• Journal of Korea Water Resources Association
• /
• v.40 no.6 s.179
• /
• pp.431-446
• /
• 2007

Groundwater flow in a basin is greatly affected by many hydrogeological and hydrological characteristics of the basin. A groundwater flow model for the Kap-cheon basin ($area=648.3km^2$) in the Geum river basin was established using MODFLOW by fully considering major features obtained from observed data of 438 wells and 24 streams. Furthermore, spatial groundwater recharge distribution was estimated employing accurately calibrated watershed model developed using SWAT, a physically semi-distributed hydrological model. Model calibration using observed groundwater head data at 86 observation wells yielded the deterministic coefficient of 0.99 and the water budget discrepancy of 0.57%, indicating that the model well represented the regional groundwater flow in the Kap-cheon basin. Model simulation results showed that groundwater flow in the basin was strongly influenced by such factors as topological features, aquifer characteristics and streams. The streams in mountainous areas were found to alternate gaining and losing steams, while the streams in the vicinity of the mid-stream and down-stream, especially near the junction of Kap-cheon and Yudeong-cheon, areas were mostly appeared as gaining streams. Analysis of water budget showed that streams in mountainous areas except for the mid-stream and up-stream of Yudeong-cheon were mostly fed by groundwater recharge while the streams in the mid and down-stream areas were supplied from groundwater inflows from adjacent sub-basins. Hence, it was concluded that the interactions between surface water-groundwater in the Kap-cheon basin would be strongly inter-connected with not only streams but also groundwater flow system itself.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6B
• /
• pp.579-587
• /
• 2010

The mid-range streamflow forecast was performed using NWP(Numerical Weather Prediction) provided by KMA. The NWP consists of RDAPS for 48-hour forecast and GDAPS for 240-hour forecast. To enhance the accuracy of the NWP, QPM to downscale the original NWP and Quantile Mapping to adjust the systematic biases were applied to the original NWP output. The applicability of the suggested streamflow prediction system which was verified in Geum River basin. In the system, the streamflow simulation was computed through the long-term continuous SSARR model with the rainfall prediction input transform to the format required by SSARR. The RQPM of the 2-day rainfall prediction results for the period of Jan. 1~Jun. 20, 2006, showed reasonable predictability that the total RQPM precipitation amounts to 89.7% of the observed precipitation. The streamflow forecast associated with 2-day RQPM followed the observed hydrograph pattern with high accuracy even though there occurred missing forecast and false alarm in some rainfall events. However, predictability decrease in downstream station, e.g. Gyuam was found because of the difficulties in parameter calibration of rainfall-runoff model for controlled streamflow and reliability deduction of rating curve at gauge station with large cross section area. The 10-day precipitation prediction using GQPM shows significantly underestimation for the peak and total amounts, which affects streamflow prediction clearly. The improvement of GDAPS forecast using post-processing seems to have limitation and there needs efforts of stabilization or reform for the original NWP.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.6 no.2
• /
• pp.22-32
• /
• 2003

The purpose of this study is to analyze soil erosion quantity of a basin by using DEM, soil map and landuse map and to find a soil erosion hazard zone in a basin based on this data. In this study, RUSLE was used to analyze soil loss quantity and the research area chosen is Mushim stream which branches off the Geum river. This study used a mean annual precipitation of Cheongju Meteorological Observation was used as a hydrological data and DEM, the detailed soil map(1/25,000), the landuse map collected respectively from Ministry of Environment, National Institute of Agricultural Science and Technology and Ministry of Construction and Transportation. The subject map was drawn to analyze soil erosion hazard zone by using the above data and maps. According to the results of the analysis, a lot of soil loss shows in a bare area. In case of a forest, a slope has a lot of influence on soil loss. The integration and analysis of the above gave the result that $193,730.3m^2$corresponding to 8.5% of the places of which the slope is over 20 degree in a bare area was found to have a higher chance of soil erosion.

