Controls of concentration and loadings of major ions in a stream draining intermediate igneous rocks

Some 300 measurements under a wide range of flow conditions were used to construct regression models to predict concentrations of six major ions in a moorland stream draining intermediate-basic lavas in Scotland. Ca, Mg, and HCO₃ were very closely related to discharge in log-log regressions (r² > 90 percent). Na and Cl required inclusion of seasonal functions for best prediction (r₂ = 76 per cent in both cases). K concentrations were predicted from discharge, direction of stage change, and a seasonal function. Annual losses of Ca, Mg, and HCO₃ were 252, 36, and 871 kg ha ^?1, substantially larger than those for upland catchments on acid rocks. Losses of K, Na, and Cl were of a similar order to other upland sites.