Fig. 5. Mixing modeling of water in the Karup River system.

Three-component mixing of the inverse Sr concentration and ⁸⁷Sr/⁸⁶Sr ratios of water from the Karup River system (samples marked with yellow dots in Fig. 3). Hydrochemical end-member values for Kompedal surface water and groundwater are weighted averages of analyses, with the shaded area representing the 2σ uncertainty. The end-member value for agricultural runoff is calculated on the basis of the amounts of lime, manure, and fertilizer applied to the fields by local farmers (see the Supplementary Materials) and average runoff and rainfall values, and the shaded area around the points represents the estimated uncertainty in the values. The numbers at each data point indicate the distance in kilometer from the headwaters of Vallerbæk stream.