Hyung-Joong Kwon

Evaluation of Paddy Water Storage Dynamics during Flood Period in South Korea

A daily paddy water balance model was developed using four years (1996–1997 and 2001–2002) field experimentals data of two locations. The model could simulate the actual daily ponding depth of paddy pretty well by treating paddy levee height and threshold ponding depth indicating irrigation time as ten days average parameters of the model with 0.76 four year average Nash-Sutcliffe efficiency. The amount ranging from 425.1 mm in 1996 to 850.8 mm in 2002. The storage ratio (amount of storage divided by rainfall) linearly decreased as total rainfall amount increased within the range of observed rainfall. From the model application, direct seeding type was more favorable to store rainfall than transplanting type.

Analysis of Hydrological Impact Using Climate Change Scenarios and the CA-Markov Technique on Soyanggang-dam Watershed

The objective of this study was to analyze the changes in the hydrological environment in Soyanggang-dam watershed due to climate change results (in yews 2050 and 2100) which were simulated using CCCma CGCM2 based on SRES A2 and B2. The SRES A2 and B2 were used to estimate NDVI values for selected land use using the relation of NDVI-Temperature using linear regression of observed data (in years 19982002). Land use change based on SRES A2 and B2 was estimated every 5- and 10-year period using the CA-Markov technique based on the 1985, 1990, 1995 and 2000 land cover map classified by Landsat TM satellite images. As a result, the trend in land use change in each land class was reflected. When land use changes in years 2050 and 2100 were simulated using the CA-Markov method, the forest class area declined while the urban, bareground and grassland classes increased. When simulation was done further for future scenarios, the transition change converged and no increasing trend was reflected. The impact assessment of evapotranspiration was conducted by comparing the observed data with the computed results based on three cases supposition scenarios of meteorological data (temperature, global radiation and wind speed) using the FAO Penman-Monteith method. The results showed that the runoff was reduced by about 50% compared with the present hydrologic condition when each SRES and periods were compared. If there was no land use change, the runoff would decline further to about 35%.

Extraction of Snowmelt Factors using NOAA Satellite Images and Meteorological Data

Establishment of snowmelt factors is necessary to simulate stream flow using snowmelt models during snowmelt periods. The few observed data related snowmelt was the major cause of difficulty in extracting snowmelt factors such as snow cover area, snow depth and depletion curve. The objective of this study was to extract snowmelt factors using RS, GIS technique and meteorological data. Snow cover maps were derived from NOAA/AVHRR images for the winter seasons from 1997 to 2003. Distributed snow depth was mapped by overlapping between snow cover maps and interpolated snowfall maps from 69 meteorological observation station. Depletion curves of snowmelt area were described from the linear regression equations of each year between the average temperature and snow cover area in Soyanggang-dam and chungju-dam watershed.

Development and Application of Paddy Storage Estimation Model During Storm Periods

The hydrologic behavior of paddy field depends largely on the irrigation and levee height management by farmers. The storage and drainage amount of paddy for storm events certainly influences the stream discharge. To understand the paddy storage effect during storm periods, a daily paddy water balance model embedding farmer`s water management was developed by using 4 years (1996, 1997, 2001, 2002) field experimental data at 2 locations (Suwon and Yeoju) From the modeling, it was possible to simulate the daily ponding depth of paddy by treating paddy levee height and threshold pending depth indicating irrigation time as 10 days average parameters of the model. The storage amount(306.9 mm to 343.6 mm) showed little deviation to rainfall amount(425.1 mm to 850.8 mm).

Climatic Water Balance Analysis Using NOAA/AVHRR Satellite Images

The purpose of this study was to analyze the climatic water balance of the Korean peninsula using meteorological data and the evapotranspiration (ET) derived from NOAA/AVHRR, Quantifying water balance components is important to understand the basic hydrology, In this study, a simple method to estimate actual ET was proposed based on a regression approach between NDVI and Morton`s actual ET using NOAA/AVHRR data, The Mortons actual ET for land surface conditions was evaluated using a daily meteorological data from 77 weather stations, and the monthly averaged Morton`s ETs for each land cover was compared with the monthly NDVIs during the year 2001. According to the climatic water balance analysis, water deficit and surplus distributed maps were created from spatial rainfall, soil moisture, and actual and potential ETs map, The results clearly showed that the temporal and spatial characteristics of dryness and wetness may be detected and mapped based on the wetness index.

Estimation of Monthly Actual Evapotranspiration Using NOAA-AVHRR Satellite Images

The purpose of this study is to estimate monthly evapotranspiration (ET) using normalized difference vegetation index (NDVI) obtained from NOAA-AVHRR data sets. Actual evapotranspiration was evaluated by the complementary relationship, and monthly NDVI was obtained by maximum value composite method from daily NDVI images in the Korean peninsula for the year 2001 The monthly actual ETs for each land cover were compared with the monthly NDVIs to determine relationships between actual ET and NDVI for each land cover category, There was a high correlation between monthly NDVI and monthly mean actual ET. This study presents an alternative approach for land surface evapotranspiration based on remote sensing techniques.

Development of Crop Information System using Satellite Images

A computer system for crop information was developed using Visual Basic and ArcGIS VBA. The system is operated on ArcGIS 8.3 with Microsoft Access MDB. Landsat +ETM, KOMPSAT-1 EOC, ASTER VNIR and IKONOS panchromatic (Pan) and multi-spectral (MIS) images were included in the system to extract agricultural land use items identifiable at various spatial resolutions of images. Agriculture related data inventories using crop cover information such as texture and average pixel value of each band based on crop cultivation calendar were designed and implemented. Three IKONOS images were loaded in the system to show crop cover characteristics such as rice, pear, grape, red pepper, garlic, and surface water cover of reservoir with field surveys. GIS layers such as DEM (Digital Elevation Model), stream, road, soil, land use and administration boundary were prepared to understand the related characteristics and identify the location easily.