Hydraulic modelling of the Lower Orange River (Republic of South Africa) and evaluation of integrated water resources management in the Orange-Senqu-Fish catchment

Jan Putteman Bert Schepens
 Jan Putteman en Bert Schepens
Duurzaam waterbeheer in Zuid-Afrika: de Oranjerivier bekent kleur
“Let there be work, bread, water and salt for all”, deze wijze woorden sprak Nelson Mandela bij zijn inauguratie in 1994. De verwezenlijking van dit droombeeld blijkt echter minder eenvoudig te zijn, althans voor wat de beschikbaarheid van water betreft. In een land waar water een schaars goed is en de behoeften nog steeds toenemen zal enkel een weldoordacht waterbeheer enig soelaas kunnen bieden.

Hydraulic modelling of the Lower Orange River (Republic of South Africa) and evaluation of integrated water resources management in the Orange-Senqu-Fish catchment

 Jan Putteman en Bert Schepens

Duurzaam waterbeheer in Zuid-Afrika: de Oranjerivier bekent kleur

“Let there be work, bread, water and salt for all”, deze wijze woorden sprak Nelson Mandela bij zijn inauguratie in 1994. De verwezenlijking van dit droombeeld blijkt echter minder eenvoudig te zijn, althans voor wat de beschikbaarheid van water betreft. In een land waar water een schaars goed is en de behoeften nog steeds toenemen zal enkel een weldoordacht waterbeheer enig soelaas kunnen bieden. Of hoe ingenieurswetenschappen, ecologie en ethiek meer dan ooit complementair zijn.

Begin september 2009 vertrokken Jan Putteman en Bert Schepens, allebei student burgerlijk ingenieur bouwkunde, voor een maand richting Zuid-Afrika. Het doel van deze reis was het vergaren van informatie in verband met de plaatselijke waterproblematiek, waarbij hoofdzakelijk het Oranjerivierbekken werd bestudeerd. Tijdens dit bezoek werd voornamelijk gepraat met de lokale bevolking, officiële instanties en de verschillende stakeholders, om zo een gefundeerd en genuanceerd beeld te krijgen van de belangrijkste pijnpunten. Ook werd voldoende data (geometrie van de rivier, debiet, ...) verzameld, met de bedoeling later een computermodel van de rivierstroming op te bouwen.

De Oranjerivier ontspringt in het hooggebergte van Lesotho en kronkelt vervolgens doorheen de Kalahari halfwoestijn. De rivier tekent zich af als een groene lijn in een onherbergzaam landschap, en mondt uiteindelijk uit in de Atlantische oceaan. Het rivierbekken beslaat bijna 50 % van de totale oppervlakte van Zuid-Afrika. Zonder het water van de Oranjerivier zou de nationale economie slechts een schim zijn van wat ze nu is. De Oranjerivier creëert werkgelegenheid in deze desolate streek. Een rit langs de rivier illustreert al snel het belang van irrigatieprojecten, bijvoorbeeld voor het verbouwen van druiven, die tevens een belangrijk exportproduct vormen.

Maar de Oranjerivier is wispelturig ... Zo verwoestend de zondvloed tijdens de zomermaanden, zo behoedzaam stroomt het water in de winter. Teneinde de watervoorziening op elk moment te verzekeren werden daarom sinds de zeventiger jaren verschillende dammen en stuwen op de rivier gebouwd. Het reservoir van een stuwdam wordt gedurende de zomermaanden opgevuld, terwijl dit gestockeerd water tijdens de wintermaanden gebruikt wordt om het watertekort te compenseren. Een netwerk van irrigatiekanalen verdeelt het water over de vruchtbare gronden langsheen de rivier.

De weelde van de Oranjerivier staat in schril contrast met het gebrek aan water elders in het land.  Daarom wordt de laatste decennia druk gewerkt aan zogenaamde inter-basin transfers. Men transporteert het rivierwater dus naar een ander rivierbekken waar het in natuurlijke omstandigheden onmogelijk terecht zou kunnen komen. Zo versast een ingenieus netwerk van kanalen, tunnels en dammen water van de Oranjerivier naar de zuidkust van Zuid-Afrika, zo’n 350 km verder. Op dezelfde manier wordt ook het industriële hart van Zuid-Afrika, dit is de regio Johannesburg-Pretoria, van bijkomend drinkwater voorzien.

De vele bouwkundige ingrepen die recent plaatsvonden in en langs de Oranjerivier hebben ertoe geleid dat de rivier geëvolueerd is naar een gereguleerd systeem. Door analyse van debietmetingen sinds de jaren ’30 kunnen we exact nagaan wat precies de impact van de mens op het stromingsregime in de rivier is. Het jaarlijks opgemeten watervolume is meer dan gehalveerd in vergelijking met de periode voorafgaand aan de constructie van verschillende stuwdammen. Maar er is meer aan de hand. Ook de seizoenale variatie van de getransporteerde watervolumes is sterk gewijzigd. Door debietregeling met behulp van stuwdammen kan men immers een constant debiet in stand houden. Dit constant debiet is een gevolg van de vrij constante waterbehoeften van de afwaartse watergebruikers.

