Groundwater level declines significantly, yet remains above allocation trigger
By Jacob Mitchell, Water Resources Technician
During March and April 2023, staff of the Upper Big Blue Natural Resources District measured roughly 500 observation wells throughout the district to determine an average water level change, based on a weighted change from each well. For spring 2023 water level measurements, the NRD has determined that the average groundwater level change shows a decline of 2.21 feet from last spring.
The spring 2023 average groundwater level is now 6.68 feet above the “Allocation Trigger.” Thus, there will be no allocation restrictions for the 2024 irrigation season.
Observation wells are measured in the spring of each year, allowing the water table to rebound from the previous irrigation season. The wells that are measured are uniformly distributed throughout the district to provide an accurate profile of the average groundwater level change. Each well measured is assigned an area of the district based on distances from other wells. This method gives the average groundwater level change a weighted average.
In spring 2022, the NRD reported an average decrease of 0.24 feet. Spring 2021 showed an increase of 0.35 feet on average. Fluctuations from year to year are common throughout the district. The Upper Big Blue NRD sits above the High Plains Aquifer, which stretches from South Dakota to Texas. This portion of the aquifer is dynamic and different factors like rainfall and pumping affect how the aquifer reacts.
In addition to the average change across the district, the NRD has also provided a more detailed look at water levels across the district. Water levels declined most significantly in Butler County and Clay County, each with a drop of more than 4 feet. Adams County saw the smallest decline, only dropping 0.64 feet. The rest of the district including York, Seward, Hamilton, Polk, and Fillmore Counties all saw a decrease between 1 and 2 feet.
Water use records enable informed management decisions and practices
In recent years, producers have done an exceptional job of managing use of district water resources and cooperating with the NRD on conservation activities and monitoring. Along with NRD staff measuring observation wells, all groundwater users are required to annually report their water use. This is how the NRD maintains records on historic groundwater usage. Groundwater use records are very important to the district for making informed management decisions. The 2022 district average groundwater usage was 7.53 inches/acre. The district average groundwater usage is 5.97 inches/year since 2007.
The district’s goal is to hold the average groundwater level at or above the 1978 level. In 2005, the district average groundwater level reached the “Reporting Trigger”, initiating mandatory reporting of annual groundwater use to the district and certification of irrigated acres. If the district average water level falls below the 1978 level (“Allocation Trigger”), groundwater allocation will begin.