Non-point Source Pollution Load Research Articles

Analysis on Water Pollution Characteristics of Typical Urban River-Taking the Zaohe River in Xi′an City as an Example

Zaohe River is a main pollution and flood discharge river in Xian city. Its water quality is affected not only by the point source pollution (PSP), but also by the non-point source pollution (NSP) to some extent. Water flow and water quality of Zaohe River are monitored during the flooding and non-flooding periods from April in 2010 to October in 2011. The results indicated that: 1) The concentration of COD, TP, NH3-N, and TN are exceed the Environmental quality standard grand Ⅴ for surface water (GB3838-2002 of China). 2) The concentration of COD is increasing from upstream to downstream. The concentration of TP, NH3-N, and TN increase firstly and then decrease. The change of NO3-N is small and the concentration of Cr is the lowest in the heavy metal pollutants. 3) The variations of pollutant concentration are smaller during the non-flooding periods than the flooding periods at Caotan section. The NSP load is lower than PSP in the flood period, and the NSP load ratio of SS, COD, NH3-N, NO3-N, TN, DP and TP is 14%, 2.0%, 5.1%, 6.0%, 7.4% and 4.2% separately. 4) The PSP plays the important role in the pollution abatement of Zaohe River，but the NSP can not be ignored, too.

토지피복도 자료원에 따른 대청댐유역 수질특성 비교

This study compared the influence of water quality according to the data sources of spatial information. Firstly, land cover map was constructed through image classification of Daecheong-dam basin and the accuracy of image classification from satellite image showed high as 88.76% in comparison with the large-scaled land cover map in Ministry of Environment, to calculate Event Mean Concentration (EMC) by land cover that impact on the evaluation of nonpoint source pollutant loads. Also curve number and direct runoff were calculated by spatial overlay with soil map and land cover map from image classification. And Seokcheon and Daecheong-Dam basin showed high in the analysis of curve number and direct runoff. Samgacheon-Joint and Sokcheon-Downstream basin showed high in the nonpoint source pollutant loads of BOD from direct runoff and EMC. And Samgacheon-Joint and Bonghwangcheon- Downstream basin showed high in the nonpoint source pollutant loads of TN and TP. Nonpoint source pollutant loads from image classification were compared with those by the land cover map from Ministry of Environment to present the effectivity of nonpoint source pollutant loads from satellite image. And Daecheong-Dam Upstream basin showed high as 10.64%, 11.70% and 20.00% respectively in the errors of nonpoint source pollutant loads of BOD, TN, and TP. Therefore, it is desirable that spatial information including with paddy and dry field is applied to the evaluation of nonpoint source pollutant loads in order to simulate water quality of basin effectively.

Impacts of climate and land-use changes on the migration of non-point source nitrogen and phosphorus during rainfall-runoff in the Jialing River Watershed, China

Summary The loss of nitrogen and phosphorus via non-point source (NPS) pollution in the Jialing River Watershed has become the main pollution sources of river waters in the Three Gorges reservoir area in the past decades, while climatic conditions and human activities directly affect changes of rainfall-runoff and land use types which are closely related to NPS pollution. This study is to assess the impact of climate change on hydrological behavior considering future land-use types and rural residential area and their propagation to NPS pollution loads. An integrated pollution load model composed of regional climate, the Semi-distributed Land Use based Runoff Processes (SLURPs) hydrological model and the improved export coefficient approach within a single framework was explored and developed to assess impacts of climate and land-use changes on NPS pollution load. Climate data for the Special Report on Emissions Scenarios (SRESs) future scenario B2 from Met Office Hadley center were generated and used as the input data for the runoff and NPS load evaluation of the Jialing River Watershed and the Markov process was used to forecast changes of land use types, respectively. Simulations of present and future regional NPS pollution from land use, livestock and poultry breeding, and agricultural population over the Jialing River Watershed were performed to investigate the potential impacts of global climate change on river water quality using the established model. Results demonstrate that: (1) Annual pollution load would obviously change due to variations of runoff and livestock and poultry breeding, the largest growth months in one year for total nitrogen (TN) and total phosphorus (TP) load are both in June, which is in accordance with changes of rainfall amount. (2) The impacts of global climate change on pollution load are relatively greater when compared to the impacts of future livestock and poultry breeding increase or agricultural population reduction; the effects from runoff increment leads to approximately 28.6% and 22.5% increases of TN and TP pollution load, respectively. And (3) the impacts of land-use change have shown insignificant effect due to soil conservation measures, whereas the impacts of rural residential area account for great proportion changes, of which about 5% of its increases are contributed to the increase of livestock and poultry breeding; but the biggest contribution rate is still from the output of different land use types. These data will be useful and valuable in evaluating potential NPS pollution load for the control of watershed pollution in the future and understanding its migration and transformation in a large-scale watershed where meteorological and underlying surface data are mutative.

