Journal of Rainwater Catchment Systems
Online ISSN : 2186-6228
Print ISSN : 1343-8646
ISSN-L : 1343-8646
Volume 20 , Issue 2
Showing 1-13 articles out of 13 articles from the selected issue
  • Chisomo Patrick Kumbuyo, Katsuyuki Shimizu, Hiroshi Yasuda, Yoshinobu ...
    2015 Volume 20 Issue 2 Pages 1-6
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??This study deals with a way of predicting Malawi rainfall from global sea surface temperature (SST) using a simple multiple regression model. Links between Malawi rainfall and SST based on statistical correlations were evaluated and selected as predictors for the model. Monthly rainfall data from nine stations in Malawi grouped into two zones on the basis of inter-station rainfall correlations were used in the study. The predictors for Zone 1 model were identified from the Atlantic, Indian and Pacific oceans while those for Zone 2 were identified from the Indian and Pacific Oceans. The correlation between the fit of predicted and observed rainfall values of the models were satisfactory with r = 0.81 and 0.54 for Zone 1 and 2 respectively (significant at less than 99.99%). The results of the models are in agreement with other findings that suggest that SST anomalies in the Atlantic, Indian and Pacific oceans have an influence on the rainfall patterns of Southern Africa. We conclude that SST in the Atlantic, Indian and Pacific Oceans is correlated with Malawi rainfall and can be used to predict rainfall values.

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  • Chisomo Patrick Kumbuyo, Katsuyuki Shimizu, Hiroshi Yasuda, Yoshinobu ...
    2015 Volume 20 Issue 2 Pages 7-13
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??Correlations between summer rainfall in Malawi and global sea surface temperature (SST) were studied to elucidate the linkage between SST and rainfall. We used SSTs for the period 1979–2011 and rainfall data for 1981–2012 from nine stations, which were grouped into two zones on the basis of inter-station rainfall correlations. The Pearson correlation coefficient was used to test the hypothesis that the main influence on summer rainfall in Malawi was the Indian Ocean SST rather than the Pacific or Atlantic SST. We found that summer rainfall was more strongly correlated with the Indian Ocean SST compared to the Atlantic and Pacific Ocean SSTs. The correlations were more significant for northern stations than for central and southern stations. These results agree with other findings, the suggestion being that different climatic drivers influence the climate of different parts of Malawi. Northern areas are strongly influenced by the SST Indian Ocean dipole, whereas central and southern areas are strongly linked to the SST in the subtropical Indian Ocean. The results reveal that SST in the Atlantic Ocean off South Africa also affects Malawi rainfall. We conclude that the Indian Ocean SST, including in particular the SST dipole strongly influences Malawi rainfall.

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  • Tomoki Izumi
    2015 Volume 20 Issue 2 Pages 15-22
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??The effects of irrigation water temperature on soil temperature in rice paddy fields under saturated irrigation are numerically clarified. A numerical model that coupled a heat transport model and a soil water movement model was employed. The governing equations of the heat transport and soil water movement were described as the heat conduction equation and the mixed form of Richards equation, respectively, and discretized by the finite element method for space and the finite difference method for time. A portion of a paddy field that is adjacent to an irrigation canal was used for the computational domain. Given the irrigation water temperatures as the Dirichlet boundary condition, the simulations of time-varying soil temperatures in the domain were implemented. In addition, the effects of the meteorological conditions on soil temperature were investigated. The results show that the irrigation water temperature has an effect on the soil temperature of a paddy field under saturated irrigation. The difference in soil temperature due to the different irrigation water temperature given as the Dirichlet boundary condition significantly appears near the ground surface; the trough or peak values are approximately equal to the difference in the irrigation water temperature, and the difference in the time-averaged soil temperature is about half of the difference in the irrigation water temperature. Consideration of the meteorological conditions makes the surface heat budget during computation period change from a negative value to a positive one, and diminishes the effect of irrigation water temperature on soil temperature. Thus, the effect of irrigation water temperature on soil temperature is small compared to that of the meteorological conditions.

