|Low-flow wading measurement on the Little Klickitat River.|
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Ecology's Statewide Flow Monitoring Network
Ecology's Stream Hydrology Technical Coordination Team provides provides timely and accurate instantaneous streamflow data for various in-stream actions. These instantaneous streamflows are an integral element in determining the in-stream resources available for fish and out-of-stream resources available for people. The driving forces behind the increasing need for accurate and timely streamflow data are the Endangered Species Act, salmon-recovery efforts, and an increased focus on water-resource management.
The Stream Hydrology Team also provides flow information to support water-quality monitoring efforts within the Department of Ecology. Instantaneous flow measurements (discharge) are an important element of both River and Stream Water Quality studies and Total Maximum Daily Load (TMDL) studies for Water Quality Improvement Projects.
Discharge measurements are used to address two issues. The first issue is the variability intruded into water-quality parameters that are directly influenced by seasonal and annual flow patterns. The removal of this variability (flow adjusting or normalizing the parameter with respect to flow) often enhances our ability to detect long-term changes (trends) in water quality. The second issue is the parameter-specific relative contribution (load) or flux from a stream with respect to its receiving water. In both cases, it is paramount that the discharge measurement be as accurate as possible.
The team does not measure river/stream discharge each time water-quality information is collected. Instead, they rely on two methods to estimate streamflow at the time of sampling. The first is to gather this information from stream gages operated by other governmental agencies, primarily the US Geological Survey, the Corps of Engineers, and the Bureau of Reclamation. The second method is to create rating curves that relate river stage to discharge following a formal set of procedures that are included in the Quality Assurance Monitoring Plan. Where this method is used, the river stage is measured and recorded when the water-quality sample is collected. In addition, at least six to eight times per year, they measure streamflow and record the corresponding stage. These measurements are made at various stage heights encompassing the recorded stage during the water-quality sampling. The instantaneous flow measurements are then plotted against stage height to develop a rating curve for each measurement site. Ideally, this rating curve covers the full range of the stage heights recorded during the sampling.
Discharge measurements are made using two primary methods. Low flows are measured by in-stream wading measurements, and high flows (non-wadable) are measured from a bridge with standard bridge equipment or an Acoustic Doppler Current Profiler (ADCP). The ADCP can be deployed using a tow-raft or, for larger applications, from a jet sled.
Flow measurements and continuous stage records are archived in a streamflow database and are reported through the Flow Monitoring Network.
The operation of Ecology streamflow stations falls into three types: Telemetry, Stand Alone, and Manual Stage Height. The specific type determines the availability of data for each streamflow station.
A telemetry station logs stage height every fifteen minutes and transmits this data in three-hour blocks to the Department of Ecology Headquarters in Olympia, Washington via a satellite transmitter or a standard dial-up modem. This data is automatically imported into the streamflow database.
A stand-alone station logs data every fifteen minutes and is downloaded once a month. Data is imported into the streamflow database manually and automatically published to the Ecology website. Stand-alone stations are typically operated for up to or less than one Water Year (October 1 - September 30). Streamflow data from both active and historic stand-alone stations are included on the website.
A manual-stage-height station does not produce a continuous record but is typically only a single point in time measurement. Stage height is directly read from either a standard staff gage, wire weight gage (WWG) or measured from a reference point (RP). A RP is a point located somewhere over the wetted width of the station cross-section from which a measurement can be made to the water surface. Manual-stage-height measurements are converted to instantaneous streamflow using a rating table or flow curve. Rating tables or flow curves for each of these stations are built based on the relationship between a series of periodic stage-height measurements and their corresponding in-stream flow measurements.
Temperature data collected by the team is measured using two types of probes. The first is an internal thermistor within the submersible SDI-12 pressure transducer. The SDI-12 probe uses water temperature to correct for the change in pressure response due to temperature and adjusts the final pressure accordingly. The nominal accuracy of this built in thermistor is + 1 Degree C. However, side by side comparisons with TidBit temperature probes have found the internal thermistors to be within + 0.2 degrees C.
Stations where a self-contained bubbler is used to measure stage height have a separate thermistor probe for measuring water temperature. The nominal accuracy of these probes is + 0.2 degrees C.
Both probe types are deployed within a 2" galvanized slant pipe that extends from the gage house into the stream channel.
Current Water Year data provided by the Washington State Department of Ecology, including stream discharge and water-level values, are automatically generated by remote equipment and have not been reviewed or edited for accuracy. Inaccuracies in the data may be present due to instrument malfunctions or physical changes to the discharge measurement sites. End-of-water-year review may result in significant revisions to the data. Please exercise caution and carefully consider the provisional nature of the information provided.
During extreme cold weather, river stage may be affected by ice. As a result of the changing channel characteristics, incorrect discharge data will be computed from the stage data. Please review associated water and air temperature data where available.
During periods of warm weather, river stage may be affected by the rapid growth of aquatic plants. As a result of the changing channel characteristics, incorrect discharge data will be computed from the stage data.
|Ecology's Statewide Flow Monitoring Network|
A designated contact for additional information is provided on each station page. Stream Hydrology Team contacts are listed as follows.
Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.html.