Abstract
Of rate, demand for industrial and city water has remarkably increased, and the effective utilization of available water resources and a large scale development covering multiple river systems for supplying water are some of the urgent subjects to be executed.
In this study, the annual minimum moving average rainfall of n days (Rj (n)) was obtained based on the observations from the principal observatory points in Kochi Prefecfure and some review were given to obtain the results stated below:
a) Rj(n)at the principal observatory points in Kochi Prefecture shows a nearly linear distribution in the Weibull probability paper.
b) No tendency change can be observed in the secular change of Rj(n).However, within such short, period of ten (10) years, its average values indicate variation and are not always constant.
c) Rj(30) shows nine (9) years of periodicity in the level of significance of 1% while seven (7), nine (9) or sixteen (16) years of periodicity in the level of significance 5%. Other Rj(n)does not show any periodicity.
d) In the correlation coefficients between Rj(n) and minimum discharge per year, drought discharge and low water discharge, the coefficient at the time of n=30 is maximum and is about 0.7 However, in the correlation coefficient between Rj(n) and discharge corresponding to n days of the moving average when daily discharges are ordered according to quantities starting small quantity, it has been found to indicate an extremely similar variations within the range up to n=100.
