INDUS BASIN IRRIGATION SYSTEM WATER BUDGET AND ASSOCIATED PROBLEMS

Abstract

Around 74% of mean annual river flows ( 140 MAF ) are diverted to the canal system and the rest flows to the Arabian Sea ( 19% ) or contributes to the river system losses ( 7% ) . Efficiency of the canal irrigation system is extremely low , as 53% of water ( 55 MAF ) is lost in conveyance through canals, watercourses and field channels. Thus system conveyance efficiency is only 47 % . The loss of 55 MAF of canal water in conveyance to the fields can be translated to a financial loss of around Rs . 3.3 Billion per annum assuming a value of Rs . 60 per acre - foot of  water based on existing Abiana rates . In terms of pumped water cost it will be around Rs. 55 billion per annum .  In - efficient application of water in basin / fiood irrigation contributes to around 25% of water losses in fields. This is mainly due to un - levelled fields and unscheduled irrigation without considering the management allowed deficit based on crop and soil needs. Total loss of water in conveyance and field application ( around 64% of canal diversions and 32% of groundwater ) is not only loss of water but it also adds to waterlogging and salinity . Acute shortage offreshwater forced farmers to exploit groundwater by installing tubewells and thus use of marginal to brackish quality groundwater resulted in secondary salinization and increased dependence on energy . The loss of produc tivity in the IBIS due to waterlogging and salinity was estimated as 25% of total crop productions . The GNP of crops in Pakistan is over Rs. 355 billion per annum . Thus the production loss due to waterlogging and salinity can be estimated as around Rs. 88 billion per annum . Around 10% of the irrigated area within canal commands is  severely affected due to waterlogging and salinity and value of land is now much lower than the productive lands and in certain cases it is only 10% of the problem free lands . This is a financial loss to farmers and their families and an economic loss to the country .