De impact van stuwdammen en irrigatieschema’s gaat veel verder dan louter hun fysieke aanwezigheid: het resulterende gewijzigde stromingsregime heeft een grote impact op het aquatisch ecosysteem aangezien er nieuwe leefomstandigheden gecreëerd worden. Zo kampt men momenteel met een plaag van ‘black flies’. Dit zijn kleine vliegjes die door de mildere stromingsomstandigheden veel makkelijker kunnen overleven en bijgevolg in onnatuurlijk hoge aantallen voorkomen. Ook verkeert de monding van de Oranjerivier, tevens van internationaal belang voor trekvogels, in zeer slechte staat. De belangrijkste herstelmaatregel bestaat uit het creëren van een meer natuurlijk en seizoensgebonden stromingsregime, waarbij een hoog zomerdebiet wordt afgewisseld door een laag winterdebiet.

Ontwikkeling, gelijkheid en natuurbehoud: drie mooie begrippen die in de geschiedenisboeken niet blijken samen te gaan. Het nieuwe Zuid-Afrika is niettemin ambitieus: de National Water Act wil water én de hiermee gerelateerde ecosystemen teruggeven aan de gehele bevolking. De gelijke toegang tot drinkbaar water vormt een belangrijke stap in de richting van de verhoging van de levensstandaard van de zwarte bevolking, denk maar aan het gebruik van water voor sanitair, irrigatieprojecten en industrie. Anderzijds groeit het besef dat het beschikbare water eindig is, en dat overexploitatie drastische gevolgen zal hebben voor het leefmilieu.

Net bij het maken van een compromis tussen deze verschillende belangen kan de technologie een handje helpen. In het kader van deze studie werd, vertrekkend van een bestaand softwarepakket, een hydraulisch model van de Oranjerivier opgebouwd. Een hydraulisch model wordt gebruikt om de voortplanting van een bepaald debiet doorheen de rivier te simuleren. Een debietgolf die ter hoogte van een stuwdam in de rivier wordt gestuurd heeft immers een zekere tijd nodig om tot bij een bepaalde watergebruiker te stromen. Zo is bijvoorbeeld een maand tijd nodig voor het overbruggen van een afstand van 1400 km. De mogelijkheid tot het correct voorspellen van het debiet in de rivier laat toe om duurzame beheersmaatregelen voor de stuwdammen voor te stellen. Door gebruik van een hydraulisch model kan men er immers over waken dat belangrijke ecosysteemcomponenten, zoals de riviermonding, op elk tijdstip een optimaal debiet ontvangen.

Momenteel is er reeds een prangend watertekort. Niettemin stelt men een economische groei voorop. Een hopeloze zaak lijkt het. Hebben de huidige gezagsdragers voldoende daadkracht om het tij te keren? De technologische knowhow laat toe om elke druppel water zo efficiënt mogelijk te benutten, maar de mate waarin prioriteit wordt gegeven aan ecosysteembehoeften wordt door politieke beslissingen gestuurd. Zal er nog heel wat water naar zee moeten vloeien alvorens men de kaart van de duurzaamheid trekt, of net niet?

Bibliografie

 [1] Orange-Senqu River awareness kit. http://www.orangesenqurak.org.

[2] R.S. McKenzie and A.R. Craig. Evaporation losses from South African rivers. WRC Report No 638/1/99, 1999.

[3] H.G. Maré, L.C. Hattingh, and W. Kamish. Pre-feasibility study into measures to improve the management of the Lower Orange River and to provide for future developments along the border between Namibia and South Africa: Hydrology, water quality and system analysis Volume A. DWAF Report No PB D000/00/4303, 2005.

[4] A. Jeleni and H.G. Maré. Review of existing infrastructure in the Orange River catchment. ORASECOM, 2007.

[5] DWA: Overview of the Lesotho Highlands Project. http://www.dwaf.gov.za/ orange/Up_Orange/lhwpover.htm.

[6] Lesotho Highlands Water Project. http://www.lhwp.org.ls.

[7] R.N. Seemel. Contracts awarded for the Lesotho Highlands scheme. Water Power & Dam Construction, 43(3): 30-33, 1991.

[8] Anon. Lesotho Highlands scheme: construction begins. Water Power & Dam Con­struction, 41(5): 48-52, 1989.

[9] R.S. McKenzie. Yield analysis up to PK le Roux Dam. BKS Inc., 1993.

[10] DWA: The Orange River catchment. http://www.dwaf.gov.za/Orange/.

[11] Orange River Scheme -Gariep and Vanderkloof power stations. http://www.eskom. co.za/.

[12] E. Steÿn. Choice of sites for two proposed gauging weirs in the Vaal and the Orange rivers.

