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The super gage at Olmsted, Illinois (USGS station 03612600), which measures, records and transmits water quality every 15 minutes. Photograph by Donnie Keeling, U.S. Geological Survey.
A super gage gives real-time, continuous water-quality data at a stream gauge or groundwater well. Super gages are built to address specific threats — water-related health risks such as harmful algal blooms, floods, droughts and spills of hazardous substances — and help show how land use affects water resources.
Before super gages, scientists relied on samples sent to a laboratory — results took days or weeks, and critical peaks could be missed. A super gage combines real-time streamflow or groundwater level and continuous water-quality sensors with samples analysed in the lab, which check the accuracy of the real-time data.
What a super gage measures
Every super gage measures stream stage or groundwater level. The other sensors depend on its type:
| Type | Continuous sensors |
|---|---|
| Standard | 5 sensors: water temperature, specific conductance, pH, dissolved oxygen, turbidity |
| Nutrient | the standard 5, plus nitrate-plus-nitrite and orthophosphate |
| Harmful algal bloom | the standard 5, plus nutrient sensors, chlorophyll and phycocyanin |
| Sediment | turbidity |
| E. coli | specific conductance, water temperature, turbidity |
What the data are good for
Surrogate models. A surrogate is a continuous sensor reading used to estimate something managers care about but that is harder to measure. Super gage data let these be modelled and reported as near-real-time concentrations and loads:
| Measured | Estimates |
|---|---|
| turbidity | suspended sediment |
| nitrate plus nitrite | total nitrogen |
| turbidity and specific conductance | total phosphorus |
| water temperature, specific conductance and turbidity | E. coli |
Figure 1. A, computed suspended-sediment concentration and measured turbidity; B, computed suspended-sediment load and streamflow, at the White River at Hazleton, Indiana.
Judging conservation practices. Nutrient super gages, with nitrogen and phosphorus sensors and analysers, show both the immediate and cumulative effects of conservation practices on a watershed's water quality. Edge-of-field monitoring traces how nutrients move from field to stream and respond to rain. Because the data are public straight away, farmers can better judge when to apply fertilisers and pesticides so they stay on the field instead of washing off at a cost.
Early warning. Super gages help water managers build real-time alerts for changes that could affect drinking-water treatment or recreation. When a fire sent thousands of barrels of bourbon into the Kentucky River in July 2019, the super gage at Lockport, Kentucky, recorded the effect every 15 minutes and showed when the river recovered.
The Kentucky River downstream of the Lockport super gage (USGS station 03290500). Photograph by Faye Peters, U.S. Geological Survey.
Nutrient reduction. Frequent measurements improve estimates of nutrient loads, helping target and assess reduction strategies. In Kentucky, USGS super gage data were key to building the state's nutrient reduction strategy and measuring loads entering and leaving its major river basins.
Groundwater and streams. Super gages paired with wells that monitor water quality continuously show how much groundwater contributes to rivers. How much legacy nitrate in groundwater reaches streams is largely unmonitored — important in Kentucky's karst, because conservation practices cannot touch nitrogen already in groundwater.
Why a state needs a network
A 2007 National Research Council report found the lack of data on river systems one of the biggest obstacles to managing the nation's rivers — and many nationally funded monitoring networks have since been cut or eliminated. Strong partnerships between the USGS and state and local governments can build networks tailored to each state's needs, and well-placed super gages are among the most cost-effective ways to address threats to water: checking impaired streams against their mandated total maximum daily loads, protecting vulnerable groundwater, and understanding the sources, pathways and timing of non-point-source pollution.
Sources
- Crain, A.S., 2020, The importance of U.S. Geological Survey water-quality super gages: U.S. Geological Survey Fact Sheet 2020–3019, prepared in cooperation with the Kentucky Governor's Office of Agricultural Policy. https://pubs.usgs.gov/publication/fs20203019
- The type and surrogate tables, figure and photographs come from the fact sheet's PDF, which the web version garbles.
- Rewritten in hubnx's own words.
Licencia: CC0 1.0 (dominio público) · Adaptado de pubs.usgs.gov
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