Securing safe water is an urgent issue to be solved in rural societies in developing countries. Conventional water environment improvement through public works, putting priority on development of water resources, such as construction of dams, well digging, etc., has shown successful results in one hand. However, on the other hand, they generally require large investment cost, long time for administrative process. In addition, inequity of benefit to residents is associated as a potential problem. Meanwhile, intensive use of the existing water resources, with cheap cost and simple technologies, can be effective alternative measures against water shortage where development of water resources is restricted. From the viewpoint, the Study is being conducted to propose water environment improvement through intensive use of the existing water resources. According to the results of the on-site survey conducted in the West Nusa Tenggara Province, Indonesia, it was found out that water environment in the province is deteriorating due to development of beef cattle raising and deforestation. In this paper, the results of the on-site survey are summarized and the water environment improvement plan to mitigate the present status is presented.
The Cutting Drain Method has been developed for digging underdrains without using lining material. The Cutting Drain Method includes a basic side-cavity method in which a tunnel is formed to the side of an excavation channel at a selected depth of 60 to 90 cm underground, and a supplementary method in which the tunnel is formed directly below the excavation channel. These methods are selected in accordance with soil conditions. The underground tunnels formed by the Cutting Drain Method function as drainage conduits, removing excess water from fields. The Cutting Drain Method can be used in peatlands, lowlands, tablelands, and mucklands . Requirements for application are that the soil is free of buried trees in the case of peatland, is free of rocks and stones, and has a sand content at depths of 50 to 90 cm of not more than 65%. With this method, drains can be constructed at a rate of 0.8 km h-1 (which is faster than underdrain digging with a trencher) and at the inexpensive construction cost of 72,000 yen ha-1 for construction of drains at 10 m intervals.
The model tests under lateral and combined load were conducted to verify the mechanical behavior on the rigid pile with multi-stepped two diameters. From the results of lateral load tests, the bearing capacity increases with the frontal projected area. For each pile, the lateral bearing capacity on the lateral load tests is smaller than the one on the combined load tests. Under combined load tests, the lateral soil pressure in MS-pile increases around the concave part to be push by vertical load. DEM analysis was also performed to evaluate the mechanical behavior under combined load. As the result of the DEM, the vertical loading before the lateral loading has the effect on the increase of the contact force between particles. Based on above test results, the ultimate lateral bearing capacity was calculated. Under combined loading tests, the calculation method involves three assumptions. The predicted values using the method are in close agreement with the measured values at about 4% of lateral displacement ratio.
In this study, a new method has been proposed that can reveal changes of wetland surface condition using high spatial resolution satellite data (IKONOS) for actual wetland managements. The method can detect the wetland surface change based on the NDVI change domain in wetlands using bi-temporal satellite data through analyzing ‘coordinate of NDVI change’. We applied the method to Kawaminami wetland in Miyazaki prefecture for comparing the calculation results and actual state of wetland with observed groundwater level data. As the results, it was able to extract artificial change of the wetland surface precisely and to detect differences of the wetness of the surface in two imageries. For satellite data analysis, it was indicated that utilization of supplementary climate data such as rainfall is important. The proposed method is effective for actual wetland managements, because it is simple and practical.
Paddy fields are widely distributed along Lake Kasumigaura. Agricultural drainage water directly flows into the lake through bank-based water canal. Both the discharged loads to the lake from paddy fields and the inflow loads from the lake by irrigation water were measured during irrigation period. In this district, some of drained water from the paddy is reused for irrigation by the cyclic irrigation system. As a result, about 57% of irrigation water was occupied by the reuse of drained water. Net effluent loadings of COD, T-N, and T-P were -25 kg·ha-1, -2.4 kg·ha-1, and -0.07 kg·ha-1, respectively. Inflow loads to the paddy from the lake were greater than outflow loads from the paddy to the lake. Cyclic irrigation water system much contributed to the reduction of effluent load to the lake.
Gathering paddy-reared juvenile fish (0-year fish) at the paddy's drain outlet at the time of the mid-summer drainage often results in many unharvested fish being left behind. To devise ways of reducing this wastage as much as possible, we performed two experiments during the irrigation season in modernized, consolidated paddy fields as follows. Experiment I: an investigation into the numbers of juvenile Carassius auratus grandoculis that succeeded in leaving a paddy field through the drain outlet. Experiment II: an investigation into their preferred route of escape from the paddy, either via the drain outlet or the water inlet, when both were available. In Experiment I, more than 39.1% of the number of fish that escaped from the paddy were still left behind in the paddy more than three days after the mid-summer drainage had begun. In Experiment II, most of the juveniles, i.e., 99.8% of the fish that escaped from the paddy, left from the water inlet. These results suggest that greater efficiency in reducing the numbers of unharvested juvenile fish in paddy culture may be achieved by first capturing fish at the drain outlet with the irrigation water shut off, and then partially refilling the paddy while using traps or other gear to catch the remaining fish that are attracted towards the water inlet.
