LONG-TERM GROUNDWATER QUALITY AND SALINE INTRUSION ASSESSMENT IN AN IRRIGATED ENVIRONMENT: A CASE STUDY OF THE AQUIFER UNDER THE LBDC IRRIGATION SYSTEM

Pakistan's irrigation system is more than a century old. Due to the increasing population and consequent intensifying agriculture, dependence on groundwater is successively increasing. The underground reservoir that was recharged during the first half of the twentieth century by the newly built irrigation system with low cropping intensities is now being overexploited. Groundwater quality is variable, both vertically and horizontally, with the exception of areas adjacent to rivers, where it is fresh. This paper describes groundwater quality in the Lower Bari Doab Canal (LBDC) irrigation system based on 47 years of historic water quality data (TDS, SAR and RSC). Areas are delineated in the form of zones and depths. The tail end of the command is facing severe groundwater depletion, whereas in certain parts, groundwater quality deterioration with the passage of time has also been detected. Possible reasons and mechanisms of saline intrusion within the aquifer are described. Lateral saline intrusion is not a major issue due to very slow groundwater movement. But in areas with saline groundwater lying below the upper layer of irrigation leaked fresh water, mobilization of deeper saline water is taking place as a result of pumping by farmers. In addition, results of the solute transport model and MODPATH runs were evaluated in support of water quality analysis and groundwater flow rates. Copyright (c) 2013 John Wiley & Sons, Ltd.