• Korean Journal of Fisheries and Aquatic Sciences
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• v.1 no.1
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• pp.31-43
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• 1968

1. Shell height frequencies of the fresh-water cockle, Corbicula elatior, sampled in the period of 1960 to 1963, are analyzed to assess the age composition and average growth pattern. Cumulative frequencies in a sample are traced on a probability scale, and the points of inflection on a probability graph are assumed to dissect age groups. 2. Seasonal growth of Corbicula elatior in the Naktong River ill as follows: Young cockles settle down on river-bed by June and grow rapidly during the summer season, reaching 14mm in shell height by October. From October to April the growth is very slow. The rapid growth in the second year starts around in May. 3. Survival rate per year for Corbicula elatior in the Naktong River is estimated to be $5\~10\%$ by age composition.

• Journal of Korea Water Resources Association
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• v.42 no.7
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• pp.579-589
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• 2009

Hwang River in South Korea, has experienced channel adjustments due to dam construction. Hapcheon main dam and re-regulation dam. The reach below the re-regulation dam (45 km long) changed in flow regime, channel width, bed material distribution, vegetation expansion, and island formation after dam construction. The re-regulation dam dramatically reduced annual peak flow from 654.7 $m^3$/s to 126.3 $m^3$/s and trapped the annual 591 thousand $m^3$ of sediment load formerly delivered from the upper watershed since the completion of the dam in 1989. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that non-vegetated active channel width narrowed an average of 152 m (47% of 1982) and non-vegetated active channel area decreased an average of 6.6 km2 (44% of 1982) between 1982 and 2004, with most narrowing and decreasing occurring after dam construction. The effects of daily pulses of water from peak hydropower generation and sudden sluice gate operations are investigated downstream of Hapcheon Dam in South Korea. The study reach is 45 km long from the Hapcheon re-regulation Dam to the confluence with the Nakdong River. An analysis of a time series of aerial photographs taken in 1982, 1993, and 2004 showed that the non-vegetated active channel width narrowed an average of 152 m (47% reduction since 1982). The non-vegetated active channel area also decreased an average of 6.6 $km^2$ (44% reduction since 1982) between 1982 and 2004, with most changes occurring after dam construction. The average median bed material size increased from 1.07 mm in 1983 to 5.72 mm in 2003, and the bed slope of the reach decreased from 0.000943 in 1983 to 0.000847 in 2003. The riverbed vertical degradation is approximately 2.6 m for a distance of 20 km below the re-regulation dam. It is expected from the result of the unsteady sediment transport numerical model (GSTAR-1D) steady simulations that the thalweg elevation will reach a stable condition around 2020. The model also confirms the theoretical prediction that sediment transport rates from daily pulses and flood peaks are 21 % and 15 % higher than their respective averages.

• Water for future
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• v.9 no.1
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• pp.86-100
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• 1976

To study influences on the downstream, and the Gunsan harbor by setting up estuary of the Gumgang, available data which were collected from the measuring stations which were established within the river basin of which results attained are as follows: 1. The discharge can be calculated as the relationship between the discharge and precipitation in the basin is $R=4{\times}10^{-4}p^2$ or R=P-600 2. The discharge flow in to small resevoirs in the basin can be estimated as $QR=QS\frac{PR-600}{PS-600}(\frac{AR}{AS})$ 3. This daily average discharge at Kongju is 31% less than the during maximum probable discharge and that in Okcheon is 48% less than the daily maximum probable flood. 4. The maximum probable flood from the small stream in the basin can be estimated by a $Q=82.45A^{0{\cdot}464}$ 5. Sediments can be computed with Qs (suspended load)=1.41 $Q^{1{\cdot}42}$ and Qb (bed load)=165.2 $Q^{0{\cdot}705}$. 6. By setting up the specific estuary the tidal movement will be reduced to 93.6% on the average and the sedimentation is reduced to 96.0%. Upon review of overall analysis, the dead wate level of estuary of Gumgang will completely sedimented in next 30 years, therefore, the dredging work at Gunsan harbor is reduced to 73.6%, it is considered that life length will be extended about 52years taking account the existing condition.

