Application Of Soil And Water Assessment Tool Research Articles

Integrated Application of SWAT and L-THIA Models for Nonpoint Source Pollution Assessment in Data Scarce Regions

Nonpoint source pollution (NPS) has become the most important reason for the deterioration of water quality, while relevant studies are often limited to African river and lake basins with insufficient data. Taking the Simiyu catchment of the Lake Victoria basin as the study area, we set up a NPS model based on the soil and water assessment tool (SWAT). Furthermore, the rationality of this model is verified with the field-measured data. The results manifest that: (1) the temporal variation of NPS load is consistent with the variation pattern of rainfall, the average monthly output of total nitrogen (TN) and total phosphorus (TP) in the rainy season was 1360.6 t and 336.2 t, respectively, while in the dry season was much lower, only 13.5 t and 3.0 t, respectively; (2) in view of spatial distribution among 32 sub-basins, TN load ranged from 2.051 to 24.288 kg/ha with an average load of 12.940 kg/ha, and TP load ranged from 0.263 to 8.103 kg/ha with an average load of 3.321 kg/ha during the 16-month study period; (3) Among the land use types, the cropland contributed the highest proportion of TN and TP pollution with 50.28% and 76.29%, respectively, while the effect of forest on NPS was minimal with 0.05% and 0.02% for TN and TP, respectively. (4) Moreover, the event mean concentration (EMC) values of different land use types have been derived based on the SWAT model, which are key parameters for the application of the long-term hydrological impact assessment (L-THIA) model. Therefore, this study facilitates applying the L-THIA model to other similar data-deficient catchments in view of its relatively lower data requirement.

Assessing Climate Change and Water Resource Management Worldwide with the SWAT Model: A Comprehensive Review

Utilized the Soil and Water Assessment Tool (SWAT) across different watershed scales, from small to large, under a variety of climate conditions, aiming to quantify and mitigate the impacts of climate change on watershed hydrology and water resources. Additionally, the paper explores the development of conservation strategies for water and soil, aimed at managing both water and sediment yields effectively. By examining research at international, national, and regional levels, with a particular focus on climate change projections for Morocco, this review critically assesses the SWAT model’s operational framework, including its inputs and outputs. The operational intricacies of the SWAT model are dissected to understand its utility in hydrological modeling, emphasizing its role in climate change assessment. Through this examination, the paper highlights the expanding application of SWAT in water resource assessments globally, demonstrating its significance in understanding and addressing the challenges posed by climate change on hydrological systems worldwide.

Using the Soil and Water Assessment Tool (SWAT) to quantify the economic value of ecosystem services

AbstractModeling tools simulate the functioning of ecosystems and their interactions with human activities, helping decision makers understand how interventions impact ecosystems and evaluate management strategies. This leads to informed decisions that balance human development and environmental protection. Among these models, Soil and Water Assessment Tool (SWAT) stands out for its ability to simulate multiple biophysical processes that can be linked to the provision of ecosystem services (ES). Although SWAT has been successfully applied for the evaluation of ES, the development of complementary approaches that translate the results of SWAT into monetary terms is still in its early stages. To narrow this gap, this review article aims to provide a comprehensive assessment of the literature on the relationship between SWAT model results and economic analysis. Specifically, the review summarizes the research conducted on the use of SWAT model results to estimate economic values, including the different methodologies used and the types of economic values estimated. The review will also discuss the limitations and challenges of these approaches, provide a critical evaluation of the strengths and weaknesses of the research in this area, and provide recommendations to strengthen SWAT application for the economic evaluation of management strategies.

