• Journal of the Korean Association of Geographic Information Studies
• /
• v.21 no.4
• /
• pp.50-63
• /
• 2018

The rapid urbanization had led to a distortion of natural hydrological cycle system. The change in hydrological cycle structure is causing streamflow depletion, changing the existing use tendency of water resources. To manage such phenomena, a streamflow depletion impact assessment technology to forecast depletion is required. For performing such technology, it is indispensable to build GIS-based spatial data as fundamental data, but there is a shortage of related research. Therefore, this study was conducted to use the use of GIS-based time series spatial data for streamflow depletion assessment. For this study, GIS data over decades of changes on a national scale were constructed, targeting 6 streamflow depletion impact factors (weather, soil depth, forest density, road network, groundwater usage and landuse) and the data were used as the basic data for the operation of continuous hydrologic model. Focusing on these impact factors, the causes for streamflow depletion were analyzed depending on time series. Then, using distributed continuous hydrologic model based DrySAT, annual runoff of each streamflow depletion impact factor was measured and depletion assessment was conducted. As a result, the default value of annual runoff was measured at 977.9mm under the given weather condition without considering other factors. When considering the decrease in soil depth, the increase in forest density, road development, and groundwater usage, along with the change in land use and development, and annual runoff were measured at 1,003.5mm, 942.1mm, 961.9mm, 915.5mm, and 1003.7mm, respectively. The results showed that the major causes of the streaflow depletion were lowered soil depth to decrease the infiltration volume and surface runoff thereby decreasing streamflow; the increased forest density to decrease surface runoff; the increased road network to decrease the sub-surface flow; the increased groundwater use from undiscriminated development to decrease the baseflow; increased impervious areas to increase surface runoff. Also, each standard watershed depending on the grade of depletion was indicated, based on the definition of streamflow depletion and the range of grade. Considering the weather, the decrease in soil depth, the increase in forest density, road development, and groundwater usage, and the change in land use and development, the grade of depletion were 2.1, 2.2, 2.5, 2.3, 2.8, 2.2, respectively. Among the five streamflow depletion impact factors except rainfall condition, the change in groundwater usage showed the biggest influence on depletion, followed by the change in forest density, road construction, land use, and soil depth. In conclusion, it is anticipated that a national streamflow depletion assessment system to be develop in the future would provide customized depletion management and prevention plans based on the system assessment results regarding future data changes of the six streamflow depletion impact factors and the prospect of depletion progress.

• Spatial Information Research
• /
• v.20 no.3
• /
• pp.39-50
• /
• 2012

The objective of this study is the quantitative analysis of climate change effects by performing several statistical analyses with hydrometeorological data sets for past 30 years in Geum river watershed. Temperature, precipitation, relative humidity data sets were collected from eight observation stations for 37 years(1973~2009) in Geum river watershed. River level data was collected from Gongju and Gyuam gauge stations for 36 years(1973~2008) considering rating curve credibility problems and future long-term runoff modeling. Annual and seasonal year-to-year variation of hydrometeorological components were analyzed by calculating the average, standard deviation, skewness, and coefficient of variation. The results show precipitation has the strongest variability. Run test, Turning point test, and Anderson Exact test were performed to check if there is randomness in the data sets. Temperature and precipitation data have randomness and relative humidity and river level data have regularity. Groundwater level data has both aspects(randomness and regularity). Linear regression and Mann-Kendal test were performed for trend test. Temperature is increasing yearly and seasonally and precipitation is increasing in summer. Relative humidity is obviously decreasing. The results of this study can be used for the evaluation of the effects of climate change on water resources and the establishment of future water resources management technique development plan.

• Journal of Korea Water Resources Association
• /
• v.53 no.3
• /
• pp.193-200
• /
• 2020

Hydrological drought is directly associated with lack of available water in rivers, reservoirs, and groundwater. It is important to analyze hydrological drought for efficient water resource management because most of rainfall is concentrated in wet seasons and water supply is highly dependent on dams and reservoirs in South Korea. Generally, a threshold level method is useful for defining hydrological droughts. However, this method causes interdependent problems between drought events which result in skewed results in further statistical analysis. Therefore, it is necessary to determine a proper threshold level to represent regional drought characteristics. In this study, applying 50~99 percentiles of daily flow-duration curve, hydrological drought events were extracted, and independence tests were conducted for 12 watersheds. The Poisson independence test showed that 87~99 percentiles were available for most stations except for Yeoju and Pyeongtaek. The generalized Pareto independence test showed that 80~90 percentiles were the most common. Mean excess plot showed that 80 ~ 90 percentiles were the most common. Therefore, the common ranges of the three independent tests were determined for each station and proper threshold levels were recommended for large river basins; 70~76 percentiles for the Han River basin, 87~91 percentiles for the Nakdong River basin, 86~98 percentiles for the Geum River basin, and 85~87 percentiles for the Youngsan and Seomjin River basin.

