Impact of quality and reliability of irrigation on field and farm level water productivity of crops

This paper examines the impact of quality and reliability of irrigation on water productivity of individual crops and cropping system in the farm through comparison of crops watered by different types of irrigation systems such as canal irrigation; well irrigation and conjunctive use. Then it analyzes the actual factors that drive differential productivity, and which change due to change in quality and reliability regime of irrigation. The study area is Bist Doab area in Punjab and the analysis was carried out for two agro-climatic regions, both semi-arid, one having medium to high rainfall and the other having low to medium rainfall. The first location (Changarwan) is predominantly canal and well irrigated, whereas the second location (Skohpur) has well irrigation and conjunctive use. The analysis involved working out an index called “irrigation quality index” for different types of irrigation systems, and then compares water productivity of individual crops vis-a-vis estimated values of this index, for each location. The crop water productivity parameters analyzed are: physical productivity of water in kg/m3 ; and water productivity in economic terms. Overall, the irrigation quality index was higher for: well irrigated fields as compared to canal irrigated fields and fields irrigated by both wells and canals in Skohpur; and canal irrigated fields for most crops in Changarwan. Comparison of irrigation water quality index estimated for major crops under different sources of irrigation vis-a-vis the water productivity of the respective crops show that differential reliability has an impact on economic productivity of water (Rs/m3 ). The fields, which received irrigation water of higher quality and reliability got higher water productivity in rupee terms. However, the impact of differential quality and reliability was not visible on physical productivity of water for fodder crops. Contrary to the belief that higher quality and reliability of irrigation would result in better yields, the fields, which were receiving poor quality irrigation gave higher yields. This was primarily due to the high nutrient load which canal water contained that increased the yield of those crops. Fodder crops also gave higher yields under less reliable irrigation water supply. Hence, one can conclude that improved quality and reliability of irrigation would help enhance the water productivity in crop production.