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The potential impacts of climate change on BMP effectiveness were investigated using SWAT simulations for an agricultural watershed that drains into the Chesapeake Bay in the U.S. Northeast climate region. Critical source areas (CSAs) for sediments, nitrogen, and phosphorus, identified for current and future climate (SRES scenarios A1B and A2), were classified by density to support BMP prioritization schemes. BMPs were designed for these CSAs and tested against current and future climate using SWAT simulations to evaluate their robustness. A second set of BMPs was designed by optimization for all agricultural and urban lands in the study watershed and was similarly tested for robustness. In both cases, the design goal was for the watershed's water quality response to meet the bay TMDLs once BMPs were implemented. Results indicated that density 2 and 3 CSAs (hotspots exporting excess amounts of 2 or 3 constituents) may be good prioritization targets, but reaching the bay TMDLs would still require targeting all CSAs. BMPs designed for CSAs under current climate were effective to reach bay TMDLs under current climate but not under scenarios A1B and A2. BMPs designed for CSAs under scenario A2 were effective to reach the bay TMDLs under all climates, except for nitrogen under A2. Similarly, BMPs optimized for agricultural and urban lands, when designed for current climate, were effective in meeting TMDLs for current climate only. Optimizing these BMPs for future climate produced a design that met TMDLs under both current and future climates, except for nitrogen with future climate. However, in this case, the nitrogen TMDL was exceeded by a smaller amount than in the CSA design. It was concluded that, in the U.S. Northeast, BMPs designed to remediate water quality problems under current climate will be insufficient to maintain water quality with climate change. Increased annual rainfall and storm intensity will increase the proportion of watershed area needing BMPs, and current hotspots will generate excess amounts of new constituents that will require re-design of existing BMPs. Community-based participatory strategies will likely be required to foster BMP adoption and sustain water quality gains in the Chesapeake Bay region. [ABSTRACT FROM AUTHOR]

Suspended sediment is the primary pollutant prevalent in runoff waters exiting construction sites with exposed and disturbed land. In this research, the effectiveness of a chemical stabilizer, known as anionic polyacrylamide (PAM), to prevent erosion and promote sedimentation was examined using different application methods (i.e., dry granular vs. semi-dissolved solution). In this study, the effectiveness of Silt Stop 712, a proprietary PAM product, was tested using different application methods at three different rates, i.e., 16.8, 28, and 39.2 kg ha-1 (15, 25, and 35 lbs acre-1), on bare, unseeded, unprotected 1.2 m x 0.6 m x 0.08 m (4 ft x 2 ft x 0.25 ft) laboratory-scale soil test plots. Laboratory-scale testing procedures using simulated rainfall were applied to mimic interrill erosion and sediment detachment scenarios similar to a highway embankment with a compacted 3H: 1V fill slope. Our results showed that dry PAM treatments applied at the recommended rate of 39.2 kg ha-1 (35 lbs acre-1) were capable of reducing turbidity by 97% and net soil loss by approximately 50% in comparison to the bare soil control Conversely, semi-dissolved PAM treatments applied at the same rate, i.e., 39.2 kg ha-1 (35 lbs acre-1), followed by a drying period of 48 h prior to the experiment, reduced turbidity by approximately 69% and soil loss by 76%. The lower application rates, i.e., 16.8 and28 kg ha-1 (15 and25 lbs acre-1), of semi-dissolved PAM without a drying time were observed to lose effectiveness after about 40 min; however, the higher application rate of 39.2 kg ha-1 (35 lbs acre-1) of semi-dissolved PAM provided consistent turbidity reductions throughout the entire experiment. Based on these results: (1) dry PAM applied directly to the surface at the manufacturer's recommended rate was more effective as a sediment control (i.e., turbidity reduction) measure, and (2) semi-dissolved PAM applied directly to the surface at the manufacturer's recommended rate and allowed to dry for 48 h prior to rainfall was a more effective erosion control (i.e., soil loss reduction) measure. [ABSTRACT FROM AUTHOR]

As climate changes, the uncertainty of water availability, changing magnitudes of nonpoint-source pollution, and uncertainty of best management practice (BMPs) effectiveness are issues that watershed managers and stakeholders must consider and plan for. The objective of this study was to determine how BMP effectiveness will be affected by climate change using the Soil and Water Assessment Tool (SWAT). Using downscaled monthly precipitation and temperature data output from the Community Climate System Model (CCSM), daily precipitation and temperature data were produced based on observed weather station data for the Tuttle Creek Lake watershed in Kansas and Nebraska. The A1B, A2, and B1 SRES emissions scenarios were compared to historical CCSM model output. Eight agricultural BMPs were physically represented within SWAT and compared across climate scenarios. Water yield, surface runoff, baseflow, sediment load, nitrogen load, and phosphorus load increased in all three future climate scenarios. Terraces, contour farming, and native grass were determined to be the most effective in pollution load reduction and percent efficiency at the field and watershed scales in future scenarios. Porous gully plugs and filter strips showed no significant changes in pollution load or percent reduction. Grazing management, no-tillage, conservation tillage, and grazing management percent and load reduction in future scenarios varied at the field and watershed scales. This study demonstrates that BMP performance in terms of sediment, nitrogen, and phosphorus reduction significantly changes in future climate scenarios at the field scale, while performance generally does not change significantly at the watershed scale. [ABSTRACT FROM AUTHOR]