[13] Blue Science Consulting. http://www.bluescience.co.za.

[14] Department of Water Affairs. http://www.dwa.gov.za/Projects/WARMS.

[15] J. de la Harpe and P. Ramsden. Guide to the National Water Act. Department of Water Affairs and Forestry, 1998.

[16] Acts online -South African hypertext legislation. http://www.acts.co.za/ntl_ water.

[17] J.S. Hallowes, A.J. Pott, and M. Döckel. Managing water scarcity to encourage sustainable economic growth and social development in South Africa. International Journal of Water Resources Development, 24(3):357–369, 2008.

[18] R. McKenzie and P. van Rooyen. Water Resources Yield Model user guide. Water resources system analysis. BKS, 1999.

[19] Department of Water Affairs. National water resources strategy,1st edition, 2004.

[20] A.T. Haines, B.L. Finlayson, and T.A. McMahon. A global classification of river regimes, chapter Applied geography, pages 255–272. Department of Civil and Agri­cultural Engineering, University of Melbourne (Australia), 1988.

[21] F.H.S. Chiew, J.A. Dracup, T.A. McMahon, and T.C. Piechota. Seasonal stream flow forecasting in eastern Australia and the El Niño-southern oscillation. 24th Hy­drological and Water Resources Symposium Proceedings -New Zealand Hydrological Society, Auckland (New Zealand), 1997.

[22] R.D. Burman, P.R. Nixon, J.L. Wright, and W.O. Pruitt. Water requirements. In

M.E. Jensen, editor, Design and operation farm irrigation systems. American Society of Agricultural Engineers, 1981.

[23] R.L. Marlow. Agriculture water use efficiency in the United States. US/China Wa­ter Resources Management Conference -Los Alamos National Laboratory, Tucson, Arizona (US), 1999.

[24] A. Keller, J. Keller, and D. Seckler. Integrated water resources systems: Theory and policy implications. IIMI research report 3. International Irrigation Management Institute, 1996.

[25] D. Seckler. The new era of water resources management from ‘dry’ to ‘wet’ water

savings. IIMI research report 5. International Irrigation Management Institute, 1996.

[26] T.A. Howell. Enhancing water use efficiency in irrigated agriculture. Agronomy Journal, 93:281–289, 2001.

[27] X. Cai, M.W. Rosegrant, and C. Ringler. Physical and economical efficiency of water use in the river basin: Implications for efficient water management. Water Resources Research, 39(1):1013, 2003.

[28] L.S. Willardson, R.G. Allen, and H.D. Frederiksen. Universal fractions for the elim­ination of irrigation efficiency. 13th Technical Conference of the United States Com­mittee on Irrigation and Drainage, 1994.

[29] R.G. Allen and L.S. Willardson. Water use definitions and their use for assessing the impacts of water conversation. In J.M. de Jager, L.P. Vermes, and R. Ragab, editors, Sustainable irrigation in areas of water scarcity and drought. Proceedings of the International Commission on Irrigation and Drainage Workshop, 1997.

[30] C.W. Howe. The return to the river basin: The increasing costs of ‘jurisdictional externalities’. Journal of Contemporary Water Research and Education, 131:26–32, 1994.

[31] D. Seckler, D.J. Molden, and R. Sakthivadivel. The concept of efficiency in water resources management and policy. In J.W. Kijne, R. Barker, and D. Molden, edi­tors, Water productivity in agriculture, limits and opportunities. CAB International, Wallingford (UK), 2002.

[32] J.A. Döckel. The possibility of trade in water use entitlements in South Africa under the National Water Act of 1998. In S. Perret, S. Farolfi, and R. Hassan, editors, Water governance of sustainable development: Approaches and lessons from developing and transitional countries. Earthscan, London (UK), 2006.

[33] National Research Council. Water transfers: Efficiency, equity and environment, 1992.

[34] J.C. Neuman. Beneficial use, waste and forfeiture: The inefficient search for efficiency in western water use. Environmental Law, 28:919, 1998.

[35] J. Berbel and J.A. Gomez-Limon. The impact of water pricing in Spain: An analysis of three irrigated areas. Agricultural Water Management, 43:219–238, 2000.

[36] C. De Fraiture and C. Perry. Why is irrigation water demand inelastic at low price

ranges? Conference sur les Politiques d'Irrigation, Considerations Micro et Macro Economiques -Morroco, 2002.

[37] Organisation for Economic Cooperation and Development. Transition to full-cost pricing of irrigation water for agriculture in OECD countries. Report No. JT00121195, 2002.

[38] A. Massarutto. Water pricing and irrigation water demand: Economic efficiency versus environmental sustainability. European Environment, 13:100–119, 2003.

[39] G.M. Banzanni, S. Di Pasquale, V. Gallerani, and D. Viaggi. Irrigated agriculture in Italy under the European Union Water Framework Directive 0043-1397. Water Resources Research, 40:1–8, 2004.

