Water Harvesting for Improving Rainwater Use Efficiency Using GIS: A Case Study, Tigris River Basin, Iraq
Abstract
The distribution of rainfall in dry areas, such as Iraq, is extremely erratic. The rainfall is mostly limited to occasional, intense, and unpredictable storms with high surface runoff and uncontrolled gullies and rills flowing on soils with low infiltration rates, and then it is collected at the end in wadis. Thus, most of the rainwater is lost as evaporation if not harvested. The objectives of this work were to explore the promising water harvesting areas of the Tigris River Basin (TRB), evaluate the amount of harvested rainwater from the river basin in Iraq, and then how to improve rainwater use efficiency. The GIS technique was utilized to examine the hydrological characteristics of the basin and locate the rainwater harvesting sites. The volumes of the harvested water (runoff) were assessed utilizing the SCS-CN method. The results showed that about 70% of the river basin inside Iraq is suitable for rainwater harvesting with a total annual runoff of 324 BCM. The results demonstrated that the harvested rainwater use efficiency ratio increases with the increasing amount of the used water or the relative water protectivity per unit area. The paper presented some suggestions and recommendations for improving rainwater use efficiency in the catchments of the TRB within Iraq.