볏짚 피복에 의한 밭 비점원오염 저감효과 분석을 위한 HSPF 모델링

This study is to assess the reduction of non-point source pollution loads for rice straw surface covering of upland crop cultivation at a watershed scale. For Byulmi-cheon watershed (<TEX>$1.21km^2$</TEX>) located in the upstream of Gyeongancheon, the HSPF (Hydrological Simulation Program-Fortran), a physically based distributed hydrological model was applied. Before evaluation, the model was calibrated and validated using 9 rainfall events. The Nash-Sutcliffe model efficiency (NSE) for streamflow was 0.62~0.78 and the NSE for water quality (Sediment, T-N, and T-P) were 0.68, 0.60, and 0.58 respectively. From the field experiment of 16 rainfall events, the rice straw covering reduced surface runoff average 10 % compared to normal surface condition. By handling infiltration parameter (INFILT) in the model, the value of 16.0 mm/hr was found to reduce about 10 % reduction of surface runoff. For this condition, the reduction effect of Sediment, T-N, and T-P loads were 87.2, 28.5, and 85.1 % respectively. The rice straw surface covering was effective for removing surface runoff dependent loads such as Sediment and T-P.

Small-scale watershed extended method for non-point source pollution estimation in part of the Three Gorges Reservoir Region

Non-point source (NPS) pollution has been increasingly recognized as a major contributor to the declining quality of aquatic environment in recent years. Because of the data shortage, the non-point source loads estimation in the large-scale watershed is always difficult in most developing countries. In this study, small-scale watershed extended method (SWEM) was introduced with a case study in the middle part of Three Gorges Reservoir Region (TGRR). Small-scale watershed extended method is the method which uses physical-based models in some small typical catchments of the targeted large watershed, and then the parameters obtained from those small catchments are extended to the surrounding area until the non-point source pollution loads in the entire watershed or region are obtained. The selected small catchments should have sufficient data. Here, the middle part of the Three Gorges Reservoir Region, about 12,500 km2, was chosen as the targeted region for the case study. In this region, considering the data availability, Xiaojiang River was screened as a typical watershed and was simulated with Soil and Water Assessment Tool model through accurate parameter calibration and validation. And then the parameter group obtained in Xiaojiang River Watershed was extended to the entire study area to quantify the total non-point source pollution loads. After which, the spatio-temporal characteristics of the non-point source pollution in the middle part of the Three Gorges Reservoir Region were analyzed, as well as the pollution from each tributary and different under layer surface conditions. The small-scale watershed extended method provides a practical approach for non-point source pollution loads estimation in the large-scale watershed or region.

Predicting Nitrogen Loading With Land-Cover Composition: How Can Watershed Size Affect Model Performance?

