It’s April. And while the cold temperatures here in New Jersey make it feel like spring hasn’t quite yet arrived, the flowers are starting to poke through the ground, reminding us that spring is coming, and with it, a steady stream of springtime showers should be on their way.
Of course, when rain falls on land, much of it ends up in rivers and streams. And thanks to a network of over 3,000 stream gages monitored by the U.S. Geological Survey, we can easily study how precipitation, including rain and snow, impacts local streams, rivers and estuaries.
All of this data is available on USGS’s WaterWatch web site, which features several easy to use maps, providing a great way to introduce streamflow data to students and the public, while showcasing how it can be used to monitor floods and droughts – critical issues related to human health, safety and well-being.
Here are a few great places to start.
Current Streamflow Map: This map displays the real-time conditions from all of the streamflow stations across the country. Some stations measure streamflow discharge or flow rate, while other stations measure gage height, that is, how high the water level is. A few stations even measure other things like temperature, pH and dissolved oxygen. From this map, you can select an individual station to view in detail, access raw data or create custom graphs.
On the map, each station is represented as a colored dot, whose color is based on how the current streamflow or gage height compares with past records. Reds designate those stations that are below average while blues are above average, and green dots represent those stations that are in line with historical norms. You can also view historical streamflow maps.
Drought Map: This map highlights which areas of the country have below normal streamflow conditions, typically due to long periods of time with limited rainfall or, in mountainous areas, low levels of wintertime snowpack. Below normal streamflow is generally a good indicator of whether a drought exists, though precipitation, ground water and reservoir levels are also taken into account when declaring an official drought. (See for example, New Jersey’s Drought Information Site.)
Flood Map: Sometimes, you can have too much of a good thing. This map shows those stations stations that are currently reporting conditions drastically higher than their historically normal levels. This can often happen after severe storms with large amounts of precipitation (which is especially true after tropical storms and hurricanes), but it is also common in the spring when mountain snowpack melts. And of course, some rivers are susceptible to a springtime a double whammy.
Personally, I’ve always wondered if a more appropriate phrase for this time of year might be “April flowers bring May showers,” but to make that case, I need to dig through this data some more.