# Shifting of Meteorological to Hydrological Drought Risk at Regional Scale
## 1 Introduction  
Drought is a condition considered as the deficit of water, including surface, ground, or atmospheric water, for a long period [1]. Irrespective of climatic sites, the drought could occur worldwide even in humid and wet environments [2]. Drought is generally classified into meteorological, hydrological, socioeconomic, and agricultural drought [3]. Among these four types of droughs, hydrological is the most important form as sustainable water resources management is heavily dependent on hydro-meteorological information. Various numbers of factors are associated with the onset of hydrological drought, and meteorological drought is one of the main influencing factors. The root cause of drought onset is the deficiency of rainfall across a large area for a very long period and is notated as a meteorological drought [4]. A meteorological drought can develop quickly because it is primarily caused by a lack of precipitation [5], and if the lack of precipitation spreadsto specific regions, the meteorological drought can be transformed into a hydrological drought, and then into an agricultural drought. The drought propagation process refers to the transition of different types of droughs. The relationships between different types of droughs are studied by several authors, for example, [6] resulted that hydrological drought events occurred approximately seven months after meteorological drought events. The streamflow drought can be investigated using meteorological drought information at the annual time scale [7]. The interrelation-ship between runoff and meteorological drought has also been investigated and it was concluded that the significant dependency of hydrological drought on meteorological drought [8]. The impact of meteorological forcing on hydrological droughs has been computed [9]. A copula-based joint meteorological-hydrological drought index has been used to model the relationship between meteorological and hydrological droughs upstream and downstream of the Kasilian basin [10]. The transmission of meteorological droughs to hydrological droughs and the influence factors have been explored and investigated [11]. The entropy theory was used to create a hybrid drought index that combines hydrological, meteorological, and agricultural data and was used to investigate the drought condition in Northwest China [12]. In literature, the relationships between hydro-meteorological droughs, climatic variables, and human activities were also explored [13; 14]. For example, [15] examined the relationship between various hydrologic and meteorological drought indices considering natural and human factors for different basins in the contiguous United States. Similarly, [16; 17; 18; 19] studied the dependence structure between meteorological drought and hydrological drought using different approaches and resulted that the occurring time lag between meteorological and hydrological droughs is critical for sustainable drought management. Most studies in the literature focused on determining hydro-meteorological drought and drought propagation; however, it remains unexplored. Besides that, the lack of understanding considering hydrological drought response to meteorological drought in different regions raises an unanswered question for basin-scale drought risk management [20]. To find answers to these questions, a comprehensive study of droughs that span multiple geographic areas and last for extended periods is required. Strategic water resources can be implemented more efficiently with accurate water-based information based on regional drought characteristics. Furthermore, given Pakistan's erratic, scarce, unstable climate and current drought situation [20; 21; 22; 23; 24; 25; 26; 27; 28; 29], drought propagation information is critical at the regional and national levels, as it can provide the appropriate and consistent information required for efficient water management and drought early warning systems.