A generalized reservoir module for SWAT applications in watersheds regulated by reservoirs

Accurate estimates of reservoir outflow are important for simulating runoff of watersheds regulated by large reservoirs using hydrological models. The target release reservoir module widely used in the Soil and Water Assessment Tool (SWAT) shows poor performance in simulating the outflow and water level of large multipurpose reservoirs. In this study, a generalized reservoir operation chart-based reservoir module is developed as an alternative to the original reservoir module in SWAT (SWAT-Or). The proposed reservoir module includes a dynamic decision-based outflow framework integrated into the operation chart. The modified version of SWAT with the new reservoir module (SWAT-M) is not only suite for small reservoir with flood control function but also more applicable to large multipurpose reservoir. The predictions obtained from the original and new reservoir modules are compared with measured data from the three largest reservoirs in the Dongjiang River basin, South China. The performance of SWAT-M and SWAT-OR for daily and monthly runoff simulations of four hydrological stations in the basin are compared. The results shows that the proposed module produces results closer to the field measurements and has fewer errors than the original module, which predicts inappropriate low reservoir outflow during dry periods. In addition, the runoff simulation by SWAT-M shows a significant improvement, in particular for stations directly influenced by large reservoirs. The monthly (daily) scale R2 of SWAT-M is 0.02 to 0.21 (0.14 to 0.44) higher, and the NSE is 0.11 to 0.30 (0.12 to 7.16) higher than that of SWAT-Or. The proposed reservoir operation chart-based module significantly improves the applicability of SWAT to simulate runoff in watersheds regulated by large reservoirs.

Simulation of rice paddy systems in SWAT: A review of previous applications and proposed SWAT+ rice paddy module

The Soil and Water Assessment Tool (SWAT) is an ecohydrological watershed-scale model which was initially developed in the early 1990s to simulate the impacts of land use, management systems, and climate on hydrology and/or water quality. First adopted in the U.S., the use of the model then spread to Europe and then later to Asia and other regions. The range of applications that SWAT has been applied to have also expanded dramatically, which influenced ongoing model development which has been virtually continuous over the past two decades. A key component of many SWAT applications in Asia is accounting for rice paddy production that is common in some subregions within the continent. However, most of these studies do not provide explicit details of how rice production was simulated in SWAT. Other research has revealed that significant problems occur when trying to represent rice paddy systems in standard versions of SWAT, due to limitations in algorithms based on the runoff curve number approach or the pothole option. In response, key modifications have been made to SWAT in recent studies that have resulted in a more accurate representation of rice paddy systems. These developments point to the need for the incorporation of an enhanced rice paddy module within SWAT to better capture rice paddy hydrological and pollutant dynamics, which would support improved use of the model in Asia and other rice production regions. Subtopics related to simulating rice production in SWAT are discussed as follows: 1) an overview of global rice production; 2) history of SWAT development; 3) typical approaches for simulating rice production; 4) problems associated with the typical approaches; 5) recent code modifications to address deficiencies in replicating rice paddy systems; 6) recommendations for developing a standard rice paddy module for future SWAT codes. Keywords: SWAT, rice paddies, potholes, hydrology, pollutants, modified SWAT models DOI: 10.25165/j.ijabe.20221501.7147 Citation: Gassman P W, Jeong J, Boulange J, Narasimhan B, Kato T, Somura H, et al. Simulation of rice paddy systems in SWAT: A review of previous applications and proposed SWAT+ rice paddy module. Int J Agric & Biol Eng, 2022; 15(1): 1–24.

Applications of the SWAT Model for Coastal Watersheds: Review and Recommendations

HighlightsA systematic review was performed of SWAT applications in coastal watersheds.Three percent of SWAT applications have occurred in coastal watersheds.SWAT performed better at a monthly time step versus a daily time step.Nash-Sutcliffe efficiency (NSE) was the most common metric used for evaluating simulations.More research should be conducted on coupling SWAT with hydrodynamic models in tidal systems.Abstract. The Soil and Water Assessment Tool (SWAT) is a watershed to river basin scale model widely used to simulate the quality and quantity of surface water and groundwater. SWAT has been applied in a wide variety of geographical landscapes around the world. This review presents a comprehensive summary of SWAT applications for coastal watersheds. Thirty-four articles were identified as coastal applications of SWAT, which account for 3% of the total published studies using SWAT. Nash-Sutcliffe efficiency (NSE) was the most common metric used to evaluate SWAT simulations. The SWAT model calibration and validation studies in coastal watersheds reported higher NSE values for monthly flow simulation (NSE up to 0.95) than for daily flow simulation (NSE up to 0.89). Among all the studies, 34% of the reported NSE values (flow and water quality combined) were >0.75. The majority (58%) of flow values were reported daily, while the majority (81%) of water quality values were reported monthly. Only two studies combined SWAT with a hydrodynamic model to account for tide-storm surge processes. SWAT may be applied more readily and successfully to coastal watersheds if a user-friendly method is developed for coupling SWAT with hydrodynamic models to simulate the tidal influence. Keywords: Bay, Coast, Estuary, Gulf, Hydrologic model, Soil and Water Assessment Tool, Water quality model, Watershed model.

