Journal of Rainwater Catchment Systems
Online ISSN : 2186-6228
Print ISSN : 1343-8646
ISSN-L : 1343-8646
Volume 14 , Issue 2
Showing 1-19 articles out of 19 articles from the selected issue
  • Type: Cover
    2009 Volume 14 Issue 2 Pages Cover3-
    Published: 2009
    Released: September 13, 2016
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  • Type: Appendix
    2009 Volume 14 Issue 2 Pages App2-
    Published: 2009
    Released: September 13, 2016
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  • [in Japanese]
    Type: Article
    2009 Volume 14 Issue 2 Pages i-
    Published: 2009
    Released: September 13, 2016
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  • Type: Index
    2009 Volume 14 Issue 2 Pages Toc2-
    Published: 2009
    Released: September 13, 2016
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  • Akira Kobayashi, Kiyohito Yamamoto, Keisuke Inoue, Shigeyasu Aoyama
    Type: Article
    2009 Volume 14 Issue 2 Pages 1-8
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    The data on fracture frequency is easy to get at an in-situ investigation, while the permeability tests are not carried out so often because of financial limitation. Thus, it is very valuable to establish a technique to estimate the permeability distribution by using the data easily obtained like the fracture frequency. In this paper, an indicator simulation technique of the geostatistics was applied by using the fracture frequency as the soft data. To improve and develop the technique, the discrete fracture network generation method was applied to estimate the fracture frequency distribution. It was found as a result that it was effective to generate the permeability distribution by using only the fracture frequency when the number of permeability data was small and that of fracture frequency was large.
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  • Subas Chhatkuli, Masayuki Fujihara
    Type: Article
    2009 Volume 14 Issue 2 Pages 9-19
    Published: 2009
    Released: September 13, 2016
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    Two dimensional shallow water equations are solved by applying a Godunov-type numerical method to analyze the flows in fishways with obstructions of circular and rectangular shapes of equal area, embedded with regular and staggered patterns. Results show that obstructions embedded with a regular pattern creates shorter fish pathways and larger low velocity regions although flow is accompanied with a little higher velocity at the center of gaps. Water depth and its distribution pattern in a pool are almost the same when the obstructions with circular/rectangular shapes are embedded with a regular pattern. However, obstructions embedded with a staggered pattern create alternate shallower and deeper pools in fishways.
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  • Shunsuke Chono, Shigeya Maeda, Toshihiko Kawachi, Koichi Unami, Junich ...
    Type: Article
    2009 Volume 14 Issue 2 Pages 21-28
    Published: 2009
    Released: September 13, 2016
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    Paddy farming is the cause of water pollution in many parts of the Asian monsoon district. As a primary study for strategically managing river water quality on a watershed scale, the dynamics of nonpoint source pollutant loadings from paddy farming area are examined for a selected agricultural watershed where a river runs through and rice paddies take greater part of the farmland. A total of 122 outfalls at which drainage (irrigation runoff) waters enter the river are exactly identifiable along the whole course of the river. Results of the detailed surveys of drainage waters, conducted at typical stages in an indigenous calendar of paddy farming practice (CPFP) in an irrigation season as well as at a few stages in the off-season, are analyzed. Major findings are as follows. (1) Any of the COD_<Mn>, NO_3-N, T-N and T-P loadings totalized over all the outfalls is maximized in puddling and transplanting with basal fertilizer application. (2) The concentrations of NO_3-N and T-N, averaged over all the outfalls, are rather low during the irrigation period of mid April to early September. Nevertheless the loading amounts of them remain high during the same period, relatively closely correlating with the amount of outfall discharge. (3) Topdressing the paddies in the booting stage of rice causes a distinguishable extra load of NO_3-N. (4) The dynamics of the COD_<Mn> and T-P loadings are totally different from those of the NO_3-N and T-N loadings, taking straightforward declines from their maximums or being significantly restricted by their concentrations rather than by outfall discharges.
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  • Masayuki Fujihara, Ayako Fujita
    Type: Article
    2009 Volume 14 Issue 2 Pages 29-33
    Published: 2009
    Released: September 13, 2016
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    This paper presents a simple estimation method of hydraulic structure in a fan-shaped fishway, based on the field observation on the fishway installed at Kuranomachi Weir in Ono River in Matsuyama, Ehime, Japan. The flow regime in the pools of the fishway was a plunging flow with discharge ranging from 200l/s to 350l/s. The estimation procedure, given the discharge, is as follows: 1) Estimate the water depth on the notch of the baffle, 2) Estimate the flow velocity on the notch using the estimated water depth, and 3) Estimate the magnitude of the velocity distributed in the pool downstream of the notch using the estimated flow velocity on the notch. A maximum velocity in the pool, approximately 1.75 times the velocity on the notch, is estimated at the plunging point.
