مروری بر نرخ فرساش آبی و تولید رسوب در ا یران

Despite the relatively long history of erosion and sedimentation studies in Iran, a large difference between their estimates was found. In order to achieve a common view on the extent and rate of erosion and sediment production in the country, the following available data were analyzed: a) results of countrywide applications of erosion models, b) soil loss measurements in plots, c) erosion calculations based on CS-137, d) suspended load of rivers in gauging sites, e) bed load to suspended load ratio in selected reservoirs, and f) contribution of erosion features on sediment yield. Average rates of specific erosion and suspended sediment yield in Iran were obtained to be about two and six t.ha-1.y-1, respectively; which seems to be logical due to the dominance of dry climate in large parts of Iran. A few limited studies showed that the contribution of surface erosion (rill and interrill) on sediment is about 1/2 of other erosion features (gully, mass movements, river bank). Finally, it was shown that the specific rate of sediment yield is increased by an increase in basin area up to 10,000 km2 where it is followed by a downward trend in larger basins. Obviously, these estimates are relatively rough and there is still a long way to achieve more accurate estimations.