Abstract:
Appropriate irrigation water management increases the yield per unit of land and water without affecting other users. Most irrigation systems in the world including Ethiopia were faced under different problems like salinity, sodicity, poor performance and water scarcity due to inadequate irrigation water management practice. Therefore, this study carried out on Amibara state farm to assess the effect of inadequate irrigation management on saline-sodicity status of soil and irrigation performance indicators and to investigate status of irrigation control structure on farm and causes of water scarcity problem to the downstream users.
Primary data such as soil sample at 90cm and 30 cm soil depth was collected to evaluate soil physical and chemical properties, respectively. Flow along the canal and on field, soil water content and yields were collected to determine performance indicators of state farm. Data that related to causes of water scarcity problem and status of irrigation control structure also collected through interview and field observation. Secondary data such as climate and crop data were collected to evaluate seasonal crop water requirement by using CROPWAT 8 model.
The obtained average soil bulk density, basic infiltration rate, and organic matter were 1.29gm/cm3,0.88% and 3.6mm/hr., respectively. Average soil PH, electric conductivity, sodium absorption ratio and exchangeable sodium percentage before and after irrigation were 7.84 and 7.79, 0.16 and 0.1 ds/m, 6.29 and 5.96 and 7.42 and 7.0%, respectively.
Average internal performance indicators such as conveyance efficiency, application efficiency, storage efficiency, percolation losses and overall efficiency were 82.2%, 30.37%, 75.5%, 65.7% and 24.96%, respectively. Mean relative water and irrigation supply were 1.83 and 3.5 and water and land productivity also 0.76kg/m3 and 30.35qun/ha, respectively.
Poor irrigation structure such as nonfunctional intake, escape canal, canal weeding and traditional division box and canal offtakes increased water loss along the canal in the state farm. Due to this, downstream farmers used untreated wastewater for irrigation purpose that affected health of irrigator, crops and soil properties. Therefore, modification of irrigation control structure, irrigation scheduling and demand-based water allocation among the users to be necessary to increase farm productivity and minimize water scarcity problem.
