• Korean Journal of Environmental Agriculture
• /
• v.16 no.1
• /
• pp.19-24
• /
• 1997

This studies was carried out to investigate the soil contamination and water quality affected by agricultural activities in the Keum river Districts. Soil pH of the Keum river districts were $5.56{\sim}7.09$ in Keum river headwater and Namdae-cheon but that of Keumgang-lake were $5.07{\sim}7.21$ because of the cattle shed and industrial complex around. Total nitrogen contents of soils were found difference as period of fertilizer application. Total phosphorous content of soils no difference were found between the headwater and Keumgang-lake. Heavy metal contents of soils were natural background level. Water pH of the Keum river districts ranged from 6.59 to 7.80 and COD was maintain below 1.0 mg/L. Total nitrogen content affected by a livestock wastes and sewage water were the higher than that of others and total phosphorous content showed below 0.5 mg/L. Nitrate nitrogen and ortho-phosphate contents were very high according to the influence a livestock waste and sewage water in headwater region of the Keum river partly. Chlorine and sulfate contents were high according to the influence of sea water invasion. Heavy metal contents of waters were natural background level.

• Economic and Environmental Geology
• /
• v.37 no.2
• /
• pp.195-206
• /
• 2004

Paleomagnetic and rock-magnetic investigations have been carried out for the Cretaceous sedimentary rocks in the Poongam (also called Gapcheon) Basin in the eastern South Korea. A total of 128 independently oriented core samples were drilled from 13 sites for this study. The mean direction after bedding correction (D/I=353.1$^{\circ}$/55.6$^{\circ}$, k=21.5, =$$\alpha$_{95}$=10.1$^{\circ}$) is more dispersed than the mean direction before bedding correction (D/I=10.5$^{\circ}$/56.9$^{\circ}$, k=73.9, =$$\alpha$_{95}$=5.3$^{\circ}$), and the stepwise unfolding of the characteristic remanent magnetization (ChRM) reveals a maximum value of k at 20% unfolding. Secondary authigenic hematite accompanied by altered clays such as chlorite was identified by the electron microscope observations. These results collectively imply that the ChRM is remagnetized due to the formation of the secondary authigenic hematite after tilting of the strata. It is interpreted that the chemical remagnetization was connected to the introduction of mixed magmatic-meteoric fluids, which formed hydrothermal vein deposits near the study area. The paleomagnetic pole position (214.3$^{\circ}$E, 81.6$^{\circ}$N, =$A_{95}$=7.4$^{\circ}$) of the Cretaceous sedimentary rocks calculated from remagnetized directions is close to those of the Late Cretaceous and Tertiary poles of the Korean Peninsula. This Late Cretaceous to Tertiary remagnetization seems to be widespread over the Okcheon Belt because the chemical remagnetization is previously reported to be found in rocks from other Cretaceous small basins (e.g., Eumseong, Gongju and Youngdong basins) along the Okcheon Belt and some Paleozoic strata from the Okcheon unmetamorphosed zone.

• 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.

• Korean Journal of Agricultural Science
• /
• v.2 no.1
• /
• pp.281-300
• /
• 1975

