Individual Best Management Practices Research Articles

Can the best management practices resist the combined effects of climate and land-use changes on non-point source pollution control?

Climate and land-use changes have an overlying impact on non-point source (NPS) pollution in river basins. However, the control effect of Best Management Practices (BMPs) for NPS pollution is not yet clear under future scenarios. The Soil and Water Assessment Tool (SWAT) model was coupled with the entropy-weighted method, global climate patterns and land-use data to explore the dynamic variations in total nitrogen (TN) and total phosphorus (TP) loads in the Jing River Basin during the baseline (2000−2020) and future periods (2021–2065), evaluate the pollution reduction effectiveness of individual and combined BMPs, and propose practical BMP configurations. Results indicate that a future trend of urban land expansion, particularly in the economic scenario (LU_SSP585), leads to weakened environmental ecosystems, while the sustainable scenario (LU_SSP126) exhibits more balanced land development. The MIROC-ES2L model demonstrates higher Taylor skill scores, forecasted significant increases in precipitation, maximum, and minimum temperatures under the SSP585 scenario. Spatial heterogeneity in TN and TP loads is notable, showing an upward trajectory in the future. The interaction between land-use and climate change has complex effects on TN and TP loads, with land-use-induced TN changes being relatively small (4.6 %) and TP changes substantial (24.3 %). The spatial distribution, under overlying effects, leans towards the influence of climate change, emphasizing its dominant role in TN and TP load variations. Distinct differences exist in the reduction of NPS pollution loads among different BMPs, with combined BMPs demonstrating superior effectiveness. The environmental-cost effectiveness trends of BMPs remain consistent across various future scenarios. RG (Return agricultural land to grass), RG + TT (Terracing), and RG + FR10 (Fertilizer reduction: 10 %) + GW (Grassed waterway) + FS (Filter strip) + TT emerge as the most effective single, double, and multiple BMP combinations, respectively. The results offer valuable insights for preventing and mitigating future NPS pollution risks, optimizing land-use layouts, and enhancing watershed management decisions.

Efficiency analysis of best management practices under climate change conditions in the So-okcheon watershed, South Korea

Best management practices (BMPs) are widely applied to address water quality degradation issues attributed to non-point source pollutants. The objective of this study was to assess the efficiency of two types of BMPs, vegetation filter strips (VFS) and wetlands, in reducing total nitrogen (TN) and total phosphorus (TP) in a watershed, and to investigate whether the efficiency of the two BMPs is maintained under future climate scenarios by employing the Soil and Water Assessment Tool (SWAT). A set of parameters was calibrated using the SWAT Calibration and Uncertainty Program (SWAT-CUP) to ensure acceptable simulation results. Three BMP scenarios were developed by applying VFS and wetlands individually and in combination. Projected climate data from 18 global circulation models under Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) were used to depict climate change conditions. VFS demonstrated 18.2% and 22.9% greater reduction efficiency for TN and TP, respectively, relative to wetlands. When the two BMPs were simultaneously applied, the reduction efficiency was even greater than that of single-BMP implementation (by 7.4% for TN and 6.8% for TP compared to VFS alone and by 25.5% for TN and 29.7% for TP compared to wetlands alone). To assess the effect of climate change, the model simulated results for the period of 2021–2,100. The differences in efficiency between the combined BMP scenario and the individual BMPs increased with greater intensity of climate change, especially in the distant future. Therefore, this study supports the effectiveness of nutrient pollution control by applying multiple BMPs rather than by applying individual BMPs. Furthermore, this research underscores the adaptability and reliability of natural-based solutions in mitigating non-point source pollution in a changing climate, which is essential for effective ecological restoration in complex urban-agricultural landscapes. The study provides valuable insights for watershed managers and policymakers seeking effective strategies to combat nutrient pollution in the face of a changing climate within the unique landscape of South Korea.

