Effect of Watercourse Lining on Water Distribution (Warabandi) in the Command Area of Laiqpur Ex Ali Bahar Minor, District Sujawal, Sindh, Pakistan

Abstract

A study was carried out to evaluate the impact of watercourse lining on water distribution (warabandi).For this study two watercourses, one lined (8-CL) and other unlined (11-R) of Laiqpur ex-Ali Bahar Minor were selected.The Theil’s Index was calculated on the basis of various parameters such as NIA (Net Irrigated Area), NWA (Net Wetted Area), CCA (Cultivable Command Area) and frequency of irrigation, actual TWA (Total Wetted Area) and predicted TWA (Total Wetted Area) and found as 0.22 and 0.496 for lined and unlined watercourses respectively. Hence, the effectiveness of warabandi was found as 78 and 50.4% for lined and unlined water courses respectively. The Theil’s Index values for head (31.07 acres), middle (31.76 acres) and tail (28.35 acres) sections of one lined and two unlined sections of the lined watercourse were determined as 0.147, 0.165 and 0.319 respectively, however for unlined watercourse, the Theil’s Index values were 0.21 (head), 0.5 (middle) and 0.6 (tail). This showed that in a lined section of the watercourse No. 8-CL, the effectiveness of warabandi was 85%, at its tail section it was 68% and that for tail section of the earthen w/c was only 40%. Variation of TIC in lined and unlined watercourse was 0.17 and 0.38 respectively. The conveyance loss per 1000 ft. in lined and unlined sections of watercourse 8-CL was 1.23% and 4.92% respectively, however in watercourse 11-R that was 4.9%. The conveyance efficiency in lined and unlined sections of the lined watercourse was98.76 and 90.60% and that for earthen watercourse was 70.59% and after lining, the cropping intensity increased up to 8%.