JOURNAL OF JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES
Online ISSN : 1349-2853
Print ISSN : 0915-1389
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Original research article
  • Fumi OKURA, I Wayan BUDIASA, Nobuyuki SEKINO, Tasuku KATO
    2018 Volume 31 Issue 5 Pages 337-349
    Published: September 05, 2018
    Released: October 11, 2018
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     Factors and environmental conditions that lead to successful Participatory Irrigation Management (PIM) have not been identified in the literature. Clarifying a decision-making process of water allocation among farmers is expected to contribute to introduction of PIM. The entire water allocation decision-making process can be changed dramatically by farmers’ water allocation arrangements, which can also change because of a change in environmental conditions. An agent-based model (ABM) is applicable to elucidate such a dynamic process. This study used ABM to structure a water allocation problem to elucidate conditions in which behaviors such as coordination and adaptation emerge among farmers’ organizations. The study area included irrigation blocks in the Saba watershed in Bali, Indonesia. Our ABM was designed to replicate interactions between agents representing Subaks, which are water user organizations in Bali. Furthermore, behavior changes resulting from environmental conditions were compared. Water use of Subak in the upstream block was not interrupted by the other Subaks, but it was influential to the other Subaks, whereas the others used water conditionally. To understand these two patterns of water use, ABM simulated two scenarios for homogeneous and heterogeneous groups. The homogeneous groups had the same water use conditions. The heterogeneous groups had the same water use conditions. Results demonstrated that the heterogeneous groups had more cropping schedules than the homogeneous groups had. This difference of schedules produced erratic water use and structured the water allocation problem. Therefore, to introduce PIM, we propose that extra time be given for water use if a block has users susceptible to any such conditions.

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  • Taihei HAGA, Akiyuki KAWASAKI, Koji IKEUCHI
    2018 Volume 31 Issue 5 Pages 350-363
    Published: September 05, 2018
    Released: October 11, 2018
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     The numerous dams that were constructed during the post-war era in Japan have played a vital role as a foundation of economic development. Nevertheless, dam construction has sometimes provoked movements against construction. Such movements have had a wide variety of side effects such as prolonging construction and increasing costs from the government’s perspective, and damaging neighbouring communities from a residential perspective. Through this literature review conducted of 41 cases of movements against dam construction during the post-war era issues and periods of the respective movements were elucidated. Although earlier reports have described categorization of movement characteristics, changes in issues are clarified better in this study along with relations between historical changes in issues and social factors such as legal systems. Lifestyle and occupation conservation, which are likely to change because of construction projects, are no longer a main issue because of improved legal remedies. However, results show that environment, water demand estimation, and flood control effects remain as salient issues, indicating room for improvement of water resource development and management policies. As an example, a case study was conducted of the Ishiki dam project in Nagasaki prefecture. Changes in main issues of antiproject movements over time are highlighted. Results of this case study indicate tendencies of issue changes for the project, which mostly coincide with those occurring nationwide.

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  • Nanako ETOH, Akio ONISHI
    2018 Volume 31 Issue 5 Pages 364-379
    Published: September 05, 2018
    Released: October 11, 2018
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     In recent years, changes in river flow have occurred in various places due to the effects of climate change, affecting local and regional water resource estimates. A possible factor affecting water resource estimates is our social situation itself, such as the development of a declining birthrate and more-elderly society, which is changing dramatically. For this reason, studies on prediction and evaluation of such changes in river flow and water resource amount, as well as changes in our social situation, have become more important. However, most studies still focus only on aspects of natural change, such as climate change; therefore not many studies focus on changes in the activities of human beings and society, and the accompanying changes in land use. Changes in land use have a great impact on changes in river flow and water resource amount, because the amount of underground penetration of rainfall etc. differs for each type of land use. Therefore, by fully considering the future land use as well as the current situation, more accurate evaluation of future water resources becomes possible. The previous research have not included a comprehensive evaluation of watersheds throughout Japan for estimating future land use, and they have not covered a long-term estimation period to fully consider climate change either. For this reason, it has been difficult to compare and evaluate future land use changes in each watershed.
     In this study, in order to contribute to the analysis of changes in river flow and water resource amount in the future, land use for the period 2015-2100 (in 5-year intervals) was estimated by a tertiary mesh procedure for all of the 109 water systems of Japan. In addition, in consideration of anthropogenic changes, by evaluating four scenarios with different birth rates and death rates, we estimated the change of land use due to differences in future population numbers. As a result, it was found that the artificial land use of the 109 water systems of Japan decreased to the same level as in 1976. Our results clarified Japan’s future water resource situation given a high rate of decrease in artificial land use. Little difference was found among the evaluated scenarios.
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  • Katsushige SHIRAKI, Jinsheng SUN, Shota KAGAMI, Kumiko NAGAI, Yasuyuki ...
    2018 Volume 31 Issue 5 Pages 380-392
    Published: September 05, 2018
    Released: October 11, 2018
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     This study examined the accuracy of low-cost flow meters used for field observations. We specifically examined handmade tipping buckets flow meters, volumetric flow meters, and tap water meters. For inflow rates lower than one tip per 2 s, laboratory tests demonstrated that handmade tipping buckets flow meters have the same calibration line among inflow flux and one tipping quantity as commercial ones. Calibration curve characteristics of tipping buckets flow meters were estimated from the tipping time and storage volume when tipping. Stemflow observation measurements in the field with handmade tipping buckets meters were within 5% error. Volumetric flow meters and tap water meters must be used to add some flow current exchange systems because they are unable to detect water flow at lower flux, such as when they are dropping. Moreover, tap water meters require 2 m water height pressure at the meter exit. Volumetric flow meters have shown large error in field experiments because they are vulnerable to fluid impurities. Some measures must therefore be used to remove impurities. We were able to judge comprehensively that handmade tipping buckets flow meters are superior in many respects as low-cost flow meters for field observations.

