New Surface Water Gages

Establishing a New Surface Water Gage

"The footprint of a gage is small, but the impact immense," Ryan Rowland.

Establishing a new gage is not a simple task. It requires a lot of forethought, planning, and hard work to make it happen and to ensure its long-term success. The following considerations must be addressed throughout the process.  

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Step 1 - Why is the gage needed? Defining the purpose of the gage must be the first step. Common reasons new gages are needed include the following. 

• New reservoirs, roads, bridges, or drinking water and wastewater facilities are planned.
• Flood warning and drought monitoring is needed.
• Waterways or power production facilities need data to maintain minimum flows.
• Discharge needs to be monitored for water rights and transboundary needs and issues.

• Environmental conditions may need to be monitored to evaluate the impacts of changing land use and protect the safety of the public engaged in recreational activities.

   

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Step 2 - What is the best location for the gage? Evaluating potential locations is the second step. 

• Is the site suitable for the purpose it is being established?
• What are the river controls at various stages of water depth?
• Can discharge be measured at the site during low and high flow?
• Is there evidence of frequent stream channel changes, multiple channels, or overbank flow?
• Is there evidence of aquatic vegetation or beaver activity that will impede flow?
• Is the site accessible and is it free from safety hazards?

• Who is the landowner and are they amenable to the installation of a gage on their property?

   

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Step 3 - What kind of instrumentation will work the best given the site conditions? Determining the most appropriate instrumentation is an important third step. 

• Is a stilling well, radar gage, acoustic sensor, or pressure sensor to monitor stream stage (river height) best?
• Is a velocity sensor a good option?
• Would a passive device to record maximum stage be needed?
• Would a field camera to monitor stream conditions be helpful?
• Would water-quality data collection be included? 

Step 4 - Will the landowner permit the installation and ongoing access and operation of the gage? Obtaining official written permission and documenting the agreement among all parties is an imperative step. 

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Step 5 - How and where will instrumentation, equipment, and supplies be acquired? Knowing if and where instrumentation is available is critical to a successful installation. 

• Most instrumentation is obtained through the USGS Hydrologic Instrumentation Facility (HIF), where it is tested and approved for use.
• Equipment not available from the HIF is sourced on the open market from a variety of vendors.
• Construction materials are usually purchased locally.
• Some items, such as instrument mounts and shelters, are designed and constructed internally by talented hydrologic technicians, or are ordered from fabricators that can meet specifications at particular sites.

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Step 6 - Who will install the gage? Having the right crew and equipment is the only way to ensure a successful installation.

• Most surface water gages are installed by USGS hydrologic technicians. Installations usually require several technicians and several days to complete.
• Larger river or complex sites and gages may need contractors and heavy machinery to install infrastructure such as stilling wells, mounts, or cableways.
• Gage houses and instrument mounts are installed.
• Instrumentation, antennas (satellite, phone, or radio), and solar panels are installed and wired into the system.
• The system is powered up, and initial data are transmitted.

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Step 7 - Calibrating instrumentation is a critical step. Good data depends on it.

• Permanent Reference Marks are established (at least 3 and may include brass caps, post, stable rock outcrops).
• Precise levels are run to establish a gage datum reference surface (see USGS publication, Techniques and Methods 3-A19, for more information on gage datum).
• Stage instruments are set to gage datum.
• Water-quality instruments are calibrated and set accordingly.
• Meteorological equipment is generally calibrated by the manufacturer.

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Step 8 - Final steps include establishing communication so that discharge can be observed in real time from any computer or mobile device.

• Programs are initiated in the office to establish and decode satellite transmissions from the stream gage (see USGS Diagram of How Stream Gage Data is Transferred to the Internet | U.S. Geological Survey for more detail).  
• Initial streamflow measurements are made to begin establishing discharge ratings for the stream gage.
• Data are stored and presented online as “provisional."
• Data are analyzed, updated, reviewed, and published as “Approved.”

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