MODELING RESERVOIR BANK STORAGE AND THE SOLUTE BUDGET OF THE RIO GRANDE

Past studies on water and chloride mass balance in Elephant Butte Reservoir have suggested that storage takes place in the banks of the reservoir. This implies that as the reservoir level rises some water from the reservoir is temporarily lost to bank storage. This phenomenon could have important implications for predicting the amount of water available in the reservoir as it recovers from record low levels experienced recently.

Using both water and chloride mass balance approaches is helpful in determining the sources and sinks of water in the system. For example, water loss due to evaporation results in increased concentration of chloride in the water in the reservoir, while water loss due to bank storage does not affect the chloride concentration in the reservoir. Therefore, using the chloride mass balance enables the effects of evaporation to be separated out from the water mass balance and allows for a better understanding of the movement of water in the system.

An integrated water and chloride balance model is being developed for Elephant Butte Reservoir using historical data. This model should be able to predict storage and chloride concentration in the reservoir given future climatic conditions and management practices.