Abstarct: Golestan dam is placed on 12 kilometers far from northeast of Gonbad-e-Kavoos. This dam is as a homogenous soil, reservoir capacity of which is 80 millions m^3. Unfortunately, in 2001, 18 millions m^3 was destroyed due to sedimentation resulting from flood. Hence, in 2004, golestan dam 2 was constructed at dam upstream to control flood, which could well control for sediment and flood pouring in downstream. If a dam is constructed over a river containing sediment, all or parts of sediments leaving into reservoir is unavoidable. So, little by little, reservoir’ early capacity is reduced and if suitable predictions and control methods are not done, it may have irreparable effects on reservoir use. Most of reservoirs are planned for multiple purposes such as municipal water supply, watering, hydropower, flood control, etc. Each part of a reservoir is assigned to one of forementioned purposes. Reservoir’ early capacity destroyed by sediment may have various effects on different parts of the reservoir and cause undesirable changes on using reservoir. In this research, goleastan dam reservoir was investigated by models GSTARS3.0 and BISTARS. In each step of calibration, coefficients were determined such that value of error function RMSE is minimized. With regard to predictions of the model, 50-year sediment volume equals 51.6 milllion m^3, something about 60% of dam capacity.