Best management practices to reduce soil erosion and change water balance components in watersheds under grain and dairy production

Soil erosion and sedimentation are among the most serious global environmental problems. Soil and water conservation measures have been proven effective ways to reduce soil loss. The objective of this study was to evaluate the impact of three approaches of soil and water conservation measures (soil management, vegetative measures, and structural practices) on soil erosion and water balance of two paired agricultural watersheds located in Southern Brazil. Streamflow and sediment monitoring was carried out from 2016 to 2019 in the two small paired agricultural watersheds; called North watershed (NW) and South watershed (SW). Modeling using Soil & Water Assessment Tool (SWAT) was performed to simulate individual (nine scenarios) and combined (four scenarios) best management practices (BMPs), by including the three approaches. Among the nine individual BMP scenarios, the most effective in reducing soil erosion was crop rotation and cover crop (sediment yield, SY, reduction of 38.4 for NW, and 28.8% for SW). Among the four combined scenarios, the association of all conservation approaches was the most effective in reducing soil erosion (SY reduction of 46 for NW, and 41.5% for SW), followed by the vegetative measures scenario (SY reduction of 43.5 and 34.1% for NW and SW). All combined scenarios increased infiltration and subsurface water components, and decreased surface runoff. The findings of this study can help farmers and policymakers choosing appropriate BMPs to reduce current soil erosion problems and promote water and soil conservation.

Assessing multivariate effect of best management practices on non-point source pollution management using the coupled Copula-SWAT model

Best management practices (BMPs) have wide application in non-point source (NPS) pollution abatement in agricultural watersheds. Multivariate analysis of BMPs reduction effects taking their randomness and correlations into account is significant to spatial optimization of BMPs configuration. However, quantifying the correlations among high-dimensional random variables of BMPs effects is challenging and remains unexplored thoroughly. This study coupled the SWAT with the Vine Copula model to conduct multivariate analysis of BMPs reduction effects considering their randomness caused by hydro-meteorological variability along with correlations among different indicators (ammonium nitrogen, NH3-N; and total phosphorus, TP) and BMPs. The coupled model was applied to evaluate the multi-indicator effect of individual BMP and combined effect of various BMPs in the upper Boyang River basin, China. Results showed that bivariate copulas and three-dimensional vine copulas can efficaciously describe the dependence of BMPs effects. Simulation results indicate 43–100% probabilities of 45% NH3-N loads reduction, while 0–79% probabilities of 45% TP loads reduction for combined BMPs scenarios. Besides, the joint probabilities of different indicators in combined BMPs scenarios are generally lower than separate probabilities with 0–21% decrease, which is similar to individual BMP. Generally, joint probabilities using copulas can provide more accurate and factual knowledge of the risk and dependability of implementation of BMPs than univariate variables. The proposed model can conduct multivariate analysis of BMPs reduction effects and has great prospect in the future risk-based decision-making of NPS pollution management.

Assessing the effectiveness of potential best management practices for science-informed decision support at the watershed scale: The case of the Mar Menor coastal lagoon, Spain

Coastal lagoons are ecosystems of high environmental importance but are quite vulnerable to human activities. The continuous inflow of pollutant loads can trigger negative impacts on the ecological status of these water bodies, which is contrary to the European Green Deal. One example is the Mar Menor coastal lagoon in Spain, which has experienced significant environmental degradation in recent years due to excessive external nutrient input, especially from non-point source (NPS) pollution. Mar Menor is one of the largest coastal lagoons of the Mediterranean region and a site of great ecological and socio-economic value. In this study, the highly anthropogenic and complex watershed of Mar Menor, known as Campo de Cartagena (1244 km2), was modelled with the Soil and Water Assessment Tool (SWAT) to analyse potential options for recovery of this unique system. The model was used to simulate several best management practices (BMP) proposed by recent Mar Menor regulations, such as vegetative filter strips, shoreline buffers, contour farming, removal of illegal agriculture, crop rotation management, waterway vegetation restoration, fertiliser management and greenhouse rainwater harvesting. Sixteen scenarios of individual and combined BMPs were analysed in this study. We found that, as individual measures, vegetative filter strips and contour farming were most effective in nutrient reduction: approximately 30 % for total nitrogen (TN) and 40 % for total phosphorus (TP). Moreover, waterway vegetation restoration showed the highest sediment (S) reduction at approximately 20 %. However, the combination of BMPs demonstrated clear synergistic effects, reducing S export by 38 %, TN by 67 %, and TP by 75 %. Selecting the most appropriate BMPs to be implemented at a watershed scale requires a holistic approach considering effectiveness in reducing NPS pollution loads and BMP implementation costs. Thus, we have demonstrated a way forward for enabling science-informed decision-making when choosing strategies to control NPS contamination at the watershed scale.

