Lakes and reservoirs are affected by human interventions mainly by eutrophication. Changes in morphology are less common, although siltation and local alterations to the riparian zone can result from urbanisation,marina construction and deforestation. In lakes and particularly reservoirs used for water supply and power generation, rapid drawdown can occur that damages riparian vegetation and fish populations.
This report from WorldFish is divided into two sections, with annexes. Section One contains the workshop report, including the workshop results and outputs. Section Two contains summary papers of the workshop presentations with a record of relevant points of discussion. The annexes contain additional information such as the participant list, detailed findings and speeches.
This paper is arranged in two parts. The first summarizes technical issues surrounding such assessments, briefly reviews the water requirements of river fish and fisheries, and examines some of the ways for predicting these requirements. The second part examines practical experiences in southern Africa by outlining ten general principles that can guide the environmental flow assessment process.
This paper focuses on property rights and collective action in the Mekong region of Cambodia. Institutional arrangements in water management for community-based aquaculture in two villages in the Mekong area of Cambodia are described.
Faced with growing pressure upon freshwater resources, increased water productivity in agriculture is essential. Efforts to do so however need to consider the wider role of water in sustaining food production. This paper considers the importance of water management in sustaining fish production in tropical river basins, and the potential for enhancing food production and income to farmers by integrating fish production into some farming systems. Specific examples from selected river systems and irrigated farming systems in Africa and Asia are provided.
Most small waterbodies were built for irrigation and/or drinking water storage for humans and livestock, but have also been shown to play an important role in watershed management. Apart from natural lakes, small waterbodies are generally of two types: 1) reservoirs created by damming a river and, 2) ponds built on watersheds to collect and store surface runoff. There are millions of small waterbodies scattered throughout the world, most of which are poorly or not at all managed for fish production.
This article presents the methodological aspects of the development of a decision support system (DSS) based on Bayesian networks and aiming at assisting in the management of water-dependent resources (rice, fish, shrimp and crab). The principles of Bayesian networks are introduced, then the steps of model development are detailed and illustrated by the BayFish model being developed in the inland coastal zone of Bac Lieu Province (Vietnam). The particular feature of this DSS is that it is based on the contribution of local stakeholders.
The BayFish models are decision-support tools that show, and predict, the impact of land use and water management options on water-dependant food production. They allow users to see all the dimensions that need to be considered for a given modification of the system, and to allow down-the line the impacts of any suggested changes.
River fisheries in Africa are important because of their contribution of animal protein to human diets. Such fisheries are highly dependent on hydrological regimes and show considerable year-to-year variation in response to natural climatic events. River flow regimes are being increasingly altered by withdrawals by man, principally for agriculture. The modification of hydrological regimes is leading to diminishing catches of fish and changes in the number and size of the species caught.