Multi-scale quantification of non-point source nitrogen in a coastal river using an integrated multi-method source-tracing framework.

Uncertainty assessment in baseflow nonpoint source pollution prediction: The impacts of hydrographic separation methods, data sources and baseflow period assumptions

Non-point source pollution in rivers is an important factor affecting water quality. Quantifying the load of non-point source pollutants in the water and implementing improvement measures are critical for guaranteeing drinking water quality. In this study, the Dan River watershed, which is an important water source for Beijing, was investigated. Through a combination of water sampling and numerical simulations, the temporal and spatial distributions of nitrate nitrogen (NO3--N) and ammoniacal nitrogen (NH4+-N) loads in the watershed were determined, and the effects of vegetation restoration and agricultural management on reducing nitrogen pollution in the river were predicted. The NO3--N and NH4+-N loads in the watershed were higher during the wet season (July-September), accounting for more than 50% of the annual nitrogen output. The Soil and Water Assessment Tool (SWAT) was used to simulate the nitrogen load in the watershed. Pollution from nitrogen loading was serious in the lower reaches of the river; however, vegetation restoration can reduce the nitrogen output. Through scenario simulations, we found that an increase in forestland in the watershed would reduce the NO3--N and NH4+-N loads. The nitrate and NH4+-N loads in the watershed also decreased with reduced fertilizer use and reduced irrigation application in the watershed. Thus, reasonable land planning and agricultural management measures can effectively reduce nitrogen loss, which is an effective way to control non-point source pollution in watersheds and ensure river water quality.

The Soil and Water Assessment Tool (SWAT) model is a continuation of nearly 30 years of modeling efforts conducted by the U.S. Department of Agriculture (USDA), Agricultural Research Service. SWAT has gained international acceptance as a robust interdisciplinary watershed modeling tool, as evidenced by international SWAT conferences, hundreds of SWAT-related papers presented at numerous scientific meetings, and dozens of articles published in peer-reviewed journals. The model has also been adopted as part of the U.S. Environmental Protection Agency's BASINS (Better Assessment Science Integrating Point & Nonpoint Sources) software package and is being used by many U.S. federal and state agencies, including the USDA within the Conservation Effects Assessment Project. At present, over 250 peer-reviewed, published articles have been identified that report SWAT applications, reviews of SWAT components, or other research that includes SWAT. Many of these peer-reviewed articles are summarized here according to relevant application categories such as streamflow calibration and related hydrologic analyses, climate change impacts on hydrology, pollutant load assessments, comparisons with other models, and sensitivity analyses and calibration techniques. Strengths and weaknesses of the model are presented, and recommended research needs for SWAT are provided.

Quantification and variation characteristics of baseflow nonpoint source pollution in Yiluo River Basin, China

Best management practices (BMPs) are the tools which are adopted to run any activity while inflicting least negative impacts on the surrounding environment. Since, water pollution is one of the most important issues in today's world; it is indispensable to discuss the activities which are deteriorating its quality. Although, a number of treatment technologies and methods are in place for treating the point sources of pollution, there is a need to address nonpoint sources of pollution. There are many successful practices which are capable of curtailing the impacts of nonpoint source pollution, if adopted. In this paper an attempt has been made to evaluate the performance and trade‐offs of various management practices to address the issues of agricultural nonpoint source pollution. Nevertheless, there is a dearth of guiding principles which can pave a way for adoption of these practices. Therefore, an attempt has also been made to explore the aspects of policy formulations along with emphasizing the factors which can lead to adoption/ non‐adoption of such practices.

Abstract. The conservation of drinking water source reservoirs has a close relationship between regional economic development and people’s livelihood. Research on the non-point pollution characteristics in its watershed is crucial for reservoir security. Tang Pu Reservoir watershed was selected as the study area. The non-point pollution model of Tang Pu Reservoir was established based on the SWAT (Soil and Water Assessment Tool) model. The model was adjusted to analyse the temporal-spatial distribution patterns of total nitrogen (TN) and total phosphorus (TP). The results showed that the loss of TN and TP in the reservoir watershed were related to precipitation in flood season. And the annual changes showed an "M" shape. It was found that the contribution of loss of TN and TP accounted for 84.5% and 85.3% in high flow years, and for 70.3% and 69.7% in low flow years, respectively. The contributions in normal flow years were 62.9% and 63.3%, respectively. The TN and TP mainly arise from Wangtan town, Gulai town, and Wangyuan town, etc. In addition, it was found that the source of TN and TP showed consistency in space.

