Salt Gradient Ponds: Investment Timing Model

Salt gradient solar ponds can play an important role in management of river salinity in semiarid locations such as the Colorado River Basin. A mathematical model and solution procedure are presented for investment timing of expansion of a salt gradient pond system. An application of the model is presented for several sites in the upper Colorado River basin where planned fossil fuel electric generating plants are located near existing source of saline or brackish water. The concept involves use of both concentrated brine waste streams from the power plants and the existing low quality water sources for the pond system water and salt demands. The salt gradient pond can: (1) Replace a power plant's customary zero discharge evaporation; (2) produce additional energy; and (3) remove much more salt from the river system than the conventional evaporation pond. An economic model solution procedure and application are presented for expansion of salt gradient solar pond systems. Such systems have important potential for salinity management applications, when used in conjunction with thermal/electric plants near sources of saline water.