Development of Groundwater Model for the Rijam Aquifer/Jafer Basin, Jordan

Rijam Aquifer/Jafer Basin area (1073 km(2)) lies in the southern part of central Jordan plain between 242-279 E longitude and 955-984 N latitude (according to Palestine Grid). Irrigation by pumping groundwater from a shallow unconfined aquifer of Rijam Formation (B4) had been practiced from 1965 up to 1971 when the salinity of the aquifer increased, whereby its yield became unsuitable for irrigation. The sustained yield has been estimated to be less than 2 MCM/Y due to limited recharge through the wadi beds during floods. Consequently, the aquifer balance has been disturbed, leading to a major decline in water level. Therefore, suitable groundwater resource management is required to overcome the problem of overpumping and its effect on groundwater quality. Three - dimensional groundwater flow model (Processing Model Flow for Windows Pro: PMWIN PRO7, 2010) was used in this study in order to calculate the groundwater budget and aquifer characteristics, as well as to predict the aquifer response under different stresses for the next 20 years (2035). The model was calibrated for steady state conditions by trial and error calibration. The calibration was performed by matching observed and calculated heads for the year 1970. Drawdown data for the period 1990-2005 was used to calibrate transient model by matching the calculated heads with the observed ones. Thereafter, the transient model was validated by using the drawdown data for the period 2006-2013. The hydraulic conductivities of the Rijam aquifer system range between 10(-4) and 10(-8) m/sec. The specific yield percentage values ranged between 10% and 15%. The higher values of specific yield appeared in the southern part of the Rijam (B4) aquifer, while the lowest values appeared in the middle of the model area, where the pumping well fields are concentrated..