Younggu Her

Younggu Her
University of Florida | UF · Department of Agricultural and Biological Engineering / Tropical Research and Extension Center

PhD

About

94
Publications
44,742
Reads
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939
Citations
Additional affiliations
August 2016 - present
University of Florida
Position
  • Professor (Assistant)
November 2014 - July 2016
Texas A&M University
Position
  • Researcher
February 2011 - October 2014
Purdue University
Position
  • PostDoc Position
Education
August 2006 - May 2011
March 2000 - February 2002
Seoul National University
Field of study
  • Soil and Water Conservation (Water Resource) Engineering
March 1995 - February 2000
Seoul National University
Field of study
  • Soil and Water Conservation (Water Resource) Engineering

Publications

Publications (94)
Article
Full-text available
The level of model complexity that can be effectively supported by available information has long been a subject of many studies in hydrologic modeling. In particular, distributed parameter models tend to be regarded as overparameterized because of numerous parameters used to describe spatially heterogeneous hydrologic processes. However, it is not...
Article
Distributed, continuous hydrologic models promote better understanding of hydrology and enable integrated hydrologic analyses by providing a more detailed picture of water transport processes across the varying landscape. However, such models are not widely used in routine modeling practices, due in part to the extensive data input requirements, co...
Article
Full-text available
The objective of this study was to evaluate effects of conservation practices actually implemented in reducing sediment and nutrient loads at field and watershed scales. We obtained locational information of 10,028 conservation practices implemented in the St. Joseph River watershed from USDA - Natural Resources Conservation Service (NRCS). Conside...
Article
Assessing the performance of LID practices at a catchment scale is important in managing urban watersheds. Few modeling tools exist that are capable of explicitly representing the hydrological mechanisms of LIDs while considering the diverse land uses of urban watersheds. In this paper, we propose computational modules that simulate the hydrologica...
Article
Full-text available
The quantification of uncertainty in the ensemble-based predictions of climate change and the corresponding hydrological impact is necessary for the development of robust climate adaptation plans. Although the equifinality of hydrological modeling has been discussed for a long time, its influence on the hydrological analysis of climate change has n...
Article
Irrigation, essential for food production and landscape maintenance, affects soil water dynamics, water quality, and soil chemistry. However, the multidimensional role of irrigation has not been a focus in irrigation sciences. We evaluated the performance of different irrigation scheduling methods regarding water saving, water quality protection, a...
Article
Full-text available
Soluble nitrogen is highly mobile in soil and susceptible to leaching. It is important to identify nitrogen transport pathways so that the sources can be efficiently targeted in environment management. This study quantified the contribution of direct runoff and baseflow to nitrate + nitrite loading by separating flow and nitrate + nitrite concentra...
Article
Street-side vegetation greenery contributes substantial health benefits for pedestrians. Multi-year street view images are expected to enable the monitoring of dynamic street-side vegetation greenery changes and the development of targeted urban landscape plans. However, the potential of multi-year street view images used for the assessment of stre...
Article
Full-text available
Quantifying reservoir water balance is an essential process for the efficient management of water resources. Water level records are often the only data available for reservoir analysis, which causes an ill‐posed problem in water resource system planning. This study proposes an analytical framework to estimate reservoir inflow and outflow from wate...
Article
Haitian watersheds suffer from a lack of environmental management and the absence of conservation practices, which impairs natural resources and agricultural productivity. This is aggravated by harvesting trees to compensate for reduced crop production and income. Deforestation can further deteriorate the natural and agricultural systems by increas...
Article
Grid-based spatially distributed hydrological modeling has become feasible with advances in watershed routing schemes, remote sensing technology, and computing resources. However, the need for long-running times on a substantial set of computational resources prevents a spatially detailed modeling program from being widely used, particularly in fin...
Article
Full-text available
Soil phosphorus (P) built up due to past management practices, legacy P, in the Lake Okeechobee Watershed (LOW) in south-central Florida, U.S.A., is often discussed as the root cause of lake eutrophication. Improvement of the lake’s water quality requires the identification of critical P sources and quantifying their contributions. We performed a g...
