Analysis of snow-melt mechanizm and discharge system is important, because snow-melt is the most important resource for supplying water for irrigation purposes in Hokkaido. The present paper addresses the observed data of snow-depth, snow-density, snow-melt, discharge amounts, radiation amounts and temperature in dry fields in the upland area. Using the data, this paper discusses the model of hourly snow-melt due to radiation and convection of warm air and hourly discharge.
The main results obtained herein are as follows:
1) Time of peak of hourly snow-melt observed under the snow deposit delays several hours are compared with the time estimated to the peak of snow-melt on the surface of snow deposit. The delay time is long in proportion to the snow depth.
2) Using the runoff distribution function built in the concentration time that is be reformabl depending on the snow depth, it is cleared that the calculated time-series of the discharge under the snow deposit was in good agreement with the observed data.
3) The reservoir-model can be applied in the estimation of interflow after a previous snow-melt and discharge process.
4) The simple model of snow-melt applied with hourly air temperature and hourly radiation data was in good agreement with the estimation model. The method was also explained to estimate the hourly radiation data from the time of sunshine. It was finally proven that the model of snow-melt and discharge used with the estimated hourly radiation coincied with the observed results.

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There are a lot of farm fields that have no water supply facilities, since they are located in the highlands. From the point of land conservation, the design and plan of reclaimed dry fields have a drainage system (catch ditch, drain ditch, lateral canal) that accelerates discharge. Using these systems, it seems good to intercept the interflow, concentrate them in a small store pond and use them for irrigation use. In this paper, we have considered the distribution of precipitation during the cold season that seems to be available for irrigation and observed the interflow amounts of reclaimed dry fields from the snowmelt season to irrigation period, and we estimated the available amount of irrigation use.
With consideration given to irrigation use and this availability, the following results could be induced.
1) In highlands of Hokkaido, the snowfall amount is abundant and occupies from 20% to 30% of the annual precipitation. It seems useful as a water resource for irrigation use.
2) The interflow amount was about 50% of the snowmelt amount for reclaimed dry fields constructed in a clayey soil area.
3) The discharge ratio of interflow is little in irrigation period and the occurence probability of heavy rain that produces the large interflow amount is negliable. Due to these reasons, it was judged that the interflow amount of snowmelt was available. After making a comparison between the available amount and irrigation use, it was found that the interflow amount was able to supply 30% of the water demand.
4) The technology that stores the interflow in small pond located near farm field is effective as an alternative plan for dam and or the like.

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We have carried out experiments on the use of “Masa-do” as a fine aggregate for concrete since 1981. The term “Masa-do” is applied to the residual soil derived from the weathered granite or decomposed granite in Japan. From these experiments, it was shown that “Masa-do” can be used as a fine aggregate for concrete.
In this paper, experimental studies on the resistance of concrete made with “Masa-do” as a fine aggregate to freezing and thawing are discussed. After curing in water at 20°C for 14 or 28 days, the concrete was exposed to freezing and thawing in the laboratory. The type of exposure is rapid freezing in air and thawing in water. The test piece is a prism with 10 cm square and 40 cm long.
Weight, volume, bulk density, dynamic modulus of elasticity, ultrasonic pulse velocity, flexural strength and compressive strength were measured. These factors were compared with the each initial value after 14 or 28 days, and the resistance to freezing and thawing was evaluated. From the experiments carried out for three years since 1988, the following results were obtained.
1) The plain concrete (without air entraining agent) made with Masa-do as a fine aggregate has a lower resistance to freezing and thawing than that made with river sand.
2) Whenever the air content of concrete was increased to 4% or more by an air entraining agent, the resistance to freezing and thawing was improved considerably.
3) To evaluate the resistance of concrete to freezing and thawing, ultrasonic pulse velocity as well as dynamic modulus of elasticity are the effectual methods.
4) The bulk density of concrete is not influenced by freezing and thawing, because freezing and thawing is not the chemical attack.

