field measurements in the sadah area showed significant differences in transmissivity table which reflect the variations in the hydraulic permeability and thickness s also the wide range of values for storativity reflects the variability of the confining pressure due to differences in lithology and thickness of both the aquifer and the overlying formations particularly toward the southeastern edge of the system however direct and indirect recharge has been reported in the southern sadahnajran area where average rainfall is mmyr in yemen it is estimated that a total recharge natural sources plus irrigation return of mcmyr occurs in this escarpment zone which is equivalent to mmyr although lower mmyr mmyr values have been suggested