Multimedia Reporting (Kuhr-Musser)

Three hundred meters, about the length of three football fields, is a long way down. That is how far the well extends down which two scientists used to see if they could detect changes in the aquifer water levels due to, in this case, rain.

Dr. Marios Sophocleous, a senior scientist specializing in geohydrology at the Kansas Geological Survey, and his colleague Dr. Earl Bardsley, an associate professor at the University of Waikato in New Zealand, have found they can clearly detect, almost a thousand feet down, events such as rainfall on the surface, in the water level of an aquifer.

This well was used by the scientists in their experiment (Photo Courtesy of Kansas Geological Survey)

Aquifers are underground rock formations which hold water like a sponge. In Kansas, much of the water for irrigation comes from the Ogallala aquifer, which extends under eight states. As a result, the aquifer is being depleted faster than nature can refill it, Sophocleous said. Measuring the water levels in aquifers is important because the measurements give scientists an idea of the amount of water being used, Sophocleous said.

This photo shows the extent of the Ogallala aquifer (Photo Courtesy of Kansas Geological Survey)

Currently, scientists must go to thousands of wells across the state to get measurements on the amount of water coming in and out of the Ogallala aquifer. This creates a greater margin for error because a large amount of data must be analyzed from the various wells and then put into an overall reading, Sophocleous said.

Sophocleous and Bardsley have found an easier method of measuring the amount of water in a confined aquifer. They used a confined aquifer below the Ogallala aquifer because the confined aquifer is more responsive to changes in pressure. A confined aquifer is surrounded by layers or impermeable rock or clay which restricts the amount of water which come in and out of it.

In the study, the confined aquifer is called a natural geological weighing lysimeter.

A lysimeter is a device which is used to measure how much water is evaporating from the soil. It is like a scale; only in this instance the water is on the scale instead of a solid substance, Sophocleous said.

The geological weighing lysimeter, in this case the well, “weighs” the changes in total water over a given area, Bardsley said. The deeper the well, the larger the area becomes that is weighed, Bardsley said. This method would not only simplify the process of monitoring the aquifer levels, but it would also lead to less error on the part of scientists.

The purpose of their experiment was to see if a load on the surface, such as rain, could be sensed accurately 300 meters down in the well. The well, located in Trego County, is about 260 miles away from Lawrence.

Just as satellites are remote sensors that circle the earth and record data, the method used by Sophocleous and Bardsley uses the same general idea. The only catch is that the remote sensing occurs underground instead of in outer space, Sophocleous said.

Although other scientists have drilled deeper, the significance of the findings of Sophocleous and Bardsley was that they found that at 300 meters the instruments in the well clearly detected or “weighed” the amount of rainfall measured on the surface.

(Source Marios Sophocleous) This graph shows the rise in the water level of the Dakota Aquifer when it rains. The sensors, about 984 feet underground, detect a rise in the water level almost immediately.

The only unknown in this experiment is exactly how deep they can drill and still receive a clear reading of the amount of rain falling on the surface, Sophocleous said. Drilling costs hundreds of thousands of dollars however, which requires funding said Sophocleous. Also, depending on how deep the holes are, and how many holes are drilled, the costs increase, Dr. Sophocleous said.

Besides cost, being a factor, location is also a factor.

“The technique can only be applied in some places where the hydrogeology
is right,” Bardsley said.

When it can be implemented, this method would allow scientists to more accurately monitor the changes in the water levels of aquifers such as the Ogallala Sophocleous said. Scientists would not only know the amount of water coming in and out of the aquifer, but when water conservation needed to be implemented.

This picture shows the decline of streams in Kansas in 1961 and 1994 due to the depletion of the Ogallala (Source Kansas Geological Survey)

“We want to see how to best manage water resources,” Sophocleous said.

This method also may allow scientists to monitor ecosystems that were previously hard to monitor said Bardsley. An example would be the tropical rainforest or the desert, he said.

Better monitoring of these ecosystems could lead to more responsive climate models.

“This gives real-time measurement of changes in such environments which might be reflective of climate change effects,” Bardsley said.