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Texas Instream Flow Studies: Technical Overview. Wendy Gordon, Ph.D. Texas Commission on Environmental Quality. October 2006. The Context of Instream Flow Science. Acknowledgment of the importance of water flowing in a stream to fish, wildlife and people

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texas instream flow studies technical overview
Texas Instream Flow Studies:Technical Overview

Wendy Gordon, Ph.D.

Texas Commission on Environmental Quality

October 2006

the context of instream flow science
The Context of Instream Flow Science
  • Acknowledgment of the importance of water flowing in a stream to fish, wildlife and people
  • Acknowledgment that competing uses of water have resulted in degraded river ecosystems
  • The challenge of developing methods to quantify environmental or instream flow needs
paradigm shift in instream flow recommendations
Paradigm Shift in Instream Flow Recommendations
  • 1950s-70s development of first instream flow methods yielding single minimum flow
  • Growing recognition of role of natural flow regimes: magnitude, duration, frequency, timing, rate of change
  • Recent shift to consideration of entire flow regime: subsistence, base, high flow pulses, overbank
senate bill 2
Senate Bill 2

In 2001, the Texas Legislature directed TCEQ, TPWD & TWDB to:

  • Establish data collection and evaluation program
  • Determine flow conditions necessary tosupport a sound ecological environmentin Texas rivers and streams
  • Complete priority studies by December 31, 2010
legislative directive
Legislative Directive

“…conduct studies and analyses to determine appropriate methodologies for determining flow conditions in the state’s rivers and streams necessary to support a sound ecological environment.”

slide6
State drafted its methodology
  • State contracted with NRC to peer review program
  • Members included TNC’s Brian Richter
  • Report published in 2005
instream flow components
Instream Flow Components

(recommended by National Research Council 2005)

statewide goal support a sound ecological environment
Statewide Goal: Support a Sound Ecological Environment

“A resilient, functioning ecosystem characterized by intact, natural processes, and a balanced, integrated, and adaptive community of organisms comparable to that of the natural habitat of a region."

ecosystem diversity
Ecosystem Diversity

Biotic Provinces

River Basins

interdisciplinary effort
Interdisciplinary Effort
  • Summary of the State of Knowledge
  • Develop Conceptual Model &
    • Tie Knowledge to Flow Components
  • Identify and Prioritize Knowledge Gaps
  • Develop Prioritized Research Agenda

Study Design

slide14

Steps in TIFP Sub-Basin Studies

Reconnaissance and

Information Evaluation

Stakeholder

Input

Stakeholder

Input

Goal Development Consistent with Sound Ecological Environment

Peer

Review

Study Design

Multidisciplinary Data Collection

and Evaluation

Stakeholder

Input

Peer

Review

Data Integration to Generate

Flow Conditions

Stakeholder

Input

Draft Study Report

Stakeholder

Input

Peer

Review

Final Study Report

SB2 ends

Post SB2

Next Steps: Implementation, Monitoring, and Adaptive Management

simple conceptual model

Sound Ecological Environment

Subsistence Flows

Base Flows

High Flow Pulses

Overbank Flows

Conserve biological

function

Conserve biological /

habitat diversity and

water quality

Life history /

geomorphic processes

Floodplain maintenance

  • Water quality
  • tolerances met
  • Key habitat
  • thresholds maintained
  • Habitat for flow
  • dependent species
  • Bank storage/moisture
  • Suitable temperatures /
  • dissolved oxygen
  • Fish spawning cues
  • Maintain channel
  • Sediment/nutrient
  • transport
  • Moisture and nutrients
  • to floodplain
  • Riparian recruitment

Simple Conceptual Model

study design
Study Design
  • Incorporate conceptual model of system
  • Determine geographic scope of study
  • Prioritize data deficiencies
  • Develop basin-specific interdisciplinary study plan
slide21

