Using drought indices to assess climate change impacts on drought conditions in the northeast of Iran (case study: Kashafrood basin)


M. Bannayan, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box 91775-1163, Mashhad, Iran. E-mail:;


Drought has significantly affected environmental and socio-economic conditions in Iran. In this study three drought indices were used for monitoring drought intensity and duration in the Kashafrood basin (northeast Iran). The standardized precipitation Index (SPI), Precipitation Index Percent of Normal (PNPI) and Agricultural Rainfall Index (ARI) were calculated for the base period (1990–1961). All these indices were used to assess future drought events in the Kashafrood basin under climate change attributed to low and high greenhouse gas emission scenarios (SRES B2 and A2, respectively) for three periods (2010–2039, 2040–2069 and 2070–2100). Projected changes in precipitation, temperature and potential evaporation were simulated by statistical downscaling of HadCM3 outputs. The main results showed: (1) slight increase in precipitation means, around 2.2–5.4% under the A2 scenario and 6.8 and 8.6% under the B2 scenario: (2) slight increase in maximum temperature, around 4.6–5.6 °C for the A2 scenario and 4.25 and 4.6 °C under the B2 scenario; (3) slight increase in minimum temperature, around 1.6–1.9 °C under the A2 scenario and 1 and 2.23 °C under the B2 scenario, and, (4) higher drought frequency associated with global warming was demonstrated by all indices under both scenarios. Such an increase in drought frequency would have major implications for natural resource management, water security planning, water demand management strategies and drought relief payments. Copyright © 2012 Royal Meteorological Society