Keywords: water saving measures, irrigation systems, soil-water-atmosphere-plant model, total water balance, simulation models, Gediz Basin, Turkey
A model approach to evaluate irrigation system water balance: an example from the Gediz Basin, Turkey
An increase in the amount of water used for agriculture has resulted in the need for water savings and measurements in the agricultural sector. With the increasing competition for water, not only should irrigation water be considered, but also an approach encompassing the total water balance is necessary. A clear understanding of all the components of the water balance is essential so as to analyse possible water saving measures. In this study, a one-dimensional physically based soil-water-atmosphere-plant model was applied in a distributed way in order to analyse all the water balance terms of an irrigated area. Methodology and data requirements are described. The results were concentrated on a comparison between a pre-drought and a drought year for Salihli Right Bank Irrigation area in the Gediz Basin, Western Turkey. The whole study area was divided into sub-areas as Land Use Systems, then this simulation model was applied to include the essential parts of the water balance such as soil evaporation, crop transpiration, groundwater recharge, capillary rise, and crop growth as a function of soil water dynamics. It was concluded that the use of existing data in combination with a physically based simulation model is a useful tool to analyse all the components of the water balance of irrigation systems.