[40] K. Schoengold, D. Sunding, and G. Moreno. Panel estimation of an agricultural water demand function. University of California Berkley (US), 2005.

[41] S. Cheung. The structure of a contract and the theory of non-exclusive resources. Journal of Law and Economics, 13:49–70, 1970.

[42] A. Randell. Resource economics: An economic approach to natural resources and the environmental policy. Grid Press, Columbus, Ohio (US), 1981.

[43] J. Patterson. Rationalised law and well-defined water rights for improved water resources management. In Renewable Natural Resources Economic Incentives for Improved Management, pages 43–64. Organisation for Economic Cooperation and Development, 1991.

[44] C.W. Howe and J.D. Wiener. Moving towards more efficient markets: institutional barriers and innovations. Proceedings UCOWR/NIWR Annual Conference, Increas­ing Freshwater Supplies, Santa Fe, New Mexico -Carbondale, Southern Illinois Uni­versity (US), 2006.

[45] Conningarth Economists. The facilitation of trade in water use entitlements by the National Water Act in South Africa. WRC Report No. 1297/1/04. Water Research Commission, 2004.

[46] A.J. Pott, J.S. Hallowes, S.S. Mtshali, S. Mbokazi, M. van Rooyen, A. Clulow, and

C. Everson. The development of a computerised system for auditing real time or

historical water use from large reservoirs in Order to promote the efficiency of water

use. WRC Report No. 1300/1/05. Water Research Commission, 2005.

[47] M.F. Viljoen, N.J. Dudley, E.F.Y. Gakpo, and J.M. Mahlaha. Effective local man­agement of water resources with reference to the Middle Orange River. WRC Report No. 1134/1/04. Water Research Commission, 2004.

[48] W.L. Nieuwoudt and R.M. Armitage. Water market transfers in South Africa: Two case studies. Water Resources Research, 40, 2004. University of KwaZulu-Natal, Pietermaritzburg.

[49] R.M. Armitage, W.L. Nieuwoudt, and G.R. Backeberg. Establishing tradable water rights: Case studies of two irrigation districts in South Africa. Water SA, 25(3), 1999. University of KwaZulu-Natal, Pietermaritzburg.

[50] C.G. Gillett and W.L. Nieuwoudt. Private water markets in the Lower Orange River catchment of South Africa. University of KwaZulu-Natal, Pietermaritzburg, 2004.

[51] R.M. Armitage. An economic analysis of surface irrigation water rights transfers in selected areas of South Africa. WRC Report No. 870/1/99. Water Research Com­mission, 1999.

[52] R.G. Huffaker and N.K. Whittlesey. Agricultural water conservation legislation: Will it save water? Choises, 4:24–27, 1999.

[53] C.B. Pedersen, H. Madsen, and C. Skotner. Real time optimization of dam releases using multiple objectives. Application to the Orange-Fish-Sundays River basin. In­ternational Journal on Hydropower and Dams, 14(6):74–78, 2007.

[54] K.R. Greaves, J.S. Hallowes, S. Mtshali, B. Mwake, and R. Cai. Progress towards the development of a real time decision support system (DSS) for the Mhlathuze River catchment. In Proceedings SANCIAHS 2007. South African National Hydrology Symposia, 2007.

[55] R. Heath and C. Brown. Environmental considerations pertaining to the Orange River. ORASECOM, 2007.

[56] C. Dickens, M. Graham, G. de Winnaar, K. Hodgson, F. Tiba, R. Sekwele et al. The impacts of high winter flow releases from an impoundment on in-stream ecological processes. WRC Report No. 1307/1/08, 2008.

[57] B.P. Han, J. Armengol, J.C. Garcia, M. Comerma, M. Roura, J. Dolz et al. The

thermal structure of Sau Reservoir (NE Spain): a simulation approach. Elsevier Eco­logical Modelling, 2000.

[58] D. Chapman. Water quality assessments: a guide to the use of biota, sediments and water in environmental monitoring. Chapman and Hall, London, 1992.

[59] G. Tchobanoglous and E.D. Schroeder. Water Quality. Addison-Wesley Publishers Company, Massachussets, USA, 1985.

[60] R.J. Pitchford and P.S. Visser. The effect of large dams on river water temperature below the dams, with special reference to Bilharzia and the Verwoerd Dam. South African Journal of Science 71:212-213, 1975.

[61] B.R. Allanson and P.B.N. Jackson. The limnology and fisheries potential of Lake le Roux. South African National Scientific Programmes Report No 77., CSIR, Pretoria, 1983.

[62] R.W. Palmer. Invertebrates in the Orange River, with emphasis on conservation and management. South African Journal of Aquatic Science, 1996.

[63] C. Carron and H. Rajaram. Impact of variable reservoir releases on management of downstream water temperatures. Water Resources Research 37(6), 2001.

[64] K. Schmidt-Nielsen. Animal physiology-adaptation and environment. Cambridge University Press, 1995.

