STUDY OF ANNUAL PRECIPITATION AND ITS RELATIcr4SHIP WITH MODULE IN KARAJ WATERSHED

In Water resources projects knowledge of hydrological parameters is
required. Some of these parameters depend on the volume of water designed
for those projects.
In order to obtain a better yearly precipitation mean for Karaj
watershed, an attempt is made to homogenize the records of the various rainfall
stations, using stations having longer recording periods. Efforts are
also made to determine the relationship between rainfall and altitude. As a
result of knowing the hypsometeic curve and variation of rainfall with
altitude the best value of watershed rainfall is computed. Finally considerlng
the correlation between annual rainfall of the watershed and its module
it is possible to study the relationship between the two. The regression
line with different probablity values related to each deviation is also
given.
To get a more precise estimate for the annual rainfall in Karaj
watershed, the establishment of rainfall recording stations in high altitudes
occupying a higher percentage of the area is necessary.
In this study, a great effort is made in the analysis of the available
data according to the statistical methods. However, it should be emphasized
that a more accarate analysis requires more measurements of runoff and
especially rainfalls, in different times and locations.
* Assistant Professors of Irrigation and Reclamation Dept. College of
Agriculture , University of Tehran.