By using simulation procedures modeled by unsteady moisture and solute transfer differential equations, the simultaneous movements of water and NaCl were numerically examined in the soil columns in which plant roots were distributed in a specified pattern. The soils used for the study were dune sand and sandy loam, of which the pF-θ curve, K-θ curve and D_s-v curve were laboratory measured. The water applied showed a 2, 000 ppm concentration of NaCl, being kept at a constant intensity during the drip time. The transpiration rate was assumed to correspond to the sine-function curve. Also, the transpiration rate became equal to the sink rate at which water was consumed by the total plant root at the same time of transpiration.
1. The NaC1-profile, which represents a distribution-type of NaCl concentration calculated by the simulation models, approached Raats's analytical results calculated in the steady state, when the drip time was increased to over 10 days in the case of dune sand or over 20 days in the case of sandy loam. As a result, the characteristics of the NaCl-profile were analyzed using various factors such as leaching fraction, drip discharge, drip time and interval day on drip irrigation.
2. The NaCl-profile developed more according to the greater depth in the soil columns during the drip time, but the rate of NaCl-profile was reduced temporarily after the drip time. The steadystate NaCl-profile was gradually formed by repetitions of the developed-and reduced-processes. The rate of NaCl-profile became generally faster in the dune sand than in the sandy loam.
3. Under the conditions of the constant leaching fraction in which the daily water applied was 7-10 mm and the daily transpiration was 5 mm, the holding capacity of the moisture content decreased and the holding capacity of the NaCl increased as the drip time became shorter or the interval day became longer. The maximum NaC1 concentration increased with decreases in the leaching fraction in the dune sand and sandy loam.
4. The NaCl-profiles calculated by the simulation models were compared with the field experiment, which were assumed to consist of one-dimensional salt movement in a netted-melon sand field which was drip irrigated. The calculated results agreed with the types of salt profiles measured in the fields.

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An irrigation system is usually designed to minimize the variation of water discharges in the system, because water application efficiency has a close relationship to the variation of water discharges which is called water-distribution efficiency. However, the water-application and waterdistribution efficiency are not theoretically related to each other. Assuming that the emitter discharges in a drip irrigation system distributed normally, the relationship among the water-application efficiency, water-distribution efficiency, and percentage of deficient water could be analytically developed. When the water-application efficiency and percentage of deficient water are determined as design criteria at the first step to a drip irrigation system design, the water-distribution efficiency allowed for the system can be calculated. The water-distribution efficiency is the outcome of a number of factors such as hydraulic variation and the manufacturing variation of the emitters in the system. The previously proposed design procedure includes the pressure head variation at the emitters and the manufacturing variation of the emitters. Then, the drip irrigation lines in a submain unit can be designed by the proposed procedure. If the design criteria of the drip irrigation system are that the water-application efficiency is 95% or more and the percentage of deficient water is 4% or less, the coefficient of variation of emitter discharges in the system (the water-distribution efficiency) is designed to be 0.10 or less.

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In agricultural drainage systems, a coastal closed conduit structure has been frequently used as a method for solving problems related to river-mouths. In this paper, an effective improvement of the closed conduit structure is proposed on the basis of the results of the experiments described below.
Experiments
Several hydraulic phenomena, which occur when coastal sediment plugs are opened automatically by a stream, were investigated experimentally. The phenomena were affected by the critical velocity which prevents ocean waves from going upstream, the process of the automatic opening of coastal sediment plugs, and the influences of the wave and tide level on the automatic opening process.
Improvement Method
Taking the above experimental results into consideration, the layered structure was chosen as being an improved structure for the closed conduit. It was confirmed experimentally that the layered strucure has the following effects: 1) perfect sand flushing at the conduit bottom, 2) the control of the rise of the water level in the conduit, 3) the suppression of the wave progress into the conduit, and 4) the restraint of the closed stream-mouth.

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Yoshii Wier, which was constructed three hundred years ago, now has fused completely into the natural system surrounding it, and is still continuing to play an important role in forming the subsurface environment there. In this paper, the authors have tried to show that the Yoshii Wier has other functions except the intake of irrigation water from the standpoint of groundwater cycle.
The observed groundwater level fluctua tions in 1982 at representative points around the wier were statistically analyzed, and as a consequence, it seems that the fluctuations generally occur due to the influence of paddy field irrigation and the water level of the Yoshii River. Especially, it has become clear that the groundwater level is mainly affected by the river water level in the upper district of the wier, due to irrigation in the lower district, and by both in the intermediate district. Therefore each fluctuation component is quantitatatively evaluated as multiple regression coefficients.
The time constants in groundwater level discent after irrigation are almost the same everywhere in this district, 9. 5 days.
These conclusions obtained from the statistical analysis give some important input data for simulation using the mathematical model of the regional groundwater flow in the following papers.

