Ground water evaluation and cooling before utilization for Wadi Zam-Zam, Libya

Abstract

Agricultural development through irrigation is a major effort in Libya. One of the areas being developed is the Wadi Zam-Zam. The Zam-Zam project water supply is entirely deep ground water with essentially no local recharge. The supply aquifer is artesian with an average pressure head of 65 m above land surface and a temperature of 56°C. The water must be cooled before application to crops. In order to maintain sufficient pressure to keep a constant supply, the number of wells and discharge must be limited. Other ground water aquifers may be developed to supply an additional resource to fulfill agricultural needs. Water quality analysis indicates that corrosion should not be a problem other than perhaps steady corrosion when the wells are closed. Considering the total dissolved solids and other criteria, water quality can be classified as good for irrigation. Water temperatures can be lowered by cooling ponds or cooling towers. An unlined cooling pond is less expensive than a cooling tower, but requires higher water consumption. Therefore, based on design assumptions, a mechanical draught tower may be considered more efficient than a cooling pond.