Assessment of Best Management Practices on Hydrology and Sediment Yield at Watershed Scale in Mississippi Using SWAT

The selection and execution of appropriate best management practices (BMPs) in critical areas of a watershed can effectively reduce sediment yield. Objectives of this research include developing a watershed-scale Soil and Water Assessment Tool (SWAT) model for the Big Sunflower River Watershed (BSRW), identifying high sediment yield areas using calibrated and validated model, and assessing the effects of various BMPs. The efficiency of three BMPs, grassed waterways (GWW), vegetative filter strips (VFS), and grade stabilization structures (GSS), and their combinations in reducing sediment yield, were investigated. The model performed well for streamflow (P-factor = 0.72–0.87; R-factor = 0.74–1.27; R2 = 0.60–0.86; NSE = 0.60–0.86) and total suspended solids (TSS) (P-factor = 0.56–0.89; R-factor = 0.43–2.83; R2 = 0.62–0.91; NSE = 0.38–0.91) during calibration and validation. The simulation of individual BMPs revealed that GWW showed the highest sediment yield reduction (up to 44%), followed by VFS (up to 38%) and GSS (up to 7%). Two BMPs’ combinations showed that GSS and GWW had the largest sediment yield reduction potential (up to 47%) while VFS and GSS had the lowest potential (up to 42%). Similarly, a combination of all three BMPs reduced the sediment yield up to 50%. The findings of this study will aid in sustainable watershed management and will be valuable for watershed managers and planners.

Evaluation of Best Management Practices for non-point source pollution based on the SWAT model in the Hanjiang River Basin, China

Abstract Taking the Hanjiang River Basin with the Ankang hydrological station as the control section and as the study area, the Soil and Water Assessment Tool (SWAT) model was used to identify the spatial and temporal distribution of non-point source (NPS) pollution and determine the critical source areas (CSA). We set up 11 Best Management Practices (BMPs) in the CSA and evaluated their environmental and comprehensive benefits. The results showed that TN and TP loads in flood season were significantly higher than that in the non-flood season. The distribution of loss intensity of TN and TP load has a strong correlation with runoff and sediment erosion intensity, respectively. Among the eight individual BMPs, the reduction rates of stubble coverage, grassed waterway and returning farmland to forest land were relatively high, and the comprehensive attribute value Z of stubble coverage was the highest. Among the three combined BMPs, the reduction rate of ‘stubble coverage + grassed waterway + returning farmland to forest land (>25°)’ was the highest and the Z value was the largest. Overall, the BMPs such as stubble coverage, grassed waterway, and returning farmland to forest land can be adopted alternately to control NPS pollution in the Hanjiang River Basin.

Evaluating the Effectiveness of Best Management Practices On Soil Erosion Reduction Using the SWAT Model: for the Case of Gumara Watershed, Abbay (Upper Blue Nile) Basin

This study was conducted to evaluate the effectiveness of best management practices (BMPs) to reduce soil erosion in Gumara watershed of the Abbay (Upper Blue Nile) Basin using the Soil and Water Assessment Tool (SWAT) model. The model was calibrated (1995-2002) and validated (2003-2007) using the SWAT-CUP based on observed streamflow and sediment yield data at the watershed outlet. The study evaluated four individual BMP Scenarios; namely, filter strips (FS), stone/soil bunds (SSB), grassed waterways (GW) and reforestation of croplands (RC), and three blended BMP Scenarios, which combines individual BMPS of FS and RC (FS & RC), GW and RC (GW & RC), and SSB and GW (SSB & GW). Mean annual sediment yield at the baseline conditions was estimated at 19.7 t ha-1yr-1, which was reduced by 13.7, 30.5, 16.2 and 25.9% in the FS, SSB, GW, and RC Scenarios, respectively at the watershed scale. The highest reduction efficiency of 34% was achieved through the implementations of the SSB & GW Scenario. The GW & RC, and FS & RC Scenarios reduced the baseline sediment yield by 32% and 29.9%, respectively. The study therefore concluded that the combined Scenarios mainly SSB & GW, and GW & RC can be applied to reduce the high soil erosion in the Gumera watershed, and similar agro-ecological watersheds in Ethiopia. In cases where applying the combined scenarios is not possible, the SSB Scenario can yield significant soil erosion reduction.