Article
Rain barrels/cisterns, a popular type of low impact development (LID) practice, can restore urban hydrological processes and decrease municipal water use by harvesting roof runoff for later use, such as landscape irrigation. However, tools to assist decision makers in creating efficient rainwater harvesting and reuse strategies are limited. This st...
Article
Full-text available
Development of a high-accuracy method to extract arable land using effective data sources is crucial to detect and monitor arable land dynamics, servicing land protection and sustainable development. In this study, a new arable land extraction index (ALEI) based on spectral analysis was proposed, examined by ground truth data, and then applied to t...
Article
Full-text available
Salinity is one of the most common and critical environmental factors that limit plant growth and reduce crop yield. The aquifers, the primary sources of irrigation water, of south Florida are shallow and highly permeable, which makes agriculture vulnerable to projected sea level rise and saltwater intrusion. This study evaluated the growth respons...
Article
Full-text available
Excessive nutrient loadings from drainage areas and resulting water quality degradation in rivers are the major environmental issues around the world. The water quality further deteriorates for the large seasonal variation of precipitation and water flow. Environmental decision makers have been exploring affordable and effective ways of securing en...
Article
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Geographic information and geospatial data are vital in many practical fields, including precision agriculture, natural resources management, flood zone mapping and management, and environmental assessment. This 6-page publication introduces publicly available geospatial data, including elevation, land use, soil, satellite imagery, and other themat...
Article
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The effectiveness of agricultural productivity is dependent on the availability of ambient natural resources as well as on the efficiency of on-site management practices. The overall understanding of a production system can help with finding management options that enable for the available resources to be used more efficiently and thus improving pr...
Article
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Climate is the long-term patterns and fluctuations in air and moisture. This 5-page article explains how future climate is projected using mathematical models and introduces common scientific terms used when discussing climate change. Written by Young Gu Her, Zachary Brym, Ashley Smyth, and Elias Bassil, and published by the UF/IFAS Department of A...
Article
Full-text available
The chloride ion (Cl−) can adversely affect an aquatic ecosystem, but it is not clear how Cl− moves with runoff and how its transport processes are related to land uses and land cover. This study investigated how the loading characteristics of Cl− vary depending on storm events and land cover in a temperate region. We monitored Cl− concentrations i...
Article
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This 8-page article explains how agriculture and natural resources may respond to projected future climate and how climate projections can be useful in developing management plans for the improved sustainability of Florida’s agriculture and natural resources. It also aims to help increase the public awareness of climate change impacts on Florida an...
Article
Full-text available
The impacts of sea level rise on ecosystems and natural resources are a major concern in Florida, especially in low-lying coastal areas such as south Florida. Sea level rise can impact many aspects of Florida’s economy, including urban development, agriculture, infrastructure, and natural areas. This 16-page document introduces, evaluates, and summ...
Article
Full-text available
Monitoring provides data and information necessary for water quality assessment, but often it is prohibitive, especially when frequent sampling is required. In this study, we explored feasible sampling intervals for improved efficiency of nonpoint source (NPS) pollution assessment. We compared NPS pollutant loads calculated with concentration sampl...
Article
Paddy fields play a critical role as storage for the retention of surface water in hydrological processes, but their water balance is complicated by irrigation and drainage management. Studies have proposed flow routing methods for paddy fields by simplifying the hydrological and hydraulic complexity associated with drainage processes. However, the...
Article
Full-text available
Land subsidence monitoring provides information required when developing land use plans and allows for proactive management of subsidence issues. However, it has been challenging to accurately detect land subsidence areas, especially those under waterbodies. This study evaluated the applicability of integrated use of the optical Landsat-8 OLI and m...
Article
Full-text available
Irrigation return flow (RF) is a critical component of the water cycle in an agricultural watershed, influencing the flow regime of downstream river. As such, it should be accurately quantified when developing water resources management plans and practices. Although many studies have proposed ways to quantify RF, uncertainty in RF estimates has not...
Article
Rainfall events largely control hydrological processes occurring on and in the ground, but the performance of climate models in reproducing rainfall events has not been investigated enough to guide selection among the models when making hydrological projections. We proposed to compare the durations, intensities, and pause periods, as well as depths...