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Subsidence of peatland has become a matter of great concern according to the change in peatland use.
Surface movement of peat ground and fluctuations of groundwater level were continuously observed on peatland in different stages of land use. Observations were carried out on an undrained bog under natural conditions, an insufficiently drained and unused bog, and a drained bog used as a paddy field in its fallow period.
Ground surface of undrained bog sensitively moves following fluctuations in the groundwater level. Surface of the drained bog did not move when the groundwater level kept its range of fluctuations in the ordinary zone, but it subsided when the water level declined drastically, and slightly restored itself when the water table rose drastically.
These differences in surface movement are caused by the change in property of peat due to drainage. Consolidation of peat after drainage, shrinkage by drying, and decomposition and loss of peat material are the cause of peatland subsidence. Beside shrinkage and decomposition, consolidation is the most serious problem faced.
Fluctuations of groundwater level cause load hysteresis in the peat. Consequently, the surface movement is less in the drained bog where hysteresis is the most intense. When the water table declines below the ordinary fluctuating zone, further subsidence occurs, since the underlayer is less effected previously.
Patterns of surface movement in relation to the fluctuations of the groundwater level vary according to the degree of drainage. Three patterns of surface movement are mentioned based on the degree of drainage.

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The behavior of twin parallel buried flexible pipes is influenced to a considerable extent by the properties of the backfill material, ring stiffness of the pipe and reaction of each pipe.
This paper discusses the effect of ring stiffness on the behavior of buried flexible pipes, obtained by experiments using the steel test-pit and numerical analyses.
Three kinds of fiberglass reinforced plastic pipe (φ200 mm) with different flexibilities are used. The values of ring stiffness for “P I”, “P II” and “PIII” are 3, 500 N/m², 10, 900 N/m² and 51, 500 N/m², respectively. The backfill material is dry SETO siliceous sand.
The results obtained are summarized as follows:
1) In case of twin buried conditions, the reducible ratio as compared with the deflection of single buried condition decreases with the increase in the ring stiffness of pipe. Its effect in the horizontal direction is larger than the vertical direction.
2) Judging from the circumferential strain of pipe, non-symmetry of pipe deformation increases with the decrease in the ring stiffness and distance of each pipe. Pipe “P I” separated from each other at the distance of one-half of the radius of pipe under 250 kPa overburden pressure has peak circumferential strains at the points that incline 40° upper and lower from the spring-pline of the adjacent side.
3) The distribution of the normal earth pressure acting on the pipe changes remarkably by ring stiffness and buried condition. In case of “PIII” under the twin buried condition, at the crown and the spring-line of adjacent side of the pipe, normal earth pressure shows about 1.08 times as much as overburden pressure. However, the distribution of the tangential earth pressure is hardly influenced by ring stiffness.

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The kinematic wave approach is one of the physical models regarded to be more suitable for flood runoff analysis of reclaimed farmlands with distinct basin characteristics. To apply the kinematic wave approach to runoff analysis, experiments with a steady overland flow were conducted. Roughness coefficients were examined by analyzing the recession curves of the hydrographs. Largescale lysimeters were used in both indoor and outdoor experiments. In the indoor experiments, bare surface, ridged surface with vinyl mulch, turf surface, and weed surface slopes were used, while in the outdoor experiments bare surface and weed surface slopes were used.
In this study, the applicability of Manning's law was first confirmed by examining the relationship between measured flow depth and discharge. When the recession coefficient was determined by reference to the hydrograph, it revealed that the recession coefficients increased with gradient and water supply intensity. Finally, based on the relationship between storage and discharge, the roughness coefficients were estimated using the recession coefficient. The results obtained were as follows. The roughness coefficient bore no relationship to the gradient and discharge. In the indoor experiments, the roughness coefficients for the ridged slope, bare slope, weed slope, and turf slope were 0.03-0.07, 0.04-0.06, 0.01-0.2, 0.6-0.7s/m^1/3, respectively, while in the outdoor experiments, the coefficients for the bare slope and weed slope were 0.09-0.2 and 0.3-0.7 s/m^1/3, respectively. In the outdoor experiments, because rapid interflow occurred at high infiltration rates, this effect was included in the calculation of the roughness coeffcients.