Evaluating nitrate and phosphorus remediation in intensively irrigated stream-aquifer systems using a coupled flow and reactive transport model

In irrigated semi-arid watersheds, over-fertilization often leads to nitrogen (N) and phosphorus (P) contamination in aquifers and river systems. Modelling tools often are used to evaluate the effect of management practices on nutrient contamination levels. In this study, we assess a suite of best management practices (BMPs) for N and P in a regional irrigated stream-aquifer system using a new numerical model. As it is necessary to consider the interaction of flow in the stream and aquifer, SWAT-MODFLOW model that couples surface and groundwater flow was used. The reactive processes were modelled using RT3D that simulate the reactive groundwater transport. The model is based on the coupled flow model SWAT-MODFLOW, with the groundwater reactive transport model RT3D included to simulate the reactive groundwater transport of NO3 and soluble P and their interactions within the soil-aquifer-stream system. The assessment is performed for a highly managed 732 km2 region in the Lower Arkansas River Valley (south-eastern Colorado), with model results compared to observed groundwater nutrient concentration, in-stream nutrient concentration and loading, and crop yield. A total of 28 BMPs scenarios are evaluated regarding their impact on NO3 and soluble P contamination in the aquifer and river system. The most effective individual BMP in most areas is to decrease fertilizer by 30%, resulting in NO3 and soluble P reduced by 20% and 2% for groundwater concentrations, 25% and 10% for river concentrations, and 27% and 6% for mass loadings into surface water, respectively. Combinations of using 30% irrigation reduction, 30% fertilization reduction, 60% canal seepage reduction, and conservation tillage yield the greatest overall impact to lower NO3 and soluble P concentrations up to 41% and 8% in groundwater, 52% and 40% in river, and 63% and 49% for mass loadings. Targeting BMPs on localized problem areas shows great promise in reducing contamination while maintaining region-wide crop yield. The study demonstrates the SWAT-MODFLOW-RT3D modelling code is a useful tool to examine NO3 and P transport and quantify BMP effects in groundwater-driven watersheds.

Modeling and Prioritizing Interventions Using Pollution Hotspots for Reducing Nutrients, Atrazine and E. coli Concentrations in a Watershed

Excess nutrients and herbicides remain two major causes of waterbody impairment globally. In an attempt to better understand pollutant sources in the Big Sandy Creek Watershed (BSCW) and the prospects for successful remediation, a program was initiated to assist agricultural producers with the implementation of best management practices (BMPs). The objectives were to (1) simulate BMPs within hotspots to determine reductions in pollutant loads and (2) to determine if water-quality standards are met at the watershed outlet. Regression-based load estimator (LOADEST) was used for determining sediment, nutrient and atrazine loads, while artificial neural networks (ANN) were used for determining E. coli concentrations. With respect to reducing sediment, total nitrogen and total phosphorus loads at hotspots with individual BMPs, implementing grassed waterways resulted in average reductions of 97%, 53% and 65% respectively if implemented all over the hotspots. Although reducing atrazine application rate by 50% in all hotspots was the most effective BMP for reducing atrazine concentrations (21%) at the gauging station 06883940, this reduction was still six times higher than the target concentration. Similarly, with grassed waterways established in all hotspots, the 64% reduction in E. coli concentration was not enough to meet the target at the gauging station. With scaled-down acreage based on the proposed implementation plan, filter strip led to more pollutant reductions at the targeted hotspots. Overall, a combination of filter strip, grassed waterway and atrazine rate reduction will most likely yield measureable improvement both in the hotspots (>20% reduction in sediment, total nitrogen and total phosphorus pollution) and at the gauging station. Despite the model’s uncertainties, the results showed a possibility of using Soil and Water Assessment Tool (SWAT) to assess the effectiveness of various BMPs in agricultural watersheds.

