- August 21, 2015
Vernal pools are in need of special attention by landowners. There is only limited protection under the Clean Water Act, which includes vernal pools as part of a larger floodplain area or those within 4000 feet of water already protected under the CWA jurisdiction. 1 While this is helpful for overall water quality, it does not encompass the vast terrain where vernal pools should exist. In general, wetland habitat has been reduced globally by 40%-90% due to human activities. 2
A variety of Vernal Pools across the landscape is ideal as a set of small wetlands can host more species than a single large wetland.
You can be a part of the solution by creating or encouraging vernal pools of various sizes and hydrologic regimes across your property. Some are dug below the water table, others use a small earthen dam to catch seeps, and many utilize artificial liners to hold rainwater and surface runoff. To determine if you could add a seasonal wetland, consider what type and where in the landscape it would work best.
Vernal Pools can be installed in almost any environment from forest to prairie and can be any size ranging from 3 to 15 meters in length and up to 1.5 meters deep. 3 Whether you are constructing a small pool dug with hand tools or larger wetlands excavated with heavy equipment, keep in mind these objectives for success when planning and constructing:
- Permits and Permission: Check with your county before you dig. Depending on local regulations, you may need a permit to ensure habitat for federally threatened or endangered species is not affected. Also, there may be buried gas and power lines if the site is near any roads or buildings.
- Locate wet areas: Usually a low position in the terrain and impermeable soil types like silty loam or clay will help collect and hold water during rainy seasons. Sand and gravel soils, or construction fill, will drain too quickly, putting the inhabitants at risk. To test, dig a hole at the site, 2’-3’ deep, and bring up a soil sample. The more you can squeeze and shape the soil without it crumbling apart, the more clay it has, and the more likely it will hold water, especially if the soil base is compacted during construction.
- Retain cover: Topsoil, leaf litter, and any sticks, logs or rocks should be carefully set aside and saved to be be reapplied later. This debris already has a large part of the biota needed to re-establish the fungal and microscopic communities necessary for vernal pool success.
- Contours: Curvy edges and a variety of depths applied to each pool will add light and temperature differences to create unique habitats and increase species diversity. Also, a variety of shapes and depths available across the landscape is ideal as a set of small wetlands can host more species than a single large wetland. 4
- Return vegetation cover: Saved topsoil, sticks, rocks, and native leaf litter 5 should be applied to the newly constructed edges. To prevent invasive plants from colonizing, native plants should be added immediately to stabilize soil, attract wildlife, and provide shade and cover. Larger pools could have logs and other woody debris partially submerged, providing cover, perches, and egg attachment sites.
The most important thing to remember is that vernal pools are inhabited seasonally and those inhabitants need a high-quality surrounding environment to spend most of their adult life. Constructed wetlands can also fail if they do not hold water long enough to establish vegetation or allow full stage development of its inhabitants. A failed vernal pool can be an ecological trap if it attracts breeding adults but does not contain all the elements to support multi-stage lifecycles. Close monitoring should be carried out for at least 5 years to ensure successful reproduction is occurring. 6
Add a Vernal Pool to Your Map
Those lucky enough to have large properties may find they include vernal pools. If you aren’t sure, make a plan to walk your property during your next wet season. For many this will be Spring, but for others in more moderate climates (like on the West Coast), this might be during a winter rainy season.
Use the water habitat type to map vernal pools ().
Set the characteristics for this object
Once you’ve added the pool to your map make sure to set the characteristics. Click on the object, and open the infowindow to access these settings under “characteristics.”
First set “running water” to “standing” water.
2nd, set seasonality to “seasonal.”
Don’t have a map yet? Start One Now
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- U.S. EPA. Clean Water Rule: Factsheet. Clear Protection for Clean Water. ↩
- Dahl T E (1990). Wetlands losses in the United States 1780’s to 1980’s. U.S. Department of the Interior, Fish and Wildlife Service, Washington D C ↩
- MORREALE, Stephen J., SULLIVAN, Kristi L. Community-level Enhancements of Biodiversity and Ecosystem Services. Higher Education Press. 2010 ↩
- Oertli B, Auderset J D, Castella E, Juge R, Cambin D, Lachavanne J B
(2002). Does size matter? The relationship between pond area and
biodiversity. Biological Conservation ↩
- STEPHENS, JEFFREY P., BERVEN, KEITH A., TIEGS, SCOTT D. Anthropogenic Changes to Leaf Litter Input Affect the Fitness of a Larval Amphibian. Freshwater Biology. 2013. ↩
- Calhoun, A. J. K., Arrigoni, J., Brooks, R.P., Hunter, M.L., Richter, S.C. Creating Successful Vernal Pools: A Literature Review and Advice for Practitioners. Wetlands (2014) ↩