Effects of the Rincon Bayou Pipeline on salinity in the upper Nueces Delta

Abstract

A pipeline to pump water from the Nueces River to the upper delta at Rincon Bayou was constructed to mitigate the reduction of inflow from impoundments. Pumping has restored ecological function to the Nueces Estuary by increasing inflow and decreasing salinity, and transitioned the marsh into a positive estuary (lower salinities upstream increasing downstream towards the bay). Pumping has decreased the occurrences of salinities greater than 35 practical salinity units during drought conditions; however the current pumping regime causes a disturbed environment by creating extreme fluctuations in salinities in a very short time period. Immediately after pumping salinity fluctuations at the pumping outfall commence from hypersaline to fresh. When pumping ceases, salinity fluctuates from fresh to hypersaline until the next pumping event. Pumping often occurs during rainfall and flooding events when reservoir levels meet certain capacities that trigger pass-through requirements. This strategy provides inflow when it is not needed, and inhibits pumping during drought conditions when inflow is needed to maintain the quality of the estuarine ecosystem. While the current pumping regime has restored estuary conditions to Rincon Bayou by increasing inflow and decreasing salinity, it also causes extreme fluctuations in salinity that act as a disturbance. A lower magnitude, longer duration pumping strategy would create a more stable environment by providing freshwater continuously and would be an improved hydrological restoration strategy. Citation: Del Rosario EA, Montagna PA. 2018. Effects of the Rincon Bayou Pipeline on salinity in the upper Nueces Delta. Texas Water Journal. 9(1):30-49. Available from: https://doi.org/10.21423/twj.v9i1.7042.

Focused Flows to Maintain Natural Nursery Habitats

“…This solution led to higher abundance and diversity of intertidal vegetation (Alexander and Dunton 2002) and benthic communities (Montagna et al 2002b). Additionally, a pipeline was built to move fresh water directly into the marsh in 2009, and the pumping was able to maintain salinities at less than 35 practical salinity units (psu) during droughts (Del Rosario and Montagna 2018). It was also determined that inflow volumes as low 0.41 m 3 /second (29 ac-ft/day) would maintain optimal salinity and water depth for infauna and epifauna communities (Montagna et al 2018).…”