Estimation of root zone salinity, using saltmod, in the arid region of Turkey

Soil salinity and waterlogging are the two most common problems limiting crop production in irrigated agriculture in southeastern Turkey. Poor water management and irrigation water leakage from the irrigation canals have caused the groundwater table to rise over approximately 35 000 ha of land. There is a need to predict drainage for salinity control in the Harran plain that has been under irrigation since 1995. The objective of this study was to establish the effects of current irrigation/drainage practices on root zone salinity, using SaltMod. Several scenarios like the changes in irrigation depth, water quality, varying drain spacing and drain depth effects on root zone salinity and groundwater table depth were tested. Experimental values showed that the initial average root zone salinity was 9.03 dS m(-1) and decreased to 3.03 dS m(-1) at the end of three years of irrigation seasons. These values were very close to those predicted by the SaltMod model. The measured drain discharge rates in the three test years were 0.099, 0.067 and 0.084 m/season. SaltMod revealed that when the drain depth became 1.40 m, there was no change in root zone salinity for the next 10 years. Copyright (C) 2007 John Wiley & Sons, Ltd.