Agricultural conservation practices (CPs) are commonly implemented to reduce diffuse nutrient pollution. Climate change can complicate the development, implementation, and efficiency of agricultural ...CPs by altering hydrology, nutrient cycling, and erosion. This research quantifies the impact of climate change on hydrology, nutrient cycling, erosion, and the effectiveness of agricultural CP in the Susquehanna River Basin in the Chesapeake Bay Watershed, USA. We develop, calibrate, and test the Soil and Water Assessment Tool-Variable Source Area (SWAT-VSA) model and select four CPs; buffer strips, strip-cropping, no-till, and tile drainage, to test their effectiveness in reducing climate change impacts on water quality. We force the model with six downscaled global climate models (GCMs) for a historic period (1990–2014) and two future scenario periods (2041–2065 and 2075–2099) and quantify the impact of climate change on hydrology, nitrate-N (NO3-N), total N (TN), dissolved phosphorus (DP), total phosphorus (TP), and sediment export with and without CPs. We also test prioritizing CP installation on the 30% of agricultural lands that generate the most runoff (e.g., critical source areas-CSAs). Compared against the historical baseline and with no CPs, the ensemble model predictions indicate that climate change results in annual increases in flow (4.5±7.3%), surface runoff (3.5±6.1%), sediment export (28.5±18.2%) and TN export (9.5±5.1%), but decreases in NO3-N (12±12.8%), DP (14±11.5), and TP (2.5±7.4%) export. When agricultural CPs are simulated most do not appreciably change the water balance, however, tile drainage and strip-cropping decrease surface runoff, sediment export, and DP/TP, while buffer strips reduce N export. Installing CPs on CSAs results in nearly the same level of performance for most practices and most pollutants. These results suggest that climate change will influence the performance of agricultural CPs and that targeting agricultural CPs to CSAs can provide nearly the same level of water quality effects as more widespread adoption.
Climate change alters watershed and field level hydrology, nutrient cycling, and erosion.
Agricultural best management practices can mitigate the impact of climate change on water quality. Display omitted
•Climate change impacts hydrology, nutrient cycling and erosion potentially degrading water quality•Agricultural conservation practices can mitigate the impact of climate change on water quality•Targeting on critical source areas results in nearly the same water quality protection as widespread targeting
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The United States Environmental Protection Agency has established aggressive nutrient reduction goals to achieve water quality objectives for the Chesapeake Bay estuary. Nitrogen (N) reduction goals ...are proving particularly difficult to meet with an additional 20.4 million kg of annual nitrogen reductions needed by 2025, and many of the easily achievable and low-cost N reductions have been realized. We assess the feasibility of employing woodchip denitrifying bioreactors to treat legacy N derived from spring discharge in the Mid-Atlantic region. We estimate that in excess of 6100 kg of soluble N is discharged daily from United States Geological Survey identified springs in four Mid-Atlantic states within the Chesapeake Bay watershed. Based on typical bioreactor removal efficiency (30–55%) and potentially treatable flows (<6000 m3/d), widespread adoption of bioreactors to treat legacy N from 231 springs could conservatively result in 420–770 kg N removed per day, while strategic adoption targeting 48 springs with N concentrations of at least 3 mg/L and flows of at least 500 m3/d could result in 322–590 kg N removed per day more cost-effectively and with far fewer installations. A cost analysis indicates bioreactors can be a cost-effective N removal strategy, generally removing N for less than $5/kg·y. Relative to other nonpoint source pollution control practices, bioreactors also offer the ability to remove larger quantities of N per installation and are more easily monitored to quantify N reductions.
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IJS, KILJ, NUK, PNG, UL, UM
Mitigating the environmental impact of nonpoint source pollution from intensively managed urban and agricultural landscapes is of paramount concern to watershed managers. Golf course turfgrass ...systems, which receive significant fertilizer inputs, have been cited as significant sources of nutrient loading to groundwater and surface water, but a contemporary synthesis of golf course nutrient export rates is lacking. This review of nitrogen (N) and phosphorus (P) loss from golf courses and the factors affecting it aims to support watershed management efforts and decision making. We discuss previous literature reviews, examine seven golf course studies that quantify nutrient export from delineated drainage areas, and analyze the results of 40 turfgrass plot experiments. Studies were collected systematically and selected based on predetermined inclusion criteria. Combining evidence from both watershed- and plot-scale studies, typical inorganic N and P losses from golf courses via leaching and runoff are on the order of 2–12 kg ha−1 yr−1 and 0.1–1.0 kg ha−1 yr−1, respectively. Typical total N and P losses are around 2–20 kg ha−1 yr−1 and 1.5–5 kg ha−1 yr−1, respectively. However, the potential for large variation in export rates across 2–3 orders of magnitude must be emphasized. The body of turfgrass literature stresses the importance of best management practices (BMPs) related to applying fertilizer to match plant needs and reducing opportunities for its transport. Accounting for all sources of nutrients, especially soil P, in determining fertilizer application rates and avoiding excessive irrigation to prevent leaching of nutrients from the rootzone is particularly important. BMPs can also reduce nutrient leaching and runoff by controlling the movement of water across the landscape and promoting natural nutrient attenuation, such as with vegetative stream buffers.
