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The Texas Instream Flow Program

The Texas Instream Flow Program. Barney Austin Surface Water Resources Division Texas Water Development Board. February 8 th , 2006. Instream flows methods. Desktops methods : Consensus Environmental Planning Criteria Lyons Method Comprehensive methods : State methodology.

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The Texas Instream Flow Program

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  1. The TexasInstream FlowProgram Barney Austin Surface Water Resources Division Texas Water Development Board February 8th, 2006

  2. Instream flows methods • Desktops methods : • Consensus Environmental Planning Criteria • Lyons Method • Comprehensive methods : • State methodology

  3. Desktop methods

  4. CPC for on-channel reservoirs

  5. CPC for direct diversions

  6. Comparison of flows…

  7. Comprehensive methods

  8. In 2001…Senate Bill 2 The Texas Legislature directed tri-agencies (TPWD, TWDB, and TCEQ) to: • Establish and continuously maintain an instream flow data collection and evaluation program, and • Develop methodologies to determine flow conditions in Texas rivers and streams necessary to support a sound ecological environment.

  9. Senate Bill 2 Framework for Instream Flow Study Program requires tri-agencies to: • Share oversight of program studies. • Share data, studies, analysis, information and reports. • Establish a Work Plan that prioritizes studies and sets interim deadlines for publication of flow determinations, and • Complete priority studies by December 31, 2010.

  10. Senate Bill 2 Framework for Instream Flow Study also: • Requires TCEQ to consider the results of completed studies in its review of any management plans, water rights, or interbasin transfers.

  11. Joint study accomplishments: • Interagency MOA • (Executed: Oct 17, 2002) • Programmatic Work Plan • (Final: Dec 19, 2002) • Technical Overview • (Draft: August 8, 2003) • NAS review…

  12. Summary of Agency Roles

  13. Texas Instream Flow Studies

  14. Timeframes for Priority Studies Toledo Bend Sabine R.

  15. Second Tier of Studies Developed to provide future direction in studies in the event priorities change or supplementary resources are made available. These include: • Upper Guadalupe River • Neches River • Red River • Upper Sabine River Colorado R. Two special studies include the Sulphur River (on-going) and the Lower Colorado River (monitoring). Sulphur R.

  16. Hydrology & Hydraulics TCEQ - Water Availability Model (WAM)

  17. Hydraulic Modeling – Brazos River Detail Area DOQQ photo taken February 4, 1995; ~7,500 cfs Boundary of FE Mesh used for flows below 3350 cfs is shown in green.

  18. Hydraulic Modeling – Brazos River • Finite Element Mesh (approximate element resolution 8m x 10m) • RMA-2 (depth averaged, hydrostatic Reynolds Averaged Navier-Stokes equations) • 1456 cfs shown FE mesh with depth contours 0.0m to 4.0m FE mesh with velocity contours 0.0 to 2.25 mps

  19. Hydraulic Modeling – Brazos River • Photo of “Island” area, November 2, 2001. • Flow is approximately 1500 cfs.

  20. Fish habitat utilization studies

  21. Habitat Modeling– Brazos River • Mesohabitats are delineated for 1456cfs using a grid-based GIS model

  22. Modeling Issues – Large woody debris South Sulphur near Cooper • Large Woody Debris (LWD) influences both hydraulics and habitat utilization analysis North Sulphur (near confluence) Sulphur US of Patman (near Site 2)

  23. Typical radial bounding regions MEBAA bounding boxes Modeling Issues – Mesh Interpolation Interpolating bathymetric single-beam data to the finite element mesh Exploit the anisotropic shape of the river cross-section for a better interpolation Use flow-directional coordinate system (either linear {TWDB} or curvilinear {CRWR})

  24. Modeling Issues – Mesh Interpolation Improved IDW interpolation using Mesh Elevating and Bathymetry Adjusting Algorithms (MEBAA) Standard IDW interpolation using Surface Water Modeling System

  25. Surveying (High Flow) Modeling (Low Flow) Modeling Issues - Geomorphology • Bathymetry that changes with flow Affects both hydraulic and habitat analysis

  26. Physical Processes • Flushing flows (> once per year) • Restore/enhance riffle habitat • Remove surficial and interstitial fine sediment • Determined through study of sediment and hydraulic model output • Channel maintenance (circa 1.5 per year) • Maintain physical characteristics of the channel • Study of flow-duration curves • Floodplain maintenance (once per 1-10 years) • Build and bring nutrients to the floodplain • Extent and frequency from (existing?) 1-D models or aerial photos • Valley maintenance • Q25-ish

  27. TCEQ – Water Quality & Specific Numeric Criteria • Dissolved Oxygen • Toxic Criteria • Aquatic Life • Human Health • Bacteria ---- Contact Recreation • Chloride, Sulfate, Total Dissolved Solids • pH as absolute minima and maxima • Temperature as absolute maxima

  28. Floodplain - Oxbow Lakes • Study of river-floodplain interaction and connectivity

  29. National Academy of Sciences • Evaluate science and methodology in key documents • Review and provide advice on scientific and technical matters relevant to the Instream Flow Program • Evaluate findings and recommendations of Tasks 1 and 2 for consistency with the requirements of Texas law for the study of Instream Flows

  30. NAS Committee • 11 members, 4 from Texas: • Dr. David Maidment (UT, Austin) • Dr. Kirk Winemiller (TAMU) • Dr. Clark Hubbs (UT, Austin) • Dr. Kenneth Dixon (UNT, Denton)

  31. NAS Public meetings • Austin – Oct 2003 • San Antonio – Jan 2004 • San Marcos – Mar 2004 • Report released in March 2005…

  32. Summary (the good stuff) • Developing instream flow recommendations for rivers is one of the most difficult and important challenges in applied ecological and physical sciences today.

  33. Summary (the good stuff) • The state of Texas shows an impressive commitment to designing and implementing an instream flow program…

  34. Summary (the good stuff) • The Texas agencies are commended for proposing a prospective, comprehensive instream flow program…the program will provide enormous benefits to the state over the next several decades and beyond.

  35. Major Recommendations:

  36. Two levels of oversight: • State level for management and program consistency • Local goals and approaches

  37. Clear definition for “Sound Ecological Environment”

  38. Goals…statewide and for individual subbasins

  39. Ecological indicators: • Responsive to flow • For monitoring & validation • Adaptive management • Achieving “Sound Ecological Environment”

  40. Existing information… How will it guide detailed technical evaluations?

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