• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.35-49
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• 2009

This study proposes a method to evaluate agricultural reservoirs drought by modifying SWSI (Surface Water Supply Index). The method was applied to Geum river basin and the results were represented as spatially distributed information. The SWSI evaluates hydrological drought of watershed unit by selectively applying one or all of the components of snowpack, precipitation, streamflow and reservoir storage. South Korea has 22 % of agricultural area, and rice paddy covers 64 % among them. Usually paddy fields scattered along stream are irrigated by so many small agricultural reservoirs. It is difficult to evaluate agriculture drought by the little information and large number of agricultural reservoirs. In this study, seven agricultural reservoirs over 10 million ton storage capacity were selected in Geum river basin, and the SWSI was evaluated for both upstream and downstream of the reservoirs using 16 years data (1991-2006). Using the results, multiple regression analyses with precipitation and reservoir storage as variables were conducted and the equations were applied to other watersheds. The spatial results by applying regression equations showed that the severe and moderate drought conditions of July and September in 1994, June in 1995, and May in 2001 were well expressed by the watershed unit.

• Water for future
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• v.27 no.3
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• pp.83-83
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• 1994

The major objective of this study is to analyze the water balance of the Keumgang Estuary Reservoir in the Keum River basin. This basin is one of the catchment area which water utilization is very complicated. For the study of this area, this paper is to evaluate the monthly river-inflow of the Keumgang Estuary Resorvoir. Here, two approach methods are proposed which can take care of the natural and the low flow. The results are as follows. The natural flow at the Keumgang Estuary Reservoir during the wet season was decreased to 8.4% and increased from 0.4% to 17.6% during the dry season by the effects of Deachung Reservoir at the upper basin. The monthly fluctuation of the low flow during My-June varies to a great extent, when large amounts of irrigation water are required.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.1-8
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• 1997

Abstract The need for integrated reservoir system operation become more intense as the demands from the system increase. A deterministic, three-dimensional discrete incremental dynamic programming approach is presented to derive reservoirs system operational planning strategies. The developed H3DP model optimizes the monthly operation of the Hwachon and Soyang Projects on the North Han river and Chungju Main Project on the South Han river. By using the H3DP model, Hwachon project was reevaluated as a component of the upstream multipurpose storage reservoirs in the basin based on 1993 hydrology. This case study demonstrates the practical use of the developed model for the basin multi-reservoir system operation in an integrated, multipurpose fashion.

• Environmental Engineering Research
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• v.20 no.3
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• pp.290-297
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• 2015

This paper presents the evaluation of the impact of climate change on water resources and yield capacity of Asa and Kampe reservoirs. Trend analysis of mean temperature, runoff, rainfall and evapotranspiration was carried out using Mann Kendall and Sen's slope, while runoff was modeled as a function of temperature, rainfall and evapotranspiration using Artificial Neural Networks (ANN). Rainfall and runoff exhibited positive trends at the two dam sites and their upstream while forecasted ten-year runoff displayed increasing positive trend which indicates high reservoir inflow. The reservoir yield capacity estimated with the ANN forecasted runoff was higher by about 38% and 17% compared to that obtained with historical runoff at Asa and Kampe respectively. This is an indication that there is tendency for water resources of the reservoir to increase and thus more water will be available for water supply and irrigation to ensure food security.

• Journal of Plant Biology
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• v.11 no.2
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• pp.1-30
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• 1968

The Han River was investigated monthly from April through September, 1967 at Chun-chon reservoir, Shin-yean, So-yang, Chung-pyong reservoir, Yang-soo-ri and Gi-doo-won to clarify the phytoplankton and to study its seasonal variation. At the same time, vertical distribution of phytoplankton was also studied from June through September at Chun-chon and Chung-pyong reservoir. The results obtained are as follows: As the environmental conditions, water temperature, dissolved oxygen, pH, and transparency were determined. The plankton samples collected from six stations were identified and classified by Engler's classification system. It resulted in 4 phyla, 4 classes, 3 subclasses, 13 orders, 27 families, 5 tribes, 71 genera, 222 species, 1 subspecies, 51 varieties and 2 forms. The total number of phytoplankton identified was 276. Of them, 84 species, 1 subspecies 26 varieties, 2 forms were recorded in this paper for the first time. Considering with the habitat of the total number of phytoplanktons, the highest percentage of Limnoplankton existed in the Chung-pyong reservoir. It suggests that hte Chung-pyong reservoir is becoming to have the character of lake. The planktons appeared commonly during six months at six station belong to Chrysophyta including 22 species in 11 genera. Among these 22 species, Navicula, consists of 6 species, was the most abundant. The number of species identified uniquely at each station were 5 species in the Chun-chon reservoir, 6 in Chung-pyong and Yang-soo-ri, 8 at Shin-yean, 11 at So-yang, and 18 at Gi-doo-won. The number of species occurred at all stations were 29 in spring, 42 in Autumn and during investigation period. The maximum production of total phytoplankton was generally shown in the late spring and the early fall with differences in quantity at six collecting statins. In the Chun-chon reservoir, the high concentration of approximately 1, 190, 000 cells per litter in the months of August and September was due to the increase of Chrysophyte genus, Melosira and the highest concentration of approximately 2, 000, 000 in July at Gi-doo-won was caused Chlorophyte genus, Secenedesmus. The Chun-chon reservoir of three years old was different from the Chung-pyong reservoir of 25 years old with respect to increase in Melosira genus in August and September. After the completion of the Ui-am reservoir, though there was an increase in total density, the number of species of phytoplankton was not changed. It suggests that Ui-am reservoir is similar to the Chun-chon reservoir under the influence of the latter. The density of total phytoplankton was generally high at the depth of 2m to 5m for the two reservoirs.

