Fig. 9. Schematic diagrams showing the different hydrological contributions to stream flow (weathered schist ground water, shallow ground water, and sources) and their effects on nitrate and sulfate levels in the stream water at each season. The dotted line represents water table elevation. The variable relative contributions of weathered schist and shallow ground waters to the stream flow are symbolized by variable thicknesses of black arrows. The size of NO₃^– and SO₄^2– symbols varies with nitrate and sulfate levels in the stream water at each season.