[65] G. de Wet. B.Sc (Hons) thesis. Department of Botany & Genetics, UOFS, Bloem­fontein, 1998.

[66] D.F. Hayes, J.W. Labadie, T.G. Sanders, and J.K. Brown. Enhancing water quality in hydropower system operations. Water Resources Research 34(3), 1998.

[67] S.W. Trimble. Encyclopedia of water science. CRC Press, 2008.

[68] J.M. Bremner, J. Rogers, and J.P. Willis. Sedimentological aspects of the 1988 Orange River floods. Transactions of the Royal Society of South Africa, 1990.

[69] C. Benade. Studies on fish populations in the regulated Orange River system within the borders of the Cape Province, M.Sc thesis. Faculty of Natural Sciences, Depart­ment of Zoology and Entomology, UOFS, Bloemfontein, 1993.

[70] C.A. Brown. Pre-feasibility study into measures to improve the management of the

Lower Orange River and to provide for future developments along the border between Namibia and South Africa: specialist report on the environmental flow requirements -riverine. Permanent Water Commission, 2005.

[71] D.M. Lehmkuhl. Change in the thermal regime as a cause of reduction of benthic fauna downstream of a reservoir. Journal of the Fisheries Research Board of Canada, 1972.

[72] P. de Villiers and M.T. Seaman. A general assessment of the in-stream requirements of the fish species in the Upper Orange River.

[73] J.A. Cambray. Fish populations in the Middle and Lower Orange River, with special reference to the effects of stream regulation. Limnological Society of South Africa, 1984.

[74] N.D. Impson, I.R. Bills, and L. Wolhuter. Technical report on the state of Yellowfishes in South Africa 2007. WRC Report No. KV 212/08, 2008.

[75] Adventure fly fishing. http://adventureflyfishing.co.za/.

[76] M.L. Hunter. Fundaments of conservation biology. Blackwell Science, USA, 1996.

[77] S. Taljaard. Pre-feasibility study into measures to improve the management of the Lower Orange River and to provide for future developments along the border between Namibia and South Africa: specialist report on the determination of the prelimi­nary ecological reserve on a rapid level for Orange River estuary. Permanent Water Commission, 2005.

[78] F.M. Chutter. Instream flow assessment of the Orange River and its tributaries: from the Lesotho border at Oranjedraai to Gariep Dam: aquatic invertebrates and their habitat requirements. AfriDev Consultants, 1997.

[79] Los Angeles County West Vector & Vector-Borne Disease Control District. http: //www.lawestvector.org/black_flies.htm.

[80] R. van Diesfeldt. Rubriek beestjes -De buffelvlieg. http://rvd501.web-log.nl/ rvd501/rubriek_beestjes.

[81] BugGuide.Net. http://bugguide.net/node/view/16613/bgimage.

[82] E. Myburgh. Factors that influence adult blackfly (Diptera: Simuliidae) survival

along the Orange River, South Africa. WRC report No. 1019/1/03. Water Research Commission, 2003.

[83] E.M. Nevill. The creation of permanent blackfly problems by the construction of sams. In I.A.W. MacDonald and R.J.M. Crawford, editors, Long-term data series relating to South Africa's renewable natural resources. South African National Sci­entific Programmes -Report No. 157, pages 353–355. CSIR, 1988.

[84] C.J. Howell and G.W. Holmes. The control of Simuliidae in the Vaalharts Irrigation Complex. Journal of the South African Veterinary Association, 40:59–67, 1969.

[85] M. Car. The influence of water-level fluctuation on the drift of Simulium chutteri Lewis 1965 (Diptera: Nematocera) in the Orange River, South Africa. Onderstepoort Journal of Veterinary Research, 50:173–177, 1983.

[86] Saskatchewan aquatic Diptera. http://www.aquatax.ca/miscdip.html.

[87] F.M. Chutter. Hydrobiological studies on the Vaal River in the Vereeniging area, volume 21, chapter Water Chemistry and Biological Studies on the Fauna of Habitats Other than Muddy Bottom Sediments, pages 1–65. Hydrobiologica, 1963.

[88] R.W. Palmer. Ecological effects of impoundments in the Buffalo River, Eastern Cape, with particular reference to the distribution of blackflies (Diptera: Simuliidae). Ph. d. thesis, Rhodes University, 1991.

 

[89] E. Myburgh. Control of blackflies in South Africa. Final report on the control of blackfly in the Orange, Vaal, Gamtoos, Sundays and Fish Rivers for the contract year 1998-1999. Report No. OVI 1999/006/UPT. The National Department of Agriculture, Directorate of Agricultural Resource Conservation, 1999.

[90] E. Myburgh. Control of the pest blackfly, Simulium chutteri, in the Orange River, South Africa. Journal of the South African Veterinary Association, 70:46, 1999.

