• Korean Journal of Soil Science and Fertilizer
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• v.30 no.3
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• pp.209-225
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• 1997

Daily rainfalls and evaporations from copper pan measured in Suweon from 1964 to 1996 were figured respectively so that past soil moisture deficits can be understood clearly at a glance in relation to the characteristics of weather. Past drought intensities in Suweon were computed on the basis of Oh's 50mm pan model estimating drought in terms of daily, monthly shortage of evapotranspiration and growthless time fraction. Yearly differences in drought seem to result mainly from yearly differences in rainfall distribution and intensity, because there is the periodical similarity in evaporation from year to year. The most intense drought continued from December, 1964 to June, 1965 for 190 days and the most frequent rainfalls were observed from June, 1989 to August, 1990 for 15 months. The applied Oh's drought estimation model was reinforced with figuring programs with a view to later application for other districts. Present economic value index of irrigation were distributed in the range of 120% to 210% of one season yield for spring chinese cabbage, calculated on the basis of 10 year's accumulation of its expectable future yield increase. Therefore, the same value can be invested for the installation of new irrigation system even only for spring chinese cabbage, if its depreciation period is 10 years.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.8-14
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• 2007

Water quality in Lake Rotorua, New Zealand, deteriorated since the 1960s because of excessive phytoplankton growths due principally to increasing nitrogen and phosphorus in the lake waters. Nutrient concentrations in eight of the nine major streams feeding Lake Rotorua have increased since 1965. The groundwater system has a key role in the hydrology of the Lake Rotorua catchment and the groundwater system is probably the control on the time delay between intensification of agricultural land use and response of surface water quality. All major, and many minor streams, in the catchment are fed by springs. Two lithological units are most important to groundwater flow in the Lake Rotorua catchment: Mamaku Ignimbrite, erupted in about 200,000 years ago and Huka Formation sediments which filled the caldera left by the Mamaku Ignimbrite eruption. Rainfall recharge to groundwater in the groundwater catchment of Lake Rotorua is estimated as approximately 17300 L/s. A calibrated steady-state groundwater flow model estimates that approximately 11100 L/s of this flow discharges into streams and then into the lake and the balance travels directly to Lake Rotorua as groundwater discharge through the lake bed. Land use has impacted on groundwater quality. Median Total Nitrogen (TN) values for shallow groundwater sites are highest for the dairy land use (5.965 mg/L). Median TN values are also relatively high for shallow sites with urban-road and cropping land uses (4.710 and 3.620 mg/L, respectively). Median TN values for all other uses are in the 1.4 to 1.5 mg/L range. Policy development for Lake Rotorua includes defining regional policies on water and land management and setting an action plan for Lake Rotorua restoration. Aims in the action plan include: definition of the current nutrient budget for Lake Rotorua, identification of nutrient reduction targets and identification of actions to achieve targets. Current actions to restore Lake Rotorua water quality include: treatment of Tikitere geothermal nitrogen inputs to Lake Rotorua, upgrade of Rotorua City sewage plant, new sewage reticulation and alum dosing in selected streams to remove phosphorus.

• Journal of Environmental Impact Assessment
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• v.20 no.2
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• pp.107-121
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• 2011

To assess the impact of climate change on water quality in an impounded river basin, this study estimated future air temperature and rainfall in the years of 2020, 2050 and 2080 by statistically downscaling the simulation results from two GCM models combined with two emission scenarios (A2 and B1). Both scenarios were selected from the Special Report on Emission Scenarios (SRES) suggested by IPCC. The A2 scenario represents an extreme condition whereas the B1 scenario represents a clean and energy efficient condition which is similar to that of study basin. With the results of estimated climate factors and land use data, the discharge and the concentrations of BOD, TN and TP in the Andong dam basins were simulated using the SWAT model. The change in BOD concentration for the B1 emission scenario was greater than the A2 scenario in the annual increase range and the pollution level. The concentration of TN was decreased during March? June which is drought period and increased again afterward. In contrast to TN, the concentration of TP was generally decreased. The change in TP concentration was greater for the B1 scenario than the A2 scenario.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.147-156
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• 2003

