A methodology is presented for water quantity and quality assessment for wetland development which enables planners to evaluate the results of restoring and managing a large wetland complex based on a set of criteria developed under multi-disciplinary guidelines. The methodology includes addressing temporal and spatial variability of climatic data for determination of wetland water requirements; determination of wetland evapotranspiration; determination of critical areas for wetland and agricultural development using GIS; modelling the water delivery ystem (quantity, quality, location, and timing) of a wetland complex using HEC-5 and WASP; and water management using the GAMS/MINOS optimization program. The methodology is applied through the use of a Decision Support System (DSS). The goal of the DSS is to provide tools for spatial and temporal simulation, evaluation and management of a wetland system. The user has access to a common analysis environment consisting of models and data within a Graphical User Interface (GUI). Simulation and optimization modules, combined with a graphical user interface, permit efficient and convenient study of various resource management scenarios.