A Regional Hydroclimate Model for Water Resources Management of the Tigris-Euphrates Watershed

In order to establish a basin-wide water management plan for the Tigris-Euphrates (TE) watershed it is necessary to perform rigorous water balance studies of the whole watershed at least for critical historical drought and flood conditions, and under various water resources development scenarios. Performance of such water balance studies over the watershed requires climatic and hydrologic data sets, corresponding to historical critical flood and drought periods, at fine time and spatial grid resolutions in order to provide the necessary hydroclimatic information. Due to various political reasons in this region, such historical climatic and hydrologic data over this watershed are not available internationally at the desired fine time-space coverage that is necessary for performing reliable water balance studies over the watershed. Reconstruction of such climatic and hydrologic data sets requires, a) the development of a regional hydroclimate model for the watershed in order to reconstruct the historical climatic and hydrologic data; and 2) the development of a hydrologic model in order to reconstruct the historical streamflows within the whole watershed. In order to downscale large scale atmospheric datasets over the Tigris-Euphrates (TE) watershed and to reconstruct the above-mentioned climatic and land hydrologic data sets, the nonhydrostatic Fifth Generation Mesoscale Atmospheric Model (MM5) of NCAR was coupled with the physically-based land hydrologic component of Integrated Regional Scale Hydrologic-Atmospheric Model (IRSHAM), and implemented to the TE watershed as its Regional Hydroclimate Model (RegHCM-TE). Since snow is the main source of water for TE watershed, a physically-based energy balance snow model was implemented to the watershed for the reconstruction of historical snowpack evolution and snowmelt processes. In order to route the flows and reconstruct historical streamflow data over the Tigris-Euphrates river network, the HEC-HMS (Hydrologic Modeling System) model was constructed over the watershed. Near the downstream end of Tigris-Euphrates river network, a marshland hydrologic model was also developed for the Euphrates and Tigris marshlands. The RegHCM-TE and the basin scale hydrologic model for Tigris-Euphrates watershed will be described, and the reconstruction of historical climatic and hydrologic data over the watershed by means of these models will be presented.