Watershed-wide land-cover proportions can be used to predict the in-stream non-point source pollutant loadings through regression modeling. However, the model performance can vary greatly across different study sites and among various watersheds. Existing literature has shown that this type of regression modeling tends to perform better for large watersheds than for small ones, and that such a performance variation has been largely linked with different interwatershed landscape heterogeneity levels. The purpose of this study is to further examine the previously mentioned empirical observation based on a set of watersheds in the northern part of Georgia (USA) to explore the underlying causes of the variation in model performance. Through the combined use of the neutral landscape modeling approach and a spatially explicit nutrient loading model, we tested whether the regression model performance variation over the watershed groups ranging in size is due to the different watershed landscape heterogeneity levels. We adopted three neutral landscape modeling criteria that were tied with different similarity levels in watershed landscape properties and used the nutrient loading model to estimate the nitrogen loads for these neutral watersheds. Then we compared the regression model performance for the real and neutral landscape scenarios, respectively. We found that watershed size can affect the regression model performance both directly and indirectly. Along with the indirect effect through interwatershed heterogeneity, watershed size can directly affect the model performance over the watersheds varying in size. We also found that the regression model performance can be more significantly affected by other physiographic properties shaping nitrogen delivery effectiveness than the watershed land-cover heterogeneity. This study contrasts with many existing studies because it goes beyond hypothesis formulation based on empirical observations and into hypothesis testing to explore the fundamental mechanism.

Evaluating spatial interaction of soil property with non‐point source pollution at watershed scale: The phosphorus indicator in Northeast China

To better understand the spatial dynamics of non-point source (NPS) phosphorus loading with soil property at watershed scale, integrated modeling and soil chemistry is crucial to ensure that the indicator is functioning properly and expressing the spatial interaction at two depths. Developments in distributed modeling have greatly enriched the availability of geospatial data analysis and assess the NPS pollution loading response to soil property over larger area. The 1.5km-grid soil sampling at two depths was analyzed with eight parameters, which provided detailed spatial and vertical soil data under four main types of landuses. The impacts of landuse conversion and agricultural practice on soil property were firstly identified. Except for the slightly bigger total of potassium (TK) and cadmium (Cr), the other six parameters had larger content in 20–40cm surface than the top 20cm surface. The Soil and Water Assessment Tool was employed to simulate the loading of NPS phosphorus. Overlaying with the landuse distribution, it was found that the NPS phosphorus mainly comes from the subbasins dominated with upland and paddy rice. The linear correlations of eight soil parameters at two depths with NPS phosphorus loading in the subbasins of upland and paddy rice were compared, respectively. The correlations of available phosphorus (AP), total phosphorus (TP), total nitrogen (TN) and TK varied in two depths, and also can assess the loading. The soil with lower soil organic carbon (SOC) presented a significant higher risk for NPS phosphorus loading, especially in agricultural area. The Principal Component Analysis showed that the TP and zinc (Zn) in top soil and copper (Cu) and Cr in subsurface can work as indicators. The analysis suggested that the application of soil property indicators is useful for assessing NPS phosphorus loss, which is promising for water safety in agricultural area.

SWAT 모형을 이용한 두 인접 하천유역간의 비점오염 유출특성 비교연구

This study is to assess the runoff characteristics of nonpoint source pollution loads for Jecheon and Jangpyeong stream watersheds located in the upstream of Chungju lake. The SWAT (Soil and Water Assessment Tool), a physically based distributed hydrological model was calibrated and verified using 5 years (2006 to 2010) streamflow and water quality data. The Nash-Sutcliffe model efficiency for streamflow was 0.60~0.92 and the determination coefficients for sediment, Total Nitrogen (T-N), and Total Phosphorous (T-P) were 0.53~0.71, 0.51~0.91 and 0.38~0.85 respectively. The results showed that the Sediment, T-N, and T-P of Jangpyeong stream were 40.0~60.9 %, 34.8~64.1 % and 76.5~83.9 % higher than Jecheon stream watershed during wet days. The results evaluated high NPS loads at Jangpyeong stream because the percentage of urban and upland crop cultivation area Jangpyeong stream watershed was higher than Jecheon stream watershed.

