Return flows- impact on the Texas Bay systems.
Masch, F.D., Jr.
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Return flows were developed from population projections, resource availability, water uses, and wastewater releases. Estimates were made in terms of river basins, zones, and areas contiguous to six selected bay systems. Detailed ecological descriptions and exchange estimates were prepared for five of these bays. The study involved a search of existing ecological information, the development of an approximate physical exchange model, and the use of a biological degradation model. These mathematical models were selected to provide estimates of the dissolved oxygen content under various conditions of inflow. Approximately 1.8 million acre-feet of wastewater are produced each year from the non-saline water used by municipalities and industries in Texas. More than two-thirds of the total municipal and industrial return flow produced in Texas passes through one or another of the bays on its way to the Gulf of Mexico. Of this amount about two-thirds of the return flow passing through the bays is derived from municipalities and industries located directly on the bays by way of natural watercourses. It is estimated that the direct contribution to each of the bays will increase in the future at a slightly higher rate than will the tributary contribution. There is a wide variation in the quality of the direct contribution of return flow to each bay, but the tributary contribution tends to be much more uniform in quality. The concentration of dissolved oxygen in a bay is generally the most reliable index of the overall condition of the bay. Therefore, one of the major efforts of this study was directed toward the development of mathematical models by means of which the dissolved oxygen level can be evaluated for both present and future loading conditions.