PROBABILITY MODELING OF LOW FLOWS AT DIFFERENT SITES OF INDUS BASIN IN PAKISTAN USING L-MOMENTS AND TL-MOMENTS

Abstract

At-site Frequency Analysis (ASFA) of low flow was carried out for nine sites ofIndus basin in Pakistan. In the present study, 10-day annual low flow series were analyzed by robustestimation methods such as Method of L-moment (ML) and TL-moment (MTL) to identify best fitprobability distributions for each site. Best distribution for each site was identified using differentgoodness-of-fit Tests (GFT). No single probability distribution was declared as the best-fit distributionfor all sites included in the plan. The GFT results indicated GPA was the most appropriate distributionfor most of the sites followed by GLO and GEV distributions. On comparison, it was found that formost of the sites ML was best estimation method and for others MTL. For ASFA, the quantiles of bestfit distribution were also estimated. It was found that estimated low flows based on fitted distributionwere in close agreement with observed flows.