The Ilisu Dam is part of the Turkish Southeastern Anatolia Project (GAP) and is the largest dam on the Tigris River in Turkey. It is located on the main river course 65 km upstream of the Syrian and Iraqi border. The Ilisu Dam watershed is the same as that of the Mosul Dam in Iraq. Sharing the same watershed with the Mosul Dam and located upstream, the Ilisu Dam will usurp most of the watershed and deprive the Mosul Dam of most of its current inflow. This paper presents an assessment of the hydrological impact (basically predicts changes on future inflow) of the Ilisu Dam on the Mosul Dam. The assessment is based on the worst-case scenario. The analyses that are employed include geographic information system (GIS) techniques and regression models, along with statistical analyses to numerate expected future impacts on the Mosul Dam’s inflow distribution. Results reveal that the Ilisu will have a drastic impact on the inflow regime of the Mosul Dam. A reduction as high as 78% of the inflow of the Mosul Dam may occur if the operation of the Ilisu and the Cizre Dams is conducted with no consideration of downstream hydrological and environment impacts.

Large amounts of runoff is generated in western Iran and flows into eastern Iraq due to relatively intensive rainstorms along the international border line. Currently, most of this runoff is being wasted by evaporation instead of being stored and preserved for later uses. This paper is an attempt to (1) assess and harness the water resources of eastern Iraq, and (2) propose a storage scheme to use the harvested water in the water shortage times. The runoff of eight catchment areas (Mandali, Qazania, Tursaq, Mirzabad, Galal Badra, al-Chabbab, al-Teeb, and Dwaireeg) is estimated using regression equations derived for areas in the western and southern parts of the United States of America. Several models were selected from two states based on catchment area location, average terrain elevation, average annual precipitation, and slope of main stream. Observed runoffs of Tursaq, Galal Badra, and al-Chabbab streams are analyzed using normal probability plots. Statistical analysis shows that there is no a statistically significant difference between observed and predicted runoffs for different return periods. The study proposes a water reservoir to be constructed within al-Shiwiaja Marsh to accommodate runoff generated within Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra streams. The capacity of the proposed reservoir is 3000 Mm³ and the expected inflow from these streams is projected to exceed the capacity of the reservoir. The proposed reservoir will contribute to the flow of the River Tigris during the non-rainy seasons. More studies are needed to propose and design a storage scheme for two remaining streams (al-Teeb and Dwaireeg).