Min Hwan Shin

Application of Surface Cover Materials and Soil Amendments for Reduction of Non-Point Source Pollution from Upland Fields

The objective of the study was to investigate the effect of rice straw mat, rice straw mat with PAM (Polyacrylamide) and gypsum addition on surface runoff and sediment discharge in field. Six experimental plots of in size and 3 % in slope prepared on gravelly sandy loam soil were treated with control, rice straw mat cover with gypsum and rice straw mat cover with gypsum and PAM. Radish in Spring and Chinese cabbage in autumn growing seasons were cultivated. Non point source (NPS) pollution discharge was monitored and compared among the treatments. Rainfall of the 10 monitored events ranged from 17.0 mm to 93.5 mm. Runoff coefficient of the events was 0.005~0.239 in control plot, 0~0.176 in rice straw plot with gypsum and 0~0.046 in rice straw mat plot with gypsum and PAM. When compared to the control plot, the runoff amount was reduced by 10.4~100 % (Ave. 60.8) in rice straw plot with gypsum and 80.7~100 % (Ave. 96.7 %) in rice straw mat plot with gypsum and PAM. The reduction of NPS pollution load was 54.6 % for BOD5, 71.5 % for SS, 41.6 % for TN and 61.4 % for T-P in rice straw with gypsum plot and 91.9 % for BOD5, 92.0 % for SS, 88.0 % for TN and 88.5 % for T-P in rice straw mat with gypsum and PAM plot. This research revealed that rice straw mat cover with soil amendments on the soil surface could not only increase the crop yield but also reduce the NPS pollution loads substantially.

Application of the Surface Cover Materials for Reduction of NPS Pollution from Actual Cultivation

Four actual cultivations were prepared and a variety of soybean was cultivated. A H-flume, an automatic water level gauge and an automatic water sampler were installed at the outlet of each plot equipped for the measurement of flow rate and its water quality. The amount of rainfall of the study area in 2013 was measured as 975.6 mm which was much lower than the annual average rainfall of 1,271.8 mm, resulting in less occurrences in rainfall-runoff events. Rainfall-runoff events were occurred three times during the rainfall event of 4~5 July, 23 and 24 August. The characteristics of NPS pollution discharge of the plots and the reduction effect of the selected BMPs were analyzed during these events. The reduction effect of straw mat and soil amendments (Polyacrylamide (PAM) and Gypsum) on runoff ratio ranged between 38.2 and 92.9% (average 71.6%). The NPS pollution load reduced between 27.7 and 95.1% (average 70.0%) by the application of rice straw mat and soil conditioner when compared with that of control plot. Soybean yield (2,133.3 kg/ha) of the straw mat covered plots increased by 14.3% when compared with control (1,866.7 kg/ha). The effect of straw mat on the yield was not economically viable if the material and accompanying labor costs were considered. The data collected and analyzed on different soil textures and crops in this study are expected to be a fundamental reference for the expansion of the results to the application nationwide and the development of NPS pollution management policies.

Analysis of Rainfall-Runoff Characteristics on Bias Correction Method of Climate Change Scenarios

Abstract Runoff behaviors by five bias correction methods were analyzed, which were Change Factor methods using past observed and estimated data by the estimation scenario with average annual calibration factor (CF_Y) or with average monthly calibration factor (CF_M), Quantile Mapping methods using past observed and estimated data considering cumulative distribution function for entire estimated data period (QM_E) or for dry and rainy season (QM_P), and Integrated method of CF_M+QM_E(CQ). The peak flow by CF_M and QM_P were twice as large as the measured peak flow, it was concluded that QM_P method has large uncertainty in monthly runoff estimation since the maximum precipitation by QM_P provided much difference to the other methods. The CQ method provided the precipitation amount, distribution, and frequency of the smallest differences to the observed data, compared to the other four methods. And the CQ method provided the rainfall-runoff behavior corresponding to the carbon dioxide emission scenario of SRES A1B. Climate change scenario with bias correction still contained uncertainty in accurate climate data generation. Therefore it is required to consider the trend of observed precipitation and the characteristics of bias correction methods so that the generated precipitation can be used properly in wa ter resource management plan establishment.