Steps in TIFP Sub-Basin Studies

Reconnaissance and

Information Evaluation

Stakeholder

Input

Stakeholder

Input

Goal Development Consistent with Sound Ecological Environment

Peer

Review

Study Design

Multidisciplinary Data Collection

and Evaluation

Stakeholder

Input

Peer

Review

Data Integration to Generate

Flow Conditions

Stakeholder

Input

Draft Study Report

Stakeholder

Input

Peer

Review

Final Study Report

SB2 ends

Post SB2

Next Steps: Implementation, Monitoring, and Adaptive Management

slide22

Primary Disciplines

Physical Processes (Geomorphology)

Hydrology & Hydraulics

Connectivity

Biology

Water Quality

biology
Biology
  • Examine integrity of biological community
  • Examine biodiversity within ecosystem
  • Assess habitat-flow relationships
biology24
Biology

Biodiversity

Habitat Diversity

water quality
Water Quality
  • Identify constituents of concern
  • Assess low flow-water quality relationship
  • Conduct water quality modeling studies
water quality26
Water Quality
  • Dissolved oxygen
  • pH
  • Temperature
  • Total dissolved solids
  • Turbidity/clarity
  • Nutrients
hydrology hydraulics
Hydrology & Hydraulics
  • Calculate flow statistics
  • Describe Wet, Normal, & Dry conditions
  • Model hydraulic characteristics
hydraulic and habitat modeling
Hydraulic and Habitat Modeling

Habitat changes with flow

physical processes geomorphology
Physical Processes (Geomorphology)
  • Assess bedforms, banks, and floodplains
  • Assess active floodplain and channel processes
  • Assess channel adjusting and overbank flow behavior
  • Develop sediment budgets
  • Identify habitat features
slide33

Watershed area determined by drainage divide. Determines the boundary conditions within which rivers operate.

Watershed

Topographic unit determined on the basis of local relief, valley slope and morphology. Defines the valley-setting.

Landscape Unit

Length of channel with a characteristic assemblage of geomorphic units.

River Style

Instream and floodplain landforms (pools, bars, levees, backwaters, etc.) that reflect distinct form-process associations.

Geomorphic Unit

Uniform patches of flow and substrate material within a geomorphic unit.

Hydraulic Unit

Individual elements (e.g., logs, rocks, gravel patches) within a stream.

Microhabitat

River Styles Hierarchy

slide34

Namoi River Basin, New South Wales

Watershed

0

100

300

400

200

Kilometers

slide35

Namoi River Basin, New South Wales

Watershed

Landscape

Unit

50

0

25

100

Kilometers

Legend – Landscape Units

Liverpool plains

Pillaga outwash

Lowland plains

Rugged metasediments

Mid to lower Peel

Rugged volcanics

Pillaga

Uplands

slide36

Watershed

Landscape

Unit

River Style

Middle Namoi

Sub-basin

50

0

25

Kilometers

slide37

Landscape

Unit

Uplands Escarpment Base of the Escarpment Rounded Foothills Lowland Plain

Channel

Slope

Channel and

Valley Width

Planform

Valley Cross Section

Head-water

Cut & Fill (Incised)

Vertically Accreated Floodplain

Floodplain Accumulation

River Style

Floodout

Cut & Fill (Intact)

Fan

Throughput

Transfer

Gorge

slide38

Geomorphic

Unit

Microhabitat

Hydraulic

Unit

Trailing Vegetation

Backwater

Rippled flow on cobbles

Submerged Macrophyte

Riffle

Barely perceptible flow on sand

Cobbles

Smooth surface flow on cobbles/sand

Floodplain

Large Woody Debris

Pool

Smooth surface flow on cobbles

Bar

Run

Secondary Channel

Boulders

Sand

Pool

Leaf Pack

Barely perceptible flow on sand/boulders

connectivity
Connectivity
  • Hydrologic connectivity
    • Upstream to down
    • Channel to floodplain
  • Groundwater/surface water interactions
slide40