•Plot- and watershed-scale studies of golf course nutrient loss were reviewed.•Although turfgrass nutrient loss varies between sites and with different management,•Typical nitrogen export rates are 2–12 kg ha−1 yr−1 NO3–N and 6–20 kg N/ha/yr TN.•Typical phosphorus export rates are 0.1–1 kg ha−1 yr−1 PO4–P and 1.5–5 kg ha−1 yr−1 TP.•Appropriate fertilizer/irrigation use reduces N and P loss and ecological impact.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In efforts to combat eutrophication, the U.S. Environmental Protection Agency has established aggressive nitrogen, phosphorus, and sediment reduction goals for states and regulated dischargers within ...the Chesapeake Bay watershed. Chesapeake Bay jurisdictions are struggling to meet the nutrient (N, P) reduction goals. This paper evaluates the efficacy of removing legacy N from groundwater as a compliance strategy for three potential classes of “buyers” of N reductions in the Chesapeake Bay watershed: permitted point sources, permitted municipal stormwater systems (called MS4s), and state nonpoint source (NPS) managers. We compare denitrifying spring bioreactors with conventional agricultural and urban NPS removal technologies using evaluative criteria important to each of these buyers. Results indicate that spring bioreactors compare favorably to other N removal technologies based on cost effectiveness, administrative costs, and certainty of N removal performance. Most conventional NPS technologies provide greater ancillary benefits. On balance, denitrifying spring bioreactors add a valuable compliance option to those tasked with achieving Bay N reduction goals.
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IJS, KILJ, NUK, PNG, UL, UM
Denitrifying bioreactors (DNBRs) harness the natural capacity of microorganisms to convert bioavailable nitrogen (N) into inert nitrogen gas (N2) by providing a suitable anaerobic habitat and an ...organic carbon energy source. Woodchip systems are reported to remove 2 to 22 g N m−3 d−1, but the potential to enhance denitrification with alternative substrates holds promise. The objective of this study was to determine the effect of adding biochar, an organic carbon pyrolysis product, to an in‐field, pilot‐scale woodchip DNBR. Two 25‐m3 DNBRs, one with woodchips and the other with woodchips and a 10% by volume addition of biochar, were installed on the Delmarva Peninsula, Virginia. Performance was assessed using flood‐and‐drain batch experiments. An initial release of N was observed during the establishment of both DNBRs, reflecting a start‐up phenomenon observed in previous studies. Nitrate (NO3−–N) removal rates observed during nine batch experiments 4 to 22 mo after installation were 0.25 to 6.06 g N m−3 d−1. The presence of biochar, temperature, and influent NO3−–N concentration were found to have significant effects on NO3−–N removal rates using a linear mixed effects model. The model predicts that biochar increases the rate of N removal when influent concentrations are above approximately 5 to 10 mg L−1 NO3−–N but that woodchip DNBRs outperform biochar‐amended DNBRs when influent concentrations are lower, possibly reflecting the release of N temporarily stored in the biochar matrix. These results indicate that in high N–yielding systems the addition of biochar to standard woodchip DNBRs has the potential to significantly increase N removal.
Core Ideas
Novel biochar amendment to denitrifying bioreactor investigated on Delmarva Peninsula.
Biochar can enhance N removal in woodchip denitrifying bioreactors.
Biochar may also serve as a temporary N sink and mitigate the first flush.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Streamflow forecasts are essential for water resources management. Although there are many methods for forecasting streamflow, real-time forecasts remain challenging. This study evaluates streamflow ...forecasts using a process-based model (Soil and Water Assessment Tool-Variable Source Area model-SWAT-VSA), a stochastic model (Artificial Neural Network -ANN), an Auto-Regressive Moving-Average (ARMA) model, and a Bayesian ensemble model that utilizes the SWAT-VSA, ANN, and ARMA results. Streamflow is forecast from 1 to 8 d, forced with Quantitative Precipitation Forecasts from the US National Weather Service. Of the individual models, SWAT-VSA and the ANN provide better predictions of total streamflow (NSE 0.60–0.70) and peak flow, but underpredicted low flows. During the forecast period the ANN had the highest predictive power (NSE 0.44–0.64), however all three models underpredicted peak flow. The Bayesian ensemble forecast streamflow with the most skill for all forecast lead times (NSE 0.49–0.67) and provided a quantification of prediction uncertainty.