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  • Noriyuki Kobayashi, Takashi Kimata, Masayuki Ishii, Tatsuro Nishiyama, ...
    2015 Volume 20 Issue 2 Pages 23-28
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??It is important for the geotechnical engineers to predict the amount of the settlements as exactly as possible for the safe design of earth and hydraulic structures. The simple technique called mv method is often used to calculate the settlement for the small scale structure, and the parameter mv is properly necessary for the technique. Some researchers have presented empirical formulas for the estimation of mv that use single or multiple soil parameter models, such as natural water content, unconfined compressive strength, static penetration resistance and others. However, the estimated values of mv vary widely and there is not necessarily an extremely strong correlation. Moreover, if we try to present a new formula, it is difficult to determine some input soil parameters necessary to overcome complex multicollinearity problems. This study has proposed a simple method that estimate mv from some soil parameters using the artificial neural network (ANN) with batch learning algorithm developed by Kobayashi et al instead of performing the oedometer test. The optimum combination of input soil parameters has been evaluated and the results of the proposed method have been compared with 4 empirical formulas on the viewpoint of learning efficiency.

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  • -On-site test results clarifying the demand-supply deficit using level-reactive gates-
    Hitone Inagaki, Kazunori Masuda
    2015 Volume 20 Issue 2 Pages 29-35
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??This manuscript describes the function of upstream and downstream water level control gates that supply a quantity of water to a downstream storage area, depending on the prevailing upstream water level. Results from actual operations are presented, using a main channel of 11 pools located between two gates installed in a waterway. The results revealed that when the water quantity supply was less than the demand, there was a pool in which the movement of the storage quantity took a long time to pass through. This decreased the level of the waterway and caused the flow in a downstream pool to cease completely. A field test was conducted in which a supply and demand deficit was formed by altering the water level setting of a level-reactive gate. Typically, water level control gates allow water accumulated upstream to move according to the downstream draw. However, in the midstream and downstream sections, the storage quantity movement was ineffective, and the supply of water to a downstream pool disappeared. In a waterway with upstream and downstream water level control gates in ten locations, a water level decrease may occur in the event of a supply and demand deficit. For this reason, field tests were conducted, which suggested that the drawdown is caused by the water level setting of the water level control gate.

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  • -Simulation analysis of the supply and demand deficit using level-reactive gates-
    Hitone Inagaki, Kazunori Masuda
    2015 Volume 20 Issue 2 Pages 37-44
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??In a waterway with upstream and downstream water level control gates in ten locations, a water level decrease may occur in the event of a supply and demand deficit. For this reason, field tests were conducted, which found that the drawdown is caused by the water level setting of the water level control gate. Using a water level setting method to control the downstream water levels of level-reactive type gates, simulations were conducted to study the supply and demand deficit of the water quantity and the channel storage redistribution function for 11 pools located between two gates. When the channel storage is insufficient in downstream pools, a supply and demand deficit has occurred. Use of the water level setting method for the level-reactive type gate proved impossible to compensate for the deficit. This is because the level-reactive gate requires time for the upstream transmission of the hydraulic information related to the drawdown of the downstream gate, resulting in ineffective movement of the storage amount.

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  • - Simulation analysis of the supply and demand deficit using flow rate-reactive gates -
    Hitone Inagaki, Kazunori Masuda
    2015 Volume 20 Issue 2 Pages 45-52
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??In a waterway with upstream and downstream water level control gates in ten locations, a water level decrease may occur in the event of a supply and demand deficit. For this reason, numerical calculations and field tests were conducted and found that the drawdown is caused by the use of a level-reactive type method for the downstream water level settings of the gate. Using a water level setting method to control the downstream water levels of flow rate-reactive type gates, simulations were employed to study the supply and demand deficit of the water quantity and the channel storage redistribution function for 11 pools located between two gates. When the channel storage is insufficient in downstream pools, a supply and demand deficit has occurred. However, by using a flow rate-reactive gate, which allows the upstream transmission of downstream hydraulic information regarding the terminal demand, water can be moved rapidly from upstream pools to the downstream channel storage. Consequently, it is possible to prevent a supply shortage in distal pools.

