Soil and Water Conservation for Desertification Control in Iran - Combating Desertification in Asia, Africa and the Middle East - page 363

Only a small part of the country is humid, the annual precipitation throughout
the country is about 250 mm. Eight percent of the country receives between 500
and 1,000 mm of precipitation annually. The maximum temperature during summer
ranges from 34 ı C in the north to 50 ı C in the south. Most parts of the north and
center of Iran receive snow during winter and temperature drops below freezing
point. More than 90 % of the land area in Iran is classified as arid or semi-arid.
Of the 164.8 million hectares (Mha) of whole area of the country, the mean annual
precipitation of the 87 Mha of the mountainous regions and 77.8 Mha of the plains
areas are 365 mm and 115 mm, respectively. Approximately one-half of Iran's
water supplies come from surface waters, with most of the remainder coming from
groundwater aquifers which are significantly over- drawn. Therefore, drought is an
ever present threat to most of Iran.

2.1 Distribution of Deserts in Iran

Even though there is a variation in reports on the exact area of deserts in Iran,
because of different definitions; some real estimations showed that, at the present
the area of desert regions and sandy lands is estimated to be 34 Mha (5 Mha active
and 12 Mha inactive sands and remaining areas is salt accumulation lands, saline
and alkaline soils, gravelly lands, etc.) The eastern part of the plateau is covered
by two salt deserts, the Dasht-e Kavir (Great Salt Desert) and the Dasht-e Lut
(Fig. 18.1 ). Except for some scattered oases, these deserts are uninhabited. The
area of the degraded and desertified rangelands is atleast 16 Mha but according
to some assessments it could be as high as 50 Mha. To more accurately determine
the area and status of the degraded rangelands will require an integrated survey to
delineate and map Iranian rangelands and deserts, to get actual numbers and provide
a baseline against which future changes can be assessed.

2.2 Land Degradation, Nature and Extent

Although agricultural activities and land use in Iran have a long history (from
about 7,000 years B.P.) and despite of huge deterioration caused by soil erosion
and flood there are some documents that show that increasing soil erosion is an
outcome of land use practices in the recent century. The first comprehensive report
of soil erosion, water and soil conservation was provided in English by FAO experts
in 1958.
There is no accurate estimate of soil erosion in different parts of Iran. But
20 years records from 120 gauging stations were examined to evaluate soil erosion
and sediment yield in some watersheds in Iran (Jalalian et al. 1997 ) . From 37 sub-
basins in Iran, data from 24 of them were used for this study which covered more
than 37 million hectares. The MPSIAC method, which uses nine factors including