• Water for future
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• v.6 no.2
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• pp.6-11
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• 1973

This paper include the hydrometeorological analyses of evapotranspiration which is import factor concerning the estimate of water budgest over a certain basin. Evapotranspiration model mode by the multiple regression analysis between the evapotranspiration measured on various kinds of ground cover (water, bare soil and lawn) and the other meteorological elements affecting the evapotranspiration process, and the simple regression analysis between the evapo transpiration measured on each ground cover and the evapotranspiration on water and vegetables calculated from the Penman equation. It is expected that the evapotranspiration models are a very useful formulae estimating ten days amounts or a month's amounts.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1423-1426
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• 2007

The goal of this research is to develop and apply the integrational model for the pan evaporation and the alfalfa reference evapotranspiration in Republic of Korea. Since the observed data of the alfalfa reference evapotranspiration using lysimeter have not been measured for a long time in Republic of Korea, PM method is used to assume and estimate the observed alfalfa reference evapotranspiration. The integrational model consists of staochastics and neural networks processes respectively. The stochastics process is applied to extend for the short-term monthly pan evaporation and alfalfa reference evapotranspiration. The extended data of the monthly pan evaporation and alfalfa reference evapotranspiration is used to evaluate for the training performance. For the neural networks process, the generalized regression neural networks model(GRNNM) is applied to evaluate for the testing performance using the observed data respectively. From this research, we evaluate the impact of the limited climatical variables on the accuracy of the integrational operation of stochastics and neural networks processes. We should, furthermore, construct the credible data of the pan evaporation and the alfalfa reference evapotranspiration, and suggest the reference data for irrigation and drainage networks system in Republic of Korea.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.178-183
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• 2004

Hydrological models simulate the land phase component of the water cycle and provide a mechanism for evaluating the effects of climatic variation and change on water resources. Evapotranspiration(ET) is a critical process within hydrological models. This study evaluates five different methods for estimating ET in the SLURP(Semi-distrubuted Land Use Runoff Process)model, in the Yongdam basin. The five ET methods were the FAO Penman-Monteith, Motorn CRAE(Complementary Relationship Area Evapotranspiration), the Spittlehouse-Black, the Granger, the Linarce model. We evaluated the five ET models, based on the ability of SLURP model to simulate daily streamflow. and How the five ET methods influence the sensitivity of simulated streamflow to changes in key model parameters and validation SLURP independently for each ET methods.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.146-146
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• 2018

Basin evapotranspiration is the result of water balance and energy balance, which is affected by climate and underlying surface characteristics, the process is complex, and spatial and temporal variability is large, the evapotranspiration estimation of river basin is an important but difficult problem in the field of hydrology, over the years, many scholars devoted to the basin actual evapotranspiration estimation and achieved excellent results. We discuss Budyko coupled water-energy balance theory and evaporation paradox, then use the Fu's equation to estimate actual evapotranspiration yearly in different areas with different dryness. The result shows that Fu's equation has high precision for estimating evapotranspiration yearly in our selected study area, and the estimation result has higher precision in the area with high dryness. Then, we propose an improved formula which can be used to estimate actual evapotranspiration monthly. Furthermore, we found that the parameter in the formula reflects general conditions of underlying surface and it is affected by several factors, at last, we tried to propose the calculation formula. The study indicates that Fu's equation provides a reliable method for evapotranspiration estimation in dry regions as well as semi-humid and semi-arid regions, which has great significance for forecasting river basin water resources and inquiring into ecological water requirement.

• Journal of Wetlands Research
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• v.25 no.1
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• pp.48-63
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• 2023

Research on the method of calculating and estimating evapotranspiration has been steadily conducted. Various models have been developed according to different backgrounds, and each of these models has different characteristics such as required input data. Therefore, this study introduces the theoretical background and characteristics of evapotranspiration models and the development process of domestic research on evapotranspiration by era. First, the origin and theoretical background of the potential evapotranspiration models are summarized in addition to classifying them by input data. Then, the characteristics of the actual evapotranspiration estimation methods are summarized. Additionally, methods based on observation and methods using the rainfall-runoff models are summarized.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.146-146
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• 2019

The aridity index, which is determined as the ratio of potential evapotranspiration to precipitation, is one of key parameters in drought characterization. Whereas the evaporative index, which is defined as the ratio of actual evapotranspiration to precipitation, represents the fraction of available water consumed by the evapotranspiration process. This study investigates variation of the aridity and evaporative indexes due to climate change during the 21st century in South Korea. Estimations of the aridity and evaporative indexes are obtained using SWAT mode based on ensemble of 13 different GCMs over 5 large basins of South Korea for 2 RCP scenarios (RCP 4.5 and RCP 8.5). The results shows the opposite trends of the two indexes, where the aridity index is projected as always increase, while the evaporative index is expected to decrease in all of 3 future period (2011-1940, 1941-1970, 1971-2099). The estimated results also suggest that land cover influenced significantly evapotranspiration along with the change of climate. The study indicates that South Korea will be facing with a high risk of water scarcity in future due to climate change, which is seriously challenging for water planing and management in the country.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.3
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• pp.115-123
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• 2008

Evapotranspiration mapping using both meteorological ground-based measurements and satellite-derived information has been widely studied during the last few decades and various methods have been developed for this purpose. It is significant and necessary to estimate regional evapotranspiration (ET) distribution in the hydrology and water resource research. The study focused on analyzing the surface ET of Chungbuk region using Landsat 7 ETM imagery. For this process, we estimated the regional daily evapotranspiration on May 8, 2000. The estimation of surface evapotranspiration is based on the relationship between Temperature Vegetation Dryness Index (TVDI) and Morton's actual ET. TVDI is the relational expression between Normalized Difference of Vegetation Index (NDVI) and Land Surface Temperature (LST). The distribution of NDVI corresponds well with that of land-use/land cover in Chungbuk. The LST of several part of city in Chungbuk region is higher in comparison with the averaged LST. And TVDI corresponds too well with that of land cover/land use in Chungbuk region. The low evapotranspiration availability is distinguished over the large city like Cheongju-si, Chungju-si and the difference of evapotranspiration availability on forest and paddy is high.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.447-450
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• 2003

It is important to calculate runoff, percolation and evapotranspiration in process hydrological cycle. Especially, a evaportranspiration in watershed has a very important effect on hydrological cycle. In the study, the watershed evapotranspiration was calculated by the water balance and a daily evaportanspiration coefficient(CE) was calculated by the modified Beken's formula.

• Journal of Wetlands Research
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• v.10 no.1
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• pp.21-30
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• 2008

Evapotranspiration is an important factor in the energy interaction process between the surface and the air. Over a vegetable canopy, evapotranspiration was investigated by measuring the sensible heat flux, the soil heat flux and the net radiation flux. Evapotranspiration based on routine AWS data is in good agreement with that estimated from the energy balance equation except for weak wind shear less than $1s^{-1}$ and a cloudy period. Soil heat flux can be approximately to 10% of net radiation flux at the lower layer. When the slope of the saturation vapor pressure versus temperature curve ($de_s/dT$) is approximated to 1.5, the evapotranspiration can be described in function of the net radiation energy flux over Goheung bay wetland covered with the vegetable canopy, reeds.

• Journal of Korea Water Resources Association
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• v.37 no.9
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• pp.745-758
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• 2004

Hydrological models simulate the land phase components of the water cycle and provide a mechanism for evaluating the effects of climatic variation and change on water resources. Evapotranspiration(ET) is a critical process within hydrological models. This study evaluates five different methods for estimating ET in the SLURP(Semi-distributed Land Use Runoff Process)model, in the Yongdam basin. The five ET methods were the FAO Penman-Monteith, Morton CRAE (Complementary Relationship Area Evapotranspiration), the Spittlehouse-Black, the Granger, the Linacre model. We evaluated the five ET models, based on the ability of SLURP model to simulate daily streamflow, and How the five ET methods influence the sensitivity of simulated streamflow to changes in key model parameters and validation SLURP independently for each ET methods. The results showed that the Merton CRAE model had more physical significance and gave better agreement simulated stream flow and recorded flows. It noted that the Morton CRAE model might be more appropriate for the simulation of the actual evapotranspiration in SLURP hydrologic model.