Water level measurements to provide snapshot of aquifer

By Sean Ellis

Idaho Farm Bureau Federation

POCATELLO – Groundwater level measurements were recently collected from 1,300 private and public wells throughout the 1,100-square-mile eastern Snake River Plain in southern Idaho.

The data will help water managers understand the status of the Snake River plain aquifer as the state enters the 2018 irrigation season.

While the data hasn’t been analyzed yet, the measurements are expected to show an uptick in water levels in the eastern Snake River Plain aquifer, which provides irrigation water for 1 million acres of farmland as well as for the state’s aquaculture industry, and is the primary source of drinking water in the region.

The measurements will likely show some water level rebound as a result of Idaho’s big water year in 2017, when snowpack levels reached record and near-record levels in many parts of the state, said Sean Vincent, hydrology section manager for the Idaho Department of Water Resources.

After collecting and analyzing the data, officials will estimate the change in the amount of water stored in the aquifer.

Because the aquifer is very deep, it’s not known exactly how much water is stored there, Vincent said. However, “you can compute how much storage change there has been based on the fluctuation of water levels.”

While the data isn’t finalized yet, “I’m pretty optimistic that we got some rebound,” he said.

But the overall trend in water levels in the aquifer since the 1950s has been downward, he added.

“We’ve had some ups and downs along the way, but the overall trend has been a downward decline in aquifer water levels since the mid-1950s,” Vincent said.

From about 1912 to 1950, the amount of water stored in the aquifer increased by about 18 million acre-feet, due in part to flood irrigation and leaky canals, which resulted in more incidental recharge into the aquifer.

But since 1950, the amount of water stored in the aquifer has decreased by about 12 million acre-feet, as many farmers have switched to sprinkler irrigation practices, flood irrigation has become less common in the region and groundwater pumping became more common.

This year’s likely rebound “is a good sign but it doesn’t mean our problem has been solved,” Vincent said. “It’s encouraging but it’s not indicative of anything significant yet.”

The groundwater level measurements were conducted in March and April by employees of the U.S. Geological Survey, IDWR and the U.S. Bureau of Reclamation.

Dave Evetts, assistant director for hydrologic data at the USGS’ Idaho Water Science Center, said the data should be entered into the state database and available to the public by late June or early July.

The agencies measure aquifer water levels every year but undertake mass measurement efforts, like the one conducted this year, every five years.

The data provides state and federal water managers a snapshot of the current state of the eastern Snake River plain aquifer, Evetts said.

The primary purpose of these collection efforts, he said, is to validate and improve the eastern Snake River plain aquifer model maintained and operated by the IDWR and to understand the status of the aquifer.