# Soil and Rockfill Dams Safety Assessment for Henan Province: Monitoring, Analysis and Prediction
## 1 Introduction  
China is the most developed country in the world in terms of large-scale water conservancy facilities. By the end of 2022, China had more than 98,000 reservoir dams, and Henan Province had 2538 reservoir dams, of which 48% were built in the 1950s-1970s, and 93% were soil and rockfill dams that had been in use for over 50 years. A large number of water conservancy projects are in \"Extended Service\" and \"Exceeding Service\", and the risk of failure cannot be fully controlled [1, 2]. Restricted by the technical conditions of the 1950s, soil and rockfill dams were often surveyed, designed, and constructed at the same time, resulting in many dangerous reservoirs. Between 1954 and 1971, a total of 159 dam failure accidents occurred in Henan Province, with a dam failure rate of 6.27%, which was at arelatively high level nationwide during the same period [3]. Especially in the flood season, for small- and medium-sized reservoir dams, river embankment failure and other hidden dangers, if not \"belt and braces\", maybe \"a failure of all\". Traditional water conservancy project safety monitoring is mainly based on precision leveling measurements, Global Navigation Satellite System (GNSS) measurements, and sensors installed in the project. These low spatial sampling density methods can only obtain local point deformation, making it difficult to analyze the impact on the dam by combining factors such as reservoir water level and rainfall. At the same time, it will lead to an increase in the cost of human and material resources. The first two methods of measuring personnel need to enter the deformation area, increasing the risk; the latter method of the sensor is difficult to maintain and will gradually lose sensitivity and even effectiveness with the operation of the dam. Interferometric Synthetic Aperture Radar (InSAR) technique with surface-domain deformation monitoring capability can provide a more effective method for water resources engineering safety monitoring [4; 5; 6; 7; 8]. This method can effectively overcome the disadvantages of traditional monitoring, such as high maintenance cost, small monitoring range, low efficiency, and difficulty in predicting deformation. It has been widely used in monitoring geological hazards such as urban surface deformation [9; 10; 11], mountain landslides [12; 13; 14], mine deformation [15; 16; 17; 18], earthquakes [19; 20; 21] and glacial permafrost [22; 23; 24; 25]. Although the InSAR technique started relatively late, it has developed rapidly in the field of water conservancy engineering safety monitoring. This technique improves the accuracy and safety of dam deformation monitoring by providing high-resolution images to obtain accurate deformation information and has been validated in multiple studies [26; 27; 28]. As early as 2009, researchers began to explore the application of the InSAR technique in the stability monitoring of water conservancy buildings. Some typical cases include the application of the InSAR technique in the deformation monitoring and simulation model construction of the Three Gorges Dam [14; 29; 30], the application of reservoir dam deformation monitoring [31; 32; 33], and the application of the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique in the reservoir landslide monitoring [34; 35; 36]. With the continuous progress and development of the InSAR technique, a series of studies have been carried out in recent years on dam slope deformation monitoring by combining the InSAR technique with groundwater level and temperature variations [37; 38; 39]. Therefore, the InSAR technique has played an active role in improving the efficiency of reservoir dam deformation monitoring and protecting the safe operation of water conservancy projects [40; 41]. However, there is no overall analysis of the field of soil and rockfill dams, and there is a lack of attention to the particularity of soil and rockfill dam structures.