Identification of potential soil water retention using hydric numerical model at arid regions by land-use changes

Assessment of soil water retention in arid region is an input required parameter in precision water management at large scale. Investigations were carried out in Tanta catchment in the middle Nile Delta, Egypt (30° 45 N, 30° 55 E), where collecting soil samples covered different hydrological soil groups and land-uses. Based on the natural resource conservation service curve number model (NRCS-CN), CN approach was used to investigate the effect of spatio-temporal variations of different land-uses on soil water retention. Potential soil water retention from 1990 to 2015 was reduced by 118.1 m3 per hectare with decreasing cropland area. Urbanization encroachment from 1990 to 2015 was increased by 2.13% by decreasing cropland with 15.3% (5300 ha in 2015). This resulted in losing the potential soil water retention by 625,968.42 m3 water for the whole catchment area. Impact of land degradation was pronounced, where 2.65%, 29.35%, and 1.11% of the initial crop land-use in 1990 were converted to bare soil, fallow, and urban area, respectively in 2015. Implementation of (S) value of the NRCS-CN model with GIS technique provides useful measure to identify land-use changes of potential water storage capacity at catchment scale.