Integrated water resources management requires demands from agriculture, industry, and domestic users be met with the available supply with full considerations to water quality, cost and the environment. Thus, optimal allocation of available water resources is the challenge faced by water managers and policy makers to meet demands. With this in mind, a new tool called ALL_WATER_gw was developed for groundwater management within the framework of the WEAP-MODFLOW Decision Support System. It takes into account satisfaction of demand, minimization of water cost and maximal drawdown, as well as meeting water salinity restrictions. A Multi-Objective Genetic Algorithm (MOGA) and the PARETO optimality approaches were used to handle the formulated problem. Sensitivity analysis based on a pilot study showed that the MOGA parameters have strong impacts on the efficiency and the robustness of the developed tool. The results also demonstrated the tool's capabilities to identify optimal solutions and support groundwater management decisions.