Long-term hydrochemical sensitivity of an alpine watershed using the alpine hydrochemical model

Abstract

Eighteen 50-year simulations of the hydrology and chemistry of Emerald Lake watershed were conducted to evaluate the sensitivity of basin hydrochemistry to natural variability and changes in ion loading. These simulations were conducted using the Alpine Hydrochemical Model, designed to predict hydrologic and hydrochemical behavior based on inputs of water, chemical content and energy. A historical reconstruction of outflow hydrology indicates several strings of years with higher than average outflow as well as several drought year series. The results of hydrochemical modeling indicate a historically strong tendency for the basin to quickly rebound from these year-sequences, with exchange site chemistry playing a significant role in the carry-over basin chemistry interannually. Although the hydrochemistry is influenced by these precipitation trends over the short term, it is relatively insensitive to changes in acid loading. A sensitivity analysis validated the original estimates of bulk mineral weathering rates used by earlier researchers.