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In this paper, the necessity of land readjustment to keep agricultural productive and establish land use order, in urbanizing area called the white zone of the agricultural promotion area (APA) was proven. Also, some techniques on land readjustment in urbanizing area were suggested.
The following conclusions were derived.
1) The function on land use in the white zone of APA has two sides. One is the conservation of APA from conversion to urban use, and the other is forming a more comfortable living environment. So, it is necessary to regard land readjustment as important for establishing land use order.
2) In order to solve the difficulty of the land readjustment project taking effect in an urbanization promotion area, it is realistic to arrange conditions in land readjustment in APA.
3) In land readjustment in the white zone of APA, it is necessary to arrange urban facilities and keep non-agricultural land obligatory by allocation.

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An attempt was made to extend the heat balance snow-melt model proposed in our previous paper for practical application regarding snow-melt runoff analysis.
As a result of the study, the model was improved regarding a few points, and functions which distinguished between solid and liquid precipitation, estimated snow density and albedo in addition to the function of calculating snow-cover runoff.
The extended model, that was the heat balance snowpack and snow-melt model, was applied and tested at 3 stations in Sapporo, Yuda and Jyoetsu.
Satisfactory results could be obtained from the tests on the presumption of snow depth, water equivalent of snow and snow density and the usefulness of the model was successfully demonstrated.

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[in Japanese]

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[in Japanese]

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This report has been organized with a view to developing sustainable easy-to-cultivate Junsai paddy fields which would provide a high yield of good quality Junsai. Theresults of a nationwide questionnaire conducted by the author reveal the present condition of Junsai-gathering. And furthermore the course of Junsai paddy field reclamation and readjustment is discussed by giving related examples from several parts of the country. The points of the report are as follows:
1) This species of Junsai is widely distributed all over Japan at present. It grows naturally in small reservoirs, swamps and ponds, and is cultivated in Junsai paddy fields as well. The Tohoku district contains most of the yield areas of Junsai in Japan, and occupies the greatest part of the yield. In particuar, Akita Prefecture occupies about 85% of the whole domestic yield.
2) The lot of Junsai paddy fields should be rectangular in shape both for efficient maintenance and for gathering a higher yield of Junsai on it. There are, however, not a few of nonrectangular ones, which range in area from 10 to 30 areas.
3) Junsai paddy fields consist of three land-reclaiming components such as foundations, surface soil and levees. The fields are completed by adding various facilities to these components. In building a levee, it is necessary to take into consideration materials used, levee slope protection and frequency of its use etc.
4) The most important factor in planning their reclamation consists of determining how big the design water depth is. In planning the reclamation of a Junsai paddy field, the optimal depth is estimated to range from about 50 to 70 cm for Akita Prefecture.
5) The Junsai paddy field contains such facilities as inlets and outlets for irrigation water, water exchange and pump-up facilities, small piers, and windbreak facilities etc. The adoption and size of these facilities above depend upon the weather, water use, soil and Junsai-gathering conditions of each region where they are located.

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Building levees for a Junsai paddy field reclaimed from wet land requires a lot of efforts to make them strong in structure and large in size, because of its comsiderable water depth and high frequency of its use etc. This paper is intended to examine the results of investigation into the erosion of earthen levees and slope-protected levees with the object of developing such fields that would be easy to maintain and provide a higher yield of good quality Junsai more efficiently. The point of the results is as follows:
1) A progressive reduction in the volume and strength of earthen levees has been noticeable with time. That is for example, about 16% after 10 years of service, and about 25% after 15 years. The volume and strength reduction is assumed to be caused by an overestimate of the design water depth, use of the subsoil for a levee or faulty maintenance.
2) Boards, plywood, wave-type plastic sheets, concrete sheet piles and U-type flumes have been used as slope-protection materials for various kinds of slope-protected levees, which have the advantage of durability and erosion resistance over earthen levees. Both of these levees have their own service life: plywood ones have a life of 7 years. In addition, the cost of building some of them is considerably high.
3) The earthen levee for a Junsai paddy field is a comparatively stable earth-structure that has a lot of advantages. Proper management allows the field to last sufficiently long. A combined use of earthen and slope-protected ones can be recommended in light of their strong points. It is necessary to protect the slopes from erosion by means of wave-type plastic sheets immediately after reclamattion, until wild plants grow thick on them.

