To estimate effects of rice straw, charcoal and no fertilization field on outflow water quality from rice cultivation fields, effluent load was measured in rice cultivation fields. These three methods of treatment were set in front of the drainage outlet of the fields. So outflow water had to move through rice straw, charcoal or no fertilization field to the drainage canal.
No purification effect of rice straw was observed.
Charcoal absorbed ammonium to level off nitrogen concentration in some days after fertilization, but charcoal had no effect of removal in all irrigation period.
No fertilization field decreased nitrogen and phosphorus effluent load. COD was not removed. It was proposed that no fertilization field for purification should be used as environment conservation paddy field.

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In the previous paper, the results of an experimental study on the uplift capacity of short pile foundations were presented, so the windproof capacity of a vinyl might be improved. This study investigated the uplift capacity of the steel circular vertical earth anchor used as an anchor foundation in greenhouses.
Also, these tests investigated the mechanism of uplift capacity of an anchor and the displacement of sand ground surface during the uplift test in dry sand. In addition, in this paper we compared the ultimate uplift capacity of the anchor with that of the piles.
The diameter (B) of the model anchor is 120 mm. The model tests were performed for embedment ratios (L/B) ranging from 1-3 in either of two densities; medium or dense.
From these results, the following conclusions were obtained: As the embedment ratio increases, ultimate uplift capacity of the anchor increases quadratically, and yielding uplift capacity increases approximately linearly. According to the distance from the anchor center, the embedment ratio and the density, the earth pressure of earth pressure cells was different. The longer the distance from the anchor center is, the larger the earth pressure increases. Also, as time goes by in the experiment, each earth pressure is different from the change pattern according to L/B = 1, 2, 3 in medium sand. In dense sand, each earth pressure increases till the end of the experiment (pull-out). The points of contact of sand surface and failure envelope from the anchor center are, 15, 21 and 27 cm in medium sand and 16, 22 and 37 cm in dense sand respectively. The ultimate uplift capacity of the anchor is 4 6 times as large as that of piles (D 43, 66 and 83 mm) in medium sand.

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Rill initiation was studied in a laboratory flume, in order to clarify and establish an empirical relationship between critical flow, slope and particle diameters. The experiments were carried out under varying steady and uniform flow conditions at different slope degrees. Ten different samples of sandy soils were used. From the relationship of critical flow, slope and particle diameter, an equation was derived which can be expressed as q_c=a (sinθ) ^m. The derived regression equation shows that the effect of slope on critical flow for rill initiation is independent of particle diameter, because the exponent “m” is almost constant and nearly equal to-3/4 for all the samples. This suggests the possibility of the practical application of Manning's equation to the flow for rill initiation. The effect of particle diameter on the parameter “a” can best be explained by using the mean diameter d as a representative diameter. The derived empirical relationships can be used to predict critical flow for rill initiation for sandy soils, and can therefore contribute to the development of physically based erosion models.

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The aim of this paper is to look for the conditions in which the direct component of subsurface runoff discharge conforms to Manning's law. Relating to this aim, we expected that there are some conditions in which Manning's law will apply even if the subsurface has unit permeability. The index p corresponding to Manning's law is 0.6.
At first, at the lower end of the basin, it was ascertained that the value of p is in the range of 0.0-1.0, not taking into account the slope of the unpermeable soil layer. Next, by the numerical simulation of subsurface flow in uniform water permeability, the direct component of subsurface flow flowing like surface flow having constant value of p near by 0.6 after rainfall could be distinguished. The length of the area of this direct component was almost 10 m from the lower end of the field having 50 m length, and was narrowing with the passage of time. For the measuring area of reclaimed stepping field which can apply Manning's law empirically, the soil permeability of this area may not be unit and may become larger, closer to the surface.

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The objective of this study was to investigate the erosion mechanism of bottom muds from a viewpoint of the rheological properties. For the evaluation of erosion rate, the concentration of suspended solids in eroding water samples was measured. Additionally, the outflow of eutrophic components, such as total nitrogen and phosphorus, in the bottom muds erosion processes was evaluated using a concentric rotating cylinder apparatus.
This study made clear that bottom muds erosion affects largely the eutrophic components outflow. It was concluded that the nitrogen and phosphorus, in part, were not dissolved, but adsorbed by the suspended solids. The transport of suspended solids is an important factor for water environmental conservation.

