This thesis covers the breakdown of the methods to clear roots by rakedozer and the findings of survey and tests carried out of the volume of roots cleared by rakedozer in one operation in the field for mechanical reclamation ; which are outlined as follows;-
(1) For survey/testing of the clearing of roots were adopted 5 methods of stump pulling, full scale, scattering, temporary clearing line and mixture. Their conditions and merits are shown in Table 3.
(2) The volume of roots cleared by rakedozer in one operation was surveyed/tasted by the process divided into “the last speed forward” and the “2nd speed forward”. The results are shown in Tables 1 and 2. The average value obtained from it, as shown in Table 4, is taken to be the standard value of the volume of roots cleared per rakedozer in one operation.
(3) The volume of roots cleared by rakedozer in one operation was studied from the aspect of weight of roots cleared, the results of which are shown in Table 5. The relation between the area of rakeboard and the volume of roots cleared is shown in Table 6.
From these table it can be observed that it is convenient to use a large-sized rakedozer and there is further room for developing the rakeboard.

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In regional low level paddy basins, that depend on pumping drainage, it is necessary to, increase daily drainage efficiency so that pumping facilities can be maintained properly.
The present author proposed the concept “ordinary drainage discharge (ODD) ” and conducted an experiment based on the above concept to explain daily drainage mechanisms. If pumps are designed in conformity with data on the ODD, a stable stream-flow will be obtained and they will be maintained economically. The ODD that is defined as the highest value in frequency distribution must be applied to the design of pumping drainage.
It has been confirmed by the results of frequency analysis that the frequency distribution of drainage discharge generally coincides with Pearson's frequency curves of I type in the irrigation season and his frequency curves of III type in the non-irrigation season. The ODD can be calculated theoretically as the maximum ordinate (mode) in the frequency curves.
In carrying out this study, Shinkawa area was chosen as a model area because a lot of useful information was available there.

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The present author has had an idea to use the ordinary drainage discharge (ODD) obtained through frequency analysis for the design of pumps, especially for the determination of their capacity.
This paper aims at proposing that the design ODD should be used as one of the most important design factors for estimating the capacity of pumps and the number of pumps to be used with respect to a certain value of design flood discharge.
It has been concluded that the following formlae (1) are most reasonably applied to the calculation of pump capacity,
_??_(1)
where, Q_d: design flood discharge, Q_s: ODD in irrigation season, Q_w: ODD in non-irrigation season, Q_r: a value determined by the values of Q_s and Q_w, A₁, A₂, A₃: number of pumps, A₁', A₂', A₃': integers coresponding to A₁, A₂ and A₃ respectively and either equal to or smaller than A₁, A₂ and A₃ or zero.

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The cource through which dam water leaks, the structure of water peameation and in particular, the condition of each seapage route are difficult to detect. However, these are indispensable to judge the necessity of leakage prevention work of dams and to plan how to execute work.
This paper presents a method of investigating leakage of dam water by a radioactive tracer and the results of field tests for ascertaining its applicability.
Iodine-131 was chosen as a tracer and Lapidus-Amundson's equation was chosen as a theoretical solution based on the results of detailed basic examinations. However, the soltion is not readily applied to field tests, because it has six unknown terms.
By introducing parameters as shown in Equation 4 and 5 and by applying the “two-nomogram method” as shown in Fig. 4 and 5, analysis has been made possible. It is obtained by simply superposing a detected pulse on the nomogram, assuming only a loss parameter which has been found to have a nearly uniform value according to the results of the basic test. These procedures permit analysis of pulses divided into superposed single pulse. Therefore. it has become possible to analyze pulses appearing many times in an observation well, and the complex shape of elution curves, which are difficult to analyze by conventional theoretical solutions. By applying the operation, the mean velocity, the axial dispersion constant, the tracer volume at the time of injection can be decided for each detected pulse.
By applying the results of experiments conducted by Ebach-White and Hubbert to the values of these factors the mean grain size and the coefficient of permeability, which are indexes of the permeation structure of an aquifer, can also be obtained.
On the other hand, the three-dimentional distribution of a flow of each tracer can be detected from the disposition of observation wells and from the continuous measurement of the vertical distribution of concentration in each well.
The detailed behavior of a three-dimentional flow of underground water as well as a flow in each seepage route may be actually proved by all-round inspection of the behavior of each pulse, the permeation structure of each well, and the three-dimentional distribution of a flow of each tracer.
A field test was carried out at Sanuma dam. A swampy paddy field exists about 100 m downstream of the dam. The field appears to be supplied with water from a spring. Satisfactory results were obtaind by the proposed method as shown in Fig. 9 and Table 1. It was found that the swampy paddy field was supplied with water leaking from the bottom of the reservoir as shown in Fig. 10 and the relationship between the amount of leakage of water and the level of reservoir water was made known as shown in Fig. 11.