Article
The Three Gorges Project (TGP) – which involved the construction of a large dam between the cities of Chongqing and Yichang – resulted in major changes to the landscape of the surrounding region, creating wide areas of open water on its completion in 2003. This article investigates the immediate effects of the TGP on storm event patterns and local...
Article
This 8-page document gives an overview of Florida temperature and rainfall during the past 20 years based on historical FAWN data to provide information about the temporal and spatial trends of Florida weather and the frequency and size of extreme weather events such as heavy rainfall and drought. This document also investigates the characteristics...
Article
Full-text available
Vermicomposting has been recommended as an eco-friendly method to transform organic waste into nutrient resources with minimum energy input. However, odor and pest issues associated with this method limit the use of vermicomposting, especially in indoor conditions. This study evaluated the effectiveness of applying hypochlorous acid (HOCl) to deodo...
Article
Full-text available
Heavy metals, including arsenic from abandoned mines, are easily transported with sediment and deposited in waterbodies such as reservoirs and lakes, creating critical water quality issues when they are released. Understanding the leaching of heavy metals is necessary for developing efficient water quality improvement plans. This study investigated...
Article
Full-text available
Regionalized lumped rainfall-runoff (RR) models have been widely employed as a means of predicting the streamflow of an ungauged watershed because of their simple yet effective simulation strategies. Parameter regionalization techniques relate the parameter values of a model calibrated to the observations of gauged watersheds to the geohydrological...
Article
Full-text available
Agricultural water supply (AWS) estimation is one of the first and fundamental steps of developing agricultural management plans, and its accuracy must have substantial impacts on the following decision-making processes. In modeling the AWS for paddy fields, it is still common to determine parameter values, such as infiltration rates and irrigation...
Preprint
Full-text available
Heavy metals, including arsenic from abandoned mines, are easily transported with sediment and deposited in water bodies such as reservoirs and lakes, creating critical water quality issues when they are released. Understanding the leaching of heavy metals is necessary for developing efficient water quality improvement plans. This study investigate...
Article
The identification of factors affecting the first flush phenomenon is important for the control of urban nonpoint source pollution. This study developed machine learning algorithms, the regression tree (RT) and random forest (RF) algorithms, to predict the mass first flush ratio (MFFn) from seven rainfall-related variables. We also evaluated the pr...
Article
Shallow aquifers significantly impact crop growth as saturated soil conditions may occur. Canals are widely constructed in such areas to mitigate groundwater saturation or flooding. We applied a simulation model to estimate the occurrence of root zone saturation [root zone saturation index (RZSI)] for agricultural crops and to identify factors that...
Article
Mathematical models with small numbers of parameters are useful for hydrological analyses and water resources planning as they are easier to prepare, use, and interpret compared to more complex models. Many simple model structures and simulation strategies have been developed, but there is still substantial room for improvement in the efficiency of...
Article
The curve number (CN) method has been widely used to estimate the amount of direct runoff generated in agricultural watersheds around the world. However, its applicability to rice paddy fields has yet to be sufficiently tested to suggest the range of alternative CNs for irrigated and drained paddies. This study proposes CNs applicable to rice paddi...
Article
Hurricanes are the most powerful and largest weather event happening in the air, affecting almost everything in their paths. Their strong winds and heavy rain can directly impact both inland and coastal areas in short periods, usually around a day. Understanding hurricane effects is the first step to preparing for hurricanes. The effects of hurrica...
Article
Full-text available
Reservoir sedimentation is a major environmental issue, and various sediment load controls and plans have been proposed to secure clean and safe water resources. The objectives of this study were to estimate soil loss in the upper basins and predict sediment deposition in Ipjang reservoir using hydrologic and hydraulic model. To do so, SWAT (Soil a...
Article
Full-text available
This 4-page fact sheet describes proper interpretation of rainfall event probabilities and recurrence intervals, particularly as they are used by engineers and water resources managers in the design and construction of hydraulic structures, such as dams, levees, and canals. This article focuses on rainfall, but its explanations and concepts can be...