Spatial Distribution of Non-Point Source Pollution in Nansihu Watershed Based on SWAT Model

Non-point source (NPS) pollution load of N and P in Nansihu watershed were simulated based on SWAT model. The Sihe watershed was selected as typical watershed for east of the lake, and the Dongyu watershed was selected as typical watershed for west of lake. The two typical watersheds were simulated respectively, and then the models were used to simulate the other rivers basins in the Nansihu watershed. Data collected in the period from 2001 to 2007 was used for calibration, while data collected from 2008 to 2010 was used for validation. Then the spatial distribution of NPS pollution in Nansihu watershed (2010) was simulated with the validated model. The result indicated that the SWAT model could simulate the no-point source pollution in Nansihu watershed with high-precision. The watershed was polluted seriously with N and P. The TN was mainly composed of dissolved form, and the TP was mainly composed of adsorbed form.

Estimation on Emission of Nonpoint Source Pollution of Nitrogen and Phosphorus in Different Catchments of the Chaohu Lake Basin, China

In order to estimate nonpoint source pollution loading of the Chaohu Lake Basin, the total nitrogen, total phosphorus of sediment, soil and water samples in five typical sub-catchments have been measured. Combining with routine monitoring data of the five sub-catchments of the Chaohu Lake, emission of nonpoint source pollution from these catchments were described and estimated with the reformative practical-mean concentration method. The results indicated that nonpoint source pollution contributed 79 % total phosphorus and 58 % total nitrogen to total loading. Thus, nonpoint source pollution was the primary cause of degrading water quality of the Chaohu Lake. The total nitrogen and total phosphorus were mainly from Hangbu-fengle River and Nanfei-dianbu River. Therefore, among five effluents of the Chaohu Lake, Hangbu-fengle River and Nanfei-dianbu River were the dominant sources for degrading water quality of the Chaohu Lake.

Assessment of Runoff and Sediment Yields Using the AnnAGNPS Model in a Three-Gorge Watershed of China

Soil erosion has been recognized as one of the major threats to our environment and water quality worldwide, especially in China. To mitigate nonpoint source water quality problems caused by soil erosion, best management practices (BMPs) and/or conservation programs have been adopted. Watershed models, such as the Annualized Agricultural Non-Point Source Pollutant Loading model (AnnAGNPS), have been developed to aid in the evaluation of watershed response to watershed management practices. The model has been applied worldwide and proven to be a very effective tool in identifying the critical areas which had serious erosion, and in aiding in decision-making processes for adopting BMPs and/or conservation programs so that cost/benefit can be maximized and non-point source pollution control can be achieved in the most efficient way. The main goal of this study was to assess the characteristics of soil erosion, sediment and sediment delivery of a watershed so that effective conservation measures can be implemented. To achieve the overall objective of this study, all necessary data for the 4,184 km2 Daning River watershed in the Three-Gorge region of the Yangtze River of China were assembled. The model was calibrated using observed monthly runoff from 1998 to 1999 (Nash-Sutcliffe coefficient of efficiency of 0.94 and R2 of 0.94) and validated using the observed monthly runoff from 2003 to 2005 (Nash-Sutcliffe coefficient of efficiency of 0.93 and R2 of 0.93). Additionally, the model was validated using annual average sediment of 2000–2002 (relative error of −0.34) and 2003–2004 (relative error of 0.18) at Wuxi station. Post validation simulation showed that approximately 48% of the watershed was under the soil loss tolerance released by the Ministry of Water Resources of China (500 t·km−2·y−1). However, 8% of the watershed had soil erosion of exceeding 5,000 t·km−2·y−1. Sloping areas and low coverage areas are the main source of soil loss in the watershed.

