Evaluation of water productivity in the saline areas of lower karkheh basin and determination of its causes : a study from southern Iran

Karkheh River Basin (KRB) is one of the important basins in Iran regarding water resources, where both rain fed and irrigated agricultural production systems prevail. Water logging and soil salinity are the major threats to water productivity and sustainable agricultural production in the lower KRB (L-KRB). More than 78% of agricultural production in Dasht-e Azadegan region is dominated by grains, mainly wheat and barley. The main objective of this research was to determine and evaluate water productivity (WP) of irrigated wheat, as major cultivated crop in DA and recommendation of simple and applicable management guidelines. This research was conducted in fourteen farmers’fields, typical of the farms in the region, during cropping season of two years 2005-2006 and 2006-2007. Based on the total applied water, calculated Evaporation- Transpiration (ET), and crop yield, wheat water productivity values were calculated and determined. Analysis of measured Water Productivity (WP) indicated that the range of variation in WP values is relatively high and varies between 0.1-2.1 kg.m-3 In the southern parts of L-KRB, mainly in Dasht-e Azadegan plain (DA), available data show that the problem of soil salinity is magnified due to lack of farmers’ knowledge, inadequate drainage networks, and absence of improved farming practices. In general, the main cause of soil salinity in the L-KRB is high water table, usually varying between 1.2-3.0 m below the soil surface. Evaluation of results indicates that, inefficiencies and the limiting factors affecting WP in southern part of L-KRB.