Projected Reservoir Rating Curves Based on Sedimentation Surveys and Its Application in Water Planning in Texas

This paper presents a study on sediment in Texas reservoirs and its effect on reservoir firm yield. This study examined the geographical variation of reservoir sedimentation across the State of Texas as well as the sediment distribution inside a reservoir at all depths from streambed to the top of conservation pool. Results indicate that sediment accumulates faster in lower elevations than in higher elevations in most Texas reservoirs but the opposite is true in reservoirs where significant deltaic formations exist. Reservoir elevational sedimentation rates (capacity loss rates) are estimated incrementally at different elevation levels to develop reservoir rating curves according to the vertical distribution of sediment, using the data from hydrographic surveys. Reservoir rating curves for the next 50 years are predicted, assuming a constant sedimentation rate for the prediction period. Based on the predicted rating curves, reservoir firm yields for the prediction periods can be estimated and a relationship between predicted reservoir capacity and firm yield is derived. This provides useful information for water planning in Texas.