•Several modeling techniques are developed and forced with Quantitative Precipitation Forecasts to predict streamflow.•Both stochastic and process-based models are capable of providing valuable streamflow forecast information.•An ensemble model forecast streamflow with the greatest predictive power and quantified uncertainty in predictions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Denitrifying bioreactors (DNBRs) are an emerging technology used to remove nitrate‐nitrogen (NO3−) from enriched waters by supporting denitrifying microorganisms with organic carbon in an anaerobic ...environment. Field‐scale investigations have established successful removal of NO3− from agricultural drainage, but the potential for DNBRs to remediate excess phosphorus (P) exported from agricultural systems has not been addressed. We hypothesized that biochar addition to traditional woodchip DNBRs would enhance NO3− and P removal and reduce nitrous oxide (N2O) emissions based on previous research demonstrating reduced leaching of NO3− and P and lower greenhouse gas production associated with biochar amendment of agricultural soils. Nine laboratory‐scale DNBRs, a woodchip control, and eight different woodchip‐biochar treatments were used to test the effect of biochar on nutrient removal. The biochar treatments constituted a full factorial design of three factors (biochar source material feedstock, particle size, and application rate), each with two levels. Statistical analysis by repeated measures ANOVA showed a significant effect of biochar, time, and their interaction on NO3− and dissolved P removal. Average P removal of 65% was observed in the biochar treatments by 18 h, after which the concentrations remained stable, compared with an 8% increase in the control after 72 h. Biochar addition resulted in average NO3− removal of 86% after 18 h and 97% after 72 h, compared with only 13% at 18 h and 75% at 72 h in the control. Biochar addition also resulted in significantly lower N2O production. These results suggest that biochar can reduce the design residence time by enhancing nutrient removal rates.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
As much as 66% of the Nile River flow that reaches Egypt originates in the Highlands of the Ethiopian Blue Nile Basin (BNB). This imbalance in water availability poses a threat to water security in ...the region and could be impacted by climate change. This study coupled a watershed model analysis with bias corrected and downscaled Intergovernmental Panel on Climate Change (IPCC) Coupled Model Intercomparison Project 5 (CMIP5) climate data to assess the potential impact of climate change on water resources and sediment dynamics in two critical headwater basins of the BNB. Climate scenarios analyzed include RCP2.6, RCP4.5, RCP6.0, and RCP8.5 from six climate models, which were used to force watershed models calibrated against historic streamflow for six gauged sub-watersheds in the Tana basin and four gauged sub-watersheds in the Beles basin. We developed distributed watershed model parameter estimates from the gauged sub-watersheds, which were applied to un-gauged portions of the basins using topographically informed parameter transfer functions. We analyzed the impact of climate change for two future time periods (2041–2065 and 2075–2099) by running each of the six downscaled and bias corrected CMIP5 model predicted climate forcings through the watershed models to assess the impact of ensemble model mean and variance in climate change prediction on water availability and sediment transport. Results indicate that the Tana and Beles basins will experience increases both in mean annual flow (22-27%) and sediment concentrations (16-19%). Interestingly, and of significance for water availability and hydropower development, the monsoon in the Tana and Beles basins will lengthen by approximately four (Tana) to six (Beles) weeks. These results highlight both the considerable variance in climate change impacts as well as the potential for beneficial outcomes in the region.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Assessing climate change (CC) impacts on urban watersheds is difficult due to differences in model spatial and temporal scales, making prediction of hydrologic restoration a challenge. A methodology ...was developed using an autocalibration tool to calibrate a previously developed Storm Water Management Model (SWMM) of Difficult Run in Fairfax, Virginia. Calibration was assisted by use of multi-objective optimization. Results showed a good agreement between simulated and observed data. Simulations of CC for the 2041–2068 period were developed using dynamically downscaled North American Regional CC Assessment Program models. Washoff loads were used to simulate water quality, and a method was developed to estimate treatment performed in stormwater control measures (SCMs) to assess water quality impacts from CC. CC simulations indicated that annual runoff volume would increase by 6.5%, while total suspended solids, total nitrogen, and total phosphorus would increase by 7.6%, 7.1%, and 8.1%, respectively. The simulations also indicated that within season variability would increase by a larger percentage. Treatment practices (e.g., bioswale) that were intended to mitigate the negative effects of urban development will need to deal with additional runoff volumes and nutrient loads from CC to achieve the required water quality goals.
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