Impacts of manure application on SWAT model outputs in the Xiangxi River watershed

This paper introduces a Special Issue of Hydrological Sciences Journal containing 10 research papers which present current applications of the Soil and Water Assessment Tool (SWAT) for water resources assessment. First, an overview of selected, recently published papers with application of SWAT is given. The papers address the following topics: nutrients and related best management practices (BMPs); sediments and related BMPs; impoundment and wetlands; irrigation; bioenergy crops; climate change impact; and land-use change impacts. Then, papers from this Special Issue are briefly described, covering the themes: surface runoff and sediments; nonpoint-source pollution; surface water and groundwater; impacts of climate and land-use change; and large-scale SWAT applications. The presented model applications of SWAT were conducted across a variety of spatial scales, physiographic regions and climatic zones. This collection of papers demonstrates that applications of SWAT for water resources assessment are growing in number and cover drainage basins in many regions worldwide.Editor M. Acreman; Associate editor Xi Chen

Parameter uncertainty analysis of non-point source pollution from different land use types

The USEPA 2000 Clean Watersheds Needs Survey (CNWS) projected that the total cost of mitigating point and nonpoint source pollution problems would be $181.2 billion, of which $0.5 billion was attributed to agricultural cropland nonpoint source pollution. The Iowa Department of Natural Resources (IDNR) contends this projected cropland nonpoint source pollution cost was greatly underestimated for the 2000 CWNS, and thus sought a more thorough accounting of potential Iowa nonpoint source pollution costs for the 2004 CWNS. In response, an assessment was performed to generate estimates of nonpoint source pollution abatement costs and associated environmental benefits for a specific set of conservation practices that were selected in consultation with the IDNR. The assessment was performed for 13 major watersheds in Iowa by interfacing economic models developed in-house at CARD with the Soil and Water Assessment Tool (SWAT) model, and utilizing available conservation practice cost and other relevant data. The practices analyzed included terraces, grassed waterways, contouring, conservation tillage, land set-aside, and a simple nutrient reduction strategy. The cost of implementing the set of identified conservation practices was estimated to range from $423 million to $540 million annually, while the corresponding reductions in sediment, nitrates, total N and total P relative to the baseline across the 13 watersheds ranged from 4 to 42, 10 to 22, 11 to 26, and 13 to 45 %, respectively. The environmental results described here are preliminary; further review and perhaps refinement of the SWAT simulations is required before final results can be reported.

The Citanduy Watershed is one of the largest watersheds on Java Island and is in critical condition. The Upper Citanduy Sub-watershed is the main sub-watershed in the Citanduy Watershed, which needs attention because it greatly affects the quantity and quality of its water. The Soil and Water Assessment Tool (SWAT) model, which is a hydrological model developed in the United States, can be used to predict the quantity of water. However, the water balance in the SWAT model uses the water balance for plants planted on dry land (up land) and is less suitable for watersheds that have rice fields (low land). For watersheds that have rice fields, pot hole and modified SWAT features have been tried and developed. This study aims to analyze the performance of the SWAT model with original features, pot hole features, and modified features in the QSWAT program to predict water discharge in the Upper Citanduy Sub-watershed. The results of the study indicate that the modified SWAT has the best performance compared to the original SWAT and pot-hole SWAT, as indicated by the NSE and R2 values. The NSE values of the original SWAT, pot hole SWAT, and modified SWAT were 0.70, 0.73, and 0.75, respectively. The R2 values of the modified SWAT, Original SWAT, and pot hole SWAT were 0.94, 0.93, and 0.94, respectively.

Non-point source pollution poses a significant threat to global water security. Meanwhile, best management practices have been widely adopted for watershed management to address non-point source pollution. Selecting appropriate farmland management measures at suitable locations is crucial to minimizing the impact of agricultural non-point source pollution on water bodies. Using the Tianmu Lake basin as the study area, this research employed remote sensing and the Soil and Water Assessment Tool (SWAT) model to identify high-risk zones, simulate various management scenarios, and assess water quality improvements. The key findings are as follows: Significant land use changes were observed in the Tianmu Lake watershed, primarily characterized by the conversion of forested areas into tea plantations and farmland. Model calibration based on experimental results met simulation accuracy requirements. Non-point source pollution hotspots were mainly concentrated in the central part of the watershed, particularly in the Daxi and Shahe sub-watersheds, due to the prevalence of tea plantations. Implementation of ecological measures such as ecological ditches, vegetated buffer strips, and nutrient removal wetlands effectively controlled non-point source pollution. These findings provide technical insights for selecting and implementing surface pollution control measures within watersheds, offering practical guidance for sustainable watershed management.

