• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.125-135
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• 2009

Reliable long-term flows by SWAT-K model were applied to the relationship between stream flow and pollutant load derived from 8-day measured data of Ministry of Environment (MOE) in order to obtain continuous loadograph and evaluate accuracy in water quality modeling for the Chungju dam watershed. The measured flow were compared with flow duration curve from the model, and it showed that measured values corresponded to the almost full range of stream flow conditions except at Odae A. And there was significant relationship ($R^2=0.60{\sim}0.97$) between measured flow and water quality load at all unit-watersheds. Applying this relationship to simulated flows, continuous loadograph was obtained and compared with modeled pollutant loads. Although there were some differences during some dry and flood seasons, those were not significant and overall trend showed a good agreement. From the results, we would be able to derive a continuous loadograph based on measured data at total maximum daily loads (TMDLs) unit-watersheds on a national scale, in which stream flow and water quality have been measured at 8-day intervals since 2004, and this could be helpful to utilize distributed water quality models with difficulty in calibrating and validating parameters from lack of measured data at present.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.6
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• pp.97-109
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• 2020

The objective of this study was to assess spatial variation of the target water quality criteria and excess rate in Nakdong river basin after the Total Maximum Daily Loads (TMDLs). For this, 41 total water quality monitoring stations were selected BOD and T-P data were collected from 2003 to 2019. The annual average water quality of BOD and T-P were calculated and compared with the target water quality for each stations by peroid. As a result of analyzing the BOD, Kumho A, Nakbon F, Namgang D, Miryang B, Wicheon B and Hoecheon A exceeded the target water quality criteria for two consecutive times. For T-P, Nakbon N, Naeseung B, Miryang A, Hwanggang A and Hoecheon A exceeded the target water quality criteria twice in a row. In the case of T-P, the target water quality excess rate was relatively low after the TMDLs implementation compared to before the TMDLs implementation. However, in the case of BOD, there was no difference in the target water quality excess rate before and after TMDLs. As a result, the overall annual average water quality shows a decreasing trend, but it is necessary to manage the water quality for the Nakdong river basin that exceed the target water quality.

• Journal of Korean Society on Water Environment
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• v.32 no.4
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• pp.349-356
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• 2016

Total Maximum Daily Loads (TMDLs) System has been used to improve water quality in the Youngsan·Tamjin river basin since 2004. The Basic Policy of TMDLs sets up the standard flow based on the average dry condition or mid-range flow during the last 10 years. However, Target Water Quality (TWQ) assessment on TMDLs has been used to evaluate water quality through eight-day intervals over 36 times a year. The results for allocation evaluation and target water quality evaluation were different from each other in the same unit watershed during the first period. In order to improve the evaluation method, researchers applied Load Duration Curve (LDC) to evaluate water quality in nine unit watersheds of the Youngsan·Tamjin river basin. The results showed that achievement rates of TWQ assessment with the current method and LDC were 67~100% and 78~100%, respectively. Approximately 11% of the achievement rates with use of LDC were higher than those with use of the current method. In conclusion, it is necessary to review the application of the LDC method in all Four Major River Watersheds.

• Journal of Korean Society on Water Environment
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• v.27 no.5
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• pp.719-728
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• 2011

The results of investigation on the water quality of the unit watersheds in the Yeongsang/Seomjin River indicate that $BOD_5$, SS, T-P decrease in most of the unit watersheds. However, $COD_{Mn}$ and T-N increase since the Total Maximum Daily Loads (TMDLs). It is thought that $COD_{Mn}$, which is included non-biodegradable matters, is difficult to decrease only using by conventional biological treatment facilities and T-N is affected by non-point source, etc. The results of assessment on 3 years $BOD_5$ indicate that most of the unit watersheds were being improved except Yeongbon A, Seombon C and Yocheon B. In addition, it was found that T-P were also being improved except Yocheon B and Hwangryeong A. Consequently, water qualities of the unit watersheds have been improved in many cases since the TMDLs.

• Journal of Korean Society on Water Environment
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• v.28 no.6
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• pp.859-865
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• 2012

It is necessary to evaluate performances hitherto carried out in the management of Total Maximum Daily Loads (TMDLs) and to set up direction so that this system can be improved continuously in the future. This study was investigated load allocation achievement ratio, water quality goal achievement ratio and interrelation between water quality goal and load allocation for the first period (2004~2010). Load allocation achievement and BOD water quality goal achievement ratio were 50% and 73% in Guem River Basin, respectively. The main reason for excess of load allocation and shortfall of water quality goal were unfulfilled reduction plan and pollution sources increment. Therefore, it is necessary to develop enhanced pollution sources prediction method and make a list realizable reduction plan. 63% of the unit watershed was not interrelation between water quality goal and load allocation. The reason why water quality goal and load allocation had not correlation were water quality of upper unit watershed, increment of inflow quantity, effluent water quality of wastewater treatment plant affected the unit watershed, increment of inner productivity by algae, water quality deterioration during the specific period, river management flow, etc.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.652-656
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• 2007

