Spatial Climate Variability and Its Impact on Irrigated Hydrology in a Canal Command

摘要

Depth to watertable continuously increases from head to tail in most of the canal commands in Punj ab, Pakistan, in spite of equitable canal water supplies. In the wake of increased groundwater use with passage of time, the tail end farming community and irrigation management institutions are to confront this emerging issue very prudently. To comprehend this dilemma, canal water availability, crop water requirement and groundwater recharge across the Lower Bari Doab Canal command were analyzed. Annual rainfall decreases towards tail (212 mm) as compared to head (472 mm), in contrary, annual gross and net crop water requirement at tail end are 10.2 and 32.5% higher, respectively, as compared to head end. As a result, groundwater mining is taking place in tail end at 0.34m/year, whereas in head end areas, the situation is stable. Actually, in tail end areas, groundwater recharge rates are considerably low as compared to the head end. Spatial climate variability across the command is the main cause for these inequities. Realloca-tion of canal water and/or enhancing recharge to groundwater in these relatively more water stressed areas during wet years needs to be sought, otherwise any groundwater management activity in this regard will not have any technical and social viability. Ignoring climatic variability within the canal command is one of the serious issues in irrigation system design that prevents achieving the optimal level of conjunctive water use and as a result, the highest potential agricultural output cannot be achieved.