• Journal of Environmental Science International
• /
• v.22 no.1
• /
• pp.119-129
• /
• 2013

We compared equilibrium evaporation($E_{equili}$) eddy-covariance($E_{eddy}$) with soil moisture data($E_{SMseries}$) which were measured with a 2 hours sampling interval at three points for a humid forest hillslope from May 5th to May 31th in 2009. Accumulations of $E_{eddy}$, $E_{equili}$ for the study period were estimated as 2.52, 3.28 mm and those of $E_{SMseries}$ were ranged from 1.91 to 2.88 mm. It suggested that the eddy-covariance method considering the spatial heterogeneity of soil evaporation is useful to evaluate the soil evaporation. Method A, B and C were proposed using mean meterological data and daily moisture variation and the computations were compared to eddy-covariance method and equilibrium evaporation. The methods using soil moisture data can describe the variations of soil evaporation from eddy-covariance through simple moving average analysis. Method B showed a good matched with eddy-covariance method. This indicated that Dry Surface Layer (DSL) at 14:00 which was used for method B is important variable for the evaluation of soil evaporation. The total equilibrium evaporation was not significantly different to those of the others. However, equilibrium evaporation showed a problem in estimating soil evaporation because the temporal tendency of $E_{equili}$ was not related with the those of the other methods. The improved understanding of the soil evaporation presented in this study will contribute to the understandings of water cycles in a forest hillslope.

• Journal of Environmental Science International
• /
• v.4 no.5
• /
• pp.427-435
• /
• 1995

In order to discuss the differences among the SMP(Surface Moisture Availability Parameter), by previous researchers on the basis of their own theoretical and empirical background, we assessed the SMP according to the soil types and volumetric soil water contents. The results are as follows. There are differences among all the five SMAPs. There's a tendency that the larger grain size, the higher value of parameters. And they divided into two groups for their value: one group has parameters with exponential function and the other with cosine and linear function. The maximum difference between the two groups appears when the volumetric soil water contents are 0.07m3m-3 for sand, 0.l1m3m-3 for loam, 0.12 for clay, and 0.13m3m-3 for silt loam. So, these differences must be considered when we estimate the surface evaporation rate. From field data, the paddy field soil around Junam reservoir is classified as a silt has high wetness, 0.56. So, the parameter obtained from the field measurement is much higher than that of Clapp and Hornberger(1978)'s Table. This study treated the SMP for a certain point of time in winter season. But if we measured the soil water contents continuously, we could obtain better time-dependent parameter. Key words : SMAP(Surface Moisture Availability Parameter), Paddy field, Volumetric soil water content, Evaporation, Capillary potential.

• The Korean Journal of Ecology
• /
• v.2 no.1
• /
• pp.31-37
• /
• 1978

The salt accumulation on the soil surface can be mathematically described. Although the movement of salts in soil solution is expressed in terms of mathematical model, which has certain limitations in practical application, except the exchangeable and absorbable state salts in soil solution. This model is illustrated by analyticl experiments in which evaporation from the bare soils, transpiration of plants and rainfall are required. Agreement between the model and the measured data was satisfactory, which validating the salt accumulation theory on the soil surface.

• Journal of Korea Water Resources Association
• /
• v.45 no.6
• /
• pp.557-568
• /
• 2012

In order to understand the hydrological processes on the mountainous forest, the configuration of soil evaporation (E) out of evapotranspiration (ET) is a challenging and important topic. In this study, we attempted to understand the soil evaporation process for a humid forest hillslope via measuring and analyzing soil moistures with a sampling interval in 2 hours at three locations for 10 days between May 22th and 31th 2009. Two methods were used to estimate soil evaporation in every 2hr; one is a method using soil moisture measurement ($E_{SM}$), the others methods are based on Penman equation (Penman (1948), Staple (1974), Konukcu (2007), Equilibrium Penman ($E_{equili}$)). As a critical parameter in determining $E_{SM}$, the dry surface layer (DSL), was estimated using energy balance equation. The accumulated soil evaporation ($E_{SM}$) of A, B, C points were estimated as 2.09, 1.08 and 2.88 mm, respectively. The estimated evaporation of Penman (1948), Staple (1974), Konukcu (2007), $E_{equili}$ were 4.91, 8.80, 8.63 and 3.28 mm. The proposed method with soil moisture measurement showed lower soil evaporations than the other conventional methods. The increasing soil temperature and interaction between soil and atmosphere due to existence of litter and DSL are considered as dominant factors for soil evaporation. The $E_{SM}$ has the apparent lag time between 2 and 4 hr compared with $E_{equili}$ and net radiation. The DSL and surface resistance ($r_s$) were increased as soil moisture was decreased for in this study. The estimated DSL through the temporal distribution analysis of soil moisture and tension measurements was also similar to that of the energy balance relationship.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.4
• /
• pp.55-64
• /
• 2003

