How does groundwater affect my lake?

Hard surfaces such as streets prevent water from soaking into the ground.

As watersheds are developed, the amount area of area covered by hard surfaces (roads, driveways, rooftops, etc.) increases, and prevents water from soaking into the ground and recharging groundwater aquifers.

Groundwater’s role in lakes

There are four main lake types. Groundwater plays a major role in seepage and groundwater drainage lakes. It can also affect drainage lakes and impoundments, even though groundwater flow is secondary in those lakes.

Groundwater flow is one of several sources of water for lakes (termed inflow); others include precipitation, runoff, and in some cases streams and rivers. Groundwater flow can also remove water from a lake (termed outflow). Other sources of outflow include evaporation, or in some cases streams and rivers.

A lake's "water budget" is the balance between the amount of water coming into the lake (inflow) and the amount of water leaving the lake (outflow). As long as inflows and outflows remain equal the balance remains constant; if inflows and outflows differ, the balance fluctuates. If reduced inflows come with a corresponding reduction in outflows, then the rate of water flow through a lake can decrease, even as the volume (or level) in the lake remains constant. A change in the rate of flow through a lake, especially over the long term, can also lead to adverse lake impacts.

A reduction in the volume of water flowing in as groundwater —due to groundwater pumping, for example—can reduce the total volume of a lake, or at least reduce the flow through a lake, both of which can have detrimental impacts on a lake ecosystem, water quality, and recreational uses.

Development’s impact on groundwater/lakes

As watersheds are developed, the amount area of area covered by impervious surfaces (roads, driveways, rooftops, etc.) increases. This prevents precipitation from infiltrating into the ground and recharging groundwater aquifers. Having less water in aquifers can lessen the flow of groundwater into lakes and other surface waters.

Significantly more Wisconsin lakes are threatened by development impacts on their water budgets than by potential impacts from nearby groundwater pumping. Increasing levels of development and redevelopment in southern and northern Wisconsin threaten to produce problematic outcomes for lakes if we do not address impervious surface areas and their impact on groundwater as it relates to lakes, not to mention the polluted runoff that can flow from impervious areas lacking proper stormwater controls.