The Use of Hydrograph Analysis to Evaluate the Groundwater Contribution to Tigris River Flow at Mosul City

The flow regime of the River Tigris has been studied during ten successive years from 1975 - 1984. The annual hydrographs of the river were analyzed to determine the ground water components by considering the general form of the river regime, and the minimum flows during recession. Master recession curve was derived from the river flow records of the studied catchment area by combining the characteristics of various recession records, and used to check the separation of components contributing to the river flow and also indicate the number of aquifers involve in contributing the ground water to the river. Four major aquifers outside the study area and within the Turkish territory appeared from the analysis contributing ground water of about 58% to 75% percent of the total flow during the ten years period. The total volume of water in storage from the beginning of recession was also determined along the ten years and was varying between 1.0 x 109 – 6.0 x 10 9 m3/ year.