The Impact of Meteorological Drought on Rainwater Harvesting in Al-Khoser Basin, Iraq

The relationship between rainfall and runoff is complex and directly related to human life, plants, and animals and their whereabouts. Modeling this process requires a suitable hydrologic model to determine accurate results, such as volume and peak discharge of runoff, that can be adopted in the planning and management of water resources. Many factors affect the quantities of surface runoff that can be saved, including climate change and drought. In this study, HEC-HMS was used and calibrated to estimate the runoff volumes and peak discharge for (1986–2018). The initial and constant methods were considered and used to account for the precipitation loss. Snyder's unit hydrograph (UH) was the transform method. Drought characteristics can be analyzed by calculating the severity and duration of drought using the Modified Chinese Z Index (MCZI). The results showed the possibility of applying a rainwater harvesting system to achieve an abundance of water that compensates for the water scarcity in the study area. The seasonal surface runoff ranged from 1361.3-19706.8 (×103 m3) during the study period (1986–2018). Regarding the drought intensity, the region experienced its most severe period in 2007–2008, with a rate of 4.63, followed by 1998–1999 at a rate of 2.48. Both are classified as extreme drought. The study revealed that certain years had a higher intensity of drought and resulted in better water collection than other years when the area was affected by drought.