The water management practice of paddy-field irrigation in Japan is said to have changed over the last 20-30 years, although the actual conditions of this change are not clear. In the present paper, therefore, the authors presented a gereral discussion on the basic trendof water use and its relationship to water requirement, as a basis for a series of studies on water demand in paddy field lots. First, the functions that water can perform in a field lot were outlined, from which it was clarified that the actual functions of water are suited for the development stage of other means of production. In this regard, the following two points emerged.
1) Static water management with all-season submergence was a dominant practice in previous times when cultivation techniques had not developed sufficiently. In those daysthe conditions of fields and the irrigation and drainage systems used had not been improved, and the working hours spent by farmers in water management were adequate.
2) Intensive management practice has spread according to changes in the conditions mentioned above. This has resulted in the use of submergence only in case of need, the fine control of ponding depth, intentional surface drainage whenever necessary and occasional flow-through.
In the traditional static management system, the water consumption in a lot is fundamentally determined by percolation and evapotranspiration phenomena which result from the natural conditions existing in a lot, so that, in this respect, the recognition of water demand aswater consumption in a field lot has been maintained. However, in recent forms of unstatic management, percolation and evapotranspiration have become influenced by the farmer's adoption of ponding periods and depth, so, that the spillage of irrigation water from the outlet (intentional surface drainage and spillage with flowthrough, usually called “lot management water requirement”) has grown. The authors therefore demonstrated that in this stage, the water consumption in a paddy field lot is determined as a result of water use, and that no direct relationship can be recognized between water demand and consumption.
Finally, it was clarified that lot management water requirement is representative of the recent changes which have occured in water management practice, and that the effect of rainfall on fields is influenced by this change, both quantitatively and qualitatively.

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Recently the additional water demand for paddy field irrigation, named the “lot management water requirement”, has been receiving attention in Japan. This comprises the runoff water from outlets, and is made up of the intended surface drainage and the spillage of furnished water. It can be thought of as another form of demand in addition to that for percolation and evapotranspiration, the net water requirement in fields. However, the actual state of its spread is still not clear.
Initially, in the present study, the circumstances in which the lot management water requirement was brought to the surface were briefly and generally outlined. Secondly, its actual mechanism and form was discussed mainly by close analysis of the records of water management and water budget ing in all 27 test field lots in Shiga prefecture. The results revealed the actual states existing as follows;
1) Paddy lots are kept submerged in the ifrst half of the growing season. In contrast, in the second half, intermittent irrigation without sumbmergence is widely spread, thus changing the rate and total quantity of percolation.
2) Intended surface drainage mainly breaks out just before transplanting and mid-summer drainage. It is established in correspondence with other cultivation techniques, and can be recognized as being representative of the recent intensive form of water management practice with the control of ponding depth.
3) Spillage with flow-through varies according to the lot, the year and the growing stage. It is determined by the water management practice of the farmer, and is influenced by intake rate, the shape and size of the lot, and by the irrigation system used.

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There are a bout 1, 500 earth dams for irrigation in Japan. It is important tomaintain their stability against earthquakes. Some problems about the dynamic behavior of earth dams still have yet to be unsettled. One of them is the three-dimensional dynamic behavior of earth dams.
This paper describes the results obtained from the experimental and the analytical approach regarding three-dimensional vibration of the dam body. A model of an earth dam was constructed, being scaled down from 250 m to 1 m. The model was made of silicon rubber, and with vibration tests being carried out using a shaking table. Three-dimensional eigenvalue analyses were performed on the above model.
These experiments and analyses showed that the vibration phenomenon of earth dams tended to concentrate in the upper half of middle area of the dam body. It was also found that the shape of the abutment influenced on the fundamental vibration mode of the dam body.

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Pasture fences are very important facilities for cattle grazing. In snowy areas, snow damage to such fences invariably occurs. Although structural and material problems with regard to these fences have been extensively investigated, the rusting and breakage of barbed wire remains one of the most troublesome maintenance problems for many farms.
This paper describes the relationship between the percentage of rust on samples of barbed wire taken from fence lines in 4 districts and their strength, and discusses the weight of zinc coating from the standpoint of the life of barbed wire.
The results of this study led to the following conclusions.
1. The barbed wire became increasingly rusty year by year and the diameter of the wire also increased in the upper wire of 4-wire fences in comparison with the lower one. The rust on the barbed wire had a tendancy to decrease as the weight of the zinc coating on the wire became greater.
2. Although the greater the thickness of rust on the wire, the smaller the tensile strength of the wire became, this effective strength persisted in spite of considerable rusting of wire exposed in pastures for 6 years.
3. The life of the barbed wire was discussed with regard to cost and minimum zinc coating weight. In the case of using barbed wire with a diameter of 2 mm, a wire-coating zinc weight above 122 g/m² was more durable and economical than a coating weight above 23g/m².

