Core Ideas Nutrient concentrations in streams are positively correlated during baseflow and runoff conditions. High nutrient concentrations at baseflow suggest high nutrient loads from nonpoint sources. Manage nonpoint sources by targeting subwatersheds with elevated nutrient concentrations during baseflow. Focusing on baseflow conditions frees up resources to monitor water quality more broadly across watersheds. Nationwide, a substantial amount of resources has been targeted toward improving water quality, particularly focused on nonpoint‐source pollution. This study was conducted to evaluate the relationship between nutrient concentrations observed during baseflow and runoff conditions from 56 sites across five watersheds in Arkansas. Baseflow and stormflow concentrations for each site were summarized using geometric mean and then evaluated for directional association. A significant, positive correlation was found for NO3–N, total N, soluble reactive P, and total P, indicating that sites with high baseflow concentrations also had elevated runoff concentrations. Those landscape factors that influence nutrient concentrations in streams also likely result in increased runoff, suggesting that high baseflow concentrations may reflect elevated loads from the watershed. The results highlight that it may be possible to collect water‐quality data during baseflow to help define where to target nonpoint‐source pollution best management practices within a watershed.

Abstract. Change point analysis was used to explore the interactions between watershed characteristics and concentrations of nitrate-nitrogen, total nitrogen, soluble reactive phosphorus, and total phosphorus in streams within the Ozark Highlands, Arkansas Valley, and Ouachita Mountains ecoregions of Arkansas. Thresholds were identified for multiple watershed metrics used to predict water quality, including percent forest in the catchment, agricultural and forested land use in the riparian buffer, stream density, and poultry house density. Based on the observed relationships from the sampled watersheds, we propose four risk indicators to improve the identification of critical source areas for NPS pollution mitigation: subwatersheds that have less than 50% forested area within the drainage area, less than 50% forested area in the riparian buffer zone, more than 0.9 poultry houses km-2, and a stream density that exceeds 50 m ha-1. Keywords: Nonpoint-source pollution, Source water protection, Watershed management.

Abstract. Algae play an important role in the internal nutrient cycling of shallow lakes and coves. Algae of shallow water bodies have been shown to thrive and even lead to eutrophic conditions despite a lack of measurable quantities of biologically available phosphorus (P) in the water during summer months. To study how sediment P release and algal growth are connected, water and sediment samples were collected in a shallow eutrophic cove on Beaver Lake in northwest Arkansas. Water quality profiles depicting temperature, dissolved oxygen, nutrients, metals, and photic zone chlorophyll-a were collected weekly from 21 May to 10 July 2018 at three points in the cove: one shallow, one at the cove midpoint, and one at the deepest part of the cove. Cove sediment samples were collected at similar points as the water quality samples for equilibrium P concentration (EPCo) analysis, sediment core incubation, and sediment composition. EPCo for the sediments ranged from 0.024 to 0.027 mg L-1. Sediment cores exposed to aerobic conditions typical of shallow areas had P release rates ranging from 1.37 to 2.02 mg m-2 d-1. Concentrations of soluble reactive P (SRP) in the water column from the weekly water quality sampling averaged 0.002 ±0.003 mg L-1, and photic zone SRP concentrations averaged 0.002 ±0.004 mg L-1 for all sampling sites. The chlorophyll-a concentration increased from 10 to 40 µg L-1 during the period from 21 May to 25 June. When SRP << EPCo, conditions favor the release of SRP from sediments to the overlying water. This was confirmed with the aerobic sediment core incubation in which algal demand was controlled using dark conditions and the release rates were >1.37 mg L-1 d-1. Core aerobic release rates and EPCo conditions both confirmed the release of P under aerobic conditions; however, it appears that algal demand sustained low SRP conditions. This created a nutrient cycle in which algae imposed a nutrient gradient favoring P release by keeping SRP conditions below the EPCo. This study indicates that algal growth potential in shallow water bodies is not limited by SRP concentrations measured within the water column. Studies of shallow water bodies with low SRP concentrations and high productivity should look to the sediments as a source of P to fuel algal growth. Finally, these findings suggest that coves play an integral part in algal production and should not be overlooked when determining the overall P budget for a lake or reservoir. Keywords: Aerobic phosphorus release, Equilibrium phosphorus concentration, Sediment core incubation.

The last half century has seen a significant shift in agricultural practices, affecting productivity, resource use, and ultimately, environmental impacts. These increases have been the result of several developments, including increases in irrigation, the expanded application of fertilizers and pesticides, improved plant genetics, and the development of mechanized operations. Changes in production practices are highlighted here for peanut crops for the years 1980 to 2014. This study uses a resource efficiency methodology from cradle-to-farm gate to examine land use, energy efficiency, soil erosion (water and wind), irrigation water usage, and environmental/greenhouse gas emissions. During the historical period, yields increased from under 2000 kg/ha in the Southwest and an average of 3000 kg/ha in the Southeast and Virginia-Carolina regions to over 4000 kg/ha across all regions. Most of this increase occurred after the year 2000. Overall trends of nitrogen fertilizer applications per planted hectare were increasing; however, chemical protections, fuel use and electricity associated with cultivation, harvest, and drying declined. Energy utilization per hectare and kg of peanut showed steady declines over the last 40 years, particularly in the Southeast and Virginia-Carolina production regions. Results indicated that greenhouse gas (GHG) emissions have been on the decline across all production regions, from greater than 1 kg CO2e/kg peanut in the early 1980s to less than 0.6 kg CO2e/kg peanuts in 2013, a 40% decrease in GHG production.

Abstract. Internal phosphorus (P) loading is a leading contributor to eutrophication in reservoirs and can cause harmful algal blooms as well as treatment issues for drinking water reservoirs. Coves are an area of reservoirs that have not received adequate attention, even though they experience higher nutrient and sediment deposition and primary production per unit area when compared to the pelagic zone of the reservoir. This study investigates a shallow eutrophic cove in a northwest Arkansas reservoir called Beaver Lake to better understand the cove’s potential to contribute to P loading and eutrophication within the reservoir. The study period was 3 to 16 July 2018. Water column profiles of depth, temperature, and dissolved oxygen were measured with a floating sensor platform that also contained a weather station. Cove bed sediment samples were collected at three locations in the cove and analyzed for chemical composition through Mehlich III extraction and P, nitrate + nitrite (N+N), and ammonia release rates with aerobic and anaerobic sediment core incubations. Bathymetry data were collected using a depth sonar system. Sensor platform profiles indicated dynamic bottom temperature and dissolved oxygen conditions with transient influxes of hypoxic waters that occurred several times for less than 24 h. The P release rates from bed sediment incubations were as high as 2.02 mg m-2 d-1 under aerobic conditions and 4.45 mg m-2 d-1 under anaerobic conditions. Upon initiation of nitrogen gas bubbling in the sediment cores, anaerobic conditions were delayed by the presence of N+N. Phosphorus release did not occur until denitrification decreased the N+N concentrations enough for reducing conditions to be present. For the study period, a P flux into the water of roughly 1 kg was determined using cove profiles, bathymetry, and P release rates. When compared to whole-lake P release averages for Beaver Lake, eutrophic coves are a disproportionate source of P per unit area within the reservoir. This may offer opportunities for more efficient use of internal loading remediation techniques, such as alum application. The results of this study also suggest that we should not continue to overlook shallow-area bed sediment P flux when considering the P mass balance of a reservoir. Keywords: Eutrophication, Sediment core incubation, Stratification.