An analysis of salt water problems in a coastal estuary

During periods of low flow and high water use on the Neches River, salt water intrudes up the river, endangering the fresh water supplies of the City of Beaumont, Texas, and the Lower Neches Valley Authority. As part of a study for the Galveston District, Corps of Engineers, the author calculated the depth of fresh water available at the City’s intake at Bunns Bluff on the Neches River for various net flows in the river, using the formula developed by Dr. Garbis H. Keulegan for computing the length of an arrested saline wedge. In this thesis the author gathered data on salinities and gross and net flows in the Neches River, and refined and extended the prior calculations. The 28.4-mile portion of the river between the mouth and Bunns Bluff was divided into three reaches and separate computations were made for each reach for net flows varying from 1,900 cubic feet per second to 8,000 cubic feet per second. Additionally, calculations were made for September 11, 1972, using data on the net river flow available that day and vertical salinity profiles by the U. S. Geological Survey at three locations along the lower 28A miles of the river. It was concluded that the formula developed by Dr. Keulegan may be used to approximate the depth of fresh water available at Bunns Bluff under static conditions, provided adequate data are available on gross flows, withdrawals of fresh water, and salinities. The refined method of breaking the lower 28.4 mile portion of the river into three reaches results in a calculated depth of fresh water at Bunns Bluff only about three percent greater than calculated without breaking the river into three reaches, indicating that the proposed refinement is unnecessary. As a subject for further research, it is suggested that additional detailed salinity measurements be made in the Neches River at more frequent intervals, and computations made under dynamic conditions considering tidal effects and other variables.