Soil erosion from agricultural lands and the subsequent transport of sediment and sediment-bound nutrients (particularly P) are serious problems contributing to surface water pollution and threatening agricultural sustainability. Raindrop impact on bare soil destabilizes soil aggregates and leads to surface sealing, increasing runoff volumes and soil loss. Surface-applied polyacrylamide (PAM) decreases soil erosion by stabilizing the soil structure and reducing surface sealing. Previous research has shown that surface-applied PAM reduces erosion at relatively high application rates (20 to 80 kg ha-l). The purpose of this study was to evaluate the effectiveness and longevity of a new liquid/emulsion PAM formulation to reduce runoff, sediment, and P loss from rainfed agricultural fields. The formulation was applied using a hand sprayer at a low PAM rate of 5 kg ha-1 (13,333 L of solution ha-1). Plot-scale field rainfall simulations (75 mm ha-1) were conducted on individual test plots at three test intervals (rainfall simulated 2 days, 3 weeks, and 10 weeks after DAM application) on two soil types (Ashdale silt loam and Plano silt loam). The new polymer formulation, Soil Net EM-1000-50, reduced runoff volumes an average of 100% at the 2-day test interval, 59% at the 3-week test interval, and 55% at the 10-week test interval. Overall, larger rainfall depths were applied to treatment plots prior to runoff generation compared to controls. The most significant differences were observed at the 2-day test interval, when an average of 141 mm of rainfall was applied to the PAM-treated plots before runoff started, compared to 82 mm for the controls. These runoff reductions are not only important in terms of erosion but may also enhance water supply through increased infiltration. Sediment loss was reduced an average of 100% at the 2-day test interval, 80% at the 3-week test interval, and 74% at the 10-week test interval. Phosphorus loss was reduced an average of 100% at the 2-day test interval, 75% at the 3-week test interval, and 83% at the 10-week test interval. The polymer treatment was more effective on the Ashdale silt loam, which had received manure during the two years preceding the rainfall simulations. Manure application was the primary difference between the two soils (manure was not applied to the Plano silt loam), suggesting that the PAM treatment reacts more favorably to manured soils. The low cost of this new PAM technology (approx. $25 ha-1) coupled with its success in reducing runoff, sediment, and P loss over a 10-week period, make EM-1000-50 an attractive and economically feasible management practice for agricultural producers in rainfed regions. [ABSTRACT FROM AUTHOR]

Surface water impairments for pathogens are a major problem in waterways throughout the United States, especially in New Jersey. Fecal coliform (FC) counts are commonly used as an indicator of pathogens. In this study, bioretention systems, which are stormwater best management practices, were modeled with columns. Unlike traditional detention basins, bioretention systems are meant to manage water quality in addition to quantity and peak flow rates. Typical rainfall conditions for New Jersey were mimicked in the laboratory with regard to rainfall intensity and stormwater composition (bacterial colony counts) using a diluted manure slurry. The applied influent flow rate was 77.0 mL/min, while the average leachate flow rate observed in the bottom spout was 20.8 mL/min. The hydraulic performance of the columns was adequate in that the influent completely infiltrated well before the New Jersey Department of Environmental Protection (NJDEP) performance standard of 72 h. However, ponding of more than 30.5 cm (the NJDEP performance standard for ponding) was observed in some of the simulations. The mean, median, and range of reduction coefficients for fecal coliform (FC) were 91.6%, 98.6%, and 54.5% to 99.8%, respectively, for 13 simulations. The mean, median, and range of reduction coefficients for total suspended solids (TSS) were 91.5%, 91.9%, and 81.0% to 99.4%, respectively, for 15 simulations. The average pH of the influent water was 6.87, while the average leachate pH was 4.61. It is likely that both adsorption and filtration were responsible for the FC and TSS reductions. Die-off factors that may have influenced FC reduction in addition to adsorption and filtration are discussed. Reduction coefficients were observed to not necessarily be the ultimate indicator of system performance or effectiveness, as they are conditional upon the leachate concentration. [ABSTRACT FROM AUTHOR]

Growing urbanization has led to increasing concern and emphasis on better construction site stormwater management. The objectives of this study were to determine the effectiveness of using compost rather than conventional hydroseeding or topsoil to reduce erosion from disturbed soils. The runoff rates, interrill erosion rates, and interrill erodibility factors from five compost and two control treatments (hydroseeding and topsoil) were compared. Compost treatments followed Texas Department of Transportation (TxDOT) specifications for compost applied as an erosion control at 1.3 and 5 cm depths. Rainfall simulation was used to apply a storm of 92 mm h-1. Surface runoff was collected after 5 min of rainfall (first-flush) and during the last 30 min of rainfall (steady-state). The first-flush mean runoff from the 5 cm depth general-use compost treatment was significantly higher than that of all other treatments. The other treatments (50% woodchips and 50% compost blend at 1.3 and 5 cm depths) and hydroseeding had significantly lower runoff and erosion rates compared to topsoil and compost manufactured topsoil at first-flush and steady-state. Furthermore, there were no performance differences between 1.3 and 5 cm compost applications at first-flush or steady-state. The TxDOT specification for erosion control compost depth might be able to be reduced from 5 to 1.3 cm. [ABSTRACT FROM AUTHOR]