 3 4 5 6 7 8 9 10
YEARSWod Bank-26023
- 26 -
be required. This type of calculation is useful for elements such as
phosphorus--a limiting nutrient--in order to predict recovery through
successive eutrophication stages of the water mass. Additionally,
concentrations in the river inflows can be easily accounted for.
On a more detailed analysis, other factors, such as reservoir
morphometry, circulation patterns, withdrawal location (e.g., height of
penstock intake in the dam), soil characteristics and nutrient recycle
(water-to-sediment), would have to be considered.
3. RIVER WATER QUALITY PREDICTIONS
River pollution analysis has been developing for several decades
and there are many detailed publications on the subject. The main
objective of this section is to promote greater use both of this knowledge
and of the powerful analytical tools derived from it, in order to better
understand and predict the project impacts. Models, such as the QUAL-II
(EPA, 1981), will become very useful in the analysis of the downstream
effects. Figures 11 and 12 show selected results of the simulation
process, as it was applied to the Sinu River downstream from the Urra
Project (Dames and Moore, 1982). Due to the absence of important
tributaries along the river course, a rather smooth curve always
developed. Figure 13, by way of contrast, shows a clear discontinuity in
the dissolved oxygen profiles due to the confluence of a major tributary.
In all of the above examples, as would be expected, a constant improvement
in the oxygen level was observed.
The development and application of remedial measures, such as
biomass clearing, multi-level intakes and hypolimnetic reaeration, should
- 27 -
FIGURE 11
Dissolved Oxygen Profile of the Lower Rio Sinu(flow 400 m3/sec)
U.o
zO 4.0.COXYGEN DEFICIENrZONE
0
_~~~~Dg WR- 3.0 nV/ l /
- °- DOR - 2.0 motl
DOR - 1.0 nVtl/1
SOUflRAI ° rlIERlRALTJA °20motEvrERIA '50 SABANA 3SOKILOMJETERS NUEVA
Source: Dames and Moore 1982
- 28 -
FIGURE 12
Dissolved Oxygen Profile of the Lower Rio Sinu
(flow 50 m3/sec)
3.0 BOO5 - O.O "I
DD5 $15 MO"
6.0/
E
2a 4.0-
>1 OXYGEN DEFICIENrZONE0
2.0
URRA 1i 50 URRA I 100 TIERRALTA 150 20 MoNTERIA 250 SABANA 300 350KILOMETERS NUEVA
Source: Dames and Moore, 1982
- 29 -
FIGURE 13
Dissolved Oxygen Profileof a Hypothetical River
"NATURAL" LEVEL
130
155zLi I
0180
C ~~~~MINIMUM LEVEL
0~~~~~~~~~~~~~~~~~~~~~~~~~1
DAM SITE/ CONFWENCE (+ 80 m3/S)
DISTANCE (km)
Word Bank-26022
- 30 -
modify the profiles described above until adequate water quality is
obtained. The advantage of simulated predictions becomes evident if one
considers the possible combinations of remedial measures and the varying
cost-effectiveness values attained.
4. SUMMARY OF THE PROPOSED APPROACHES
The water quality studies presented in this paper should
preferably follow a staged development approach. The stages should
closely parallel traditional engineering studies conducted on a project.
This will facilitate the necessary data collection activities and allow
for close interaction with the project staff. The flow chart presented in
Figure 14 summarizes the different aspects that require consideration
under two successive levels of approximation in a detailed water quality
evaluation. The complexity of the task and the major effort required to
obtain the necessary data and develop the appropriate predictive models
are especially evident for the "design level" approach. This poses a
great challenge to those responsible for designing such projects in
tropical regions. The fact that most of them will be located in
developing nations calls for greater technology interchange and an
increased effort to understand both tropical ecosystems and societal goals.
- 31 -
FIGURE 14
Proposed Water Quality Considerations(two successive approaches)
A. FEASIBILITY LEVEL:
Stratification ConservativeSubstances SET AND REEVALUATE1 < T ~~~~~~~~~~~~~~~~~OBJECTIVES
Biodegradable Flooding Recovery Predi ctedFraction _ Process Process Downstream
S * _ ._ | a . _ ~~~~~~~~~~~~~~~~Effects
River Reservoir ixningWater 1Morphology .AssumptionsQuality
ANALYZE ALTERNATIVE PREVENTATIVE/MITIGATIVE MEASURES
B. DESIGN LEVEL:
Amount of Hydrothermal Main WaterVegetation Soi Behavior Quality SET AND REEVALUATE
.~~~~~~~~~ Constituents OBJECTIVES
_ Bidgradable | rFloodirng a Waer Quality | Rcovr I Pred cFraction & Process Constituents Process DownstreamNutrient Input -Balances- Discharges
River Circulation CirculationWater Quality Patterns atten
ANALYZE ALTERNATIVE PREVENTIVE/MITIGATIVE MEASURES
- 32 -
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Brady, N.C. 1974. The nature and properties of soils. New York,Macmillan. 639p.
