• Journal of Korea Water Resources Association
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• v.39 no.10 s.171
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• pp.833-844
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• 2006

The objective of this study is to evaluate the snowmelt effects on the hydrological components, especially on the runoff, by using the soil water assessment tool(SWAT) which is a continuous semi-distributed long term rainfall-runoff model. The model was applied to the basin located in the upstream of the Chungju Dam. Some parameters in the snowmelt algorithm were estimated for the Chungju basin in order to reflect the snowmelt effects. The snowmelt effects were assessed by comparing the simulated runoff with the observed runoff data at the outlet of the basin. It was found out that the simulated runoff with considering the snowmelt component matches more satisfactorily to the observed one than without considering snowmelt effect. The simulation results revealed that the snowmelt effects were noticeable on March and April. Similar results were obtained at other two upstream gauging points. The effect of the elevation bands which distribute temperature and precipitation with elevation was analyzed. This study also showed that the snowmelt effect significantly affects the temporal distribution as well as quantity of the hydrological components. The simulated runoff was very sensitive to the change of temperature near the threshold temperature which the snowmelt can occur. However, the reason was not accounted for this paper, Therefore, further analyses related to this feature are needed.

• Journal of Korean Society on Water Environment
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• v.28 no.4
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• pp.523-530
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• 2012

Runoff, NPS pollution load and flow-weighted mean concentration (FWMC) occurred by snowmelt and rainfall runoff were compared by a variance analysis. Snowmelt runoff ranged between 1,449 and $19,921m^3$. The peak snowmelt runoff was similar to the runoff that occurred by about 40mm/day rainfall. And average snowmelt runoff was not significantly different from the runoff that occurred by 25.5 mm/day rainfall. Average values of SS loads and FWMCs were 5,438 kg/day and 954.9 mg/L, respectively. SS loads and FWMCs were in the similar range with those that occurred by 39.0 mm/day and 53.0 mm/day rainfall, respectively. Daily SS and COD loads and FWMCs occurred by snowmelt and rainfall were analyzed not to be significantly different. Overall assessment led that the NPS pollution loads by snowmelt runoff had a similar characteristics with the loads by about 40 mm/day rainfall runoff. It was recommended that the agricultural fields in snowy region needs to managed not only for rainfall runoff but also snowmelt runoff for an effective water quality management.

• Journal of Korea Water Resources Association
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• v.39 no.10 s.171
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• pp.845-854
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• 2006

Establishment of snowmelt factors is necessary to simulate stream flow using snowmelt models during snowmelt periods. The few observed data related snowmelt was the major cause of difficulty in extracting snowmelt factors such as snow cover area, snow depth and depletion curve. The objective of this study was to extract snowmelt factors using RS, GIS technique and meteorological data. Snow cover maps were derived from NOAA/AVHRR images for the winter seasons from 1997 to 2003. Distributed snow depth was mapped by overlapping between snow cover maps and interpolated snowfall maps from 69 meteorological observation station. Depletion curves of snowmelt area were described from the linear regression equations of each year between the average temperature and snow cover area in Soyanggang-dam and chungju-dam watershed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.1-9
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• 2008

The impact of snow accumulation and snowmelt in rainfall-runoff modelling was analyzed for the Soyanggang dam basin by comparing the measured and simulated discharges simulated by the NWS-PC model. Sugawara's conceptual model was used to simulate the snow accumulation and snowmelt phenomena and NWS-PC model was employed to simulate rainfall-runoff. Parameters in model calibration were estimated by the Multi-step Automated Calibration Scheme and optimized using SCE-UA algorithm in each step. The results of the model calibration and verification show that the model considering snowmelt process is better than the one without consideration of snowmelt under the performance criteria such as RMSE, PBIAS, NSE, and PME. The measured discharge time series has over 60 days of persistence. Correlograms for each simulation showed that the simulated discharge with snowmelt model reproduce the persistence closely to the measured discharge's while the one without snow accumulation and snowmelt model reproduce only 20 days of persistence. The study result indicates that the inclusion of snow accumulation and snowmelt model is important for the accurate simulation of rainfall-runoff phenomena in the Soyanggang dam basin.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.833-844
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• 1998

The objectives of this study are to adopt a snowmelt model for coupling a rainfall-runoff model and to study snowmelt effects for long-term runoff analysis on the northeast mountaneous area in Korea. The NWS temperature-index snowmelt model was selected and tested on the 1,059+,6 km$^2$ Naerinchen basin. It can be observed that the time variations of the computed areal extents of snow cover from the model are well agreement with those of the observe station snowfall records on the Inje meteorological station. It is also evident that the computed soil water contents and river flows indicate quite different behaviors with or without snowmelt model. It is concluded that the snowmelt model works well and the snowmelt effects for multi-decadal river flow computations are important on the study area.

