MANHATTAN, Kan. -- Drought conditions have prevailed in parts of the nation's midsection through much of the past several years, and that fact may have affected the quality of the region's well water, a Kansas State University agricultural engineer said.

"Well water comes from the pores in underground aquifers -- deposits of soil, sand, rock, and such -- so is in contact with many minerals," said Morgan Powell, K-State Research and Extension. "Some minerals, such as calcium sulfate, readily dissolve in the water. Others don't.



"Water sometimes acts as a barrier, however, that prevents some minerals from undergoing certain chemical changes that alter their ability to dissolve in water. So, as long as the water is present in the ground and fills the pore spaces around the minerals, they resist chemical alteration and stay safely in place -- and out of tap water."

But, when the water level drops, as in times of drought, minerals become exposed to dry conditions, Powell explained. And, with their protective water barrier removed, some of the minerals may undergo the chemical changes that make them more soluble.

After that, when the drought ends and the water table returns to its former level, the chemically-altered minerals can dissolve in the water. In turn, they're carried out of the ground and into the household.



Increased concentrations of dissolved minerals also can relate to reduced recharge rates, he said.

When the soil is quite wet or saturated by rain, the excess moisture in the soil profile recharges the groundwater supply.

"It takes several rains in succession or a large rain that lasts over multiple days to raise soil moisture to the point that there is excess water is the soil that can move downward to groundwater and recharge it," Powell said.

That kind of recharge, however, is important to more than just water supply, he said.

Over time, minerals that dissolve readily from water-bearing materials cause an increase in mineral concentrations. The longer water remains in contact with such materials, the more concentrated the contaminant dissolved minerals become.

So, the introduction of fresh water not only recharges the aquifer, it also dilutes concentrations of contaminants, because the fresh water has not been exposed to minerals for long.

"Water well users should be alert to changes in their water at any time, but during drought it can be unusually important," Powell said.



"Because many contaminants are not detectible by appearance, taste, or odor, testing is the only way to determine water's safety, he said.

"All analyses should be retained for future reference. Comparison with previous results reveals trends and allows for intervention before problems become more obvious."

Based on test results, for example, a well owner may see the need to take action to protect the well and groundwater, to to install a treatment device, or to obtain seek an alternate new water supply.

More information on well water quality is at county and district K-State Research and Extension offices in the publications "Measuring Depth to Water in Wells," "Testing to Help Ensure Safe Drinking Water" and "Recommended Water Tests for Private Wells." The publications also are available on the Kansas Extension Web site at www.oznet.ksu.edu (click on "Publications" and search for MF2669, MF-951 or MF-871).



SOURCE: K-State Research and Extension news release.