Year Completed:

Construction Cost:

Trinity River Authority
City of Dallas
City of Houston
Tarrant Regional Water District
North Texas Municipal Water District

Contact Name:
Glenn Clingenpeel
(817) 467-4343

Nature of the Work:

  • Freshwater Inflows
  • Ecological Health
  • Statistical Analyses

Galveston Bay Freshwater Inflow Study

Project Description

In 1998, the Texas Parks and Wildlife Department (TPWD) recommended a pattern of monthly inflows as necessary for maintenance of the ecological health of the Galveston Bay estuary. These "beneficial inflows" (so named following provisions of the Texas Water Code introduced by the 69th Legislature that require the maintenance of "beneficial inflows" to the Texas estuaries necessary for maintaining an "ecologically sound environment") were computed using a comprehensive methodology developed by the Texas Water Development Board (TWDB) and TPWD. The objective of this study is to expand upon this work, attempting to improve and render more accurate certain aspects of the “State” methodology. 

Services Provided

Espey Consultants, Inc. (EC), working with Dr. George Ward (Consultant), began a multitude of analyses in 2000.  A substantial effort has been made to answer the crucial question:  Is the commercial harvest of a species (upon which present inflow regression equations are based) in fact a measure of its real abundance in the bay, given the other potentially relevant factors that can corrupt the data, and, if so, have the important relationships been captured in the statistical model?  A detailed study of the derivation of commercial harvest data was made, making several findings.   Subsequent to these findings, the methodology for the generation of the inflow regression equations was derived, as well as statistical analyses resulting in correlations between commercial harvest and more direct measures of ecosystem productivity, such as diversity and abundance.

Several other analyses are entailed in this project.  First, EC continues the investigation into the basis for specification of inflow and salinity constraints used in the methodology, further searching for a better demonstration of the relation of inflow to salinity and the correspondence of salinity preference zones to abundance.  Also, instead of relying on aggregated bi-monthly flows, duration, freshets, and geographic distribution of flows will be used to make a refined delineation of inflows.  Lastly, work continues on the exploration of alternative management objectives as well as hydrologic studies and analyses of yields and water availability in the Trinity/San Jacinto Basins.



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