• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.440-447
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• 2007

This paper is dealing with recent hot issues related with copper toxicity and its criteria, which was caused by a new government policy relocating some industries discharging priority-water quality pollutants from the watershed of Han River to other regions. Author is not interested in arguments between two sides of anti- and pro-policy but would like to go over status of copper pollution and its management and regulatory policy in Korea. From the data of published Research Journals and Reports, it can be concluded that copper is very common metal not only in the effluent from publically owned wastewater treatment plants, but also as a non-point source pollutant in the rainfall runoff. In addition, there have been very few studies personal interests, not by National Fund Basis. In order to enforce a new regulation, national-wide macro and micro-mass balance work of heavy metals should be performed in advance. In particular, background concentration and measurement errors have to be clearly defined before a new standard or criteria is established. The new standard has to be acceptable in terms of the best available technology and cost.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.149-149
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• 2022

Accurate quantitative evaluation of baseflow contribution to streamflow is imperative to address seasonal drought vulnerability, flood occurrence and groundwater management concerns for efficient and sustainable water resources management in watersheds. Several baseflow separation algorithms using recursive filters, graphical method and tracer or chemical balance have been developed but resulting baseflow outputs always show wide variations, thereby making it hard to determine best separation technique. Therefore, the current global shift towards implementation of artificial intelligence (AI) in water resources is employed to compare the performance of deep learning models with conventional hydrograph separation techniques to quantify baseflow contribution to streamflow of Piney River watershed, Tennessee from 2001-2021. Streamflow values are obtained from the USGS station 03602500 and modeled to generate values of Baseflow Index (BI) using Web-based Hydrograph Analysis (WHAT) model. Annual and seasonal baseflow outputs from the traditional separation techniques are compared with results of Long Short Term Memory (LSTM) and simple Gated Recurrent Unit (GRU) models. The GRU model gave optimal BFI values during the four seasons with average NSE = 0.98, KGE = 0.97, r = 0.89 and future baseflow volumes are predicted. AI offers easier and more accurate approach to groundwater management and surface runoff modeling to create effective water policy frameworks for disaster management.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.951-959
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• 2016

This study was conducted to evaluate observed runoff data collected every 10 minutes at stream gauging stations in Jeju Island using a physically-based model, SWAT. The Hancheon watershed was selected as study area, and ephemeral stream algorithm suggested by previous research was incorporated into the model, which is able to simulate ephemeral runoff pattern of Jeju streams. Simulated runoff and runoff rates were compared to observations during 2008-2013, which showed 'very good' performance rating in Nash-Sutcliffe model efficiency (ME) and determination coefficient ($R^2$). Some observations had problems such that runoff rates were very high for some rainfall events with little amount of antecedent rainfall, and were very low or missing with much rainfall comparing to previous researches. Additionally, regression equation between precipitation and simulated runoff was generated with high degree of correlation. The equation can be utilized to simply predict reasonable runoff, or to investigate and complement the abnormal or missing data of observations on the assumption that modelling results were sufficiently reliable and satisfactory. As results, minimizing the error in calibrating the model by evaluation of observed data would be helpful to accurately model the rainfall-runoff characteristics and analyze the water balance components of watersheds in Jeju Island.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.4
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• pp.87-96
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• 2019

The objective of this study was to develop a general inundation modeling technique considering the effect of drainage delay in the paddy field districts. In most studies, farmland inundation simulations have been conducted using previously developed watershed models. However, the water cycle in the paddy fields has a different structure from that of the general watershed, and the effect of the drainage delay should be considered. In this study, the drainage delay algorithm was developed using water balance equation, and the inundation modeling was performed for inundation-prone paddy fields located near Doowol stream. As a result, the depth of inundation was 43.1 cm and 45.2 cm, respectively, due to the 100-year and 200-year frequency rainfall. With the operation of drainage pump ($0.1m^3/s$), inundation depths decreased by 5.8 cm and 6.0 cm, respectively, and inundation time reduced by 20 hours and 21 hours, respectively for the 100-year and 200-year frequency rainfall. The result showed that the general inundation modeling technique developed in this study could reflect the effect of drainage delay due to the rise of external water level and the flooding reduction effect by operation of drainage pump. The results of this study are expected to be useful to establish measures for damage caused by farmland inundation.

