Determination and Evaluation of Water Productivity in the Saline Areas of Lower Karkheh River Basin

Karkheh River Basin (KRB) is one of the important basins in Iran regarding water resources, where both rainfed and irrigated agricultural production systems prevail. Waterlogging and soil salinity are the major threats to water productivity and sustainable agricultural production in the southern parts of lower KRB (L-KRB). In the southern parts of L-KRB, mainly in Dasht-e Azadegan plain (DA), available data and surveys show that the problem of soil salinity is magnified due to lack of farmers' knowledge and skills, inadequate drainage networks, and absence of new and improved farming practices. In general, the main cause of soil salinity in the L-KRB is high watertable, usually varying between 1.2-3.0 m below the soil surface. More than 78% of agricultural production in Dasht-e Azadegan region is dominated by grains, mainly wheat and barely. 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 for better management of irrigation and amelioration of salinity-waterlogging hazards on crop yield and WP. The research was conducted in fourteen farmers' fields, typical of the farms in the region, during cropping season of two years 2005-06 and`2006-07. Based on the total applied water, calculated ET, and crop yield, wheat water productivity values were calculated and determined. Analysis of measured WPs indicated that the range of variation in WP values is relatively high and varies between 0.1-2.1 kg.m-3. Evaluation of results indicate that sources of inefficiencies and the limiting factors affecting WP in southern part of L-KRB have combined effects and can be classified into four main categories as: Socio-cultural problems governing the region leading to low motivation for investment in irrigation management and on-farm improvement activities by the farmers; limitations that are out of farmer's management control and authority, e.g., irrigation intervals and rationing, and shortage of agricultural inputs (fertilizers, other agrochemicals, machinery, etc), technical and infrastructure limitations and problems (e.g., inadequate drainage and reclamation, and incomplete irrigation and drainage networks) that need extensive planning and investments and should be supported by the government; managerial problems and limitations whose solution is simple and do not need much investment and can be accomplished easily.