[91] R.W. Palmer. Principles of integrated control of blackflies (Diptera: Simuliidae) in South Africa. WRC report No. 650/1/97. Water Research Commission, 1997.

[92] R.W. Palmer and F.C. De Moor. Annotated records of blackfly (Diptera: Simuliidae) distribution in southern Africa. African Entomology, 2:223–251, 1998.

[93] E. Myburgh and E.M. Nevill. Review of blackfly (Diptera: Simuliidae) control in

South Africa. Onderstepoort Journal of Veterinary Research, 70:307–317, 2003.

[94] B. Hocking. The intrinsic range and speed of flight of insects. Transactions of the Royal Entomological Society of London (UK), 99:475–496, 1953.

[95] D.M. Davies, B.V. Peterson, and D.M. Wood. The black flies (Diptera: Simuli­idae) of Ontario. In Proceedings of the entomological society of Ontario, volume 92, chapter Adult Identification and Distributions of Six New Species, pages 70–154. Entomological Society of Ontario (CA), 1962.

[96] D.M. Hunter. Sugar-feeding in some Queensland black flies. Journal of Medical Entomology, 14:229–232, 1977.

[97] J.F. Sutcliffe. Black fly host location: A review. Canadian Journal of Zoology (CA), 64:1041–1053, 1986.

[98] J.S. Welton, J.A.B. Bass, M. Ladle, and W.J. Merritt. Distribution of oviposition sites and characteristics of the egg development in the ‘Blandford Fly’ Simulium posticatum (Diptera: Simuliidae). Journal of Applied Ecology, 24:865–879, 1987.

[99] G. Gibson and S.J. Torr. Visual and olfactory responses of haematophagous Diptera to host stimuli. Medical and Veterinary Entomology, 13:2–23, 1999.

[100] D.M. Davies and B.V. Peterson. Observations on the mating, feeding, ovarian devel­opment and oviposition of adult black flies (Simuliidae, Diptera). Canadian Journal of Zoology (CA), 34:615–655, 1956.

[101] B.V. Peterson. Observations on mating, feeding and oviposition of some Utah species of black flies (Diptera: Simuliidae). The Canadian Entomologist (CA), 91:147–155, 1959.

[102] R.W. Crosskey. The natural history of blackflies. John Wiley & Sons (UK & US), 1990.

[103] G.S. Nelson. Human Onchocerciasis: Notes on the history, the parasite and life cycle. Annals of Tropical Medicine and Parasitology, 85:83–95, 1991.

[104] J.B. Davies. Sixty years of Onchocerciasis vector control: A chronological summary with comments eradication, reinvasion, and insecticidal resistance. Annual Review of Entomology, 39:23–45, 1994.

[105] J.-M. Hougard, L. Yaméogo, A. Sékétéli, B. Boatin, and K.Y. Dadzie. Twenty-two

years of blackfly control in the Onchocerciasis control programme in west Africa. Parasitology Today, 13:425–431, 1997.

[106] M.A. Rodriquez-Perez, F. Reyes-Villanueva, and M.H. Rodriquez. Estimating the gonotrophic cycle and survivorship of Simulium ochraceum (Diptera: Simuliidae) during routine vector surveillance in southern Mexico. Journal of the American Mosquito Control Association (US), 11:360–362, 1995.

[107] E.M. Samba. Ten years of onchocerciasis control. Report No. OCP/GVA/85. World Health Organisation, 1B:43–57, 1995.

[108] D.H. Molyneux and J.B. Davies. Onchocerciasis control: Moving towards the mille­nium. Parasitology Today, 13:418–425, 1997.

[109] Kirstyn E's weblog -Onchocerciasis (river blindness). http://kirstyne. wordpress.com/2007/10/11/onchocerciasis-river-blindness.

[110] P.C. De Villiers. Simulium dermatitis in man -Clinical and biological features in South Africa. A case report. South African Medical Journal, 71:523–525, 1987.

[111] P.G. Mason and J.A. Shemanschuk. Black flies. Agricultural Canada Publication (CA), 1499/E, 1990.

[112] Department of Medical Biometry University of Tübingen. Diagnosing Onchocerciasis by palpation of nodules. http://www.uni-tuebingen.de/modeling/Mod_Oncho_ Diag_Palp_Index_en.html.

[113] F.C. De Moor. Determination of the number of instars and size variation in the larvae and pupae of Simulium chutteri Lewis 1965 (Diptera: Simuliidae) and some bionomical implications. Canadian Journal of Zoology (CA), 60:1374–1382, 1982.

[114] J.R. Anderson and G.H. Voskuil. A reduction in milk production caused by the feeding of blackflies (Diptera: Simuliidae) on dairy cattle in California, with notes on the feeding activity on other animals. Mosquito News (US), 23:126–131, 1963.

[115] J.A. Steenkamp. 'n Ondersoek na die wisselwerking tussen sommige ekologiese fak­tore en die bevolkings van Simulium damsnosum Theobald en S. nigritarse Coquillett (Simuliidae: Diptera) in die Vaalrivier by Parys. Potchefstroom University, 1972. DSc Thesis.