Identification of critical areas and evaluation of best management practices using SWAT for sustainable watershed management

Identification of critical erosion-prone areas and selection of best management practices (BMPs) for watersheds are necessary to control their degradation by reducing sediment yields. The current research assesses and proposes a combination of potential BMPs for the Baitarani catchment in India using the Soil and Water Assessment Tool (SWAT). After the successful calibration and validation of the SWAT model developed for this catchment, the model was applied to evaluate the efficacy of eight agricultural and structural management practices and their combinations (three scenarios) for controlling sediment yields at watershed and sub-watershed levels as well as to assess the impacts of combined BMPs on water balance components. A combination of BMPs was found more effective in reducing sediment yields than individual BMPs. Comparative evaluation revealed that structural BMPs (0.66–70%) are better than agricultural BMPs (2–7%) in minimizing sediment yields at watershed level. The costly measures like grade and streambank stabilization structures can reduce the sediment yield up to 70% at the watershed level. The modeling results of the impacts of different combinations of BMPs (three scenarios) indicated that if all the eight BMPs are implemented, the reduction of sediment yields is increased by 76% and 80% at sub-watershed and watershed levels, respectively compared to the Base Scenario. Based on funds availability, a suitable combination of BMPs can be adopted by the concerned decision-makers to effectively reduce sediment yields in the study area. Further, the simulation results of BMPs impacts on water balance components revealed that the annual average surface runoff reduces by 4–14% in the three scenarios, while aquifer recharge (6.8–8.7%), baseflow (8–10.5%), and percolation (1.2–3.9%) increase due to implementation of BMPs. Overall, the findings of this study are very useful for ensuring sustainable management of land and other resources at a catchment scale.

Addressing the spatial disconnect between national-scale total maximum daily loads and localized land management decisions.

Regulatory watershed mitigation programs typically emphasize widespread adoption of best management practices (BMPs) to meet total maximum daily load (TMDL) goals. To comply with the Chesapeake Bay TMDL, jurisdictions must develop watershed implementation plans (WIPs) to determine the number and type of BMPs to implement. However, the spatial resolution of the bay‐level model used to determine these load reduction goals is so coarse that the regulatory plan cannot consider heterogeneity in local conditions, which affects BMP effectiveness. Using the Topo‐SWAT modification of the Soil and Water Assessment Tool (SWAT), we simulated two BMP adoption scenarios in the Spring Creek watershed in central Pennsylvania to determine if leveraging fine‐scale spatial heterogeneity to place BMPs could achieve the same (or better) nutrient and sediment reduction at a lower cost than the state‐level WIP BMP adoption recommendations. Topo‐SWAT was initialized with detailed land use and management practice information, systematically calibrated, and validated against 12 yr of observed data. After determining individual BMP cost effectiveness, results were ranked to design a cost‐effective BMP adoption scenario that achieved equal or greater load reduction as the WIP scenario for 74% of the cost using eight management‐based BMPs: no‐till, manure injection, cover cropping, riparian buffers, land retirement, manure application timing, wetland restoration, and nitrogen management (15% less N input). Because watersheds of this size typically represent the smallest modeling unit in the Chesapeake Bay Model, results demonstrate the potential to use watershed models with finer inference scales to improve recommendations for BMP implementation under the Chesapeake Bay TMDL.

Validation of Nursery and Greenhouse Best Management Practices through Scientific Evidence

