Designing an Effective Groundwater Monitoring Network based on Evaluation of Depth-Stratified Groundwater Salinization in Gaza Strip, Palestine

Abstract

Abstract A chronology evaluation of depth-stratified groundwater salinization and designing an effective Groundwater monitoring network in Gaza Strip, Palestine Groundwater is the main source of fresh water in the Gaza strip. Demand is beginning to outpace supply, and supply itself is being impacted in terms of both quantity and quality. The purpose of this study is to assess salinity phenomenon at sub-aquifers individually for time periods (2009-2011 and 2012-2014) and designing an effective groundwater quality monitoring networks (GWQMN) for each sub-aquifer to get a realistic representation of the salinity phenomenon through the study area. Chloride prediction maps have been generated for salinity assessment using ArcGIS geostatistical analysis tool by applying ordinary kriging method as a measure to salinity phenomenon in the Gaza strip. The existing monitoring networks have been optimized by adding new wells both in areas having the lowest reliability and in possible hot spot areas (e.g., areas of maximum concentration, high variability or uncertain measurements) and neglecting the wells which cause information redundancy based to the results of second time period assessment study. A comparison has been made between the prediction of standard error maps of existing and the prediction of standard error maps of proposed new networks to show a distribution of variation associated with differences between the measured and calculated values as a measure of an error, or uncertainty of the estimated surface. This study showed that all sub-aquifers are facing a huge and accelerated salinization, the percentage of fresh area (Chloride less than 250 mg/l) decreased with time in all sub-aquifers (A, B1, B2 and C) to be (24%, 27%, 10% and 8%) at first time period and (18%, 13%, 7% and 7%) at second time period. The proposed new network showed that the number of the groundwater quality monitoring wells (using Chloride data) in the Gaza Strip can be reduced by average 32.4%. Key-Words: Groundwater quality monitoring network, spatial, standard error; prediction map; redundant information, Gaza Strip.