Effect of Balloonflower and Potato Cultivation on Runoff and NPS Pollution Loads

An upland monitoring was conducted for about 4 years with respect to the water and quality of rainfall-runoff. The objective was to characterize of runoff and nonpoint source (NPS) pollution from a sandy field with 4.5 % in slope under balloonflower (2008-2010) and potato (2011) cultivation. Balloonflower was cultivated without any surface cover but potato was grown under plastic mulching. Runoff rate, EMCs and NPS pollution loads were estimated. The first flush effect was evaluated, and the correlation coefficient among the selected water quality indices were analyzed. Average rainfall size was higher by 2.3 mm when balloonflower was cultivated but average runoff rate was higher by 0.02 when potato was cultivated due to the plastic mulching. EMCs monitored from balloonflower field were higher than potato field except SS and TN, but all NPS pollution loads of potato field were 2.1~22.9 times greater than balloonflower field because of larger runoff volume. As a result of first flush effects, balloonflower and potato field were more influenced by increasing of accumulated rainfall and rainfall intensity rather than first flush. In the result of correlation analysis, there were no evident correlations between runoff and water quality indices. However, there were obvious correlations between SS and the other indices except TN. As a result of this study, it was thought that perennial balloonflower crop could help reduce runoff and NPS pollution loads but annual crop with plastic mulching increase them.

Comparison of Annual Soil Loss using USLE and Hourly Soil Erosion Evaluation System

Soil erosion and sediment has been known as one of pollutants causing water quality degradation in water bodies. With global warming issues worldwide, various soil erosion studies have been performed. Although on-site monitoring of sediment loss would be an ideal method to evaluate soil erosion condition, modeling approaches have been utilized to estimate soil erosion and to evaluate various best management practices on soil erosion reduction. Although the USLE has been used in soil erosion estimation for the last 40 years, the USLE model has limitations in estimating event-based soil erosion reflecting rainfall intensity and rainfall duration for long-term period. Thus, the calibrated model, capable of simulating soil erosion using hourly rainfall data, was utilized in this study to evaluate the effects of rainfall amount and rainfall intensity on soil erosion. It was found that USLE soil erosion value is 3.06 ton ha -1 yr -1 , while soil erosion values from 2006 ~ 2010 were 2.469 ton ha -1 yr -1 , 0.882 ton ha -1 yr -1 , 1.489 ton ha -1 yr -1 , 2.158 ton ha -1 yr -1 , 1.602 ton ha -1 yr -1 , respectively. Especially, soil erosion from single storm event for 2008-2010 would be responsible for 30% or more of annual soil loss. As shown in this study, hourly soil erosion estimation system would provide more detailed output from the study area. In addition, the effects of rainfall intensity on soil erosion could be evaluated with this system.

Quantification of NPS Pollution to Meet the TMDL in Korea

Concept of TMDL system of Korea is briefly introduced. Objectives and target pollutant in the first and second stage TMDL, classification of pollution source groups, and concept of unit load were explained. Advantages and disadvantages of current unit load were compared and a new normalized method to estimate the unit load was suggested. Government land cover classification method was introduced to explain the efforts to expand unit load for more detailed land uses than current ones. Characteristics and current status of NPS monitoring studies in Korea also were briefly explained. And future challenges in the quantification of NPS pollution load were described where a proposal for the change of unit load system to BMPs based method for agricultural area in the computation of pollution load was made.

A Study to Develop Monthly Cover Management Factor Database for Monthly Soil Loss Estimation

Soil loss is an accompanying phenomenon of hydrologic cycle in watersheds. Both rainfall drops and runoff lead to soil particle detachment, the detached soil particles are transported into streams by runoff. Here, a sediment-laden water problem can be issued if soil particles are severely detached and transported into stream in the watershed. There is a need to estimate or simulate soil erosion in watersheds so that an adequate plan to manage soil erosion can be established. Universal Soil Loss Equation (USLE), therefore, was developed and modified by many researchers for their watersheds, moreover the simple model, USLE, has been employed in many hydrologic models for soil erosion simulations. While the USLE has been applied even in South-Korea, the model is often regarded as being limited in applications for the watersheds in South-Korea since monthly conditions against soil erosion on soil surface are not capable to represent. Thus, the monthly USLE factors against soil erosion, soil erodibility and crop management factors, were established for four major watersheds, which are Daecheong-dam, Soyang-dam, Juam-dam, and Imha-dam watersheds. The monthly factors were established by recent fifteen years from 2000 to 2015. Five crops were selected for the monthly crop management factor establishments. Soil loss estimations with the modified factors were compared to conventional approach that is average annual estimations. The differences ranged from 9.3 % (Juam-dam watershed) to 28.1 % (Daecheong-dam watershed), since the conventional approaches were not capable of seasonally and regionally different conditions.