• Journal of Korea Water Resources Association
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• v.33 no.3
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• pp.375-382
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• 2000

The surface hydrology of large watershed is susceptible to several preferred stable states with transitions between stable states induced by stochastic fluctuations. This comes about due to the close coupling of land surface and atmospheric interaction. An interesting and important issue is the duration of residence in each mode. In this study, mean transition tunes between the stable modes are analyzed for the Han River Basin. On the basis of historical data, the nonlinear water balance model is calibrated for the Han River Basin. The transition times between the stable modes in the model are studied based on the stochastic representation of the physical processes and on the calibrated model parameters. This study has implications for prediction of the transition time between stable modes or residence times, that is, the time the system spends in a given stable modes, since this would be equivalent to predicting the duration of drought or wet conditions.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.1293-1297
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• 2010

최근 10년 들어 가뭄과 홍수가 빈번하게 반복되면서 용수공급에 어려움이 많은 것이 사실이다. 특히나 농촌지역, 군, 면단위 지역의 용수공급 문제는 시간이 지날수록 개선이 이루어지고 있으나 시간적으로 공간적으로 개선속도가 늦게 진행되고 있다. 새로운 취수원의 변경, 댐건설 등으로 인하여 새로운 용수공급량의 추정과 용수공급의 배분문제는 아주 중요하다고 할 수 있다. 중소하천유역에서의 물수지 분석은 해당 지역에 대한 안정된 용수를 공급하기 위해 유역내의 장래 용수수요를 산정하고 공급기준년의 자연유량을 비교하여 유역내의 물수지를 예측하고, 공급기준년의 물부족량을 공급하기 위해 필수적으로 선행되어야 하는 요소이다. 갈수시의 물수지 분석은 유역 내에서 발생하는 용수수요의 총량 및 장래수요 증가량과 불규칙한 자연유하량을 비교 검토하여 물 부족 여부를 검토하는 것으로 갈수시에도 하천의 정상적인 기능을 유지하기 위한 수자원의 확보방안을 강구하기 위해 행하는 것이다. 본 연구에서는 증가하는 용수수요와 취수원 변경에 따른 영주시 수자원의 효율적인 이용과 체계적인 용수공급 계획을 수립하기 위하여 지방 2급 하천인 서천상류(죽계천, 남원천,서천)유역 일원에 대한 용수이용현황을 조사하고 장래 용수수요를 추정하여 물수지 분석을 실시하였다.

• Korean Journal of Environmental Agriculture
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• v.28 no.1
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• pp.32-37
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• 2009

This study was conducted to assess the impact of agricultural land use on the water quality in mountain village farmlands. Two soil types, paddy and upland soil were analysed for their chemical properties. Although, pH and organic matter contents were not significantly different to each other, concentrations of available P and exchangeable K and Ca were much higher in upland soil compared with those in paddy soil. The results of water quality analysis indicated that, in Goseong-cheon watershed, the nutrients contents were much higher in downstream area than in upstream area. Particularly, the elevation of $COD_{Mn}$ and T-P were significant during rainy season. When paddy fields coexist with upland fields, SS, T-N, and T-P concentrations in paddy fields were lower than those of upland fields. This may indicate that paddy fields possess an water-purifying ability by absorbing nutrients. This effect may reduce excessive nutrients discharged into the neighboring streams which may cause eutrophication problem. The difference between inflow and outflow of nitrogen and phosphorus during the cultivation period were measured as -98.9 kg $ha^{-1}$ and -29.7 kg $ha^{-1}$, which means that nutrient outflow was higher than inflow. This may suggest that much nutrient was discharged during the crop harvest period.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.1
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• pp.1-10
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• 2016

