Rotational method in farmer managed irrigation systems Tanzania
Gowing, J.W.|Tarimo, A. K.P.R / 1996

Most of the traditional farmer-managed irrigation systems (FMIS) in Tanzania have their water delivery schedule based on Demand. Rotational schedules have been introduced to the newly upgraded FMIS which came into operation in the late 1980's such as Majengo irrigation scheme in the Usangu Plains in Mbeya region and Lower Moshi irrigation scheme in Kilimanjaro region. This Study which was conducted in two cropping seasons (1991/92 and 1992/93) concentrated on a Rotational schedule introduced in Majengo and its results compared to Ipatagwa a neighbouring traditional irrigation scheme located in the same Usangu Plains. The results showed that although the water delivery schedule in Majengo was designed to operate on Rotation and likewise the water conveyance systems were constructed to meet the water delivery objective, the water users resorted to their old system of irrigation. An in depth performance evaluation over the two seasons showed that Majengo scheme performed better than Ipatagwa scheme, but it is concluded that this was not due to improved water distribution and control. Rather, the high performance of the irrigation systems shown in Majengo over that of Ipatagwa was mainly due to bigger water capture because of a bigger intake and canal structures. Other parameters such as crop variety and fertilizer application had little or no effect. The rotational schedule envisaged in Majengo was not practised simply because the farmers lacked irrigation water management technology and there is a possibility that the irrigation system may not be sustainable. Given that rotational schedule needs some expertise which our farmers do not have, more careful consideration must be given during the design phase to the manageability of alternative methods of water control. If it is inevitable that rotation has to be practised, then it should be between tertiaries rather than between secondaries as was the case in Majengo until such time that farmers are acquainted with the kind of irrigation water management.