The area where there is large discharge subsurface flow over an impermeable layer was defined in this study as variable source area (VSA). The component of water flowing slowly was not considered. An equation for determining the moving boundary of this VSA was derived. It was found to be applicable to an one?dimensional unsteady model.
In this derived equation, there is only one unknown parameter which is the ratio of water depth (i. e., water volume per unit area affecting direct run?off) to discharge per unit width. So it is possible to determine both the moving boundary and Darcy's flow in VSA using this unknown parameter.
The following assumptions must be made for run?off analysis. The first is effective rainfall. All rainfall into VSA is effective. The second is increasing velocity of VSA. In this paper, a term related to this increase was considered to-be linearly related to rainfall intensity and to the len gth of the no-source area. The third is that water depth is related to discharge. Water depth was considered to be linearly related to discharge.
A reclaimed terraced field made by cutting and banking a clay hill-slope was used for this research. A clay layer was under the plow layer or the banking, thus the first assumption was justified to some degree. Inverse analysis of run-off discharge indicated the second assumption to be essentially valid. The simulated response of peak discharge was slow compared to the that measured values.

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Toward the rationalization of upland irrigation water requirement design in humid climate region, it is one of the effective ways to estimate consumptive use as the difference between evapotranspiration and upward moisture supply. In this paper, upward moisture supply from sub layer to root zone was estimated by a water balance model in the five layers.
Results obtained are as follows;
(1) Upward moisture supply occurs in the surface layer at first, then moves downward one after another. Soil moisture in the surface layer recovers slightly during night time.
(2) At least 1-2 days are neccesary to change the hydraulic gradient in root zone from downward to upward direction after irrigation or rainfall, even under a large amount of evapotranspiration. Upward moisture supply doesn't occur during the period.
(3) The amount of upward moisture supply is generally proportional to evapotranspiration, and changed by the ratio of soil surface evaporation to evapotranspiration. It is also proportional to the moisture holding capacity of soil.
(4) The amount of upward moisture supply is influenced by the variation of transpiration ratio among layers, and decreases slightly as root zone depth increases.

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It is statistically unreliable to estimate design reservoir capacity requirements from river flow data observed for not enough number of years. Synthesis of river flow data having the same statistical parameters of a record is proposed to fill this insufficiency of record length. With this proposal, the authors' question is whether capacity requirement calculated from time series of synthesized flow data preserving the value of statistical parameters of record will statistically agree with that calculated from original record or not.
Two kinds of capacity requirements at various demand levels are statistically compared, using five-day average of river flow data observed at three typical multipurpose reservoirs in Japan. One requirement is directly calculated from record itself, and the other is calculated from the data synthesized by the Thomas-Fiering Method, which preserves such statistical parameters as the mean, the standard deviation and the auto-correlation of a record.
The results of this study show that the synthesized capacity requirement has statistically regular biased tendency. Preservation of the statistical parameters in observed flow data will not connote statistical agreement of synthesized capacity requirement with that estimated from record.

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Capacity requirement calculated from river flow data synthesized by Thomas?Fiering Method has statistically regular biased tendency in comparison with that calculated from record itself. The bias might be caused by calculation from synthesized flow data that have symmetrical distribution, which is different from the observed one. An adjustment of synthesized data by logarithmic normal transformation results in some improvement in estimation of capacity requirement as a whole. However, this adjustment still does not show enough agreement in the estimation of capacity requirement, especially at low levels of release requirement.

