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How Much Groundwater Do Delaware’s Wetlands Hold?

Written on: November 25th, 2015 in Wetland Assessments

Groundwater and Delaware’s Wetlands

Approximately 71 percent of the Earth’s surface is covered in water, and it makes an incredible journey around the globe. Water can travel up into the atmosphere and back down into the land; moving from plants, to clouds, to soils, and can even make its way underground. Water that is stored under the soil is called groundwater, and clean, drinkable groundwater is a highly sought after natural resource.

But how can groundwater be cleaned you ask? Before water travels to underground storage units (aquifers), it can first go through, and be filterd in our wetlands. As water moves down through wetland soils, nutrients, such as phosphorus and nitrogen, and sediments are filtered out, purifying the water.

Just one acre of wetlands can store as much as 300,000 gallons of water, but water levels vary greatly depending on the season. During the wetter months of winter and spring water can be seen on the surface, while during the dryer months of summer and fall you may not find water in wetlands until you start digging. To track these changes, we will establish a long-term dataset that monitors groundwater levels in Delaware’s wetlands.

But how do you measure how much water is in a wetland? Why, through the installation of wells of course. In late October of 2015, we installed a series of shallow water monitoring wells that began collecting data as part of a long term project to understand what is happening to groundwater levels in Delaware’s headwater flat and floodplain riverine wetlands. The data gathered from these well monitoring sites will help us place a value on some of the services wetlands provide, and better understand the ability of Delaware’s wetlands to store water, reduce flooding and create cleaner waters.

Well Installation

Three sites were chosen at each of the Ted Harvey Conservation Area’s flat wetlands and the Blackbird State Forest’s riverine wetlands. The well installation process began in the dry months of the fall when groundwater levels were at their lowest. This ensured that water would be present in the wells throughout the entire year. A straight 4 inch diameter hole was dug using an auger to a predetermined depth, 8 feet deep for the Ted Harvey Conservation Area, and 5 feet deep for the Blackbird State Forest.

After the hole was dug, a PVC pipe with tiny grooves cut into it to allow water to pass through was inserted, and then sand was filled in around the pipe to lock it in place. The tricky part was to make sure that the pipe was completely horizontal and at the correct depth.

After the pipe was secured, it was topped off with a clay bentonite mixture that sealed the PVC to the opening in the ground preventing rainwater from entering the well and skewing water level results. To measure and track the groundwater levels, waterproof dataloggers that automatically record temperature and pressure were installed underground at the bottom of each of the PVC pipes, and a reference one was installed above ground at each site.

We will come back to these wells periodically throughout the year to download the data, make sure everything is functioning properly, and if all goes “well,” gain some interesting insights to share.

Check out this short video of the well install process at the Blackbird State Forest.

Tags: Blackbird State Forest, groundwater, Ted Harvey Conservation Area, well installation, Wetland Monitoring & Assessment Program