An Inflow Demonstration Project to Assess the Impacts of Targeted Water Deliveries on Estuarine Productivity in Matagorda Bay

The quality, quantity, and timing of freshwater inflow alters the condition of estuaries, which in turn drives the structure, function, and sustainability of estuarine habitats (Alber 2002). Freshwater inflows are heavily influenced by large-scale climatic cycles, which are becoming more variable over time (Tolan 2007; Pollack et al. 2011). In Texas, water demand and evaporation are expected to increase in the future, while water supply is expected to decrease (Nielsen-Gammon 2011; Bugica et al. 2020), resulting in increased stresses on estuarine ecosystems. Considering freshwater inflows drive water quality and subsequently productivity through changes to nutrient and chlorophyll concentrations (Montagna et al. 2018), it is imperative to gather and understand baseline data on biological communities at this estuarine interface.

Marshes represent one of the most critical nursery habitats for ecologically and economically important finfish and shellfish in the Matagorda Bay ecosystem. Despite its current level of productivity (Stunz et al. 2023a, 2023b, 2024), Matagorda Bay is subject to many of the same stressors that other estuaries face including habitat degradation, changes to freshwater inflows, and increasing frequency of ecological extremes such as drought.

During low inflow conditions which commonly occur during droughts, the upper marshes of Matagorda Bay can experience high salinity conditions which can reduce estuarine habitat quality and overall productivity (Stunz et al. 2023b, Dodson et al. 2025). Access to high quality nursery habitats is critical for nekton (i.e., fish, shrimp, and crabs) growth and survival, especially considering up to 75% of commercially or recreationally important species in the Gulf are estuarine dependent (Chamber 1992). As such, during droughts or other periods when marsh nursery habitats are exhibiting high salinities (e.g., >30 practical salinity units (psu), it is imperative that at least some refuge areas for marsh vegetation and nekton are available to maximize overall ecosystem productivity and resilience. Projecting forward, it is highly anticipated that extended drought conditions will require additional prescribed measures such as targeted inflows to maintain estuarine conditions at key marsh habitats in Matagorda Bay.

The Harte Research Institute of Texas A&M University-Corpus Christi and BIO-WEST, Inc. will assist the Lower Colorado River Authority (LCRA) in the implementation of the Matagorda Bay Targeted Inflow Demonstration Project (Project) to demonstrate whether targeted freshwater inflows delivered through LCRA’s canal system can more efficiently improve estuarine habitat during drought periods relative to traditional freshwater inflows into the Colorado River Delta.