TITLE:
Description and Evaluation of Legacy Hydrochemical Data for the Big and Little Blue River Watersheds, Nebraska, USA
AUTHORS:
Jon Atkinson
KEYWORDS:
Hydrochemical Facies, Linear Regression Analysis, Stiff Diagram, Visual MINTEQ, Silicate (Feldspar) Weathering
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.9,
September
11,
2026
ABSTRACT: Numerous legacy hydrochemistry data [major cations and anions, pH, total dissolved solids (TDS)] (STORET database, 1968-1975) resulting from collection and analysis by the Nebraska Department of Environment and Energy (NDEE) were statistically, graphically, and hydrogeochemically analyzed for the Big and Little Blue River watersheds in southcentral Nebraska. Interpretation of this large legacy dataset (29 Big and Little Blue River watersheds sampling stations and 13 sampling sites on seven tributaries) revealed low but notably variable TDS concentrations (~100 - 500 mg/L), possessing predominant Ca-HCO3 hydrochemical facies. Median TDS values range from about 150 - 440 mg/L; slight calcite and dolomite supersaturation exists; and low computer software-generated saturation index values comprise a line of evidence for the near thermodynamic equilibrium of the studied surface waters. Many calculated saturation indices for calcite and dolomite were slightly positive, indicating slightly precipitating conditions. Subjecting Ca-HCO3 hydrochemical facies sample analyses to Pearson correlation and linear regression evaluation reveals strong covariance for Ca-HCO3 and Ca-SO4 pairs and somewhat less strong for Ca-Cl. These statistical analyses suggest primary carbonate weathering [assuming insignificant contribution of HCO3 originating from silicate (feldspar) weathering], followed closely by gypsum dissolution and less closely by evaporite dissolution in the studied river watersheds.