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Nitrogen outflow from a small agricultural area (165 ha) was measured by an automatic water sampler and automatic water table gauge during a six-month period in which the area was a not irrigated. Land use of this area is as follows: upland fields 33. 6%, forest 26. 9%, orchards 20. 2%, paddy fields 10. 2%(Table 1). About 1, 800 pigs are being intensively cared for in this area.
The concentration of NO₃-N in outflow water from this area is very high. Usually, the values are between 8-14 mg/l but it decreases to about 5 mg/l during storm flow after a heavy rainfall (Figs. 2, 4 and 5). Since the water discharge of storm water increases more than ten-fold, the nitrogen load also increases significantly. The coefficients of the correlation between the discharge, and load are more than 0.9 (Table 3 and Fig.10). Accordingly, we can estimate the values of load by the discharge data.
Average values of the nitrogen load from this area during the non-irrigation period are 15. 7 kg/d in 1983 and 4.8 kg/d in 1984. The specific of nitrogen load per unit area is 6. 2 kg/d·/km² in average.

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Recently, the control of nitrogen outflow has been required in order to prevent the pollution of water in a lake. In the small agricultural area concerned, therefore, the effect of return irrigation on flowing load was investigated. The discharge and NO3-N concentration of outflowing water were measured during the irrigation period. Irrigation water for paddy fields was supplied by pump as a returning system in which outflow water from this area was reused. Groundwater was also pumped up to supplement the irrigation water.
The water balance of this area is shown in Tables 1 (1983) and 2 (1984). In 1984, the volume of outflow water (Q₂) was 1723 m³/d, and that of returned irrigation water (J) was 534 m³/d (Fig. 4). Groundwater supply (W) was 1, 233 m³/d, which was larger than returned irrigation water. Fig. 5 also shows that groundwater supply (W) was always larger than returned irrigation water (J).
The NO₃-N concentrations of outflow water usually showed high values of more than 10 mg/l, but this decreased to about 2 mg/l during groundwater supply due to dilution as shown in Figs. 6-8. The average outflowing load of total nitrogen during the irrigation period in 1984 was 8.6kg/d and the nitrogen load contained in returned irrigation water was 1.1kg/d, or about 13% of the outflow load. This percentage was smaller than the value we expected. Excess supply of groundwater caused a large amount of water outflow and as a result of this inappropriate water management, the effect of returned irrigation on the control of nitrogen outflow became unsatisfactory.

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NO₃-N concentrations of waters in the main stream, it's tributaries, springs, groundwaters and surface flooding waters concerning paddy fields were measured (Table 1). Along the main stream, flowing load of NO₃-N increase in the zone of the downstream (Fig. 1). NO₃-N concentrations of the tributaries in the downstream show high values of 10-20 mg/l (Fig. 3). The concentrations of the shallow groundwater near the pig farm (L) are always exceedingly high, about 100 mg/l (Figs. 5 and 6). Contrary to this, the concentration of the groundwater underneath the forest (P) are very low (about 0.2mg/l), and that underneath the upland fields (I) are about 10 mg/l. The effect of pig farms on NO₃-N concentration of groundwater is large.
NO₃-N concentrations of groundwater underneath paddy fields are usually lower than that of stream water (Fig. 7). The concentrations of surface flooding water on the paddy fields are not uniform. Concentration near the inlet is high and it is low near the outlet (Fig. 8). Nitrogen concentrations of the surface flooding water gradually decrease with time due to the natural nitrogen removal of the paddy fields, mainly as a result of denitrification.
Flow diagram of nitrogen in this area is shown in Figs. 9 and 10. Outflow load of nitrogen from the upland part is estimated to be 25. 3 kg/d (17 kg/d·km²). Since the load flowing out of this area is measured to be 10.7 kg/d, the load decreased in the flow process through lowland area of the paddy fi elds. More than half of the nitrogen is removed from the paddy field area. This function of the paddy fields area can be considered as one of the important properties for controlling the nitrogen outflow from agricultural areas.

