Effect of the Length of the Streamflow Record on Truncation Level for Assessment of Streamflow Drought Characteristics

Abstract

The effect of length of streamflow records on truncation level (TL) and consequent drought characterization using streamflow data for a 50 year period at Banda (Ken river) and Nandghat (Seonath river) sites in India are studied. The study demonstrates the divergence in estimates of TL from different sets of data of various assessment lengths of duration and severity of independent streamflow drought events. TL for each 10-day (sum of 10 days streamflow volume) period during the year have been estimated as 75% of dependable flow value from corresponding flow duration curves prepared for datasets of various lengths and periods. A pooling procedure has been used to identify independent streamflow drought events. The study revealed that the estimation of TL using data covering fewer than 30 years shows considerable variations and may lead to biased estimates in TL values in the study basins. However, the estimates of TL derived from datasets covering 30 years or more are reasonably close to that of TL derived from 50 years of data, and the assessment for duration and severity of drought events are comparable. Therefore, data spanning 30 years or more should be used for realistic stream flow drought characterization.