Nitrates in Groundwater Management Zones Continue Upward Trend

Nitrates in Groundwater Management Zones Continue Upward Trend

Wednesday, November 2, 2022
Summer sampling of monitoring wells across the district show that groundwater nitrate levels continued to increase in some parts of the district over the past year. While no zone has moved into a new phase of management this year, Zone 4 is close to moving into Phase II management and Zone 1 is approaching the threshold to move to Phase III management. 

Each of the three zones currently in the Phase III management area saw an increase in median nitrate values in the past year. Other zones of the district saw no change or some decline. 

The Upper Big Blue NRD has been monitoring groundwater quality since 1997 through a network of irrigation, municipal, dedicated monitoring, and domestic wells the district refers to as GWMA#2 (Groundwater Management Area #2). The GWMA#2 is comprised of 12 management zones delineated based on aquifer properties, land use, and geologic formation. The median nitrate value for each zone determines the phase of management and therefore, rules and regulations. According to the NRD’s Rule 5, a zone will move into Phase II management at 7 milligrams of nitrogen per liter (mg/L) in median samples and into Phase III at 10 milligrams per liter. Fertilizer management practices requirements increase with each Phase.