51-IMPASSE - A Field Scale Decision Support System for Impact Assessment and Management of Saline-Sodic Waters on Irrigated Agricultural Lands

Abstract

Saline ground waters pose a continuous threat to sustained irrigated agriculture in many arid and semi-arid regions. Appropriate decisions on the use of poor quality irrigation waters requires the ability of a decision maker to predict long term impacts of different conjunctive water use plans on soil salinization/sodification and crop yield reductions. Conjunctive use of saline and non-saline irrigation waters is generally aimed at minimizing yield losses and enhancing flexibility of cropping, without much alteration in the farming operations. Strategies available include blending and cyclic use of non-saline/saline waters. The pros and cons of such options have been discussed at length. However whether a farmer has to make alterations in his conjunctive water use plans during both Kharif and Rabi seasons or during only one of the growing seasons has not been widely tested under similar conditions. Long- term field experiments are the conventional means for developing suitable conjunctive water use plans. However these are site specific, expensive and time consuming. Appropriate decision support tools provide a time-efficient and cost-effective means for such long-term impact evaluations. This study illustrates the development, validation and application of one such field scale, user-friendly decision support system named IMPASSE (IMPact Assessment & management of Saline/Sodic Environments). The DSS has been extensively tested and validated on several farms and controlled experimental fields in Gurgaon and Kamal districts of Haryana. The average relative wheat yield reductions due to salinity, under various saline water-irrigation treatments, could be realistically simulated by the DSS. Proposed DSS based long-term (2001-2010) impact assessments of existing and alternative conjunctive water use strategies, during both Kharif and Rabi seasons, showed that a change in the conjunctive water use plan during just Rabi season could fetch 3-4% higher annual long term returns to the test farmer.