The following two case histories were prepared in summary at the suggestion of the Consultation, who felt that they represent good examples of the two extremes in approaches to planning for river basin development.
Kainji was conceived as a multi-purpose dam but in its execution the provision of hydropower was the primary consideration. Biologists and social scientists came on to the scene after the dam had been designed and, indeed, after construction had started.
Pre-impoundment biological studies were aimed at and did provide estimates of fish and field crop production potentials in the lake basin and areas upstream. Little attention was given to livestock although wildlife conservation requirements were covered. No attempt was made to evaluate the impact of the dam in downstream areas, apparently because it was thought that they were unlikely to be affected because of the pattern of local rainfall.
Decrease in fish and crop yields from the fadamas (floodplain depression lakes) due to low water level in the river channel and floodplain was noted within one year of dam closure around Jebba to Lokoja. Within the second and third years, the effects of the new rather low water level regime during the flood season coupled with unsteady flood rises had been felt as far down-river as the apex of the Niger Delta. The Niger at Onitsha was scarcely half bankfull. Consequently the rich and extensive Anambra floodplain northeast of Onitsha was grossly desiccated and few floodplain lakes/ponds made seasonal connexion with the main river channel.
Fishermen and farmers watched helplessly as their yields fell. By 1970, the Lower Anambra Basin which hitherto had been responsible for 70% of freshwater fish and yam production in Eastern Nigeria, had lost both 60% of its fish output and yam production running into 100 thousand tonnes. By 1974, the Sahelian drought had helped to bring catches from the floodplains to almost a standstill and only a trickle from the main channel fisheries Most of the professional fishermen had to migrate to the coastal brackishwater zone. Gear dealers had to look for new markets in Benin and Ghana.
With relatively better floods (i.e., with higher amplitudes since dam construction) in the last two years, the situation has somewhat improved. However, fishermen are finding it difficult to locate good fishing grounds and to predict catches from the flood characteristics as before in these downstream stretches - a situation which may be related to the adverse effects of the dam on species and stocks composition and population structure/distribution.
It is noteworthy that although basic and developmental fisheries studies are continuing in the lake basin, little effort has been made to monitor on a similar basis the downstream effects of the dam. Thus, in spite of better catches in the lake, the overall fisheries production of the Nigerian Niger continues to be below average since Kainji. The lesson for fisheries management is obvious.
The Mekong project is perhaps the most ambitious and comprehensive river basin development plan ever initiated. It will guide the development of the water resources of a vast basin, larger than France, which is drained by the world's sixth largest river, with an annual discharge of 475 000 000 000 m³ of water into the South China Sea. Development of these resources on a regional scale is the single most important engineering venture that could be undertaken to improve the social and economic welfare of the peoples who inhabit the Lower Mekong Basin. Four countries are involved: Democratic Kampuchea, Lao PDR, Thailand and the Socialist Republic of Viet Nam. The project will foster improved food supplies through agriculture and fisheries along with industrial growth, and will implement flood control and navigation projects for the expanding population.
The Mekong project is unique because it is planned for integrated development of a river basin. The concept of integrated development implies the use of water for several purposes simultaneously as well as consideration of the entire economic, social and environmental macrosystem throughout the drainage basin. For that reason, the project involves numerous special studies in many fields including their socio-cultural and socio-economic aspects. Fisheries, public health, forestry and wildlife, archaeology, resettlement and the carrying capacities of the environments are all being studied, in addition to the more normal technical investigations for the main stream, tributary and delta engineering works and the economic, agricultural and industrial power investigations necessary for the project to achieve its primary and secondary objectives. All the aforementioned activities are conducted as a coordinated series of studies to understand and quantify wherever possible the basinwide implications of the development actions, including effects on watersheds, reservoirs and downstream areas. In the case of major developments such as the proposed Pa Mong dam on the mainstream, the results of these investigations are used as the data base for studies to determine design features of the engineering structures, programmes and relative capital allocations necessary for development activities that will optimize the benefits and mitigate the adverse effects of the water resource development on associated and ancillary resources.
This exemplary approach to water resources development is made possible by the foresight of the Mekong Committee, which comprises plenipotentiary representatives of the four riparian countries, as well as by the generous support of 25 cooperating countries and agencies outside the Basin. Another circumstance that has favoured this multi-sectoral approach is the demonstrable magnitude of the benefits from resources such as fisheries which are usually, but erroneously, considered as ancillary to other activities in water resource development around the world.
