Ecological Overlay for the Trinity River for support of Development of ...

Introduction
This report summarizes available ecological information on the Trinity River and provides an
“Ecological Overlay” document for future development of instream flow recommendations for
the Trinity River. This summary report includes graphical representations and tabular
information revealing key relationships between flow variation and the ecological indicators.
This also include a species occurrence matrix indicating, when available, the location of various
fish and aquatic species within the basin by river mile, TCEQ waterbody code, HUC code and
latitude and longitude. This was developed in coordination with San Jacinto River Authority and
other investigators in Texas who are conducting similar studies. Supporting graphical and
tabular data are available in digital format from the Trinity River Authority and/or Texas Water
Development Board with a copy of the full summary report.
Data used in the preparation was extracted from various sources including published peer
reviewed articles, agency reports, federal aid progress reports, conference proceedings, and
regional, state and federal environmental databases. The focus of this study was on development
of ecological information on the occurrence and relationship of instream living resources and
hydrology. However, two related study objectives were also included in the scope of work. This
included developing background data on important variables processes needed to understand the
influence of changing hydrology on water quality and the physical transport of sediments.
Therefore an attempt was made to evaluate the fluctuation of important water quality parameters
(water temperature, conductivity, dissolved oxygen, selected nutrients and suspended solids in
relation to flow, including loading estimates at selected priority gages. In addition we have
provided estimates of downstream loading of nutrients and suspended solids to the estuary from
the Trinity River. Two major products produced from this study include a species occurrence
matrix which utilized data compiled from surveys of the literature including agency reports, and
summarization of ecological relationships of candidate “focal species” previously suggested by
TPWD. These focal species were compared, based on their life history attributes, to other
members of the fish community to determine if they can serve as indicator species representing
larger ecological fish guilds. Finally using these indicator species generic and specific
recommendations on possible instream flow regimes is presented. This data can be used to
inform current and future hydrological analysis generated by IHA/HEFR/MBFIT to prescribe
recommend flow regimes for conservation and protection of the ecological health of the river.
Although other biological data exist on benthic communities and wildlife, by far more
information exists on the fish communities of the Trinity River basin. This is due in part to their
cultural and economic importance as a fisheries resource and the more extensive history of
research and monitoring by state agencies and university researchers. The primary sources of
data include fisheries and river fish community studies by Texas Parks and Wildlife Department
during the last 40 years and recent investigations by TCEQ and predecessor agencies conducting
water quality related permitting studies including receiving water assessments. In addition, EPA
and TCEQ have funded additional university studies investigating the effects of water quality on
biota. Comparatively few data and studies exist on invertebrate and wildlife resources.
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Environmental Institute of Houston
November 17, 2009
Trinity River Basin
Biological Overlay