Younggu Her

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

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...

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...

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...

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...

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...

Machine learning (ML) is now commonly employed as a tool for hydrological prediction due to recent advances in computing resources and increases in data volume. The prediction accuracy of ML (or data-driven) modeling is known to be improved through training with additional data; however, the improvement mechanism needs to be better understood and d...

This publication is part of a larger body of work initiated by the UF/IFAS Extension Climate and Carbon Extension Educators that informs a general audience about climate issues and mitigation strategies. It was prepared to help Extension agents, farmers, and ranchers interested in carbon credit programs better understand the process of carbon credi...

Predicting flood wave propagation from reservoir failures is critical to practical flood hazard assessment and risk management. Flood waves are sensitive to topography, channel geometry, structures, and natural features along floodplain paths. Thus, the accuracy of flood wave modelling depends on how precisely those features are represented. This s...

This publication is meant to describe three major approaches to account for climate change in rainfall intensity-duration-frequency (IDF) curves and the pros and cons of each approach. This document aims to provide information to practicing engineers, Extension agents, and others interested in how projected changes in rainfall patterns can be consi...

The regression relationship between water discharge rates and nutrient concentrations can provide a quick and straightforward way to estimate nutrient loads. However, recent studies indicated that the relationship might produce large biases in load estimates and, therefore, may not be applicable in certain types of cases. The goal of this study is...

Future streamflow and nutrient projections are necessary for the development of sustainable water resources management plans and practices. Watersheds located in the Northern Lake Okeechobee (NLO) areas serve as a source of water and nutrients to Lake Okeechobee and its downstream areas, including the Everglades, in South Florida. This study invest...

The Soil and Water Assessment Tool (SWAT) has been widely employed to assist with decision making and management planning for assessing and mitigating the impact of climate change. This model has gained popularity in India as the country is facing increasing water issues under projected climate changes. However, a systematic review of the literatur...

Accurate prediction of flood waves from reservoir failures and their propagation is critical to effective flood hazard assessment and risk management. Flood waves are sensitive to floodplain topography, channel geometry, and hydraulic structures located along flow paths in downstream areas, and thus the accuracy of flood wave modelling is dependent...

The increased concentrations of greenhouse gases have led to global warming and an increased frequency and intensity of extreme weather events. Such changes in weather patterns may have unexpected implications for everyday life and water resource management in coastal and inland areas; thus, it is critical to understand the pattern of the changes....

Subsurface drainage systems are effective management practices employed to remove excess soil water, thereby improving soil aeration and crop productivity. However, these systems can also contribute to water quality issues by enhancing nitrate leaching and loads from agricultural fields. The Soil and Water Assessment Tool (SWAT) is commonly used to...

This article introduces NOAA Atlas 14 and explains how to use it to help Extension agents and the general public estimate the frequency of any storm event of interest. The frequency estimate of a storm event using NOAA Atlas 14 helps the user to understand how large a storm is in relation to the historical storm events that occurred at a certain lo...

Low floodplain wetlands such as the Western Everglades in South Florida are vulnerable to extreme weather events, and their water quality and ecosystem functions vary greatly depending on changes in water levels and discharges. The future (i.e., the mid and late 21st century) climate is projected to result in increased frequency and magnitude of ex...

Study Region Lake Okeechobee and its drainage basins, the Northern Lake Okeechobee (NLO) watershed, have faced climate variability and changes. The frequencies and magnitudes of extreme weather events are projected to increase in the future, and the impact of climate change on hydrological changes in upstream watersheds would significantly affect t...

Computer simulation models are a useful tool in planning, enabling reliable yet affordable what-if scenario analysis. Many simulation models have been proposed and used for urban planning and management. Still, there are a few modeling options available for the purpose of evaluating the effects of various stormwater control measures (SCM), includin...

The water quality of a waterbody is determined by internal hydrodynamic processes as well as external loadings. Understanding the interaction between the external loading and internal process of a waterbody is essential for efficient water management and water quality improvement. Studies and efforts have focused on water and nutrient loading from...

This infographic illustrates the global carbon cycle and discusses sources, sinks, carbon markets, and carbon sequestration. Written by Jehangir Bhadha, Mark Clark, Michael Andreu, Yuchuan Fan, Tara Wade, and Young Gu Her, and published by the UF/IFAS Department of Agricultural and Biological Engineering, January 2023.

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...

This publication introduces the findings from a recent study conducted to find safer levels of water salinity in the irrigation of two economically important foliage crops: Hibiscus rosa-sinensis and Mandevilla splendens. Written by Young Gu Her and E. Vanessa Vassilaros, and published by the UF/IFAS Department of Agricultural and Biological Engine...

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...

This article introduces concepts related to carbon sequestration, credits, and markets to help Extension agents, farmers, and concerned residents to better understand how agriculture can help to mitigate climate change, and thus become a part of Florida’s carbon economy. Written by Young Gu Her, Tara Wade, Sawssan Boufous, Jehangir Bhadha, and Mich...

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...

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...

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...

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...

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...

This publication introduces the TIGER/Line Shapefile datasets and demonstrates how we can extract and map spatial information from the US Census data using the shapefiles. Written by Young Gu Her and Ziwen Yu, and published by the UF/IFAS Department of Agricultural and Biological Engineering, May 2021.

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Rice growing in paddy fields equipped with irrigation and drainage systems is less affected by unfavorable weather patterns such as prolonged dry periods and severe storms, but for the same reason, the fields discharge water to maintain suitable water depths even between rainfall events. Studies have been done to examine the quality of water draine...

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...

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...

We developed an Excel-based computational template Extension educators can use to assist clientele with scheduling irrigation for efficient use of water. With the template, the user applies the dual crop coefficient method to calculate evaporation and transpiration rates separately, with the result being more accurate soil water tracking as compare...

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...

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...

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...