Biomass fuels produce about 400 million tonnes of ashes as waste material. This paper discusses the pozzolanic character of bio-waste ashes obtained from dry tree leaves (AML), Korai grass (KRI) and Tifton grass (TFT). Ashes were obtained by control incineration of the wastes at 600°C for 5 hours and mortar specimens were prepared by substituting cement with 10, 20 and 30% ash. Strength development of ash-blended mortar specimens was evaluated by conducting destructive tests as well as non-destructive tests till 91 days. X-ray diffraction, scanning electron microscopic and thermo-gravimetric techniques were used to analyze the influence of ash substitution on strength properties of blended-mortar. Pozzolanic reactivity of AML- and KRI-ash was confirmed, but TFT-ash did not show enough reactivity. Overall results confirmed that up to 20% substitution of cement can be made with AML- or KRI-ash with strength approaching 90% of that of control.

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Sugarcane bagasse ash (SCBA), a sugar-mill waste, has the potential of a partial cement replacement material if processed and obtained under controlled conditions. This paper discusses the reactivity of SCBA obtained by control burning of sugarcane bagasse procured from Punjab province of India. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were employed to ascertain the amorphousness and morphology of the minerals ash particles. Destructive and non-destructive tests were conducted on SCBA-blended mortar specimens. Ash-blended cement paste specimens were analyzed by XRD, thermal analysis, and SEM methods to evaluate the hydration reaction of SCBA with cement. Results showed that the SCBA processed at 600°C for 5 hours was reactive as ash-blended mortar specimens with up to 15% substitution of cement gave better strength than control specimens.

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Using repeated sequences of microsatellite DNA, we investigated genetic variation and spatial structure of the loach Misgurnus anguillicaudatus population in drainage canals including a main stream in the Shitada River basin composed of Yatsu paddy fields, Chiba Prefecture. Loach population samples of nine to 48 individuals were collected from 54 sampling sites in eight canals and the main stream, and genotype data in eight microsatellite loci were obtained for each sample in the genetic analysis. The average number of alleles per locus was 3.9 to 9.0, and the average observed and expected heterozygosities were 0.444-0.647 and 0.463-0.628, respectively, across samples. All samples seemed to be random mating, which conformed to the Hardy-Weinberg equilibrium. Values of the fixation index F_ST, were estimated to range between 0-0.161 among all samples, and a part of these values were significant. The pattern of genetic differentiation between samples with principal component analysis indicated that samples in three distinct canals appeared to differentiate, suggesting that the genetic spatial structure of the loach population in Yatsu paddy fields must be complex.

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Since 2002, Kamihayashi district in Niigata prefecture has been undertaking flood mitigation measures using paddy fields by installing runoff control devices in drainage pits. The purpose of this study is to quantitatively evaluate the effect of this runoff control device on runoff detention at the paddy field scale. The factors controlling the rate of surface water drainage from a paddy field during ponding season are the width of the drainage outlet (rectangular weir) and the diameter of the drainage hole on the floor of the drainage pit (orifice). On the other hand, during midsummer drainage season, the surface of the paddy field is furrowed for promoting quick drainage. Calculation of runoff rate with and without runoff control devices is conducted using the formulae of rectangular weir and orifice in the case of ponding season, and an orifice formula incorporated in tank model for midsummer drainage season. The result shows that the peak discharge from a paddy field plot decreases by 48% for ponding paddy field and 55% for midsummer drainage paddy field with an observed rainfall event (daily precipitation of 101.8mm), and 73% and 71% respectively with a 50-year return period rainfall.

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Since 2002, Kamihayashi district in Niigata prefecture has been undertaking flood mitigation measures using paddy fields by installing runoff control devices in drainage pits. The purpose of this study is to evaluate the flood mitigation performance of a paddy field with runoff control devices by using combined hydrologic analyses and flood routing. The model constructed for runoff analysis is composed of the following three modules; mountain-urban module where the overland flow was estimated by the Kinematic Wave method, paddy field module where runoff from paddy fields was calculated by water balance analysis, and river/canal module where flood routing was performed by the one-dimensional unsteady flow model. The output of the first two modules represents the input of the third module. The result of the simulation shows that the main river and canal discharge would be decreased by 25% to 29% and water level would be lowered by 0.17 to 0.23m in the case of all the paddy fields being installed with runoff control devices. From these outcomes, it is confirmed that the runoff control measure in the study area is functioning effectively.

