Hakkwan Kim

Predicting the impacts of climate change on nonpoint source pollutant loads from agricultural small watershed using artificial neural network.

This study described the development and validation of an artificial neural network (ANN) for the purpose of analyzing the effects of climate change on nonpoint source (NPS) pollutant loads from agricultural small watershed. The runoff discharge was estimated using ANN algorithm. The performance of ANN modelwas examined using observed data from s tudy watershed. The simulationresults agreed well with observed values during calibration and validation periods. NPS pollutant loads were calculated from load-discharge relationship driven by long-term monitoring data. LARS-WG (Long Ashton Research Station-Weather Generator) model was used to generate rainfall data. The calibrated ANN model and load-discharge relationship with the generated data from LARS-WGwere applied to analyze the effects of climate change on NPS pollutant loads from the agricultural small watershed. The results showed that the ANN model provided valuable approach i n estimating future runof f discharge, and the NPS pollutantloads.

Assessing Irrigation Water Capacity of Land Use Change in a Data-Scarce Watershed of Korea

AbstractThe objective of this study is to assess stable irrigation water capacity and erosion on the basis of water and sediment balance analysis of land use change. The reservoir water balance analysis is calculated by the daily irrigation reservoir operation model (DIROM) for simulating daily inflow and release rates for irrigation reservoirs. The reservoir capacity change for assessing the sediment flux is predicted using the universal soil loss equation (USLE), sediment delivery ratio (SDR), and trap efficiency. To analyze soil erosion changes according to land use changes, Landsat-5 images were selected. Spatial distribution of deposited sediment is estimated by the U.S. Bureau of Reclamation (USBR) method and the hydrodynamic, sediment and contaminant transport model (HSCTM-2D), which is a finite-element model for simulating surface water flow and sediment transport. The model performance was verified by comparing simulated and observed data. The simulated results, which were validated using an inte...

Climate and Land use Changes Impacts on Hydrology in a Rural Small Watershed

The objective of this study is to evaluate the hydrologic impacts of climate and land use changes in a rural small watershed. HadCM3 (Hadley Centre Coupled Model, ver.3) A2 scenario and LARS-WG (Long Ashton Research Station - Weather Generator) were used to generate future climatic data. Future land use data were also generated by the CA-Markov (Cellular Automata-Markov) method. The Soil and Water Assessment Tool (SWAT) model was used to evaluate hydrologic impacts. The SWAT model was calibrated and validated with stream flow measured at the Baran watershed in Korea. The SWAT model simulation results agreed well with observed values during the calibration and validation periods. In this study, hydrologic impacts were analyzed according to three scenarios: future climate change (Scenario I), future land use change (Scenario II), and both future climate and land use changes (Scenario III). For Scenario I, the comparison results between a 30-year baseline period (1997~2004) and a future 30-year period (2011~2040) indicated that the total runoff, surface runoff, lateral subsurface runoff, groundwater discharge, and evapotranspiration increased as precipitation and temperature for the future 30-year period increased. The monthly variation analysis results showed that the monthly runoff for all months except September increased compared to the baseline period. For Scenario II, both the total and surface runoff increased as the built-up area, including the impervious surface, increased, while the groundwater discharge and evapotranspiration decreased. The monthly variation analysis results indicated that the total runoff increased in the summer season, when the precipitation was concentrated. In Scenario III, the results showed a similar trend to that of Scenario II. The monthly runoff for all months except October increased compared to the baseline period.

Development of Hydrologic Data Management System Based on Relational Database

In this paper, the Hydrologic Data Management System (HDMS) was developed for the efficient management of hydrologic data. The applicability of the system was demonstrated using the hydrologic data of study watershed located in the southwest from Suwon city MySQL 5.0, relational database management system, and MS Visual Basic 6.0 were used for the development of MS windows based HDMS. The primary components of the HDMS are data search system, data management system, and data analysis system. Data search and management systems provide basic functions for the efficient data search, storage, update and export. Data analysis system enables the users to get the further and diverse hydrologic statistical information from the stored data. Furthermore, the accuracy and quality of hydrologic data was analyzed and evaluated through data analysis system.

Flood Inundation Analysis in a Low-lying Rural Area using HEC-HMS and HEC-RAS

The objective of this study is to analyze the flood inundation in a low-lying rural area. The study watershed selected for this study includes the Il-Pae and Ahn-Gok watersheds. It is located in the Namyangju, Korea and encompasses . A major flood event that occurred in July 2011 was chosen as the case for the flood inundation analysis. The Hydrologic Engineering Center`s Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS) were used to simulate flood runoff and water surface elevation at each cross-section, respectively. The watershed topographic, soil, and land use data were processed using the GIS (Geographic Information System) tool for the models. The contribution to the total flood volume was estimated based on the results simulated by HEC-HMS and HEC-RAS. The results showed that the overflow discharge from the Il-Pae stream constituted 80% of the total flood volume. The contributions of rainfall falling directly on the inundation area and overflow discharge from the Ahn-Gok stream were 15 % and 5 %, respectively. The simulation results in different levee scenarios for the Ahn-Gok stream were also compared. The results indicated that the levee could reduce the flood volume a little bit.

