Abstract:

This data was collected to identify effects of small freshwater inflow volumes on water and sediment quality in the Lavaca-Colorado estuary, Texas, from to 2015-09-01 to 2016-09-15. The aim of this study was to quantify the effects of small changes of inflow volumes on ecosystem health to evaluate the potential environmental benefits of hydrological conservation or restoration projects. Carancahua Bay is an ungaged watershed, so modeled flows using obtained from the Texas Water Development Board (TWDB), which uses the Texas Rainfall-Runoff (TxRR) model to estimate daily stream flows in ungagged watersheds. The TWDB watershed 15050 is composed of East Carancahua Creek and West Carancahua Creek, which contribute freshwater flow to the Carancahua Bay. The flow data was used to interpret biological changes at station N3 in dataset https://doi.org/10.7266/6ptst906, UDI: HI.x962.000:0018. This analysis indicates that an increased small volume, as low as 10% of freshwater inflow volume, can have positive benefits to estuarine conditions and health. Thus, hydrological protection or restoration projects based on small volumes can improve estuaries degraded by freshwater diversions.

Suggested Citation:

Montagna, P. A., H. Ehrmann, C.M. Olson, and E. L. Turner. 2025. Effects of small freshwater inflow volumes on water and sediment quality based on modeled flows to Carancahua Bay, Texas from 2015-09-01 to 2016-09-15. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/5d0sv6p1

Purpose:

The aim of this study is to evaluate the potential environmental benefits of hydrological conservation or restoration projects by quantifying the effects of small changes of inflow volumes on estuary ecosystem health. Discharge at a station was compared to water quality (indicated by nutrients and chlorophyll) and sediment quality (indicated by benthic communities) sampled monthly at five stations in the upper reaches of the Lavaca-Colorado Estuaries, specifically, Carancahua Bay, Texas. Distinct oligohaline and mesohaline benthic communities were present in both estuaries. A positive correlation between multivariate water quality and benthic metrics indicates a positive relationship between small flow changes and estuarine health.

Data Parameters and Units:

Modeled Discharge (acre-feet per day, ac-ft/d), Modeled Discharge (million cubic meters per day, m³/d), Cumulative Discharge (million cubic meters per sample period, m³), Salinity (practical salinity units, psu).

Methods:

TWDB uses the Texas Rainfall-Runoff (TxRR) model to estimate daily stream flows in ungaged watersheds. This model is conceptually similar to the Agricultural Research Service (ARS) rainfall-runoff model which is based on the Soil Conservation Service’s curve number method to estimate direct runoff from a precipitation event. TxRR, however, has three key differences: (1) use of a simpler and more straightforward mathematics, (2) introduction of 12 monthly depletion factors, instead of single depletion factor used in the ARS Model, and (3) introduction of a base flow component into the model. TxRR has been used to estimate daily stream flows from over 50 coastal ungaged watersheds as a part of the Bays & Estuaries Coastal Hydrology Program to study freshwater inflows to Texas bays and estuaries.

Provenance and Historical References:

Montagna PA, Ehrmann H, Olson CM, Turner EL. 2023. Effects of small freshwater inflow volumes on water and sediment quality obtained from bays in Texas from 2015-09-30 to 2016-09-15. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. https://doi.org/10.7266/6ptst906 Montagna PA, Ehrmann H, Olson CM, Turner EL. 2024. Effects of small freshwater inflow volumes on water and sediment quality based on USGS gaged flows from 2015-09-30 to 2016-09-15. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. https://doi.org/10.7266/0y56trjr

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