Water-Quality Assessment of the Heart River Basin, North Dakota, 1970-2019

Author: Wyatt Tatge, Department of Geology and Geological Engineering

Mentor: Dr. Larry Stetler, Department of Geology and Geological Engineering

Trends in water-quality for the Heart River Basin in west-central North Dakota were computed for historical (1974-2019) and recent (1999-2019) periods at 5 sites to determine changes that have occurred over time. Geochemical modeling was completed at these sites to determine the source of identified chemistry changes in the water. R-QWTREND was used to characterize dissolved ion concentration trends by removing the variability caused by changing streamflow conditions to determine changes from factors other than streamflow. PHREEQC inverse modeling was used to better understand the geochemical reactions controlling water-quality within the Basin. Results of the trend analysis indicated that sulfate, sodium, calcium, potassium, magnesium, chloride, and total dissolved solids had increasing trends in either the historical or recent trend periods. Results of the geochemical modeling indicated that increased dissolved ion concentrations were derived mainly from sulfate evaporites that include gypsum, konyaite, mirabilite, and thenardite that are components in the soils and geology of the Basin. Application of these results will assist producers and water-resource managers in making informed decisions regarding best management practices to protect soil health in terms of salinity and the quality of source water for irrigation.