Time and frequency domain analyses of high-frequency hydrologic and chloride data in an east Tennessee watershed

In the realm of sustainability science, it is becoming increasingly important to understand the basal condition of a natural system as well as its long-term behavior. Research is needed to better explain the temporal scaling of water chemistry in streams and watersheds and its relationship with the hydrologic factors that influence its behavior. Persistence of dissolved chemicals in streams has been demonstrated to be linked to certain hydrologic processes, such as interaction between hydrologic units and storage in surface or sub-surface systems. In this study, spectral and wavelet analyses provided a novel theoretical basis for insights into long-term chloride behavior in an east Tennessee watershed. Temporal scaling analyses were conducted on weekly time series data of chloride collected from November 1995 to December 2005 at the West Fork of Walker Branch in Oak Ridge, Tennessee. The objectives of the study were to: evaluate chloride concentration (a conservative solute) to determine the presence of statistical persistence and the relationship of the persistence to hydrologic variables (discharge and rainfall) using time and frequency domain analyses of high-frequency hydrologic and chloride concentration data. Results demonstrated that chloride showed some level of statistical persistence that was influenced by rainfall and/or discharge. Short-term statistical persistence (less than a year) was related to the persistence of rainfall and discharge, whereas long-term statistical persistence (more than a year) was related to the persistence of discharge.