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This paper is the third of a series of reports on the pond-regulated pipeline irrigation systems in operation in Tonami Plain of Toyama. They carry water smoothly down the pipelines thanks to the geological gradients of the alluvial fan landform of the area. The purpose of these systems is to close the gaps between supply and demand in such a way as to allow flexible and efficient use of any required amount of irrigation water whenever and only when it is needed. Through analyses of data on the water balances of four of the regulating ponds obtained over an 8-year period I have found the following:
(1) An analysis of the water balances of the ponds shows (a) that the percentages of inflows into the ponds relative to the total out-of-pond discharges (Q_in/Q_fi) range from 125 to 168%, (b) that out-of-pond discharges divided by the acreages of the benefited paddies (Q_fi/A), i. e.the water depths, register greater values in proportion as the pond-regulated systems are located further upstream and (c) that the percentages of pond uses relative to the total out-of-pond discharges (Q_po/Q_fi) register greater values in inverse proportion to the acreages of the benefited paddies (i. e. the smaller the acreages, the greater the percentages).
(2) The per-day maximums of out-of-pond discharges (maxQ_fi) far exceed the maximum gross water requirements for the ordinary irrigation period (q). This tendency is especially conspicuous from the latter half of July to August, when rice plants start to develop their spikes and come into ears.
(3) Obviously the above tendency means that pond-regulated irrigation systems allow more flexibility in irrigation work in terms of both access timing and the quantity of irrigation water readily available and it also shows that during these months the regulating ponds are used to a greater extent than at any other time in the rice season in order to meet the need for intensive irrigation.
(4) The practical experience of farmers and/or telemeter monitoring systems enable them to use irrigation water optimally without overburdening the present capacities of the regulating ponds.
(5) The design capacities of these regulating ponds have been determined on the assumption that the actual needs in irrigation work will be more or less satisfied by pondages of a magnitude approximately equal to q × 6 hrs. The ratios of the consumptions of pond-stored water to the pond capacities show a quasi-normal distribution curve and range for the most part from 20 to 70%, clustering most densely between 30 and 60% and exceeding 70% at some sites. With pipeline-involved systems of this type, it goes without saying that we must take care to avoid any air entraining liable to occur when the water levels of the ponds fall extremely low. However, given the actual pond use of the above ratio distribution, it would seem that, besides satisfying the irrigation needs, our design criterion is also appropriate enough not to incur such problems.

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This paper is the fourth of a series of reports on the pond-regulated pipeline irrigation systems in operation in Tonami Plain of Toyama and deals with some central aspects of these systems that previous papers did not address.Analyses of the observation data on three of the systems obtained over an eight-year period have yielded the following findings:
(1) Out-of-pond discharges (Q_fi) usually peak between 6 and 7 a.m.and/or between 7 and 8 p.m.The maximums of Q_fi during the morning peak hours often far exceed the maximum gross water requirements for the ordinary irrigation period (q).
(2) Pond uses (Q_po), which are meant to compensate for the excesses of Q_fi over inflows into the ponds (Qin), are devoted for the most part to morning irrigation in keeping with the peaking of Qfj.
(3) Data on Q_in, Q_fi and Q_po, graphically plotted, show that there are three patterns in how they are related to each other, i.e.morning peak type, two-peak type and evening peak type.
(4) Let us define T_po as a per-day discharge excess over the discharge average (avr, Qfi), calculated in terms of the discharge average multiplied bynhours and for convenience expressed simply asnhours.Then we obtain a formula V=T_po·avr QM where V stands for the design capacity of a regulating pond.
(5) I chose the 10 topmost of per-day Q_po and averaged out the T_po values for these Q_po data. These T_po averages range from 3 to 6 hrs. Since they reflecting the actual demands of the benefited paddies, they can be expected to be optimal design criteria for pond capacities.
(6) The smaller the acreages of the benefited paddies (A), the greater are the T_po values. Besides, as I pointed out in my previous paper, the smaller the acreages, the greater are the values of Q_po/Q_fi. These facts suggest that the T_po value of 6 hrs, which was obtained in the smallest pond-regulated irrigation system can be regarded as the safest capacity for a regulating pond.
(7) The foregoing consideration of T_po would allow us to draw the following conclusion: since the actual T_po values range from 3 to 6 hrs, the values of T_po in the formula V=T_po·avrQ_fi should be determined within this range and since, as I reported in my previous paper, the maximums of pond uses are concentrated between the latter half of July and August, the value of avr Q_fi should be pegged atqfollowing a generally accepted criterion for irrigation facilities. Needless to say, in determining the values of T_po, we need to take into account several related factors, such as the characteristics of water sources, the meteorological conditions of the areas concerned and the characteristics of benefited paddies including, importantly, their acreages. We now know that, the smaller the acreages, the greater are the T_pos. At any rate the T_po value of 6 hours can be regarded as a safe enough criterion for determining the design capacities of regulating ponds.

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The characteristics of wet deposition of acid precipitates along the shore of the Japan Sea in the northern part of Honshu Island were investigated. Precipitation was sampled from January 1990 to December 1992 at two sampling sites in thewestern area of Yamagata Prefecture. Event sampling was done with wet-only collectors. In this area, the acidity of precipitation in winter was higher than that in summer. The acidification of precipitation in winter was mainly due to non-sea-salt-SO₄^2- (nss-SO₄^2-). Concentrations of NO₃^-in the precipitation did not show any conspicuous seasonal changes. In winter, the ratio of [NO₃^-]/[nss-SO₄^2-+NO₃^-] and that of [nss-Ca²⁺]/[nss-SO₄^2-+NO₃^-] in this area were consistent with those in northern China, while in summer they were consistent with those in eastern Japan. The analysis of weather charts at the time of precipitation in dicated that nss-SO₄^2-concentration and nss-Ca²⁺concentration of precipita tion due to the meteorological condition of typical winter and cold fronts were relatively high. These results suggested that the anthropogenic ions in this area mainly came from the Eastern Asian Continent in winter and from domestic sources in summer.