• Journal of Soil and Groundwater Environment
• /
• v.14 no.2
• /
• pp.1-9
• /
• 2009

This study was objected to identify the effect on water quality and contamination by non-agricultural facilities in 'A' reservoir watershed located in OO city, Kyounggi-do, Korea. Ground- and stream water samples showed (Na+K)-Cl, Ca(Cl, SO$_4$) and Ca-Cl type in an illegally discharging area of sewage and a densely industrial area indicating water contamination. Stream water of an illegally discharging area of sewage had high COD, T-N and T-P. In this area, direct incoming of sewage into stream water was induced ground water system by well pumping, and it made a progress of ground water contaminations with those components. Groundwater of a densely industrial area showed high concentrations of T-N, NO$_3$N. From a nitrogen isotope analysis, stream water of an illegally discharging area of sewage has ${\delta}^{15}N-NO_3$values of 0.7%0 was strongly affected by nitrogen originated from agrochemicals, and a densely industrial area of 19.7%0 from septic system. Ground- and stream water of a livestock fanning area were contaminated with NH$_3$-N and Mn, which was affected by intensive livestock facilities. SAR-conductivity plot indicates the water does not pose either alkalinity or salinity hazard for irrigation. COD, T-N, T-P, NO$3$-N, NH$_3$N and Mn concentrations from contaminated areas were diminished by mixing with 'A' reservoir water. There were no water contaminations in silver towns, vacationlands around reservoir and golf links. Consequently, it should be made a plan of systematic managements for past and- present possible contaminants and sewage systems in preventing water contamination by non-agricultural facilities.

• Korean Journal of Environment and Ecology
• /
• v.26 no.4
• /
• pp.498-511
• /
• 2012

Mountainous wetland have many species such as II grade endangered species of wild flora and fauna(Drosera rotundifolia) and environmental indicator species(Utricularia racemosa, Habenaria linearifolia, Parnassia palustris, Molinia japonica, etc.). Accordingly, the mountainous wetlands is very important. However, most mountainous wetlands will disappear by natural or artificial aridness processes. Thus, it needs to manage mountainous wetland for protecting from aridness. This study has found out the wetland status of the environmental ecology and aridness processes moreover, it has suggested ways of improving wetland conservation plan and wetland aridness management plan. According to the results of topography structure survey, Hwaeom wetland's altitude is ranged within 750~810m(87.4%), and slope is less than $10^{\circ}$. There was ideally suited mountainous wetland. However, the water supply(1.6 meters depth and 0.8 meters wide) was built on under the wetland. For that reason, there was concerned about the aridness processes by sweeping away peat layer and dropping the water level. The distribution area of hygrophyte was narrowed to 6.7% whereas, woody plants and xerophytic plants was achieved a dominant position. If it leaves the situation as it is, the mountainous wetland will be developed next succession as forest ecosystem. Therefore, in order to sustain the mountainous wetland from aridness, it is set to the base direction of conservation and management as main schemes. Moreover, we have suggested that setting the vegetation conservation and management area which considering a ecological vegetation characteristics, managing the ecotone vegetation, setting the buffer zone for protection of ecological core areas, protecting the mountainous wetland indicator species and designating the management vegetation. In conclusion, in order to sustain and maintain a soundly wetland ecosystem, it needs to several management of wetlands damage factors. 1) suppression of the excessive groundwater to basin, 2) stabilization of wetland via hydrologic storage, 3) suppression of changing and transforming wetland into forest by succession via management of xerophytic plants.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.1
• /
• pp.113-118
• /
• 2010

Due to diverse soil-forming environments and different purposes of the soil classification, numerous soil classification systems have been developed worldwide. The World Reference Base for Soil Resources (WRB) and the Soil Taxonomy of the United States are well-known in Korea. However, the German Soil Systematics based on somewhat different principles from the two former systems is little-known. The objective of this paper is therefore to give a short overview of the principles of the German Soil Systematics. The German Soil Systematics consists of a six-level hierarchical structure which comprises soil divisions, soil classes, soil types, soil subtypes, soil varieties, and soil subvarieties. Soils in Germany are firstly classified into one of four soil divisions according to the soil moist regime: terrestrial soils, semi-terrestrial soils, semi-subhydric/subhydric soils, and peats. Terrestrial soils are subdivided into 13 soil classes based on the stage of soil formation and the horizon differentiation. Semi-terrestrial soils are differentiated into four classes regarding the source of soil moist: groundwater, freshwater, saltwater, and seaside. Semi-subhydric/subhydric soils are subdivided into two classes: semi-subhydric and subhydric soils. Peats are classified into two classes of natural and anthropogenic origins. Classes can be compared to orders of the U.S. Taxonomy. Classes are subdivided into 29 soil types with regard to soil forming-processes for terrestrial soils, into 17 types with regard to the soil formation for semi-terrestrial soils, into five types with regard to the content of organic matter for semi-subhydric/subhydric soils, and also into five types with regard to peat-forming processes for peats. The soil mapping units in Germany are types, which can be additionally subdivided into ca. 220 subtypes, several thousands of varieties and subvarieties using detailed nuances of morphologic features of soil profile. Soil types can be compared to great groups of the U.S. Taxonomy.

