In addition, the factors affecting the change of runoff are the construction and operation of reservoirs and the change of the subsurface in the basin. The Jialing River has the largest number of reservoirs in the entire tributary of the Yangtze River, and it is also one of the earliest hydropower development areas in the country. Most of the large reservoirs (total reserves over 100 million cubic meters) were built after the mid-1980s as shown in Table 4. As shown in Figure 13, with the successive construction of large-scale cascade dams, the annual runoff presents a downward trend in the Jialing River basin. As the large reservoirs in the basin (Tingzikou, Caojie, Baozhusi, Shengzhong, etc.) are built one after another, the runoff will decrease significantly, especially when they are first put into operation, but gradually slow down or even rebound occurs after normal operation. The Jialing River Basin is located in the upper reaches of the Yangtze River. Due to its special geographical location, the main purpose of dam construction is hydroelectric power generation, and the demand for irrigation is relatively small. Therefore, the direct impact of dam construction on total runoff is limited. However, with the construction of large reservoirs and the formation of cascade reservoirs, the sediment flux has changed significantly and adjusted the water and sediment transport mechanism of rivers at the basin scale (Lu 2005), which led to changes in the underlying surface, and in vegetation restoration and under the combined influence of climatic factors, the long-term runoff generally showed a downward trend.