Highlights Convective currents led to hydraulic flux and transport of P between bottom and surface waters of the littoral zone. Hydraulic flux was primarily into the bottom of the cove and out of the cove along the surface. Eutrophic littoral areas are a significant source of P to the photic zone of reservoirs, supporting algal growth. Abstract . Eutrophication of surface waters is defined by excessive algal growth, with consequences for drinking water treatment. The sources of phosphorus (P) in southern U.S. reservoirs that fuel peak algal productivity in late summer are still not fully understood. One potential source is reservoir littoral zones, which have been described as the most productive zone of a waterbody. A shallow cove named Granny Hollow in Beaver Lake, northwest Arkansas, was selected as an isolated and semi-controlled location to measure and model sources of P and its transport in a littoral area for the month of July 2018. Hydraulic and P fluxes between the reservoir and littoral area were quantified through field measurements and a 3D lake model. In quantifying hydraulic flux for the month of July, the model indicated that water tended to move into the cove along the bottom and out along the top, with a net hydraulic flux out of the cove of -723,000 m3. Peak surface velocity in the cove averaged 2.09 cm s-1 for the month of July, while peak bottom velocity was 1.29 cm s-1. Diurnally, water movement switched directions, moving out of the cove along the surface during differential heating and into the cove along the surface during differential cooling due to thermoconvective flow. During differential heating, the water velocity and hydraulic flux to the main reservoir channel along the surface of the cove were greater than the velocity and flux in the opposite direction during differential cooling. The sources of P within the cove during July included P released from bottom sediments within the cove and littoral zone and transport of P from the reservoir channel to the cove. Transport of P from the main reservoir into the cove was a result of thermoconvective flow. During differential heating, bottom waters from the main reservoir channel were transported to the surface within the littoral zone by thermoconvective currents flowing upslope from deeper to shallower waters. This resulted in P exchange between the reservoir and littoral area and is significant because it represents movement of P from the bottom of the reservoir upward into the photic zone, where it can be used for algal productivity. During July 2018, it was estimated that 13.3 kg of P were transported from the bottom of the cove to the surface by convective currents and subsequently out of the cove. This study shows that eutrophic coves represent a significant source of P to the reservoir and more importantly to the photic zone, supporting algal growth. Keywords: 3D reservoir model, Eutrophication, Internal loading, Thermoconvective flow.

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.

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).

Over the past 100 years, peanuts and peanut products have become an increasingly common food staple in the United States and around the globe. This chapter explores the role of peanuts as a source of nutrition and a plant-based protein alternative. In addition, the environmental impacts associated with the production of peanuts are also explored. Peanuts are grown in a number of regions around the world, and their postharvest life cycle stages include drying, grading, shelling, and endpoint product preparation. Peanut products can provide a dense source of nutrients, and tend to have high concentrations of proteins and amino acids. The emerging knowledge suggests that the climate change and water use impacts of peanut production are lower than other plant-based and animal-based protein sources that are currently available in the marketplace. We are just beginning to measure sustainability impacts across agricultural products, but peanut production, processing, consumption, and disposal are looking very promising across most metrics.

Data are often collected during or after hydrological and water quality (H/WQ) model development, thus limiting the ability for direct comparison or use in calibration and validation. In this study, we demonstrate a way to validate the performance of three previously performed watershed simulations by comparing SWAT-simulated loads prior to 2011 with loads estimated from monitoring data collected after the SWAT models were completed. Water quality data, including total suspended solids, total phosphorus, and nitrate-nitrogen concentrations, were collected from the three watersheds from 2011 through 2013. Calibration and validation for WQ was accomplished for the Poteau River watershed using historical monitoring data. However, similar data were not available for the Strawberry and Upper Saline River watersheds, and their subsequent SWAT models were not calibrated or validated for WQ. A combination of regression, residual, and ANOVA analyses was used to post-validate the SWAT models beyond their simulation periods. Results indicated that the SWAT-simulated loads were in general agreement with the loads estimated from monitoring data for the Poteau and Saline River watersheds, but not for the Strawberry River watershed. A comparison of constituent loads modeled using SWAT and estimated from monitoring data for the Strawberry River watershed resulted in statistically different slopes and residuals and dissimilar ellipse orientation, range, and variance for each constituent. Load comparisons for the Saline and Poteau River watersheds using these same techniques resulted in variable slope and residual significance but improved ellipse orientation, range, and variance for each constituent. The approach used in this study was sufficient for analyzing the adequacy of simulated loads and could inform users concerning model performance when an uncali-brated model is used to make policy decisions and allocate resources.

ABSTRACT 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.

The U.S. produced 2.6 billion kg of peanuts during the 2012 growing season, up from 1 billion kg in 2002, a 160% increase. Over $2 billion worth of peanuts were produced in seven key states: Alabama, Georgia, Oklahoma, North Carolina, South Carolina, Texas, and Virginia. Approximately 32% of U.S. peanuts were made into peanut butter, representing $850 million in sales. The goal of this study was to quantify the greenhouse gas ( GHG) emissions associated with the production, consumption, and disposal of peanut butter packaged in the U.S. A life cycle assessment (LCA) model was created in SimaPro 7.3, and a combination of sources including peer-reviewed literature, producer surveys, and experts' opinions were used to develop and populate a comprehensive model of the peanut butter life cycle from cradle to grave. The system boundaries included peanut production on farm, shelling, blanching, roasting, peanut butter manufacture, consumer use, and package disposal. The functional unit ( FU) was 1 kg of peanut butter consumed by U.S. consumers. GHG impacts were assessed using the IPCC 2007 global warming potential ( GWP) methodology. A Monte Carlo analysis was performed in order to determine the 90% confidence interval of the mean GHG emissions. The Monte Carlo analysis indicated that CO(2)e emissions were between 2.38 and 3.49 kg CO(2)e per FU at a 90% confidence interval with a mean of 2.88. The processor subsystem contributed the greatest amount of GHG to the system ( 1.01 kg CO(2)e), followed by consumer use and disposal ( 0.84 kg CO(2)e) and retail ( 0.51 kg CO(2)e).