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The recent water situation considered, it is necessary to place emphasis on saving water in water management as well as system such a drip irrigation. This study was conducted to develop and examine an irrigation scheduling to determine water requirement and irrigation timing simultaneously based on the data of crop transpiration in a green house condition. The heat pulse method on sap flow measurements was applied to obtain transpiration rate of sweet pepper in two experimental control and stress plots. The control plot was irrigated every one or two days to maintain unlimited soil water availability. Irrigation in stress plot was applied 1.2 times of total amount of transpiration after last irrigation when the transpiration rate was decreased to 80 % of the control one. The results indicated that total irrigation amount in stress plot was conserved 20 % of the control plot without yield loss and allow that water management in this study was available method for water saving. TDR technique was also examined to estimate water requirement under drip irrigation condition. Transpiration value was estimated by the soil moisture depletion in the root zone of sweet pepper and separate evaluation of evapotranspiration derived from a weighing lysimeter. The estimated. value was agreed well with measured transpiration rate by the heat pulse method.

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Resources consumption and environmental loading (eco-efficiency) of both High input type and Recycling type agriculture scenarios were preliminary examined, using Life Cycle Assessment (LCA) technique. The data collection and examination of life cycle energy and CO₂ emission at each stage, from the fertilizer production up to its use, were carried out to obtain the consumption and emission per unit nitrogen input for crop production.
Based on the results of the case study, it was found that the CO₂ emission rate of the Recycling type is 3, 373-4, 183kg·y^-1/ha lower than that of the High input type. On the other hand, quite different life cycle energy consumption levels for the Recycling type are found depending on the composting treatment methods employed. The life cycle energy varied from around 1.3GJ·y^-1/ha to around 12.8GJ·y^-1/ha, while the life cycle energy of the High input type which was estimated at around 2.7GJ·y^-1/ha. Thus, the study results suggest that careful examination should be conducted before the introduction of the Recycling type agriculture to increase the eon-efficiency as a objectives for the regional planning.

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The compression index C_c for undisturbed clays which is one of the mechanical properties of soils must be expressed as a function of three kinds of factors, which are type of soil, condition of soil and structure of soil.
Now by selecting plasticity index I_p, liquidity index I_L and sensitivity ratio S_t as representatives of these three factors and expressing the effect of contributions of both I_p and IL to C_c by the multiplication of I_p and I_L {I_p × I_L= (w₀-w_p)}, C_c can be expressed as
C_c=F {(w₀-w_p), S_t}
where w₀ and w_p are initial water content and water content at plastic limit, respectively.
The above mentioned function for C_c was examined in its applicability to undisturbed clays and the following C_c equation was obtained: C_c/S_t^0.22=0.009 (w₀-w_p) + 0.101 (regression coefficient, r=0.911).
Comparing the C_c equation shown above with the C_c' equation previously obtained for disturbed clays, the ratio, C_c/C_c' was expressed simply as a function of only S_t in the range of C_c > 0.4 as, C_c/C_c' = 1.25 S_t^0.22.

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Experiments to investigate the mechanism of fill initiation under non-uniform flow conditions were carried out in a pair of large flumes 10 m long and 1 m wide with artificial rainfall facilities. All the experiments were conducted under two different slopes of 5 and 10 degrees. The rainfall intensity ranged from 36 to 90 mm/h. The process of rill formation includes three stages: sheet erosion with water concentration into flow lines, microrilling and rill development. In this paper, the critical distance for rill initiation is defined as the distance from the top of the slope to the point where rill starts, and the surface discharge at the distance is defined as critical discharge for rill initiation. It was found that critical distance depends on rainfall intensity and slope, while the critical discharge is constant for each respective slope. Supposing that the overland flow is in the form of a thin sheet flow, it is considered that the critical velocity might be the same for both slopes, if the physical properties of the soil are kept constant. It appears that critical velocity may be an important external factor for rill initiation.

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Numerical simulations of water flow in a sloped soil model were conducted for two different soil materials, the sand tested by Vachaud & Thony and the Yolo light clay. First, the estimation of time to ponding (t_p) from numerical and pseudo-quasi-analytical solutions-were compared. t_p decays exponentially with rainfall intensity (R). When slope gradient (α) is larger than 30°, the slope soil has a distinguished different infiltrability from the flat.
Secondly, soil physical properties can influence greatly the lateral flow in sloped soils specially when R is a little larger than the sand's saturated hydraulic conductivity. In the sloped sand from its surface to the wetting front a saturated layer and a near saturated one could be discerned, which was not observed in the sloped clay.
In the third, slope gradient and rainfall intensity are two most important factors in determining the magnitude and refraction of water flux. The maximum refraction angle at the soil surface is linearly dependent on α, however, which is much less at high R than that at low R. Soil water refracts much more in the sand than that in the clay due to the sand's hydraulic conductivity.