Temporal and Spatial Simulation of Adsorbed Nitrogen and Phosphorus Nonpoint Source Pollution Load in Xiaojiang Watershed of Three Gorges Reservoir Area, China

The presence of nonpoint source (NPS) pollution due to agricultural activities at the Three Gorges Reservoir Area in China has been of concern to the public in recent years. Due to the extent of the polluted area and seasonal dispersion mode, sediments have greatly impacted the water quality in the area. Generation and formation of adsorbed NPS pollution involves great uncertainty, which makes monitoring and controlling pollution very difficult. Rainfall erosivity factors, which are calculated by surface rainfall data from watershed hydrological simulation, and sediment delivery ratios were both selected and determined as the dynamic factors, whereas blind number theory was introduced and used to describe and deal with the factors' uncertainty of the Revised Universal Soil Loss Equation (RUSLE). Through the integration among blind number theory, dynamic factors, and pollution load model, parameter uncertainty and model dynamics could be better understood in the new and comprehensive pollution load model using GIS technology. Results indicated that rainfall runoff and sediment delivery ratio had significantly affected the uncertainty of final adsorbed NPS pollution load simulation results; the magnitude of adsorbed nitrogen and phosphorus loads from different land use types in descending order in turn was glebe, grassland, paddy fields, forestland, and urban land. This work provides a theoretical basis for control and management of soil loss and NPS pollution in the Three Gorges Reservoir Area, and these data are also useful in evaluating potential soil loss and NPS pollution loads in the watershed.

BASINS/HSPF: Model Use, Calibration, and Validation

This article presents recommendations by model developers and the authors about calibration and validation procedures for the Hydrological Simulation Program - Fortran (HSPF) as applied through BASINS. HSPF is a continuous simulation watershed model that simulates nonpoint-source runoff and pollutant loadings for a watershed and performs flow and water quality routing in stream reaches and well-mixed lakes and impoundments. HSPF can be used to estimate nonpoint-source loads from various land uses as well as fate and transport processes in streams and lakes. This article describes the ideal calibration and validation process for the full range of constituents modeled by HSPF, as well as the process for acceptable minimum calibration and validation of this model. The model information and guidance provided in this article may be used to help in determining the scope of the proposed ASABE Standard/Engineering Practice for model calibration and validation. Model calibration and validation are necessary and critical steps in any model application. For HSPF and most other watershed models, calibration is an iterative procedure of parameter evaluation and refinement, as a result of comparing simulated and observed values of interest. Model validation is in reality an extension of the calibration process. Its purpose is to ensure that the calibrated model properly assesses all the variables and conditions that can affect model results, and to demonstrate the ability to predict field observations for periods separate from the calibration effort. For HSPF calibration and validation, a “weight of evidence” approach is most widely used in practice when models are examined and judged for acceptance for assessment and regulatory purposes. This article explores the “weight of evidence” approach and the current practice of watershed model calibration and validation based on more than 30 years of experience with HSPF. Example applications are described and model results are shown to demonstrate the graphical and statistical procedures used to assess model performance. In addition, quantitative criteria for various statistical measures are discussed as a basis for evaluating model results and documenting the model application efforts.

Modeling of land use and reservoir effects on nonpoint source pollution in a highly agricultural basin

Nonpoint source (NPS) pollution is tightly linked to land use activities that determine the sources and magnitudes of pollutant loadings to stream water. The pollutant loads may also be alleviated within reservoirs because of the physical interception resulting from changed hydrological regimes and other biochemical processes. It is important but challenging to assess the NPS pollution processes with human effects due to the measurement limitations. The objective of this study is to evaluate the effects of human activities such as land uses and reservoir operation on the hydrological and NPS pollution processes in a highly agricultural area-the Iowa River Basin-using the Soil and Water Assessment Tool (SWAT). The evaluation of model performance at multiple sites reveals that SWAT can consistently simulate the daily streamflow, and monthly/annual sediment and nutrient loads (nitrate nitrogen and mineral phosphorus) in the basin. We also used the calibrated model to estimate the trap efficiencies of sediment (∼78%) and nutrients (∼30%) in the Coralville Reservoir within the basin. These non-negligible effects emphasize the significance of incorporating the sediment and nutrient removal mechanisms into watershed system studies. The spatial quantification of the critical NPS pollution loads can help identify hot-spot areas that are likely locations for the best management practices.

