Informing Environmental Flow Standards in Support of Wetlands in Big Boggy

Abstract

The Colorado River of Texas no longer provides direct freshwater flows to the wetlands of East Matagorda Bay, and a few small basins, such as that of Big Boggy Creek, provide the only inflowing freshwater. The upstream portions of the Big Boggy watershed were extensively modified in the past and its freshwater inflows have been reduced, negatively affecting the wetlands in this basin. The central objective of this project was to help identify environmental flow standards for the Big Boggy coastal watershed and recommend potential restoration actions to sustain its wetlands. I first identified wetland and land cover trends over the historical period to today, finding that this watershed has lost more than half of its low marsh area since 1953. I then quantified the flow rates into/out of the watershed and created a water budget, finding that relative sea level rise and seasonal droughts are likely responsible for the historical loss of wetlands in this watershed. I modeled both historical and future inflows, from the years 1953 to 2100, under various scenarios. I developed a decision tool that can be used by natural resource managers to identify the quantity of supplemental water that is needed to avoid the damaging effects of drought. Finally, I recommend several potential restoration options within the Big Boggy NWR and adjacent lands that will improve both flows and habitat.