Method for correction of annual precipitation records using the water balance approach*

Precipitation gauge measurements suffer from several sources of errors which can strongly influence their accuracy. The method proposed in the paper is based on the correction of annual precipitation records for a given river basin using the water balance equation. The main advantage of the approach is in using the annual runoff records and air temperature data, which are measured more accurately than the annual precipitation amount. Two versions of the computation scheme (for a multi-year period and for an annual interval) are presented and discussed. The water balance equation taken into account in this study combines the area averaged annual measured precipitation, runoff, evapotransporation and, over an annual time scale, the change in moisture in surface and undersurface storages. The Ol'decop formula for calculation of evapotranspiration together with the improved regional formula for potential evaporation as a function of annual air temperature is used in this study. It has been determined for the annual time interval that the storage of water in a basin is strongly dependent on annual air temperature and, to a lesser extent, on precipitation. An example of the method application for two catchments situated in Northwest Russia is presented, too.