Nutrient Loss Reduction Strategy Research Library

  • 2021 U.S. Geological Survey Continuous Loadings Network Update

    Sep 1, 2021 1:00 pm by Paul Terrio2021 Biennial Report

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    • Photo of USGS Staff working with a supergage.
    • Figure 3.9

    Since 2015, the U.S. Geological Survey, with financial assistance provided by Illinois Environmental Protection Agency, has operated a network comprised of “super gages” that provide real-time continuous monitoring of eight major rivers in the state (Figure 3.9 and Table 3.5). Each super gage continuously measures river discharge, along with nutrient and suspended-sediment concentrations to calculate continuous loadings. Nutrient and suspended-sediment loads were computed for the 2016- 20 water year period using a statistical modeling approach. These load estimates represent the riverine loads at the locations of the eight monitoring stations and include parts of the Illinois, Rock, and Vermilion River basins that receive drainage from neighboring states. The loads do not include an estimate of ungaged areas of the state. The cumulative drainage area of these gaging stations covers approximately 74% of the total land area of Illinois, as well as portions of Wisconsin and Indiana. The statistical modeling procedure provides a means to both determine and reduce uncertainties in load estimates computed from continuous data with data gaps. The load estimates are currently under review and awaiting approval; a report describing the modeling procedures and results is scheduled for publication in 2021. A detailed comparison of load estimates using this procedure and load estimates computed from discrete water quality data is forthcoming.  

    For the 2016-20 water year period, the provisional mean annual nitrate-N load was 426 million pounds N per year; the provisional mean annual total phosphorus load was 30.2 million pounds per year; and the provisional mean annual suspended-sediment load was 8.32 million tons per year.

    Photo of USGS Staff working with a supergage.

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    Figure 3.9

    Figure 3.9. Drainage basins and locations of the eight nutrient monitoring stations

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    River

     USGS ID

    Station Drainage Area 
    (km2)

    Station Drainage 
    Area in Illinois     (km2)

    Basin Drainage 
    Area in Illinois (km2)

    Percent of Station Drainage 
    Area in Illinois

    Areal Percent of Illinois

    Vermilion

    03339000

    3,341

    3,105

    3,372

    93%

    2.1%

    Embarras

    03346500

    6,042

    6,042

    6,307

    100%

    4.2%

    Little Wabash1

    03381495

    7,998

    7,998

    8,298

    100%

    5.5%

    Rock

    05446500

    24,732

    10,290

    13,789

    42%

    7.1%

    Green2

    05447500

    2,598

    2,598

    2,927

    100%

    1.8%

    Illinois3

    05586300

    69,264

    58,666

    64,009

    84%

    40.2%

    Kaskaskia

    05595000

    13,439

    13,439

    15,045

    100%

    9.2%

    Big Muddy

    05599490

    5,592

    5,592

    6,180

    100%

    3.8%

    Table 3.5. Monitoring station information

    1 Drainage area numbers are for Little Wabash River at Carmi, IL (USGS ID 03381500).
    2 The Green River is part of the Rock River drainage basin. The 2,927 km2 is part of the 13,789 km2 Rock River drainage area in Illinois.
    3 Drainage area numbers are for the Illinois River at Valley City, IL (USGS ID 05586100).