Evaluation of irrigation water demand and agricultural land use in relation to surface water availability in Chongwe catchment.

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Mwenya, Teddy
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University of Zambia
Zambia has been experiencing population increase over the years. The growth has been characterised by an increase in agricultural irrigation activities, competitiveness in water use which have caused water stress and conflicts in some catchments. Some water availability assessment works in Chongwe Catchment have been done by various researchers but very little work has been done on assessment of water demand. Some of the effects of water depletion such as drying up of the Chongwe River and water use related conflicts among water users are seen, however the extent of water demand is still unknown. The major objectives of the research were to determine water demand for irrigation in Chongwe Catchment and its impact on water availability in the Catchment. The study helped to design ways of managing water resources, allocation and understand environmental flow requirements of the catchment. The methodology involved literature review, data collection, data analysis, presentation of research findings and report writing. Literature review was achieved through the use of text books, journals and other published materials. Data was collected by field observations, interviews and measurements. Data analysis was done using Microsoft excel 2010 as well as FAO Penman calculator. Judgment sampling method was used due to inaccessibility of some farms. Data that was used include flow measurement data, rainfall data and irrigated areas. The study showed that the demand for irrigation has been increasing since 1963. Water demand for irrigation almost causes the flows on the Chongwe River at Chongwe Bridge to cease completely from mid-September to October every year. This is the reason during the same period there is water shortage in Chongwe Township as the water level at LWSC’s abstraction point becomes too low to be pumped. Furthermore the study revealed that between July and October every year, there shall be some water shortages in several parts of the catchment. After October, the situation will be getting better as some runoff gets generated from rainfall. Nevertheless, the runoff that gets generated in October is not adequate to sustain the river owing to the high demand for irrigation. The study further demonstrated that, there has been a general increase in the long term flows. Analysis of the impact of demand on water availability gave positive correlation values except at Kapilyomba station which gave a negative correlation values. That means water demand has been causing a decrease in long-term flows at Kapilyomba station unlike other stations. The increase in flows at other stations may be attributed to construction of hydraulic structures such as dams. The study was also an eye opener as some research gaps were identified such as need for rainfall runoff model development, and a study on effluent release into the catchment’s streams as well as its impact on the hydrology of the catchment. Key Words: Water, Irrigation, Demand, Chongwe, Catchment, Availability, Correlation. v
Agricultural conservation. , Water conservation--Chongwe, Zambia , Irrigation--Management--Chongwe, Zambia