• Journal of Korea Water Resources Association
• /
• v.49 no.2
• /
• pp.107-119
• /
• 2016

Since future climate scenarios indicate that extreme precipitation events will intensity, probable maximum precipitations (PMPs) without being taken climate change into account are very likely to be underestimated. In this study future PMPs in accordance with the variation of future rainfall are estimated. The hydro-meteorologic method is used to calculate PMPs. The orographic transposition factor is applied in place of the conventional terrain impact factor which has been used in previous PMPs estimation reports. Future DADs are indirectly obtained by using bias-correction and moving-averaged changing factor method based on daily precipitation projection under KMA RCM (HEDGEM3-RA) RCP 8.5 climate change scenario. As a result, future PMPs were found to increase and the spatially-averaged annual PMPs increase rate in 4-hour and $25km^2$ was projected to be 3 mm by 2045. In addition, the increased rate of future PMPs is growing increasingly in the future, but it is thought that the uncertainty of estimating PMPs caused by future precipitation projections is also increased in the distant future.

• Journal of Korea Water Resources Association
• /
• v.31 no.6
• /
• pp.795-806
• /
• 1998

Soil moisture is affected by regional climate, soil characteristics and land surface condition, etc,. Especially, the changes in land surface condition is more than other factors, which is mainly due to rapid urbanization and industrialization. This study is to evaluate how the change of land surface condition impacts on soil moisture field evolution using a simple model of soil moisture dynamics. For the quantification of soil moisture field, the first half of the paper is spared for the statistical characterization based on the first- and second-order statistics of Washita '92 and Monsoon '90 data. The second half is for evaluating the impact of land cover changes through simulation study using a model for soil moisture dynamics. The model parameters, the loss rate and the diffusion coefficient, have been estimated using the observed data statistics, where the changes of surface conditions are considered into the model by applying various parameter sets with different second-order statistics. This study is concentrated on evaluating the impact due to the changes of land surface condition variability. It is because we could easily quantify the impact of the changes of its areal mean based on the linear reservoir concept. As a result of the study, we found; (1)as the variability of land surface condition, increases, the soil moisture field dries up more easily, (2)as the variabilit y of the soil moisture field is the highest at the beginning of rainfall and decreases as time goes on to show the variability of land surface condition, (3)the diffusion effect due to surface runoff or water flow through the top soil layer is limited to a period of surface runoff and its overall impact is small compared to that of the loss rate field.

• Journal of Korean Society of Forest Science
• /
• v.102 no.2
• /
• pp.176-181
• /
• 2013

The impacts of habitats changes of benthic macroinvertebrae species and individuals of the torrents due to construction of torrent structures can be summarized as follows. Approximately 16 to 40 species and 352 to 4,333.3 individuals of benthic macroinvertebrae were found around the local position of the torrent structures. Construction of torrential structures can increases the stability in the riverbed by preventing vertical corrosion and reducing the flow rate. However, if pond is created due to increase flow rate of rainfall, the temporal confusion of micro-habitats may lead to decrease in the number of species and induce reduced number of diversity as well as cause simplification in the community structure. Therefore, erosion control structures in torrent cause influence on the habitual ecosystem, though there are differences in the degree per distance depending on the types and heights of the structure. Before establishing torrent erosion control structure in mountainous torrent area, ecosystem status should be studied carefully from the planning stage and torrent habitats should be protected by deciding type, height and scale of structure, to minimize the influence on local habitants.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.8 no.1
• /
• pp.1011-1034
• /
• 1966

