Ground water withdrawals can affect both ground water and surface water flow. Extensive withdrawals can lead to wells, springs and wetlands to go dry, lake levels to drop, stream flow to reduce resulting great harm to ecosytems. The reduction in surface water can in turn can lead to greater contamination of ground water, losing the ability to filter pollutants from water before it flows in to recharge an aquifer.

Intensive ground water withdrawal can also cause subsidence - lowering of the land surface. Subsidence occurs when the removal of water leaves underground spaces that collapse or when underlying clay shrinks from lack of moisture. The result looks like a cone of depression on the land.

Ground water is an important water source in the ACF River Basin. In the lower part of the basin, aquifers are highly productive. In 2000, rround water provided 37% of all non-thermoelectric water withdrawals in the basin. Most of these withdrawals were for agricultural use in the lower part of the basin as shown in USGS factsheet, 2007 [1].

According to the above article, some ground water modeling studies (1999) conducted to investigate the effect of pumping on streamflow in the lower ACF basin indicated that irrigation pumping reduced the ground water flowing into streams by 56 million gallons per day (during low flow conditions).

It is also mentioned that above information is not available throughout the basin, eventhough it is essential to have quantified ground water modeling results for the northern parts of the basin. The reason for difficult to quantify is indicated as reporting requirements not being  implemented for agricultural withdrawals.

Use of ground water resources has long-term impacts beyond the point of withdrawal that future management

must consider to minimize impacts on surface water resources [2].

[1] fs2007-3034, USGS Fact sheet.pdf

[2] http://files.dnr.state.mn.us/waters/groundwater_section/sustainability/GW-SWinteraction.pdf