Integrated watershed development plan for a sub-basin, central India

Abstract The present study aims to propose an integrated watershed development plan for the Wainganga basin situated in Maharashtra, India. Also, the study involves evaluating the performance and applicability of SWAT (Soil and Water Assessment Tool) as a runoff model along with the trend analysis of rainfall for the above mentioned study area. The decadal land-use/land-cover (LULC) variation from 1985 to 2005 has been studied using data procured from Goddard Earth Sciences Data and Information Services Center (GES-DISC) and the groundwater table level of the study area was monitored using dug/bore well data collected from the Central Ground Water Board (CGWB). Rainfall trend analysis for a period of 101 years using historic rainfall data procured from the India Meteorological Department (IMD) has been analyzed to foresee the future scenario. It was observed that the rainfall-runoff relationship of the area is getting affected by the LULC variation and is thereby affecting the groundwater regime. There is a significant deterioration in the forest cover and water bodies which is alarming. The study devises the importance of an immediate master plan to be implemented in the basin to avoid any future crisis. Also, the study emphasizes the advancement of remote sensing in the use of hydrologic models like SWAT more realistically.

SWAT Application for Gajahwong River Streamflow Simulation

Gadjahwong River flows along Daerah Istimewa Yogyakarta (DIY) that is located in southern Java Island. Gadjahwong River has an important role for water supply purpose especially for agriculture activities. On the other hand, DIY is seeing 1.18% population growth each year. The population surge influences land cover change that can seize continuous discharge of Gadjahwong River. Therefore, continuous discharge simulation needs to be conducted for assessing Gadjahwong River water availability. Soil and Water Assessment Tool (SWAT) was employed for modelling Gadjahwong River streamflow discharge. The simulation result discharge was compared with observed data acquired at AWLR Wonokromo by using NSE and R2 statistical parameter. Finally, the statistical parameter was applied to justify quality of simulation. Findings showed that daily time step yielded NSE value of 0.61, R2 value of 0.79, and PBIAS value of -2.41%. Overall, the simulation showed good result based the statistical parameters.

Application of SWAT in Hydrological Simulation of Complex Mountainous River Basin (Part II: Climate Change Impact Assessment)

This study aims at analysing the impact of climate change (CC) on the river hydrology of a complex mountainous river basin—the Budhigandaki River Basin (BRB)—using the Soil and Water Assessment Tool (SWAT) hydrological model that was calibrated and validated in Part I of this research. A relatively new approach of selecting global climate models (GCMs) for each of the two selected RCPs, 4.5 (stabilization scenario) and 8.5 (high emission scenario), representing four extreme cases (warm-wet, cold-wet, warm-dry, and cold-dry conditions), was applied. Future climate data was bias corrected using a quantile mapping method. The bias-corrected GCM data were forced into the SWAT model one at a time to simulate the future flows of BRB for three 30-year time windows: Immediate Future (2021–2050), Mid Future (2046–2075), and Far Future (2070–2099). The projected flows were compared with the corresponding monthly, seasonal, annual, and fractional differences of extreme flows of the simulated baseline period (1983–2012). The results showed that future long-term average annual flows are expected to increase in all climatic conditions for both RCPs compared to the baseline. The range of predicted changes in future monthly, seasonal, and annual flows shows high uncertainty. The comparative frequency analysis of the annual one-day-maximum and -minimum flows shows increased high flows and decreased low flows in the future. These results imply the necessity for design modifications in hydraulic structures as well as the preference of storage over run-of-river water resources development projects in the study basin from the perspective of climate resilience.

