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Streamflow Information in Texas. David R. Maidment Director, Center for Research in Water Resources University of Texas at Austin USGS Workshop, Fort Worth, Tx, 9 February 2005. Streamflow Information in Texas. Texas as part of the National Streamflow Information Program

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streamflow information in texas

Streamflow Information in Texas

David R. Maidment

Director, Center for Research in Water Resources

University of Texas at Austin

USGS Workshop, Fort Worth, Tx, 9 February 2005

streamflow information in texas2
Streamflow Information in Texas
  • Texas as part of the National Streamflow Information Program
  • Gage network analysis in Texas
  • Streamflow information system
streamflow information in texas3
Streamflow Information in Texas
  • Texas as part of the National Streamflow Information Program
  • Gage network analysis in Texas
  • Streamflow information system
national streamflow information program
National Streamflow Information Program
  • What gages need to be federally supported?
  • Five goals with associated GIS metrics
  • Recent National Academy report

National Academy Press

http://www.nap.edu

nsip goals
NSIP Goals
  • Interstate and International Waters (Borders and Compacts)
  • Flood Forecasts (NWS sites)
  • River Basin Outflows (Water Budgets)
  • Sentinel Watersheds (Regionalization and Long Term Trends of “natural flows”)
  • Water Quality (NAQWA, NASQAN,…
interstate and international waters 515 gage sites
Interstate and International Waters(515 gage sites)
  • Metric: Operate a discharge station at rivers:
  • on or near crossings of state and international borders where the drainage area of the river reach is greater than 500 square miles,
  • or where the location is mandated by a treaty, compact or decree
2 nws forecast points 3244 gage sites
2. NWS Forecast Points (3244 Gage sites)

Metric: Operate a streamgaging station at each NWS and NRCS forecast point that is not located on a reservoir

3 river basin outflows 450 gage sites
3.River Basin Outflows(450 gage sites)

Metric: Operate streamgaging stations near the terminus of each of the 352 Hydrologic Accounting Units (6-digit HUC’s) for water budgeting purposes

4 sentinel watersheds 874 gage sites
4. Sentinel Watersheds (874 Gage sites)

Ecoregion

Regionalization and Long Term Trends in Streamflow

(stations measuring natural flow in undisturbed lands)

5 water quality 210 gage sites
5. Water Quality (210 gage sites)

Metric: Locate a stream gage on the same river reach as a

permanent water quality monitoring site

source of nsip gage sites
Source of NSIP Gage Sites
  • Active USGS gages 2796 (63%)
  • Other agency gages 307 (7%)
  • Inactive gages 837 (19%)
  • New gages 484 (11%)

3103 existing gages (70%)

1221 inactive or new gages (30%)

number of nsip gage sites
Number of NSIP Gage Sites

Rhode Island (2)

Delaware (4)

Kansas (166)

Colorado (171)

California (201)

Texas (416)

streamflow information in texas17
Streamflow Information in Texas
  • Texas as part of the National Streamflow Information Program
  • Gage network analysis in Texas
  • Streamflow information system
stream gages in texas

200

300

400

Stream Gages in Texas

Peak Flows

Daily Mean Flows

1970

1900

1920

1930

1940

1950

1960

1980

1990

1910

back to 1962
Back to 1962

Existing: 312 daily stations, 17 annual peak stations

1962

1970

1900

1920

1930

1940

1950

1960

1980

1990

1910

nsip goals vs existing stations
NSIP Goals vs Existing Stations

NSIP Goal: 416 daily stations

Existing: 312 daily stations, 17 annual peak stations

1970

1900

1920

1930

1940

1950

1960

1980

1990

1910

slide21

Texas Stream Gaging Network

Active Stations

Discontinued Stations

texas gage network assessment
Texas Gage Network Assessment
  • Carried out by USGS and Texas Water Development Board (principal local cooperator)
  • Goals
    • Regionalization – estimate flows or flow characteristics at ungaged sites in 11 hydrologically similar regions
    • Major Flow – obtain flow rates and volumes in large streams
    • Outflow from the State – account for streamflow leaving the State
    • Streamflow conditions assessment – assess current conditions with regard to long-term data and define temporal trends in flow
regional optimization model
Regional Optimization Model
  • Based on Generalized Least Squares Regression – separates model error from error due to finite sample size
  • Estimating mean annual flow and 25 year peak flow using basin characteristics with equations for each hydrologic region
  • Three planning horizons (5yr, 10yr, 20yr)
  • Active or discontinued stations in natural watersheds considered
  • Start with all stations then step backwards, eliminating least informative station at each step
slide25

Estimating the 25-year Peak Streamflow

5yr

5yr

10yr

10yr

20yr

20yr

Mean Sampling Error

5yr

10yr

20yr

  • As number of stations increases, sampling error decreases until a minimum is reached
  • As planning horizon increases, sampling error decreases