The precipitation data and water level data in twenty-four sampling places, to investigate same hydrological quantities along the basin of Geum River, have been analyzed, and the findings for the first report are summarized as follows. 1. The mean annual precipitation in the basin of Geum River is of 1203mm, and the areal weight of areal rainfall by Thiessen's method shows as Table 1. 2. The areas where have maximum annual precipitation of 1501 to 2000mm, are seventeen placed among twentyfour gauging stations, and it is founded to be the highest rate with 71 percents. The precipitation of below 1500mm is measured in the other three statinons, and that of above 2001mm in four stations, too. 3. The areas where have maximum rainfall of 201 to 300mm within a day, are fifteen places, and that comes in the highest rate of distribution with 63 percents. 4. As to distribution of the places with maximum rainfall of below and above 300mm within two days, it shows respectively 50 percents. 5. The areas where have maximum rainfall of 301 to 400mm within three days, are fifteen places, and it is the highest rate of distribution with 63 percents. 6. The fourteen places have maximum rainfall of 401 to 600mm within a continuous day, it is the highest rate of distribution with 58 percents. 7. Table 5 shows probable maximum rainfall within a day, and it does the most rainfall a long the upper stream of Daecheong dam site around Muju, and the next shows in the areas around Ganggyeung, Gongju and Buyeu. 8. During irrigation period on paddy corp, for 100 days from early ten days in June to early ten days in September the areas where have rainfall of 601 to 800mm are sixteen places, and it is the highest rate of distribution with 76 percents, as Table 6 9. The areas where have effective rainfall of 501 to 600mm, are fifteen places, and it is the highest rate of distribution with 71 percents. Thirteen places have the effective ratio of 66 to 75 percents, and it means 62 percents of distribution, and the next, 76 to 85 percents in the seven places, and it comes 33 percents. 10. The areas where have probable effective rainfall of 401 to 500mm, are fourteen places, which is about 100mm less than mean effective rainfall in each area, and that comes 67 percents of distribution. 11. A particular year can not be appointed as once -in-10 year drought in the same year as a whole in the basin of Geum River. 12. The basin of Geum River, s/S being 0.53 to 0.74, has relatively proper conditions in the aspect of water resources.

• Journal of Environmental Impact Assessment
• /
• v.27 no.6
• /
• pp.685-694
• /
• 2018

We measured ecological niche space (ENS) using carbon and nitrogen stable isotope ratios of benthic macroinvertebrates to estimate its applicability for large river assessment. In particular, we compared ENSs of selected macroinvertebrates between upper and lower area of Seungchon Weir in Yeongsan River to estimate the impact of weir on biological community. We also measured basic water quality and community indices including benthic macroinvertebrates index (BMI) to estimate their correlations with calculated ENS. ENS was calculated using the Bayesian Stable Isotope in R statistics (package "SIBER"). The results showed that seasonal variations in water quality and community indices were found, but there was no apparent tendency between upper and lower area of the Seungchon Weir in June (before rainy season) and August (after rainy season). However, ENS of benthic macroinvertebrates markedly decreased across the weir in both June and August regardless of changes in water quality. This means the physical change of the stream due to the weir cause decrease of ecological isotopic niche space of benthic macroinvertebrates regardless of water quality, suggesting physical modification by the weir can affect the interaction between habitat condition and macroinvertebrates. Therefore, the ecological isotopic niche space can be a useful supplementary indicator for the river ecosystem assessment.

• Korean Journal of Ecology and Environment
• /
• v.52 no.1
• /
• pp.50-64
• /
• 2019

Recently, quantitative analyses of food web structure based on carbon and nitrogen stable isotopes are widely applied to environmental assessments as well as ecological researches of various ecosystems, particularly rivers and streams. In the present study, we analyzed carbon and nitrogen stable isotope ratios of POM (both planktonic and attached forms), zooplankton, benthic macroinvertebrates and fish collected from 6 sites located at Nakdong River. Samples were collected from upstream areas of 5 weirs (Sangju, Gangjeong-Goryeong, Dalseong, Hapcheon-Changnyeong, and Changnyeong-Haman Weirs) and one downstream area of Hapcheon-Changnyeong Weir in dry season (June) and after rainy season (September). We suggested ranges of their carbon and nitrogen stable isotope ratios and calculated their trophic levels in the food web to compare their temporal and spatial variations. Trophic levels of organisms were relatively higher in Sangju Weir located at upper part of Nakdong River, and decreased thereafter. However, the trophic levels were recovered at the Changnyeong-Haman Weir, the lowest weir in the river. The trophic level calculated by nitrogen stable isotope ratios showed more reliable ranges when they were calculated based on zooplankton than POM used as baseline. The suggested quantitative ecological information of the majority of biological communities in Nakdong River would be helpful to understand the response of river food web to environmental disturbances and can be applied to various further researches regarding the quantitative approaches for the understanding food web structure and function of river ecosystems as well as restoration.

