Lake Mcilwaine: The Eutrophication and Recovery of a Tropical African Man-Made Lake

257 Pages·1982·10.21 MB·English

by  N. A. Burke, J. A. Thornton (auth.), Jeffrey A. Thornton, W. K. Nduku (eds.)

LAKE McILW AINE
MONOGRAPHIAE
BIOLOGICAE
VOLUME 49
Editor
J.ILLIES
Schlitz, F.R.G.
Dr W. Junk Publishers The Hague-Baston-London 1982
LAKE McIL WA INE
The Eutrophication and Recovery
of a Tropical African Man-Made Lake
Edited by
J. A. THORNTON
With the assistance of
W.K.NDUKU
Dr W. Junk Publishers The Hague-Baston-London 1982
Distributors:
for the United States and Canada
Kluwer Boston, Inc.
190 Old Derby Street
Hingham, MA 02043
USA
for all other countries
Kluwer Academic Publishers Group
Distribution Center
P.O. Box 322
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The Netherlands
Library of Congress Cataloging in Publication Data CIP
Main entry under title:
Lake McIlwaine : th e eutroPhication and recovery of
a tropical African man-made lake,
(Monographiae hiologicae ; v. 49)
Bibliography / by Margaret J. Thornton &
J.A. Thornton
Includes indexes.
l. Eutrophication--Zimbabwe--McIlwaine, Lake .
2. Limnology--Zimbabwe --McIlwaine, Lake.
3. Water quality management--Zimbabwe--McIlwaine,
Lake. 4. McIlwaine, Lake (Zimbabwe) I. Thornton,
J. A. (Jeffrey A.) II. Series.
QPl.P57 vol. 49 [QHl95.Z55] 574s 82 -l5238
[363 .7'394'09689 l] AACR2
ISBN-13: 978-94-009-7985-7 e-ISBN-13: 978-94-009-7983-3
DOl: 10.1007/978-94-009-7983-3
Cover design: Max Velthuijs
Copyright © 1982 by Dr W. Junk Publishers, The Hague.
Soflcover reprint oft he hardcover Js t edition J 982
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,
or transmitted in any form by any means, mechanical, photocopying, recording, or otherwise,
without the prior written permission oft he publishers,
Dr W. Junk Publishers, P.O. Box 13713, 2501 ES The Hague , The Netherlands.
Preface
'And God said, Let there be a firmament in the
midst of the waters, and let it divide the waters
from the waters. '
Genesis 1:6
Lake McIlwaine is a man-made lake. It was formed in 1952 by the Hunyani-
poort Dam and is situated on the Hunyani River some 37 km southwest of
Salisbury* in the Republic of Zimbabwe**. It is a lake of many aspects: being
a popular recreational site, the City's primary water supply reservoir (and the
fourth largest impoundment in Zimbabwe), a source of irrigation water to
downstream farms, an important fishery, and, until the 1970s, the receptacle
of Salisbury's sewage effluent. It is, in short, typical of so many 'urban' lakes
in Africa and throughout the world. Lake McIlwaine is also unique, to my
knowledge: being amongst the first of the major man-made lakes on the
continent to suffer from what is known as cultural eutrophication, and the
first to be r:ehabilitated to a mesotrophic state through a rational programme
of lake management. This volume synthesizes this process of eutrophication
and recovery in terms of the geology and geography (Chapter 2), physics
(Chapter 3), chemistry (Chapter 4) and biology (Chapter 5) of the lake, and,
whilst discussion of the trophic relationships between these components is
beyond the scope of this monograph, discusses its utilisation, conservation
and management (Chapter 6).
* Subsequent to writing, the name of the Zimbabwean capital was changed to Harare on 18
April 1982. - Ed.
** The Colony of Southern Rhodesia was granted independence by H. M. Government on 18
April 1980 and became the Republic of Zimbabwe. All names used in this monograph are those
currently in use at the time of writing.
VII
The recovery of Lake McIlwaine was effected through the efforts and
foresight of a large numer of individuals: in Government, in the University, in
commerce and industry, and in the general pUblic. Their efforts formulated
the principles, policies and legislation and, more importantly, implemented
these same which resulted in the recovery of the lake. Some of these people
have now recorded the roles played by their colleagues and themselves in this
endeavour, and my sincere thanks, as editor, go out to them, collectively and
individually, for without their expertise this monograph would not have been
possible.
Acknowledgement must also be made to the Government of Zimbabwe,
particularly to the Ministry of Natural Resources and Water Development; to
the City of Salisbury; and to the University of Zimbabwe, who generously
funded large portions of the research programmes; and to Lever Brothers
(Pvt.) Ltd. and Mobil Oil Zimbabwe (Pvt.) Ltd. and others who equally
generously provided monies for various necessary items of equipment. I am
grateful for the co-operation and assistance of my colleagues and friends at
