The authors designed a new method for measuring percolation water in paddy fields. A cylinder which had no bottom, 15cm in diameter and 10cm in height was used for the purpose (Fig.-4). After setting the cylinder in the soil, a tip of the tube connected with Mariott glass tube (g) was inserted into the hole (i) of the cylinder. The water lost by percolation in the cylinder causes a drop of the water level in (i), which is automatically supplemented with water from (g). Diminution of water in the Mariott tube indicates the quantity of percolation water for that time required.
The merits of this method are ;
(1) Percolation can be measuerd rapidly and correctly. 10 minutes is enough for measuring at one point.
(2) Since the, water levels inside and outside of the cylinder are nearly equal while measuring, errors due to the difference in water levels are negligible.
(3) It is possible to measure the percolation water even in paddy fields into which irrigation water flows all the time.
The results which were obtained by this method in newly developed paddy fields on a diluvial plateau showed facts that there was much variety in the amount of percolation at different positions in the field. We assume that this phenomenon may be observed in any paddy fields. In order to improve paddy fields of lower productivity it is important to evaluate the positional distribution of percolation-rate in paddy fields. For this purpose the above method may be very useful.

抄録全体を表示

In Japan where agricultural farming is generally small and intensive, the cultivated fields are scatterd and the farmers are perplexed. To gather these scattered fields into some blocks is an urgent business for them. The land valuation is very important for the treatment of land gathering.
The Department of Agriculture and Forestry of Japan now expects that the replotting of arable land is performed not proportional to the area but to the land valuation and the cost of construction is imposed upon a person according to his land's value.
The land is evaluated by the topographical or micro climatographical condition such as the soil of tilth, the convenience of the irrigation and the drainage, the slope, the shape, the length of sunshine, the ventilation, and the distance etc. The author investigated the real condition of the arable land readjustment in Chiba, Ibaragi, Kanagawa, Nagano, Niigata, and Iwate.
After author's investment, it have been clearified that in many place, the land valuation was out. Here many farmer said that it was too complicated and troublesome. But in some rare case, the replotting was proportional to the land valuation. And to their treatment, there was some farmer who's own land was forced to decreased about 1000m². It is shown in Table 9, 11. Farmers were grumbling and not contented with the results. They also said that it was inclined to be influenced by the boss' s opinion. The author considers that the treatment of replotting and the share of the cost of construction must be principally proportional to the area.
And the land value should be used only in the liquidation cost of replotting, the treatment of land valuation must be simple and must be acceptable to farmers.

抄録全体を表示

In the last report, the development of the turbulent boundary layer was analyzed theoretically. In this paper, theoretical results were compared with experimental results.
The boundary layer thickness which developed from the side wall and channel bed was determined by the measurement of velocity distribution through the cross-section, and thus the process of the boundary layer development was clarified for some channels. The data obtained by the test in the channel which has a uniform section (in the state of sub- and super-critical flow) and those data which have been shown by Mr. W. J. Bauer, Mr. J. W. Delleur and Mr. Y. Iwasa agreed with calculated results quite well.
When the depth is smaller than one half of the channel width, it was found that the boundary layer thickness which developed from the bed was constant after it reached the water surface, but the distribution of transverse velocity still continued to change.
The process of its development agreed with the calculated result.
As an exponent of the power law changed along the stream in the divergent channel, calculated results did not coincide with tested data well, but both results showed the similar tendency that the boundary layer developed rapidly as compared with the case of uniform flow.

抄録全体を表示

In order to represent the boundary condition of the seepage surface in the electrical analogue method, the author divided the seepage surface into 20 small pieces, and gave each of them proper electric potential by a potential divider (Fig. 3). The arrangement of experiment becomes quite easy by this method.
The flow and the distribution of potential will change with the following value ;-e_n= (v_n/V-h_n/D) whereV = electric potential difference between the bottom of ditch and ground surface. v_n=-potential of the n-th small piece from the bottom of ditch. D = depth of ditch. h_n= height of the center of the n-th small piece.
To every small piece, such v_n is given that every e_n of the piece may be equal. In case of equidistant ditches which reach the impervious substratum, the relation between flow and e and number of small pieces is given as Fig, 4 shows. When the number of small pieces is few, e =0 is not always appropriate. The most appropriate value of e may be dicided by Fig. 4 for a certain number of small pieces. The inversion between potential and stream function may easily be made as shown in Fig. 5, too. According to such an example of experiment as shown by Fig. 6, the experimental value coincided with the theoretical value very well.

抄録全体を表示