The Nubian Sandstone Aquifer in the Sinai Peninsula and the Negev Desert

Abstract

The Negev Desert covers about 60% of Israel’s land area. Despite its dry climate, several cross-border regional aquifers, with enormous water storage capacity, exist hundreds of meters below its surface. Among these, one of the main groundwater resources is the Nubian sandstone aquifer (NSA) of the Kurnub Group, stretching between the Suez and the Arava Rift Valleys in the west and the east, respectively. This aquifer is one of several regional Nubian aquifers that underlie the hyper-arid Saharan and Arabian Deserts. The NSA’s great potential in the Sinai–Negev Basin was discovered almost half a decade ago. However, the existence of such a regional aquifer, with high water heads and even artesian flow in places, raised several questions: Where and when has the recharge to the aquifer taken place? What were the climatic conditions under which this area, now characterized by very low precipitation amounts and high evaporation rates, received its significant recharge? Was it a singular massive recharge period or the result of several distinct pluvial epochs? And is the system being recharged even under the present hyper-arid climate? Many studies have addressed these and other fundamental questions, using various techniques and different approaches. This chapter provides an overview of some of the major findings and discoveries obtained across decades of hydro-geological and hydro-chemical research. The main recent discoveries include the following: 1) the long residence time of the groundwater in the confined parts of the NSA, on the order of 104–105 years, and 2) the dominant mixing processes that take place in the aquifer between groundwater masses that were recharged in distinct intake areas of the NSA during different epochs in the Pleistocene. It is concluded that even though some active recharge to the NSA is currently taking place in its limited outcrops scattered over the Sinai–Negev Basin under the present-day conditions of hyper-aridity, the aquifer is largely dominated by paleo-recharge water. Since the NSA was mostly replenished under different climate conditions, as evidenced by its isotopic composition, it can be considered “fossilized.”