PRECIPITATION INTENSITY-DURATION-FREQUENCY FUNCTIONS FOR THE BANNU REGION NWFP PAKISTAN

The function of precipitation intensity-duration-frequency is needed for the planning anddesign of water resource projects. short duration precipitation data are hardly available. hovever thetotal hourly-recorded available precipitation data for different parts of nwfp fronl differentdepartnlents have been collected and analyzed for the present study. the data from wapda is foundto be ltiore authentic. making use of the data, functions of intensity-duration-frequency forprecipitation are developed for the bannu region, representing the lower hilly and plane areas innwfp. the idf curves are plotted for 2, 5, 10, 25, 50 and 100-year return periods. the theoreticalintensities of precipitation calculated by the developed functions are in close agreement 'vvith thoserecorded at the stations through automatic gages. only 7 0a> variation is observed for ltiost of the time.the values of the constants k, b and exponents n, m in the idf function 1==ktn/ are/(t+b)lticalculated from the observed precipitation data. the correctness of the developed function isascertained through its coltiparison with existing equations for depth duration developed for thevorld's largest rainfall events. the function developed is found to produce nlore realistic results forregions in nwfp. the developed function may be used in the sanlc region in a radius of about 100knl. for design practices regarding the prediction of precipitation in the future, instead of consulting26 years of data available for the sanlc region on hourly basis.