Stream Stewards – Temporary streams help save the Bay
Jake Hosen, University of Maryland, gave a great talk on streams and what keeps them healthy on Thursday night (4/4), and followed it up Saturday morning with a guided walk through the flood plain of Cedar Run on Merrimac Farm to view the streams there.
Streams that flow year-round are known as perennial streams, while temporary streams have no water flow during some portion of the year.
There are two types of temporary streams. The first are intermittent streams which do not flow year round but are fed by groundwater during some portion of the year. The second type, ephemeral streams, receive water only from rain and never from groundwater so they usually flow less often than intermittent streams.
It turns out that streams are not only lovely to look at, they have many interesting characteristics. Streams are ubiquitous – there are approximately 1.6 million miles of 1st order streams, which are the smallest streams in a river network. Overall, in the continental United States and Hawaii a remarkable 59% of stream length is estimated to be temporary.
According to Jake, who studies the ecology and hydrology of temporary streams in the Parker’s Creek watershed on land protected by the American Chestnut Land Trust, streams sequester excess nutrients from water before it reaches larger water bodies, such as the Chesapeake Bay. So, healthy streams contribute to a healthy Bay.
If, in your traipsing through nature, you come across a sparkling, crystal clear stream gurgling its way toward the Mississippi (America’s only 10th order stream) or other large body of water, know that as beautiful as it is, the reason it’s clear is that it contains little organic material and so, few living organisms.
Conversely, the muddier streams are teeming with life. A stream bottom covered with leaf litter and other organic matter in various states of decay (this material is called detritus) may seem mucky, but it’s an important food source for stream organisms. Leaf litter becomes food for bacteria and insects, which become food for the larger inhabitants of the neighborhood, such as crawfish, amphibians, and birds.
As Jake was talking about temporary streams being dry for months at a time, I wondered what becomes of the creatures that lived in the water. Some, such as stoneflies, may develop into flying adults more rapidly so that they can leave the stream before it dries out. Others hide under rocks and leaves. Crawfish dig deep burrows in the stream bed or stream bank to a depth that will remain moist until water refills the stream above; these burrows may even be occupied by other opportunistic organisms seeking moisture, creating a sort of multi-species condominium to wait out the drought. Still other organisms become an unwilling buffet for predators as they are stranded in the drying streambed.
At Merrimac Farm, we had a beautiful spring day for the walk through the forested floodplain of Cedar Run and Jake pointed out many examples of the stream characteristics that he had spoken of two nights before.
For example, often only sections of a temporary stream will go dry, while other, deeper parts will retain water. One large stream we viewed at Merrimac was in this condition because of lack of water over our unusually warm and dry winter and spring. In fact, much of the floodplain and wetland areas at Merrimac were dry, meaning a probable reduction in the amphibian population for the year as these areas are important breeding areas for frogs and other amphibians. Cedar Run itself was also low.
On the bright side, the bluebells, for which Merrimac Farm is famous, were in riotous bloom. There were tiny violets and dogwoods blooming, and the promise of wild iris in a few weeks. The dogwoods planted last fall in Merrimac’s landscape conservation garden were also in bloom.
These events were part of Prince William Conservation Alliance’s Stream Stewards program, a free program made possible by community donations and the support of PWCA members. For a complete schedule of the program, go here.
Merrimac Farm’s annual Bluebell Festival will be held next weekend, Sunday, April 15, from 10:00 am to 4:00 pm. In addition to a walk through the bluebells, there will be wildlife exhibits, some of Northern Virginia’s best naturalists will be leading tours, and there will be many family-friendly activities. We would love to see you there!
For a calendar of upcoming PWCA events, go here.