A numerical flow model was developed for the Salalah coastal aquifer using both the MODFLOW computer code and the MT3DMS computer code to assist in the analysis of freshwater flow and saltwater intrusion. The underflow was derived from the developed numerical groundwater flow modelling and calibration on hydraulic heads of 1992. A model-calculated water budget indicates that 51 million cubic metres per year of freshwater recharge the Salalah plain aquifer system, of which 98% of this water is underflow originating from Jabal AlQara, and the remaining 2% is the recharge on the plain. Two baseline scenario simulations were run to calculate the potentiometric surface and salinity distribution for the "business as usual" conditions (no-management interference) of the aquifer for the period 2006 until 2020. Baseline scenario A, assumes "business as usual" and the underflow (constant recharge) to continue the same and baseline scenario B, supposes "business as usual" and the underflow to decrease (changing recharge) at 5% annually. The ef- fectiveness of seven scenarios under each baseline scenario proposed in this work was assessed in comparison with the "business as usual" conditions. The developed simulation model was used to predict the distribution of the po- tentiometric surface, salinity distribution, and mass balance under these proposed scenarios for the prediction pe- riod 2006-2020. The experimental work in Jabal AlQara was linked with the theoretical study of the flow model to optimize the re- charge analytically in order to evaluate the output of the recharge that was obtained by the calibrated flow model. The investigation of fogwater collection demonstrates the importance of the vegetation in Jabal AlQara as a source of subsurface recharge by contributing to the horizontal precipitation. This project estimated that the horizontal precipitation caused by fogwater capture by the Jabal vegetation, contributes to the annual natural recharge by 60% to 80%. The experimental studies on fogwater harvesting in Dhofar demonstrated the importance of vegetation in Jabal AlQara as the main source of the annual underflow to the Salalah coastal aquifer. The extent of tree cover over parts of the Jabal is rapidly declining; in turn water from fogwater collection may decrease. This means that there will be a decrease in the quantities of available water from this source to recharge the aquifers in the Jabal and the Salalah aquifer. Measures have been taken by the government to enhance the sustainability of the Jabal vegetation through the re- duction of the camel population, which, by browsing, threatens the fogwater collecting forest on the mountain crest behind the Salalah plain. In addition, the government (MRMEWR) established a plant nursery in Jabal AlQara (Qai- roon hairriti- about 872 m amsl) to enhance the conservation as a result of transplantation of the indigenous plant species to combat desertification and restore the plant canopy. The ecosystem of the Dhofar region supports more than 750 terrestrial plant species, out of which about 50 are endemic. This study stresses the importance of imple- menting a major programme to enhance fogwater collection. Tree planting in the Jabal grassland is proposed for re- forestation with the principle purpose of causing an increase in fogwater interception to benefit grassland produc- tion and increase the recharge of the Salalah groundwater aquifer. This study investigated the effectiveness of the artificial infiltration, through the application of reclaimed treated sewage recharge, to halt the salinity of the Salalah aquifer using a modelling technique. The study argues that the in- jection scheme is effective in pushing back the saline zone front by 700 metres in 2019.

A numerical flow model was developed for the Salalah coastal aquifer using both the MODFLOW computer code and the MT3DMS computer code to assist in the analysis of freshwater flow and saltwater intrusion. The underflow was derived from the developed numerical groundwater flow modelling and calibra...