IDENTIFYING THE RELATIVE CONTRIBUTION OF GROUNDWATER AND PRECIPITATION TO WETLAND SYSTEMS IN LAPEER COUNTY MICHIGAN

Wetlands are complex ecosystems that are dependent on hydrologic processes and water chemistry. Understanding the role that water chemistry and nutrients play in wetland ecosystems is crucial to wetland management and restoration. The Fish Lake Environmental Education Center in Lapeer Michigan, whose topography north of the lake is glacially influenced, and contains a large bog. Between the bog and lake there are multiple kettles that contain ephemeral wetlands during the spring months. Bogs are primarily precipitation sourced, whereas the kettle wetlands may be a combination of precipitation and groundwater sourced. Previous studies indicated that the direction of groundwater flow is towards Fish Lake, but it was unclear to what extent groundwater is affecting the water chemistry in the wetlands north of the lake. The goal of this project was to understand the relative contribution of both precipitation and groundwater in the bog and kettle wetlands north of Fish Lake. Identifying the primary water source in these wetlands will aid in their restoration and management.

Monthly and bi-weekly sampling from shallow groundwater and surface water occurred between May 2022 and September 2023. Samples were collected using either a disposable bailer or peristaltic pump from monitoring wells ranging from eight to 21 feet (2.4 to 6.4 meters) below ground surface. Field data collection included pH, electrical conductivity, temperature, and water level. Laboratory water sample analysis included nitrate, nitrite, phosphorus, iron, sulfate, and turbidity. Nitrogen (nitrite & nitrate) and phosphorous concentrations were highest on average in the kettles. The bog and kettles all have an acidic pH, however the average pH values in the kettles are lower closer to the bog, and higher closer to the lake. These data suggest that the wetlands closest to the lake are more heavily groundwater influenced, and become more precipitation sourced towards the bog. This study supports other research at Fish Lake including a botany study of plant communities within these wetlands and creation of a digital field guide.