The Soil and Water Assessment Tool (SWAT) was used to simulate monthly runoff in the Yarmouk River Basin (YRB). The objectives were to assess the performance of this model in simulating the hydrological responses in arid watersheds then utilized to study the impact of YRB agricultural development project on transport of sediments in the YRB. Nine and three years of input data, namely from 2005 to 2013, were used to calibrate the model, whereas data from 2014 to 2015 were used for model validation. Time series plots as well as statistical measures, including the coefficient of determination (R ²) and the Nash–Sutcliffe coefficient of efficiency (NSE) that range between 0 to 1 and −∞ to 1, respectively, between observed and simulated monthly runoff values were used to verify the SWAT simulation capability for the YRB. The SWAT model satisfactorily predicted mean monthly runoff values in the calibration and validation periods, as indicated by R ² = 0.95 and NSE = 0.96 and R ² = 0.91 and NSE = 0.63, respectively. The study confirmed the positive impact of soil conservation measures implemented in the YRB development project and confirmed that contouring can reduce soil loss from 15 to 44% during the study period. This study showed that the SWAT model was capable of simulating hydrologic components in the drylands of Jordan.

Soil moisture conservation and combating soil erosion on agricultural fields are the highest priorities for crop production in arid lands. In this research, the effect of land application of rock fragments on runoff, soil loss, and vegetative cover on a silt loam soil has been tested under natural rainfall conditions. Field plots of 2 m wide by 10 m long were prepared in two locations with a deposit installed at the downstream end of the plots to collect runoff and sediments after each storm during the 2004/2005 winter season. Three treatments were used in the experiments in duplicates including plots covered with 5% and 15% stone and a control. Experimental results showed that rock fragments were highly effective in reducing runoff and soil loss. Runoff depth from plots covered with rock fragments at a rate of 5% and 15% was reduced by 17% and 30% compared to the control, respectively. The corresponding reductions in soil loss for both stone treatment levels were as high as 35% and 53%, respectively. The average soil moisture measured at the center of the plots during the entire season was always higher for stone treated plots and increased with stone coverage percentage compared to control. Consequently, vegetative cover was higher in the plots with 5% rock fragments cover. For higher stone coverage of 15%, rock fragments occupy more soil surface area and, therefore, reduce the space available for vegetation.

A field study was conducted to evaluate the potential of rooftop rainfall harvesting (RRH), determine the smallest tank volume and the potential contribution of RRH to the national water budget. The potential water volume from rooftops nationwide is 14.7 million cubic metres per year (MCM/year), which comprises 6% of the domestic national water budget. Public water supply rates decreased for areas practicing RRH. The number of underground tank (cisterns) increased in high rainfall areas indicating adaptation behaviours for securing water. Smallest cistern volume charts were constructed for each governorate in relation to consumption rate and rooftop area. An immediate and nationwide awareness and legislative programmes are needed to spread RRH among the whole population of Jordan.