VALENTINE, Neb. — Nitrate levels in well water across north-central Nebraska have slowly increased over the past three decades, according to new data from the Middle Niobrara Natural Resources District.

Based on samples collected in 2025, 47% of domestic wells, 75% of irrigation wells and 70% of monitoring wells in the district show increasing nitrate levels over time. District officials emphasized that the increases have been gradual. Since 1996, nitrate levels have risen an average of 1.27 parts per million in domestic wells, 1.8 ppm in irrigation wells and 3.57 ppm in monitoring wells.

The U.S. Environmental Protection Agency sets a legal limit of 10 ppm of nitrate in drinking water, which is considered the maximum safe level.

In Brown County, 13% of domestic wells, 19% of irrigation wells and 50% of monitoring wells tested above that threshold. In Cherry County, 3% of domestic wells, 6% of irrigation wells and 26% of monitoring wells exceeded 10 ppm. In Keya Paha County, the figures were 22% of domestic wells, 31% of irrigation wells and 13% of monitoring wells. In Rock County, nitrates were above 10 ppm in 15% of domestic wells, 24% of irrigation wells and 57% of monitoring wells.

Nearly 400 wells were sampled across the Middle Niobrara NRD this year. Results are displayed using a color scale, with green indicating less than 5 ppm, yellow between 5 and 7.5 ppm, and red above 7.5 ppm.

MNNRD well samples
MNNRD well samples  

 

And here’s a look at the well samples collected by NRDs across Nebraska.

Nitrate water samples
Nitrate water samples  

 

To better understand what is driving higher nitrate levels, the district conducted isotope testing in 2023 on 40 wells across four counties that tested above 10 ppm. Of those samples, 28 were linked to synthetic nitrogen fertilizer, seven were tied to organic sources such as human or animal waste or runoff, and five showed a combination of synthetic and organic sources.

“Nitrate contamination can come from numerous different sources,” said Kyle Temple with the Middle Niobrara NRD. “Synthetic nitrogen used for growing crops or livestock feed, manure from animal waste (both confined and open range), human waste from leaking septic systems or open drain fields, household fertilizers for lawns and gardens, industrial runoff, and some naturally occurring sources can all cause nitrate levels to rise.”

Temple said nitrates are highly water-soluble, making overuse or improper application of nitrogen fertilizers a common contributor. He also pointed to well construction and location as factors.

“There are old Sandpoint wells or household wells still in use that were constructed prior to the establishment of water well construction standards in 1988 that were implemented to reduce the likihood of well contamination and improve aquifer protection,” Temple said. “Old domestic wells are often located near old livestock barns, in the middle of a heavily fertilized yard or garden, or near a septic leech field.”

The Middle Niobrara NRD covers roughly 3 million acres from Gordon to Bassett. The district samples the same domestic, irrigation and monitoring wells year after year to track long-term trends.

Domestic wells are sampled on a voluntary basis, with landowners receiving annual reports on nitrate levels. Irrigation wells include both voluntary sites and required monitoring locations. Since 2011, the district has required all newly drilled irrigation wells to be monitored annually for nitrate levels. The district also maintains 75 monitoring and observation wells placed in areas where groundwater quality or quantity concerns exist.

“It is important to get your water tested every year or every couple of years, especially if you have a well that is older or constructed prior to 1988 or that might be in a location that is more vulnerable to contamination,” Temple said.

The district offers free nitrate testing for private well owners at its office, with results available in less than an hour. The district also works with Wards Lab in Kearney to do full panels of testing for other issues in domestic, livestock, and irrigation wells for a small fee. City water systems are required by the state to test their water regularly.

“Go learn about your well that supplies your water,” Temple said. “Where is it located? When was it drilled? Does runoff water pool around it and soak in? Do you spray weeds and fertilize around it? Does it meet Water Well Construction Standards (Ne State Statutes Title 178 Chapter 10-13)? What is your depth to groundwater? How is the land around your well used?”