反復利用を考慮した水田用水の期別必要取水量に関する研究

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In this paper, the authors have investigated a fundamental theory for planning of seasonal water requirement for paddy field,improving the Critical Block Method (hereafter CB Method). Then to verify the effectiveness of the theory, they applied it to the YAHAGIGAWA water use district,which is located in Aichi Pref.. Main results obtained are as follows; 1. Improvements in the block-kind judgements of the CB Method (Chap. 1 and Chap. 9 ) . The block-kind judgements in the CB Method become difficult and complicated as the blocks increase number. The authors succeeded in working out these problems, by separating judgement into two parts: divisional judgement (D-judgement) and quantitative judgement (Q-judgement). D judgement is the means for calculating water quantity of divisional and returned flow under a part blench canal. It is done independent of other areas. Q-judegement is the means for caluculating water requirement in a whole area,under considering the results of D-judgement. In the actual process of planning, the block-kind judgement are done easily, correctly and swiftly. 2.Proposition concerning the fundamental theory for planning of seasonal water requirement (Chap.2, Chap. 7 and Chap. 8). The CBMethod has been proposed for calculating maximun quantity of water requirement for a paddy field. Therefore , when we nead seasonal quantity of water, the necessary fundamental theory is insufficient. In this report; we proposed the general idea for planning that has been summarized in the coefficient of seasonol demand quantity <special>(fı)</special> and coefficient of seasonal repeating quantity <special>(rı)</special>. The former is expressed in the equation (2-4) and the latter is expressed in the equation (2-11). If we multiply <special>fı(or rı)</special>, by water requirement in depth and paddy field area, we can obtain seasonal demand quantity (or seasonal repeating quantity) in each block. 3. Estimation of the saved quarity by repeated use (Chap. 10). Applying the above described theory to the YAHAGIGAWA water district, we estimated the saved quantity by repeated use. Generally, repeated use is divided into two types, in one brench canal area and among mary brench canal areas. In the YAHAGIGAWA water district, repeated use saved 24 percent of water requirement on the average. Then,in the quantity of water, repeated use in a brench canal occupied about 38 percent and among many brench canals about 62 percent (Table. 10-5). Especially, the percentage was the highest during from June 16th to 30th and from August 1st to 1Oth, about 30 percent (Table. 10- 5). 4. Comparison of the practical data with calculated results on the quantity of water requirement. The practical date during non-rainy days from 1973 to 1979 was compared with D-judgement and Q-judgement results. Consequently, the seasonal pattern calucuated shifted foward about 10 days (Fig.10-2). This is explained by the fact that the rice-planting season has been moved in foward recent　years. Considering this gap,the puantity of Q-judgement was 59 percent and D-judgement was 84 percent of the practical data. Thus, it becomes clear that repcated water use had deep significance for the water requirement in this district.

反復利用を考慮した水田用水の期別必要取水量に関する研究

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