• Journal of Korean Society on Water Environment
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• v.26 no.2
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• pp.356-364
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• 2010

The chemical and biological reaction of the aquatic organism is closely related with temperature variation and water temperature is one of the most important factors that should be considered in establishing sustainable reservoir operation scheme to minimize adverse environmental impacts related with dam construction. This paper investigates temperature variation in the downstream of Yongdam Reservoir using sampled data collected from total 8 temperature monitoring stations placed along the main river and the major tributaries. Using KoRiv1, 1-dimensional dynamic water quality simulation model, temperature variation in the downstream of Yongdam Reservoir has been simulated. The simulated results were compared with sampled data collected from May 15 to August 1 2008 by applying two different temperature modeling schemes, equilibrium temperature and full heat budget method. From the result of statistical analysis, seasonal temperature variation has been simulated by applying the equilibrium temperature scheme for comparison of the difference between the reservoir operation and the natural conditions.

• Journal of The Geomorphological Association of Korea
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• v.26 no.4
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• pp.1-20
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• 2019

In order to establish appropriate policy to control sediment-associated problems, it is necessary to identify the physical characteristics of the reservoir sediments in particulate form in the Yeongsan River. Two time-integrated suspended sediment samplers were installed at Seungchon and Juksan weir on the upper and middle Yeongsan River in July 2012. Reservoir sediment samples were obtained at monthly intervals until October 2014. During the monitoring period, a total of 38 sediment samples were obtained and analyzed. Seasonal trends of suspended sedimentation rates and grain size distributions were examined based on variations in precipitation and discharge fluctuations. Moreover, stream flow characteristics, which has a great influence on the physical characteristics of the river sediment, was analyzed using flow duration curve for the period 2003-2019 at Naju gauging station. Sedimentation rates during summer, when heavy rainfall was concentrated due to the monsoonal front and typhoon, were very high, indicating the positive relationship between sediment concentration and discharge. Particle size analysis of the collected sediment showed that coarse silt and very fine sand-sized sediment dominated most of the Seungchon weir sediment. On the other hand, medium silt-sized sediment dominated the downstream Juksan weir except for a few summer samples. These results implied that the physical characteristics of the suspended sediment are determined not only due to flow fluctuations, but also with regard to the antecedent rainfall conditions, hillslope-channel connectivity, and the supply of materials from various contributing regions. This information about flow characteristics and temporal variations in reservoir sediment can be used for safe management of the weir and discussing the issues on the dismantling of the weirs.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.89-96
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• 2011

This study was carried out to assess the variations of water quality caused by the dam construction on the river. Six dams-Yongdam, Miryang, Hoengseong, Boryeong, Jangheung and Buan- constructed recently in Korea were selected for the study. Chemical oxygen demand(COD) was increased in the initial stage of water storage at dams compared to the lotic(river) environment, but after 3 years it was maintained lower and stabilized concentrations. Five dams except for Jangheung Dam were maintained Ia~Ib grade conditions under the water quality criteria of Korea. The concentrations of total nitrogen(T-N) were decreased under the lentic(reservoir) environment compared to the river status. Total phosphorus(T-P) was decreased 13~63% at the reservoir condition. We concluded that increase of COD concentration was due to the debris organic materials of the land, but temporary phenomenon. T-N and T-P concentrations were decreased at the lentic condition compared to the lotic.

• Advances in environmental research
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• v.7 no.3
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• pp.161-175
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• 2018

Krishna River is significantly affected due to Srisailam dam from past 30 years. The impact of this hydraulic structure drastically reduced the minimum flow regime on the downstream, which made the river nearing to decaying stage. In the present paper, Environmental Flow called minimum flow values released for the dam are estimated with the help of three hydrological methods viz., Range of variability Approach (RVA), Desktop Reserve Model (DRM), and Global Environmental Flow Calculator (GEFC). DRM method suggested considering the intermediate values obtained from among the three methods to preserve the ecosystem on the downstream of the river, which amounts to an average annual allocation of 9378 Million Cubic Meter (MCM) which is equal to 23.11% of mean annual flow (MAF). In this regard GEFC and RVA methods accounted for 22% and 31.04% of MAF respectively. The results indicate that current reservoir operation policy is causing a severe hydrological alteration in the high flow season especially in the month of July. The study concluded that in the case of non-availability of environmental information, hydrological indicators can be used to provide the basic assessment of environmental flow requirements. It is inferred from the results obtained from the study, that the new reservoir operations can fulfil human water needs without disturbing Environmental Flow Requirements.

• Magazine of the Korean Society of Agricultural Engineers
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• v.10 no.1
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• pp.1413-1419
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• 1968

Yochon reservoir was consturcted with an original storage capacity of 202.7 chung-meters. This reservoir receives the water from watershed area of 933.0 chungbo and has irrigated area of 478.0 chungbo. In 1967 a detailed capacity survey of this reservoir was carried out by a new depth-recorder under the scheme of reservoir sedimentation of Agricultural Engineering Research Center. Significant findings are 1. The capacity of the reservoir for the water storage has been reduced by 8.9%(18.066 chung-meters out of the 202.7 chung-meters) since its construction, a period of just 39.0 years. 2. The sediment accumulation in the reservoir represents an average annual soil loss of 0.496mm depth(0.463 chung-meters) of soil from the watershed area of 933.0 chungbo. Eventually the capacity of the reservoir for the water storage will be reducing by about 25%(50.7 chung-meters out of the 202.7 chung-meters)in one hundred years since its construction. We have to set up controlling projects for those reservoir protections from the sediment, soil loss, and other failures. The depth recorder is very useful, convenient, and accurate machine for surveys of reservoir capacity and other river surveys.