This thesis is the final report which has long been studied by the author to obtain the design basis for various hydrological constructions with the specific system suitable to the natural environmental conditions in Korea. This report is divided into two parts: one is to estimate runoff volume from watersheds and the other to estimate the peak discharge for a single storm. According to the result of observed runoff record from watersheds, it is known that Kajiyama formula is useful instrument in estimating runoff volume from watersheds in this country. But it has been found that this formula shows us 20-30% less than the actual flow. Therefore, when wihed to bring a better result, the watershed characteristics coefficient in this formula, that is, f-value, should be corrected to 0.5-0.8. As for the method to estimate peak discharge from drainage basin, the author proposes to classify it in two ways; one is small size watershed and the other large size watershed. The maximum -flood discharge rate $Q_p$ and time to peak Pt obtained from the observed record on the small size watershed are compared by various methods and formulas which are based upon the modern hydrological knowledge. But it was fou.d that it. was not a satisfied result. Therefore, the author proposes. tocomputate $Q_p$, to present 4.0-5.0% for the total runoff volume ${\Sigma}Q$.${\Sigma}Q$ is computed under the assumption of 30mm 103s in watershed per day and to change the theoritical total flow volume to one hour dura tion total flow rate when design daily storm is given. Time to peak Pt is derived from three parameters which are u,w,k. These are computed by relationship between total runoff volume (ha-m unit)and $Q_p$. (C.M.S. unit). Finally, the author checked out these results obtained from 51 hydrographs and got a satisfied result. Therefore the author suggested the model of design dimensionless unit-hydrograph. And the author believes that this model will be much available at none runoff record river site. In the large size watersheds in Korea when the maximum discharge occurs, the effective rainfall is two consequtive stormy days. So the loss in watershed was assutned as 6Omm/2days,and the author proposed 3-hour-daration hydrograph flow distribution percentage. This distribution percentage will be sure to form the hydrograph coordinate.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.11 no.4
• /
• pp.135-142
• /
• 2009

In order to predict frostfall, nocturnal cooling rate and air temperature changes were analyzed on days with and without frost when the maximum temperature was lower than $20^{\circ}C$. In general, the nocturnal cooling rates on frosty days were higher than those on non-frosty days. The cooling rates averaged from 19:00 to 24:00 on frosty and non-frosty days were $1.7^{\circ}Ch^{-1}$ and $0.7^{\circ}Ch^{-1}$ respectively. As expected, the nocturnal temperature on frosty days was lower than that on non-frosty days. Especially, the midnight air temperature averaged about $3.9{\pm}1.5^{\circ}C$ on frosty days, which was lower than that on non-frosty days (i.e., $10.1{\pm}2.9^{\circ}C$). The discriminant analysis using three independent variables (i.e., total cloud amount, air temperature at 24:00, and 5-day rainfall amount) successfully classified the presence of frost with 87% accuracy.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.23 no.4
• /
• pp.221-232
• /
• 2021

Most of measurement sensors used for maintenance are continuously exposed to various environmental factors such as transportation and rainfall, so the possibility of breakage increases gradually. The maintenance measurement sensor of domestic subway tunnel shows an average of 14.2% to 14.8% of loss rate after about 5 to 6 years from installation, and it shows a sensor loss rate of about 13.9% in case of foreign countries. As a result, it can be seen that an average of 15% of maintenance measurement sensors at home and abroad cannot send measuring values after 5~6 years. In order to continuously collect accurate data, measurement data must be recovered by performing repair or replacement of the sensor, but some lost measurement sensors are buried after installation. So, there are many difficulties in repairing sensors, including cost and time. Therefore, in this paper, we propose lost measurement sensor data estimation technology based on data trend analysis using adjacent sensors.

• Journal of Korea Water Resources Association
• /
• v.52 no.1
• /
• pp.71-82
• /
• 2019

The purpose of this study is to analyze the Mekong River streamflow alteration due to climate change. The future climate change scenarios were produced by bias corrections of the data from East Asia RCP 4.5 and 8.5 scenarios, given by HadGEM3-RA. Then, SWAT model was used for discharge simulation of the Kratie, the main point of the Mekong River (watershed area: $646,000km^2$, 88% of the annual average flow rate of the Mekong River). As a result of the climate change analysis, the annual precipitation of the Kratie upper-watershed increase in both scenarios compared to the baseline yearly average precipitation. The monthly precipitation increase is relatively large from June to November. In particular, precipitation fluctuated greatly in the RCP 8.5 rather than RCP 4.5. Monthly average maximum and minimum temperature are predicted to be increased in both scenarios. As well as precipitation, the temperature increase in RCP 8.5 scenarios was found to be more significant than RCP 4.5. In addition, as a result of the duration curve comparison, the streamflow variation will become larger in low and high flow rate and the drought will be further intensified in the future.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.3
• /
• pp.541-550
• /
• 2021

