Study on Influences of Salinization on the Evaporation Processes in a Semi-arid Area in Western Australia
| Project/Area Number |
15560447
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
水工水理学
|
|---|
| Research Institution | Daido Institute of Technology |
|---|
Principal Investigator |
SHIMOJIMA Eiichi Daido Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (80027276)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TAMAGAWA Ichiro Gifu University, River Basin Research Center, Associate Professor, 流域圏科学研究センター, 助教授 (40273198)
|
|---|
| Project Period (FY) |
2003 – 2004
|
| Project Status |
Completed (Fiscal Year 2004)
|
| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2004: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥2,000,000 (Direct Cost: ¥2,000,000)
|
|---|
| Keywords | evaporation / salinization / semi-arid area / Western Australia / observed data analysis / evaporation experiment / 半乾燥地 |
|---|
| Research Abstract |
In order to clarify the relation between evaporation from the ground surface and salinization, a meteorological and hydrological observation was undertaken in a bare soil area in a semi-arid region (Yalanbee), Western Australia for three years from 2000. In this research, through analysis on that obtained data and a subsidiary evaporation experiment so on, that relation was investigated. The following was disclosed:
(1) In the field, salty crust is formed by occurrence of evaporation in summer (dry season) and in. winter (wet season) soil is wetted by rainfall events. However albedo (reflection rate of solar radiation on the ground) in the dry season becomes by 10% smaller than that in the wet season. This reverse relation could not be recognized through an experiment using Yalanbee-soil and still remains as a future problem.
(2) Albedo in the field in the dry season decreases with solar altitude, but its minimum was detected to appear not at noon but around 10 a.m. This is considered to
… More
be due to drying of ground surface by evaporation because reduction of soil wetness usually lets the albedo increase. This situation corresponds to such a result by a dome evaporation experiment that evaporation rate decreases abruptly from around 10 a.m. via its continuous increase from sunrise due to increasing solar radiation.
(3) In the dry season, daily changes in atmospheric temperature-humidity and solar radiation cause the evaporation -condensation in the soil. Through a laboratory Yalanbee-soil column experiment under a meteorological condition similar to these actual variations, it was clarified that, when vapor movement in the soil layer is described by a diffusion equation, its modified diffusion coefficient becomes approximately 100 times larger than the original one. This increase is concluded to be caused by occurrences of evaporation and condensation, and structure and behavior of the modified coefficient were also clarified theoretically
(4) In an evaporation experiment using the soil column with a shallow water-table, salty crust was observed to be formed non-uniformly on the upper soil surface and its development was very fast as the crust area became about 60% within about five days from the beginning of experiment. Also it was recognized that the evaporation rate decreased linearly with inverse of the crust area, and reduction in effective transferable cross-section for vapor leads to the decrease in vapor flux, evaporation rate, significantly. Less
|
Report
(3 results)
Research Products
(3 results)
-
-
[Journal Article] Variational Characteristics of Ground temperatures in a Semi-Arid Area, Western Australia2004
Author(s)
Enomoto, T., Shimojima, E., Horiuchi, M., Tamagawa, I., Woodbury, R.
-
Journal Title
Proc. of Annual Meeting of JSCE (in Japanese) NO.59(II)
Pages: 17-18
Description
「研究成果報告書概要(欧文)」より
Related Report
-