[116] F.C. De Moor. Blackfly problems in and along the Vaal River. In Proceedings of a

joint symposium convened by the foundation for research and development and the Vaal River Catchment Association, pages 159–173. FRD & VRCA, 1986.

[117] L.C. Jordaan and H. Van Ark. A survey of annoyance of livestock by Simulium chutteri Lewis along the Orange River, South Africa (diptera: Simuliidae). Onder­stepoort Journal of Veterinary Research, 57:189–195, 1990.

[118] R.W. Palmer, M. Edwardes, and E.M. Nevill. Timing of larvicide treatments for the control of pest blackflies (Diptera: Simuliidae) in a semi-arid environment in South Africa. Journal of Vector Ecology, 21:48–59, 1995.

[119] F.M. Chutter. On the ecology of the fauna of stone in the current in a South African river supporting a very large Simulium population. Journal of Applied Ecology, 5:531–561, 1968.

[120] A.W. Brown. A new insecticide for the control of blackflies (Diptera: Simuliidae). World Health Organisation, 27:51–522, 1962.

[121] R. Carson. Silent spring. Houghton Mifflin Harcourt Publishing Company, Boston (US), 1962.

[122] M. Car and F.C. De Moor. The response of Vaal River drift and benthos to Simulium (Diptera: Nematocera) control using Bacillus thuringiensis var. israelensis (H-14). Onderstepoort Journal of Veterinary Research, 51:155–16, 1984.

[123] C.J. Howell, G.J. Begemann, R.W. Muir, and P. Louw. The control of Simuliidae (Diptera: Nematocera) in South African rivers by modification of the water flow volume. Onderstepoort Journal of Veterinary Research, 48:47–49, 1981.

[124] F.C. De Moor. A community of Simulium species in the Vaal River near Warrenton. University of the Witwatersrand, 1982. PhD Thesis.

[125] F.C. De Moor and M. Car. A field evaluation of Bacillus thuringiensis var. israelensis as a biological control agent for Simuliidae chutteri (Diptera: Nematocera) in the Middle Orange River. Onderstepoort Journal of Veterinary Research, 53:43–50, 1986.

[126] M. Car. Laboratory and field trials with two Bacillus thuringiensis var. israelensis products for Simulium (Diptera: Nematocera) control in a small polluted river in South Africa. Onderstepoort Journal of Veterinary Research, 51:141–144, 1984.

[127] R.W. Palmer. Biological and chemical control of blackflies (Diptera: Simuliidae) in

the Orange River. WRC report No. 343/1/95. Water Research Commission, 1995.

[128] R.W. Palmer, M. Edwardes, and E.M. Nevill. Downstream carry of larvicides used in the control of pest black flies (Diptera: Simuliidae) in the Orange River, South Africa. Journal of Vector Ecology, 21:37–47, 1995.

[129] R.W. Palmer. Short-term impacts of formulations of Bacillus thuringiensis var. is­raelensis De Barjac and the organophosphate temephos, used in blackfly (Diptera: Simuliidae) control on rheophilic benthic macroinvertebrates in the Middle Orange River, South Africa. South African Journal of Aquatic Science, 19:14–33, 1993.

[130] R.W. Palmer and A.R. Palmer. Impact of repeated application of Bacillus thuringien­sis var. israelensis De Barjac and temephos used in blackfly (Diptera: Simuliidae) control on macroinvertebrates in the Middle Orange River, South Africa. South African Journal of Aquatic Science, 21:35–55, 1995.

[131] E. Myburgh. The influence of developmental temperature on the adult survivial of Simulium chutteri (Diptera: Simuliidae). University of Pretoria, 2002. MSc Thesis.

[132] R.W. Palmer, N. Rivers-Moore, W. Mullins, V. McPherson, and L. Hattingh. Guide­lines for integrated control of pest blackflies along the Orange River. WRC report No. 1558/1/07. Water Research Commission, 2007.

[133] R.E. Simmons, C. Boix-Hinzen, K.N. Barnes, A.M. Jarvis, and A. Robertson. The important bird areas of southern Africa. BirdLife South Africa, 1998.

[134] The ramsar convention on wetlands. http://www.ramsar.org/.

[135] M.D. Anderson, H. Kolberg, P.C. Anderson, J. Dini, and A. Abrahams. Water­bird populations at the Orange River mouth from 1980-2001: a re-assessment of its Ramsar status. Ostrich 74(3&4), 2003.

[136] G.A. Shaw, J.B. Adams, and T.G. Bornman. Sediment characteristics and vegetation dynamics as indicators for the potential rehabilitation of an estuary salt marsh on the arid west coast of South Africa. Elsevier Journal of Arid Environments 72, 2008.

[137] Orange River ecology. Assessment of environmental water requirements for the Or­ange River mouth. DWA Report No. V/D400/01/E001, 1990.

