Investigating a high resolution, stream chloride time series from the Biscuit Brook catchment, Catskills, NY

In conjunction with stream discharge, stream chloride (Cl−) concentration has traditionally offered hydrologists a means to better understand internal catchment processes. Here we examine a 10 year, weekly stream Cl− concentration time series from the Biscuit Brook catchment, NY, United States. Using a two reservoir box model plus a snowmelt component, we replicate daily stream discharge reasonably well (Nash-Sutcliffe efficiency = 0.64) and capture general trends in the stream Cl− concentration (R2 = 0.36 during nonfreezing conditions). Additionally, we find that both the observed and modeled stream Cl− concentration time series appear to be 1/f noise when analyzed spectrally. Differing from previously published explanations of 1/f noise in other catchments, we propose that 1/f noise in the Cl− concentration signal of Biscuit Brook may originate from a suite of watershed-scale processes affecting both water content and Cl− mass in the system and occurring at multiple time scales.