WATER IN THE CITY: THE GEOCHEMISTRY OF THE URBAN FOURCHE CREEK WATERSHED

Most of the creeks in the City of Little Rock, Arkansas (US) flow through the Fourche Creek Watershed into the Arkansas River. This system drains over 73% of the city, and the wetlands within it play a vital role in filtering the water, wildlife habitat, flood control, and recreation for the metropolitan area. Additionally, when the stage of the Arkansas River is higher than Fourche Creek it will flow into the creek system impacting the stream geochemistry. For several years, we sampled the tributaries in this watershed as well as the AR river for field parameters (YSI multi-probe), as well as dissolved cations (IC), anions (IC), and trace elements (ICPMS) in order to understand the natural changes in geochemistry through time, as well as changes due to anthropogenic activity. We sampled during low and high flow, as well as storm events. The Arkansas River has much higher concentrations of cations (Ca, Na, K), anions (Cl, SO₄) and trace elements (Ba, Li) compared to the tributaries within the city. Although, Mn and Zn were occasionally higher in Fourche Creek compared to the Arkansas River. The tributaries within the watershed have distinct geochemical patterns dependent on the land cover around them. The Coleman Creek tributary has the highest concentration of cations, anions, and trace elements of the streams sampled reflecting the more urban environment surrounding the stream. The geochemistry of the streams in this dynamic system was a function of the time of year, discharge, land cover, time in the wetlands, human activity, and flood events.