Assessment of drought and wet projections in the humid climatic regions for Pakistan

Abstract

Investigation of extreme hydrological events are necessary for planning and designing hydrological structures. In this study, we examine and project two hydrological extremes of drought and wet conditions over the north and eastern regions of the country. A statistical procedure of the Reconnaissance Drought Index at the annual time scale was used to combine the monthly rainfall and temperature data for the assessment of extreme drought and wet events. These hydrological extreme events were combined with Index-Drought Procedure using L-moments to obtain study results. Homogenous regions were satisfied for both the extremes based on statistical measures. Two statistical tools were used to select suitable probability distributions in the form of Generalized Pareto and Pearson Type-III distributions to discuss drought risk and wet conditions in the regions. Secondly, regional projections of drought risk and wet conditions were performed based on regional quantiles at different interarrival periods which show greater chances of the wet condition in region one while drought risk in region two. Lastly, at-site projections were carried out for all the included sites for both extremes at various interarrival periods using the suitable probability distributions. Both at-site and regional projections show greater similarity at lower while uncertainty at higher interarrival periods. As droughts and wets cover, a large area, therefore, regional results are more functional and better for regional planning and development programs. These statistical projections will help planners of water resources management and hydrological extremes in the study area.