The Effects of Agricultural Expansion on Regional Hydrology in Southeastern Turkey

The goal of this research is to determine the water resource impacts of land use and land cover change (LCLUC) that are occurring as part of the large-scale water development and irrigation projects in semi-arid southeastern Turkey. Our approach is a multidisciplinary research program involving change detection analysis using Landsat imagery, statistical analyses of long-term meteorological and river discharge observations, application of models of evaporation specifically suited to changing soil moisture supply, and simulation analyses with a meso-scale climate model. To address the issue of LCLUC impact on water balance partitioning, each of these tasks will be integrated into a framework based on the complementary hypothesis for evaporation estimation first put forth by Bouchet (1963). Together, the research has the objective of answering the following three important questions: i) How has the irrigated area changed over the course of the last 10 years? ii) What is the impact of this irrigation on the regional hydrology? and iii) What is the long-term impact of this irrigation both on hydrology and regional climate as simulated by a regional climate model? The proposed research has important implications for water budget estimates, a keystone for sustainability of water resources, and could quantify whether economies of scale of water resource exist due to scale dependencies of physical water balance mechanisms. Main accomplishments during the first year are: 1. Development of baseline and irrigated lands maps with categories representing the extent and distribution of irrigated area on a two-year basis between 1990-2001. This map forms the basis of change analysis involving expansion of irrigation. 2. Building of a 26-year climate dataset with critical meteorological parameters with data purchased from Turkey. This dataset, coupled with areal estimates of irrigated area, allows us to test our hypothesis of changing water-partitioning patterns between the surface and the atmosphere as a result of LCLUC. 3. Preliminary analysis of climate dataset to find trends in moisture status in the region. Work during the second year will include: - Converting of irrigated area estimates into water usage with the help of our Turkish collaborators - Implementing the Bouchet – Morton Hypothesis on areal evapotranspiration using climate dataset from Turkey and irrigated area estimates from remote sensing to understand the LCLUC impacts on water balance partitioning, specifically the impacts on evapotranspiration.