OMAHA -- The benefits of a series of wet years, including the extraordinary rains of 2019, are showing up in Nebraska’s aquifers.
Across Nebraska, almost 80% of wells recorded an increase in groundwater levels from spring 2019 to spring 2020, according to the annual groundwater report by the Conservation Survey Division of the University of Nebraska-Lincoln’s School of Natural Resources.
That’s good news because Nebraska’s economy rests heavily on the health of its aquifers given their importance to irrigation, industry and domestic and municipal drinking water.
Some highlights from the report:
From spring 2019 to spring 2020, the state averaged a 1.58-foot increase in groundwater levels. Aaron Young, a geologist at UNL and lead author of the report, said that level of statewide increase was “pretty significant.â€
The highest increases were recorded in central Nebraska, where some levels jumped more than 14 feet.
Aquifers continue to recover from the stress of the flash drought of 2012, the state’s hottest, driest year on record. Of the 4,533 wells measured every year from spring 2015 to spring 2020, the groundwater levels averaged a 3.59-feet increase.
Groundwater levels have dropped and risen over time, in response to dry and wet years. Above-normal precipitation from 2007 until early 2012 helped aquifers recover from the prolonged drought of 2000 to 2007. The flash drought of spring 2012 to spring 2013 saw an unprecedented drop — an average of 2.54 feet — in groundwater in the state. (Some parts of Nebraska saw a drop of almost 25 feet.) That drought erased nearly all of the previous years’ gains.
And now, a series of wet years is providing a recovery in some areas. While not all of Nebraska’s aquifers have recovered from 2012, some have, Young said.
The Kilgore weather station in Cherry County recorded 212% of normal precipitation in 2019, well above the highest level of annual precipitation — 180% of normal — recorded in any one spot since 2007 when the state began enjoying a string of wet years.
Depletion continues in aquifers that are deep and have little connection to surface water. The steepest decline in this type of aquifer is the 125-foot drop just north of Alliance in Box Butte County. Other areas with sharp drops are in southwest Nebraska and in the Panhandle.
Wells near reservoirs and canals continue to show increases as they benefit from seepage. Groundwater levels have risen as much as 60 feet near Lake McConaughy because of seepage from the lake, where water has been stored since 1941. The aquifer in that area has generally stabilized, though it fluctuates with lake levels and precipitation. In south-central, central and western Nebraska, groundwater has risen by more than 100 feet because of the influence of canals, reservoirs and irrigation.
Groundwater-level monitoring began in Nebraska in 1930. This type of report by UNL has been produced since the 1950s.
Young said it’s too early to know how the 2020 drought affected groundwater levels. Officials have just begun taking the spring 2021 measurements that would show some of the effects of the past year.
He said it’s also too soon to understand whether climate change is affecting the state’s aquifers.
“Climate change will definitely have an impact on aquifers,†Young said. While aquifers are rising and falling with wet and dry cycles and because of heavy irrigation, climactic shifts take longer to discern, he said. The likely impact of climate change, however, will be greater depletion — in spite of potential increases in precipitation.
Martha Shulski, Nebraska state climatologist, said annual precipitation already has increased in the state and is likely to continue doing so. Most notable are the changes in central and northeast Nebraska, she said. That area is recording more wet days and more of those days are incurring a greater amount of precipitation.
Climate scientists have long said that increased precipitation won’t be the cure-all to the stresses of a warmer world on plant life.
For one thing, plants have a limited ability to absorb moisture, and increased heat is expected to outstrip that.
And then there are limitations in recharging moisture levels in soils and aquifers. Young said soils can’t absorb water fast enough to keep up with heavy precipitation events. Typically, the top few inches of soil become saturated quickly, and then the rest of the rain runs off rather than percolates down in the aquifer.