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

STEP 3. Obtain and evaluate geographically-oriented biological data in support of a flow regime
analysis.
STEP 4. Parameterize the flow regime analysis using ecological and biological data
STEP 5. Evaluate and refine the initial flow matrix
Our study and report provides information needed to immediately complete steps 2 and 3.
Furthermore the information provided in this report can be used to assist the BBEST complete
the remaining steps.
The SAC draft guidance also provided other general recommendations on use of biological data.
They are paraphrased and listed below.
1. Quantification of biology based flow parameters
The BBEST should examine sources from the literature review, assess them for relevance and
identify any statements, data, or graphs that specifically link aspects of the flow regime with
biota or key ecological processes. It is important to document key habitat requirements and
preferences of target biological species and assemblages.
2. Causal connections based on available data and known relationships
It is recommended that the BBEST portray the flow-ecology relationships and ecological
processes in a conceptual model. Conceptual models provide a concise way to portray
ecological knowledge and show hypothesized linkages between flow and various aspects of
ecosystem health, or a species’ dependence upon certain flow conditions to complete a particular
life history stage.
3. If there is existing data that links aspects of the flow regime with biological information,
this information should be used to parameterize the flow regime analysis, e.g. HEFR
Based on the quantification of flow parameters, development of causal connections and
geospatial information, information may be available that specifically links biological
information to aspects of the flow regime. Even if specific biological information is not
available to inform all decision points in the hydrographic separation, any available information
should be used.
4. Subsistence flows should maintain water quality and key habitat considerations
Subsistence flows need to be sufficient to support key habitats and habitat needs for focal
species, populations, or guilds of representative flowing-water organisms and adjustments should
be made to minimize or avoid loss of key habitats and needs, to the extent possible. Flows should
be evaluated and adjusted to ensure water quality parameters (e.g. DO and temperature) are
maintained in a suitable range to ensure aquatic life persists/endures.
17
Environmental Institute of Houston
November 17, 2009
Trinity River Basin
Biological Overlay