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Unit load factor, which is used for the quantification of non-point pollution in watersheds, has the limitation that it does not reflect spatial characteristics of soil, topography and temporal change due to the interannual or seasonal... more
Unit load factor, which is used for the quantification of non-point pollution in watersheds, has the limitation that it does not reflect spatial characteristics of soil, topography and temporal change due to the interannual or seasonal variability of precipitation. Therefore, we developed the method to estimate a watershed-scale non-point pollutant load using seasonal forecast data that forecast changes of precipitation up to 6 months from present time for watershed-scale water quality management. To establish a preemptive countermeasure against non-point pollution sources, it is possible to consider the unstructured management plan which is possible over several months timescale. Notably, it is possible to apply various management methods such as control of sowing and irrigation timing, control of irrigation through water management, and control of fertilizer through fertilization management. In this study, APEX-Paddy model, which can consider the farming method in field scale, was applied to evaluate the applicability of seasonal forecast data. It was confirmed that the rainfall amount during the growing season is an essential factor in the non-point pollution pollutant load. The APEX-Paddy model for quantifying non-point pollution according to various farming methods in paddy fields simulated similarly the annual variation tendency of TN and TP pollutant loads in rice paddies but showed a tendency to underestimate load quantitatively.
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기후변화에 따른 농업수자원 여건 변화와 가뭄 등의 재해 빈도의 증가는 농산물 생산성에 직접적인 영향을 줄 수 있다. 안정적인 농업생산량 유지를 위해서 기후변화를 고려한 미래 농업수자원 및 가뭄취약성 분석을 통해 지속가능한 농업용수 공급 대책을 마련할 필요가 있다. 용수공급원의 물 부족 대응 정도를 파악하고, 농업용수 이수 취약 예상 지역을 예측하여 미래시기 용수공급계획 및 물 관리시설 확충계획을 사전에 마련해야한다. 이에... more
기후변화에 따른 농업수자원 여건 변화와 가뭄 등의 재해 빈도의 증가는 농산물 생산성에 직접적인 영향을 줄 수 있다. 안정적인 농업생산량 유지를 위해서 기후변화를 고려한 미래 농업수자원 및 가뭄취약성 분석을 통해 지속가능한 농업용수 공급 대책을 마련할 필요가 있다. 용수공급원의 물 부족 대응 정도를 파악하고, 농업용수 이수 취약 예상 지역을 예측하여 미래시기 용수공급계획 및 물 관리시설 확충계획을 사전에 마련해야한다. 이에 이 연구에서는 기후 변화에 따른 단기 및 중장기 미래 가뭄 심도 분석 결과와 농어촌용수구역별 통계특성을 이용하여 용수구역 유형화 결과를 바탕으로 미래 농업용수이용 취약지구를 선정 및 제시하고자 하였다. 이를 위하여 먼저 기상청에서 제공하는 RCP (Representative Concentration Pathways) 4.5 및 8.5 시나리오의 기후변화자료를 바탕으로 FAO Penman-Monteith 기반으로 한 표준강수증발산지수 (SPEI, Standardized Precipitation Evapotranspiration Index) 산정하여, 가뭄심도 및 기간 등을 분석하였다. 또한 농어촌용수구역의 유형분류는 농어촌용수이용화합리화 계획 자료를 바탕으로 논용수 수요량 대비 공급량 비율과 밭용수 수요량대비 공급량 비율, 지하수 개발가능량 대비 이용량 비율 등을 추정하여 용수구역 분류 실시하였다. 위 두 결과를 바탕으로 기후변화 및 지하수 기반 가뭄대비가 필요한 가뭄취약지구를 선정하기 위한 우선순위 기준을 설정하고, 이를 바탕으로 취약용수구역을 제시하였다. 최종적으로 취약용수구역 중 지표수 수리시설로 용수공급 불리 지역에 대한 우선순위를 리단위로 제시하였다. 이 연구결과는 극한 기상 변화에 의한 농업용수 수급 취약지역을 예상하고, 미래 기후변화 전망에 따른 물 부족 대응 및 지표수-지하수 연계를 통한 안정적 농업용수 공급 정책 결정 등의 기반 마련에 기여할 수 있을 것으로 판단된다.
The purpose of this study is to analyze the effects of climate change on the nonpoint source pollution in a small watershed using a mid-range model. The study area is a basin in a rural area that covers 384 ha with a composition of 50%... more
The purpose of this study is to analyze the effects of climate change on the nonpoint source pollution in a small watershed using a mid-range model. The study area is a basin in a rural area that covers 384 ha with a composition of 50% forest and 19% paddy. The hydrologic and water quality data were monitored from 1996 to 2004, and the feasibility of the GWLF (Generalized Watershed Loading function) model was examined in the agricultural small watershed using the data obtained from the study area. As one of the studies on climate change, KEI (Korea Environment Institute) has presented the monthly variation ratio of rainfall in Korea based on the climate change scenario for rainfall and temperature. These values and observed daily rainfall data of forty-one years from 1964 to 2004 in Suwon were used to generate daily weather data using the stochastic weather generator model (WGEN). Stream runoff was calibrated by the data of and was verified in . The results were determination coeff,...
