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Volume 25 (2012)
- Issue 6 Pages 351-
- Issue 5 Pages 271-
- Issue 4 Pages 201-
- Issue 3 Pages 139-
- Issue 2 Pages 71-
- Issue 1 Pages 20-
Volume 25, Issue 6
Displaying 1-5 of 5 articles from this issue
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Original research article
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Hirofumi SUGAWARA, Ken-ichi NARITA2012 Volume 25 Issue 6 Pages 351-361
Published: November 05, 2012
Released on J-STAGE: July 12, 2013
JOURNAL FREE ACCESSRivers in cities mitigate thermal environments on hot summer days. This paper presents a discussion of physical mechanisms of that mitigation effect using field measurements taken in downtown Tokyo.
Because of heat transfer upward over river surfaces affected by sea breezes, air temperatures near rivers are lower than those in surrounding urban areas. Quadrant analysis revealed that this upward transfer results from the downward motion of colder air, not upward motion of heated air. The cold air mass above intrudes into the hot urban surface layer at the river space.
In daytime, deep rivers have a water surface that is colder than the air. Consequently, heat is transferred to the water surface. However, shallow river water heats air. The temperature difference between the water surface and the air above reverses at nighttime. These features are attributable to the fact that most net radiation at the water surface is partitioned into heat storage. The effective depth of water for thermal mitigation depends on the time of day.View full abstractDownload PDF (3806K) -
Feng SHI, Akio ONISHI, Masafumi MORISUGI2012 Volume 25 Issue 6 Pages 362-372
Published: November 05, 2012
Released on J-STAGE: July 12, 2013
JOURNAL FREE ACCESSAs with virtually any international river, many international disputes have arisen about allocation of water resources among countries located in the Mekong River Basin, where an appropriate approach to water-resource management must be applied. Moreover, the trade volume among countries of the Mekong River Basin, which increases annually, is expected to influence water resources strongly. In this context, the effects of international trade on water resources cannot be ignored when discussing appropriate approaches to water resources management. Therefore, in this study, we first analyzed the change of the structure of trade among countries located in the Mekong River Basin during 1999-2007 based on international trade data. The degree of interdependence among countries was also estimated. Subsequently, we estimated the virtual required water and the actually required water to support international trade in the Mekong River Basin. Finally, we discussed the interdependence of water resources among the countries of the Mekong River Basin, and present some advice related to water resource management for sustainable water resource use.managementView full abstractDownload PDF (2698K) -
Shunji KOTSUKI, Kenji TANAKA, Toshiharu KOJIRI, Toshio HAMAGUCHI2012 Volume 25 Issue 6 Pages 373-388
Published: November 05, 2012
Released on J-STAGE: July 12, 2013
JOURNAL FREE ACCESSThis study was conducted to propose a global water cycle model on land including irrigation and reservoirs. The proposed model, which comprises a hydrological and land surface model, a runoff model, and a reservoir operation model, simulates water flow on land globally. Cropping calendars for six crops (rice, spring wheat, winter wheat, maize, cotton, and soybean) were specified through phonological analysis of NDVI. A global river channel network is scaled up from a 1 km resolution flow direction map. Those land surface parameters well suit the statistical data. We conducted a global water cycle analysis over ten years. The main findings of results are as follows. Mean annual runoff agreed well with observed data without arid areas.Estimated yearly irrigation water requirements correspond to statistical data in many countries, suggesting that irrigation water requirements are analyzed well using our model. Reservoir operations have a strong impact on river discharge on land compared to withdrawal for irrigation.View full abstractDownload PDF (2316K)
Technical note
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Toru HIRAOKA, Hiromi YUKI, Minjiao LU2012 Volume 25 Issue 6 Pages 389-395
Published: November 05, 2012
Released on J-STAGE: July 12, 2013
JOURNAL FREE ACCESSThe distributed hydrological model used for this study includes many parameters, the setting of which requires expert engineering skills and much time. Easily determined parameters therefore contribute to setting work efficiency. However, runoff routing precision should be sufficient. This study therefore emphasizes the catchment capacity and final infiltration rate among the parameters. The runoff routing precision for the Kakehashi River basin is inspected using the catchment capacity and final infiltration rate in the Uetsuara River basin.View full abstractDownload PDF (895K)
Review article
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Hideshi IKEDA, Takashi WAKAMATSU, Ko NAKAYA, Seiya ABE2012 Volume 25 Issue 6 Pages 396-409
Published: November 05, 2012
Released on J-STAGE: July 12, 2013
JOURNAL FREE ACCESSRecently, forest management, especially thinning, has not been conducted adequately in Japanese forest areas. In poorly managed forest areas, sediment yield has occurred, which has degraded water resources. To restrain sediment yields and to conserve water resources, prediction models such as the Universal Soil Erosion Equation (USLE), Water Erosion Prediction Project (WEPP), and EUROpean Soil Erosion Model (EUROSEM) have been established and have been applied to agricultural fields in various countries including Japan. However, application of these models to mountainous forest watersheds has not been conducted frequently. For application of these models to watersheds, it is necessary to evaluate environmental conditions and sediment yield mechanisms. Then, these models must be applied on a watershed scale. In forest areas, forest floor components such as soil ground vegetation, litter, and organic soil layer (A0layer) prevent soil detachment and reduce the sediment yield. However, forest floor is reduced through deterioration of the photo-environment. It is necessary to observe and evaluate these mechanisms, and then to incorporate them into sediment yield models.View full abstractDownload PDF (648K)
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