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  • Henrie Manford Njoloma, Ichiro Kita, Yoshinobu Kitamura, Satoka Aoyagi
    Type: Article
    2009 Volume 14 Issue 2 Pages 35-44
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    Malawi's agricultural sector is the main contributor to the national economy. Its activities are, however dependent on rainfed farming and it suffers from the consequences of poor policy implementation and management, as well. Irrigation has, for a long time, been viewed as a major component in agriculture but its implementation has been facing challenges and problems ever since the initiative was formally introduced. The status of irrigation farming in Malawi was studied based on four major national schemes selected based on their size, age and management, and implementation style. Ten study elements crucial in assessing performance of irrigation farming were identified and each studied in relation to the schemes. Each study site was examined within the context of these study elements to understand the core issues under study. The analyses showed that despite the abundance of water in the country, irrigation is still very dismally implemented making agricultural production low, causing serious household food insecurity and distorting the national economy. Some achievements have been made to stir the irrigation sector into a viable contributor to the agricultural sector; but it is still far from being a vibrant factor for a reliable production.
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  • Atsushi Yada, Atsushi Yamafuji, Atsushi Matsuoka, Nirmala Devi Bhatta
    Type: Article
    2009 Volume 14 Issue 2 Pages 45-51
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    The purpose of this paper is to grasp the level of satisfaction by inhabitants for the agricultural water use facilities, and clarify the direction of improvement. To approach the above subject, the authors sent questionnaires to inhabitants in Minamiumemoto, Takai and Nakano district in Dogo plain, Ehime prefecture during December, 2004 and performed CS portfolio analysis as an evaluation technique. The items of research are the satisfaction for agricultural water use facilities, "Natural environment", "Scene", "Management", "Sense of closeness", "Water quality", "General satisfaction", and the concern for agricultural water use facilities. The results of this study are as follows: (1) As a result of having researched concern and satisfaction by inhabitants for the agricultural water use facilities, the level of concern in Minamiumemoto district is low in comparison with other two districts, and the level of satisfaction in Nakano district is low. On the other hand, in Takai district where environmental maintenance of the waterside is performed positively, the level of both two items is high in comparison with other two districts. (2) As a result of CS portfolio analysis, it is clarified that "Water quality" shows the improvement point in three districts. But the background of this is different in every district, and different methods are necessary for the measures. (3) Satisfactory structure is different for the other four items in every district. In Minamiumemoto district, items except "Water quality" is evaluated in some degree, particularly "Sense of closeness" shows the superiority point. In Takai district, "Sense of closeness" shows the precaution point, "Natural environment" and "Scene" shows the improvement point, for the consciousness for environment is high in comparison with other districts. In Nakano district, "Management" shows the precaution point, and this reflects dissatisfaction for the present conditions of the management system of agricultural water use facilities.
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  • Yuji Sakurai, Kazuyuki Yano
    Type: Article
    2009 Volume 14 Issue 2 Pages 53-58
    Published: 2009
    Released: September 13, 2016
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    In Japan, fallow paddy fields and abandoned paddy fields have increased through the rice acreage reduction policy for dealing with surplus rice, depopulation, or aging of the population. It is important to manage and maintain those paddy fields in a condition in which they are immediately and easily available for use as rice fields in the future. Control of weeds cannot be neglected in order to use fallow paddy fields as a rice fields soon. We think that much manpower and a cost are not necessary, and that the herbicides that have a bad influence on the surrounding environment, especially the rice field ecosystem should not be used for managing fallow paddy fields. As a way of satisfying these conditions, an examination of the control of water by the deeper ponding method was made. First, we examined the relations of the ponding depth of water and the growth of weeds in an experimental rice field. As a result, the abundance of weeds decreased as the ponding depth increased. Also, grass did not grow at all in water 5cm or more in depth during winter and in water over 15cm depth during summer. We arrived at the standard ponding depth of water for managing fallow paddy fields from this examination. Therefore, we proved that though some kinds of waterweed appeared, a grass did not appear as a result of managing the ponding depth of water at about 15cm in summer in an actual fallow paddy field.
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  • Kazuyuki Yano, Yuji Sakurai
    Type: Article
    2009 Volume 14 Issue 2 Pages 59-65
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    The authors have proposed a method of managing fallow paddy fields to control the growth of weeds and to maintain conditions for their potential as paddy fields by irrigation of fields at a depth of 15cm. However, the growth of paddy field weeds varies with the condition (kind and quantity) of seed buried in the soil, natural conditions such as air temperature, and regional difference in growth distribution have been reported. We investigated the kind and quantity of weeds that occurred in six fallow paddy fields in Ehime Prefecture during the six years from 2002 to 2007. Geographical features and surrounding conditions varied in the fields. The fields were managed according to the method of irrigating fallow paddy fields proposed by the authors. As a result, though the kind and quantity were different, weeds which appeared in each fallow paddy field could be restrained at a level at which the paddy field could be returned to use easily. Also, it was proved that the proposed method was effective in management and control of fallow paddy fields. Moreover, information about the control of weeds was obtained, for example, that once weeds have appeared when the depth of water becomes shallow, we cannot control their growth even if the water is made deeper.
