Impact of Agricultural Pract ices on Groundwater Sal ini ty

Suarez, D.L., 1989. Impact of agricultural practices on groundwater salinity. Agric. Ecosystems Environ., 26: 215-227. The impact of agricultural practices on water quality has been examined predominantly with an emphasis on surface water. Impacts on groundwater, as compared with surface waters, are much more difficult to quantify. This is due to larger travel times to and in groundwaters as compared with surface waters and difficulty in sampling groundwaters properly. Despite these difficulties in quantification, the impacts on groundand surface waters are equally important. In non-irrigated areas agriculture often leads to increased recharge, sometimes resulting in the leaching of salts from the unsaturated zone into groundwater. In irrigated areas groundwater salinization can result from irrigation with saline water, salt water intrusion owing to pumping of groundwater, downward movement of salts in the unsaturated zone or dissolution of saline minerals, and from the unavoidable concentration of salts owing to plant water uptake. The interrelationship of surface and groundwaters must involve water quality as well as quantity. Optimization of water resources entails consideration of conjunctive use, which in turn requires consideration of water quality in all parts of the system. In this paper examples are given showing how improvements made to reduce river salinity can cause groundwater salinization, which may not represent the optimum management strategy.