In China, Li Daoyuan (A.D. 466-527) wrote "Notes on Water Classics", in which he described the stone carvings engraved on the stone wall of Longmen Town, a tributary of the Yellow River, with the highest flood level on June 24th in the Wei and Four Years of the Three Kingdoms Period (A.D. 223). After investigation, many records of low water in the history of China were found. For example, on the rocks in the middle reaches of the Yangtze River in Fuling, Sichuan, there are 162 low water data engraved near the stone fish pattern after the Tang Dynasty. Since 1950s, hydrological surveys in some river basins and flood surveys in more than 65,438+02,000 river sections in China have been carried out in China. In 1980s, the Ministry of Water Resources compiled the data of more than 6,000 river sections and the data of more than 60 largest floods in history into the Compilation of Historical Flood Survey Data. The meteorological department has compiled the historical data of drought and flood in China for 500 years. 198 1 year 65438+February, based on the national water resources survey data, the Preliminary Assessment of Water Resources in China was released. Since 1960s, new techniques have been adopted in hydrological survey. For example, remote sensing technology, especially multi-band photography, microwave scanning and infrared technology, has been applied to the study of river basin physical geography and water body and its pollution (see hydrological remote sensing technology); Nuclear technology has made some progress in measuring soil moisture, snow cover and studying the movement of surface water, groundwater and sediments.