Lecture 7: Fluxes and Streamflow

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Lecture 7 Fluxes and Streamflow

• Some review of flux units and computation for
  homework 2
• National Streamflow Information Program
• Reading Executive Summary from NSIP report
  http//www.nap.edu/books/0309092108/html/

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Precipitation and Evaporation Fluxes
Evaporation, E, and precipitation, P, fluxes In
the NARR are stated as mass fluxes in kg/m2-s
1 kg/m2-s 86400 mm/day
1 kg/m2-3hr 8 mm/day
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NARR-A, July 2003, 3 hour data
1 kg/m2-3hr 8 mm/day
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National Streamflow Information Program

• NSIP applied to the United States
• Texas Stream Gage Assessment
• Streamflow information in time and space

National Academy Press http//www.nap.edu
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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,

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NSIP GoalsWater Management and Regional Hydrology

• 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,

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Interstate and International Waters(515 gages)
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2. NWS Forecast Sites(3244 Gages)
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3. River Basin Outflows(450 gages)
For Water Budgeting
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4. Sentinel Watersheds (874 Gages)
Regionalization and Long Term Trends in
Streamflow (stations measuring natural flow in
undisturbed lands)
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5. Water Quality (210 gages)
NAQWA, NASQAN, .
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All NSIP Stations (4424 gages)
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Source of NSIP Gages

• 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)
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Number of NSIP Gages
Rhode Island (2)
Delaware (4)
Kansas (166)
Colorado (171)
California (201)
Texas (416)
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1980s Gage Network Goals

• Regional Hydrology relating basin
  characteristics to streamflow under natural
  conditions
• Hydrologic Systems water accounting including
  diversions, return flows
• Legal Obligations treaties, compacts and
  decrees
• Planning and Design dam, levee, water supply,
• Project Operation reservoir releases,
  hydropower
• Hydrologic Forecasts floods, flow volumes
• Water-Quality Monitoring NASQAN
• Research gages for specific studies
• Other recreation, canoeists, fishermen

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Comparison of Goals
NSIP Goals
1980s Goals

• Regional Hydrology
• Hydrologic Systems
• Legal Obligations
• Planning and Design
• Project Operation
• Hydrologic Forecasts
• Water-Quality Monitoring
• Research
• Other

• Sentinel Watersheds
• River Basin Outflows
• Borders and Compacts
• No
• No
• NWS Forecast Sites
• Water Quality
• No
• No

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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

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NSIP Goal 416 daily stations
Existing 312 daily stations, 17 annual peak
stations
1962
1970
1900
1920
1940
1930
1950
1960
1980
1990
1910
Figure 1
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Texas Stream Gaging Network
Active Stations
Discontinued Stations
Figure 2
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River Basins and Hydrologic Regions
Figure 3
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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

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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
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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

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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 gt 0.9
• 43 of 129 station pairs analyzed for 25 year flow
  have correlation coefficient gt 0.9
• Select stations for core network that are not
  highly correlated with other selected stations

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Interstation Correlation of Mean Annual Flow
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Interstation Correlation of 25yr Peak Flow
Figure 12
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Results of Texas Study

• Proposed core network of 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

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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)
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Current Stream Gaging Network( 7000 gages of
which 3000 are in NSIP)
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Water Watch Real Time Data( 5000 gages)
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Streamstats
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Streamflow Information in Space and Time
Future Possibilities
Current
Time
Real Time data
Historical daily mean discharge
Streamstats
Streamflow statistics
At Gages
Anywhere on a Stream
Space
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• Data Collection
• Stream gages
• Intense data collection during extreme events
• Water quality

• Stream Information
• Flow,
• Velocity, width, depth,
• Sediment, N, P, bacterial loads

Stream Information Cycle
Gaged point
Ungaged point

• Data Management
• Tabular, statistics, unit values
• Quality assurance
• Aerial photography, satellite imagery

• Information Dissemination
• Internet (Water Watch, Streamstats)
• Reports
• Telemetry using radio, satellite

• Information Generation
• Regional regression equations
• Data assimilation and modeling
• Estimation at ungaged sites

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Point Design Model
Site gages so as to accurately measure the
vertical flux (e.g. precipitation) over a domain
Domain
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Network Design Model
Site gages so as to measure flow through a stream
network (Horizontal flux vs vertical flux)
Siting of a set of gages partitions drainage
basin into a set of subbasins for each gage
A gage supports flow estimation upstream and
downstream of its location on the stream network
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Coverage Design Model
Take a space and subdivide it into subspaces With
an area for each point e.g. service areas of
fire stations
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Coverages of the Guadalupe Basin
NWS forecast Watersheds (flooding)
Guadalupe HydroNetwork
EPA TMDL Segments (water quality)
TNRCC water availability points (water supply)
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NSIP

• NSIP design is a combination of the network and
  coverage design models
• Each of the five goals has a set of gage points
  and a corresponding drainage area coverage
• Intersection of these five drainage area
  coverages for each goal defines the NSIP drainage
  area coverage
• Gage provides point flow information on a stream
  at a point and also of the flow increment between
  this location and that of adjacent stream gages.

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San Marcos basin as a coverage model