Assessment of meteorological, hydrological and groundwater droughts in the Kashmar and the Bardaskan plains and their relationship with each other

Drought is one of the most complex natural hazards that affect natural systems and different parts of an ecosystem in various ways. Evaluation of drought behavior such as determining the time of its occurrence, understanding the relationships between types of drought, and recognizing its characteristics such as magnitude, severity, and duration of drought periods can be an important aid in water resources management. This study was conducted to determine the meteorological, hydrological, and groundwater drought characteristics and the relationship between their occurrence using SPEI, SDI, and GRI indices over a period of 29 years (1987-88 to 2015-16) of the Kashmar and the Bardaskan plains. According to the results, in general, the occurrence of meteorological, hydrological, and groundwater drought in the region is increasing. The increase in drought events is quite evident in the groundwater drought. The highest correlation coefficient of drought types with each other is related to SPEI and SDI indices in return periods of less than 3-months and SPEI and GRI indices, with a return period of 6-month, which indicates a slight association of meteorological droughts with hydrological and/or groundwater droughts in the region. In general, the correlations between SPEI with GRI, and SDI with GRI are not significant at a 95% level of significance. It can be mentioned that there is no significant relationship between groundwater drought and hydrological drought or meteorological drought in the study area. Therefore, it can be stated that groundwater and hydrological drought are affected by factors other than meteorological drought (and precipitation). The continuous decrease of groundwater level in the study area can be another reason for this remark. Also, the study of drought characteristics showed that in the short scales, the GRI index is more intense than other indices and the most deficiencies were identified by the SPEI index. It is suggested that the effect of extraction from surface water and groundwater resources on the quantity and quality of water resources be further investigated.