Steps in TIFP Sub-Basin Studies

Reconnaissance and

Information Evaluation

Stakeholder

Input

Stakeholder

Input

Goal Development Consistent with Sound Ecological Environment

Peer

Review

Study Design

Multidisciplinary Data Collection

and Evaluation

Stakeholder

Input

Peer

Review

Data Integration to Generate

Flow Conditions

Stakeholder

Input

Draft Study Report

Stakeholder

Input

Peer

Review

Final Study Report

SB2 ends

Post SB2

Next Steps: Implementation, Monitoring, and Adaptive Management

slide41

Subsistence Flows

Identify Biological Considerations

Identify Water Quality Constituents of Concern

Calculate Low Flow Statistics

Conduct Water Quality Modeling Studies

Assess Low Flow - Water Quality Relationship

Other Biological Considerations

Primary Discipline

Hydrology/Hydraulics

Biology

Geomorphology

Water Quality

Subsistence Flows

slide42

Base Flows

Assess Bedform and Banks

Identify Biological Issues and Key Species

Calculate Base Flow Statistics

Collect Biological Data

Model Hydraulic Characteristics in Relation to Flow

Determine Habitat Criteria

Assess Habitat-Flow Relationships, including Diversity

Describe Wet, Normal, and Dry Years

Consider Biological and Riparian Issues

Consider Water Quality Issues

Primary Discipline

Hydrology/Hydraulics

Biology

Geomorphology

Water Quality

Base Flows

slide43

Assess Active Channel Processes

Develop Sediment Budgets

Assess Channel Adjusting Flow Behavior

Calculate High Flow Statistics

Consider Water Quality Issues

Describe Significant Habitat Conditions

Consider Biological Issues

Primary Discipline

Hydrology/Hydraulics

Biology

Geomorphology

Water Quality

High Flow Pulses

High Flow Pulses

slide44

Calculate Flood Frequency Statistics

Assess Active Floodplain and Channel Processes

Model Extent of Flood Events

Assess Overbank Flow Behavior

Consider Biological Issues

Conduct Riparian Studies

Consider Water Quality Issues

Estimate Riparian Requirements

Primary Discipline

Hydrology/Hydraulics

Biology

Geomorphology

Water Quality

Overbank Flows

Overbank Flows

integration of flow components
Integration of Flow Components

Wet year

Average year

Dry year

4,000-10,000 cfs for 2-3 days

Once every 3-5 years

Channel Maintenance

Riparian Connectivity, Seed dispersal

Flooplain habitat

Overbank

Flows

700-1500 cfs for 2-3 days

2-3 X per year every year

Sediment transport

Lateral connectivity

Fish spawning

1800 cfs for 2 days

1 X per yr every other year

“Big River fish” spawning

between Jul 15 - Aug 15

High Flow

Pulses

300-450 cfs

maintain biodiversity and longitudinal connectivity

Base

Flows

100-150 cfs

Fish habitat

150-300 cfs

Spring spawning

40-50 cfs

Fish habitat

90-100 cfs

Fish habitat

Subsistence

Flows

35 - 55 cfs

Maintain water quality (35 cfs) and key habitats in May (55 cfs)

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

projects funded for sb2
Projects Funded for SB2
  • Field-Based Mapping in support of a Geomorphic Analysis of the Lower San Antonio River Subbasin
  • GIS-Based Geomorphic Analysis of the Lower San Antonio River Subbasin
  • Field-Based Analysis in support of a Geomorphic Assessment of the Brazos & Navasota River Subbasin
  • Geomorphic Equilibrium in Southeast Texas Rivers
  • Distributional Survey and Habitat Utilization of Freshwater Mussels
  • Developing a Large Woody Debris Budget for the Sabine River, TX
  • Historical Zoogeography And Abundance Of Fishes In Two Texas River Basins With An Annotated Species List
  • Assessment of Hydrologic Alteration Software
  • Geomorphic Studies of the Lower Brazos and Navasota Rivers
  • Analysis of Existing Biological Data
  • Biological Sampling on the Lower Brazos River, Sabine River, and San Antonio River (3 separate contracts)
  • Stakeholder Process
additional questions comments
Additional Questions & Comments
  • Contact:
      • Wendy Gordon, TCEQ, 512-239-4174

wgordon@tceq.state.tx.us

      • Kevin Mayes, TPWD, 512-754-6844, ext. 25

Kevin.mayes@tpwd.state.tx.us

      • Mark Wentzel, TWDB, 512-936-0823

Mark.wentzel@twdb.state.tx.us

http://www.twdb.state.tx.us/instreamflows/index.html