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Fisher, H.B., et al. 1979. Mixing in inland and coastal waters. NewYork, Academic Press. 483p.
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- 33 -
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Wang, M. and Harleman, D.R.F., 1982. Hydrothermal-biological coupling oflake eutrophication models. Dept. of Civil Engineering, MIT, Cambridge,Mass., R.M. Parsons Laboratory. Technical Report No. 270, April, 245 p.
Wu, J.S. and Alhert, R.C. 1980. Mathematical modeling of impoundmentwater quality. Proceedings of the Symposium on Surface WaterImpoundments. New York, American Society of Civil Engineers (ASCE).June, 1679 p.
Woxid Bank The Johns Hopkins University Press, investment decisions, incomeWorld Batik 1966: 4th printing, 1974. 80 pages distribution, and distortions in the
Publications (including 2 appendixes). pricing system of the economy.
Of Related LC 66-28053. ISBN 0-8018-0646-1, The Johns Hlopkins University Press,$5.00 (13.00) paperback. 1977; 2nd printing, 1981. 382 pages
Interest (including tables, maps, index).
The Economics of Power LC 76-9031. ISBN 0-8018-1866-4,System Reliability and $30.00 (S.13.50) hardcover,Systemng R helibiiy anISse 1BN 0-8018-1867-2, $12.95 (45.75)
Studies pprakMohan Munasinghe French: L economie de l electricite:
essais et etudes die cas. Economica.A completely integrated treatment of 19e79system reliability. Indicates thatapplication of the reliability optimiza- ISBN 2-7178-0165-0, 58 francs.tion methodology could help realize . . .considerable savings in the electric Spanish: y!ectuicidad y economia:power sector, which is especially im- ensayos y estudios de casos. Editorialportant for developing countries with Tecnos. 1979.limited foreign exchange reserves. ISBN 84-309-0822-6, 710 pesetas.
The Johns Hopkins University Press,
Alcohol Production 1980. 344 pages (including tables, Electricity Pricing: Theoryfrom Biomass in the maps, index). and Case StudiesDeveloping Countries LC 79-2182. ISBN 0-8018-2276-9, Mohan Munasinghe andExplains the techniques for manufac- $27.50 (SI6.75) hardcover; Jeremy J. Warfordturing ethyl alcohol from biomass Ba -8018-2277-7. 12.50 (625) Describes the underlying theory andraw materials; analyzes the paperback. practical application of power-pricingeconomics of and prospects for pro- policies that maximize the netduction and government policies economic benefits to society ofneeded to accommodate conflicting NEW electricity consumption. Theneeds of various sectors of the methodology provides an expliciteconomy in promoting production; The Effect of Discount Rate framework for analyzing system costsand discusses the role the World and setting tariffs, and it allows theBank can play in assisting developing and Substitute Technolo tariff to be revised on a continualcountries in designing national on Depletion of Exhaustible basis. Case studies of electricity pric-alcohol programs. (One of three Resources ing exercises in Indonesia, Pakistan,publications dealing with renewable Yeganeh Hossein Farzin the Philippines, Sri Lanka, andenergy resources in developing coun- The succession of sharp price Thailand describe the application oftries. See Mobdizirng Renewab(e increases of oil in the early 1970s the methodology to real systems.Energy Techinolosgy in Dev)eloping icesso i nteerv17st elssescountries: Strengthening Local raised several issues related to com- The Johns Hopkins University Press.Capabitities and Research and a petition against OC as a supplier of 1982. 399 pages (including appendixes,Reaeabiltes anerg Resoarchs andth oil and competition against oil as a ine)Renewable Energy Resources in the form of energy. This paper considers index).Developing Countries.) the latter form of competition and LC 81-47613. ISBN 0-8018-2703-5,
September 1980. ix - 69 pages develops a model to analyze the $29.50 hardcover.(including 12 annex figures). validity of some basic propositions inFnglish, French, Spanish. and the economics of exhaustiblePortuguese. resources in the presence of NEW
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price of electricity to the marginal or the 1980s and it concludes that thereincremental cost of supply and dealswith interactions between pricing and
is a significant potential for additional World Bank Staff Working Paper No. Rural Electrificationmethanol capacity in developing 489. August 1981. uiii + 63 pages. Discusses the prospects for success-countries that possess low-cost gas fl investme rospectriricationresources, yet, in most cases, do not Stock No. WP-0489. $3.00. ful investment in rural electrificationhave an adequate supply of oil. Com- and considers implications for Worldplements the World Bank report, Bank policies and procedures.Alcohol Production from Biomass in India: The Energy Sector A Word Bank Paper. October 1975. 80the Developing Countries (September P D. Henderson pages (including annex). Englishr1980). Summary review of the sector, pro- French, and Spanish.April 1982. viii - 73 pages. viding technical, historical, and15BN 0-821300180 a73pages. statistical background information. Stock Nos.PP-7505-E.PP-7505-F.ISBIY 0-8213-0018-0. $5.00. OxodUiest rs,17.20PP-7505-S. $5.00.