Application of SWAT in Hydrological Simulation of Complex Mountainous River Basin (Part I: Model Development)

The soil and water assessment tool (SWAT) hydrological model has been used extensively by the scientific community to simulate varying hydro-climatic conditions and geo-physical environment. This study used SWAT to characterize the rainfall-runoff behaviour of a complex mountainous basin, the Budhigandaki River Basin (BRB), in central Nepal. The specific objectives of this research were to: (i) assess the applicability of SWAT model in data scarce and complex mountainous river basin using well-established performance indicators; and (ii) generate spatially distributed flows and evaluate the water balance at the sub-basin level. The BRB was discretised into 16 sub-basins and 344 hydrological response units (HRUs) and calibration and validation was carried out at Arughat using daily flow data of 20 years and 10 years, respectively. Moreover, this study carried out additional validation at three supplementary points at which the study team collected primary river flow data. Four statistical indicators: Nash–Sutcliffe efficiency (NSE), percent bias (PBIAS), ratio of the root mean square error to the standard deviation of measured data (RSR) and Kling Gupta efficiency (KGE) have been used for the model evaluation. Calibration and validation results rank the model performance as “very good”. This study estimated the mean annual flow at BRB outlet to be 240 m3/s and annual precipitation 1528 mm with distinct seasonal variability. Snowmelt contributes 20% of the total flow at the basin outlet during the pre-monsoon and 8% in the post monsoon period. The 90%, 40% and 10% exceedance flows were calculated to be 39, 126 and 453 m3/s respectively. This study provides additional evidence to the SWAT diaspora of its applicability to simulate the rainfall-runoff characteristics of such a complex mountainous catchment. The findings will be useful for hydrologists and planners in general to utilize the available water rationally in the times to come and particularly, to harness the hydroelectric potential of the basin.

Impacts of swat weather generator statistics from high-resolution datasets on monthly streamflow simulation over Peninsular Spain

Study regionPeninsular Spain. Study focusWeather data are the key drivers of hydrological modelling. However, available weather data can present gaps in data sequences and are often limited in their spatial coverage for use in such hydrological models as the Soil and Water Assessment Tool (SWAT). To overcome this limitation, SWAT includes a weather generator algorithm that can complete this data based on long-term weather statistics. This work presents a newly developed weather statistics dataset for Peninsular Spain (PSWG), calculated from national gridded datasets according to the SWAT model format. PSWG provides a higher resolution that stands as a compelling alternative to the statistics calculated from the Climate Forecast System Reanalysis (CFSR) that are available on the SWAT website. New hydrological insights for the regionThe dataset has been evaluated using PSWG and CFSR datasets for different data availability scenarios to reconstruct weather series in three watersheds with contrasting weather climates. Results underscore the superiority of the PSWG dataset in reconstructing missing data for hydrological simulations. This approach provides a strong alternative for SWAT applications in Peninsular Spain and the applied methodology can be replicated in other countries that dispose of high-resolution gridded rainfall and temperature datasets.

Verifying the applicability of SWAT to simulate fecal contamination for watershed management of Selangor River, Malaysia