the University of Zimbabwe, in the Department of National Parks and Wild
Life Management, in the Division of Water Development, and latterly in the
Hartbeespoort Dam Ecosystem Programme team of the National Institute for
Water Research, CSIR, whose advice and encouragement resulted in the
completion of this volume.
As editor, I have had to co-ordinate the various sections of this monograph
which were written by a number of independent authors and co-authors, and
in some instances considerable adjustment was necessary to bring these
contributions into line with the general plan ofthe volume. Should any errors
or omissions have occurred during this process, I tender my sincere apo-
logies.
This volume forms contribution No.4 to the National Water Quality
Survey of Zimbabwe.
Pretoria, December 1981 JEFFREY A. THORNTON
VIII
Contents
Preface VII
Addresses of authors XI
1. Introduction
The creation of Lake McIlwaine: history and design, by N. A. Burke
and J. A. Thornton
2. Geology and geography
Land use survey of the Upper Hunyani catchment, by K. Munzwa 11
3. Physics
Physical limnology , by P. R. B. Ward 23
The hydrology of the Lake McIlwaine catchment, by B. R. Ballinger
and J. A. Thornton 34
4. Chemistry
Water chemistry and nutrient budgets, by J. A. Thornton and
W. K. Nduku 43
The sediments, by R. Chikwanha, W. K. Nduku and J. A. Thornton 59
- Sediment chemistry, by J. A. Thornton and W. K. Nduku 59
- Sediment transport, by R. Chikwanha 66
The effects of urban run-off, by R. S. Hatherly, W. K. Nduku,
J. A. Thornton and K. A. Viewing 71
- The aqueous phase: nutrients in run-off from small catchments,
by J. A. Thornton and W. K. Nduku 71
- The solid phase: a study of pollution benchmarks on a granitic
terrain, by R. S. Hatherly and K. A. Viewing 77
Insecticides in Lake McIlwaine, Zimbabwe, by Yvonne A. Greichus 94
IX
5. Biology
An SEM study of bacteria and zooplankton food sources in Lake
McIlwaine, by Monika Boye-Chisholm and R. D. Robarts 101
Phytoplankton, primary production and nutrient limitation. by
R. D. Robarts, J. A. Thornton and Colleen J. Watts 106
- The algal community, by J. A. Thornton 106
- Primary production of Lake McIlwaine, by R. D. Robarts 110
- An examination of phytoplankton nutrient limitation in Lake
McIlwaine and the Hunyani River system, by Colleen J. Watts 117
Zooplankton and secondary production, by J. A. Thornton and
Helen J. Taussig 133
Aquatic macrophytes and Eichhornia crassipes, by M. J. F. Jarvis,
D. S. Mitchell and J. A. Thornton 137
The benthic fauna of Lake McIlwaine, by B. E. Marshall 144
The fish of Lake McIlwaine, by B. E. Marshall 156
Avifauna of Lake McIlwaine, by M. J. F. Jarvis 188
6. Utilisation, management and conservation
Water pollution: perspectives and control, by D. B. Rowe 195
Water supply and sewage treatment in relation to water quality in
Lake McIlwaine, by J. McKendrick 202
Fisheries, by K. L. Cochrane 217
Recreation, by G. F. T. Child and J. A. Thornton 221
Research: perspectives, by J. A. Thornton 227
7. Bibliography
by Margaret J. Thornton and J. A. Thornton 233
Taxonomic index 241
General index 245
x
Addresses of authors
B. R. Ballinger, Hydrological Branch, Division of Water Development,
Ministry of Natural Resources and Water Development, Private Bag 7712,
Causeway, Salisbury, Zimbabwe.
Monika Boye-Chisholm, 13 Glebe End, nr. Bishops Stortford, Herts., UK
(previously: Hydrobiology Research Unit, University of Zimbabwe.
N. A. Burke, Designs Branch, Division of Water Development, Ministry of
Natural Resources and Water Development, Private Bag 7712, Causeway,
Salisbury, Zimbabwe.
R. Chikwanha, Hydrological Branch, Division of Water Development,
Ministry of Natural Resources and Water Development, Private Bag 7712,
Causeway, Salisbury, Zimbabwe.
G. F. T. Child, Director, Department of National Parks and Wild Life
Management, P. O. Box 8365, Causeway, Salisbury, Zimbabwe.
K. L. Cochrane, Limnology Division, National Institute for Water Research,
CSIR, P.O. Box 395, Pretoria 0001, Republic of South Africa (previously:
. Lake Kariba Fisheries Research Institute, Department of National Parks
and Wild Life Management, Zimbabwe).
Yvonne A. Greichus, Enviro Control Inc., 11300 Rockville Pike, Rockville,
MD 20852, USA.
R. S. Hatheriy, c/o Institute of Mining Research, University of Zimbabwe,
P.O. Box MP.167, Mount Pleasant, Salisbury, Zimbabwe.
M. J. F. Jarvis, Branch of Terrestrial Ecology, Department of National Parks
and Wild Life Management, P.O. Box 8365, Causeway, Salisbury,
Zimbabwe.
B. E. Marshall, Lake Kariba Fisheries Research Institute, Department of
National Parks and Wild Life Management, P.O. Box 75, Kariba,
Zimbabwe.
XI