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  • Masayoshi Harada, Akifumi Douma, Kazuaki Hiramatsu
    2015 Volume 20 Issue 2 Pages 53-60
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??Field measurement methods for chlorophyll a concentrations (Chl. a) have been developed, enabling data collection in a short time scale because of recent technological advancements in optical sensors. Such time-series data provides important findings in analyses and predictions of aquatic environments targeting eutrophic water areas. In this study, the water quality dynamics in a eutrophic reservoir in a flat low-lying agricultural area was analyzed from the viewpoint of short-time prediction of time series data using artificial intelligence to assess the water environmental dynamics related to a phytoplankton. Specifically, we proposed a short-term prediction method for Chl. a with the chaos recurrent neural network based on continuous observation data. This study aimed to improve the degree of prediction accuracy with observation noise processing, which uses wavelet analysis, and then examined the effectiveness of the prediction method. As a result, by introducing the noise processing, which uses wavelet analysis and reinforcement learning with supplemental training data, the accuracy of the predictions improved significantly and the practicality of the method proposed in this study increased, as evidenced by the fact that the lead time exceeded 48 h. In particular, it is suggested that predications are feasible with the same degree of accuracy for each lead time within the limit lead time. Yet distinctive variation patterns emerge with regard to changes in the algae species composition caused by artificial effects during the period in which water level management, which varies significantly from regular management, takes place. Therefore, it was difficult to conduct real-time predictions for chronological changes that share no similarities with such learning data.

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  • - A Case Study for the Trunk Lines Around Lake Biwa, Japan -
    Yoshinori Itani, Tatsuro Nishiyama, Takeshi Ibata, Toshinori Kawabata
    2015 Volume 20 Issue 2 Pages 61-66
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??For maintenance of irrigation pipelines over long spans of time, it is indispensable to clarify the actual situation of accidents along the irrigation pipelines. In this paper, the actual situation of the accidents of water leakage from the trunk lines of irrigation pipelines, which are laid in the 18 land improvement districts around Lake Biwa, Japan, was investigated. The accident rates, or the number of accidents per year, and length of laid pipes, were obtained from the data provided by the practical managers. Furthermore, the accident rates were found to be related to the type, the diameter and the period of use of the pipes. As a result, it was concluded that the accident ratios of ductile cast iron pipes and steel pipes are lower than those of other pipes ; the accident ratio of fiberglass reinforced plastic mortar pipes is the same as that of both prestressed concrete pipes and asbestos pipes. No relationship has been found between the accident ratio and the diameter. Moreover, the accident ratio of the fiberglass reinforced plastic mortar pipes, which have been used for over 20 years, is high.

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  • Yukiyoshi Teramoto, Masaru Oka, Etsuro Shimokawa, Suk-Woo Kim, Kun-Woo ...
    2015 Volume 20 Issue 2 Pages 67-74
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??We conducted field investigations to study temporal changes in erosion and collapse types and sediment yields of yarding roads in an abandoned clear-cut plantation forest. The study site in Kumamoto Prefecture, Japan, is 0.89 km2, and was clear-cut in September 2002. Moreover, to study sediment yields before replantation was abandoned in the study site, we interpreted aerial photographs taken in 1963, 1968, 1977, 1983, 1988, and 1995. Many of the shallow landslides that occurred on replanted slopes in the study site before replantation was abandoned were smaller than 400 m2, and were on slopes with gradients greater than 30 degrees. Sediment yields from these landslides were greater when the tree age was 20 years or less than when the tree age was 20 years or more. The annual average sediment yield/km2 between September 2002 and 2007 from yarding roads in the abandoned clear-cut forest was~17 times greater than the maximum annual sediment yield/km2 from shallow landslides on replanted slopes prior to abandonment of replantation. The annual sediment yield/km2 from September 2007 to 2008 from those yarding roads was~7 % of the annual average yield during that period from yarding roads. The decrease in annual sediment yield/km2 from the yarding roads was due to washout of slope collapse material from filled slopes toward lower parts of the slopes and an increase in the rate of water infiltration caused by vegetation spread into cuttings in grass tracks for cutting and filling slopes.

