Spatial propagation of different drought types and their concurrent societal risks: A complex networks-based analysis

Abstract

This study proposes a novel complex networks-based framework to examine the spatial propagation of one type of drought to another (concurrent droughts) in a region and the associated risks. The methodology involves two major steps: (1) Analysis of drought connection patterns using spatial networks of different drought types in a region, using event synchronization and network measures; and (2) Building concurrent drought risk networks to identify smaller-scale (district-level) homogeneous drought risk communities. Meteorological, agricultural, and hydrological droughts as well as hot events are considered for developing the methodology. The proposed method is implemented to study droughts in Peninsular India, a water-stressed region that often witnesses intra- and inter-basin conflicts during drought periods. The results indicate that drought sources of all types and severity are located primarily on the high-altitude divides of river basins. This finding has great significance, since any drought occurring at a source could hint at a forthcoming event in the connected locations. Analysis of the distances of drought connections reveals that meteorological droughts are more localized when compared to the other drought types and that the distances increase with severity levels for all drought types. Furthermore, based on the construction of a correlation-based concurrent drought risk network (using a copula-based multivariate drought index), seven distinct communities of districts are demarcated. The network thus formed is found to inherently capture the topographical and rainfall pattern along with the socio-economic aspects existing in the area. Therefore, the communities detected could facilitate devising appropriate drought mitigation strategies.