SPATIAL AND TEMPORAL ASSESSMENT OF HYDROLOGIC PROCESSES OF NEW ENGLAND VERNAL POOLS

Vernal pools in New England are discrete seasonal wetlands occurring in forests. These pools provide a home to a variety of amphibians and other aquatic life, including threatened and endangered species. Most vernal pool research has focused on their ecological significance, but lacks analysis of underlying hydrologic processes. Of the studies conducted on the hydrologic properties of vernal pools, little has been done to quantify groundwater flow in vernal pool systems. The investigation of hydrologic processes of vernal pools can offer integral information about their hydrologic connection to the surrounding upland environments.

This study will assess six vernal pools that have varying hydrogeological settings, with a focus on the importance of groundwater exchange to these pools. The long term goal of this work will be the creation of monthly water budgets over a twelve month period. To assess groundwater flow, shallow monitoring wells and stilling wells have been installed to measure vertical hydraulic gradients. Hydraulic conductivity will be measured using the Hvorslev piezometer testing method and combined with the vertical hydraulic gradients to estimate groundwater flow rates using Darcy’s law. Vertical arrays of temperature sensing data loggers have been installed to monitor the diurnal fluctuation in temperature in and beneath the pools. A heat transport model will be calibrated to these data to further assess vertical groundwater flow and test the utility of this method in these settings. Surveying of basin morphology using an autolevel is ongoing and the watershed extent of the pools is being identified using GIS software and DEM data layers. Cameras using time-lapse photography will be set up to monitor snow thickness and snow melting, and other hydrologic processes.

Results from this project will provide a better understanding of the recharge and discharge functions of vernal pools, importance of groundwater to the water budget, and hydrologic processes associated with vernal pools in Maine. This data will provide missing hydrologic information on New England vernal pools. The hydrologic interconnection between these vernal pools and the surrounding watershed is an important facet of the regulations that protect vernal pools and their surrounding landscapes.