The Soil and Water Assessment Tool (SWAT) ecohydrological model was utilized to simulate fecal contamination in the 1937 km2 Selangor River Watershed in Malaysia. The watershed conditions posed considerable challenges owing to data scarcity and tropical climate conditions, which are very different from the original conditions that SWAT was developed and tested for. Insufficient data were compensated by publicly available data (e.g., land cover, soil, and weather) to run SWAT. In addition, field monitoring and interviews clarified representative situations of pollution sources and loads, which were used as input for the model. Model parameters determined by empirical analyses in the USA (e.g., surface runoff, evapotranspiration, and temperature adjustment for bacteria die-off) are thoroughly discussed. In particular, due consideration was given to tropical climate characteristics such as intense rainfall, high potential evapotranspiration, and high temperatures throughout the year. As a result, the developed SWAT successfully simulated fecal contamination ranging several orders of magnitude along with its spatial distribution (i.e., Nash-Sutcliffe Efficiency (NSE) = 0.64, Root Mean Square Error–Observations Standard Deviation Ratio (RSR) = 0.64 at six mainstem sites, and NSE = 0.67 and RSR = 0.57 at 12 major tributaries). Moreover, mitigation countermeasures for future worsening of fecal contamination (i.e., E.coli concentration > 20,000 CFU/100 mL for 690 days during nine years at a raw water intake point for Kuala Lumpur [KL] residents) were analyzed through scenario simulations, thereby contributing to discussing effective watershed management. The results propose improving decentralized sewage treatment systems and treating chicken manure with effective microorganisms in order to guarantee water safety for KL residents (i.e., E.coli concentrations <20,000 CFU/100 mL throughout the period, considering Malaysian standards). Accordingly, this study verified the applicability of SWAT to simulate fecal contamination in areas that are difficult to model and suggests solutions for watershed management based on quantitative evidence.

Influence of Land Use Change on Hydrological Cycle: Application of SWAT to Su-Mi-Huai Area in Beijing, China

The human activities and urbanization process have changed the underlying surface of urban areas, which would affect the recharge of groundwater through rainfall infiltration and may further influence the groundwater environment. Accordingly, it is imperative to investigate the variation of hydrological cycle under the condition of underlying surface change. Based on the high-precision remote sensing data of 2000, 2005, 2010 and 2015, and Soil and Water Assessment Tool (SWAT) model, this work firstly studied the land use change and the corresponding changes in runoff generation mechanism and rainfall infiltration coefficient in Su-Mi-Huai area, Beijing, China. Meanwhile, SWAT-MODFLOW semi-loose coupling model was applied to analyze the water balance in the study area in typical hydrological years. The results showed that the area of the construction land (urban and rural residential land) increased by 1.04 times from 2000 to 2015, which is mainly attributed to the conversion of cultivated land to construction land in the plain area. This change caused the runoff in the area to increase by 7 × 106 m3, the runoff coefficient increased by 17.9%, and the precipitation infiltration coefficient was less than the empirical value determined by lithology. Compared with 2000, the average annual precipitation infiltration coefficient in 2018 decreased by 6.5%. Under the influence of urbanization process, the maximum reduction rate of precipitation infiltration recharge is up to 38%. The study investigated the response of surface runoff and precipitation infiltration recharge to land use change, which can provide helps for water resources managers to coordinate the relationship between land use change and rational water resources planning.

Can-GLWS: Canadian Great Lakes Weather Service for the Soil and Water Assessment Tool (SWAT) modelling

The rapid rise in availability of large geospatial datasets for the development of hydrological models such as Soil and Water Assessment Tool (SWAT) has led to a dramatic increase in both the demand and availability of web services and tools that assist watershed modellers in incorporating data and knowledge into their modelling frameworks. Within the Canadian Great Lakes region, there is a huge potential for the application of SWAT in integrated water resources management. However, a potential barrier is the preparation of SWAT weather inputs that require time-intensive preprocessing of large data sets. Because such preprocessing is reproducible, the redundancy associated with it can be removed by introducing a web service that enables easy and open dissemination of climate data (including climate change and historical data) in SWAT-ready format. This short communication introduces such a web service called the Canadian Great Lakes Weather Data Service for SWAT (Can-GLWS). It hosts observed (historical) and projected (future) daily precipitation, daily maximum/minimum temperature, as well as weather generator database at regular grids (300 arc seconds or ~10 km) for use in SWAT simulations of the region. The novel Can-GLWS web service offers flexibility in selecting the region of interest by allowing them to be uploaded as a shapefile or to draw a rectangle or a polygon. We believe that such data as a service platform will help many practitioners to explore several issues pertaining to the sustainability of the freshwater resources of Canadian Great Lakes using the SWAT model.