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To ascertain the resuspension rate of sediments, the mechanism and the process of the formation of tidal flat, laboratory measurements were made to study the flow characteristics of sediment which settled from a suspension to form a deposited layer in still sea water. Experiments were performed using two sediments which were collected in the interior shallow region of Ariake Sea. Experimental conditions were set up to simulate the field conditions.
The experimental results showed that the flow characteristics of sediment were influenced by the type of sediment, initial sediment concentration, sea water salinity, and the water content. In particular, the relationship between the flow characteristics such as viscosity and yield shear stress, and the initial sediment concentration, water content could be expressed by a power law. However the effect of salinity of sea water on the flow characteristics was very small. These observations were interpreted by appropriate relationships characterizing the structure of the aggregate and the effect of the bonding-force between the sediment particles.

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The applicability of the proposed equation on the fltation and settling velocity of a single Microcystis floc was examined using additional data which were taken at different seasons. It was found that the degree of scatter in the velocities were a few times larger than that obtained for non-biological samples. The extent of scatter in the velocities for small sized colonies were larger than that obseved for large colonies. These findings imply that there exists a transition from uniform structure to self-similar structure of the colony. From the analysis of settling velocities of pressurized colony, it was clarified that the morphology of Microcystis flocs can withstand for theapplied pressure up to 1.0 MPa.

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In this study, the particle size effect was evaluated by using a anchor pullout test and a trap-door test on glass beads having different grain size (s) of 0.2 mm and 0.4 mm. The anchor pullout tests were performed on the circular anchors with diameters (B) of 2.5 cm, 5.0 cm and 10.0 cm, and were to measure load-displacement relationships.The trap-door tests were made to observe the shear band development using thin horizontal colored layers. For a given B, a nondimensional load parameter for s=0.4 mm was exhibited greater than the one for s=0.2 mm. The deformations of shear band for both s=0.2 mm and 0.4 mm were not equal at the same displacement. The differences were due to the effect of grain size relative to B (the grain size effect). In case the ratio of s to B was same, the nondimensional load parameter agreed to the deformation of shear band. It was clear that the shear deformation of shear band was governed by the grain size.

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To ensure a) large scale participation by the core farmers in the projects and b) the accumulation of farm land by the core farmers on the execution of the projects, the proposal for the payment to the farmers, the farm rent and special organization of land use coordination should be newly proposed as follows.
There are two new systems in order to encourage core farmers and to participate in land consolidation projects. These are a lease system and the utilization of a special organization of payment of a farm rent in advance. The former one means that the tenant will pay a lease fee for a long period of time. The latter one means that we should make the best use of the special organization for the promotion of the accumulation of land to core farmers, where tenants should make payment of construction costs and farm rents annually, and the farm rent should be paid in advance to the landowner by the tenants.

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Water requirements for direct seeding of rice in the tropical monsoon region of Asia is discussed in this study. The Muda irrigation area, the largest rice producing area in Malaysia, was selected as a study area, where direct seeding method (wet seeding and dry seeding) has spread rapidly since 1980's. Irrigation water requirements after spread of direct seeding has compared with that when transplantation method has shared 100% of the area, and analysed the causes of the difference by considering the change of farm operation and irrigation management.
Furthermore difference of water requirements by the spread of direct seeding and construction of tertiary canal and farm road has been analysed in the selected four study irrigation blocks for three years.
As a result of this study, following findings have been obtained.
a) Direct seeding method requires less irrigation water than transplantation method both in the 1st and 2nd cultivation seasons. Water requirement has decreased from 1879 mm to 1642 mm in the 1st season, and decreased from 1548 mm to 1446mm in the 2nd season by the shift of cultivation method from transplanting to direct seeding.
b) The reasons of decrease of water requirement in the 1st season are (1) shortening of irrigation period by the spread of dry direct seeding and (2) reduction of water requirement to nursery in whole main field.
c) In the 2nd season the decrease of water requirement is not so much as the 1st season. But (1) by the spread of wet seeding the shortening of irrigation period for rooting and (2) shortening the period between harvest in the 1st season and start cultivation of 2nd season.
d) In areas of no tertiary canal, where percentage of direct seeding are low, irrigation water requirements were higher than areas with tertiary canal where spread direct seeding in high percentage. It was shown both in the 1st and 2nd cultivation seasons during all three analysed years.

