Wonseok Jang

• Ph.D
• Fellow at University of Colorado Boulder

In this study, 52 asymptotic Curve Number (CN) regression equations were developed for combinations of representative land covers and hydrologic soil groups. In addition, to overcome the limitations of the original Long-term Hydrologic Impact Assessment (L-THIA) model when it is applied to larger watersheds, a watershed-scale L-THIA Asymptotic CN (...

The Korea Railroad Research Institute (KRRI) has developed a bimodal tram and advanced bus rapid transit (BRT) system which is an optimized public transit system created by mixing the railway’s punctual operation and the bus’ easy and convenient access. The bimodal tram system provides mass-transportation service with an eco-friendly and human-cent...

Soil erosion is an natural phenomenon. However accelerated soil erosion has caused many environmental problems. To reduce soil loss from a watershed, many management practices have been proposed worldwide. To develop proper and efficient soil erosion best management practices, soil erosion rates should be estimated spatially and temporarily. The Un...

The Universal Soil Loss Equation (USLE)-based modeling systems have been widely used to simulate soil erosion studies. However the GIS-based USLE modeling systems have limitation in gully erosion evaluation which is one of the most important factor in soil erosion estimation. In this study, the integrated soil erosion evaluation system using with S...

This study evaluates the applicability of the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model for assessing wildfire-induced changes in water-related ecosystem services at a localized scale. Wildfires significantly alter hydrological processes by reducing vegetation cover, which in turn affects water-yield dynamics. To quant...

Organic carbon in topsoil plays an important role in carbon sequestration to mitigate climate change. Topsoil contains the highest amount of organic carbon in soil layers, and conserving topsoil can provide an important solution to climate change. In South Korea, an extensive amount of topsoil has been lost due to the development of industrial comp...

The application of machine learning (ML) and remote sensing (RS) in soil and water conservation has become a powerful tool. As analytical tools continue to advance, the variety of ML algorithms and RS sources has expanded, providing opportunities for more sophisticated analyses. At the same time, researchers are required to select appropriate techn...

The application of machine learning (ML) and remote sensing (RS) in soil and water conserva-tion has become a powerful tool. As analytical tools continue to advance, the variety of ML al-gorithms and RS sources has expanded, providing opportunities for more sophisticated analyses. At the same time, researchers are required to select appropriate tec...

Agriculture is vulnerable to drought indicating that the increasing climate crisis requires the necessity of sustainable crop production. In this study, we developed the Irrigation Schedule and Management (ISM) model based on a simulation–optimization (Soil Water Atmosphere Plant-SWAP model with Genetic Algorithm-GA) framework. The ISM model finds...

Efficient water resource management requires accurate analyses of hydrological components and water balance. The Hydrological Simulation Program—FORTRAN (HSPF) model serves this purpose at the watershed scale. It has limited accuracy in calculating runoff and infiltration because the model simulates hydrological processes using one representative p...

Nitrate contamination in groundwater was evaluated using the concept of integrated aquifer assessment by combining groundwater characterization and risk analysis with tiered approaches for land and surface runoff contamination by soil chemicals and leaching of contamination to groundwater in the Upper White River Watershed (UWRW) in Indiana. Integr...

The South Korean government has recently focused on environmental protection efforts to improve water quality which has been degraded by nonpoint sources of water pollution from runoff. In order to take care of environmental issues, many physically-based models have been used. However, the physically-based models take a large amount of work to carr...

Crop models are increasingly used to evaluate crop yields at regional/global scales. These applications require the integration and processing of very large data sets in order to explore the implications of land management options across spatially heterogeneous scales. These modeling involve the combination of large spatially explicit data sets for...

Land use change needs to be considered in hydrological modeling because these affect various hydrologic components as well as sediment and water quality in a watershed. It cannot predict the hydrological phenomena accurately without considering the dynamics of land use changes. Most of the hydrological models reflect invariable land use with time....

Accurate analysis of water flow (streamflow and baseflow) is important for accurate water resources management. For accurate water resources management, modeled surface and groundwater hydrology should be calibrated simultaneously. The objectives of this study are: 1) to develop and provide an efficient flow calibration method (EFCM) for accurate b...

Baseflow is influenced by incoming groundwater to aquifers and is closely related to watershed characteristics. Understanding baseflow characteristics is of great importance to river ecosystems and water management. Baseflow estimation typically depends on the observed streamflow in gauged watersheds, but accurate predictions of streamflow through...

Groundwater management and protection has been facilitated by computational modeling of aquifer vulnerability and monitoring aquifers using groundwater sampling. The DRASTIC (Depth to water, Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone media, and hydraulic Conductivity) model, an overlay and index GIS model, has been used...

The Long-term Hydrologic Impact Assessment Model with Asymptotic Curve Number Regression Equation and Water Quality model (L-THIA ACN-WQ) has been developed to simulate streamflow as well as instream water quality using fewer parameters, compared to other watershed models. However, since model input parameters (i.e. hydraulic response unit (HRU) ma...

The authors wish to make the following corrections to this paper [1]: The author name “Bernard A. Engle” should be “Bernard A. Engel”[...]

The Long Term Hydrologic Impact Assessment (L-THIA) model was previously improved by incorporating direct runoff lag time and baseflow. However, the improved model, called the L-THIA asymptotic curve number (ACN) model cannot simulate pollutant loads from a watershed or instream water quality. In this study, a module for calculating pollutant loads...

