Caddo Lake Institute

Aquatic Biology Meeting July 2008

Meeting Summary

Meeting Summary

Joe Trungale, with Trungale Engineering and Science, gave the introductory talk, which summarized the work of the Environmental Flows Project to-date.  Begun in 2004, the Project has relied upon meetings of stakeholders and scientists, field research, literature reviews and analysis to develop recommendations for environmental flow regimes for the major rivers in the Cypress Basin.  The work has also focused on determining how a more natural flows release pattern could be obtained from Lake O’ the Pines to reflect natural cycles of flood, pulses, and low flows.  The work has been guided by a framework set out in Texas law in SB 2 and, later, SB 3, and the recommendations to the State of Texas by the National Academy of Sciences on developing environmental flow regimes. 
The July 31, 2008 meeting on aquatic biology provided the opportunity for a small group of scientists to propose work to be done during the fall of 2008 to support the work of the project and the upcoming full meeting in early December.  Recommendations for work beyond that period were also discussed.  

Jack Killgore, with the US Army Corps of Engineers, in Vicksburg, LA, followed with a presentation on several studies that the Corps has conducted in the Cypress Basin.  A 1985 study on Black Cypress and Little Cypress, two tributaries to Caddo Lake, identified SI (Suitability Index) curves for a number of fish species.  A 1992-93 study of IFIM (instream flow incremental methods) sought to determine how habitats of certain fish would be affected by differing in-stream flow rates.  This study documented 80 species of fish in the basin.  A 1997-1999 floodplain study focused on habitat during higher flows. 
Killgore also discussed a 2007-2008 project to create gravel bars in Cypress Creek to support spawning of fish, including paddlefish.  He discussed the need and alternatives for monitoring the success of the gravel bar and indicated that the experiment with gravel could have important implications for other areas of the Mississippi watershed, but that there is currently no funding for  monitoring of the gravels or use by fish.

Joe Trungale then gave a presentation on Hydraulic-Habitat Modeling and Time Series.  Trungale took data from Corps studies on Black and Little Cypress and modeled the amount of habitat for certain fish species (chosen because they  represent a ‘guild’) as it relates to flow rates.  He then applied the current draft flow regimes (that specify average flow rates in a month for base dry, base average, base wet years) to the model to determine which species might be negatively or positively affected by different flow regimes.  Discussion centered on a number of issues regarding the value of the modeling and applicability to other tributaries. 

Bruce Moring with the U.S. Geological Survey gave a presentation on the different options for evaluating high flows prescriptions.  His presentation began by posing some basic questions: 

  • How accurate are the flow prescriptions for bank full conditions, maintenance of biodiversity and habitat, and hydrologic connectivity?
  • Should the flow prescriptions be prescribed differently depending on location in the reach of interest?
  • How important in number and areal coverage are below bank-full points of connection to backwater habitat?

He then discussed studies he and USGS had conducted that measured how different flow rates from the dam affected flows downstream and connectivity to backwaters.  The study had revealed that a release of 1800 to 3000 cfs was all that was needed for bank-full and backwater connectivity, instead of 6000 cfs as the draft regime suggests.

Trungale then finished the meeting by leading a discussion on the guild matrix and the next steps.  Guilds were chosen based on reproductive and feeding habits.  It was suggested that habitat guilds be used, as well, considering that changing flows will result in habitat manipulation.

Frank Heitmuller with the U.S. Geological Survey raised the issue of whether the project had discussed options for additional work on sediment.  Because of the funding limitations, no work was proposed for this fall, but additional work may be proposed at a later time.


Thursday July 31, 2008 at USGS, Austin, TX 

09:00 - 09:30 Introductions/Background (CLI)
09:30 - 10:30 Biological - Habitat Suitability (WES)
10:30 - 10:45 Break
10:45 - 11:45 Hydraulic - Habitat vs. Q and Habitat Time Series (TES)
12:00 - 01:00 Lunch
01:00 - 02:00 Interpretation - Refine/Validate Base Flow recommendations
02:00 - 03:00 Connectivity Flows - WSE v Q & ecological value (USGS)
03:00 - 03:15 Break
03:15 - 04:15 Future work


Introduction to the Environmental Flows Process by Joe Trungale, Trungale Engineering and Science

Flow-Ecological Response Curves and Habitat Time Series
by Joe Trungale of Trungale Engineering, in powerpoint

High Flow Pulses and Watershed Connectivity (USGS)
by J. Bruce Moring, of the US Geological Survey, in powerpoint



 A Collaborative and Adaptive Process for Developing Environmental Flow Recommendations, Sustainable Rivers Process developed by the Nature Conservancy and being employed in the Caddo Watershed, 2006  

Texas Instream Flow Program Technical Overview, State agency guidelines for conducting instream flow studies, May 2008

Caddo Flows-Ecology Workshops 

Texas A&M Summary Report, Supporting the Development of Flow Recommendations, April 2005 

Summary of May 2005 Flows-Ecology Workshop, Big Cypress and Caddo Lake Building Blocks and Research Priorities 

Summary of October 2006 Flows-Ecology Workshop, Little and Black Cypress Building Blocks

Previous Instream Flow Studies in the Cypress Basin 

A Report on the Aquatic Resources of the Cypress Bayou Basin, Texas, USFWS IFIM Study on Little and Black Cypress, 1984 

Application of the habitat evaluation procedures in the Cypress Bayou Basin, Texas, USACE HEP Study on Little and Black Cypress, 1987 

Report on Minimum Flow Considerations, Terrestrial Mitigation and Ecological Effects on Caddo Lake Associated with Little Cypress Reservoir Development, Espey, Huston & Associates critique of Little and Black Cypress Studies, 1987 

Red River Waterway Project, Shreveport, LA, to Daingerfield, TX, Reach, Reevaluation Study In-Progress Review: Appendix 6. Aquatic Resources, USACE IFIM on Big Cypress, 1994

Draft Scopes of Work 

Task 1 – Low Flow Verification 

Task 2 – High Flow Verification 


Historic Fish Data (Draft) - Compilation existing biological data including georeferenced historical collections and species lists with associated reproductive, feeding and habitat requirements as well as other pertinent life history information. Includes evaluation of historical trends in species relative abundances, identifies species of conservation concern and lists preliminary recommendations of target species or guilds. 

Rating Curves (Draft) – Flow vs. Water Surface Elevation rating curves based on Pressure Transducers installed on Big Cypress Creek. 


Study Site Locations 


Little and Black Cypress PHABSIM models (USFWS-IFIM 1984) 

Big Cypress PHABSIM Models (USACE-IFIM 1994)


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