Nursery and greenhouse growers use a variety of practices known as best management practices (BMPs) to reduce sediment, nutrient, and water losses from production beds and to improve efficiency. Although these BMPs are almost universally recommended in guidance manuals, or required by regulation in limited instances, little information is available that links specific BMPs to the scientific literature that supports their use and quantifies their effectiveness. A previous survey identified the most widely used water management, runoff, and fertilizer-related BMPs by Virginia nursery and greenhouse operators. Applicable literature was reviewed herein and assessed for factors that influence the efficacy of selected BMPs and metrics of BMP effectiveness, such as reduced water use and fertilizers to reduce sediment, nitrogen (N), and phosphorus (P) loads in runoff. BMPs investigated included vegetative zones (VZs), irrigation management strategies, and controlled-release fertilizers (CRFs). Use of vegetative buffers decreased average runoff N 41%, P 67%, and total suspended solids 91%. Nitrogen, P, and sediment removal efficacy increased with vegetative buffer width. Changes in production practices increased water application efficiency >20% and decreased leachate or runoff volume >40%, reducing average N and P loss by 28% and 14%, respectively. By linking BMPs to scientific articles and reports, individual BMPs can be validated and are thus legitimized from the perspective of growers and environmental regulators. With current and impending water use and runoff regulations, validating the use and performance of these BMPs could lead to increased adoption, helping growers to receive credit for actions that have been or will be taken, thus minimizing water use, nutrient loss, and potential pollution from nursery and greenhouse production sites.

Evaluating efficiencies and cost-effectiveness of best management practices in improving agricultural water quality using integrated SWAT and cost evaluation tool

Agricultural conservation practices, or agricultural best management practices (BMPs), can reduce nutrient loading and help address harmful algal blooms (HABs). HABs in the western basin of Lake Erie, which are largely caused by phosphorus losses from the Maumee River watershed, are critical in the recent years. In this study, a new BMP cost tool was developed. Then the Soil and Water Assessment Tool (SWAT) and the new BMP cost tool were integrated to explore efficiencies and cost-effectiveness of BMPs in an agricultural catchment of the Maumee River watershed with various scenarios. The scenarios included individual BMPs applied in 100% of suitable areas, individual BMPs targeting Dissolved Reactive Phosphorus (DRP) and Total Phosphorus (TP) critical areas, and BMPs implemented in series. In addition, a cost-effective approach for the selections and placements of BMPs in agricultural watersheds was developed as an alternative to running complex optimization tools that are not applicable to large watersheds. The cost-effective approach applied BMPs based on cost-effectiveness rankings starting from the most cost-effective one. Results showed that: (1) BMPs implemented in series, which reduced pollutant loads more than individual BMPs, were not as cost-effective as some individual BMPs; (2) among all scenarios, filter strips targeting DRP/TP critical areas were the most cost-effective in reducing yearly/spring DRP/TP losses; (3) to obtain the watershed management plan goal of reducing March-July DRP/TP losses by 40%, implementing BMPs one by one in critical areas based on the cost-effectiveness rankings of individual BMPs in DRP/TP critical areas was the most cost-effective; and (4) the simulation results, modeling tools, and cost-effective approach can help create agricultural BMP strategies to cost-efficiently improve water quality.

Performance of low-impact development best management practices: a critical review

Low-impact development (LID), a land planning and engineering design approach for managing urban stormwater runoff, has been widely adopted across the globe. LID best management practices (BMPs) are man-made features that rely on natural processes to manage stormwater water quantity and quality. In this article, recent literature (published after the year 2008) related to nine BMPs was reviewed to highlight the ranges in treatment efficiencies for 21 of the most frequently investigated runoff parameters. The primary function, pros and cons, and factors affecting performance of each BMP were discussed. A frequency analysis of the reviewed parameters showed that total suspended solids, total phosphorous, total nitrogen, runoff reduction, and zinc concentrations were the most frequently investigated stormwater runoff parameters. Five recurring themes were observed with regards to knowledge gaps and conflicting objectives for research related to LID BMPs that include: (i) lack of consensus on which parameters to measure for effective LID adoption, (ii) BMP performance is highly variable, (iii) many BMPs are known exporters of nutrient pollutants, (iv) lack of cold weather performance-specific studies for individual BMPs, and (v) lack of human pathogen-related stormwater quality studies for individual BMPs. Suggestions for future research are discussed to address these knowledge gaps.