Impacts of land-use and climate changes on surface runoff in a tropical forest watershed (Brazil)

ABSTRACT Surface runoff generation capacity can be modified by land-use and climate changes. Annual runoff volumes have been evaluated in a small watershed of tropical forest (Brazil), using the Soil and Water Assessment Tool (SWAT) model. Firstly, the accuracy of SWAT in runoff predictions has been assessed by default input parameters and improved by automatic calibration, using 20-year observations. Then, the hydrological response under land uses (cropland, pasture and deforested soil) alternative to tropical forest and climate change scenarios has been simulated. SWAT application has showed that, if forest was replaced by crops or pasture, the watershed’s hydrological response would not significantly be affected. Conversely, a complete deforestation would slightly increase its runoff generation capacity. Under forecasted climate scenarios, the runoff generation capacity of the watershed will tend to decrease and will not be noticeably different among the representative concentration pathways. Pasture and bare soil will give the lowest and highest runoff coefficients, respectively.

Metaldehyde prediction by integrating existing water industry datasets with the soil and water assessment tool

Metaldehyde (a synthetic aldehyde pesticide used globally in agriculture) has been internationally identified as an emerging contaminant of concern. This study aimed to integrate existing water industry, publicly available and purchased licensed datasets with the open-access Soil and Water Assessment Tool (SWAT), to establish if these datasets could be used to effectively model metaldehyde in river catchments. To achieve the study aim, a SWAT model was developed and calibrated for the River Medway catchment (UK). The results of calibration (1994–2004) and validation (2005–2016) of average daily streamflow (m3/s) showed that the SWAT model could simulate water balance well (P-factor 0.68–0.85 and R-factor 0.54–0.82, NSE 0.42–0.60). Calibration (P-factor 0.72 and R-factor 1.35, NSE 0.31) and validation (P-factor 0.49 and R-factor 1.37, NSE 0.16) for daily soluble metaldehyde (mg active ingredient) load was also satisfactory. The most sensitive pesticide parameters for metaldehyde simulation included the timing and amount of pesticide (kg/ha) applied to the hydrological response units, the pesticide percolation coefficient and pesticide application efficiency. Outputs from this research demonstrate the potential application of SWAT in large complex catchments where routine monitoring is in place, but isn’t designed explicitly for the purpose of predictive modelling. The implications of this, are significant, because they suggest that SWAT could be applied universally to catchments using existing water industry datasets. This would allow more efficient use of historical datasets and would be applicable in situations where resources are not available for additional targeted monitoring programmes.

An improved process-based representation of stream solute transport in the soil and water assessment tools

Hydrological models have long been used to study the interactions between land, surface and groundwater systems, and to predict and manage water quantity and quality. The soil and water assessment tool (SWAT), a widely used hydrological model, can simulate various ecohydrological processes on land and subsequently route the water quality constituents through surface and subsurface waters. So far, in-stream solute transport algorithms of the SWAT model have only been minimally revised, even though it has been acknowledged that an improvement of in-stream process representation can contribute to better model performance with respect to water quality. In this study, we aim to incorporate a new and improved solute transport model into the SWAT model framework. The new process-based model was developed using in-stream process equations from two well established models—the One-dimensional Transport with Inflow and Storage model and the Enhanced Stream Water Quality Model. The modified SWAT model (Mir-SWAT) was tested for water quality predictions in a study watershed in Germany. Compared to the standard SWAT model, Mir-SWAT improved dissolved oxygen (DO) predictions by removing extreme low values of DO (<6 mg/L) simulated by SWAT. Phosphate concentration peaks were reduced during high flows and a better match of daily predicted and measured values was attained using the Mir-SWAT model (R2 = 0.17, NSE = −0.65, RSR = 1.29 with SWAT; R2 = 0.28, NSE = −0.04, RSR = 1.02 with Mir-SWAT). In addition, Mir-SWAT performed better than the SWAT model in terms of Chlorophyll-a content particularly during winter months, improving the NSE and RSR for monthly average Chl-a by 74 and 42%, respectively. With the new model improvements, we aim to increase confidence in the stream solute transport component of the model, improve the understanding of nutrient dynamics in the stream, and to extend the applicability of SWAT for reach-scale analysis and management.