Water quality model establishment for middle and lower reaches of Hanshui River, China

With the development of industry and agriculture, nitrogen, phosphorus and other nutrients in the Hanshui River greatly increase and eutrophication has become an important threat to the water quality of the Hanshui River, especially in the middle and lower reaches. The primary objective of this study was to establish the water quality model for the middle and lower reaches of the Hanshui River based on the model of MIKE 11. The main pollutants migration and transformation process could be simulated using the water quality model. The rainfall-runoff model, hydrodynamic model and water quality model were established using MIKE 11. The pollutants, such as chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen, nitrate nitrogen, phosphorus, dissolved oxygen (DO), were simulated and predicted using the above three models. A set of methods computing non-point source pollution load of the Hanshui River Basin was proposed in this study. The simulated and observed values of COD, BOD5, ammonia, nitrate, DO, and total phosphorus were compared after the parameter calibration of the water quality model. The simulated and observed results match better, thus the model can be used to predict water quality in the future for the Hanshui River. The pollution trend could be predicted using the water quality model according pollution load generation. It is helpful for government to take effective measures to prevent the water bloom and protect water quality in the river.

Land use pattern optimization based on CLUE-S and SWAT models for agricultural non-point source pollution control

Improper land use is one major cause of non-point source pollution. Integrated modeling would support the evaluation and optimization of land use for the non-point source pollution control. In this study, the CLUE-S (the Conversion of Land Use and its Effect at Small regional extent) and SWAT (Soil and Water Assessment Tool) models were coupled to simulate pollution loads under different land use scenarios in the upstream watershed of Miyun Reservoir in Beijing, China. The results indicated that changes in land use structure and pattern under different land use scenarios have significantly affected the non-point source pollution load. The increase of orchards and loss of forest cover has led to an increase in the potential pollution loads of nitrogen by 5.27% and phosphorus by 4.03%. However, in the agricultural non-point source pollution control scenario, pollution loads of nitrogen decreased by 13.94% and phosphorus by 9.86%, resulting from the establishment of riparian vegetation buffers and restoring forest on unutilized land and slope arable land. Coupling the hydrological model SWAT and the land use model CLUE-S succeeded in evaluating the land use pattern for agricultural non-point source pollution control. The coupling of two models provides a new approach for land use optimization towards non-point source pollution control.

Response of non-point source pollutant loads to climate change in the Shitoukoumen reservoir catchment

The impacts of climate change on streamflow and non-point source pollutant loads in the Shitoukoumen reservoir catchment are predicted by combining a general circulation model (HadCM3) with the Soil and Water Assessment Tool (SWAT) hydrological model. A statistical downscaling model was used to generate future local scenarios of meteorological variables such as temperature and precipitation. Then, the downscaled meteorological variables were used as input to the SWAT hydrological model calibrated and validated with observations, and the corresponding changes of future streamflow and non-point source pollutant loads in Shitoukoumen reservoir catchment were simulated and analyzed. Results show that daily temperature increases in three future periods (2010-2039, 2040-2069, and 2070-2099) relative to a baseline of 1961-1990, and the rate of increase is 0.63°C per decade. Annual precipitation also shows an apparent increase of 11mm per decade. The calibration and validation results showed that the SWAT model was able to simulate well the streamflow and non-point source pollutant loads, with a coefficient of determination of 0.7 and a Nash-Sutcliffe efficiency of about 0.7 for both the calibration and validation periods. The future climate change has a significant impact on streamflow and non-point source pollutant loads. The annual streamflow shows a fluctuating upward trend from 2010 to 2099, with an increase rate of 1.1m(3)s(-1) per decade, and a significant upward trend in summer, with an increase rate of 1.32m(3)s(-1) per decade. The increase in summer contributes the most to the increase of annual load compared with other seasons. The annual NH (4) (+) -N load into Shitoukoumen reservoir shows a significant downward trend with a decrease rate of 40.6t per decade. The annual TP load shows an insignificant increasing trend, and its change rate is 3.77t per decade. The results of this analysis provide a scientific basis for effective support of decision makers and strategies of adaptation to climate change.

