Watching the Gauge

The United States Geological Survey (USGS) has a network of stream gauges across the country.  These report stream conditions in real time, which you can follow on the USGS website.  There is one station on the Portage River at Woodville, and the data can be viewed here: http://waterdata.usgs.gov/usa/nwis/uv?04195500

If you clicked that link, you’re now looking at a page full of charts with squiggly blue lines that don’t necessarily tell you anything useful.  The first thing to notice is the dates – the default is to show the last 7 days of data.  If you want to change that, there are two places to enter dates within the blue bordered box near the top of the page.

Moving down the page, the first two graphs tell us how much water is moving through the river.  The first one is discharge, or the volume of water that will flow past you.  It is measured in cubic feet per second, or CFS.  Typically in early July, the Portage River is flowing at around 50 CFS, or about 375 gallons per second.  That is roughly the same volume of water as a train tank car moving past you once every 10 seconds or six cars in one minute.  During the flooding we experienced in the second week of July this year, the discharge increased to over 6000 CFS, which is close to four tank cars passing you every three seconds, or 80 in one minute.  The second chart gives the gauge height in feet.  This is simply a measure of how deep the water is at the gauge.  Each gauge also has a defined ‘flood stage’ which is shown by the horizontal red line.  If the blue line is above the red line, the river is flooding.  If the blue line rises steeply, that represents a dangerous flash flood.  Encouraging rapid draining of upper parts of a river system will cause faster and deeper floods downstream.

The next graph shows water temperature.  In the summer, there is a daily variation due to the heating effects of the sun.  Flood water also tends to be warmer in part due to the heat it absorbs from the land before it reaches the river.  Dark roofs and asphalt can absorb quite a bit of solar energy and will release that to any water that runs across them.  Lower water temperatures are healthier for the organisms which live in the river, and protecting streamside forests can buffer the effects of the sun.

Specific conductance is a fancy way of saying how good the water is at conducting an electrical current.  This may seem like a weird thing to measure since we’ve always been warned about water and electricity, but pure distilled water won’t conduct electricity.  Once any sort of ion is introduced, the water can then conduct electricity, so conductance tells us the “total dissolved solids” load of the river water, or how much other stuff has been dissolved in it.  This number usually drops after large rains, just because of dilution.  Heavy use of road salt in the winter can cause sharp rises in specific conductance if the snow melts suddenly.  Inorganic fertilizers can also increase specific conductance.

Dissolved oxygen is important to any gill-breathing organisms in the water, since it measures how much oxygen is available to them.  Plant photosynthesis and turbid flow (water mixing with air as it flows around rocks or other objects) add oxygen to water.  High temperatures, decaying plants or animals, and stagnation remove oxygen from water.  Some species are more sensitive to low dissolved oxygen than others, so we can collect invertebrate species and use them to measure water quality.

pH is the standard way to report how acidic water is.  Most aquatic plants and animals do best when the pH is closer to 7, and a swing either up or down can cause things to die off. 

Turbidity is a measurement of total suspended solids, or the amount of particles being carried along by the water.  Turbid water means that somewhere upstream someone is losing soil, either from a ditch bank, a field, a stockpile, or a construction site.  This sediment will eventually settle out, and when it does, it can cause a problem for bottom-dwelling organisms and fish eggs.  Sediment can also clog a river’s mouth, requiring more frequent dredging to maintain shipping and recreational boating access.  Turbid water also carries pollutants which are bound to the particles of sediment. 

So in summary, we can tell quite a bit about current conditions just by reading the gauge.  Ideally, we’d like to see discharge and gauge height near their historic averages.  A high reading on either one of these means property damage in low-lying areas.  A low reading indicates drought conditions, which is bad news for farmers.  Lower temperature and specific conductance (dissolved solids) are also indicators of healthier river conditions.  We’d like to see dissolved oxygen as high as possible, pH to stay near 7, and turbidity (suspended solids) to be as low as possible.

Most river gauges are not as detailed as the gauge on the Portage River in Woodville, however more gauges are planned for the Maumee River as part of an effort to understand the impacts of urban and rural runoff on water quality in Ohio’s rivers and Lake Erie.  If you would like to check out other river gauges in Ohio, click here: http://waterdata.usgs.gov/oh/nwis/rt