Soil and Water Conservation for Desertification Control in Iran - Combating Desertification in Asia, Africa and the Middle East - page 362

• 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. From 37 sub-basins
in Iran, data from 24 of them were used for this study which covered more
than 37 million hectares. The results show that watersheds under study have an
average annual sediment yield of 750 t/km 2 and an erosion yield of 2,500 t/km 2 .

Keywords Desertification • Iran • Water conservation • Sand dune fixation •
Gully erosion • Landslides • Water spreading • Flood waters re-vegetation •
Sediment yield

1 Introduction

Desertification is acknowledged to be a complex phenomenon requiring the exper-
tise of researchers in such disciplines as climatology, soil science, meteorology,
hydrology, range science, agronomy, veterinary medicine, as well as geography,
political science, economics and anthropology. It has been defined in many different
ways by researchers in these and other disciplines, as well as from many national and
bureaucratic (institutional) perspectives, each emphasizing different aspects of the
phenomenon. A review of the desertification literature shows a great diversity (and
confusion) among definitions. This mix of definitions leads to miscommunication
among researchers, among policy-makers, and most important, between researchers
and policy-makers (see Chap. 1 ) .
Some researchers consider desertification to be a process of change, while others
view it as the end result of a process of change. This distinction underlies one of
the main disagreements about what constitutes desertification. Desertification-as-
process has generally been viewed as a series of incremental (sometimes step-wise)
changes in biological productivity in arid, semi-arid, and sub humid ecosystems.
It can encompass such changes as a decline in yield of the same crop or, more
drastically, the replacement of one vegetative species by another maybe equally
productive or equally useful, or even a decrease in the density of the existing
vegetative cover. Desertification-as-event is the creation of desert-like conditions
as the end result of a process of change. To many, it is difficult to accept incremental
changes as a manifestation of desertification.

2 Desertification and Soil and Water Conservation in Iran

Iran which has more than 75 million population is located between the latitudes 25 ı
to 30 ı N and longitudes 44 ı to 64 ı E, in the temperate zone and could be considered
arid or semi-arid.