Oxford University Press, 1975. 210pages (including map, 2 appendixes,
Energy in the Developing index). ~~~~~~~~~~~~~The Energy Transimon ini Developing Counrnes. justpubiished. details .vhv the Bank intends to commit
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Discusses the energy problem of the (i3.25; 1s30) hardcover. projects through 198e .1970s and the perspective for the the Deveeoptng Coi'trnes the last comprelhensivenext decade. States that by tapping World Bank report on the subiect. Since then thereserves of oil, gas, coal, and Mobilizing Renewable Bank has provided needea energy assistance inhydroelectric and forest resources Energy Technology in developing countries bv esxanding and di, ersify-ing its ener gy activities. The tnsights eained fromspreviously considered uneconomical Developing Countries: proects the Bank ihas financed form the basis for
and by vigorous conservation efforts, Strengthenintg Local the penetratinr ana!lvsis in th:s new report Thoseoil-importing countries could halve ho use the rePort -ill Drnf,t from the diversetheir oil-import bill by 1990. Outlines Capabilities and Research experience ot enerev specianists w%ho have neen
measures for saving energy without Focuses on the research required to 5ctive! invol\'eO ir iieid onerationsreducing economic growth and develop renewable energy resourcesexhorts industrialized and indus- in the developing countries and on REPRINYStrializing countries to adjust energy the need to strengthen the develop- Absorptive Capacity, the Demand forprices, incentives, and investments ing countries' own technological Revenue, and the Supply of Petroleumto emphasize domestic production. capabilities for using renewable Salah El SerafyProposes a World Bank program for energy. (One of three publicationsenergy lending and explains the dealing with renewable energy World Bank Reprint 5eries: Nlumber 213.energy lending ~~~~~~~~~~~~~~~~~~~Reprinted from The Journal of Energy andoperational aspects of the program. resources and issues in developing Development, vol. 7. no. 1 (Autumn 1981/: 73-88.
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Stock No. WP-0350. S5.00. renewable resources can make to World Bank Reprint Series: Number 201.energy supplies in developing coun- Reprinted from Energy Economics, vol. . no. 3tries and discusses the role of the (July 1981):140-52.
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Prepayment on orders from individuals is requested. Purchase orders are accepted from booksellers, library suppliers, libraries, and institutions.All prices include cost of postage by the least expensive means. The prices and publication dates quoted in this Catalog are subject to changewithout notice.
No refunds will be given for items that cannot be filled. Credit will be applied towards future orders.No more than two free publications will be provided without charge. Requests for additional copies will be filled at a charge of US $1.00 per
copy to cover handling and postage costs.Airmail delivery will require a prepayment of US $2.00 per copy.Mail-order payment to the World Bank need not be in U.S. dollars, but the amount remitted must be at the rate of exchange on the day the
order is placed. The World Bank will also accept Unesco coupons.
*** TD 326.5 .G37 1984 C.2
GARZON, CAMILO E., 1948-
WATER QUALITY INHYDROELECTRIC PROJECTS
1T326.5.G371984C.2
The World Bank
Headquarters European Office Tokyo Office U1818 H Street, N.W. 66, avenue d'lena Kokusai BuildingWashington, D.C. 20433, U.S.A. 75116 Paris, France 1-1 Marunouchi 3-chomeTelephone: (202) 477-1234 Telephone: (1) 723-54.21 Chiyoda-ku, Tokyo 100, JapanTelex: WUI 64145 WORLDBANK Telex: 842-620628 Telephone: (03) 214-5001
RCA 248423 WORLDBK Telex: 781-26838Cable Address: INTBAFRAD
WASHINGTONDC
ISSN 0253-7494Covcr design by Bill Fraser ISBN 0-8213-0363-5
