In microirrigation systems the emitter clogging can adversely affect the uniformity in irrigation water application, thereby increasing irrigation requirement, and decreasing the irrigation water use efficiency. We investigated the impact of selected water quality attributes (chemical) and the duration of the irrigation system in use (long and short period) on (i) emitter clogging and (ii) uniformity of water distribution in microirrigation systems. Field experiments were conducted in eleven farms, equipped with microirrigation system, in Rafsanjan and Jahrom sub-provinces in Southeast Iran. In Rafsanjan, the emitter clogging was induced primarily by calcium carbonate content in irrigation water and to a lesser extent by calcium sulfate. On the other hand, an opposite trends was observed in the Jahrom irrigation system. In general, clogging in Jahrom irrigation systems was higher than in Rafsanjan. The pH of the irrigation water used in Rafsanjan irrigation systems was higher than that in Jahrom. The field performance index “coefficient of emitter discharge variation (W_q1) ” seems to be more sensitive and reliable, for assessing clogging severity, than uniformity coefficient (U_c) or emission uniformity coefficient (E_u). Emission uniformity coefficient in the irrigation systems in operation for short period was higher, E_u>80%, than those in operation for long period, E_u<66%.

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The purpose of this paper is to describe an elastoplastic model for unsaturated soils. In the formulation of elastoplastic model for unsaturated soils, it is necessary to consider two suction effects. Authors have already proposed some models for unsaturated soils. Though these models are suitable to express unsaturated behavior for clayey soils, they are not to express that of sandy and silty soils. The models were here is modified to express unsaturated behavior of clayey, sandy and silty soils. The modification is accomplished by modeling state surfaces whose shapes depend on the type of soils. The model was formulated on the basis of cyclic plasticity. The verification of the model was done simulating triaxial compression tests for some soils. The simulation results showed good agreements to the experimental ones.

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One of the effective rural plans requires to promote the project for villages by producing high value added crops. In this paper, rain shelter greenhouses growing high value added tomato were selected in a superior active village. The locations of them were analyzed from the viewpoints of settlement form and field conditions, which set a limit on the production of crops. As results, rain shelter greenhouses were almost fixedly located on the consolidated paddy lots near the each landowner's residence which were scattered. They were built up along short side of a lot getting efficient sunshine, ventilation and workability. The fields were well irrigated and had a good drained subsoil containing gravels. A high value added crop production in this village after Japanese rice overproduction policy was found to be supported by many farmers' efforts of crop selection and extension. Promoting a high value added type of agriculture requires not only good physical and physiological field conditions but also settlement form enable intensive cultivation. Moreover, drainage system should be improved against increasing storm runoff caused by the rain shelter greenhouses.

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Many practical problems are involved with the consolidation of earth structures, such as embankment dams, which are built of compacted partially saturated soils. The air in partially saturated soil is found in occluded state and the pore space is assumed to be filled with an equivalent fluid with compressibility equal to that of air-water mixture. An extension of Biot's theory of consolidation that makes possible finite element analysis of the consolidation of elastic-plastic, partially saturated soil masses is presented. The influence of partial saturation on pore pressures developed during construction of embankment dams is investigated using the proposed partially saturated model.
The analysis of construction pore pressure of a hypothetical and an existing dam was undertaken using the proposed model, and the result of the analysis is compared with previous studies and with field measurements. The model reveals that the partial saturation of soil reduces the pore pressure developed and shows more settlement during construction, and it predicts a result closer to the measured field values than that of a saturated soil model.

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On the base of the equation of continuity for pore water using Lagrangian coordinate and nominal strain, the linear equation governing primary consolidation is derived using effective stress as the dpendent variable. The analytical solution of this Lagrangian linear formulation is exactly obtained under the fixed boundary. The reason why this analytical solution agrees with the solution of Terzaghi's formulation is that Terzaghi's Eulerian formu-lation is incorrectly derived as a linear equation and is incorrectly in addition solved under the fixed boundary to result in solving the exact formulation of this paper. It is also clarified that Mikasa's Eulerian formulation using the logarithmic strain is incorrectly solved under the fixed boundary to result in producing various contradictions in the method of arrangement of data. The method to simultaneously obtain a set of the coefficient of volume compressibility and the coefficient of consolidation by curve-fitting is proposed using degree of consolidationtime factor curve. Furthermore, it is clarified that the primary consolidation is determined by the two parameters.