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The condition of similarity of saturated-unsaturated flows with a free surface was theoretically proposed by the writer (1966) as follows: The relative hydraulic conductivity K_r (P) should be equal at the geometrically similar points in the unsaturated domain of both model and prototype (P is the water head of negative pressure). In the present paper, it is verified by computer simulation that the condition of similarity is satisfied by the relation K_r (P) =K_r'(λP), in which λ is the ratio of geometrical length between two flows.

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Residual current in Kii Channel in August 1996 was simulated by using a robust diagnostic numerical model. The computed results were verified by an Acoustic Doppler Current Profiler (ADCP) data obtained along the two observational lines.
The computed residual current is as follows. From the water surface to the depth of 30m, the water coming from Osaka Bay flows southward to the line of 34° N and veers to the west because of the existence of the counterclockwise eddy in the central part of Kii Channel. After the changing of its direction, the water flows southward along the Shikoku island. The water again changes its direction to the east off Man City and approaches the Kii Peninsula, then flows out to the Pacific Ocean along the Kii Peninsula. As a whole, the southward current is apparent in this layer. Below the depth of 50m, the northward current is dominant as a whole.
The forcing balances among the terms in momentum equation were investigated. The tidal stress balances with the pressure gradient around the strait. In other regions, the tidal stress is relatively small. Main balance is established between the pressure gradient force and the Coriolis force in Kii channel. Therefore the residual current in Kii Channel is supposed to be geostrophic.

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Frost heave occurs dueto ice formation which segregates soil structure. This ice formation is called ice lensing. The frost heave in soil is a complex solidification phenomenon which involves the movement of water and heat through unfrozen soil to the freezing front. Furthermore, soil complexity, such as non-uniformity of texture, particle shape and chemical composition and so on, makes difficult to clarify the ice lensing mechanism. In this study, we observed microscopic ice lensing in glass beads in stead of soil by thing an apparatus which can control temperature gradient and freezing velocity separately. As a result, we found that artificial ice lenses were formedin the glass beads as well as soil and that thickness of the ice lenses depended on freezing velocity. In addition, we observed the criteria for exclusion and inclusion of glass particles during ice formation depended on both particle size and freezing velocity. These results suggest that particle size and freezing velocity play an important role in ice lensing.

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Signification and problems of Agricultural Infrastructute Improvement and Rural Development Projects in case of an upland field have been studied, using Regional Energies Levels unveiled by Foundation of Long-term Finance for Agriculture, Forestry and Fisheries, and using enlarged analysis.
This study has revealed that Agricultural Energies which are one of principal ingredients of Regional Energies Levels is useful as a method of evaluating Effect of Project, and that specifically implementation of irrigation facilities and land readjustment have effect on strengthening Regional Energies Levels to some extent.
It has also revealed that effect of projects would reach a fixed limit without intentional and integrated implemen tation of projects, and that intentional implementation of projects based on clarification of land use planning is more important than ever, considering Economic Energies and a social economic condition.

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Diurnal soil temperature fluctuation, water content and soil water potential profiles, evaporation rate, and radiation were measured in a bare field in Tsukuba, to investigate the wet and dry effects of surface soil on soil temperature. When a dry soil layer appeared at surface, the surface temperature amplitude increased significantly, but the amplitude in the wet layer beneath the dry layer was similar to that without the dry layer. The reasons were found that the dry layer has high resistance to heat flow, and the location of heat sink due to latent heat of evaporation shifts down to the bottom of the dry layer, while evaporation rate is reduced by the dry layer. Measured relative humidity profile in the soil showed that evaporation rate is restricted by vapor diffusion in the dry layer.

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Water quality of seven irrigation ponds was investigated in Kyotanabe city of Kyoto Prefecture. The ponds were classified into three types by catchment land use;(1) Forest Type, which has forest as a catchment, (2) Farmland Type, which uses farmlands, and (3) Urban Type, which collects discharges from urban areas.
The average concentrations of T-N, T-P and COD were low in the forest and farmland types. The concentrations changed little in the forest type. In the farmland type, peaks of concentrations were observed in the early irrigation period. The concentrations of inorganic nitrogen and inorganic phosphorus were higher in the irrigation period than in the non-irrigation period.
Characteristics of water quality in irrigation ponds were extracted using Principal Component Analysis, which dealt with five water quality parameters (pH, EC, T-N, T-P and COD) at study ponds and 47 ponds in Kyoto, Shiga and Nara Prefectures. The amount of organic matters was proportional to total solids in the forest and the farmland types, and in a part of the urban types. Other ponds tended to have high ratio of their command areas to water storage capacity.

