Modeling water, heat, and oxygen budgets in a tidally dominated estuarine pond

We present a methodology to model water, heat, and dissolved oxygen budgets on short time scales within a shallow estuarine environment using limited local water quality and climatic data. A tidally restricted eutrophic pond in Elkhorn Slough, California, experiences extreme diel dissolved oxygen (D O) variations during warm sunny days and neap tidal cycles. Empirical relat ionships between biological metabolism (measured as DO variations) and phys ical parameters are derived using time-series hydrographic data from the si te. A simple box model predicts the time-series structure of water depth, w ater temperature, and DO concentrations within the pond as a function of th e tidal cycle and local climate over 10 to 15 d simulation periods. Paramet ric analyses illustrate applications of the model to predict thermal and ge ochemical responses to hydrologic, chemical, and climatic alterations to th e system. This study also initiates preliminary investigations of the funda mental processes influencing DO dynamics within a natural wetland environme nt, and could be used to explore the potential response to various physical and chemical alterations prior to restoration or management adjustments. F uture box models of wetland geochemistry should include carbon and nutrient budgets to create a more sensitive model, and to allow more rigorous evalu ations of the role decreased nutrient inputs would play in alleviating eutr ophic conditions.