Abstract
Limited surface supplies without considering crop water demand has created gap between water applied and its requirement.
It results into extensive groundwater pump-age. It is therefore required to study crop water demand and supply at a specific
hydrological unit level. In the current study crop water supply and demand was assessed in command area of two main
distributaries (Killianwala and Mungi) of Lower Chenab Canal (LCC) based on unique hydro-geology. Three parameters
including land use, soil type, and topography were used to develop Hydrological Response Units (HRUs) using Soil and Water
Assessment Tool (SWAT) model and GIS. Forty-one and forty-two HRUs were developed for Killanwali and Mungi
distributaries, respectively. The daily reference crop evapotranspiration (ETo) for the canal commands was estimated using
CROPWAT 8.0 model for the period of six years (2007-12). The crop water requirement was estimated using ETo, crop
coefficient (Kc) and cropping period at HRU level. The water shortages observed were more than 50% at both distributaries.
Results showed that the maximum water shortfall at Killianwala and Mungi distributary were 4.1 MCM/Year and 4.9
MCM/Year, respectively. It was concluded that canal water supplies should be scheduled with the consideration of water
requirements of each zone. Eventually, a shift from supply based to demand-based irrigation is highly recommended.
