Investigation of Rainfall Variability for Pakistan

Abstract Pakistan is an agricultural country mainly dependant on irrigation through the Indus water system. The country has developed the world’s largest contagious canal network. Monsoon precipitation is the lifeline of Pakistan which not only caters the national power supply and standing crops water demands but help gathers the reserves to meet the requirements of low flow period in the next 4-5 months. Future projection of weather indicates towards the dry land agriculture for Pakistan. The purpose of the present study was to investigate and analyze the variability in precipitation occurred in the past times. Rainfall variability coefficient is utilized to analyze the past time situation and the study covers the period from 1960-2009. The results of the decadal analysis showed that the high value of the variability coefficient has been observed in Balochistan (251%), Sindh (247%) and Punjab (208%) regions. However the annual analysis showed the increasing trend of variability coefficient from North to South in Pakistan. According to the inter seasonal analysis of fifty years data (1960-09) variation in the coefficient of variability was highest in post monsoon and pre monsoon seasons as compared to the winter and monsoon seasons. These analysis showed that forecasting is a challenging job for the forecasters where the variability is prominently high. It revealed in the study that most of the northern areas have safeguarded except in the post monsoon period. While the southern half has been suffered throughout the year in terms of rainfall variability.