Assessment of smallholder irrigation perfomance; management of conveyance and distribution infrastructure (at Murara and Nyamatanda North East Zimbabwe)
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A study was carried out on two smallholder surface irrigation schemes; Murara in Mutoko District and Nyamatanda in Mudzi District, north east Zimbabwe, between 1999 and 2001. The objective was to investigate possible causes of poor performance, emphasis on water management along the conveyance and distribution infrastructure. The methodologies used included a socio-economic survey questionnaire, an inventory of the existing infrastructure and assessment of its hydraulic suitability, monitoring of the irrigation process and practices, and calibrating the infrastructure for easy use by the farmers. Results showed that the farmers have an appreciation of the irrigation process and the flow in the canals was adequate for irrigation with water duty of at least 8.2 l/s/ha in an eight hour day, for both irrigation schemes against a demand of two l/s/ha. Between the two schemes an average of 60 percent of the canal slopes are outside the recommended 1:300 to 1:2 000 limits that seriously affects water management. It was also observed that both irrigation schemes have distribution and regulation structures that lack water-measuring mechanisms and the water control mechanism is poorly defined, resulting in poor water management. Evidence of poor water management was observed in poor crop yields, use of lost water for fish farming at Murara Irrigation Scheme and loss of about two ha of irrigated fields at Nyamatanda Irrigation Scheme due to waterlogging. Our general recommendations are to rehabilitate the irrigation infrastructure that does not meet design specifications, improve on water management through proper use, repair and maintenance of the infrastructure and generally to educate the farmers to take responsibility for their schemes.