• Ecology and Resilient Infrastructure
• /
• v.1 no.1
• /
• pp.39-48
• /
• 2014

In order to establish fundamental data for stream restoration and environmental flow, we investigated optimal ecological flowrate (OEF) and riverine health condition in the Chogang Stream, a tributary to Geum River, Korea. The number of fish individuals sampled in this period were 4,669 in 36 species of 9 families. The most abundant species was Korean chub (Zacco koreanus, 34.0%) followed by pale chub (Z. platypus, 22.6%) and Korean shinner (Coreoleuciscus splendidus, 13.3%). Index of biological integrity (IBI) and qualitative habitat evaluation index (QHEI) values decreased from upstream to downstream along the stream. The estimated IBI value ranged from 27.9 to 38.6 with average 32.2 out of 50, rendering the site ecologically fair to good health conditions. OEF was estimated by the physical habitat simulation system (PHABSIM) using the habitat suitability indexes (HSI) of three fish species Z. koreanus, C. splendidus and Pseudopungtungia nigra selected as indicator species. In Z. koreanus, HSI for flow velocity and water depth were estimated at 0.1 to 0.4 m/s and 0.2 to 0.4 m, respectively. In P. nigra, HSI for flow velocity, water depth and substrate size were estimated at 0.2 to 0.5 m/s and 0.4 to 0.6 m and fine gravel to cobbles, respectively. OEF values increasing from up to downstream was found to increase, weighted usable area (WUA) values increased accordingly.

• Journal of Wetlands Research
• /
• v.22 no.4
• /
• pp.295-301
• /
• 2020

This research analyzed the relationship between environmental factors and the density of Sycios angulatus in the Miho Stream, Geum River water system in order to secure basic data for the control of the ecosystem-distrubing plant Sycios angulatus. As a result of the soil particle size analysis of Sycios angulatus habitat, it was found that the density of Sycios angulatus decreased as the silty and clay contents increased. Most of the Sycios angulatus habitats had high sandy and silt content, and low clay content of less than 2%. The increased flow rate reduced the density of Sicyos angulatus. This is because when the flow rate is increased, the Sicyos angulatus cannot grow due to the change in soil characteristics. Water quality plays a role in supplying nutrients when Sicyos angulatus are submerged. However, due to the change in soil characteristics during flooding, the density of Sicyos angulatus tended to decrease due to impaired growth. The Sicyos angulatus can be managed through artificial and natural techniques. The appropriate natural control technique is the creation of a natural waterway in the habitats to change the water contents.

• Korean Journal of Ecology and Environment
• /
• v.52 no.2
• /
• pp.118-125
• /
• 2019

Swimming performance of fish is an important factor in the survival of fish. Also, swimming performance of fish is used in the form of habitat, or as a condition to consider when creating a fish ladder. However in Korea, researches in swimming performance of Korean freshwater fish were scarce and inadequate in some part, thus fish ladders were installed without considering their swimming performance. Therefore, in this study, we measured swimming performance of 4 Korean freshwater fish species to consider importance of swimming performance test. The fish used in this study were Carassius auratus, Zacco koreanus, Gnathopogon strigatus, Acheilognathus lanceolata intermedia species which was collected during October to November, 2018 at Geum River, and measurement for swimming speed of each fish was done by using $Loligo^{(R)}$ System, swim tunnel respirometer in January to February of 2019. The average value of the burst critical swimming speed ($U_{crit}$) for each species was $0.8{\pm}0.04m\;s^{-1}$ for C. auratus, $0.77{\pm}0.04m\;s^{-1}$ for Z. koreanus, $0.95{\pm}0.04m\;s^{-1}$ for G. strigatus, $0.73{\pm}0.03m\;s^{-1}$ for A. lanceolata intermedia and the average value of prolonged critical swimming speed was $0.54m\;s^{-1}$ for C. auratus, $0.67m\;s^{-1}$ for Z. koreanus, $0.7m\;s^{-1}$ for G. strigatus, $0.54m\;s^{-1}$ for A. lanceolata intermedia. Since the fish used in this experiment were collected from a small part of the water system in Korea and there were only 4 species, they were not enough to represent the species that inhabit the entire Korean water system. It will be necessary to continue evaluating the swimming performance of other freshwater species in Korea.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.9 no.1
• /
• pp.29-36
• /
• 2007