Simulation of the GHG Emissions Impact on Climate Change from Radish Field

This study was conducted to predict greenhouse gas (GHG) emission from a radish field by future climate change scenario. A radish field located at Chuncheon-si Gangwon-do was selected, and A1B Special Report on Emission Scenario (SRES) of the IPCC (Intergovernmental panel on climate change) was applied to simulate the future potential climate change. Rainfall and temperature data were predicted to be increased by 8.4 % and 1.9 % in 2040s, 35.9 % and 27.0 % in 2060s, 19.2 % and 30.8 % in 2090s, respectively, compared to the climate data in 2010s. The N2O, CO2, and CH4 emission were estimated to be increased by 0.4 up to 2.4 kg/ha/yr, by 500.5 up to 734.5 kg/ha/year, and by 29.4 up to 160.4 kg/ha/yr, which were resulted from the global warming potential (GWP) of 14.5~21.7 CO2/ha/year caused by the amount changes of rainfall, temperature, manure amendment, and fertilizer applied in fields. One distinct feature of the study result was that the changes of N2O-N, CH4-C and CO2-C with future potential climate change simulation were varied by soil texture. Therefore it was concluded that there is a need to apply appropriate amount of manure amendment needs and to consider soil texture as well.

Evaluation of Regression Models in LOADEST to Estimate Suspended Solid Load in Hangang Waterbody

Abstract Typically, water quality sampling takes place intermittently si nce sample collection and following analysis requires substantia l cost and efforts. Therefor eregression models (or rating curves) are often used to interpolate water quality data. LOADEST has nine regression models to es timate water quality data ,and one regression model needs to be selected automatically or manually. The nine regression models in LOADEST and auto-selection by LOADEST were evaluated in the study. Suspended solids data were collected from forty-nine stations from the Water Information System of the Ministry of Environment. Suspended solid data from each station was divided into two groups for calibration and validation. Nash-Stucliffe efficiency (NSE) and coefficient of determination (R 2 ) were used to evaluate estimated suspended solid loads. The regression models numbered 1 and 3 in LOADEST provide dhigher NSE and R 2 , compared to the other regression models. The regression modes numbered 2, 5, 6, 8, and 9 in LOADEST provided low NSE. In addition, the regression model selected by LOADEST did not necessarily provide better suspended solid estimations than the othe r regression models did.Keywords: Load estimation; LOADEST; Regression model; Suspended solid*

Effect of NPS Loadings from Livestock on Small Watersheds

Abstract The objective of this paper was to quantit atively analyze the effect of concentrated animal feeding operations (CAFO) NPS pollu tion on a small watershe dwater quality. Monitoring was conducted from March to October, 2013. Monthly flow rate and selected water quality at each monitoring site were measured during dry days. Rainy day monitori ng also was conducted. Modeli ng was conducted to evaluate the effect of CAFO NPS po llution on the wate rquality at the watershed outlet. The highest and mean concentration of se lected water quality indices during rainy days were hi gher than those in dry daysin general. The highest TN concentration measured at the CAFP pollution discharge point was 237.831 mg/L. The results revealed that the CAFO NPSpollution sources could be equally blamed for the water quality degradation of the stream. However, the effect of the NPS pollut ion from CAFOs seeme dnot to be very influential to the watershed water quality at the outlet. SWAT modeling revealed that the TN load was reduced by 18.95 %, 23.39 % and30.53 % at the watershed outlet if the TN load at the CAFO NPS pollution discharge point reduced by 20 %, 40 % and 60 %, respec tively. It was though tthat the natural attenuation processes play ed an important role. The modeling was based only on the assumption of the load redu ction and not verified bythe monitored data. Therefore, it was suggested that a long term monitoring studies for the evaluation of the impact of CAFO NPS pollution on the watershed water quality be conducted.Keywords:Livestock; NPS Pollution; Pollution Load; SWAT*