Influences of land use on water quality of a diverse New England watershed

Abstract

Analysis of variations in major ion chemistry in the Mill River watershed reveals the importance of anthropogenic activities in controlling streamwater chemistry. Average concentrations of NO3- and SO4(2-) show a positive correlation with percent catchment area altered by human land uses, and concentrations of Cl- increase with road density. Water removal from municipal reservoirs increases the downstream concentration of NO3- and SO4(2-) over that predicted by land use changes, showing that removal of high quality upstream water concentrates pollutants downstream. In salt-impacted streams, Cl- exceeds Na- by 10-15% due to cation exchange reactions that bind Na+ to soil. The net effect of nonpoint source pollution is to elevate ANC in the most developed areas, which impacts the natural acidity of a large swamp. The sum of base cations (C(B)) exceeds ANC for all samples. Plotting C(B) against ANC and subtracting Cl- quantifies the impact of road salt from the impact of the addition of strong acids.