The amounts of the outflow loads of nitrogen and phosphorus from the Kahokugata watersheds were estimated, and measures for the pollution load reduction were examined. Composite reservoir model was used to estimate the runoff discharge from watersheds. Parameter of the composite tank model was determined by the discharge and N and P observation data of Omiya river which was small one located in Kahokugata basin. Simulation results show the good fitting of the curve representing between observed and calculated discharge. Amounts of the outflow loads of total nitrogen(T-N) and total phosphorus(T-P) were estimated by using two methods, one was the pollutant load factors of paddy, upland, forest and urban area and the other method was L(load)and Q (discharge)relation method. Based upon the loading estimates from 1998 to 2002, Kahokugata basin received approximately 678 t year-1 of T-N and 92.2 t year-1 of T-P by former method and 661 t year-1 of T-N and 31 t year-1 by the latter method. It was clear that the land use of domestic, agriculture and forest contributed to the pollution. Moreover, about the total nitrogen loads, the load factor method and LQ equation method were compared on the forest watersheds and lowland areas. A high correlation was obtained between the both methods in the forest watersheds, but the result of lowland areas was not so good. As consideration, the effect of nitrogen pollutant reduction by repeating use of irrigation water at the forest watersheds was examined.
We determined the average exterior link length lex and the average interior link length lin for each studied rill network in sloping fields using survey maps of rill networks. We used the results to investigate the relationships between lex, lin and lin/lex and the number of sources of each rill network, as well as the relationships between lex and lin for each study rill network. Most of the average exterior and interior link lengths ranged from 2m to 5m for each rill network with n ≥29 sources, and lex was nearly equal to lin for each rill network with n ≥50 sources, except for a rill network with 89 sources. Furthermore, by using a magnitude theory of channel networks, we suggested two equations: one to predict the length of the mainstream of the rill network and another to predict the average total length of rill links in sub-basins with Strahler's stream orders in a rill network. These equations express statistical laws of topological structure of rill networks and contain parameters lex and lin . The validity of the equations was substantiated by the observed morphological data from the study rill networks.
In the present study, the formation situation and effects of physical and biochemical factors on formation of hypoxic water which has bad influence on the ecosystem and fishery in the interior parts of the Ariake Sea were investigated on the base of observation data and two-layer box model. Formation time rate of hypoxic water was high in the western parts with high COD and mud content. And hypoxic water was occurred and expanded at neap tide with the formation of density stratification. However, the expansions of its formation area were different every each time. Moreover, DO consumption rate in the bottom layer of the study area strongly influenced the formation or not of hypoxic water in consumption with the other physical and biochemical factors.
The effect of on sowing and before transplanting application of the phenyl pyrazole insecticide, fipronil, on the survivorship Sympetrum spp. was investigated in plots of an experimental rice paddy field. In addition, the effect of two pesticide applications on rice weevils was investigated. A total of nine paddy plots were used in this study: three were treated with fipronil at the before transplanting application , three at the on sowing application, and the three remaining plots were left untreated for use as controls. Fipronil concentrations in paddy water at the time of application in before transplanting and on sowing treatments reached 1.45 and 1.20 μg/L, respectively. A comparison of experimental and control plots revealed a marked absence of Sympetrum frequens larvae, exuviae and adults from fipronil-treated fields. Adult density of Sympetrum sp. and members of Lestidae in paddy fields before transplanting application were considerably lower than in control plots. Our results show that before transplanting application is more effective than on sowing application for treating rice weevils, but that on sowing application may still be harm against dragonflies.
In this study, we considered health and safety management for small-scale methane fermentation facilities that treat 2-5 ton of biomass daily based on several years operation experience with an approximate capacity of 5 t·d-1. We also took account of existing knowledge, related laws and regulations. There are no qualifications or licenses required for management and operation of small-scale methane fermentation facilities, even though rural sewerage facilities with a relative similar function are required to obtain a legitimate license. Therefore, there are wide variations in health and safety consciousness of the operators of small-scale methane fermentation facilities. The industrial safety and health laws are not applied to the operation of small-scale methane fermentation facilities. However, in order to safely operate a small-scale methane fermentation facility, the occupational safety and health management system that the law recommends should be applied. The aims of this paper are to clarify the risk factors in small-scale methane fermentation facilities and encourage planning, design and operation of facilities based on health and safety management.