Characterization of the Influence of Freshwater Inflow on Trinity River Delta Indicators


The primary objectives for this study were to 1) inventory submerged aquatic vegetation and Atlantic rangia in the Trinity River Delta; and 2) monitor salinity using automated devices in the Trinity River Delta.

Study Area

Trinity River delta and surrounding waters

Project Period

2017 - 2019


A better understanding of the hydrodynamics of the Trinity River delta and the distribution and abundance of the freshwater inflow indicator species, rangia and wild celery, are required for resource managers to inform freshwater inflow needs to Galveston Bay. Researchers completed an inventory of submerged aquatic vegetation (SAV) and rangia clam beds and input into geographic information system (GIS) databases. A total of 10 rangia monitoring sites were established and sampled every six months. SAV was surveyed for during each visit to the delta, and special trips were made during very low tides, or unusually clear water, to best map the extent and location of SAV. Automated temperature and salinity/conductivity (SCT) meters, and three water depth recorders, were co-located with rangia monitoring sites to characterize changes in salinity regime associated with freshwater inflow from the Trinity River. The SCT automated probes automatically logged salinity and temperature at 15 minute intervals for approximately one year.

Publications and Presentations

Oakley, J.W., Omar, M.E., and Guillen, G.J. 2020. Characterization of the influence of freshwater inflow on Trinity River delta bioindicators. EIH Report 20-001, 57 pp.

Omar, M. 2020. Modelling the growth of Atlantic rangia, Rangia cuneata, in response to freshwater inflow, Trinity River delta, Galveston Bay. University of Houston-Clear Lake.

Omar, M.E., Oakley, J.W., and Guillen, G.J. 2020. Understanding ecology of Atlantic rangia in Galveston Bay: deciphering the role of freshwater inflows. Galveston Bay Estuary Program, State of the Bay Symposium, Galveston, TX. Presentation.

Omar, M.E., Oakley, J.W., and Guillen, G.J. 2019. Understanding ecology of Atlantic rangia: toward better management of freshwater inflows. Coastal and Estuarine Research Federation, Mobile, AL. Poster.

Guillen, G., Gordon, A., Oakley, J., and Mokrech, M. 2016. Trinity River delta and upper Trinity Bay rangia population assessment. Final Report 16-001, 57 pp.

Guillen, G., Oakley, J., Johns, N., and Gordon, M. 2016. Influence of freshwater inflow on the occurrence of water celery and the abundance and health of Atlantic rangia in the Trinity River delta, Galveston Bay, Texas. In Restore America's Estuaries, New Orleans, LA. Poster.

Project Sponsors


  • Environmental Institute of Houston

    Phone: 281-283-3950

    North Office Annex
    2700 Bay Area Blvd, Box 540
    Houston, TX 77058-1002