ANTHROPOGENIC INFLUENCE ON THE WATER CHEMISTRY OF THE UPPER WOOD RIVER BASIN, RHODE ISLAND, USA

In a watershed with relatively good quality water, what role does land use play in the variations of water chemistry? This study looks at the chemical contributions to the Wood River in southwestern Rhode Island from its headwaters over a three-month period. Parris Brook, Fall River, Flat River, Acid Factory Brook, Breakheart Brook, and Roaring Brook flow south through the Arcadia Management Area (AMA), where they converge to form the Wood River. The first five tributaries begin their journey in the relatively unpopulated area north of the AMA, while the sixth flows from the more densely populated eastern border of the AMA. Field data and water samples were collected from 22 surface-water sites. Based on the analyses of samples with electrical conductance (EC) < 75mS, the background levels of fluoride, chloride, nitrate (as NO₃^-), and sulfate in the watershed are 0.12 - 0.22 mg/L, 4.0 - 8.0 mg/L, 0.28 - 0.78 mg/L, and 3.3 - 5.5 mg/L, respectively. Acid Factory Brook, Flat River, and Fall River had ECs consistently below 60 mS over the study period, while Parris Brook EC ranged between 62 - 84 mS. Breakheart Brook had the highest variation of EC at 50 - 137 mS. However, the highest overall ECs were found in the Roaring Brook drainage with EC ranging from 152 mS to 350 mS; this reflects significant changes in chloride concentration, which reached levels as high as 64 mg/L, more than eight times the background concentration. The maximum nitrate and sulfate concentrations in Roaring Brook were approximately twice the respective background values. Chemical analyses are ongoing to characterize these waters, including an investigation into the use of optical brighteners as a possible tool for detecting septic system constituents.