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Fishing: How To Fish: Advanced: Fly Fishing
USGS Offers Tips on Using Streamflow Information
They stand among the sycamores and rhododendron bushes along West Virginia's rivers.Some look like rustic tool sheds; others are sleek stainless steel boxes. On the outside, sophisticated antennas point toward satellites flying 22,300 miles above the earth; inside, advanced electronics hum with data.
These USGS streamflow-gaging stations provide valuable information for river recreationists. Using the current streamflow-data web pages available at http://wv.usgs.gov/ can mean the difference between a wasted trip to a bone dry stream channel or a thrashing ride down some of West Virginia's best white water.
The U.S. Geological Survey maintains 100 stream gages throughout West Virginia. Currently, data from 87 of these gages appear on the World Wide Web every four hours. Many of the stations report both a river's stage and its discharge. By using this information, river recreationists can better plan their trips and make efficient use of their time on the river.
Streamflow information is usually presented in two ways--river stage and discharge. Whitewater guidebooks often use river stage to evaluate rafting conditions. Many believe that by using stage you can quickly determine how much water is in the river and make an informed decision about whether or not to raft that day. But by using only stage as a reference,paddlers can be mislead.
River stage and discharge are not the same. River stage refers to the height of the water surface above an arbitrary reference point set at the river gage. The USGS develops a mathematical relation between the river's stage and actual measurement of its discharge. This mathematical relation is then used to determine discharges for all stages recorded at the gage.
Stage refers only to the specific pool where the gage is found and not to the entire river. And, most importantly, stage does not refer to water depth. River depth and discharge can change without corresponding changes in stage. In short, a river can have more or less water flowing in it but stage may not change.
During periods of heavy flow, a river bottom can "scour" or erode. Water eats away the rocks and sediment at the location where the river is gaged. Because the channel is now deeper and wider, the river has more flow, but the stage has not changed. The opposite can happen also. Stage can change without an increase in flow. For instance, during the summer of 1999 drought conditions on several rivers caused aquatic grasses to grow across the "control," the downstream section or tail of a pool that controls the stage. These grasses caused a natural dam on the pool and forced the stage to rise by two feet, but flow did not increase.
To accurately see a river's conditions on a particular day, paddlers and anglers should note a river's discharge. Discharge, often measured in cubic feet per second (cfs), refers to the actual volume of water flowing through the river. By using discharge as their point of reference, river users will better understand conditions on the whole river, rather than on just the gaged pool.
River users should also note a river's conditions over the seven day period that is presented on the USGS web site. By watching river fluctuations for several days, anglers, for example, can see if a river is falling and when it might be wadeable again after a high flow. Paddlers can note a river rising and better plan the time and location of their next outing. For instance, before running the lower New River from Cunard to Fayette Station, go to the UGSG web site and check discharge for the New River at Thurmond Station. There you'll see real-time information about discharge and stage and better prepare yourself for the trip ahead.
Recreationists may also want to keep their own log of river conditions. Look at the web site before and after a trip to the river and jot down the discharge and stage. Once you have a personal history, you can make a more informed decision about your trips. Soon you may be able to notice the subtle differences in your favorite stretch of river at slightly different flow volumes.
When using stream flow information of any kind, always keep in mind that rivers are dynamic systems. They change over time, often rapidly. You never see the same river twice. But by using the USGS web site, you may see the changes as they take place. Remember also that any information presented on the USGS web site is provisional and subject to significant change. Several times each year, the USGS measures discharge with current meters at the river gages. These measurements are then used to check the relation between stage and discharge. The stage versus discharge relations may change and not be shown in the web information until the flow measurements define the new relations. Data are considered provisional until reviewed and published.
The USGS streamflow-gaging program in West Virginia began in 1879, the year the U.S. Geological Survey became an agency. At that time, the USGS started maintaining a gage on the Kanawha River at Kanawha Falls. Constructed by the U.S. Army Corps of Engineers in March 1877, this gage has recorded daily average flow every day for over 120 years. During the drought of 1999, the station recorded some daily flows lower than any corresponding day in that 120-year period.
The USGS built many gages in West Virginia between 1895-1905. For most gages the period of record, amount of time that data at a particular site have been recorded, dates back to 1895. Today, the USGS and other agencies use this data for many projects such as estimating the magnitude and frequency of current and historic floods, water-quality studies, and to plan and design construction projects such as reservoirs, levees, or highways. Funding for the USGS streamflow-gaging network in West Virginia comes from a cooperative program primarily among the USGS, Army Corps of Engineers, and the State of West Virginia.
For further information about USGS stream flow data or other USGS activities in West Virginia, contact them at (304) 347-5130 or email [email protected].
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Written by Matt Cooke, USGS, Charleston, W. Va.
This information provided by USGS
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