Dwerige weir is a small hydraulic structure was constructed for reducing the flooding impact, irrigation regulation and environmental purposes. Also, the project was considered as a pilot water harvesting project in the eastern part of Missan Province. In this study, the problem of siltation in the weir reservoir was studied depending on the topographic surveying data of the reservoir, before it is was filled with water, and the final silt elevation taken directly during the reservoir drying period. The study uses the topographical and geotechnical approach to calculate the silt volume and the economic estimation of the economic loss of the project. A comparison between the designed and real project lives was made and the results are discussed in detail in order to avoid this problem in the future of the weirs and dams in the study area.