WRRCTR No.138 Water Quality Simulation of Wahiawa Reservoir, Oahu, Hawaii

Abstract

Wahiawa Reservoir is a small multi-use facility located on the central plain of Oahu, Hawaii. The goal of this study was to develop and apply a computer-simulation model of water quantity and quality in Wahiawa Reservoir. The model was used to evaluate alternate water quality management strategies. The model represents the reservoir as a dynamic, one-dimensional (vertical) system. Primary emphasis is placed on representing vertical and temporal changes in water level, water temperature and dissolved oxygen. A unique feature of the model is the inclusion of the effects of artificial aeration. Model calibration was accomplished by obtaining statistically acceptable comparisons between simulated and observed water quality values over a 1-yr interval. Model verification results demonstrated a low predictive accuracy for the model as calibrated. However, the general response behavior of the reservoir is well represented by the model. Examples of using the model to predict effects of alternate management strategies showed that anaerobic conditions depend on oxygen demanding sediments and high algal productivity of surface waters. Artificial aeration appeared to be the most effective water quality management strategy.