Assessment of Water Allocations using Remote Sensing and GIS Modeling for Indus Basin, Pakistan

PSSP working paper 036, “Assessment of Water Allocations using Remote Sensing and GIS Modeling for Indus Basin, Pakistan”, uses satellite imagery to estimate crop water use and corresponding water productivity for each canal command area of the Indus Basin Irrigation System. Three years were selected for the study and two representative canal commands (Lower Chenab and Muzaffargarh Canal) were selected for detailed analysis and ground truthing. Spatially distributed maps of land use, crop water use, groundwater use and quality, soil and water salinity, and crop yields at a pixel resolution of 250 m (6.25 ha) were prepared and then verified by field surveys. GIS maps of canal water availability/supply were also prepared to account for the volume of water supplied through irrigation, and this spatial database was used to evaluate and create maps of water productivity in the different canal commands. The analysis shows that the area affected by soil salinity (strongly saline) in the basin has increased by 2.5% during the last five years. The average crop water use is 342 mm and 516 mm for Rabi and Kharif season, respectively. The variation in wheat yield ranged between 5,280 to 423 kg ha-1, while rice yield varied from 3,312 to 1,925 kg ha-1. Water productivity of wheat is also variable with a maximum of 1.34 kg m-3 and minimum estimated at less than 0.2 kg m-3. The water productivity of rice shows maximum of 1.12 kg m-3 and minimum estimated at less than 0.4 kg m-3. The cost incurred to irrigate one acre of land with groundwater is around Rs. 4,000 and Rs. 9,000 for wheat and rice, respectively, while canal water costs are only Rs. 50 and Rs. 85. The total cost of production is also higher in areas where groundwater is being used.  Several rationalization policies based on cost and water productivity are suggested to reduce the cost gap between the two irrigation sources.