It has been known that torrential rainfall events have been occurring worldwide due to climate change. The accelerated soil erosion has caused negative impacts on water quality and ecosystem of receiving waterbodies. Since soil security issues have been arising in various areas of the world, intensive interests have been given to topsoil management...

DRASTIC, with the use of different ratings criteria, has been widely used to evaluate aquifer vulnerability. Advantages of the DRASTIC model include the method's low cost of application and relative accuracy of model results for extensive regions with a complex geological structure. However, the current DRASTIC model has limitations including the l...

The Soil and Water Assessment Tool (SWAT) model has been used worldwide for many hydrologic and Non-Point Source (NPS) Pollution analyses on a watershed scale. However, it has many limitations in simulating the Vegetative Filter Strip (VFS) because it considers only ‘filter strip width’ when the model estimates sediment trapping efficiency and does...

SATEEC ArcView GIS system was developed using the Universal Soil Loss Equation (USLE) and sediment delivery ratio (SDR) modules. In addition, time-variant R and C modules and R5 module were developed and integrated into the SATEEC system in recent years. The SATEEC ArcView GIS 2.1 system is a simple-to-use system which can estimate soil erosion and...

Mandae watershed in Gangwon province has been known as one of soil erosion hot spot watersheds within Hanggang basin. Thus numerous efforts have been made to reduce soil erosion and pollutant loads into receiving watershed. However, proper best management practices have not been suggested because no monitoring flow and water quality data were avail...

Soil erosion is a natural phenomenon, but accelerated soil erosion is occurring with increased construction activities and intensive agricultural cultivation within many watersheds in recent years. To develop efficient soil erosion control best management practices, the soil erosion status in the target areas first needs to be understood spatially...

The purpose of this study is to evaluate sediment yield reduction under various field slope conditions with rice straw mat. The Vegetative Filter Strip Model-W (VFSMOD-W) and Soil and Water Assessment Tool (SWAT) were used for simulation of sediment yield reduction effect of rice straw mat. The Universe Soil Loss Equation Practice factor (USLE P fa...

Because of negative impacts of sediment-laden water by accelerated soil erosion and transport processes, many researchers have been investigating to develop most effective soil erosion management practices. Hydraulic structures such as soil erosion control dams and grit chamber are installed widely. Instead of structural best management practices,...

The Long-Term Hydrologic Impact Assessment (L-THIA) model has been widely used in estimating the long-term impacts of land use change because of its ease-of-use interface. However, the current L-THIA 2.3 is developed in the ArcView 3.x platform. Thus, there have been requests for enhanced version in ArcGIS platform because of computer processing ca...

In order to assess hydrologic and nonpoint source pollutant behaviors in the watershed with the Soil and Water Assessment Tool (SWAT) model, accuracy evaluation of the SWAT model should be conducted prior to the application of it to the watershed. When calibrating and validating hydrological components of the SWAT model, the Nash-Sutcliffe efficien...

The Soil and Water Assessment Tool (SWAT) model, semi-distributed model, first divides the watershed into multiple subwatersheds, and then extracts the basic computation element, called the Hydrologic Response Unit (HRU). In the process of HRU generation, the spatial information of land use and soil maps within each subwatershed is lost. The SWAT m...

Non Point Source Pollution (NPSP) load had been arising as a significant environmental issue. Especially excessive NPS input to the water bodies is causing serious impacts on river or stream ecosystems worldwide. To develop efficient best management practices for water quality improvement, hot spot target areas first need to be identified and under...

The total maximum daily load (TMDL) program has been established for water quality restoration and management in watershed. The Load Duration Curve (LDC) has been used for appropriate TMDL targets determination. However, the related personals had to first learn to develop the LDC, and then collect flow and water quality data for a site of interest...

Among wide range of hydrologic and water quality models, watershed scale SWAT has been widely used worldwide. The semi-distributed SWAT model extracts basic hydrologic and water quality computation element for each Hydrologic Response Unit (HRU) within subbasin. However, average topographic features of each subwatershed are used for topographic dat...

Soil and Water Assessment Tool (SWAT) model have been widely used in simulating hydrology and water quality analysis at watershed scale. The SWAT model extracts topographic feature using the Digital Elevation Model (DEM) for hydrology and pollutant generation and transportation within watershed. Use of various DEM cell size in the SWAT leads to dif...

Environment problem has been arising in many countries. Especially, soil erosion has been deemed as one of the biggest issues because sediment causes muddy water and pollutants, such as agricultural chemicals, flow in the stream with this sediment. Many studies, regarding soil loss and non-point source pollution from watershed, has been performed w...

Increasing urban sprawl and climate changes have been causing unexpected high-intensity rainfall events. Thus there are needs to enhance conventional disaster management system for comprehensive actions to secure safety. Therefore long-term and comprehensive flood management plans need to be well established. Recently torrential snowfall are occurr...

In recent days, the Non Point Source Pollution has been arising as a big environmental issue. Especially muddy water problem is causing serious impacts on river ecosystem not only in Korea but also most of the countries. Accordingly many methods to manage and prevent this problem have been investigated such as greet chamber, reservoir or debris bar...