Natural ecosystem services can provide direct and indirect economic benefits. These services are not fully understood, although they are used by human societies. Economic valuation is an effective way to understand the multiple benefits of these services. In this research, the economic value of vegetation cover function in soil and water conservation is estimated within natural ecosystems of Golpayegan dam watershed. To quantify the water and soil conservation functions, SCS and MPSIAC methods were used, respectively. Three scenarios including (a) vegetation completely removed, (b) vegetation increased by 10%, and (c) vegetation increased by 20% were defined to illustrate the role of vegetation cover in protecting soil and water resources. Then the effects of each scenario in terms of runoff, erosion and sediment condition were determined using SCS and MPSIAC models. The results indicate that current vegetation cover is conserving 13.13 million m 3 of water and 67483.96 m 3 of soil by increasing initial losses and decreasing curve number. Under second and third scenarios, vegetation will conserve 5.54 and 9.70 million m 3 of water and 34814.84 and 65700.76 million m 3 of soil, respectively. The replacement cost approach was applied for economic valuation of soil and water conservation function. The information of costs required for construction of artificial structures with the same role (water and sediment trapping dams in Gharghan Sub-basin) was used to be considered as the economic value of soil and water conservation by natural ecosystems of 1378 was used. Valuation results reveal that each acre of the study area can conserve 123.43 m 3 of water and 0.63 m 3 of soil annually with the economic value of 4320050 and 11419.12 Rials/ha/year, respectively. In scenarios 2 and 3, these rangelands will be able to conserve 49.31 and 91.23 m 3 /ha/y of water and 0.32 and 0.61 m 3 /ha/y of soil with the economic value of 1726002 and 3193142 Rials/ha/y for water conservation and 5891.10 and 11117.38 Rials/ha/y for soil retention functions, respectively. Results indicate the importance and considerable role of rangeland ecosystems in soil and water conservation and can be used for land rehabilitation and degradation control planning. Keywords: Valuation, Soil and water conservation, Golpayegan Dam, Replacement Cost, SCS, MPSIAC.