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A well function which has been used as a theoretical base in a nonequilibrium pumping test is based on the approximation of a pumped well by mathematical sink. It can not be cosidered to be representing well characteristics perfectly. The presentauther envisaged the well which was provided with the following three characteristics as the most generalized well. They are an inflow radius a storage effect and an inflow resistance of the well.
An equation expressing a lowering of ground-water level was obtained under the condition that such a well was dug in an infinite uniform elastic aquifer and ground-water was pumped up from it at a constant rate.
From the result of numerical calculation of the equation, it was confirmed that at the initial stage of pumping, well characteristics had an important effect on a lowering of ground-water level in the aquifer. With the lapse of time, its influence diminished till a lowering could be expressed by the well function. However, in a lowering of water level in a pumped well, the influence of inflow resistance did not diminish with the lapse of time.
The effect of partial penetration of a well was also investigated. It was found that partial penetration of a well had a great influence on a lowering of water level in a pumped well.

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In the previous paper, the general influence of well characteristics was diagrammatically. investigated. In this paper, the effect of each parameter representing one well characteristic on a lowering of water level-time curve was analytically considered. As a result of this investigation the present auther has come to the following conclusions:
i) Immediately after the begining of pumping, well characteristics, namely, storage factor a and inflow resistance R have a great effect on a lowering of water level-time curve.
ii) After a considerable length of time elapses, a lowering of water level may be divided into two parts; one containing only aquifer constants known as a well function and the other expressing the well effect. In the case of a lowering of water level in an aquifer, it has been found that the latter decreases with the lapse of time, but in the case of a lowering of water level in a well the same does not hold. From this result, it has been found that an aquifer essentially differs in a lowering of water level from a well.
As it has been found that the well effect disappears with the lapse of time in a lowering of water level in an aquifer, the applicable limit of the well function has been derived from this result on the assumption that the range within which relative deviation from the well function does not exceed 1/100 is only applicable
Finally, a pumping test carried out on the spot is quoted as an example and the properity of these theoretical treatments has been confirmed by this example.

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A recovery test is widely used as a simple aquifer test. Though recovery of water level in a pumped well is greatly affected by well characteristics, they have been neglected in recovery tests. Therefore, in this paper the method of recovering water level is investigated with well characteristics taken into consideration.
First, it is discussed that well characteristics as mentioned in the previous paper are approximately expressed by a single parameter α'. And a recovery curve of a lowering of water level with well characteristics taken into account has been derived from the result of analysis of pumping at a constant rate. From this the following conclusions have been reached:
i) The s-log (t/t-t0) curve does not take a liner form as obtained from the well function, but takes an S-shaped form when well characteristics are taken into consideration.
ii) For a constant pumping time, the amount by which a recovery curve deviates from the straight line obtained from the well function increases with an increase in the value of C', where C'=α'/ 2S is a storage factor.
It has been found from the above-mentioned that in order to obtain a correct value of transmissibility, we should use the gradient of s-log (t/ t-to) curve at the limit of t→∞.
Finally, it has been confirmed by the recovery curve obtained in a pumping test carried out previously that the treatment mentioned above is proper.

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The method of determining aquifer constants by measuring a change in water level in a well after a known volume of water is poured into it in an instant is the simplest method of aquifer tests. Though a method making use of a single well is greatly affected by well characteristics, the effect of well characteristics has been neglected in ordinary methods.
The present auther took up the study of a well provided with three characteristics comprising an inflow radius, a storage effect and inflow resistance, and analyzed a change in water level after instantaneous pouring of water. The following have been revealed from the result of the analysis:
i) The equation which was used by Ferris et al. is applicable only when nondimensional time θ= Tt/Sa² is very long, and it cannot be used for practical purposes.
ii) Cooper et al. treated this problem in disregard of inflow resistance in well characteristics, but the effect of inflow resistance is too large to be neglected.
iii) On the other hand, if inflow resistance is approximately expressed by the effective radius, well characteristics can be expressed by a single parameter C'. Conseqently the analytical result obtained by Cooper et al. apparently coincides with the s_w/ s₀-t curve. And if inflow resistance is unknown and the method proposed by Cooper et al. is applicable, the correct value of T can be obtained but that of S cannot be o btained substantially.
Finally, the applicability of this method was examined on the spot and it has been found that this method is the simplest and most prtactical for determining the value of T.

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