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Crop diversification means introducing non-rice crops to paddy based land during the dry season in Asian developing countries. In this diversified land, moisture movement in subsurface soil layers is complex and diverse for the existence of plow sole formed through paddy cultivation. This complex movement influences estimation of crop water consumptive use (CU) by the soil moisture depletion method. To analyze the complex moisture movement, the author applied total potential (TP) gradients, CU and soil moisture extraction pattern (SMEP). The CU and SMEP were determined by the modified soil moisture depletion method which estimated evapotranspiration (ET) distinguishing ET from drainage loss in the depletion amount with the zero flux plane (ZFP) identified from the TP gradients. The results of analysis are summarized below.
(1) No influence is identifed for existence of plow sole to estimate CU amounts.
(2) The CU rate of plow sole layer is bigger than that of the right above layer.
(3) Upward water supply from the subsurface soil layer through plow sole is apparently intermittent in the case of long irrigation intervals.
(4) Under low evaporative demand conditions, TP gradients become sharp above the plow sole although upward water supply occurs from the layers below the plow sole.
(5) Under high evaporative demand conditions, TP gradients become sharp in and above the plow sole layer, mainly to supplement upward water supply which is decreased for the lowered hydraulic conductivity of the plow sole with soil dry.
(6) Under extremely high evaporative demand conditions, a phenomena happens that the TP gradient between the plow sole and the right above layer shows adverse moisture movement direction to the real flux.
For the adverse TP gradient described in (6), an untrue ZFP appears above the plow sole layer. Analyzing TP gradient changes is, thus, required to avoid under estimation of CU for the untrue ZFP in applying the modified soil moisture depletion method under high evaporative demand conditions.
This study is based on the data collected in a Japan's technical assistance project called Diversified Crops Irrigation Engineering Project which was carried out from 1987 to 1992 in the Philippines.

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In recent years there have been several reports published on researches regarding regulating ponds in irrigation systems. All these researches are presumed to share the goal of designing regulating ponds of the kind that will serve to close the gaps between supply and demand in such a way as to allow maximal flexibility in irrigation in terms of both the quantity of water available and access timing. The present paper is an attempt to put these researches in perspective in order to define their relative significance.
Ogata (1984) succeeded in simulating formulaically the interrelationship of the amounts of inflows into regulating ponds, the pond capacities and the gaps between supply and demand. Cho (1984) devised a formula for obtaining pond capacities commensurate with the trapezoidal patterns of water demand peculiar to upland field irrigation. The research by Ezaki (1989) confirmed that the patterns of water demand will present comparably simple profiles. Nishide (1989), dealing with horticulture irrigation, identified the patterns of water demand, the degrees of freedom in irrigation and the ratios of the amounts of discharges via the spillway to those of inflows into the regulating pond. Yoshino (1989) designed a calculation procedure based on the assumption of non?uniform flow in order to determine the design capacity of a so-called buffer pond installed at the site where the open channel system is linked to the pipeline system. Mitsuno's theoretical study (1992) demonstrated that an open channel system inherently has a filtering function of absorbing flow fluctuation. Hirose's statistical study (1989) proposed realistically optimal design criteria for determining the capacities of regulating ponds in pipeline irrigation systems. His proposal was derived from the processing of accumulated data on the actual water balances of several regulating ponds.
The researches by Cho, Ezaki and Nishide mainly dealt with upland field irrigation. On the other hand, those by Yoshino and Hirose presented practical methods of determining pond capacities in paddy irrigation systems. Yoshino's procedure will suit a system in which information about use of a regulating pond can be easily fed back to the management of the gate in the diversion works. Hirose's study addressed the irrigation needs and features of a benefited area where intake operations in the terminal paddy blocks are conducted in a not so finely-tuned way (as is usual in Japanese farming) at an interval of a day or even a few days. His proposal was aimed at enhancing the degree of efficiency and freedom in this kind of irrigation to such a level where any required amount of water is available at any time and is used only when it is needed.
Mitsuno showed that the mechanism underlying the fluctuation absorbing function of an open channel system can be theoretically accounted for in terms of spectrum functions. One implication of his research findings is that further research along his line might provide a comprehensive theoretical framework which would enable us to explain in a unified way a whole set of fluctuation phenomena in irrigation systems. It might also be expected that this theoretical development might finally be technologically reflected in the system design of a user?oriented irrigation unit combining in an optimal way the storage function of an open channel and the regulating capacity of a farm pond.

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