• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.10-17
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• 2012

The middle and lower reaches of the Kum River system become stagnant in dry seasons with florishing of phytoplankton. In this study primary productivity of phytoplankton were measured by the C-14 uptake method and the P-I model method at seven main stream sites of the Kum River from the Daechung Dam outet to the river mouth. Nutrients (TN, TP, DIP, TIN) concentrations were measured in the mainstream and tributaries and compared with the variation of assimilation number. The range of primary productivity was $40{\sim}4,558mgC{\cdot}m^{-2}{\cdot}day^{-1}$ and it was higher than those of lentic ecosystems in Korea. Average TN and TP were $4.1mgN{\cdot}L^{-1}$, $70.6mgP{\cdot}m^{-3}$, respectively. Tributaries showed higher nutrient concentrations than the main stream. After two major tributaries merged with the discharging water of the Daechung Dam phyotplankton biomass and productivity increased drastically and remained at the similar eutrophic level through the downstream reach to the river mouth. Both dissolved phosphorus and nitrogen concentrations showed positive correlation with assimilation number of phytoplankton. In conclusion phytoplankton productivity is at the level of eutrophic water and it was higher than usual lentic habitats. Nutrient concentrations are critical factors in controlling productivity in the lower reach of the Kum River.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.847-857
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• 1994

FESWMS-2DH developed by the U.S. Department of Transportation based on two-dimensional shallow water wave equation is used in this study to simulate the flow characteristecs of the river reach between Chamsil and Shingok submerged weirs, which acts as a tidal river under low flow conditions. The model uses Galerkin F.E.M and meshes are composed of triangular or quadrangular elements. The model shows accurate and stable results concerning mass conservation as well as velocity distribution and water surface elevation. The results obtained in the present study may provide useful informations on the planning of river pollution abatement measures and artificial structures.

• Journal of Ecology and Environment
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• v.40 no.2
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• pp.107-119
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• 2016

Background: Previous studies on the biological integrity on habitat and landuse patterns demonstrated ecological stream health in the view of regional or macrohabitat scale, thus ignored the mesoscale habitat patterns of pool, riffle, and runs in the stream health analysis. The objective of this study was to analyze influences on the mesohabitat structures of pool, riffle, and run reaches on the fish guilds and biological integrity in Geum-River Watershed. Results: The mesohabitat structures of pool, riffle, and run reaches influenced the ecological stream health along with some close relations on the fish trophic and tolerance guilds. The mesoscale components altered chemical water quality such as nutrients (TN, TP) and BOD and these, then, determined the primary productions, based on the sestonic chlorophyll-a. The riffle-reach had good chemical conditions, but the pool-reach had nutrient enrichments. The riffle-reach had a predominance of insectivores, while the pool-reach has a predominance of omnivores. Also, the riffle-reach had high proportions of sensitive fish and insectivore fish, and the pool-reach had high proportions of tolerant species in the community composition. The intermediate fish species in tolerance and omnivorous fish species in the food linkage dominated the community in the watershed, and the sensitive and insectivorous fishes decreased rapidly with a degradation of the water quality. All the habitat patterns were largely determined by the land-use patterns in the watershed. Conclusions: Trophic guilds and tolerance guilds of fish were determined by land-use pattern and these determined the stream health, based on the Index of Biological Integrity. This study remarks the necessity to include additional variables to consider information provided by mesohabitats and land-use distributions within the selected stream stretch. Overall, our data suggest that land-use pattern and mesohabitat distribution are important factors to be considered for the trophic and tolerance fish compositions and chemical gradients as well as ecological stream health in the watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.58-58
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• 2011

The Texas Commission on Environmental Quality(TCEQ) WAM(Water Availability Modeling) System consists of the generalized Water Rights Analysis Package(WRAP) river/reservoir system water management simulation model, 22 sets of WRAP hydrology and water rights input files for the 23 river basins of Texas, geographic information system tools, and other supporting databases. The WRAP/WAM modeling system, as routinely applied since the late 1990s, has not included consideration of water quality. Recently developed WRAP-SALT(Water Rights Analysis Package) is designed primarily for computing concentration frequency statistics and supply reliability indices at locations of interest in a river system for alternative water development and management scenarios. Though motivated primarily by natural salt pollution, WRAP-SALT water quality modeling features are applicable to essentially any conservative water quality constituent. The Brazos River studies discussed in this paper focus on total dissolved solids, though the available observed data also includes chloride and sulfate which can be modeled as individual constituents. The WRAP-SALT salinity input file contains loads or concentrations of salinity inflows during each month of the hydrologic period-of-analysis and reservoir storage at the beginning of the simulation. The WRAP-SALT model computes salt loads and concentrations for each control point of a river/reservoir system for inflows and outflows during the month and end-of-month reservoir storage for each month of the hydrologic period-of-analysis, for given loads entering the system. River reaches connect control points. The mass balance algorithms proceed from upstream to downstream, with outflow from one river reach contributing to inflow to the next downstream reach. In a given month, for each control point in sequence, the inflow loads are first computed. Loads and concentrations of outflows and reservoir storage at the control point are then determined. Complete mixing during the month is assumed at locations without reservoir storage.

