Research Ont He Rational Exploitation And Utilization Of Grouundwater Resources In Wadi Bay Area In Libya

Libya is located in northern Africa, which is the world-famous desert country. The Sahara desert provides Libya with rich petroleum resources. The dry weather conditions make surface water resource extremely lacking, so the groundwater water resource becomes the most important supply source to Libya. Since 1960s, to satisfy the northern coast of economy and agricultural development, in addition to lacking of understanding about groundwater circulation rules and sustainable use of water resources, groundwater was suffered from excessive pumping, which cause the aquifer exhaustion and seawater intrusion to coastal areas, and also make water quantity and water quality into a crisis. Libya government began to research the northern coast of the rational development and utilization of the limited groundwater resources to understand and solve these water environment geology problems. Therefore, this article takes the Wadi Bay region in northern Libya as an example, analyzing the current development of groundwater resources and the regional groundwater circulation characteristics, using of underground water in numerical simulation technology for the rational development and utilization of groundwater resources. This study not only provides theoretical guidance to economic and agricultural development, but also has important practical significance for the sustainable utilization of water resources and water environment calamity prevention and control for Libya.Based on the systematic analysis of geological and hydrogeological conditions of Wadi Bay, this paper analyzes the lithology and structure of formation, aquifer distribution and groundwater system. Eocene limestone shallow aquifer and early cretaceous KiKlah sandstone deep aquifer were chosen as the main research object. Groundwater recharge, runoff and discharge conditions were analyzed, combining study area special meteorological and hydrological characteristics of groundwater system. According to the geological profile and deep drilling material of study area, three-dimensional geological structure model of Wadi Bay was built using GMS software. This model can shows aquifer and formation from different angles and profile. On these basis, the boundary conditions of aquifer, hydraulic characteristics were generalized, and the groundwater system of study area were generalized as heterogeneity isotropic three-dimensional groundwater unsteady flow, at the end, the hydrogeological conceptual model was established.According to the spatial distribution of TDS,the groundwater chemical types, and the spatial evolution of major ions in groundwater found that the TDS and major ions content decreases with the the distance from the sea increased.Then used piper diagram,descriptive statistics,the ratio coefficient of the main ions and isotopic methods to analysis the evolution of the Hydrogrochemistry of Groundwater.The main reason of hydrochemical mutation of shallow groundwater is affected by ancient salt water; the rapid rise of the ions in the vicinity of 50 km offshore is affected by the mixing between Groundwater and modern seawater.Based on the above research, the author built the numerical model of groundwater flow systems, using Visual MODFlow to solve the model.Then calibrated the paremeters to determine the reasonable partition of hydrogeological parameters and parameter values. Then selected the Hydraulic Conductivity, specific yield and the coefficient of rainfall infiltration as parameters to analysis the sensitivity, he results showed:the Hydraulic Conductivity is the most sensitive.The water quantity balance of aquifer was analyzed base on the modeling results, which showed that both shallow and deeper aquifer were both negative balance. Modified hydrological parameters of the numerical model were occupied to calculate the water quantity of research area. Therefore, pearsonⅢcrave was used to compute the recharge amount of precipitation infiltration on an annual average basis in different conditions that precipitation rate were 25%, 50%.75%,95% respectively. The calculation results indicated that the average recharge amount of groundwater was 1.67×105m3/d, the average exploitation amount of shallow and deeper aquifer ware 3.37×104m3/d and 3.56×104m3/d respectively. Through the analysis of the potential of exploitation, it was clear that the overexploitation of the shallow aquifer was quite serious and the same threat would rise in the deeper aquifer.According to the established numerical model of groundwater flow, there were three groundwater exploitation programs had been developed, and forecasted the groundwater flow field of different mining schemes in the next ten years. In the conditions of the expansion of exploitation quantity (scheme 1) and the current exploitation quantity (scheme 2), both shallow and deep groundwater table decreased continuously, the cone of depression of the original deep groundwater expanded gradually, and a new cone of depression of groundwater occurred in study area. Reduced the exploitation quantity was equal to the allowable withdrawal (scheme 3), the downrange of shallow and deep groundwater depth declined significantly, the holistic groundwater level kept stable or increased slightly. But the water table which was in the concentration exploitation area showed a slight downward trend in the forecast period. The reason for the exploitation wells were distributed over-intensive, so that local water resources were due to a negative balance. Reasonable utilization and conservation of groundwater was presented according to the modeling results.