Two basic methods are used to determine if there is sufficient water in a stream for boating and, if so, how much water there is above the minimum level.  First of all, there are the gauges installed by the US Geological Survey (USGS) for measuring water flows.  Then there is the canoeing gauge system developed by Randy Carter.

Randy Carter Gauges -  Randy Carter, a pioneer whitewater canoeist and author of the best of the early whitewater river guidebooks, devised a system of marking bridge abutments (or piers/footings) to indicate the amount of water available for paddling.  Randy canoed the streams in his book and noted the depth of the water in the widest, shallowest parts of the stream.  If there was barely enough water to get through without stepping out of the canoe, as a general rule, he considered the level to be zero for canoeing.  And he marked the bridges accordingly.

The Randy Carter gauge may appear confusing, but it must be remembered that his system indicates a zero level for canoeing ---not that there is no water in the river.  If the river is widest at the bridge where there are markings, then the canoeist's zero (on the gauge) will mean that there is about 7 inches of water flowing at this point.  If the river is narrow at the bridge and wide downstream, then there may be a foot of water flowing under the bridge where the RC gauge indicates a zero canoeing level.  As a point to ponder, Randy was one of the best canoeists in the nation when it came to paddling in low water.  So, canoeists must have a lot of experience in reading and paddling in low water to attempt a river at a level below the Randy Carter "zero" without walking through a lot of shallow areas.

 This system has been adopted by the Canoe Cruisers Association, Coastal Canoeists, Blue Ridge Voyageurs, and North Carolina Canoe Club for marking rivers.  The author uses the same system.


USGS Gauges -  Gauges have been installed at hundreds of locations throughout the state by the U. S. Geological Survey.  The gauges are checked periodically, some hourly by satellite, some daily by telephone, some daily by people who mail the reading to USGS, some weekly,  some only when the water is high, and some only when performing measurements on water flow.  These gauges are usually located near bridges and can be recognized by the metal silo (a drain culvert) that protrudes vertically from a spot near the stream.  The USGS topographic maps indicate the locations of the government gauges.

The readings from the USGS gauges for the Potomac, Shenandoah, Rappahannock, and James watersheds can be obtained from River Services, US Weather Service at 703-260-0305 or by going to the USGS web site or the Monocacy Canoe Club web site.  Or the same information can be obtained from the NOAA weather broadcast from Manassas on 162.55 mc.

The USGS gauge readings must be interpreted to determine the amount of water in the river--- i.e., if there is enough to canoe or if there is too much to canoe.  This process is quite simple if you know how much to subtract from the USGS reading to determine the water level for canoeing.  As a general rule, the USGS gauges are buried so that the river bottom is level with the 2.00-feet reading on the gauge; some USGS gauges read 3.00-feet at the river bottom; few read higher.

As an example of how to use the USGS gauges, assume you want to paddle on the Brocks Gap Section of the North Fork Shenandoah River and want to know if the river has sufficient water for paddling.  You refer to the gauge information in this book and learn that a reading of 3.5-feet on the USGS Cootes Store gauge means a zero level on that river.  You call River Services or check the web sites and learn that the Cootes Store gauge is reading 4.2-feet. You subtract 3.5-feet from 4.2-feet, and you know that the river has .7-feet (about 8.4-inches) of water above canoeing zero.  You can easily paddle the stream.