ABSTRACT
Efficient operation and maintenance of an irrigation scheme is a necessary condition for preventing serious health consequences. An irrigation scheme is rarely built in a vacuum, where disease is concerned. Health planning only takes place in the development of an irrigation scheme if money is spent and efforts are made. A specific percentage of the project costs should be devoted to health planning and preventive measures. The creation of a lake and an irrigation system establishes a radically new ecological regime and with it a new pattern of infectious disease. Changes in insect and snail populations, in conjunction with other direct effects of irrigation projects, may cause marked changes in the transmission of the following infections: schistosomiasis, onchocerciasis, malaria, arboviral infections and filariasis. Dams are always created as a water conservation device and a siphon spillway determines a specific release policy which may well not be that which would be selected from a water resources standpoint.