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This study aims to assess the spatiotemporal characteristics of meteorological droughts in 21 Bangladesh during 1981–2015 using the Effective Drought Index (EDI). Monthly precipitation data 22 for 36 years (1980-2015) obtained from 27... more
This study aims to assess the spatiotemporal characteristics of meteorological droughts in 21 Bangladesh during 1981–2015 using the Effective Drought Index (EDI). Monthly precipitation data 22 for 36 years (1980-2015) obtained from 27 metrological stations, were used in this study. The EDI 23 performance was evaluated for four sub-regions over the country through comparisons with 24 historical drought records identified at the regional scale. Analysis at a regional level showed that 25 EDI could reasonably detect the drought years/events during the study period. The study also 26 revealed that the overall drought severity had increased during the past 35 y; the most significant 27 increasing trend was observed in the central region. The characteristics (severity and duration) of 28 drought were also analysed in terms of spatiotemporal evolution of the frequency of drought events. 29 It was found that the western and central regions of the country are comparatively more vulnerable 30...
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Existing agro-hydrological models to explore the effects of paddy management practices on hydrology and water quality suffer from multiple shortcomings because they were developed using upland characteristics. The Agricultural... more
Existing agro-hydrological models to explore the effects of paddy management practices on hydrology and water quality suffer from multiple shortcomings because they were developed using upland characteristics. The Agricultural Policy/Environmental eXtender (APEX)-Paddy model was recently developed to improve the agro-hydrological characteristics of paddy ecosystems. This study explores the hydrology, total nitrogen (T-N) content, and rice yield behaviors of the APEX-Paddy model by simultaneously considering multiple parameters associated with different agricultural activities. Model performances with respect to runoff, T-N, and rice yield were assessed as good level of approved statistical criteria over the calibration and validation periods. Results showed that the APEX-Paddy model can simulate the behavior differences of soil nutrients between different agricultural activities, such as treatment with commercial mineral fertilizer or liquid manure application. Changes in mineral-nitrogen levels in root zones caused by fertilizers can affect T-N load and crop uptake. A high degree of correlation was observed between the amount of nutrients remaining after crop uptake and sediment-transported nitrogen. These findings suggest that the crop-growth parameters of the model can significantly affect biomass, evapotranspiration rate, and T-N load on farmland. The results may help decision makers evaluate water-saving and pollutant-reduction options in paddy fields under future climate scenarios and conservation strategies.
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Climate change is currently one of the most critical issues in watershed management, and typical paddy systems should be addressed by watershed modeling approach in paddy-dominant landscapes. This study is designed to evaluate and enhance... more
Climate change is currently one of the most critical issues in watershed management, and typical paddy systems should be addressed by watershed modeling approach in paddy-dominant landscapes. This study is designed to evaluate and enhance the watershed modeling approach currently used to characterize the impacts of climate change on hydrologic and water quality responses while considering a paddy environment. APEX-paddy, which is a newly developed and modified APEX (Agricultural Policy/Environmental eXtender) model for paddy ecosystems, was coupled with SWAT (Soil and Water Assessment Tool) model to take advantage of the strengths of the two models. The resulting hybrid model, SWAPX, was calibrated and validated using observed data from 2008 to 2017 for two sites in the study watershed. Compared to SWAT, the accuracy of SWAPX was improved, showing statistically better results in the downstream including more paddy field areas. Ten GCMs were selected, and the characteristics of these GCMs were evaluated to assess the impacts of climate change scenarios. When applying the climate change scenarios to the SWAPX model, the results indicated that the future streamflow would increase due to increased rainfall. The results also showed that total nitrogen (T-N) loads would increase rapidly in the near future, then decrease gradually through the 2090s (2091–2100). T-N load was affected by the characteristics of rainfall patterns (e.g., daily maximum rainfall and rainfall intensity) occurring in various GCMs. This approach will be helpful for decision-makers in adapting to climate change and evaluating Best management practices (BMP) for paddy-dominant watersheds.
