Applicability of Horton model and recharge evaluation in irrigated arid Mesopotamian soils of Hashimiya, Iraq

The drawbacks of Horton model for infiltration potential estimate in arid regions are a serious problem the hydrologists are facing. Horton model is inapplicable in regions of initial rainfall intensities less than initial infiltration capacity of soils as basically outlined by Horton. Four infiltration models including Horton are adopted to evaluate their validity for infiltration potential estimate namely as Horton, power, polynomial, and mixed fitting models. Infiltration field measurements by double ring infiltrometer, and geotechnical investigations for soils to estimating infiltration rate, specific gravity, and bulk density were conducted at Hashimiya area of 110 km 2 . The entire area was divided into nine administrative sectors namely as Jerboeyia, Hashyimia, Niwedra, Tebra, Sada, Zineyia, H3, Fayadhiya, and Bazul due to spatial hydrology. Geologically, the area consists of Mesopotamian plain which comprises the recent river sediments of Tigris and Euphrates, which consists of silts and clays and stacked river channel sands with occasional marsh deposits. The power model offers best fit to the measured infiltration with correlation coefficient of 0.996, whereas polynomial, mixed fitting, and Horton models offer 0.947, 0.958, and 0.84 respectively. Moreover, Horton model offers less infiltration potentials for both dry and wet seasons of 3 and 1 mm/day causing a rise in the average groundwater levels equal to 8.4 and 2.8 mm/day respectively. Similarly, the average infiltration potentials estimated by power model for both dry and wet seasons were 3.55 and 1.19 mm/day to rise in the average groundwater levels 9.88 and 3.31 mm/day respectively. These models create a paradigm for hydrology and environmental sustainability.