An agreement between the governments of the province of Québec and the State of Vermont calls for a 41% decrease in phosphorus (P) loads reaching Missisquoi Bay, the northern portion of Lake Champlain. The agreement particularly targets the agricultural sector, since 80% of non-point source P inputs to the bay are associated with cultivated lands. In order to identify sustainable cropping practices likely to help meet the target P loads, the SWAT (soil and water assessment tool) model was employed to assess hydrological performance, erosion processes and P mobility on the bay’s principal Québec P contributing tributary, the 630 km2 Pike River watershed. Strong in-watershed spatial clustering of vulnerability to non-point source exports highlights the need for targeted implementation of sustainable agricultural practices and soil conservation works to derive the reduction in P loads. Planting cover crops over the 10% most vulnerable lands would result in roughly a 21% d rop in overall P exports at the watershed outlet, whereas the same 10% randomly distributed over the watershed would only contribute to a 6% drop in P exports. The study of different field-scale management scenarios indicated that achieving the targeted 41% reduction in P exports would require the widespread (half the land devoted to annual crops) implementation of sustainable cropping practices, and the conversion of a specific 10% of the territory to either cover crops or permanent prairie land. Meeting the P target-loads would require additional investments in the protection of floodplains and riparian strips, the targeted construction of runoff-control structures, and the rapid soil incorporation of manures on lands dedicated to annual crops. Key words: Soil and water assessment tool, modelling, sediment, phosphorus, cropping system, scenario, best agricultural management practices

The Soil and Water Assessment Tool (SWAT) model was used to assess the impacts of different land use scenarios on hydrological processes in the Fuhe watershed in Poyang Lake Basin, East China. A total of 12 model parameters were calibrated with observed monthly runoff data for 1982-1988 and validated for 1991-1998 for baseline conditions. The baseline test results of R2 and Nash-Sutcliffe model efficiency (NSE) values ranged between 0.88 and 0.94 across the calibration and validation periods, indicating that SWAT accurately replicated the Fuhe watershed streamflow. Several different land use scenarios were then simulated with the model, focusing on the impacts of land use change on the hydrology of the watershed. The results of hypothetical scenario simulations revealed that surface runoff declined while groundwater recharge and evapotranspiration (ET) increased, as forest land, agriculture land and/or grassland areas increased, as well as when paddy field and urban areas decreased. These results further showed that forest land has a higher capacity to conserve the water as compared to pasture land. The results of the real scenario simulations revealed that urbanization is the strongest contributor to changes in surface runoff, water yield, and ET. Urbanization can be considered as a potential major environmental stressor controlling hydrological components. Keywords: SWAT model, land use, streamflow, water budget, scenario simulation, Poyang Lake, Fuhe watershed DOI: 10.3965/j.ijabe.20150803.1132 Online first on [2015-03-17] Citation: Tao C, Chen X L, Lu J Z, Gassman P W, Sabine S, Jose-Miguel S P. Assessing impacts of different land use scenarios on water budget of Fuhe River, China using SWAT model. Int J Agric & Biol Eng, 2015; 8(3): 95－109.

This study is to assess the future impact of climate change on hydrological behavior considering future vegetation canopy prediction and its propagation to nonpoint source pollution (NPS) loads. The SWAT (Soil and Water Assessment Tool) model was used for the assessment. For a forest dominant ChungjuDam watershed of South Korea, the MIROC3.2hires climate data of SRES A1B and B1 scenarios were adopted and downscaled for the watershed. The future vegetation canopy information was projected by the monthly relationship between Terra MODIS (MODerate resolution Imaging Spectroradiometer) LAI (Leaf Area Index) and temperature. The future predicted LAI increased up to 1.9 in 2080s April and October because of the temperature increase 3.6 degrees C and 5.3 degrees C respectively. By reflecting the future LAI changes, the future estimated percent changes of maximum annual dam inflow, SS, T-N, and T-P were + 42.5% in 2080s A1B,-35.6% in 2020s A1B,+73.7% in 2080s A1B and-21.0% in 2080s B1 scenario respectively. The increase of T-N load was from the increase of subsurface lateral flows and the groundwater recharges by the future rainfall increase. The decrease of T-P load was by decrease of sediment load during wet days because the effect of LAI increase is greater than the increase of rainfall.