Web Exercises

Stream Flow Data

Stream gauging stations, which keep records of water flow in streams for many years, are one of the most important tools we have for understanding water resources. Stream gauge records are used  to estimate water availability for drinking and for irrigation, pollution levels, and many other types of information. In the US, the United States Geological Survey maintains a vast network of stream gauges.

Go to the USGS real time stream guage page. This page shows a map of today's water flow compared to normal conditions for this time of year. Each dot represents a guaging station. Look at the map explanation below the map. Which colors represent unusually high flow rates? Which color represents approximately normal flow rates (25th to 75th percentile)? Which colors are low flow? Which colors predominate in your area today?

Just below the map are options for retrieving data. Click on the "State map" button. Then click on your state. (If your state is below freezing or very dry this month, use a different state.) This will lead you to a map of colored dots for the state you chose. When the state map loads, click on a colored dot near you on the map. (If any information is missing for the questions below, try selecting another site.)

1. When you click on a dot you will get information on streamflow for that station. The first graph is streamflow--the amount of water in the stream today, in cubic feet per second. Note the numbers on the vertical axis. Is the stream flowing in tens of cubic feet per second? Hundreds? Thousands? How does today's flow compare to the median flow (blue triangles)? Has the flow been high or low for the past month?

2. The second graph is stage, the water level (why is this not exactly the same as flow rate?)
How high is today's water level compared to the past month?

3. In some states, most sites have a third graph showing rainfall. If your site does, look at the second and third graphs together. Are there any rainfall events (spikes in the rainfall graph) that help explain highs in the "stage" graph? Based on the rainfall graph, does most of the water in the stream at this gauging point come from rainfall here or somewhere upstream?

4. Now hit the "back" button to go back to the state map and look at several different gauging stations (colored dot) in a different areas of your state. Which part of your state is driest? Which region is wettest? Are the numbers in different regions similar, or is flow at some sites several times greater than at other sites? Do most sites have fairly constant flow, or do some have dramatic peaks and valleys? What generalizations can you make about surface water availability in the state?

Find out where your water comes from.
Go to http://www.epa.gov/surf2/surf98/wimdw.html
Enter your county and click Submit. Select the county name in your state, and then find the Watershed Name for your community. Click on the Index of Watershed Indicators, (provided by the EPA). How big is your watershed? How vulnerable is it?