Water Budget Assessment for a Typical Watershed in the Karak Plateau, Jordan

Adequate assessment of water resources in arid and semiarid watersheds is essential for several purposes, such as the evaluation of biotic potentials for agricultural and grazing practices and for designing water dams. The water balance components of the watersheds in these environments are poorly understood due to the lack or the total absence of hydro-meteorological measurements. Simulation models would more likely fill this gap and can be applied to gauge these resources. The present investigation implements a physically based model with relatively fine spatial and temporal resolutions to examine the water budget components in the Numera catchment, a typical medium sized watershed draining the southwestern parts of the Karak Plateau. The model was able to reproduce the energy balance components adequately, and the results compared favorably well with the observed data. Simulated results of the various water budget components are comparable to those obtained in similar environments. The average annual blue water fluxes (surface runoff and deep recharge) in this catchment is calculated to be ~ 3.3 million m3 during the simulation period, 1996/1997 through 2001/2006. Blue water fluxes are generated primarily in the highlands of the watershed where relatively ample precipitation occurs. Steep terrains with limited vegetation cover experience significant runoff, implying the production of large quantities of sediments. The substantial sediment yield from these landscapes has serious adverse consequences on water quality and the life spans of dams constructed over these watersheds. It is imperative, therefore, that the sediment control via watershed management e.g., terracing, grazing control, preservation of native plants) be specified as a mandatory measure before constructing any dams over these watersheds.