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The Savage River in western Maryland and its associated reservoir and watershed serves many purposes including recreation, drinking water supply, and auxiliary water supply for Washington DC. Streamflow on the Savage River was modeled using a simple hydrologic model and validated with historical streamflow observations. Future projected climate data were used to drive the model to assess the impact of temperature and precipitation changes on future streamflow. Winter streamflow is projected to increase, while spring, summer, and fall streamflow are projected to decrease. Annual streamflow totals show a slight negative trend over the coming century. Future changes in precipitation are more influential on future streamflow during the winter while temperature may be more important during the summer and fall. On an annual basis, by the year 2098, the impacts of temperature and precipitation will essentially cancel each other out resulting in only a small negative trend in annual streamflow. Increased streamflow during the winter months may not be able to compensate for decreased flow during the remainder of the year which raises concerns about the ability of the reservoir to supply water during future droughts.

BackgroundUnconventional natural gas (UNG) extraction (fracking) is ongoing in 29 North American shale basins (20 states), with ~6000 wells found within the Fayetteville shale (north-central Arkansas). If the chemical signature of fracking is detectable in streams, it can be employed to bookmark potential impacts. We evaluated benthic biofilm community composition as a proxy for stream chemistry so as to segregate anthropogenic signatures in eight Arkansas River catchments. In doing so, we tested the hypothesis that fracking characteristics in study streams are statistically distinguishable from those produced by agriculture or urbanization.ResultsFour tributary catchments had UNG-wells significantly more dense and near to our sampling sites and were grouped as ‘potentially-impacted catchment zones’ (PICZ). Four others were characterized by significantly larger forested area with greater slope and elevation but reduced pasture, and were classified as ‘minimally-impacted’ (MICZ). Overall, 46 bacterial phyla/141 classes were identified, with 24 phyla (52%) and 54 classes (38%) across all samples. PICZ-sites were ecologically more variable than MICZ-sites, with significantly greater nutrient levels (total nitrogen, total phosphorous), and elevated Cyanobacteria as bioindicators that tracked these conditions. PICZ-sites also exhibited elevated conductance (a correlate of increased ion concentration) and depressed salt-intolerant Spartobacteria, suggesting the presence of brine as a fracking effect. Biofilm communities at PICZ-sites were significantly less variable than those at MICZ-sites.ConclusionsStudy streams differed by Group according to morphology, land use, and water chemistry but not in biofilm community structure. Those at PICZ-sites covaried according to anthropogenic impact, and were qualitatively similar to communities found at sites disturbed by fracking. The hypothesis that fracking signatures in study streams are distinguishable from those produced by other anthropogenic effects was statistically rejected. Instead, alterations in biofilm community composition, as induced by fracking, may be less specific than initially predicted, and thus more easily confounded by agriculture and urbanization effects (among others). Study streams must be carefully categorized with regard to the magnitude and extent of anthropogenic impacts. They must also be segregated with statistical confidence (as herein) before fracking impacts are monitored.

Nonpoint source (NPS) pollution from agricultural and urban development is a primary source of nutrients and decreased water quality in aquatic systems. Installation of best management practices (BMPs) within critical source areas of the watershed can be helpful at reducing the transport of nutrients to waterbodies; however, prioritizing these areas may be difficult. The objective of this study was to develop several potential frameworks for prioritizing subwatersheds using baseflow water chemistry data in relation to a simple human development index (HDI; total percent agriculture and urban development). At a monthly interval, samples were collected at 26 sites throughout the Oklahoma portion of the Lake Wister Watershed (LWW) and analyzed for total nitrogen, total phosphorus, total suspended solids, and chlorophyll a. Changepoint analysis for each parameter found significant thresholds for each of the parameters ranging from 20 to 30% HDI. Changepoint analysis summary statistics were used to develop prioritization frameworks for the LWW that could be used to target subwatersheds where BMP installation would have the greatest effect at improving water quality. Additionally, regression models developed from the relationships between water quality parameters and HDI values serve as realistic targets for improving water quality, with the modeled line representing the target concentration for a given HDI value. After BMPs have been implemented, baseflow monitoring should continue at the subwatershed scale to track changes in water quality. Focusing monitoring efforts at the subwatershed scale will provide an earlier indication of the effectiveness of BMPs, as it may take several decades to detect improvements in water quality at the larger watershed scale.

Nuisance periphyton growth influences the aesthetics, recreation, and aquatic life of waterbodies. Partners Lake is a shallow spring-fed lake in the headwaters of the Illinois River Watershed in Cave Springs, Arkansas, that experiences nuisance growth of periphyton (i.e., Spirogyra spp.) each year. The ratio of dissolved nitrogen (N ~5.0 mg L-1) and phosphorus (P ~0.030 mg L-1) in the lake water (N:P≥288), as well as nutrient limitation assays, suggests that periphyton growth should be P-limited. While the water column lacks sufficient P to promote growth, the sediments have the ability to release P to the overlying water; P-flux ranged from 1.63 mg m-2 d-1 to over 10 mg m-2 d-1, reaching final concentrations of 0.08 to 0.34 mg L-1. However, soluble reactive phosphorus concentrations were consistently at or below 0.030 mg L-1, in the lake, suggesting that the periphyton were likely immobilizing P as quickly as it was released from the sediments. In the lab, maximal periphyton growth (~30 to 35 mg m-2) occurred in the 0.10 to 0.25 mg L-1 P treatments, over a 6 day incubation period. Similar levels of growth occurred when lake sediments were the P source, suggesting P released from the sediments is sufficient to support nuisance algal growth. We need to begin managing the legacy P stored in the sediments, in addition to external P loads, because internal P can sustain nuisance periphyton biomass when N is not limiting.

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