Number of Stations

results of regional optimization
Results of Regional Optimization
  • Stations on steepest part of the curve offer the most valuable regional hydrologic information relative to basin characteristics
  • Sampling error increases as you go west and climate gets drier
    • Mean annual flow 6.6% to 114.3%
    • 25yr peak flow 9.9% to 28.5%
  • Much less error in regression equations for 25yr peak flow than mean annual flow in arid regions
  • Greater variability in error between regions than by adding stations within a region
flow correlations
Flow Correlations
  • Strong correlation in flows for upstream and downstream stations on the same river
    • 61 of 81 station pairs analyzed for mean annual flow have correlation coefficient > 0.9
    • 43 of 129 station pairs analyzed for 25 year flow have correlation coefficient > 0.9
  • Select stations for core network that are not highly correlated with other selected stations
slide28

Correlation Coefficient

> 0.95

0.9 – 0.95

< 0.9

Interstation Correlation of Mean Annual Flow

slide29

Correlation Coefficient

> 0.95

0.9 – 0.95

< 0.9

Interstation Correlation of 25yr Peak Flow

Figure 12

results of texas study
Results of Texas Study
  • Proposed core networkof 263 stations for regional hydrology purposes in natural watersheds
    • 205 active stations (78%)
  • NSIP for Texas requires 416 stations
    • Border (10), NWS (345), Basin (36), Sentinel (87), Water Quality (16) (some gages serve multiple goals)
  • Existing Gage Network of 312 stations
  • Difficult to make comparisons between national and regional studies because criteria are different
streamflow information in texas31
Streamflow Information in Texas
  • Texas as part of the National Streamflow Information Program
  • Gage network analysis in Texas
  • Streamflow information system
streamflow information system
Streamflow Information System

“The stream gaging activity is no longer considered a network of observation points, but rather an information system in which data are provided by both observation and synthesis”

(Fontaine et al, 1984, “Cost Effectiveness of the Stream-Gaging Program in Maine”, USGS Water Supply Paper 2244)

streamflow information in space and time
Streamflow Information in Space and Time

Current

Future Possibilities

Time

Real Time data

Historical daily

mean discharge

Streamstats

Streamflow statistics

At Gages

Anywhere on a Stream

Space

numerical weather prediction north american regional reanalysis
Numerical Weather Prediction(North American Regional Reanalysis)

Precipitation

Evaporation

3 hour time steps, 32 km grid, 1979 -- 2003

real time bacteria estimation
Real-time bacteria estimation

Kansas River at DeSoto, KS

point design model

Gage

Point Design Model

Site gages so as to accurately measure the vertical

flux (e.g. precipitation) over a domain

Domain

coverage design model
Coverage Design Model

Take a space and subdivide it into subspaces

with an area for each point e.g. service areas

of fire stations (goal of 4 min response time to a call)

slide40

Coverages of the Guadalupe Basin

NWS forecast

Watersheds

(flooding)

Guadalupe

HydroNetwork

EPA TMDL

Segments

(water quality)

TCEQ water

availability points

(water supply)

instream flows in texas
Senate Bill 2 in 2001 Texas Legislature authorizes legal protection of instream flow

Study program on selected reaches underway

Review by National Academy

Instream Flows in Texas

Report released

Feb 8, 2005

senate bill 2
Senate Bill 2
  • Implementation is joint responsibility of TWDB, TPWD, TCEQ
  • SB2 says: “… conduct studies and analyses to determine appropriate…flow conditions [that]…support a sound ecological environment.”
  • Achieving this goal is scientific and institutional challenge for Texas
instream flow studies
Instream Flow Studies
  • Requires TPWD, TWDB, TCEQ to develop procedures for defining instream flow requirements
  • Implemented on priority study regions by 2010
  • Based on aquatic life analysis

Trinity

Brazos

Sabine

Guadalupe

San Antonio

Priority Study Regions

combining flows and biology

Criterion

Depth & velocity

Species groups

Habitat

Hydrodynamic

Habitat

SMS/RMA2

Data Collection and some statistics

Model

Model

Descriptions

ArcGIS

Instream

Flow

DecisionMaking

Combining Flows and Biology
biological gage
Biological Gage
  • A representative reach associated with a stream gage
  • Regular monitoring for aquatic life assessment
  • Scientific program for relating flow and ecological integrity
conclusions
National: number of stream gages steady, real-time rising

Texas: number of stream gages declining since peak of ~410 in 1972

Losing 6 gages per year to less than 290 currently

Conclusions

National

Texas

we need flows to support lots of different watershed coverages
We need flows to support lots of different watershed coverages

NWS forecast

Watersheds

(flooding)

Guadalupe

River Network

EPA TMDL

Segments

(water quality)

TCEQ water

availability points

(water supply)