| Popis: |
Groundwater in eastern Arabia is commonly associated with relatively flat-bedded aquifer systems in Tertiary marine limestone. However in the Sultanate of Oman, there are a number of unusual flow systems in which large freshwater lenses and plumes occur as discrete bodies within, but separate from the broader aquifer system. Each of the occurrences requires special management considerations as the specifics of the partial flow system, rather than those of the aquifer in genera, determines the nature, extent, and at times, the survivla of the resource. Examples of such occurrences are the large and exceptionally fresh groundwater lenses (TDS 400-160 mg/l) overlying saline regional systems in hyper-arid central Oman. The larger lenses represent modern day recharge, and as such run counter to more conventional wisdom about recharge potential under such adverse conditions. The lenses are a renewable resource but require careful management to avoid upcoming, saline pollution and eventual destruction. A similar requirement occurs on the Al Khawd Fan at the eastern edge of the Batinah, coastal plain of northern Oman where water tables are at or close to sea level, 6 km inland near important wellfields. While the potential for upconing of saline water would appear to be acute, this is less precarious than would normally be the case. High groundwater pressures occurring at depth within the aquifer, generated from upbasin within the regional and intermediate flow systems, counter the inland migration of the intruded seawater wedge and thus partially protect the resource. Westward, on the Batinah, coastal plain, a further type of flow system sees large plumes of groundwater originating from recharge areas high (>2000 m) on the Jabal Akhdar, and then passing across the Batinah plain to the coast. In the case of the Wadi Maawil, the high altitude isotopic signature of the Maawil plume is still present at the coast after crossing the Batinah plain, showing that there is very little low altitude recharge on the plain along the path of the plume. In a more general sense this demonstrates that recharge from precipitation is insignificant on the Batinah coastal plain. The presence of the plume across the deepest part of the Eastern Batinah, an area with the highest groundwater potential in the coastal plain alluvial aquifer, requires special consideration in management of the aquifer. |
