Abstract
From a hydraulic view point, this paper deals with the conditions of uniformity for water allocation in a paddy field pipeline system.
First of all, as an example of this problem, hydraulic analysis was carried out on a paddy field pipeline system 443 ha in area on the coast of Lake Biew. The analysis revealed that the quantity of discharge from each hydrant at each paddy field plot was quite different, such that the maximum was several times the minimum under the same conditions.
Secondly, in order to clarify the characteristics of ununiformity of the discharge from each hydrant, hydraulic analysis was also carried out on several types of model pipeline systems having different area, slope, and discharge of water. The simulated results obtained qualitatively revealed the effects of these factors.
Thirdly, when 10% of the hydrant valves were fully opened, the effects on other hydrant valve pressures were simulated. This simulation showed that if the area of the block was 100 ha or over, the standard deviation σ of the discharge from each valve was 10 times that in the case of the uniform valve constant. However, when the block area was smaller than 100 ha, σ gradually become smaller. Therefore, it was clarified that the uniformity of discharge is dominantly affected by the block area of the allocation system.
The above-mentioned results provide very usefull knowledge for the design of pipeline systems and the management of irrigation water in order to maintain uniformity of discharge in each hydrant.