Evaluation of non-point source pollution and river water quality using a multimedia two-model system

Summary In this study, an integrated two-model system composed of a multimedia watershed model and a river water quality model was developed to effectively simulate the impacts of non-point source (NPS) pollution on river water quality. NPS pollution loadings from Kaoping River Basin were calculated using the Integrated Watershed Management Model (IWMM). Results from the IWMM modeling were used as the input data for the Kaoping River water quality evaluation using the Water Quality Analysis Simulation Program (WASP) modeling. The land use patterns classified using SPOT images and Digital Elevation Model techniques with the aid of Erdas Imagine® process and ArcView® geographical information system were applied to assist the NPS pollution simulation. Results indicate that land use patterns of orchard farms and farmland areas were the major causes of the NPS pollution, and they should be effectively controlled. Results show that higher flow rates (>200 m 3 /s) were observed in the wet seasons, which would cause the increase in NPS pollution loadings. Results demonstrate that the integral approach could develop a direct linkage between upstream land use changes and downstream water quality. Using water quality modeling alone would underestimate the impact of NPS pollution on river water quality. The introduction of the integrated two-model system shows a significant advance in estimating the water quality.

강우강도와 토지이용을 고려한 비점오염물질 부하량 산정에 관한 연구

The unit load has simply been used to estimate total pollutant loading from non-point sources, however, it does not count on the variable pollutant loading according to land use characteristics and rainfall intensity. Since pollutant emission from the watershed is strongly dependent on the rainfall intensity, it is necessary to find out the relationship between pollutant loading and rainfall intensity. The objective of this study is to develop simple and easy method to compute non-point source pollution loads with consideration of rainfall intensity. Two non-point source removal facility at Gyeongan-dong (Gwangju-si) and Mohyeon-myeon (Yongin-si), Gyeonggi-do was selected to monitor total rainfall, rainfall intensity, runoff characteristics and water quality from June to November, 2010. Most of Event Mean Concentrations (EMC) of measured water quality data were higher in Gyeongan which has urban land use than in Mohyeon which has rural land use. For the case of TP (Total Phosphorus), Mohyeon has higher values by the influence of larger chemical uses such as fertilizer. The relationship between non-point source pollution load and rainfall intensity is perfectly well explained by cubic regression with 0.33~0.81 coefficients of determination(). It is expected that the pollution loading function based on the long-term monitoring would be very useful with good accuracy in computing non-point source pollution load, where a rainfall intensity is highly variable.

격자기반의 지형 및 지리정보자료와 GIS분석기법을 이용한 유역의 유출량 및 오염부하량 추정

Pollutant loads calculated with unit factor method can not identity seasonal variations of pollutant inputs. Estimation of pollutant loads considering rainfall runoff can overcome these limits. SCS curve number method was applied to estimate runoff of each event of Koeup watershed of Koheung estuary lake. SCS curve numbers were calculated based upon land use, soil types of the catchment using GIS. Point and nonpoint source pollutant loads were summed up for total loads estimation. Those from nonpoint source were estimated by multiplying the calculated runoff and expected mean concentrations (EMC) presented by the Minister of Environment of Korea. DEM can present three dimensional views of a terrain, identity stream networks and flow accumulation. Furthermore, it can examine accumulated pollutant loads of specific point of a catchment. Therefore, cell based pollutant load estimation was attempted using DEM. ArcView was utilized to collect, store and manipulate spatial and attribute data of pollutant sources and features of the catchment. Cell-based DEM which was established by the GRID module of ARC/INFO was employed to estimate flows and pollutant loads.