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The applicability of the Kriging technique for the soil properties of dune sand was examined. Sixty-six soil cores were sampled from dune sand surface in a 100m long and 50m wide area at the nodes of a 10m square grid. The measured properties had a silt content, which is the ratio of the weight of that soil passing through a 0.074mm sieve to the bulk sand weight, Na concentration and electric conductivity in 1: 5 soil-water suspension.
The semi-variograms for these properties were approximated by linear-type equations. The neighboring distance determined by the jack-knifing method was 21m at most. Using the values estimated from the Kriging technique, reasonable contour maps for the properties were obtained and they showed definite spatial characteristics for the properties. The comparison of these maps represented the similarity of the distribution between the Na concentration and electric conductivity, but not between the silt content and the other two properties.

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An automatic control valve is recently used for relieving pressure and maintaining appropriate pressure in closed conduit for irrigation system. Considerations were made on what influence the valve have on hydraulic phenomena in closed conduit. Firstly, hydraulic experiments were carried out to make clear dynamic characteristics of the automatic control valve, and in accordance with the results, theoretical simulation for numerical experiments were carried out to estimate pressure variation in closed conduit with the valve. The conclusions thus obtained are as follows.
1) Sensitivity of the automatic control valve for responding to flow disturbance can be made adjustable by having the controlling system built in the valve. The pressure variation which occurs in closed conduit by hydraulic transient varies with the established sensitivity of. the valve.
2) When a situation of hydraulic transient acts to open an automatic control valve located in a closed conduit, the valve has the effect of reducing pressure variation without regard to sensitivity of the valve.
3) In case that the valve is adjusted to suitable sensitivity, it is able to perfectly control pressure variation of water-hammer at downstream side of the valve without increasing the pressure variation at upstream side of the valve. The optimum sensitivity of the automatic control valve is changeable with the various conditions of pipeline and the situation of hydraulic transients.
4) If automatic control valve is adjusted over-sensitivity, waterhammer pressure wave may be enlarged by elastic behavior of the valve, and steady pressure oscillation will be formed.

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Theoretical approach was tried for evaluating the dead time D (s) and time constant T (s) as parameters of the lead time of the response of flow due to operation in an open-channel with step works in a series.
The main procedures are shown in terms (1)-(3) as follows.
(1) The nom-dimemsional discharge per unit width K_q (x, t) was defined as Eq.(A).
_??_(A)
in which, q: discharge per umit width (m³·s^-1·m^-1), x: distamce from upstream boundary im the openchannel system (m), t: time afer operation (s), subscript b: quasi-uniform flow in initial state and subscript e: quasi-uniform flow in the final state.
(2) Input fumction K_q (0, t) at the upstream boumdary wasgivem as a step fumctiom of time t, and output k_q (x, t) at the downstream boundary was obtained as the calculated results.
(3) The Eqs.(B) snd (C) were apPlied to evaluate the dead time D and time comstamt T in the indicial respomse of flow im an open-chammel under various conditions.
D+T=l/w₀ (B)
_??_(C)
in which, l: partial Iength of chanmel bound with each step work (m), w₀: velocity of hydraulic bore (m/s), μ₀: equivalent to q_b/2i (m²/s), i: bed slope of the opem-channel.
Eq.(B) was derived from the condition of continuity, and Eq.(C) was derived from the diffusion analog model.
The mathematical model for evaluating dead time D and time constant T of the flow in an openchannel with step works in a series was presented and checked using a numericalanalysis.
The validity of this model was confirmed within about 10 step works in an open-channel.

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The flow characteristics of the large scale roughness on the mild slope channel were studied experimentally and the following facts were found.
1. On the flow over a sill, the relations among the flow surface profile classification, the energy loss and the flow conditions showed in a diagram.
2. As the expression of the energy loss of the large scale roughness, the form loss coefficient f and the effective drag coefficient β²C_D (C_D: the form drag coefficient of roughness element, β: the ratio of degradation of fluid force acting on the element due to the covering by the upstream roughness element) were used for adjustment of test data. The relations of f-n (n: the roughness setting rank number), and β²C_D-n were found on each testing cases. In generally, f increased and β²C_D-n decreased with increasing n.
3. On the sill group, the largest resistance were obtained at the case of S₁/D=10 (S₁: flow-ward sill setting space, D: height of sill). The relations of f-n, β-n and C_D-D_r were obtaind by the experimental equations.(D_r=D/H₂, H₂: downstream station depth)
4. On the block roughness group, the 9 cases that combined the 4 arrangement patterns with the 4 block shapes were tested.
The relation between classification of overflow surface profile and the flow conditions are shown in diagram and these characteristics were about the same with the sill cases.
On the resistance characteristics, the relations f-n, β-n and C_D-D_r, were obtained as the experimental equations for the each tested case.
5. The influence of the arrangement of blocks to the energy loss were tested under the same condition of the block shape, setting rank number, and flow condition.
The energy loss were afected largely by the B_rD_r (B_r=Σb/B, B: the width of channel, Σb: the sum of each transverse-ward block width on a rank.) and S₁. At the B_rD_r>0.103 of the zigzag arrangement, the energy loss increased with decreasing S₁ as far as some S₁. But at the B_rD_r<0.103, the loss did not vary with S₁ variation and showed a nearly constant value.
The lattice looking arrangement showed a loss smaller than the zigzag's one at small S₁ but the difference of both the losses lessened with increase in S₁ and at last both the losses became the same.