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  • Miki Ogawa, Mitsuo Fukada
    Type: Article
    2009 Volume 14 Issue 2 Pages 67-72
    Published: 2009
    Released: September 13, 2016
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    Water contamination in drainage ditches due to soil puddling has been identified as an important problem and this study investigated the filtration of the resulting turbid waters. Bamboo coal was used as a filtering material by absorbing the soil particles and other suspended materials from the turbid waters. In this research, effectiveness of different arrangement of bamboo coal in a modeled channel was investigated. It was found out that turbid water filtration using the net, commonly used for mandarin orange bags, was the most effective method. It is most probably because both the bamboo coal and the net adsorb the soil particles and the spaces between them become sedimentation traps. The arrangement of the bamboo coal in the drainage area to allow space for sedimentation was also found important.
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  • Takayuki Kuraoka, Fumiyoshi Kondo, Jun-ichi Shoji, Takefumi Nakazono, ...
    Type: Article
    2009 Volume 14 Issue 2 Pages 73-79
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    A model equation for estimating the ground water levels using Landsat TM data was examined in this paper, based on the results of site investigation of land cover contexts and ground water levels in Yoron Island. Firstly, land cover classification was conducted by supervised classification and the monitoring wells sited in agricultural areas were extracted. The data collected in these wells was used for estimating the ground water levels as the site investigation data. Next, a model equation for estimating the ground water levels was created by inter-band calculations among the CCT values of the TM data as independent variables in the multiple regression analysis. The validity of this model equation was proved by applying it to the other monitoring wells where the collected data was not used for creating the equation. Then, the model equation was found out to be generally applicable for estimating the ground water levels within the limits of approximately 5-20m.
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  • Masafumi Katou, Yasuhiro Akiyoshi, Shinichi Takeshita
    Type: Article
    2009 Volume 14 Issue 2 Pages 81-86
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    In the recent years, there has been heavy rain near the Kakihara River and its basin, which is located in the southern part of Miyazaki City. Internal water damage occurred due to a decline in the river's flowing capacity and increased construction in the area. A sluiceway and drainage pumping station have been established in the lower area of the Kakihara River as a countermeasure against the internal water damage. However, the station encounters serious problems with regard to pumping the river water during heavy rains. For this reason, the flow of the river was interrupted where the Kakihara River and the Shimanda River meet at a right angle. As the result, the internal water damage occurred. Therefore, we have tried to control the river water with a training levee by using a hydraulic model experiment where the two rivers connect, adopting the style of the interchange of expressway. We succeeded in controlling the current of the river and also report a slight lessening of the internal water damage mentioned above.
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  • Masayoshi Harada, Kazuaki Hiramatsu, Takashi Saitoh, Makito Mori, Atsu ...
    Type: Article
    2009 Volume 14 Issue 2 Pages 87-96
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    In a eutrophic reservoir under a scarce underwater light environment due to a large amount of fulvic acid, the dynamics of chlorophyll-a and dissolved oxygen (DO) were examined by water quality monitoring and numerical simulations with a vertical one-dimensional ecosystem model. In addition, the effect of the improvement of transparency on their dynamics was evaluated by a scenario analysis. In the summer, the objective water body was under an extremely scarce underwater light environment since blue-green algae were generated in large quantities at the water surface. At a depth of more than 1m, chlorophyll-a concentration did not increase owing to the limitation of light intensity, and the water body entered the anaerobic state. In the autumn, the chlorophyll-a did not increase because of the nutrient limitation, although the influence of the light limitation decreased in a depth of less than 4m by the attenuation of blue-green algae. The vertical diffusion transport of DO, however, increased by the formation and progress of the mixed layer at a depth of less than 5m, resulting in an improvement of the anoxic state. The results of the scenario analysis indicated that the progressing of the current transparency (0.5?1.4m) to 3m led to the decrease of phytoplankton due to the nutrient limitation and the improvement of the anoxic state in the whole vertical area, although phytoplankton temporarily increased from the decrease of the light limitation.
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  • Masayuki Fujihara
    Type: Article
    2009 Volume 14 Issue 2 Pages 97-98
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
    It is highly esteeming and a great honor to have received a nomination for the 2008 JRCSA Award and being presented with it during the 16th JRCSA annual congress held on November 1, 2008 in Tsuruoka, Yamagata, which was organized by Dr. Yuki Nakajima, Executive and Vice-President of Yamagata University. I extend my sincere thanks to the Award Screening Committee, chaired by Dr. Yoshitaka Yoshitake, Professor of Ehime University, for elevating me to the status of a JRCSA Award recipient; and to the members of the JRCSA Executive Board and Council headed by Prof. Dr. Tsugio Ezaki, President of JRCSA. Also, special thanks are due to Dr. Tadao Fukushima, Professor Emeritus of Ehime University, and other co-workers for pursuing projects with me.
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  • Type: Appendix
    2009 Volume 14 Issue 2 Pages 99-105
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
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  • Type: Cover
    2009 Volume 14 Issue 2 Pages Cover4-
    Published: 2009
    Released: September 13, 2016
    JOURNALS FREE ACCESS
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