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Angling pressure to fishes (O.masou, Sieucomaenis) in the mountainous strearn was studied using CPUE (Catch Per Unit Effort) based on 12 times survey. CPUE was calculated as the whole total length per one hour and as a number of capture per one hour. The study area, 1.6km-length, was divided into the 19 units. The ratio of the water surface area became lower in order of fast rapids, flat riffle, step and pool. The average density of the point, which a angler throws worms into with fishing rod, of flat riffle was 2-3 times higher than other river forms. In pool, it was lowest values. In the seasonal variation of CPUE, any river form was low in summer where the water temperature rose to 15 degrees or more. The CPUE became higher in spring and autumn. Average CPUE in the whole investigations showed low value 25cm/h at the flat riffle and high result 97cm/h at pool. Fast rapid and pool were accounted for about 80% in the number and the amount of total capture. And especially highest pressure was brought to fish of the average type (16-20cm). As for flat riffle and step, the tendency with a high pressure to a small type of fish (16cm or less) was analyzed compared with pool and fast rapids. As mentioned above, the feature of angling pressure to fishes and the point in each river form became clear. Therefore, some important findings will be useful for making a countermeasure plan to angling pressure in the mountainous stream.

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The ascending route and swimming speed of the fish and the flow characteristics at the wall were demonstratively carried out examine in the ice-harbor type fishway (width=2.6 m. drop=0.15 m. slope=1: 20. length=3.0m) of Akaishi the number 2 headworks on the Akaishi River in Aomori Prefecture. It was found that the swimming fishes almost uniformly swum up in the inside of the overflow. and swum up along in sidewall division which the velocity was about 140cm/s on the notches. On the other hand. it was found that the fishes swum through in the each basal plane corner part in the orifices. And the relationship between the passage swimming speed of the fishes guessed thatthey are Plecoglossus altivelis (Ayu) and Tribolodon hakonensis (Ugui) and the body length was shown. and it was found that the swimming velocity of every body length is about 190cm/s-250cm/s (3cm≤body length≤16cm) on the notches.

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Recently in Okinawa, red soil runoff becomes a remarkable problem, and its prediction models are demanded. In this study, a purpose is a construction of the models which can calculate a time series of suspended sediment concentration using rainfall data. First, the LQ equation is often applied in basin scale suspended sediment runoff analysis. The equation has been improved to express some sediment runoff characteristics which can not be expressed by the LQ equation. As results of the application of the improved LQ equation, it was confirmed that every improvements were effective for the representation of each characteristic. Next, the suspended sediment runoff model was constructed including the improvements above. A rainfall-runoff process was based on the storage-typed runoff model which can separate direct and base flow. A sediment runoff process was composed of the detachment process of soil particles by raindrops and the storage process of detached soil particles. This model was applied in Yakashimoguchi river basin for 2 months. It was recognized that the model represented a time series of suspended sediment concentration accurately.

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A theory of consolidation including the secondary consolidation based on peds model is proposed. This theory is based on the following assumptions;(1) The soil structure is assumed to be composed of the assemblage of peds. Accordingly, it is assumed that the first consolidation is compression of macro pores between peds by effective stress not between soil particles but between peds and the secondary consolidation, of micro pores within peds by applying of increasing effective stress between peds.(2) The peds are assumed to be linear elastic bodies. The consolidation behavior of peds is described by a function that is analogous to Terzaghi's consolidation degree function of time factor.
The governing equation with respect to effective stress between peds is derived and solved by means of the Laplace transform. As a check on the reliability of the solution, the settlements measured in the standard tests are compared with those predicted by the theory. Good agreement can be observed to 20 or 40 in time factor.

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The purpose of this research is to clarify the role of air in the formation of pore structure of compacted volcanic ash soil. The soil was compacted in a vacuum and under atmospheric pressure, respectively using special equipment we developed. Permeability of each compacted soil was measured and then pore structure was observed by x-ray stereo-radiography. The dry bulk density of the specimens compacted in a vacuum (SCV) were higher than those compacted under atmospheric pressure (SCA). The permeability of SVCs was 1/6-1/7 times lower than that of SCVs. Thus it was proved that air behaves as an obstruction to soil compaction. Horizontally well developed membranous macropores were observed in a partially saturated SCA compacted at field water content. However, they were not found in completely saturated SCA but faint pores surrounding the cluster of soil aggregates were observed. This suggests that kind of macropores permeated by contrast medium changes by the degree of saturation. Any membranous macropore was not found in SCV compacted at the field water content. It was concluded that air contributes to the formation of membranous macropores. It seems that membranous macropores were formed by the horizontal spreading of entrapped air under vertical compression of the compaction effort.

