The Effects and Consequences of Climatic Drought on Time Delay and the Change in Water Discharge of Springs and Qanats (Case study: Yazd - Ardakan Plain)

Drought is a natural event its impacts are more sever in arid and semiarid regions. Water resources are the first area being affected by the drought Therefore it is important to do researches and investigations in this field, and to explore the delay between climatic and hydrologic drought in order to achieve better management on ground- and surface-water resources and to reduce drought damages or in other words to manage the drought risks. In this study by examining the consecutive periods of climatic and hydrological drought using two drought indices of SPI and GRI in Yazd - Ardakan plain, central Iran, the delay time between climatic and hydrological drought were identified. For studying the characteristics of climatic and hydrological drought, long-term data (1980-2010) is used from rain-gauge stations and from discharge stations for the Qanats in plain, in hillslopes, and mountains as well as recent data for springs in the area (2001-2010). Results showed an increase in drought intensity and persistence of climatic and hydrological drought, particularly in recent decades such that the climatic drought in recent decades occurred in a frequency 4 times of that in the past four decades. The results also indicated the existence of different time delays between the climatic drought and its impact on discharge of plain, hillslopes, and mountains Qanats and springs. So that the delay in the mountainous Qanats, depending on the severity of the drought and the type of Qanat, usually is less than 1 year. This is less than 2 years for the Qanats in the plain. The results of this study warn about 2-year Crisis Management after each period of drought in Yazd Plain.