Water Quality Modeling Study to Support a Proposed Water Supply Project GoldSim was used to evaluate the feasibility of a water supply project in Canada involving diversion works on a river and water conveyance through pipelines and canals to the headwaters of several creeks. Water would subsequently be made available to the various end-users through existing and proposed canals, natural channels, water supply reservoirs and multi-use projects. Water quality was one of the key issues required to determine the feasibility of the project. GoldSim was used to support a water quality modelling study to assess the suitability of water provided by the proposed project for irrigation use. The model addressed two key water quality parameters that are of particular concern with respect to the suitability of water for irrigation purposes: electrical conductivity (EC) and sodium adsorption ratio (SAR). The model was calibrated to match water balance and water quality data monitored in a reservoir in the project area with multiple years of monitoring data. The calibrated model was then used to predict weekly EC and SAR in surface waters for a continuous 34 year period, allowing water quality to be simulated under varying historical climatic and flow conditions. Results of water quality simulations were subsequently compared with the irrigation water quality guidelines to determine if predicted water quality in the system would be acceptable for irrigation use.