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The caves in Ryukyu limestone which are estimated from boring data in Komes groundwater basin, southern part of Okinawa island, are distributed within 500 m in distance from sea shore and in range of 10 m--50 m in altitude. Palaeo-gradients of shallow groundwater tables, which are presumed from linear arrangements of caves in direction from sea shore to inland show 1/20→1/40→1/60→1/70 in ascending order. The palaeo-gradients have gentler slope toward upper level. However, the palaeo-gradients are too steep compared with recent groundwater gradient around sea shore that has a gradient of 1/300-1/500. The continuous tilting of basement may be caused the steep palaeo-gradient of groundwater. The construction ages of cave estimated from palaeo-sea level corrected tilting and sea level curve are presumed as follows: minimum level:-45m, 9800-8300 years B.C.;-31m, 7600 year B.C.;-15m, 5800 years B.C.;-2m, 4300 years B.C.; +4m, 2800 years B.C. in ascending order. Permeability of Ryukyu limestone estimated from a relationship between distance from seashore and amplitude of groundwater table is 0.0006m/s. Permeability estimated from a delay time of phase difference of groundwater from tide level is 0.008 m/s. The reason for higher permeability estimated from delay time from tide level is considered that the permeability may be an apparent permeability, because a phase difference of groundwater table from tide level is caused by a propagation of tide pressure without movement of groundwater flow.

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In our country, paddy fields have been irrigated by irrigation ponds since ancient times. There are irrigation ponds with beneficiary areas of 2 hectares or more at about 69, 000 locations. Irrigation ponds not only contribute to the stable supply of food as sources of irrigation water, but because they are often located upstream from paddy fields, upland fields, and residential land, they help reduce flooding of the downstream regions by temporarily storing flood waters discharged as rain water or from catchment areas. This paper describes a study conducted to macroscopically evaluate the potential rainwater storage capacity that can be obtained by creating capacity in irrigation ponds by using their water for irrigation purposes as an index to evaluate their flood prevention function with the Kagawa prefecture and Osaka prefecture areas selected as the study area. The results have clearly shown that in a normal year, the potential rainfall storage capacity of irrigation ponds in early September in the study region reaches about 2.1 times and 1.2 times the rain water storage capacity of the paddy fields in Kagawa prefecture and Osaka prefecture respectively.

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Uncultivated farmland in suburban areas has been considered the intermediate stage of farmland's transition to urban land use. This research examined changes in land use in two farming communities in the Nishi Ward of the city of Kobe, Japan, from 1986 to 2000. One community was part of an Urbanization Promotion Area, and the other was part of an Urbanization Control Area. The study confirmed the following facts:
It was not always the case that uncultivated farmland was converted to urban use. There were cases in which uncultivated farmland again became used as farmland, as well as case of sustained stop cultivating.
Two factors were identified as determinants of the future of a tract of uncultivated farmland. They were its distance from the farmer's house and whether or not the uncultivated farmland faced a road.
In conclusion, land consolidation was needed to solve the problem of uncultivated farmland not being converted to urban land use or not being reused as farmland.

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To obtain acuurate estimation of flow transmissibility of rockfill structures, a nonlinear relationship between a hydraulic gradient and a discharge velocity of flow should be well described. Author had already developed a head loss equation of flow based on a laboratory one-dimensional permeability test of river gravel. A hydraulic mean radius of void had been effectively introduced into the head loss equation of flow to take account of an effect of rock particle size, shape and rockfill void on the hydraulic property of flow through the structure. Fifteen laboratory embankment tests using river gravel were conducted in a laboratory water flume to examine accuracy of the head loss equation of flow developed. Results of the laboratory embankment tests were tabulated, and analyzed by using a nonlinear FEM. Good comparisons of the discharge velocity, the position of free surface and the total head of flow between the measurement in the laboratory embankment test and the FEM calculation showed effectiveness as well as accuracy of the head loss equation of flow developed. Since relatively small particle size of rockfill was used in the laboratory one-dimensional permeability tests and the laboratory embankment tests, it's should be examined whether the head loss equation of flow proposed can be effectively applied to the larger rockfill.

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