Desiccation of a soil is basically the removal of water by evaporation, which is controlled by evaporativity and evaporability. Surface evaporation improves the trafficability which is essential for the access of construction equipment in the area reclaimed with soft clay. The existing traditional methods for evaluating evaporation can not account for the deformation of reclaimed soft soils during evaporation. Therefore, a theoretical model for predicting the rate of evaporation from the surface of a deformable material is proposed. The model is based on a system of equations for coupled heat and mass transfer in unsaturated soils. The modified pressure plate extractor test and glass desiccator test were carried out to obtain the soil-water characteristic curve for a deformable soil. The column drying test was conducted to investigate one dimensional water flow, heat flow and evaporation in the surface. A finite difference program was developed to solve the coupled nonlinear partial differential equations, which permit the study of water, vapor and heat flows in the deformable soil. Comparison between measured and simulated values shows a reasonably good matching between the two.

• Journal of Environmental Science International
• /
• v.4 no.5
• /
• pp.41-41
• /
• 1995

In order to discuss the differences among the SMP(Surface Moisture Availability Parameter), by previous researchers on the basis of their own theoretical and empirical background, we assessed the SMP according to the soil types and volumetric soil water contents. The results are as follows. There are differences among all the five SMAPs. There''s a tendency that the larger grain size, the higher value of parameters. And they divided into two groups for their value: one group has parameters with exponential function and the other with cosine and linear function. The maximum difference between the two groups appears when the volumetric soil water contents are 0.07$m^3m^{-3}$ for sand, 0.l1$m^3m^{-3}$ for loam, 0.12 for clay, and 0.13$m^3m^{-3}$ for silt loam. So, these differences must be considered when we estimate the surface evaporation rate. From field data, the paddy field soil around Junam reservoir is classified as a silt has high wetness, 0.56. So, the parameter obtained from the field measurement is much higher than that of Clapp and Hornberger(1978)''s Table. This study treated the SMP for a certain point of time in winter season. But if we measured the soil water contents continuously, we could obtain better time-dependent parameter.

• Geomechanics and Engineering
• /
• v.21 no.3
• /
• pp.237-245
• /
• 2020

The process of evaporation from free water surface was simulated in a large scale environmental chamber under various controlled atmospheric conditions and also was modelled by a new mass transfer model. Six evaporation tests were conducted with increasing wind speed and air temperature in the environmental chamber, and hence the effect of atmosphere parameters on the evaporation process and the corresponding response of water were investigated. Furthermore, based on the experiment results, seven general types of mass transfer models were evaluated firstly, and then a new model consisted of wind speed function and air relative humidity function was proposed and validated. The results show that the free water evaporation is mainly affected by the atmospheric parameters and the evaporation rate increases with the increasing air temperature and wind speed. Both the air and soil temperatures are affected by the energy transformation during water evaporation. The new model can satisfactorily describe the evaporation process from free water surface under different atmospheric conditions.

• Water for future
• /
• v.5 no.2
• /
• pp.44-48
• /
• 1972

This article includes hydrometeorological analysis of evapotranspiration and precipitation, which are used available basic data for a certain basin water budget. Evapotranspiration on water surface, bare soil and rice fields is directly measured by Thornthwaite's type Lysimeter and on water surface and vegetables computed using the Penman's equation. Areal precipitation is analized through the Thiessen method and arithmatic mean method. It is interested fact that the correlation coefficient for Class A Pan's evaporation vs. the actual evapotranspiration is the highest value among the coefficients for different type evaporimeter and Penman equation, and evaporation ratio on rice field's evapotranspiration vs. Class A Pan's evaporation is 1. 5-2. 3.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
• /
• 2011.11a
• /
• pp.7-10
• /
• 2011

The semi-arid and arid regions comprise almost 40 percent of the world's land surface. The low and erratic precipitation pattern is the single most significant contributor for limiting crop production in such regions where rainfall is the source for surface, soil and ground water. In a changing climate, the semi-arid and arid regions would increasingly face the challenge of water scarcity. According to the relevant literature; under the assumption of a doubling of the current atmospheric CO2 concentration, irrigation demand was estimated to increase for wheat and to decrease for second crop maize in a Mediterranean environment of Turkey in the 2070s. Crop evapotranspiration would decrease due to stomata closure. Reference evapotranspiration and potential soil evaporation were projected to increase by 8.0 and 7.3%, respectively, whereas actual soil evaporation was predicted to decrease by 16.5%. Drainage losses below 90 cm soil depth were found to decrease mainly due to lesser rainfall amount in the future.

• Korean Journal of Soil Science and Fertilizer
• /
• v.25 no.4
• /
• pp.311-324
• /
• 1992

Polymeric substances in organic matter of soils aggregate soil particles into a crumb structure which greatly influences such properties as water movement, aeration and heat transfer. Poorly-structured soils may be improved by the incorporation of synthetic polymers where the main objects are : promoting germination or establishing crops, improving drainage, combating wind and water erosion, and reducing evaporation from the surface of soil under arid condition.