While open-air compost has value as a source of nutrients for crops in agricultural land, it acts as a pollution that adversely affects the environment during rainfall, and management is required. In this study, it was intended to analyze the accuracy of calculating open-air compost volume using fixed-wing UAV (unmanned aerial vehicle) capable of acquiring a wide range of images and automatic path flights and to identify the possibility of utilization. In order to evaluate the accuracy of calculating the three open-air compost volume, ground LiDAR surveys and precision surveys using a rotary UAV were performed. and compared with the open-air compost volume acquired through a fixed-wing UAV. As a result of comparing the calculation of open-air compost volume based on the ground LiDAR, the error rate of the rotary-wing was estimated to be ±5%, and the error rate of fixed-wing was -15 ~ -4%. one of three open-air compost volume calculated by fixed-wing was underestimated as about -15 %, but the deviation of the open-air compost volume was 2.9 m3, which was not significant. In addition, as a result of periodic monitoring of open-air compost using fixed-wing UAV, changes in the volume of open-air compost with time could be confirmed. These results suggested that efficient open-air compost monitoring and non-point pollutants in agricultural for a wide range using fixed-wing UAV is possible.

• Journal of Mushroom
• /
• v.21 no.1
• /
• pp.22-32
• /
• 2023

To investigate the effect of thinning intensity on environmental factors and ectomycorrhizal mushroom fruiting in forest ecosystems, we studied canopy closure, throughfall, soil temperature, soil moisture, light response of understory vegetation, and ectomycorrhizal mushroom fruiting in a 10-year-old pine forest after 34%, 45%, and 60% thinning. Canopy closure was significantly higher in the 34% treatment and control plots, ranging from 80-85% in April. However, in November, all thinning treatment plots showed a decrease of approximately 5-10% compared with the control plot. The 60% treatment plot had over 200 mm of additional throughfall compared with the control plot, and monthly throughfall was significantly higher by more than 100 mm in October. The soil temperature in each treatment plot increased significantly by up to 1℃ or more compared with the control plot as the thinning rate increased. The soil moisture increased by more than 5% in the thinning treatment plots during rainfall, particularly in the 34% treatment plot, where the rate of moisture decrease was slower. The photosynthetic rate of major tree species (excluding Pinus densiflora)was highest in Quercus mongolica, with a rate of 7 µmolCO₂·m^-2·s^-1. At a lightintensity of 800 μmol·m^-2·s^-1, Q. mongolica showed the highest photosynthetic level of 6 ± 0.3 μmolCO₂·m^-2·s^-1 in the 45% treatment. The photosynthetic rate of Fraxinus sieboldiana and Styrax japonicus increased as the thinning intensity increased. The Shannon-Wiener index of mycorrhizal mushrooms did not significantly differ among treatments, but the fresh weight of mushrooms was approximately 360-840 g higher in the 34% and 45% treatments than in the control. Additionally, the fresh weight of fungi in the 60% treatment was 860 g less than that in the control. There were more individuals of Amanita citrina in the control than in the thinning treatment, while Suillus bovinus numbers increased by more than 10 times in the 34% thinning treatment compared with the control.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.15 no.3
• /
• pp.130-144
• /
• 2013

In this study, we examined the effect of high temperature of urban area on the physiological response of apple tree including the photosynthesis, shoot growth, and fruit quality of 'Fuji'/M.9 apple trees planted at Daegu urban area (DUA) and Gunwi rural area (GRA) for 2 years (2009-2010). During the apple growing season (April-October), the average air temperature of DUA was about $3.0^{\circ}C$ higher than that of GRA and the total rainfall of DUA was 130 mm more than that of GRA. During fruit enlargement stage (June-August), the number of days that recorded daily mean temperature of over $30^{\circ}C$ were ten on DUA in 2010, but there was no day when such temperature was experienced in 2009. Average air temperature of DUA during the maturation stage (September-October) was $19.8^{\circ}C$, which was $4.0^{\circ}C$ higher than that of GRA. The higher temperature of over $30^{\circ}C$ during fruit enlargement stage decreased the photosynthetic rate, shoot growth, fruit weight, and soluble solid content of 'Fuji'/M.9 apple tree. The moderate temperature of about $20^{\circ}C$ during maturation stage increased the photosynthetic rate and soluble solid content of 'Fuji'/M.9 apple tree, but decreased fruit red color. In regional comparison with GRA, photosynthetic rate of DUA was changed from lower before rainy season to higher after rainy season. Fruit weight was higher in DUA than that of GRA. However, fruit weight between DUA and GRA did not show the difference when accumulated days that recorded daily maximum temperature over $35^{\circ}C$ of DUA was increased. Compared to the GRA, soluble solid content of DUA was higher, but fruit red color of DUA was less. These results indicate that the poor red coloring is the most problematic in 'Fuji'/M.9 apple tree by global warming and urbanization.