The relative performance of global climate models (GCMs) of phases 5 and 6 of the coupled model intercomparison project (CMIP5 and CMIP6, respectively) was assessed in this study based on their ability to simulate annual and seasonal mean... more
The relative performance of global climate models (GCMs) of phases 5 and 6 of the coupled model intercomparison project (CMIP5 and CMIP6, respectively) was assessed in this study based on their ability to simulate annual and seasonal mean rainfall and temperature over Bangladesh for the period 1977–2005. Multiple statistical metrics were used to measure the performance of the GCMs at 30 meteorological observation stations. Two robust multi-criteria decision analysis methods were used to integrate the results obtained using different metrics for an unbiased ranking of the GCMs. The results revealed MIROC5 as the most skillful among CMIP5 GCMs and ACCESS-CM2 among CMIP6 GCMs. Overall, CMIP6 MME showed a significant improvement in simulating rainfall and temperature over Bangladesh compared to CMIP5 MME. The highest improvements were found in simulating cold season (winter and post-monsoon) rainfall and temperature in higher elevated areas. The improvement was relatively more for rainfall than for temperature. The models could capture the interannual variability of annual and seasonal rainfall and temperature reliably, except for the winter rainfall. However, systematic wet and cold/warm biases still exist in CMIP6 models for Bangladesh. CMIP6 GCMs showed higher spatial correlations with observed data, but the higher difference in standard deviations and centered root mean square errors compared to CMIP5 GCMs indicates better performance in simulating geographical distribution but lower performance in simulating spatial variability of most of the climate variables except for minimum temperature at different timescales. In terms of Taylor skill score, the CMIP6 MME showed higher performance in simulating rainfall but lower performance in simulating temperature than CMIP5 MME for most of the timeframes. The findings of this study suggest that the added value of rainfall and temperature simulations in CMIP6 models is not consistent among the climate models used in this research. However, it sets a precedent for future research on climate change risk assessment for the scientific community.
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Projecting water availability under various possible future climate scenarios depends on the choice of Global Climate Model (GCM), evapotranspiration (ET) estimation method and Representative Concentration Pathway (RCP) trajectory. The... more
Projecting water availability under various possible future climate scenarios depends on the choice of Global Climate Model (GCM), evapotranspiration (ET) estimation method and Representative Concentration Pathway (RCP) trajectory. The relative contribution of each of these factors must be evaluated in order to choose an appropriate ensemble of future scenarios for water resources planning. In this study variance-based global sensitivity analysis and Monte Carlo filtering were used to evaluate the relative sensitivity of projected changes in precipitation (P), ET and water availability (defined here as…
Rainfall and temperature variability at multiple time and space scales profoundly affect both water demand fluctuations and supply availability. In support of effective water resource management and efficient groundwater/surface water... more
Rainfall and temperature variability at multiple time and space scales profoundly affect both water demand fluctuations and supply availability. In support of effective water resource management and efficient groundwater/surface water source rotation that enhances system reliability, Tampa Bay Water is seeking to develop more robust climate forecasts and simulation techniques. In 2007, Tampa Bay Water initiated a project with University of Florida to assess the usefulness of various climate indices, climate forecasts and climate model predictions as input into the agency’s hydrologic models.
Agricultural reservoirs play such a central role in supplying water to rural areas that it is essential to properly estimate the design flood for agricultural reservoirs under climate change. The objective of this study was to estimate... more
Agricultural reservoirs play such a central role in supplying water to rural areas that it is essential to properly estimate the design flood for agricultural reservoirs under climate change. The objective of this study was to estimate the inflow design flood interval using a non-parametric resampling technique for agricultural reservoirs under climate change. This study suggested an alternative method to point estimation using insufficient past data by providing the interval of the inflow design flood under the representative concentration pathway. To estimate the interval of the inflow design flood, we employed the bootstrap technique, which estimated the confidence interval corresponding to the 95% confidence level. This study covered a spatial range of 30 agricultural reservoirs in South Korea and a temporal range of past and three future representative periods: the base period (2015s: 1986–2015) and future periods (2040s: 2011–2040, 2070s: 2041–2070, 2100s: 2071–2100). We analy...
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The authors wish to make the following corrections to this paper [...]
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This research aims to assess the impact of climate change on water balance components in irrigated paddy cultivation. The APEX-Paddy model, which is the modified version of the APEX (Agricultural Policy/Environmental eXtender) model for... more
This research aims to assess the impact of climate change on water balance components in irrigated paddy cultivation. The APEX-Paddy model, which is the modified version of the APEX (Agricultural Policy/Environmental eXtender) model for paddy ecosystems, was used to evaluate the paddy water balance components considering future climate scenarios. The bias-corrected future projections of climate data from 29 GCMs (General Circulation Models) were applied to the APEX-Paddy model simulation. The study area (Jeonju station) forecasts generally show increasing patterns in rainfall, maximum temperature, and minimum temperature with a rate of up to 23%, 27%, and 45%, respectively. The hydrological simulations suggest over-proportional runoff–rainfall and under-proportional percolation and deep-percolation–rainfall relationships for the modeled climate scenarios. Climate change scenarios showed that the evapotranspiration amount was estimated to decrease compared to the baseline period (197...