A simulation/optimization approach to manage groundwater resources in the Gaza aquifer (Palestine)

Gaza aquifer is the main source of water for supplying agriculture, domestic, and industrial purposes in the Gaza Strip. Recently, the rapid increase on water demand to fulfill the needs of the continuous population growth made the aquifer overexploited, leading to huge crises of water scarcity and contamination by seawater intrusion. To relieve and narrow the huge deficit between water demand and supply, the use of artificial resources, such as stormwater and reclaimed wastewater, has been investigated. To manage sustainable aquifer development under effective recharge operations and water quality constraints, a decision support system based on a simulation/optimization (S/O) approach has been developed and applied to the Gaza coastal aquifer. The S/O approach is based on the coupling of the density-dependent variably saturated groundwater model CODESA-3D with the Carroll's FORTRAN Genetic Algorithm Driver. The optimization model incorporates two conflicting objectives using a penalty method: maximizing pumping rates from the aquifer wells while limiting the salinity of the water withdrawn. Two aquifer management models (with and without artificial recharge) have been considered for the inner region of the coastal aquifer within a 1 year time interval. Results of the no-injection optimization model identified the optimum spatial distribution of pumping rates at the 16 control wells, showing an average increase of 0.11 m (+9.2%) in water table levels and a marked decrease of 65% in the total extracted salt mass, while keeping the 99% of total abstraction, with reference to current non-optimized conditions. Results of the mixed injection-pumping optimization model identified optimum recharge locations among 9 configurations (3 different spatial locations and 3 rates of 0.5, 1 and 1.5 Mm3/year, respectively) and the spatial distribution of pumping rates at the wells, allowing to withdrawal the 95% of the total current pumping rate, while lowering the total extracted salt mass up to 25% and increasing water table levels in a range of 0.15-0.49 m, with reference to current non-optimized conditions. The last model allowed also to increase up to 20% the total pumping rate, while keeping the total extracted salt mass under 50% of current values with relatively stable water table levels. Further development is foreseen to extend the result to the whole aquifer system, including also economic costs into the multi-objective management model

A simulation/optimization study to assess seawater intrusion management strategies for the Gaza Strip coastal aquifer (Palestine)

Seawater intrusion is one of the major threats to freshwater resources in coastal areas, often exacerbated by groundwater overexploitation. Mitigation measures are needed to properly manage aquifers, and to restore groundwater quality. This study integrates three computational tools into a unified framework to investigate seawater intrusion in coastal areas and to assess strategies for managing groundwater resources under natural and human-induced stresses. The three components are a three-dimensional hydrogeological model for density-dependent variably saturated flow and miscible salt transport, an automatic calibration procedure that uses state variable outputs from the model to estimate selected model parameters, and an optimization module that couples a genetic algorithm with the simulation model. The computational system is used to rank alternative strategies for mitigation of seawater intrusion, taking into account conflicting objectives and problem constraints. It is applied to the Gaza Strip (Palestine) coastal aquifer to identify a feasible groundwater management strategy for the period 2011–2020. The optimized solution is able to: (1) keep overall future abstraction from municipal groundwater wells close to the user-defined maximum level, (2) increase the average groundwater heads, and (3) lower both the total mass of salt extracted and the extent of the areas affected by seawater intrusion

A Simulation/Optimization approach to manage groundwater resources in the Gaza aquifer (Palestinian Territories) under climate change conditions

The Gaza aquifer is the main source of water for agricultural, domestic, and industrial uses in the Gaza Strip. The rapid increase on water demand due to continuous population growth has led to water scarcity and contamination by seawater intrusion (SWI). Furthermore, current projections of future climatic conditions (IPCC, 2007) point to potential decreases in available water, both inflows and outflows. A numerical assessment of SWI in the Gaza coastal aquifer under climate induced changes has been carried out by means of the CODESA-3D model of density-dependent variably saturated flow and salt transport in groundwaters. After integrating available data on climatology, geology, geomorphology, hydrology, hydrogeology, soil use, and groundwater exploitation relative to the period 1935-2010, the calibrated and validated model was used to simulate the response of the hydrological basin to actual and future scenarios of climate change obtained from different regional circulation models. The results clearly show that, if current pumping rates are maintained, seawater intrusion will worsen. To manage sustainable aquifer development under effective recharge operations and water quality constraints, a decision support system based on a simulation/optimization (S/O) approach was applied to the Gaza study site. The S/O approach is based on coupling the CODESA-3D model with the Carroll’s Genetic Algorithm Driver. The optimization model incorporates two conflicting objectives using a penalty method: maximizing pumping rates from the aquifer wells while limiting the salinity of the water withdrawn. The resulting coastal aquifer management model was applied over a 30-year time period to identify the optimum spatial distribution of pumping rates at the control wells. The optimized solution provides for a general increase in water table levels and a decrease in the total extracted salt mass while keeping total abstraction rates relatively constant, with reference to non-optimized conditions

Modeling of seawater intrusion in a coastal aquifer of Karaburun Peninsula, western Turkey

Seawater intrusion is a major problem to freshwater resources especially in coastal areas where fresh groundwater is surrounded and could be easily influenced by seawater. This study presents the development of a conceptual and numerical model for the coastal aquifer of Karareis region (Karaburun Peninsula) in the western part of Turkey. The study also presents the interpretation and the analysis of the time series data of groundwater levels recorded by data loggers. The SEAWAT model is used in this study to solve the density-dependent flow field and seawater intrusion in the coastal aquifer that is under excessive pumping particularly during summer months. The model was calibrated using the average values of a 1-year dataset and further verified by the average values of another year. Five potential scenarios were analyzed to understand the effects of pumping and climate change on groundwater levels and the extent of seawater intrusion in the next 10 years. The result of the analysis demonstrated high levels of electrical conductivity and chloride along the coastal part of the study area. As a result of the numerical model, seawater intrusion is simulated to move about 420 m toward the land in the next 10 years under “increased pumping” scenario, while a slight change in water level and TDS concentrations was observed in “climate change” scenario. Results also revealed that a reduction in the pumping rate from Karareis wells will be necessary to protect fresh groundwater from contamination by seawater.Scientific and Technological Research Council of Turkey (TUBITAK 113Y042