Spatio-temporal estimation of consumptive water use for assessment of irrigation system performance and management of water resources in irrigated Indus Basin, Pakistan

Abstract

Reallocation of water resources in any irrigation scheme is only possible by detailed assessment of current
irrigation performance. The performance of the Lower Chenab Canal (LCC) irrigation system in
Pakistan was evaluated at large spatial and temporal scales. Evaporative Fraction (EF) representing the
key element to assess the three very important performance indicators of equity, adequacy and reliability,
was determined by the Surface Energy Balance Algorithm (SEBAL) using Moderate Resolution Imaging
Spectroradiometer (MODIS) images. Spatially based estimations were performed at irrigation subdivisions,
lower and upper LCC and, whole LCC scales, while temporal scales covered months, seasons and
years for the study period from 2005 to 2012. Differences in consumptive water use between upper
and lower LCC were estimated for different crops and possible water saving options were explored.
The assessment of equitable water distribution indicates smaller coefficients of variation and hence less
inequity within each subdivision except Sagar (0.08) and Bhagat (0.10). Both adequacy and reliability of
water resources are found lower during kharif as compared to rabi with variation from head to tail
reaches. Reliability is quite low from July to September and in February/March. This is mainly attributed
to seasonal rainfalls. Average consumptive water use estimations indicate almost doubled water use
(546 mm) in kharif as compared to (274 mm) in rabi with significant variability for different cropping
years. Crop specific consumptive water use reveals rice and sugarcane as major water consumers with
average values of 593 mm and 580 mm, respectively, for upper and lower LCC, followed by cotton and
kharif fodder. The water uses for cotton are 555 mm and 528 mm. For kharif fodder, corresponding values
are 525 mm and 494 mm for both regions. Based on the differences in consumptive water use, different
land use land cover change scenarios were evaluated with regard to savings of crop water. It is found that
such analyses need to be complemented at more fine spatial resolutions (i.e. irrigation subdivisions)