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  • Eiji Ichion, Kyohei Maeda, Yoichi Fujihara, Shunsuke Chono, Uéda Tetsu ...
    2015 Volume 20 Issue 2 Pages 75-83
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??Two pool and weir fishways with orifices were installed on a trial basis between a spring-fed pond and two agricultural watercourses in Shika, Ishikawa, Japan, where pungitius sp. 1 (nine-spined stickleback) lives. In order to determine the function of fishways installed for migrating nine-spined sticklebacks, fixed net survey in the exit of the fishways and scrape net survey in the entrance of the fishways were conducted. The fixed net survey showed that the total of 6,900 (left fishway: 1,687 ; right fishway: 5,213) nine-spined sticklebacks, including 1,920 immature fish, had passed upstream through the fishways during the period from September 2009 to December 2010. The ascending number of pungitius sp. 1. increased in spring (March-April), early summer (June-July) and fall (September-November). The fish sampling survey showed that nine-spined sticklebacks which were mainly composed of immature fish stagnated in the entrances of fishways during the period of December 2009 to May 2010. The survey results indicated that the fishway had a sufficient function of upstream migration for adult nine-spined stickleback in the reproductive season.

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  • Eiji Ichion, Kyohei Maeda, Shuhei Yamamoto, Shuhei Nakano, Shunsuke Ch ...
    2015 Volume 20 Issue 2 Pages 85-92
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??Three types of upstream-inclined plank weir have been tested in order to develop small-scale fishway for the fishes around paddy fields. The experiments were conducted using leveled-crested upstream-inclined plank weir of rectangular section (Type 1), inclined-crested upstream-inclined plank weir of rectangular section (Type 2), leveled-crested upstream-inclined plank weir of trapezoidal section (Type 3) and leveled-crested vertical plank weir of rectangular section (Control type). The ascending experiments of Orizias sakaizumii and Misgurnus anguillicaudatus were conducted with the water-level difference of 6cm and 9cm between upstream and downstream at the volumetric flow rate of 5.3 and 1.9L/s. The experimental results showed that upstream-inclined plank weirs were superior to vertical plank weir in the rate of ascending and the Type 2 plank weir had stable ascending rates of the two fishes. Multiple linear regression analyses showed that (i) Type 1, Type 3, ascending distance, ascending angle, water temperature, discharge and water-level difference significantly affected the ascending rate of Orizias sakaizumii, (ii) Type 2, Type 3 and ascending angle significantly affected the ascending rate of Misgurnus anguillicaudatus.

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  • -A Case Study in Ishikawa, Japan -
    Noriko Kusamitsu, Eiji Ichion, Tetsuyuki Uéda
    2015 Volume 20 Issue 2 Pages 93-102
    Published: 2015
    Released: August 06, 2019
    JOURNALS FREE ACCESS

    ??The change of environment-conscious construction methods in land consolidation projects was investigated on the case of Ishikawa, Japan. The results showed that (1) the installation of environment-conscious facilities in Ishikawa began just after the notice of land improvement projects by the Japanese government in 1991, (2) the rate of land consolidation projects which included environment-conscious facilities reached 80% already when the revised Land Improvement Act was enforced, and has become 100% recently, (3) in each project the number of the kinds of environment-conscious construction methods and targeted conservation species has been increasing, (4) recent land consolidation projects had a tendency to select oriental weather loach and frogs for targeted conservation species, and (5) overusing of concrete products for environment-conscious facilities has become prominent. It was inferred that the recent trend of overusing concrete products has been caused by the regard to the local residents forced to the burden of the maintenance of the facilities, and besides by the prefectural government policy that concentrates to the conservation of particular species. We considered that it is necessary to change the consciousness of local residents against coexisting plants and animals, in cooperation with an environmental education, to achieve more effective facilities for conservation of biodiversity.

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