Wastewater contains elevated concentrations of fecal indicator bacteria (FIB). The type of wastewater treatment technology and septic system density may influence the FIB concentration and exports at the watershed scale. The goal of this study was to gain a better understanding of FIB concentrations and exports from watersheds served by conventional septic (CS) systems, sand filter (SF) septic systems, and a municipal sewer (SEW) system. Seven watersheds (3 CS, 3 SF, and 1 SEW) were monitored to quantify FIB concentration and export monthly from April 2015 to March 2016. The type of wastewater treatment did not yield significant differences in FIB concentration or exports when pooling watersheds using similar wastewater treatment. Watersheds with the highest septic densities (approximately 0.4 systems ha⁻¹) contained greater FIB concentrations and exports than watersheds with the lowest (approximately 0.1–0.2 systems ha⁻¹), but only FIB concentrations significantly differed. These findings suggest that when the septic system density exceeds 0.4 systems ha⁻¹, water quality degradation from septic leachate may be observable at the watershed scale, especially in watersheds dominated by residential development. More research is recommended to determine if this density threshold is similar for other water pollutants and/or in watersheds with differing hydrogeological, land use, and wastewater characteristics.

Hurricane Matthew caused flooding in Eastern North Carolina that was categorized as a one in 500-year frequency event. Matthew was the second such event in less than 20 years, following Hurricane Floyd in 1999. The frequency of intense storms is projected to increase for many coastal areas, including North Carolina, because of climate change. The goal of this study was to gain a better insight into the geochemistry of flood waters associated with major flood events. Water samples (n = 22) from the Tar River in Greenville, North Carolina were collected over a two-week period after Matthew moved across the state. Results show that total Kjeldahl nitrogen, dissolved organic carbon, phosphate, and Escherichia coli concentrations and exports were significantly (p < 0.05) higher when the river was above flood stage relative to below. Isotopic analyses of δ¹⁵N and δ¹⁸O in NO₃ in flood waters suggest that wastewater, possibly from sanitary sewer and confined animal feeding operation overflows, was the major source of nitrate associated with flood waters. Regulatory efforts to reduce nutrient loading to coastal waters may be complicated by contributions associated with intense storm events, given that such storms are becoming more frequent.

Recent legal cases have suggested that contaminated seeps and/or springs that have measurable impacts on adjacent surface water quality may fall under the jurisdiction of the Clean Water Act (CWA). An improved understanding of the effects of groundwater seeps on surface water quality is needed to support the evolving legal and regulatory environment. Surface seeps or seepage zones are locations where upwelling groundwater saturates the surface. Seeps can provide groundwater that may be transported to nearby surface waters along surface and shallow subsurface flowpaths. From a water quality perspective, seeps can provide portholes to observe groundwater quality. Here we consider examples of seeps as contaminant sources or sinks across a range of watershed disturbance and synthesize the seep water quality literature to help answer the questions: Why do seeps act as contaminant sinks in some cases and contaminant sources in others? What areas of seep water quality research can help apprise the legal and policy discussion on the role of the CWA to address groundwater contamination that is conveyed to streams? Overall, the case studies and literature review indicated that seep water quality data can provide valuable insights into the effects of stream‐groundwater interactions on stream water quality. Future work on seep‐surface water interactions is needed to characterize seep water quality behavior across a range of hydrogeological, meteorological, and land‐use conditions to better understand the locations where seeps are more likely to convey contaminants to streams and affect stream water quality.