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This paper deals with an investigation of the mechanism of diurnal variation regarding the albedo of soils.
First, trial equipment for the albedo measurement can be made sure to fulfill its function precisely.
Second, it can be shown qualitatively that the physical and chemical properties of soil and the geometrical features of the soil's surface being composed of different size particles may be the main cause of the diurnal variation concerning albedo.
Finally, the mechanism of the diurnal variation regarding the albedo of the soil is examined, semitheoretically. The albedo of soil versus solar altitudes may be estimated by means of introducing both the hypothetical and analytical methods. Especially, soil particle models that make up the soil's surface may be proposed. Effects of the solar altitude on the models may be attributed mainly to the yield of both shade & shadow and sunny parts on the particles. The diurnal variation of the ratios of both shade & shadow and sunny area fractions to their unit area projected orthogonally to the soil's surface level may be calculated analytically. The estimated albedos may be put on the tendency of the diurnal variation of the measured albedo. On the other hand, it can be explained that the physical and chemical properties of soils might not have a direct influence on the albedo diurnal variation, but have a great influence on the production of great and small values for the variation, and the same thing might hold true for the ratio of direct incident radiation to diffuse radiation.

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On the hydraulic jump, mainly for the jump in sloping bed, the distributions of velocities and its standard deviations were measured using the micro-current meter and micro-program calculator. The following were found.
1. On the jump in flat bed, the relations between the height of maximum velocity's position at each cross section (δ) and the distance of each cross section from the beginning of jump (l) varied by the Fr number of incoming flow. For Fr≥4.52, δ grew rapidly for the water surface from the beginning of jump, and their variation coefficient near bed (σ/U) 0.3>0.4 (U: velocity, σ: standard deviation). For Fr=3.03, the increment of δ became moderate and (σ/U) _0.3=0.2-0.3, and then for Fr=1.75, (σ/U) _0.3=0.1-0.2 and δ grew very slowly. The δ-l relations at the case of Fr=1.75 in fl at bed and the cases of low Fr number jumps in sloping bed were similar to the turbulent boundary layer developments in smooth surface open channel.
The area of surface roller of jump became narrow at Fr=1.75, 4.52 and 6.02 and became wide at Fr=3.03.
The vertical velocity distribition in the jump followed the 1/7 power law at 0<z<3 and the law of free jet at z>δ, where Z is the height of position from bed.
2. The jumps in sloping bed were classified to 2 types according to the δ-l relations. The direct jump type, where, δ grows rapidly for water surface on the sloping bed, or where δ does not grow so largely on the sloping bed but grows rapidly on the flat bed, and the submerged jump type, where δ scarcely grows on the sloping bed and grows very slowly on the flat bed.
The direct jump type occured when the turbulence near bed became high, that is, in general the Fr number and D/d (D: the height of jump beginning station from flat bed, d: the depth of jump beginning station) were large provided the slope remained the same.
The submerged jump type occured at the contrary case.
The relations between the borders of Fr number, D/d of the both type and the slope were shown.
3. When the jump was the direct jump type, the vertical velocity distributions for 0<z<δ deviated from the 1/7 power law at the high turbulent stations but they followed the 1/7 power law at the low turbulent stations.
When the submerged type jump occured, the 1/7 power law was concluded perfectly.
For z>3 of the vertical velocity distribution, the same relation of free jet was concluded.
4. The U_m/U_o, U_0.3/U_o (Um: the maximum velocity of section, U_0.3: the velocity near bed of section, U₀: the mean velocity of the jump beginning station) were related to l/d. These relations were adjusted in the 2 groups of slopes 1/6.9-1/3 and slopes 1/10-1/20, flat bed. The U_m/U₀-l/d relations were settled on a single curve for each group having no relation to the slope, Fr, and the jump type.
The U_0.3/U₀-l/d relations were adjusted in the same manner.
The experimental equations were obtained.
5. The various states of jump from a flat bed jump to a sloping bed jump were caused by regulating the downstream flow stage only.
The scoring characteristics of flat bed were compared with each other. The tested slopes were 1/1, 1/5 and 1/6. 9.
The flow states of each jump had some specialities, for example, in the case of high jump beginning station of 1/1 slope, the partial adverse fllow area was found on the flat bed near the toe of slope.

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