In this research, multiple corrosion factors of buried environments were measured in order to establish a formula for the corrosion character of corrugated steel structures in domestic environments. By substituting corrosion factors for each predicting formula, the durable lifetime was measured, and the measured lifetime was compared with the estimated lifetime by applying existing thickness-measuring techniques. A new usage standard was proposed with these results, in order to create the conclusion below. There are known differences in the soil factors used as variables in estimating the duration caused by the seasonal effects of rainfall and temperature. Comparing the durable lifetime estimated by each predicting formula, the findings show that the California technique is conservative. This study demonstrates that the error range of the AISI technique, which is mostly used as a duration technique, is a very narrow predicting technique as compared with many other countries. Considering that there is on average, a 13% error margin in this study, a proposed safety factor of 0.87 could be used to more accurately predict the duration. The laying time in the California technique is not longer than the whole durability, and as a result, this error margin exists. It is concluded that this study on the open area has been overdue. Based on these findings, it's proposed that this error margin should be applied to the domestic environment through periodic observation, in order to establish the predicting techniques of durable lifetime.

• Journal of Korean Society on Water Environment
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• v.24 no.5
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• pp.550-555
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• 2008

This study was conducted to assess the growth characteristics of phytoplankton and to understand seasonal dynamics of phytoplankton in response to limiting nutrients in an agricultural reservoir from November 2002 to December 2003. Marked increase of chl.a concentration observed in July ($99.0{\mu}g/L$) and November ($109.7{\mu}g/L$) after heavy rainfall. TP concentration ranged $48.0{\sim}126.6{\mu}g/L$, and its the temporal variation was similar to that of chl.a concentration. Microcystis spp., dominant phytoplankton species were used for the growth kinetics experiment, except for the season when Aulacoseira spp. (March, April) and Aphanocapsa sp. (May) dominated. In the temperature range between $10{\sim}25^{\circ}C$, the rate of growth increase per $10^{\circ}C$ was almost two folds. The highest maximum growth rate (${\mu}_{max}=1.09day^{-1}$) of phytoplankton observed September, and ${\mu}_{max}$ was lowest ($0.34day^{-1}$) in March when Aulacoseira spp. dominated. The ${\mu}_{max}$ ($0.78{\pm}0.20day^{-1}$) was relatively high in the summer season when water temperature is above $20^{\circ}C$ and cyanobacteria dominated compared to the spring when diatoms dominated ($0.43{\pm}0.08day^{-1}$). The maximum growth rate ($0.55{\pm}0.12day^{-1}$) and the half saturation concentration ($K_s=0.73{\pm}0.15{\mu}M$) of cyanobacteria during winter season (November, December) was higher than those of diatoms. However, the ${\mu}_{max}$ and $K_s$ of cyanobacteria in December was similar to those of diatom, reflecting that diatom cell quota (Mean 48.4 pgP/cell) was greater than cyanobacteria (34.0 pgP/cell) during this time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.155-161
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• 2018

Many short range weather radars with the low elevation search capability are needed for analysis and prediction of unusual weather changes or rainfall phenomena which occurs regionally. However, due to the characteristics of low elevation electromagnetic wave beam, it is highly probable that the received weather signals of these radars are contaminated by the ground and sea clutter. Since most of ground clutter appears around the very narrow low Doppler frequency region, it is somewhat easy to separate. However, the sea clutter removal is very difficult since it can occupy the broad Doppler frequency region according to weather conditions. Therefore, in this paper, the sea clutter removal capability is analyzed for a phased array weather radar which use vertical array elements for electronic elevation beam steering. Also, it is shown that the sea clutter removal can be achieved appropriately using the receiver beam forming technology in a phased array antenna.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1079-1083
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• 2010