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To clarify the mechanism of the water quality change in paddy fields, the water quality of irrigation water, ponding water of the paddy field and drainage water have been investigated for six years in the Kameda District.
The results obtained are as follows.
1) Concentrations of COD increase and those of N, PO₄-P and SiO₂ drop in the paddy field in the first half of the stage of the growing period of rice plants.
2) In the second half of the stage of the growing period of rice plants, concentrations of N and PO₄-P still drop, but those of COD and SiO₂ vary only to a very small extent.
3) Water quality of irrigation water changes mostly in ponding of the paddy field in process from inlet to drainage water.
4) When the concentration of nutrient salt is at a high level, it drops the paddy field, and when that is at a low level, it increases inversely.
5) In first half of the stage of the growing period of rice plants, nutrient salts are purified by immobilization to organic matter and those in second half of the stage of the growing period of rice plants are purified by assimilation of rice plants and absorption of soil.

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A practical technique is proposed for finding a set of quasi-optimum parameters, k and p, for two-dimensional overland flow, in which the relation between water depth, h, and discharge, q, is given by h=kq^p, in the kinematic runoff model.
First, the theoretical expression for the average water depth of rainwater flow over a slope is examined for the steady state of the flow under constant rainfall excess. The equation showing the relation between k and p is transformed from the above expression on the assumption that the average water depth is scarcely governed by the value of p. This equation can explain well the shape of the trough on the response surface of errors for sets of these parameters obtained through the analyses of flood runoff hydrographs.
Next, the practical identification technique is formulated utilizing the avobe-mentioned equation. This technique shows excellent results in computational time compared with the SP method which is one of the mathematical techniques for parameter identification.

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This paper deals with an experimental study on the creep of concrete during the early stage. In the experiments, the concrete was made using portland blast-furnace slag cement or fly ash cement or normal portland cement. Using spring-loaded creep test machines, the concrete specimens were loaded at three or seven days.
A summary of the results is shown below.
(1) The following relations on the mechanical properties of concrete were obtained; between splitting tensile strength and compressive strength, between Young's modulus in compression and compressive strength, between Young's modulus in tension and that in compression.
(2) The relations between the creep strain of concrete and the time since application of load were nearly expressed by linear lines on logarithmic graph paper.
(3) The specific creep of concretes during tension was greater than that during compression.
(4) Influence of age at the application of load on the specific creep of concrete was investigated.
(5) Both the specific creep and the creep coefficient were related to the strength of concrete.

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In this study, we consider the “hypothetical condition” that the water channels of the Tamagawa-Jyosui water system located at the Musashino platform in Tokyo provide the topographical conditions necessary for connection at extremely close range to the rivers in the platform. From this point of view the water channels will be able to accomplish this land conservation function as agricultural water facilities in the future, too.
To prove this “hypothetical condition”, site investigations have been performed for the 18 confirmed water channels in the sites. The properties of the water channel and river network systems were clarified as mentioned below by analyzing the survey data.
The data obtained by the site investigations are as follows:
1. Coupling length
2. Difference of elevation
3. Elevations at the upper and lower portions of the coupling line
A conclusion is obtained by analyzing these data.
In short, the water channels of the Tamagawa-Jyosui water system penetrate the upper stream portions of the rivers in the platform and the watersheds of these rivers provide the disposition conditions necessary for a stable connection to the topographical formations. Furthermore, the relation between each water channel and river is extremely close (14 rivers with less than 1 km of hypothetical coupling line among 21 rivers; accounting for 67% of all rivers, 17 rivers with less than 2 km; accounting for 81% of all rivers). Based on these conditions, the existence in the platform of the “naturally flowing water channel network system” is clear whereby water of the Tama River is able to flow to the upper stream portions of 21 rivers belonging to the three main water systems through the water channels of the Tamagawa-Jyosui water system.

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