The major streams in South Korea have established the TMDL(Total Maximum Daily Loads) regulation for just 4 years. Traditional concepts in water quality management in South Korea are based upon the selection of a design streram flow which is 10-year averged flow exeedance probability 75%(Q275). That is, a single flow value based upon average long term flow conditions is chosen for application in dilution calculations, permit design, water quality modeling, etc. While these TMDLs seems to satisfy the requirement of the target water quality regulations, they have contributed little to any watershed/waterbody assessment and restoration plans. These types of TMDLs do little to characterize the problems the TMDLs are intended to address. For TMDLs to be more beneficial in the assessment and implementation process, TMDLs should reflect adequate water quality across flow conditions rather than at a single flow value such as average daily flow. In this paper, we developed LDC (load duration curve) methodology for theevaluation of Korean TMDL evaluation based on watershed scaled, physically based on SWAT(Soil and Water Assessment Tool) model.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.497-509
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• 2019

After the Total Maximum Daily Loads(TMDLs) was applied, it became beyond the limit of concentration management. However, it does not adequately reflect the characteristics of various watersheds, and causes problems with local governments because of the standard flow set. Thus, in this study, the Han River system is organized into four groups in estimating the Pollution Contribution by applying the Flow Duration Curve(FDC) created by the daily flow of data from the HSPF. And the method of this study is expected to be valuable as basic data for the TMDLs. As a result, Group I contains the main watersheds with no large hydraulic structures and tributary watersheds. There is no specificity in the FDC and the Pollution Contribution is estimated as rainfall runoff. Group II contains watersheds near the city where the FDC is maintained above a certain level during the Low Flow Conditions and the Pollution Contribution is estimated as the discharge flow of large scale point pollution facilities. Group III contains the main watersheds in which the large hydraulic structures are installed and FDC is curved in the Low Flow Conditions. So the Pollution Contribution is estimated as the water quality of the large hydraulic structures. Group IV contains the upstream in mainstream watersheds in which the large hydraulic structures are installed and the FDC is disabled before the Low Flow Conditions. As the flow is concentrated in the High Flow Conditions, the non-point pollution sources are estimated as the Pollution Contribution.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.426-435
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• 2012

The variation of stream flow is the one of the most important factors which influence on that of water quality in the unit watershed. The target water quality goal is established and permissible load is allotted in the base of the standard flow condition along with its water quality for the management of Total Maximum Daily Loads (TMDLs). A standard flow selected could cause problems in the load allotment if it was not properly arranged. This study reviewed the acquisition of water quality data, the self-variation and the retainability in water quality on the specific flow conditions. This study also proposed the median and the adjusted average flow condition out of general flow conditions as alternative standard flow conditions. It is considered that the alternatives can make the water quality data easily acquired and the water quality representativeness more enhanced on the standard flow conditions.

• Journal of Korean Society on Water Environment
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• v.25 no.4
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• pp.481-493
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• 2009

This study was conducted to performance appraisal of Total Maximum Daily Loads (TMDLs), especially in terms of performance on development & reduction plan and water quality status of unit watershed. Because load allocations for pollution sources were predicted redundantly by uncertainty of prediction, TMDLs master plan has been frequently changed to acquire load allocation for local development. Therefore, It need to be developed more resonable prediction techniques of water pollution sources to preventing the frequent change. It is suggested that the reduction amount have to be distributed properly during the planning period. In other words, it has not to be concentrated on the specific year (especially final year of the planning period). The reason why, if the reduction amount concentrate on the final year of the planning period, allotment loading amount could not be achieved in some cases (e.g., insufficiency of budget, extension of construction duration). If the development plan was developed including uncertain developments, it is necessary to be developed reduction plan considered with them. However, some of the plans in the reduction plan could not be accomplished in some case. Because, it is not considered financial abilities of local governments. Consequently, development plan must be accomplished to avoid uncertain developments, and to consider financial assistance to support the implementation of effective plan. Water quality has been improved in many unit watersheds due to the TMDLs, especially in geum river and yeongsang/seomjin river.

• Journal of Korean Society on Water Environment
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• v.30 no.3
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• pp.351-360
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• 2014

The allocation of margin of safety (MOS) at a uniform rate to all areas of the unit watershed makes it very difficult to keep the load allotment stable in the area for lack of reduction measures like forest land. This study developed an equation to calculate margin of safety differentially according to the regional characteristics. The equation was formulated on the basis of the regional characteristic factors such as a load contribution factor for land use type and a site conversion factor for the unit watershed. The load contribution factor represents a contribution of loads from a particular land use. The site conversion factor was derived from the site conversion ratio of a unit watershed. Margin of safety for the non-point pollution load in the land use sector decreased by 20~25% in three river basins. The margin of safety in the unit watersheds with low site occupation ratios decreased in high rate, while in the unit watersheds with large urban area decreased in low rate. With the application of the differential margin of safety considering regional characteristics, not only the reduction of pollution loads can become lighter but also it can be easier to develop plans for Total Maximum Daily Loads (TMDLs) even where the reduction measures are not available.