Effects of Different Spatial Configuration Units for the Spatial Optimization of Watershed Best Management Practice Scenarios

Different spatial configurations (or scenarios) of multiple best management practices (BMPs) at the watershed scale may have significantly different environmental effectiveness, economic efficiency, and practicality for integrated watershed management. Several types of spatial configuration units, which have resulted from the spatial discretization of a watershed at different levels and used to allocate BMPs spatially to form an individual BMP scenario, have been proposed for BMP scenarios optimization, such as the hydrologic response unit (HRU) etc. However, a comparison among the main types of spatial configuration units for BMP scenarios optimization based on the same one watershed model for an area is still lacking. This paper investigated and compared the effects of four main types of spatial configuration units for BMP scenarios optimization, i.e., HRUs, spatially explicit HRUs, hydrologically connected fields, and slope position units (i.e., landform positions at hillslope scale). The BMP scenarios optimization was conducted based on a fully distributed watershed modeling framework named the Spatially Explicit Integrated Modeling System (SEIMS) and an intelligent optimization algorithm (i.e., NSGA-II, short for Non-dominated Sorting Genetic Algorithm II). Different kinds of expert knowledge were considered during the BMP scenarios optimization, including without any knowledge used, using knowledge on suitable landuse types/slope positions of individual BMPs, knowledge of upstream–downstream relationships, and knowledge on the spatial relationships between BMPs and spatial positions along the hillslope. The results showed that the more expert knowledge considered, the better the comprehensive cost-effectiveness and practicality of the optimized BMP scenarios, and the better the optimizing efficiency. Thus, the spatial configuration units that support the representation of expert knowledge on the spatial relationships between BMPs and spatial positions (i.e., hydrologically connected fields and slope position units) are considered to be the most effective spatial configuration units for BMP scenarios optimization, especially when slope position units are adopted together with knowledge on the spatial relationships between BMPs and slope positions along a hillslope.

Analysis of the efficacy and cost-effectiveness of best management practices for controlling sediment yield: A case study of the Joumine watershed, Tunisia

Soil erosion can be reduced through the strategic selection and placement of best management practices (BMPs) in critical source areas (CSAs). In the present study, the Soil Water Assessment Tool (SWAT) model was used to identify CSAs and investigate the effectiveness of different BMPs in reducing sediment yield in the Joumine watershed, an agricultural river catchment located in northern Tunisia. A cost-benefit analysis (CBA) was used to evaluate the cost-effectiveness of different BMP scenarios. The objective of the present study was to determine the most cost-effective management scenario for controlling sediment yield. The model performance for the simulation of streamflow and sediment yield at the outlet of the Joumine watershed was good and satisfactory, respectively. The model indicated that most of the sediment was originated from the cultivated upland area. About 34% of the catchment area consisted of CSAs that were affected by high to very high soil erosion risk (sediment yield >10t/ha/year). Contour ridges were found to be the most effective individual BMP in terms of sediment yield reduction. At the watershed level, implementing contour ridges in the CSAs reduced sediment yield by 59%. Combinations of BMP scenarios were more cost-effective than the contour ridges alone. Combining buffer strips (5-m width) with other BMPs depending on land slope (> 20% slope: conversion to olive orchards; 10–20% slope: contour ridges; 5–10% slope: grass strip cropping) was the most effective approach in terms of sediment yield reduction and economic benefits. This approach reduced sediment yield by 61.84% with a benefit/cost ratio of 1.61. Compared with the cost of dredging, BMPs were more cost-effective for reducing sediment loads to the Joumine reservoir, located downstream of the catchment. Our findings may contribute to ensure the sustainability of future conservation programs in Tunisian regions.

Evaluation of the best management practices in a semi-arid region with high agricultural activity