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An experimental paddy field (370 m²) was irrigated with the effluent of a rural sewage treatment plant (328 m³/d) for 7 years, and the concentrations of hazardous metals in the rice plant, percolating water and surface soil as well as the growth and yield of rice were compared with those obtained from a neighboring paddy field (325 m²) irrigated with the water of an irrigation canal. The total volume of the irrigated effluent was strongly affected by rainfall during a growing season, and ranged from 172 to 849 mm/y, with the mean value of 415 mm/y. The mean concentrations of total-N, NH₄-N, NO₃-N, total-P and K⁺ in the effluent for 7 years were 14.4, 2.04, 9.25, 1.86 and 8.1 mg/l, respectively. Those of total-N and total-P in the percolating water of the control field were 0.49 and 0.038 mg/l, respectively, whereas those of the field irrigated with the effluent were 0.52 and 0.029 mg/l in the last 7th year. The mean supplies of total-N and total-P from the irrigated effluent were 61.8 and 7.89 kg/ha per crop, respectively, and increased the percolating losses by 2.0 and 0.22 kg/ha·y in comparison with those from the control field. The concentrations of Cd, Hg, Cu, Zn, Pb and As in the harvested rice grains, leaves and stems, surface soil (ca. 10 cm), and percolating water did not differ between the effluent-irrigated and the control field. No increasing trends were observed in the metal and nitrate concentrations of the percolating water as well as the soils for these 7 years. The mean yields of the rice grain harvested from the effluent-treated and the control field were 5, 950 and 5, 770 kg/ha per crop, respectively.

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Actual farming water requirement at upland fields in Southern Kyushu was investigated, and clarified that it had developed characteristically by reflecting climate conditions and cropping pattern of this region. In this report, farming water requirement includes not only multipurpose water requirement, but also such farming water supply as harvested crop washing and agricultural facility management. Investigated results of this research were summarized as follows;
1. Farming water requirements were limited such a few crops as tea, radish, taro and some crops grown in greenhouse in spite of that there were lots of irrigated crops especially for vegetables.
2. Farming water requirement was much different among districts, and reflected cropped area ratio where such supplemental water requirements were relatively large, as frost protection for tea and soil moisture supply for greenhouse.
3. Farming water requirement per unit area of orchard was the largest. Most of it was the water requirement for protecting frost damage for tea field. On the other hand, water requirement at greenhouse had almost limited for overcome the shortage of soil moisture. In other field use fdrms, various kinds of farming water requirement had spread widely though the quantity of water was small.
4. Water requirements for soil moisture management, such as supplemental water requirement, seeding water requirement, exceeded any other purposes in number of use, quantity of water used and irrigated area.
5. There were such irrigation methods applied in this region as intermediate pressure sprinkler, giant type sprinkler, perforated pipe, drip method, hydrant and power sprayer. Intermediate pressure sprinkler was mainly employed among them. It was used not only soil moisture management but also many other farm management.

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The accuracy of a survey using the Differential GPS method (DGPS) was evaluated by site tests. The receiving condition of GPS signals was not good and the accuracy of the survey dropped or sometimes measurements became impossible under tree branches. Survey test using DGPS at eight national triangulation stations showed an error of 0.5 m or less in the horizontal direction and 1.6 m or less in the altitude from the official position of the stations. The standard deviation of the measured position was estimated as decreasing below more than half by collecting data for 3 min. or more and taking the average of DGPS data. A change in the position and altitude of the survey station occurred to the same degree, and the direction as the offset value added to the position or the altitude of the reference station used for position correction. The exact position of the reference station is necessary to obtain the position of survey stations at an unknown site with accuracy based on the geodetic coordinates system. DGPS is easy to operate and has sufficient accuracy for mapping of the results of field surveys.

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Drop structures are constructed for the reduction of the ground slope in open channel which slope is steep. Stilling basins are designed for the energy dissipation in the downstream of drop structures. In many cases, a large fluctuation of water surface frequently occurs in the downstream flumes of stilling basins. Those surface fluctuation are also observed in the Main Canal in Isawa plain area, Iwate Prefecture. The height of surface wave occurred at the end of the stilling basin is about 0.5m with average water depth 1.7m, when maximum design flow discharge 16m³/s flows. And, wave amplitude range become smaller as flow discharge diminishes.
Similar phenomenon in a smaller size flume, whose width and water depth are about half of the Main Canal, is also surveyed. The ranges of surface fluctuation in a half-size flume are about half compared with those in the Main Canal.

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[in Japanese]

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