Article
Hydrological connectivity can strongly influence phytoplankton communities and ecological status through the interchange of nutrients and organisms in interconnected aquatic habitats. However, there is little consensus regarding the distinction of environmental variables influencing phytoplankton communities related to hydrological connectivity in...
Article
Multi-objective calibration can help identify parameter sets that represent a hydrological system and enable further constraining of the parameter space. Multi-objective calibration is expected to be more frequently utilized, along with the advances in optimization algorithms and computing resources. However, the impact of the number of objective f...
Article
The current FORTRAN code of SWAT (SWAT2012) is being rebuilt to ease new model and module development by incorporating object-oriented programming techniques into defining spatial objects and calculating variables. SWAT+, the new SWAT code, is expected to offer flexible watershed representation with linked spatial objects. Ideally, SWAT+ produces o...
Article
Hydrologically sensitive areas (HSAs) largely control watershed response to rainfall, along with water and pollutant transport processes. Thus, their identification is critical in watershed management planning. Although watershed processes have been studied enough to provide a good understanding of HSA dynamics, only a few concepts and methods are...
Chapter
Full-text available
In this chapter, we describe Florida’s agriculture, the vulnerability of its crops and livestock to climate change and possible adaptation strategies. Much of Florida’s agricultural success is linked to its moderate climate, which allows vegetable and fruit crop production during the winter/spring season as well as the production of perennial crops...
Article
Full-text available
Simulink, an extension of MATLAB, is a graphics-based model development environment for system modeling and simulation. Simulink's user-friendly features, including block (data process) and arrow (data transfer) objects, a large number of existing blocks, no need to write codes, and a drag and drop interface, provide modelers with an easy developme...
Presentation
Full-text available
An application of HYSTAR to a watershed in Brazil
Article
Hydrologic modeling outputs are influenced by how a watershed system is represented. Channel routing is a typical example of the mathematical conceptualization of watershed landscape and processes in hydrologic modeling. We investigated the sensitivity of accuracy, equifinality, and uncertainty of Soil and Water Assessment Tool (SWAT) modeling to c...
Article
Full-text available
Evaluating the effectiveness of conservation practices (CPs) is an important step to achieving efficient and successful water quality management. Watershed-scale simulation models can provide useful and convenient tools for this evaluation, but simulated conservation practice effectiveness should be responsive to parameter values used to represent...
Technical Report
Full-text available
Florida climate is characterized by wet and dry seasons, with rainfall predominantly occurring between June and October. Annual rainfall amounts range from 40 to 60 inches per year depending on the location (Florida Climate Center 2016). Florida rainfall is also spatially variable, meaning rainfall may occur on one side of the street but not on the...
Article
Future climate change has the potential to significantly impact crop growth, both directly due to CO2 enhancement and indirectly, through temperature and moisture impacts. This work investigates the biophysical and hydrological effects of future climate change, including trends in CO2, in the St. Joseph River watershed, Eastern Corn Belt. In this s...
Article
Full-text available
Because hydrologic responses of an agricultural watershed are influenced by many natural and man-made factors including pond/reservoir, management practices, and/or irrigation/drainage, strategies of hydrological modeling for the watershed must be case-dependent and thus carefully designed to effectively reflect their roles as critical hydrologic c...
Article
Conservation practices are designed and implemented to reduce soil erosion and protect water quality, but their effectiveness has been found to vary widely. This study investigated spatial and temporal variability in sediment and nutrient loads and load reductions achieved by implementing conservation practices to understand the implications of lan...
Article
A representative curve number (CN) of a catchment is often calculated from the area-weighted average of CN values of unique land use and soil combinations. While convenient for implementation, this method is known to underestimate direct runoff depth. This paper investigates the mathematical mechanism of the expected underestimation and proposes al...
Article
Parameter uncertainty in hydrologic modeling is commonly evaluated, but assessing the impact of spatial input data uncertainty in spatially descriptive 'distributed' models is not common. This study compares the significance of uncertainty in spatial input data and model parameters on the output uncertainty of a distributed hydrology and sediment t...