Typical USGS water-monitoring site

There are many pieces of equipment, both mechanical and electronic, that are installed at U.S.Geological Survey (USGS) water-monitoring sites to measure, record, and transmit both water-quantity and water-quality information. USGS's National Water Information System (NWIS) provides access to water-resources data collected at approximately 1.5 million sites in all 50 States, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands.

Description of the USGS real-time streamflow system. (new window)

Stream-stage monitoring instrumentation

This picture shows one type of USGS gage structure which is attached to a stilling well (the vertical pipe), and the shelter contains measurement and data-transmission instruments. Equipment in the gage house continuously measure stream height (stage) every 15 minutes. Stilling wells are used at locations where they can built next to the stream, but other systems monitoring water pressure can be used in different situations.

The box on top of the pipe contains a measuring instrument (data logger) that has a pulley with a metal tape holding a float at one end. As the water in the stream rises and falls, the water in the vertical metal pipe also moves and the float on the wire goes up and down with the water level. As the wire moves, the pulley turns, which changes the stream-stage (gage height) reading. The stream-stage readings are recorded by the data logger. Many sites have a solar-powered GOES satellite system that transmits and uploads stream-stage and water-quality measurements directly to USGS databases to give virtually "real-time" readings of stream stage, streamflow (computed using the stream stage/streamflow relation), and water-quality measurements.

Water-quality monitoring instrumentation

USGS monitors many streams in urban settings, as they can be affected by the pressures of urban development, and thus, the potential for water-quality problems are high. Possible sources of problems are:

• Sediment runoff from construction sites
• Potential pollution from runoff from roads and parking lots
• Inflow of warmer water from impervious surfaces (roads, parking lots)
• Fertilizer (nitrogen and phosphorus) runoff from yards and gardens
• Bacteria and pathogens from animal and human wastes
• Runoff containing pesticides and pharmaceutical residue
• Industrial wastes
• Trash

It is important to monitor water quality not only to establish baseline water-quality information about a stream, but also to allow for timely notification when water quality changes. This picture shows an automated water-quality monitoring site. The white tube on the right contains probes and instruments submerged in the stream. The structure on the left houses the data-transmission and automated stream-sampling and storage equipment.

The tube shown in this picture contains probes that continually measure temperature, specific conductance, dissolved oxygen and pH. It also contains tubes to collect water samples during storm events and store the samples in the refrigerated housing structure. It is important to sample the water during storm events, because it is during high water that some water-quality problems, such as high levels of bacteria, sediment, and nutrients (nitrogen and phosphorus) occur.

 Another website about measuring streamflow.

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