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 HCO 3 were very closely related to discharge in log‐log regressions ( r 2 > 90 percent). Na and Cl required inclusion of seasonal functions for best prediction ( r 2 = 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 HCO 3 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.