EVALUATION OF SPRINKLER IRRIGATION SYSTEM AT BELES SUGAR DEVELOPMENT PROJECT

Abstract

xii | P a g e Irrigation is the largest user of water. Effective and efficient use of water is very crucial to sustain water resources. Effective, sustainable, and efficient sprinkler irrigation system is a combined effect of proper system design, operation, maintenance, and management. Appling appropriate field irrigation practices safeguard that crops could get peak supply of water in their root zone for achieving best yield of crops without facing water stress and damaging the quality of soils. Sugar cane fields at study area irrigated to irrespective of the soil type, growing month, and stage of crop growth with the design application efficiency of 70%. But, now the system is not working with the full design capacity so that evaluating the actual sprinkler application efficiency under existing condition was very important. Therefore, this study was conducted to evaluate the existing actual water application uniformity with design standards, and develop irrigation scheduling based on the actual existing water application with respect of soil, growing month and stage of growth. Primary and secondary data were used to attain the objective of the study. Representative soil samples were taken for soil texture, bulk density, field capacity and wilt point test. The actual water application uniformity was measured for single and four overlapping sprinklers by installing catch can at a grid spacing of 3*3 m with two replications at hydrant pressure of 2.5 and 3.0 bars. Secondary data collected were weather data, effective root depth and crop coefficient. The performance parameters analyzed were, crop evapotranspiration, net irrigation requirement, net depth of application, irrigation interval, sprinkler set hour, uniformity coefficient(CU) ,distribution uniformity(DU), and system uniformity, and application efficiency. The average actual DU and CU obtained at 3 and 2.5 bars at existing sprinkler spacing of 18mx18m was 53% and 63% respectively. The value of CU was lower than the recommended value of 75%. The catch can data for single sprinkler were overlapped for different spacing‟s and values DU and CU were calculated. Acceptable value of CU equal to 75% and 76 % at operating pressure 2.5 bar and 3 bar respectively obtained at 12m x 18m spacing. The average sprinkler discharge at 3.0 and 2.5 bar operating pressure was 0.9 and 0.8 m 3 /hr respectively. The sprinklers had an average actual application efficiency of 62%. Sprinkler set hours obtained for the age of 0-3, 3-6, 6-15 and >15 month was 13, 19, 25 and 38 hr respectively. Irrigation interval obtained for age of 0-3, 3-6, 6-15 and >15 month varied with growing month and had a range of 7-10, 6-21, 7-20, and 16-24 days respectively. According to the study the system was not working under full design capacity and actual application uniformity was out of the acceptable range. The irrigation scheduling based on the actual efficiency was recommended with respect of growing month and stage of growth.