WATER DELIVERY PERFORMANCE OF SECONDARY CANALS IN TERMS OF ADEQUACY AND WATER USE EFFICIENCY IN SINDH PAKISTAN
Keywords:current metering, distributaries, equitable distributaries, gauge calibration
This study determines the water delivery performance and evaluation of secondary canals of the Nara Canal, situated in southern province of Pakistan. Hydraulic data such as water levels and discharge measurements were collected for four consecutive seasons (02 Rabi and 02 Kharif seasons) during 2014 and 2015. The data was collected through gauge readings installed at head, middle and tail reaches on weekly basis. The gauge readings were converted to flow rates by time to time calibration of these gauges. Simultaneously, the primary hydraulic data was collected from Sindh Irrigation and Drainage Authority (SIDA) offices. Results show that Bareji, Belharo and Mirpur distributaries were providing averagely less discharge during six, four and four months round a year, respectively. However, in the remaining months the water supply either remained as per design or in excess. Water delivery performance was ‘good’ in August, 2014 and ‘fair’ in June and July, 2014, while for the rest of the months of 2014 and 2015 were rated as ‘poor’. Study revealed that water use efficiency was higher at head reaches, equitable at middle reaches and inadequate at tail reaches during both the years. As a result of consistent over flows at head reaches the tail reaches always suffer especially when distributaries flow at a lesser rate than their designed discharges. In order to increase the performance of irrigation system, there is need to minimize system’s conveyance losses and improve water application efficiency. This could be done through proper management and water distribution plans at tertiary canal levels. There is need to continuously monitor and measure the water diverted to the secondary canals and make sure that water approaches at middle and tail reaches.