Regional climate change scenarios and their impacts on water requirements for wheat production in Iran

Document Type: Research Paper

Authors

1 Department of Geography, Golestan University, Gorgan, Iran.

2 School of Geography, Archaeology and Environmental Studies, University of Witwatersrand, South Africa.

Abstract

We simulate the effect of climate change on water requirements of cold season
wheat in various climatic zones of Iran. The research considers both observed
climate (temperature and precipitation) changes during recent decades (1960-2009)
based on instrumental records and projected future changes to 2100 based on the
MAGICC/SCENGEN 5.3 compound model. 20 General Circulation models are used
based on a single scenario known as P50, which is the average of SRES or emission
scenarios. Results indicate that whilst winter precipitation has marginally increased
across the country as a whole, a significant decline in mean spring precipitation is
recorded between 1960 and 2009. However, considerable variability in trends is
measured across various climatic regions of Iran. Mean annual temperature / rainfall
changes in the various climate zones of Iran for the period 1960-2009 follow: +0.1 °C
/ decade / +0.43 mm / decade in arid regions, -0.1 °C / decade / -1.7 mm / decade in
semi-arid regions, +0.1 °C / decade / -1.33 mm / decade in Mediterranean / semihumid
regions and -0.01 °C / decade / -0.04 mm / decade in humid / hyper humid
regions. Temperature projections to 2100 indicate an overall temperature rise of ca.
4.25 °C relative to that for 1961-1990, with increases projected for all climatic
regions of Iran. Despite an overall projected mean precipitation increase of 36% for
the year 2100, relative to that for 1961-1990, these are insufficient to compensate for
temperature increases. Consequently, calculated water deficits during the growing
season (autumn to spring) in Iran’s wheat producing areas are expected to increase
from 5.2% in 1980 to over 23% by 2050 and 38% by 2100.

Keywords