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Runoff characteristics of nitrate nitrogen (NO₃-N) concentrations of drainage water were investigated in Yatsu agricultural catchment during rainfall events. With regard to the changes in the NO₃-N concentrations for each rainfall event, the NO₃-N concentrations showed a decreased tendency according to the increases in runoff by rainfall. When the runoff and the NO₃-N concentrations for rainfall events during the irrigation or non-irrigation periods were plotted in a scattered diagram, they were significantly related to each other using a power function. The NO₃-N concentrations during the irrigation period were below those at the similar runoff during the non-irrigation period, suggesting that irrigation water and a nitrogen removal function of paddy fields affected the No₃-N concentrations during rainfall events. In special, the direct runoff was strongly related to the No₃-N concentrations. In addition, the NO₃-N concentrations decreased when the antecedent rainfall during the 5 days preceding the rainfall event (pre-5-day rainfall) was great, indicating that the pre-5-day rainfall affected the changes in the NO₃-N concentrations. The results suggested that irrigation water, direct runoff, and antecedent rainfall affected the NO₃-N concentrations of drainage water during rainfall events.

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We investigated the growth and the yields and the cadmium concentrations of rice plants by using two models of stratified paddy fields during three years. The first model had water flow in an open system under the plow layer and the plowsole and the subsoil became oxidation layers. The other model had water flow in a closed system under the plow layer and the plowsole and the subsoil became reduction layers. The plow layer and the plowsole in those models were made of polluted soil (3.39mg/kg) that existed in polluted paddy field.
As a result, the range of cadmium concentration in both models in brown rice, stems and leaves was 0.001-0.200mg/kg, 0.06-1.25mg/kg, respectively. Also the one in roots in the plow layers and that in the ones in the plowsoles were 6.62-25.05mg/kg, 9.85-61.63mg/kg, respectively. Cadmium concentration in every item with water flow in an open system became higher than that with water flow in a closed system. We realized that percolation patterns did not influence the growth of rice plants But the number of panicles, the total weight of straw and the weight of the brown rice with water flow in the closed system became higher than those with the water flow in the open system.
From these results, it became clear that the percolation patterns influenced the concentration of cadmium in the rice plants and the yields under inundation during the cultivation.

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The effect of salt concentration on the visco-elastic properties of a montmorillonite suspension was clarified by applying the Maxwell model to the measured flow curves. Based on the sheet-like shape and measured size of montmorillonite, the suspended particles at a 1.1×10^-2 volume concentration (experimental condition) were found to orient in the same direction. In this configuration of the particles, the repulsive force was calculated from the balk salt concentration on the basis of the two flat-plates model. The relative repulsive force at various salt concentrations was defined as the increasing ratio of this force to the force at critical coagulation concentration (C. C. C). The effect of the relative repulsive force computed from the salt concentration on the visco-elastic properties (such as viscosity, elastic modulus and relaxation time) was examined and it was found that the fluidity decreases and the solidity increases almost linearly with the increase in the repulsive force.

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Swimming experiments were conducted on wild fishes in a natural guidance system stamina tunnel (cylindrical pipe) installed in a fishway of a local river under high-velocity flow conditions (tunnel flow velocity : 211 to 279 cm·s^-1). In this study, the swimming characteristics of fishes were observed. The results show that (1) the swimming speeds of Tribolodon hakonensis (Japanese dace), Phoxinus lagowshi steindachneri (Japanese fat-minnow), Plecoglossus altivelis (Ayu), and Zacco platypus (Pale chub) were in proportion to their body length under identical water flow velocity conditions; (2) the maximum burst speed of Japanese dace and Japanese fat-minnow (measuring 4 to 6 cm in length) was 262 to 319 cm·s^-1 under high flow velocity conditions (225 to 230 cm·s^-1), while the maximum burst speed of Ayu and Pale chub (measuring 5 cm to 12 cm in length) was 308 to 355 cm·s^-1 under high flow velocity conditions (264 to 273 cm·s^-1) ; (3) the 50cm-maximum swimming speed of swimming fishes was 1.07 times faster than the pipe-swimming speed; (4) the faster the flow velocity, the shorter the swimming distance became.

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Fish immigration and migration to early-planted paddy fields was investigated in Kaminanami-cho, in Matsusaka-city, Mie prefecture. Fish immigrated to paddy fields in the upper area through water inlets during the intake of water and they spawned eggs. Since it is rare that water is taken into paddy fields in the lower area, fish immigrated to there through water outlets when water from the drainage channel overflowed due to rainfall. Paddy fields in the lower area functioned as breeding and refuge areas. Oryzias latipes immigrated to paddy fields in the middle of April just after rice planting, and Misgurnus anguillicaudatus immigrated in May. The standard length of M. anguillicaudatus fries that emigrated from paddy fields to irrigation channels during mid-summer drainage in Kaminanami was significantly smaller than those in Kunitachi-city, Tokyo where rice is planted in early June. The small standard length of former may be attributed to a low water temperature; short term to be able to grow in paddy fields until mid-summer drainage. If accelerated cropping season make negative effect on fish spawning and growth, it will be more important to conserve spawning and growth areas in irrigation channels.

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