[138] J.H. Day. Estuarine ecology with particular reference to southern Africa. AA

Balkema, Cape Town, South Africa, 1981.

[139] Great Brak estuary management programme. Report on the monitoring results for the period April 1993 to March 1994. CSIR, Stellenbosch, South Africa, 1994.

[140] L. van Niekerk, P. Huizinga, S. Taljaard, and A.K. Theron. Orange estuary abi­otic specialist report: hydrodynamics, water quality and sediment dynamics. CSIR, Stellenbosch, South Africa, 2003.

[141] A. Venter and M. van Veelen. Refinement of the instream flow requirements of the Orange River and Orange River mouth. DWAF, 1996.

[142] Environmental rehabilitation: Orange River salt marshes. CSIR, Stellenbosch, South Africa, 1991.

[143] P.D. Morant and M. O’ Callaghan. Some observations on the impact of the March 1988 flood on the biota of the Orange River mouth. Transactions of the Royal Society of South Africa 47, 295-305, 1990.

[144] T.G. Bornman, J.B. Adams, and C. Bezuidenhout. Adaptations of salt marsh to semi-arid environments and management implications for the Orange River mouth. Transactions of the Royal Society of South Africa 59(2), 2005.

[145] M. Fenner and K. Thompson. The ecology of seeds. Cambridge University Press, Cambridge, UK, 2005.

[146] K.N. Barnes. The Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland. BirdLife South Africa, 2000.

[147] P. Barnard. Biological diversity in Namibia: a country study. Namibian National Biodiversity Task Force, Windhoek, Namibia, 1998.

[148] BirdLife International. http://www.birdlife.org/.

[149] A.J. Williams. Orange River mouth wetland. Directory of Wetlands of International Importance data sheet. Department of Environmental Affairs and Tourism, Pretoria, 1990.

[150] IUCN Red List of threatened species. http://www.iucnredlist.org/.

[151] DWA gauging station database. http://www.dwa.gov.za/hydrology/cgi-bin/

his/cgihis.exe/station.

[152] C. McBride. South African Weather Service, 2010. Personal communication.

[153] F. Sibanyoni. Department of Water Affairs pretoria, 2010. Personal communication.

[154] K.A. Fair. Operational model of the orange river. WRC report No. 865/1/03. Water Research Commission, 2003.

[155] J. Hallowes. DHI SADC, 2010. Personal communication.

[156] J. van Bosch. Department of Water Affairs bloemfontein, 2010. Personal communi­cation.

[157] A. du P. le Grange, C.J. Briers, and J.D. Rossouw. Situation assessment -Orange River System: Real-time operating system for the Lower Orange River. Department of Water Affairs, 2005.

[158] R.S. McKenzie and C. Roth. The evaluation of river losses from the Orange River downstream of the P.K. Le Roux Dam. WRC Report No 510/1/94, 1994.

[159] L. De Doncker and P. Troch. Progress report: Femme-modelling. 2007.

[160] L. De Doncker. A fundamental study on exchange processes in river ecosystems. Universiteit Gent, 2009.

[161] K. Soetaert, V. deClippele, and P. Herman. FEMME, a flexible environment for mathematically modelling the environment. Elsevier (NL), 2002.

[162] K. Soetaert, V. deClippele, and P. Herman. A flexible environment for mathemat­ically modelling the environment -Manual. Netherlands Institute of Ecology (NL), 2003.

[163] K. Buis et al. Fundamentele studie van uitwisselingsprocessen in rivierecosystemen ­Ge¨ıntegreerde modelontwikkeling. Tijdschrift Water, 2007.

[164] P. F. Mufeti. Orange River flood wave modeling. Brandenburgische Technische Uni­versit¨at Cottbus (DE), 2007.

[165] V. T. Chow. Open channel hydraulics. McGraw-Hill International editions (SG), 1959.

[166] H. Chanson. The hydraulics of open channel flow: An introduction. Butterworth-Heinemann, Oxford (UK), 1999.

[167] DWA -Lower Orange. http://www.dwaf.gov.za/orange/low_orange.

[168] Augrabies Falls National Park. http://www.sanparks.org/parks/augrabies.

[169] P. Fourie. Scenery picture gallery. http://www.saao.ac.za/~pah/scenerypics. html.

[170] D.A. Hughes and F. Münster. Hydrological information and techniques to support the determination of the water quantity component of the Ecological Reserve for rivers. WRC Report No. TT 137/00, 2000.

[171] S. Taljaard. Pre-feasibility study into measures to improve the management of the Lower Orange River and to provide for future developments along the border between Namibia and South Africa: Specialist report on the determination of the prelimi­nary ecological reserve on a rapid level for Orange River estuary. Permanent Water Commission, 2005.

 

Universiteit of Hogeschool
Burgerlijk ingenieur bouwkunde
Publicatiejaar
2010
Kernwoorden
Share this on: