Kansas Geological Survey, Public Information Circular (PIC) 1
A User's Guide to Well-spacing Requirements for the Dakota Aquifer in Kansas--Part 5 of 5

Effect of Pumping Multiple Wells on the Dakota Aquifer

If multiple wells in the Dakota aquifer are withdrawing water from the same sandstone body, their cones of depression will probably overlap and coalesce (figure 6). This is because of the relatively small size of the sandstone bodies. If multiple wells operate simultaneously for some time, the aquifer may not be able to adequately replace the withdrawn water with recharge, resulting in water-level declines.

Figure 6--When two nearby wells are pumping, they create a cone of depression, which overlaps. Note the flow moving in both directions between the pumping wells.

Rationale for Well-spacing Requirements

The water resources of Kansas are managed by the Division of Water Resources using the concept of safe yield. Safe yield is the long-term sustainable yield of the source of supply including hydraulically connected surface water and ground water. Thus, the total amount of water pumped from an aquifer should be less than the net recharge so as not to deplete the aquifer. The purpose of well-spacing requirements is to ensure that additional wells using the Dakota aquifer as a source of supply do not impair the supply of water to existing wells.

Impairment can also result from over-development of the entire aquifer. The Dakota aquifer is susceptible to over-development unless the spacing between wells is adequate to avoid overlap in their respective cones of depression. If wells are too close together, they may cause permanent water-level declines and eventual depletion of the aquifer. This is most likely where the Dakota aquifer is overlain by thick, relatively impervious strata. Results from the Dakota Aquifer Program show that there is no significant local freshwater recharge to this part of the aquifer. Consequently, water must come from other parts of the aquifer not affected by pumping. This represents a net loss of water from the aquifer and may cause water-level declines. In areas where the Dakota aquifer is at the surface or is overlain by shallow aquifers, local recharge to the Dakota aquifer from precipitation or from the overlying aquifer is sufficient to justify a denser well spacing.

A denser well spacing for domestic wells is appropriate because they typically operate at low pumping rates and for relatively short periods of time, causing less impact on the aquifer than nondomestic wells pumping at higher rates and for longer periods of time.

Kansas Geological Survey, Geology Extension

Web version Nov. 1995
http://www.kgs.ku.edu/Publications/pic1/pic1_5.html