• Journal of Soil and Groundwater Environment
• /
• v.10 no.1
• /
• pp.43-57
• /
• 2005

Twelve bottom sediments and three cores were collected in Juam reservoir for a study on transportation, which was controlled by particle grain size (2mm-200{\mu}m,\;200-100{\mu}m,\;100-50{\mu}m,\;50-20{\mu}m,\;<20{\mu}m), and vertical distribution of heavy metals. Sediment cores were sliced into 2 to 5 cm intervals to measure heavy metal concentrations in interstitial water and sediments with depth. Pb isotopic compositions of core samples were determined to calculate sedimentation rate. Regardless of sampling sites, levels of heavy metals and trace elements in bottom sediments are nearly constant with mean values of $14.9\;{\mu}g/g\;for\;As,\;0.81{\mu}g/g\;for\;Cd,\;30.7{\mu}g/g\;for\;Cu,\;34.7{\mu}g/g\;for\;Ni,\;63.3{\mu}g/g\;for\;Pb\;and\;87.9{\mu}g/g\;for\;Zn$. In general, Cu, Pb, Zn, Wi, and Cr in fraction of $<20{\mu}m$ exhibit the highest concentration, but content of As is the highest in grain size of $2\;mm-200\;{\mu}m$ and $200-100\;{\mu}m$. Fe and Mn occur as the dissolved compositions of the highest concentrations in interstitial waters and increase in their concentrations toward lower part of cores. On the contrary, concentrations of Zn and Cu show the highest value in the uppermost part in cores, suggesting these elements are released from reductive dissolution of hydroxides and oxidation of organic matters under different redox conditions. The highest accumulations of Cu, Ni, Pb, and Zn contents in the sediment cores are observed at 0-4 cm layers, and concentrations of Cu and Pb are especially high, implying these heavy metals are originated from anthropogenic sources. The apparent sedimentation rate estimated using unsupported $^{210}Pb$ is 0.91 cm $year^{-1}$, corresponding about 10 cm sedimentation in total depth since construction of Juam dam. These results will provide available information for management of bottom sediment in Juam reservoir.

• Journal of Korea Water Resources Association
• /
• v.46 no.12
• /
• pp.1193-1207
• /
• 2013

Increase of impervious area caused by overdevelopment has led to increase of runoff and then the problem of flooding and NPS were brought up. In addition, as decrease of base flow made groundwater level to decline, a stream that dries up is issued. low impact development (LID) method which is possible to mimic hydrological water cycle, minimize the effect of development, and improve water cycle structure is proposed as an alternative. As introduction of LID in domestic increases, the study on small watershed is in process mainly. Also, analysis of property of hydrological runoff and load on midsize watershed, like sewage treatment district, is required, the study on it is still insufficient. So, area applying LID practices from watershed of Dongrae stream is pinpointed and made the ratio and then expand it to watershed of Oncheon stream. Among low impact development practices, Green Roof, Porous Pavement, and Bio- retention are selected for the application considering domestic situations and simulated with SWMM-LID model of each watershed and improvement of water cycle and reduction of non-point pollution loads was analysed. Improvement of water cycle and reduction of non-point pollution loads were analyzed including the property of rainfall and soil over long term simulation. The model was executed according to scenario based on combination of LID as changing conductivity in accordance with soil type of the watershed. Also, this study evaluated area of LID application that meets the efficiency of conventional management as a criteria for area of LID practices applying to sewer treatment district by comparing the efficiency of LID application with that of conventional method.

• Journal of Korea Water Resources Association
• /
• v.54 no.11
• /
• pp.875-889
• /
• 2021

This study compares and analyzes the Soil and Water Assessment Tool (SWAT) and Terra MODIS (Moderate Resolution Imaging Spectroradiometer) as coniferous, deciduous and mixed forest with Yongdam Dam upstream (904.4 km²). The hydrologic evaluation period was set to 10 years from 2010 to 2019, and the applicability of the 8-day MOD15A2 Leaf Area Index (LAI) data, 3 TDR (Time Domain Reflectometry) (GB, JC, CC), and 1 Flux Tower (DU) evaporation volume (YDD) data was simulated. As a result, the R² of coniferous forest, deciduous forest and mixed forest are 0.95, 0.89, 0.90, soil moisture and evaportranspiration stations R² were analyzed at 0.50 to 0.55 and 0.51, respectively, with R² at 0.74, RMSE 2.75 mm/day, NSE 0.70 and PBIAS 14.3% for Yongdam inflow. Based on the calibrated and validated watersheds, the annual average evaportranspiration was calculated as coniferous 469.7 mm, deciduous 501. mm and 511.5 mm mixed forest, total runoff were estimated at coniferous 909.8 mm, deciduous 860.6 mm and 864.2 mm mixed forest. In the case of annual average evaportranspiration, it was evaluated that deciduous were high, but in the case of streamflow, it was evaluated that coniferous were high. Unlike other hydrologic with similar patterns throughout the year, the average annual evapotranspiration was about 7% higher than coniferous due to the higher evapotranspiration of deciduous with high leaf area index in summer and fall. In addition, deciduous were 9% and 6% higher for surface runoff and lateral flow, but the groundwater of coniferous was 77% higher. Therefore, it was confirmed that the total runoff was in order of coniferous, mixed forest, and deciduous.