• Journal of Korea Water Resources Association
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• v.49 no.10
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• pp.809-821
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• 2016

The study area is local river of 671 (total length 3,741 km) in Gyeongnam prefecture, the results are as follows. Total number of river-crossing structures was investigated as 7,730, and it was found that structures were installed in 2.1 sites per 1 km (river length) on average. Diversion weirs for agriculture were 4006 (51.82%) and drop structures for channel bed maintenance were 3670 (47.48%), but the rest (riverbed road etc.) were 54 (0.70%). The number of high structures (height > 1.0 m) that affect many impact in upstream and downstream was investigated as 3,897 (51%), and the number of low structures (height < 0.5 m) that affect negligibly was 1109 (14%). Fish ladders have been installed on 640 (8%) structures in 153 (23%) rivers. In flood control and environment conservation, river-crossing structures brought about various impact that flood water level is raises and the eco-corridor is intercept. In order to improve these problems, we proposed a few engineering measures that can be realize with respect to river-crossing structures.

• Korean Journal of Environment and Ecology
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• v.26 no.3
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• pp.367-373
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• 2012

Population ecology (Ecological characteristics) of Squalidus japonicus coreanus from the Namhan River(Yangpyeong-gun Yangpyeong-eup Changde-ri), Gyeonggi-do, Korea were investigated from January to December 2011. Short barbel gudgeon inhabits habitats run of the lower river. The stream bed was mostly covered sand. Their current velocities were 0.14~1.38m/sec and depths were 80~120cm. The sex ratio of female to male was 1 : 0.82. It is presumed that the spawning season is from June to July and water temperatures were $18.5{\sim}24.3^{\circ}C$. Sexually matured individuals appeared over the two year of age. Frequency analysis of total length indicated that the group with 34~50mm in total length was one year old, the 51~74mm was two years old, and the group over 75mm was three years old. The average number of eggs in the ovaries was estimated as 1,871 per matured female. Stomach content of S. japonicus coreanus were Cyanophyta, Chlorophyta, Bacillariophyta, Rotatoria, Crustaceae, Copepoda, Ephemeroptera, Diptera, and Nematoda. omnivorous, mainly feeds on benthic invertebrates such as chironomidae larvae.

• Korean Journal of Ichthyology
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• v.13 no.2
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• pp.123-128
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• 2001

The reproductive ecology of Gobiobotia brevibarba was investigated at Hongchen River of Bangokri, Seomyon, Hongcheongun, Kangwondo, from March 1999 to February 2000. The favorite habitat was a stretch of river with fast flow and a stream bed mostly covered with cobbles and pebbles. The spawning ground was a riffle area 20~50 cm deep, with a current velocity of 0.6~1.3 m/sec, and a bottom consisting of cobble and boulder. The sex ratio of female to male was 1 : 0.86. Peak spawning season was May when water temperatures rose to $18{\sim}20^{\circ}C$. Male and females became sexually mature when they attained more than 40 mm and 50 mm in body length, respectively. The average number of eggs in the ovary was $2,040{\pm}400.57$ and the egg diameter was $1.98{\pm}0.06\;mm$. The matured eggs were demersal, spherical, and dimmed light yellow in color.

• 한국해양학회지
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• v.7 no.1
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• pp.1-14
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• 1972

Seasonal changes in nutrients and suspended organic particulates were measured in the estuary of Nak-dong River in relation to the black laver bed. Monthly measurements of water temperature, pH, dissolved oxygen, nutrients ( $NH_4$-N, $NO_2$-N, $NO_3$\-N, $PO_4$-P and $SiO_2$-Si) and organic suspended particulates (organic carbon and nitrogen) were determined at five stations from February through December, 1970. PH varied 7.6-8.4 with an average of 8.0, and percent saturation of dissolved oxygen were 71-147% with an average of 100.8%. Studies gave evidence that Nak-dong River estuary is strongly enriched with nutrients. Concentrations of nutrients were: 0.13-12.54 ${\mu}g$-atoms/${\iota}$ (averaging 1.63 ${\mu}g$-atoms/${\iota}$) for $NH_4-N$, 0.12-2.09 ${\mu}g$-atoms/${\iota}$ (averaging 0.71 ${\mu}g$-atoms/${\iota}$) for $NO_2-N$, 3.46-56.79 ${\mu}g$-atoms/${\iota}$ (averaging 21.54 ${\mu}g$-atoms/${\iota}$) for $NO_3$-N, 4.04-57.90 ${\mu}g$-atoms/${\iota}$ (averaging 23.79 ${\mu}g$-atoms/${\iota}$) for total soluble nitrogen, 0.18-5.05 ${\mu}g$-atoms/${\iota}$ (averaging 0.96 ${\mu}g$-atoms/${\iota}$) for $PO_4$-P, and 18.33-133.29 ${\mu}g$-atoms/${\iota}$ (averaging 71.57 ${\mu}g$-atoms/${\iota}$) for $SiO_2$-Si, respectively. These nutrient levels were considerably higher compare with other productive laver beds of Wan do and Pyung-il Do in Korea or Ise Bay in Japan. Concentrations of suspended organic particulates varied 55-648 ${\mu}g/{\iota}$ (averaging 392 ${\mu}g/{\iota}$) with organic carbon, 30-155 ${\mu}g/{\iota}$ (averaging 92 ${\mu}g/{\iota}$) with organic nitrogen, and its carbon-nitrogen ratios were varied within 1.5-8.4 with an average of 4.6.