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Technical note
  • Riku SATO, Hikaru AONUMA, Satoshi ANZAI, Natsuko SUENAGA, Ayako HASHIM ...
    2018 Volume 31 Issue 5 Pages 393-398
    Published: September 05, 2018
    Released: October 11, 2018
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     This study was conducted to elucidate difference of interest in rivers, mountains and seas and to propose plans to improve river popularity. We analyzed travel information magazines “Rurubu” and administered questionnaires to high school students. Three important conclusions were obtained. First, tourists visited the sites aimed at nature. Second, people in distant areas from sea might highly demand for river tourism. Third, leisure activities are effective for many young people. Furthermore, we propose three plans to encourage people to visit rivers. First, facilities around rivers must be enhanced. Second, marine leisure should be introduced into river areas. Third, water amenity facilities should be set near river.

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Original research article
  • Takashi WAKAMATSU, Hideshi IKEDA, Ko NAKAYA, Takashi ISHII
    2018 Volume 31 Issue 5 Pages 399-413
    Published: September 05, 2018
    Released: October 11, 2018
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     To observe the temporal changes of the surface runoff and sediment yields in forest slopes under conditions of high rainfall intensity, with consideration of the changing kinetic energy of a raindrop in the process of rainfall passing through the canopy, a new rainfall simulator was designed to sprinkle water above the canopy. Usefulness of the simulator was evaluated on a Japanese cypress (Chamaecyparis obtusa) plantation located in Gunma Prefecture, Japan. Intermittent water sprinklings was performed with durations of about 13, 32, and 16 min. Surface runoff and sediment yields were monitored using a bounded monitoring plot. The throughfall amount, raindrop sizes, and drop velocity were measured over the plot using a laser precipitation monitor. The throughfall intensities were between 195-378 mm h-1, which were judged to be reasonable based on the water balance in surface soil. Results of comparing the drop size and the drop velocity in a forest and in an open field indicated that the ratio of raindrops with larger size increased during passage through the canopy. Both the drop velocity in the forest and in the open field were lower than the terminal velocity and the velocity calculated using the branch height of the canopy. A positive correlation (r=0.96) was found between the throughfall intensities and the infiltration rate. As the rainfall continued, the surface runoff ratio did not change much. However, the ratio of sediment yield to kinetic energy of throughfall and surface runoff tended to decrease.

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Commentary article
  • Yasushi OHMASA, Shoji NOGUCHI, Yasuhiko OKADA, Shin’ichi IIDA
    2018 Volume 31 Issue 5 Pages 414-427
    Published: September 05, 2018
    Released: October 11, 2018
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     Forest resources are getting mature and are now ready for harvest in Japan. Therefore, sustainable use of forest resources is necessary through forestry and maintenance of environmental conservation in forests. First, we describe forests and forestry from the past to present in Japan. Second, we assess measures to fulfill multifunctional forest roles and explain the Forest and Forestry Basic Plan. Finally, we explain forest maintenance projects for the sustainable use of forest resources of forests in Japan and introduce the following associated studies: 1) development of forestry road network; 2) ensuring proper regeneration through re-planting, etc.; 3) promotion of land conservation; and 4) restoration and reconstruction following the Great East Japan Earthquake disaster.

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