Watershed projects effectiveness in reducing erosion and sediment of large rivers (Case study, (Zanjanrud River in Zanjan province, Iran) Mehdi shafaghati 1,Seyed hamid reza Sadeghi2, Amir saddodin3, Parviz Garshasbi4 1- PhD Student in climatology, Kharazmi University, Tehran, Iran 2-professor, PhD in Soil and Water Conservation Engineering ,Tarbiat Modares University (TMU),Noor, Mazandaran Province, Iran, 3- Associate Professor, Dean Faculty of Range and Watershed Management, Manager the National Mega Project of Integrated Watershed Management, Gorgan University , Golestan Province, Iran 4- PhD in Soil and Water Conservation & Deputy Head of watershed management forest, range and watershed management organization, Jihad-agriculture ministry, Tehran, Iran Email:m_shafagati@yahoo.com Abstract: Humans for their survival, food utilization of the soil and water resources needs to be enabled. But despite a phenomenon that endangers the resources, soil erosion is. One of the activities in the field run off control and prevent soil erosion and degradation, and ultimately playing a role to consolidate the channel and will watercourse is Watershed Management projects that this positive step toward your balance is stable. Effect of Watershed projects by measuring the parameters and check how to achieve its main objectives and sub, the first step in evaluating the principles of this branch of science is considered. Case study looking at (Zanjanrud River in Zanjan province), to assess the practice about the implementation of specific projects is Watershed Science. With the implementation of these projects over the years in a row, different aspects of effectiveness can be examined them. Among these is the effectiveness of water harvesting can prevent erosion and sediment production, prevent flooding phenomenon, increased vegetation, job creation are Mentioned in the comments area. In addition to the full article introduces the desired area, to discuss concepts and generalities, river conditions and the relevant areas before and after project implementation, useful results from project implementation and provide numerical assessment will be discussed. Key words: erosion and sediment - watershed - Watershed Management Project River Znjanrud