Selecting Target Sites for Non-point Source Pollution Management Using Analytic Hierarchy Process

This paper suggests a hierarchial method to select the target sites for the nonpoint source pollution management considering factors which reflect the interrelationships of significant outflow characteristics of nonpoint source pollution at given sites. The factors consist of land slope, delivery distance to the outlet, effective rainfall, impervious area ratio and soil loss. The weight of each factor was calculated by an analytic hierarchy process(AHP) algorithm and the resulting influencing index was defined from the sum of the product of each factor and its computed weight value. The higher index reflect the proposed target sites for nonpoint source pollution management. The proposed method was applied to the Baran HP#6 watershed, located southwest from Suwon city. The Agricultural Nonpoint Pollution Source(AGNPS) model was also applied to identify sites contributing significantly to the nonpoint source pollution loads from the watershed. The spatial correlation between the two results for sites was analyzed using Moran`s I values. The I values were for total nitrogen(T-N), and for total phosphorus(T-P), respectively. The results showed that two independent estimates for sites within the test water-shed were highly correlated, and that the proposed hierarchial method may be applied to select the target sites for nonpoint source pollution management.

Estimating Soil Losses from Saemangeum Watershed based on Cropping Systems

A Geographic Information System (GIS) was developed to estimate basin-wide soil losses using the Universal Soil Loss Equation (USLE). It was applied to estimate the annual average soil losses from the Saemangeum watershed. The USLE factors for each subarea of uniform land use and treatments were estimated from the GIS routines from digital topographic maps, land cover and detailed soil maps. A routine was developed to estimate the averaged cropping management factors (C) of USLE for multi-cropping farmlands, based on cropping system records from the district offices. The resulting C factors ranged from 0.28 to 0.35 for multi-cropping areas. The estimated annual average soil loss was approximately 2.9 million tonnes. Typical soil losses from different land uses were 0.8 t/ha at paddies, 33.7 t/ha at uplands and 1.1 t/ha from forested mountains. It was also found that 6.0% of the arable land of the watershed possessed high risks of soil losses, and conservation measures were needed to reduce soil losses.

Effects of Saline Irrigation Water on Lettuce and Carrot Growth in Protected Cultivation

The objectives of this study were to monitor and assess the effects of saline irrigation water on lettuce and carrot growth in protected cultivation. One control and 4 treatments with three replications, which were differentiated according to the level of salinity in irrigated water, were employed for each vegetable to assess the effects of the irrigation with saline water. Monitoring results showed that the use of irrigation water containing above a certain level of salinity was found to cause excessive accumulation of salts in the soil as saline irrigation water increased electrical conductivity (EC) and sodium () content in both lettuce and carrot soil samples, while tap water irrigation used as control decreased the salinity in the samples. The salinity higher than the threshold level of irrigation water was found to reduce the yields of lettuce and carrot, while in less than the threshold level the higher the salinity of the irrigation water increased the yields. The salinity of the irrigation water also appeared to increase the internal salinity of the plant as the content in plant increased as the salinity of irrigation water increase. Increased content was analyzed to be able to increase the sugar content in carrot. This study could contribute to suggest water quality criteria for safe use of saline water in protected cultivation, although long-term monitoring is needed to get more representative results.

A Study on the Economic Analysis of Wastewater Reclamation and Reuse Systems for Agriculture using a System Dynamics Approach

Abstract. Many studies have reported additional treatment is needed to use wastewater for agricultural purpose. Economic considerations should be taken into account to establish infrastructure for agricultural reuse because of a large amount of water use in irrigation and relatively low water quality requirement. The objective of this study was to conduct economic analysis of wastewater reclamation and reuse systems for agriculture. A system dynamics approach considering complexity and dynamics in the wastewater reuse systems was used for the economic analysis, which are related with social, environmental, and economic problems. Sensitivity and benefit cost analysis for wastewater reuse systems was conducted through the established economic assessment model. The result of sensitivity analysis showed that water resources development and installation cost were the most sensitive for total benefits and costs, respectively. The scenario-based test of the organized economic assessment model shows marginal cost ranges and enables decision-makers to decide reasonable cost for the wastewater reuse systems for agriculture.

Analysis of Landscape Structure on the Impervious Cover of the Gap-Stream Watershed using FRAGSTATS

An impervious cover in the watershed management has been used as effective indicators. It is a very useful barometer to measure the impacts of watershed development on aquatic systems. Hence, it is necessary to survey the impervious cover of a watershed and to develop an impervious cover model (ICM) for supporting best management practices. The main objectives of this study were to investigate the spatial patterns of the impervious cover, to calculate landscape indices using FRAGSTATS, and to develop an ICM in the Gap-stream watershed and its six sub-watersheds. The results showed that the impervious cover of the Gap-stream watershed increased from 4.9 % in 1975 to more than 11.2 % in 2000, the number of impervious cover fragments increased from 662 to 3,578, and the landscape shape index increased from 27.0796 to 91.1982. Fragmentation was severe within the Yudeungcheon downstream and the Gapcheon downstream of six sub-watersheds. This paper presented the results derived landscape indices to define landscape patterns and structure for the Gap-stream watershed. Our results indicate that altered land use might be influenced changes in landscape structure.