This study was carried out to develop a water quality simulation model for the evaluation of an ungauged watershed. For this purpose, the WASP5 model was selected and modified. The model consists of three sub-models, LOAD-M, DYN-M, and EUT-M. LOAD-M, an empirical model, estimates runoff loadings using point and non-point source data of villages. The Geum River Estuary watershed was selected to calibrate and verify the Modified-WASP5. The LOAD-M model was established using field data of water quality and quantity at the gauging stations of the watershed and was applied to the ungauged watersheds, taking the watershed properties into consideration. The result of water quality simulation using Modified-WASP5 shows that the observed average BOD data from Gongju and Ganggyeong were 2.6 mg/L and 2.8 mg/L, and the simulated data were 2.5 mg/L and 2.4 mg/L, respectively. Generally, simulation results were in good agreement with the observed data. This study focused on formulating an integrated model for evaluating ungauged watersheds. Even though simulation results varied slightly due to limited availability of data, the model developed in this study would be a useful tool for the assessment and management of ungauged watersheds.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.3
• /
• pp.93-105
• /
• 1993

In this paper, the maximum scour depths at piers located in the Bo Cheong Stream, which is a tributary in the Geum River System, were calculated and compared using 24 local pier scour equations. The equations were classified as six groups by non-dimensional types of equations. The geometric data in the stream bed and pier data at San Seong, Yi Pyung and San Gye, which are IHP data collection stations, were utilized for applying the scour equations. The geometric data in the stream bed were obtained by analyzing the bed material sampled in three stations which are in the left side, middle and right side for stream direction. The maximum flow velocities at maximum flow depths which were measured from 1982 to 1991, were used as the hydraulic flow data. The pier data for predicting pier scour depths were measured in the fields. The maximum pier scour depths calculated using the equations were compared with the held scour depths measured in the streams or rivers in the world. Arunachalam, Shen-Karaki III, Jain-Fischer equations are selected as the proper local scour equations for predicting the maximum local scour depths at piers in the Bo Cheong Stream. Inglis-Lacey and Shen-Karaki II equations are applicable in case of rapid flows conditions in which Froude number is over 0.3. Froehlich, Laursen I, Laursen II, Neill, Melville equations are applicable in the slow flow conditions in which Froude number is less than 0.3. Blench equation or Inglis-Poona equation varies rapidly by changing Froude numbers. Therefore the equations should not be used without careful considerations in selecting the applicable ranges. The maximum local scour depths calculated using Sarma-Krishnamurthy, Ahmad, Coleman, Varzeliotis, Larras, Bata, Chitale, Venkatadri, Basik-Basamily-Ergun, U.S.G.S., Shen I equations are usually less than the scour depths measured in the fields.

• Korean Journal of Environmental Biology
• /
• v.41 no.2
• /
• pp.109-125
• /
• 2023

This study was conducted to select target fish species as baseline research for accumulation analysis of major hazardous chemicals entering the aquatic ecosystem in Korea and to analyze the impact on fish community. The test bed was selected from a sewage treatment plant, which could directly confirm the impact of the inflow of harmful chemicals, and the Geum River estuary where harmful chemicals introduced into the water system were concentrated. A multivariable metric model was developed to select target candidate fish species for hazardous chemical analysis. Details consisted of seven metrics: (1) commercially useful metric, (2) top-carnivorous species metric, (3) pollution fish indicator metric, (4) tolerance fish metric, (5) common abundant metric, (6) sampling availability (collectability) metric, and (7) widely distributed fish metric. Based on seven metric models for candidate fish species, eight species were selected as target candidates. The co-occurring dominant fish with target candidates was tolerant (50%), indicating that the highest abundance of tolerant species could be used as a water pollution indicator. A multi-metric fish-based model analysis for aquatic ecosystem health evaluation showed that the ecosystem health was diagnosed as "bad conditions". Physicochemical water quality variables also influenced fish feeding and tolerance guild in the testbed. Eight water quality parameters appeared high at the T1 site, indicating a large impact of discharging water from the sewage treatment plant. T2 site showed massive algal bloom, with chlorophyll concentration about 15 times higher compared to the reference site.