Characteristics of chloride loading from urban and agricultural watersheds during storm and non-storm periods

Abstract

The chloride ion (Cl-) can adversely affect an aquatic ecosystem, but it is not clear how Cl- moves with runoff and how its transport processes are related to land uses and land cover. This study investigated how the loading characteristics of Cl- vary depending on storm events and land cover in a temperate region. We monitored Cl- concentrations in three study watersheds that have different compositions of urban and agricultural land uses. In addition, a Mass First Flush ratio (MFFn) was determined to quantify the effect of first flush on Cl- loading. Overall, the observed concentrations and loadings in this study were found to be less than those reported in cold northern regions. The monitoring data showed that Cl- concentrations and loads observed in an urban watershed were significantly larger than those of a rural watershed. The results suggest water management plans should focus on urbanized areas and their storm water to efficiently reduce chloride loading to downstream waterbodies. However, a further study is recommended to identify the sources and pathways of Cl- loaded to waterbodies.