The TexasInstream Flow Program

Barney AustinSurface Water Resources DivisionTexas Water Development Board

May 21, 2004

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.

Senate Bill 2Framework 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, andComplete priority studies by December 31, 2010.

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.

Joint study accomplishments:

• Interagency MOA (Executed: Oct 17, 2002)

• Programmatic Work Plan (Final: Dec 19, 2002)

• NAS contract (July 2003)

•Technical Overview (Draft: August 8, 2003)

Summary of Agency Roles

Instream Flow Study ElementCoordinating

Agency

Study Design Joint

Hydrological and Hydraulic Evaluation

TWDB

Biological Evaluation TPWD

Physical Processes Evaluation Joint

Water Quality Evaluation TCEQ

Integration Joint

Interpretation Joint

Study Report Joint

Monitoring and Validation Joint

Texas Texas Instream FlowInstream FlowStudiesStudies

Timeframes for Priority Studies

Subbasin 2003 2004 2005 2006 2007 2008 2009 2010

Lower Guadalupe River

Lower Brazos River

Lower San Antonio River

Middle Trinity River

Lower Sabine River

Middle Brazos River

Sabine R. Toledo Bend

Second Tier of Studies

Upper Guadalupe RiverNeches RiverRed RiverUpper Sabine River

Two special studies include the Sulphur River (on-going) and the Lower Colorado River (monitoring).

Developed to provide future direction in studies in the event priorities change or supplementary resources are made available. These include:

Sulphur R.

Colorado R.

Tiered Aquatic Life ----- D.O. Toxic Criteria Aquatic Life Human Health

Bacteria ---- Contact RecreationChloride, Sulfate, Total Dissolved SolidspH as absolute minima and maximaTemperature as absolute maxima

TCEQ – Water Quality & Specific Numeric Criteria

Sound Ecological EnvironmentSound Ecological Environment

Maintain Ecological IntegrityMaintain Ecological Integrity • processes & functions that create

& maintain habitat & otherphysicochemical conditionsthat support survival, growth,& reproduction

Conserve BiodiversityConserve Biodiversity • fish, invertebrates,

mussels, plants … • riparian diversity

Biological approach

Coordinating Agency - Texas Parks & WildlifeField surveys to develop sampling strategies and characterize biota and habitat

3 contracts to be executed for reconnaissance on priority sub-basins.

Habitat-based approach Geomorphology, hydrology and hydraulics Two complementary analyses using spatially-explicit habitat

models Microhabitat availability using habitat guilds and/or target species Habitat heterogeneity (diversity/complexity) using landscape metrics

Develop habitat-discharge functions and time-series Important to consider:

Both channel and riparian areas…also consider watershed; connectivity

Key habitats; environmental requirements and life history of flow dependent biota

Temporal considerations

Hydrology & Hydraulics

TCEQ - Water Availability Model (WAM)

Develop Finite Element mesh

Hydraulic Modeling – Brazos River

DOQQ photo taken February 4, 1995; ~7,500 cfsBoundary of FE Mesh used for flows below 3350 cfs is shown in green.

Detail Area

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 contours0.0m to 4.0m

FE mesh with velocity contours0.0 to 2.25 mps

Hydraulic Modeling – Brazos River

Photo of “Island” area, November 2, 2001.Flow is approximately 1500 cfs.

Fish habitat utilization studies

Habitat Modeling– Brazos River

Mesohabitats are delineated for 1456cfs using a grid-based GIS model

Mesohabitat vs. discharge

INSTREAM FLOW STUDY:Brazos River near Allens Creek Reservoir

Mesohabitat Area Absolute Area at each Flow Rate

0

200

400

600

800

1000

1200

1400

500 1000 1500 2000 2500 3000 3500

Flow (cfs)

Ab

solu

te M

eso

hab

itat

Are

a (s

q.

feet

x 1

,000

)

Deep Pool

Medium Pool

Shallow Pool

Run

Slow Riffle

Fast Riffle

Velocity Contour Plot

Modeling Issues – Large woody debris

Large Woody Debris (LWD) influences both hydraulics and habitat utilization analysis

North Sulphur (near confluence)

South Sulphur near Cooper

Sulphur US of Patman (near Site 2)

Modeling Issues – Mesh Interpolation

 

MEBAA bounding boxes

Typical radial bounding regions

Interpolating bathymetric single-beam data to the finite element meshExploit the anisotropic shape of the river cross-section for a better interpolationUse flow-directional coordinate system (either linear {TWDB} or curvilinear {CRWR})

Modeling Issues – Mesh Interpolation

Standard IDW interpolation using Surface Water Modeling System

Improved IDW interpolation using Mesh Elevating and Bathymetry Adjusting Algorithms (MEBAA)

Modeling Issues - Geomorphology

Bathymetry that changes with flow

Surveying (High Flow)

Modeling (Low Flow)

Affects both hydraulic and habitat analysis

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

Integration and Interpretation

National Academy of Sciences1. $300k contract executed in July 20032. Evaluate science and methodology in key documents3. Review and provide advice on scientific and technical

matters relevant to the Instream Flow Program4. Evaluate findings and recommendations of Tasks 1

and 2 for consistency with the requirements of Texas law for the study of Instream Flows

Final Report due Oct 2004

Dr. Lauren Alexander (NAS) testified at the Feb 18th Study Commission meeting

National Academy of Sciences

• Have had three open meetings in Texas• Austin, San Antonio, San Marcos

• Questions/answers and public testimony• “Panel of experts” for second meeting• Not able/willing to release draft report• Comprehensive guide to be used by any

entity conducting instream flow studies in Texas…and beyond?

Instream Flow Study Program Results Will Be:

An essential database for conservation of fish and wildlife resources in Texas. Used in the State’s water rights permitting process, andIncorporated into future regional and state water plans.

For more information….

http://www.twdb.state.tx.us/InstreamFlows/

Barney Austin

Texas Water Development Board

Tel: 463-8856

Email: barney.austin@twdb.state.tx.us