• Journal of Korea Water Resources Association
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• v.40 no.11
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• pp.909-920
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• 2007

River restoration and environmental improvement projects have been peformed by social needs, therefore methodology for evaluating such projects must be provided. The PHysical HABitat SIMulation system (PHABSIM) is proposed as a tool for the assessment of hydraulic habitat suitability for aquatic species related to flow regime in river. This study evaluates the change of physical habitat for Zacco platypus according to small dam removal and the model suitability by applying PHABSIM to the reach where small dam was removed. It is shown that the physical habitat is generally increased and improved where the small dam was removed. However, physical habitat in the spawning stage that has a weak swimming speed is decreased by increased flow velocity in the upstream area of small dam, so proper countermeasure for that condition should be needed. Consequently, PHABSIM can be effectively used to provide methodology for assessment and necessity of various river projects including a removal of out-aged hydraulic structures.

• Journal of the Korean Geographical Society
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• v.42 no.3 s.120
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• pp.388-404
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• 2007

This study interprets evolution of fluvial terraces along the four Yeongdong- and Yeongseo streams such as Naerin River, Yeongok River, Golji River and Osip River, in Gangwon Province based on the tectonics. The results from the analyses of the distribution pattern of fluvial terraces and incision rates of rivers show distinctively the evidence as the axis of uplift by Taebaek Mountains, especially on the 4th, 5th and 6th terraces in upper reach of Osip River among the four streams. The axis of uplift extends to the zone of $30\sim40km$ in width as well as the divide. The difference of uplift between upper and middle reaches of Naerin River and total reach of Golji River wasn't found from the height from riverbed by the active uplifting along all reaches, estimated to be set in inner area of uplift zone. Incision rate of period between formation age of 2nd terrace and 1st terrace is calculated $0.13\sim0.22m/ka$, and incision rate of period between formation age of 1st terrace and Present is diversely calculated $0.17\sim0.27m/ka$ by the climatic discrepancy between the two periods. The incision rate of Yeongdong streams whose mouths reach to the sea level eroded actively more than Yeongseo streams in the uplift zone. And Yeongdong streams between formation age of 1th terrace and present appears to much higher than that of Yeongseo streams, due to active down-cutting in oder to balance against the sea level.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1203-1213
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• 2014

The hydraulic characteristics and the patterns of riverbed change had been analysed by HEC-RAS simulation in a reach of Cheong-mi river with and without weir. The corresponding physical disturbance had been evaluated with the method suggested by K-water (2008). The occurrences of low physical disturbance score coincide with the corresponding high bed changes by weir installation. The effects of physical disturbance coincide with the patterns of riverbed change along river reach which shows riverbed change is the important factor to physical disturbance. In case of installation of additional weirs at up and down stream sections of no disturbance effect by the existing weir, no physical disturbances occur in certain sections with confirming the appearance of the similar disturbance scores between the simulation results of with and without additional weir installations. In case of installation of additional weirs at up and down stream sections of disturbance effect margins by the existing weir, physical disturbances occur at every section. In case of installation of additional weirs at up and down stream sections within disturbance effect by the existing weir, low physical disturbance scores are given at every section because of superposition of disturbance along river reach. The physical disturbance would be minimized such that the additional weir is installed with sufficient distances of no disturbance and bed change effects along river reach.

• Water Engineering Research
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• v.6 no.3
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• pp.113-122
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• 2005

Periphyton is known to be one of major primary producers for river ecosystem. While the growth of periphyton usually observed on the stone surface in gravel river, the large growth of periphyton is sometimes seen even in sand river with relatively small river discharge. In the present study, field observations and numerical simulations were performed to investigate the growth of periphyton in sand river. In the field observation, the growth of periphyton on fixed sand bed was measured weekly. The results of the field observations show that the large growth of periphyton occurs in sand river until the bed material sands have not moved. An integrated numerical simulation model is presented to describe the growth of periphyton at observed river reach, and a series of numerical simulations were performed to study the effect of river discharge on growth of periphyton in the sand river. The results of the numerical simulations show that the net primary production of periphyton decreases with the river discharge. These results suggest that the reduction of river discharge at ordinary water stage strongly affects the primary productivity of periphyton even in sand river.

• Journal of Korea Water Resources Association
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• v.42 no.8
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• pp.619-629
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• 2009

The objective of this study is to estimate bed-resistance in gravel-bed rivers using the equivalent roughness height($k_s$). We calculated the friction factor(f) with the measured data from 8 domestic gravel-bed rivers and investigated the size distributions of the bed materials. The averaged $k_s$ in each cross-section, which is determined under the hypothesis that the vertical velocity distribution follows the logarithmic law, is compared with the reach $k_s$ which is calculated with the cumulative grain diameter distribution curve of bed materials. Moreover, the applicability of existing formulae, such as Strickler type equations, is examined by comparing with Manning's n value converted from the $k_s$. According to the results, the reach $k_s$ proves to be a good indicator of representative characteristic of bed materials in a reach, and the Manning's n based on the reach $k_s$ is appropriate for practical estimation of the bed-resistance, for RMS errors between calculated and measured Manning's n is less than 0.003. The correlation between the $k_s$ and specified bed-material size($D_i$) is very low, so it is difficult to select a proper one among the existing empirical equations.

• Journal of Korea Water Resources Association
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• v.37 no.1
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• pp.55-66
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• 2004

The Hapchon Dam, located upstream of the Hwang River, Korea, was constructed in December, 1988. Due to the lack of storage of water, the dam gate has not been operated during last ten years. Thus, a new ecosystem has been established at the downstream part of the dam. This is not a common phenomenon which can be found elsewhere in the country. The present study investigates the effect of flow regime change on the river morphology and vegetation cover in the downstream river reach after the dam construction. The analysis of flow regime is carried out, and the changes in bed elevation and in channel cross sections are examined. Site investigations including tree ring tests are also performed. The increase in the vegetation cover is estimated by comparing aerial photographs taken before and after dam construction.