Due to summer rainfall is concentrated in the construction of the reservoir and the dam was inevitable. The character of these structures are different from the common rivers have been characterized. According to this problem, we need to adopt to this area with three dimensional model. Construction of dams for preservation of land, utilization of water resources, and exploitation of energy potential, which is a basic element of countries' development, is regarded as indispensable for peoples. In addtion, the development of the Nakdong River nutrient and pathogen Total Maximum Daily Loads (TMDL) required that the full range of pollutants, sources, and flow conditions, typical of heavily urbanized areas, be addressed for a single water body with 1-D simulation model (river) and 3-D simulation model (reservoir). The objective of this study is to simulate the applicability of reservoir with the coupling of 3-D hydrodynamic and water quality models to estimate water balance and pollutant loading in Namgang Dam(Jinyang reservoir).

• Korean Journal of Agricultural and Forest Meteorology
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• v.10 no.4
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• pp.167-176
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• 2008

Airborne pollen is known as one of the major causal agents to respiratory allergic reactions. Daily number of pollen grains was monitored using Burkard volumetric spore traps at seven locations including Seoul and Jeju during 1997-2007. Pollen grains were observed throughout the year especially from February to November. They showed similar distribution patterns of species among locations except in Jeju, where Japanese cedar vegetation is uniquely found. Peak seasons for pollen grains from trees and weeds were March to May and August to October, respectively. Tree pollens were mainly composed of pine, oak, alder, and birch. Weed pollens were mainly from Japanese hop, Worm wood, and ragweed. Diameter of pollen grains, which has a typical range of $20{\sim}60{\mu}m$, has close relationship with allergenicity. Allergenicity of tree and weed pollens is higher than that of grass pollens in general. In the case of trees and shrubs, pine trees account for about 70% of all tree pollens. However, pine pollens are weak allergens. The remaining 30% of tree pollens, including alder trees, white birches, and oaks, are moderate to strong allergens despite the smaller numbers. Grass and weeds are also highly likely to cause allergies. Especially, the pollens of Wormwood and Japanese hop are highly likely to cause allergies. Daily fluctuations in the number of pollens have to do with a variety of meteorological factors, such as temperature and rainfall.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.637-647
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• 2014

Quantitative assessment of groundwater level change under extreme event is important since groundwater system is directly affected by drought. Substantially, groundwater level fluctuation reveals to be delayed from several hours to few months after raining according to the aquifer characteristics. Groundwater system in Jeju Island would be also affected by drought and almost all regions were suffered from a severe drought during summer season (July to September) in 2013. To estimate the effect of precipitation to groundwater system, monthly mean groundwater levels in 2013 compared to those in the past from 48 monitoring wells belong to be largely affected by rainfall(Dr) over Jeju Island were analyzed. Mean groundwater levels during summer season recorded 100 mm lowered of precipitation compared to the past 30 years became decreased to range from 2.63 m to 5.42 m in southern region compared to the past and continued to December. These decreasing trends are also found in western(from -1.21 m to -4.06 m), eastern(-0.91 m to -3.24 m), and northern region(from 0.58 m to -4.02 m), respectively. Moreover, the response of groundwater level from drought turned out to be -3.80 m in August after delaying about one month. Therefore, severe drought in 2013 played an important role on groundwater system in Jeju Island and the effect of drought for groundwater level fluctuation was higher in southern region than other ones according to the regional difference of precipitation decrease.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.65-73
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• 2012

Soil-rock interface, mainly founded in Granite region of Korea, is known as one of the important factor of the slope failure at the rainfall due to smaller shear strength than soil itself. However, research of the effect on slope stability by soil-rock interfaces is insufficient. Therefore, a series of direct shear tests were performed in order to investigate the effect of soil-rock interface on slope stability. The method of tests is to get sand itself and sand-artificial rock interface shear strength from different grain size of sands and artificial rock samples. The results of tests show that the friction angle of interface depends primarily on particle size and surface roughness. Interface friction angle ratio ${\mu}(={\delta}/{\Phi})$ is in the range of 0.75 ~ 0.96, this results indicate that interface friction angle is smaller than sand itself.