The arid and semi-arid regions with water scarcity are vulnerable to several stressors such as urbanization, high water demand created by agricultural and industrial activities, point and non-point pollution sources, and climate change. Hence, proactive policies and sustainable water management strategies that are based on decision support systems are crucial in arid and semi-arid regions. Because of large expenses and implementation difficulties associated with the diffuse pollution abatement plans, many authorities are hesitant to initiate, especially those that may present a financial burden on population. Lake Mogan, a shallow lake, is located in a semi-arid region dominated by dry agricultural activities and has been in eutrophic state for the past 20 years. There has been several management alternatives suggested to improve the water quality in Lake Mogan and one of the alternative is the application of BMPs that include fertilizer management, conservation/no tillage, contouring, and terracing to reduce the amount of diffuse source pollutants. In this study, Soil and Water Assessment Tool (SWAT) Model is applied to evaluate the effectiveness of agricultural best management practices (BMPs) in the Lake Mogan watershed located in a semi-arid region. The most effective BMP scenario was found as the one in which three individual BMP scenarios (30% fertilizer reduction, no tillage, and terracing) were combined. With this scenario average annual load reductions of 9.3%, 8.6%, 8.0%, and 11.1% were achieved in sediment, nitrate, total nitrogen, and total phosphorus, respectively. Even with the most effective BMP strategy, high levels of nutrient reduction will not be achieved since non-irrigated agriculture and intermittent low-flow streams accounts majority of the study area. The outcomes suggest integrated solutions should be developed to improve water quality in Lake Mogan. It is aimed that this study will aid decision makers to implement effective best management practices in watersheds showing similar characteristics (i.e. topographical, hydrologic processes, LULC (Land use land cover) characteristics, agricultural activities, meteorological etc.) with the study area.

National status of state developed and implemented forestry best management practices for protecting water quality in the United States

United States forestry best management practices (BMPs) were developed by U.S. states to protect water quality while enhancing the sustainability of forest management activities. Forestry BMPs are revised over time or new BMPs are written to meet current water quality standards. Properly implemented forestry BMPs have been found to minimize the impact of erosion and sediment that may occur during forest management activities. States developed implementation strategies to help determine if BMPs are being implemented correctly; however, these strategies can vary between regions and states making implementation results difficult to interpret. Few studies have compared monitoring strategies and implementation of BMPs on a national level. This study surveyed and received responses from state forestry agencies in all 50 states. Each state reported a documented BMP manual. Twenty states reported non-regulatory BMP guidelines, 19 reported quasi-regulatory BMP guidelines, and 11 reported regulatory BMP guidelines. Thirty-nine states have BMP monitoring programs with the state forestry agency as the lead agency in 35 states. BMP effectiveness studies were reported in 33 states with 19 states reporting current or future effectiveness studies. Thirty-two states reported that they have conducted BMP implementation studies resulting in a mean national BMP implementation rate of 91%. However, when evaluating implementation of individual BMP categories, the survey indicated potential deficiencies for some states, yet these states’ overall BMP implementation rate appear to be satisfactory. There was no significant difference between non-regulatory, quasi-regulatory, and regulatory BMP guidelines when compared by mean state BMP implementation rates (90.2%, 90.2%, and 93.4%, respectively). Mean BMP implementation rates for the western (93.2%) and southeastern (92.4%) regions were significantly higher than the northeastern region (86.4%). This assessment of state BMP programs indicates that BMP programs appear to be implemented at relatively high levels across the U.S. These findings should be useful globally for agency managers to improve program effectiveness and better understand BMP implementation and program structure among 50 diverse states.

Evaluation of distributed BMPs in an urban watershed—High resolution modeling for stormwater management

AbstractThe urban environment modifies the hydrologic cycle resulting in increased runoff rates, volumes, and peak flows. Green infrastructure, which uses best management practices (BMPs), is a natural system approach used to mitigate the impacts of urbanization onto stormwater runoff. Patterns of stormwater runoff from urban environments are complex, and it is unclear how efficiently green infrastructure will improve the urban water cycle. These challenges arise from issues of scale, the merits of BMPs depend on changes to small‐scale hydrologic processes aggregated up from the neighborhood to the urban watershed. Here, we use a hyper‐resolution (1 m), physically based hydrologic model of the urban hydrologic cycle with explicit inclusion of the built environment. This model represents the changes to hydrology at the BMP scale (~1 m) and represents each individual BMP explicitly to represent response over the urban watershed. Our study varies both the percentage of BMP emplacement and their spatial location for storm events of increasing intensity in an urban watershed. We develop a metric of effectiveness that indicates a nonlinear relationship that is seen between percent BMP emplacement and storm intensity. Results indicate that BMP effectiveness varies with spatial location and that type and emplacement within the urban watershed may be more important than overall percent.