• Journal of Soil and Groundwater Environment
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• v.17 no.5
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• pp.31-39
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• 2012

Chemical and isotopic variations of snowmelt provide important clues for understanding snowmelt processes and the timing and contribution of snowmelt to catchment or watershed in spring. The newly developed model includes a hydraulic exchange between mobile and immobile water (${\omega}$), and isotopic exchanges between both mobile water and ice ($f_1$) and immobile water and ice ($f_2$). Since the new model is based on the mobile-immobile water conceptualization, which is widely used for describing chemical tracer transport in snow, it allows simultaneous calculations of chemical as well as isotopic variations in snowpack discharge. We compare the model results with a study of solute transport and isotopic evolution of snowmelt in snow, using artificial rain-on-snow experiments with conservative anion ($Br^-$). These observations are used to test the newly developed model and to better understand physical processes in a seasonal snowpack where our model simulates the chemical and isotopic variations.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.5
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• pp.37-48
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• 2013

The objective of this study is to assess the impact of potential climate change on the hydrological components, especially on the streamflow, evapotranspiration and snowmelt, by using the Soil Water Assessment Tool (SWAT) for 17 Hanriver middle watersheds of South Korea. For future assessment, the SWAT model was calibrated in multiple sites using 4 years (2006-2009) and validated by using 2 years (2010-2011) daily observed data. For the model validation, the Nash-Sutcliffe model efficiency (NSE) for streamflow were 0.30-0.75. By applying the future scenarios predicted five future time periods Baseline (1992-2011), 2040s (2021-2040), 2060s (2041-2060), 2080s (2061-2080) and 2100s (2081-2100) to SWAT model, the 17 middle watersheds hydrological components of evapotranspiration, streamflow and snowmelt were evaluated. For the future precipitation and temperature of RCP 4.5 scenario increased 41.7 mm (2100s), $+3^{\circ}C$ conditions, the future streamflow showed +32.5 % (2040s), +24.8 % (2060s), +50.5 % (2080s) and +55.0 % (2100s). For the precipitation and temperature of RCP 8.5 scenario increased 63.9 mm (2100s), $+5.8^{\circ}C$ conditions, the future streamflow showed +35.5 % (2040s), +68.9 % (2060s), +58.0 % (2080s) and +63.6 % (2100s). To determine the impact on snowmelt for Hanriver middle watersheds, snowmelt parameters of SWAT model were determined through evaluating observed streamflow data during snowmelt periods (November-April). The results showed that average SMR (snowmelt / runoff) of 17 Hanriver middle watersheds was 62.0 % (Baseline). The annual average SMR were 42.0 % (2040s), 39.8 % (2060s), 29.4 % (2080s) and 27.9 % (2100s) by applying RCP 4.5 scenario. Also, the annual average SMR by applying RCP 8.5 scenario were 40.1 % (2040s), 29.4 % (2060s), 18.3 % (2080s) and 12.7 % (2100s).

• Journal of Soil and Groundwater Environment
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• v.16 no.5
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• pp.82-89
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• 2011

Understanding snowmelt movement to the watershed is crucial for both climate change and hydrological studies because the snowmelt is a significant component of groundwater and surface runoff in temperature area. In this work, a new energy balance budget algorithm has been developed for melting snow from a snowpack at the Central Sierra Snow Laboratory (CSSL) in California, US. Using two sets of experiments, artificial rain-on-snow experiments and observations of diel variations, carried out in the winter of 2002 and 2003, we investigate how to calculate the amount of snowmelt from the snowpack using radiation energy and air temperature. To address the effect of air temperature, we calculate the integrated daily solar radiation energy input, and the integrated discharge of snowmelt under the snowpack and the energy required to generate such an amount of meltwater. The difference between the two is the excess (or deficit) energy input and we compare this energy to the average daily temperature. The resulting empirical relationship is used to calculate the instantaneous snowmelt rate in the model used by Lee et al. (2008a; 2010), in addition to the net-short radiation. If for a given 10 minute interval, the energy obtained by the melt calculation is negative, then no melt is generated. The input energy from the sun is considered to be used to increase the temperature of the snowpack. Positive energy is used for melting snow for the 10-minute interval. Using this energy budget algorithm, we optimize the intrinsic permeability of the snowpack for the two sets of experiments using one-dimensional water percolation model, which are $52.5{\times}10^{-10}m^2$ and $75{\times}10^{-10}m^2$ for the artificial rain-on-snow experiments and observations of diel variation, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.457-467
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• 2014

This study is to evaluate the snowmelt impact on dam inflow for the Chungju Dam watershed $6,642.0km^2$ using Terra MODIS (Moderate-Resolution Imaging Spectroradiometer) and Soil and Water Assessment Tool (SWAT). To determine the SWAT snowmelt parameter; snow cover depletion curve (SCDC) the snow depth distribution (SDD) using Terra MODIS was used, the snow depth was spatially interpolated using snowfall data of ground meteorological stations. For 10 sets (2000-2010) data during snowmelt period (November-April), the sno50cov parameter, that is, the 50% coverage at a fraction of SCDC which determines the shape of snow depletion process, showed the values of 0.4 to 0.7. The SWAT model was calibrated with average $R^2$ of 0.54 using the sno50cov of each year. The 10 years average streamflow during snowmelt period was 104.3 mm which covers 12.0% of the annual streamflow.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.453-459
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• 2012

In this study, Song-Cheon river Basin located at Dae-kwan-lyong Meyn in Kang-Won Province was monitored to analyze characteristics of non-point source pollution during the snowmelt period. The characteristics of NPS pollution such as runoff, change in water quality and pollutant loads by snowmelt were investigated from 23th February 2010 to 27th April 2010. The results showed that The climate change effects flow, turbidity and concentration of SS and COD with showing similar trend of fluctuation. Daily pollutant loads per unit area were SS 74.43 kg/ha/day, COD 1.25 kg/ha/day, BOD 0.21 kg/ha/day, TN 0.717 kg/ha/day, TP 0.141 kg/ha/day and the flow weight mean concentration has been SS 985.97 mg/L, COD 16.28 mg/L, BOD 2.67 mg/L, TN 9.302 mg/L, TP 1.834 mg/L, respectively. The flow and pollutant loads both of SS and of COD significantly increased during the snowmelt period. Because structurally loosen soil by freezing and thawing deteriorates water quality, research and management measures will be needed.