Investigating Meteorological/Groundwater Droughts by Copula to Study Anthropogenic Impacts

Abstract

A critical understanding of the water crisis of Lake Urmia is the key in this paper for a basin-wide investigation of its Meteorological (Met) droughts and Groundwater (GW) droughts through a data-driven modelling strategy using 21-years of data records. The challenge is to formulate a modelling strategy to discern anthropogenic impacts and resilience patterns. The strategy includes: (i) transforming the recorded timeseries into Met/GW drought indices; (ii) extracting their drought duration and severity; and (iii) deriving return periods of the maximum drought event through the copula method. Our strategy is heuristic and its novelty emerges from deriving return periods for both Met and GW droughts to discern anthropogenic impacts on GW droughts. The results underpin the need for a planning system yet to emerge for mitigating impacts and rectifying ongoing damages before they become irreparable. The collective outcomes of the results and our professional knowledge shed light: on the ways resilience in the basin is undermined in terms of subsidence problems, on impacting the environment by altering interconnectivities between the lake and watercourses, and on discerning the causes for aquifer depletions to be due to mismanagement but not of Met droughts. Already, migration from the basin area can be detected.