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This study was conducted to clarify the conditions of fitting soil and the water environment in an artificial forest of a botanical garden for development or conservation of urbanized green areas to be constructed in future. The content investigated in this study consisted of the physical properties of the soil, that is, real specific gravity and bulk density, distribution of soil particle size, water permeability, water-holding capacity, etc. Furthermore, the ground of the artificial forest was banked about one or two meters over the original paddy field. Moreover, the physical properties of the soil in the orchard which is adjacent to the botanical garden were investigated too.
The results obtained are as follows.
1) The soil layers in the artificial forest and orchard were found to mainly consist of silty sand soil with a lot of gravel and stone.
2) The bulk density of soil layers in the artificial forest were found to be the same grade as in the orchard, but the real specific gravity in the former was higher than that in the latter.
3) The permeability of soil layers in the artificial forest and orchard were within the range of 1.0×10^-2-1.0×10^-3 cm/s.
4) The water-holding capacity of soil layers in the artificial forest showed a higher value than that in the orchard.
5) Though the ground in the artificial forest has passed several tens years after it was constructed, the soil conditions were judged to be superior to general forests or general upland fields.

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This study was carried out to clarify the soil moisture characteristics in an artificial forest of a botanical garden and orchard which are adjacent to each other. The soil moisture characteristics were investigated by the daily fluctuations in soil moisture from August to September when the dryness of soil is at its peak. The results obtained are as follows.
1) Precipitation conditions in August and September in 1987 were found to correspond to the droughty year of one-third to one-forth probability.
2) Situations of soil moisture in the artificial forest amounted to over 400 cm H₂O at a depth of 90 cm.
3) Situations of soil moisture in the orchard were below 300 cmH₂O at a depth of 70 cm.
4) Average value of soil moisture in the artificial forest was in the range of 500cmH₂O to 630 cmH₂O under a soil layer condition of 90 cm during the dry period, but in the orchard itwas below 250cmH₂O.
5) Soil layers in the artificial forest were found to be dried than that in the orchardbecause the ground level in the former where is artificially banked over the original ground is higher than that in the latter, and consequently, the rainfall can not be stored to any extent in spite of having a higher water-holding capacity.

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The research for microbial reaction rate is inevitable to develop the design and management technique of wastewater treatment facility in rural settlement.
In this paper, the modeling concept of microbial reaction, the removal principle of organic matter and nitrogen, characteristics of influent wastewater and activated sludge, are arranged at the beginning.
Then the following kinetics are lead and relations among them are arranged systematically, with an eye on analysis of wastewater treatment by Batch-Activated Sludge Process.
1) growth of activated sludge
2) removal of organic matter and nitrogen
3) balance of oxygen
As an example, kinetic model equations which represent changes of water quality in a batch cycle are applied and the concept of procedure to require parameters are shown.

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In irrigation system with an open channel, water supply-oriented control is generally applied to adjust the difference between water demand and its supply. Though the water supplyoriented control is necessary in the peak demand season, the demand-oriented control is able to be applied in other seasons because the system has ample capacity to convey the required water. In this paper, it is made clear that the absorbability can be evaluated by the averaging time of the system, and then on the viewpoint to average the water demand fluctuation occurring due to water consumption, how to determine the storage capacity for regulation and how to design canal system are discussed.

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