A global sensitivity analysis approach for identifying critical sources of uncertainty in non-identifiable, spatially distributed environmental models: A holistic analysis applied to SWAT for input datasets and model parameters

Abstracts Environmental models have a key role to play in understanding complex environmental phenomena in space and time. Although their inherent uncertainty and non-identifiability are being increasingly recognized with the development and application of various methods, a more holistic analysis of all sources of model uncertainty is warranted. This paper addresses sources of uncertainty from various types of input datasets and model parameters, including those related to model structure assumptions, using a Soil and Water Assessment Tool (SWAT) application for the Minjiang River watershed, China. The holistic uncertainty sources in the SWAT application are summarized, and a sensitivity analysis (SA) is applied to examine the relative importance of the uncertainty sources influencing average streamflow and the load of nitrate. The analysis reveals that uncertainties related to the stream network precision and certain SWAT parameters are the most critical factors. Furthermore, building upon our SA framework to consider uncertainty sources more holistically would provide a good starting point for subsequent SA of spatially distributed environmental models in general.

Comparison of the SWAT and InVEST models to determine hydrological ecosystem service spatial patterns, priorities and trade-offs in a complex basin

• We compared the applicability of InVEST and SWAT in Nansihu Lake basin. • Comparison included the spatial pattern, trade-offs and priorities of three HESs. • The two models provide same reference though some differences in specific values. • Model Users should consider three kinds of conditions and four important factors. Models for the assessment of ecosystem services are important tools for policy-makers and researchers. However, the simulation results of different models vary greatly, and it is difficult for policy-maker to select a suitable model for specific areas. As a result, we compared the results of three hydrological ecosystem services (HESs) in a basin with diverse topography, Nansihu Lake basin, China, including the water supply, soil conservation and water purification services estimated by the Soil and Water Assessment Tool (SWAT) and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. Further comparisons of the HES results were conducted in the application of spatial pattern, priority and trade-off analyses through spatial statistics, hot spot and correlation analyses. Firstly, the results showed that the HES values in whole basin simulated by SWAT model were a little higher than those in InVEST model. Secondly, the spatial patterns of soil conservation service simulated by the two models were approximately similar in whole basin because of proximate simulation algorithm and input data, but the spatial distribution of the other two HESs varied greatly. In particular, the spatial patterns of water supply service simulated by the two models were more similar in hill areas than those in plain areas, while the spatial patterns of water purification service displayed opposite result. Furthermore, the distributions of hot and cold spots of HESs simulated by the two models were approximately consistent. Thirdly, the results of relation analysis to HESs were similar to SWAT and InVEST model roughly. The study suggested that the results of the two models could provide similar frames of reference for management and policy-making although different simulation results between the two models. This research can provide the theoretical basis for model selection, policy decision-making and regional ecosystem management.

Application of the Soil and Water Assessment Tool (SWAT) at Field Scale: Categorizing Methods and Review of Applications

HighlightsThis review study identified five different ways of setting up a SWAT model for field-scale analysis.Model setup for each field-scale modeling method and examples of application are discussed.Benefits and limitations of each method are discussed.Abstract. Although the Soil and Water Assessment Tool (SWAT) has been widely used as a watershed/basin scale model, recently there has been considerable interest in applying it at the field scale, especially for evaluation of best management practices and for building stakeholder confidence. In this study, a thorough review of the literature on field-scale application of SWAT was conducted. It was determined that there is more than one way of setting up a field-scale SWAT model depending on the spatial scale of the research as well as the research question to be answered. This article provides a detailed review of the methods used for field-scale SWAT modeling along with a summary of applications. This article also discusses the limitations and advantages of each method along with future research needs. The overarching goal of this article is to provide a valuable and time-conserving resource for future researchers interested in field-scale SWAT modeling. Keywords: Arc-SWAT, Field level, Field-scale resolution, Field-scale SWAT, SWAT.