• Journal of environmental and Sanitary engineering
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• v.5 no.1
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• pp.1.1-14
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• 1990

This study was conducted to investigate the contents of heavy metals in soils of the Kumho river basin, by analyzing soils according to the distance from edge of the river and to the soil layers. The contents of heavy metals in soils showed highly in its downstream. Namely there was shown a remarkably high contents of these heavy metals in the Kum-ho bridge areas where Kongdan stream joins Dalseo stream, such as 39.52ppm for zinc, 35.92ppm for copper, 97.90ppm for iron, 102.45ppm for manganese, 13.92ppm for lead, respectively, and 0.48ppm for cadmium. However, the heavy metals contents in soils around Kangchang bridge tended to gradually decrease in its contents, probably because its main soils consisting of sand. Based on their soil layers, the average contents of these heavy metals in the surface soils were higher than one of the subsurface soil. Its contents according to the distance from the river edge indicated some difference every individual area. Nevertheless, its contents showed lower contents in the area far away from the edge. And its contents tended to again increase in the outside bank. In addition, a remarkable positive correlation is shorten between individual heavy metals, except correlation between iron and lead. Also cadmium just shows reverses correlation in the statistics. With respect to comparison between soil layers, there was a remarkable positive correlation between surface layers and subsurface layers. Considering the above results, it seems that the pollution of river bed's soil is in proportion to it of stream.

• Journal of The Geomorphological Association of Korea
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• v.19 no.1
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• pp.41-56
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• 2012

The purpose of this study is to look into the location environment of prehistoric and ancient remains (hereinafter referred as remains) in Daejeon Area. For the purpose of this, out of remains reported in investigation areas so far with the object of remains (total 22 places) of New Stone Age -Proto Three Kingdom period, geographical and Geomorphological analysis was conducted. The results are like the following. Most of the remains are distributed over hills especially flat surface - semi-gentle slope of hills. The bed rocks of the remains (21 places, about 95%) are composed of double-mica granite. The remains (19 places, 86%) retain 'the 1st-2nd small scale river and '5th or higher medium scale river'within comparatively short distance at the same time. The average altitude of remains is 71m and most remains are located over the altitude of 50 - 90m. The average gradient of hillslop where the remains are located is $6.7^{\circ}$ and the remains (15 places, 71%) are located over the gradient of about $0-15^{\circ}$. And the tendency that the higher the gradient of remains the smaller the number of remains was confirmed. From the above, it is judged that the inhabitants who lived in Daejeon Area at that time preferred hills with comparatively not high altitude and the earth's surface of low gradient and in addition they recognized water (river) as being important when they selected the location of settlement (or dwelling sites group).

• Korean Journal of Environment and Ecology
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• v.36 no.4
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• pp.381-389
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• 2022

This study investigated the ecological characteristics of Microphysogobio yaluensis at Dugye Stream of Geum River basin from January to December 2021. The river bed structure of this species' habitat was rich in pebbles and gravel. The water depth ranged from 12 to 85 cm with an average of 23 cm, which was shallow. The stream velocity was rapid at 1.03±0.34(0.72-1.47) m/sec. The ratio of females to males was 1:0.86. The age according to the total length-frequency distribution as of summer (June, July) indicated that the group with less than 50 mm (30.4-49 mm) in total length was one year old, the group with 50-69 mm was two years old, and the group over 70-92 mm was three years old. Both male and female fish sexually matured at 50 mm long and two years old in June and July. The spawning season was from July to August, and the water temperature was between 25.8℃ and 28.2℃ during the period. The prosperous spawning season was July. The matured eggs were yellowish and spherical with a mean diameter of 0.52±0.16 (0.33-0.77) mm, and the average number of eggs found in the ovaries of mature female fish was 2,593 (1,343-4,672). As for the food of M. yaluensis, only attached algae, which grow by attaching to stones and gravel of the stream rapids, were identified. The feeding habit of M. yaluensis was reported to be herbivorous, ingesting Cyanophyta, Chlorophyta and Bacillariophya. Also, the species belonging to Bacillariophya and Chlorophyta were abundant in Dugye Stream.