The objective of this study was to investigate the effects of farming methods on mass balance from paddy rice. The experiment fields were established at Chunpo-myeon, Iksan-si in the Saemangeum watershed. Experiment was performed during the growing season to assess water and mass balances of the study field in 2013. The three different farming practices were applied: conventional (TR-A), drainage outlet heighten (TR-B) and slow release fertilizer use (TR-C). Drainage amount from TR-B was reduced by 28.5 % compared to the TR-A, while the amount from TR-C was similar to that of TR-A. Overall, nutrient concentration of paddy water were similar among the treatments except for T-P. Mean T-P concentration from TR-C was lower than that from TR-A (p-value<0.05). As the results of mass balance, TR-B appeared to reduce nutrient surface loss, substantially by 30.9 % and 40.8 % for T-N and T-P an compared to TR-A. TR-C treatment also demonstrated nutrient load reduction by 38.2 % and 40.1 % for T-N and T-P. The study results showed that water and fertilizer treatments are effective in surface load reduction respectively from paddy fields, and, long-term monitoring and evaluation is needed to confirm the reduction.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.19-32
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• 2007

In Korea, there have been various methods of estimating groundwater recharge which generally can be subdivided into three types: baseflow separation method by means of groundwater recession curve, water budget analysis based on lumped conceptual model in watershed, and water table fluctuation method (WTF) by using the data from groundwater monitoring wells. However, groundwater recharge rate shows the spatial-temporal variability due to climatic condition, land use and hydrogeological heterogeneity, so these methods have various limits to deal with these characteristics. To overcome these limitations, we present a new method of estimating recharge based on water balance components from the SWAT-MODFLOW which is an integrated surface-ground water model. Groundwater levels in the interest area close to the stream have dynamics similar to stream flow, whereas levels further upslope respond to precipitation with a delay. As these behaviours are related to the physical process of recharge, it is needed to account for the time delay in aquifer recharge once the water exits the soil profile to represent these features. In SWAT, a single linear reservoir storage module with an exponential decay weighting function is used to compute the recharge from soil to aquifer on a given day. However, this module has some limitations expressing recharge variation when the delay time is too long and transient recharge trend does not match to the groundwater table time series, the multi-reservoir storage routing module which represents more realistic time delay through vadose zone is newly suggested in this study. In this module, the parameter related to the delay time should be optimized by checking the correlation between simulated recharge and observed groundwater levels. The final step of this procedure is to compare simulated groundwater table with observed one as well as to compare simulated watershed runoff with observed one. This method is applied to Mihocheon watershed in Korea for the purpose of testing the procedure of proper estimation of spatio-temporal groundwater recharge distribution. As the newly suggested method of estimating recharge has the advantages of effectiveness of watershed model as well as the accuracy of WTF method, the estimated daily recharge rate would be an advanced quantity reflecting the heterogeneity of hydrogeology, climatic condition, land use as well as physical behaviour of water in soil layers and aquifers.

• Korean Journal of Ecology and Environment
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• v.40 no.1
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• pp.155-162
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• 2007

Water balance is the major factor in forest ecosystem, and is closely related to the vegetation and topographic characteristics within a watershed. The hydrologic response of a forest watershed was investigated with the hydrological model. The deterministic, lumped parameter model (BROOK90) was selected and used to evaluate the applicability of the model for simulating daily runoff on the steep, forested watershed. The model was calibrated and validated against the streamflow data measured at the Bukmoongol watershed. The deviation in runoff volume $(D_v)$ was -1.7% for the calibration period, and the $D_v$ value for the validation period was 4.6%. The correlation coefficient (r) and model efficiency (E) on monthly basis were 0.922,0.847, respectively, for the calibration period, while the r- and E-value for the validation period were 0.941, 0.871, respectively. Overall, the simulated streamflows were close to the observations with respect to total runoff volume, seasonal runoff volume, and baseflow index for the simulation period. BROOK90 model was able to reproduce the trend of runoff with higher correlation during the simulation period.