• Korean Journal of Ecology and Environment
• /
• v.55 no.1
• /
• pp.35-48
• /
• 2022

Fish assemblage of total 325 of Korean peninsula estuaries were surveyed to analyze the characteristics of community structure and diversity by sea areas for three years from 2016 to 2018. The scale (stream width) of Korean estuaries were various (14~3,356 m), and 68.9% of all estuaries showed salinity of less than 2 psu. Total 149 species classified into 52 families of fish were identified, and the dominant and sub-dominant species were Tribolodon hakonensis (relative abundance, RA, 12.5%) and Mugil cephalus (RA, 9.5%), respectively. The estuary of the Korean Peninsula had different physical and chemical habitat environments depending on the sea area, and accordingly, fish community structure also showed statistically significant differences (PERMANOVA, Pseudo-F=26.69, P=0.001). In addition, the NMDS (nonmetric multidimensional scaling) results showed the patterns that indicating fish community difference by sea areas, even though low community similarity within sea area (SIMPER, 21.79~26.39%). The estuaries of east sea areas were distinguished from the others in the aspects of which, the higher importance of migratory fishes and endangered species, and that of brackish species were characterized at south sea estuaries. However, the estuaries of west sea showed higher importance of species that have a relation with freshwater (primary freshwater species, exotic species), which is the result that associating with the lower salinity of west sea estuaries because of the high ratio of closed estuaries(78.2%). The SIMPER analysis, scoring the contribution rates of species to community similarity, also showed results corresponding to the tendency of different fish community structures according to each sea area. So far, In Korea, most studies on fish communities in estuaries have been conducted in a single estuary unit, which made it difficult to understand the characteristics of estuaries at the national level, which are prerequisite for policy establishment. In present study, we are providing fish community structure characteristics of Korean estuaries in a national scale, including diversity index, habitat salinity ranges of major species, distribution of migratory species. We are expecting that our results could be utilized as baseline information for establishing management policies or further study of Korean estuaries.

• Korean Journal of Ecology and Environment
• /
• v.55 no.1
• /
• pp.1-9
• /
• 2022

An estuary is an area where a freshwater river or stream meets the ocean. Even before the importance of the value of estuaries was recognized, the estuary was lost because of large-scale conversion by draining, filling, damming, and dredging. In South Korea, 643 estuaries are located, and the total area is 3,248,300 ha, accounting for 32.5% of the total area of South Korea. Over 35% of Korean estuaries are closed estuaries which are only temporally connected with the sea, either permanently or periodically. Since 2008, in order to preserve the estuary ecosystem and solve major issues in the estuary by accumulating knowledge about the estuarine ecosystem, the Ministry of Environment of Republic of Korea has been conducting the "Estuarine Ecosystem Monitoring and Assessment Project". At 668 sites of 325 estuaries, epilithic diatom, benthic macroinvertebrate, fish, and vegetation are investigated, and the habitat condition of each site is evaluated using the newly developed biotic index. More than 100 researchers annually record 2,097 species of estuaries according to the standardized survey guidelines over the past 14 years and provide strictly managed data necessary for establishing estuaries conservation policies. As a result of bibliometric analysis of 1,195 research articles related to the monitoring and assessment of the estuarine ecosystem, research on pollutants such as heavy metals and sediment control have recently been conducted. "Estuarine Ecosystem Monitoring and Assessment Project" is an ecological monitoring type of long-term mandated monitoring that is usually focused on identifying trends. Although it is difficult to identify the mechanism influencing a change in an ecosystem through long-term mandated monitoring, providing empirical data for supporting evidence-based policy, decision-making, and the management of ecosystems. In order to increase the efficiency of the project, research to investigate the relationship between sediments and pollutants and organisms can be conducted at specific estuaries or sites to compensate for the shortcomings of mandatory monitoring.