CHARACTERIZATION AND PERFORMANCE EVALUATION OF IRRIGATION WATER DELIVERY SYSTEM AT WONJI/SHOA SUGARCANE PLANTATION

Abstract

The need to use water efficiently and effectively is necessary to optimize maximum returns and conserve water resources due to the increasing demand of irrigation water. This can only be achieved through effective design, proper construction, timely and quality maintenance and well planned operation and management of irrigation systems. The proper functioning of water conveyance and distribution structure has an effect on the ability to convey irrigation water at the required time and place in a sustainable manner throughout the irrigation period. A study was conducted using four performance indicators (adequacy, efficiency, dependability and equity) in order to evaluate the water delivery performance of pumps, canals and night storage reservoirs and to know the general health of the system regarding to water distribution and operational performance. Weather data recorded at sugar estate was used to compute the crop water requirement using CROPWAT version 8 computer program. To know the actual water delivered to plantation cane fields, measurements of water from main pump station and other five secondary canals starting from five different secondary night storage reservoir was carried on daily basis with interval of 1 hour. The actual capacity of canal and reservoirs were measured using GPS and other surveying instrument assisted by computer programme called Auto CAD. Other secondary data like area under cane cultivation soil type, drying and harvesting periods were obtained from plantation department. From the study of characterization of the structure, all water delivery structures except right branch canal, secondary canal start from WO reservoir and two tertiary night storage reservoir were designed and constructed according to the requirement. But through time the discharge capacity of pumps were reduced and longitudinal slope and cross section of canals were also changed due to lack of proper maintenance and reconstruction activity. The result showed that adequacy performance for pump (0.69) and canals (0.62) were found to be poor. The outcome of equity was fair for pumps (0.22) and good for canals (0.04). Poor dependability was computed for pump (0.40) and good for canals (0.09) throughout the year. Generally, the performance indicators reveal that the water distribution throughout the plantation had no ability to meet the required amount with the required time and place. It is recommended that the Estate should practice proper planning and scheduling of irrigation water supply according to the weather condition, replacement of the existing pumps which is located at main station with design capacity, enlarging the canal cross section in right branch canal and appropriate and timely maintenance both in pumps and canals.