An evaluation of water constrained growth pattern in the Arroyo Colorado River Watershed, Texas

The broad goal of this study was to develop optimization based methodologies to estimate waste load allocation and evaluate subsequent load redistribution policies in the Arroyo Colorado River Watershed. The decision support system consisted of a simulation model which explicitly modeled the BOD and DO assimilation in the wastewater treatment plants as well as in the non-tidal river reaches. Three different policy scenarios were evaluated for waste load allocation. The critical carrying capacity of the river was estimated to be roughly 1500 kg/d for BOD. Reductions in non-point source loadings were noted to lower this critical limit. The treatment plants in La Feria and San Benito have to be upgraded for sustained development. Bilateral redistribution of wastewater loadings (i.e., two-party trading) was noted to be infeasible under existing technological and assumed policy conditions. Multilateral redistribution of waste loads was possible but required several cities to alter their discharges and as such may be impractical. The variability in the non-point source loadings was seen to have a significant impact on the multilateral redistribution.