## 1 Introduction  
As a world-recognized renewable and clean energy, the rational development and utilization of small hydropower are of great significance for China to achieve the goal of \"peak carbon and carbon neutrality\". According to the definition of relevant authorities in China, hydropower stations with an installed capacity of less than 50 MW are regarded as small ones [1]. By the end of 2019, China had built 45,445 small hydropower stations, with an installed capacity of 81,442 MW (equivalent to the total installed capacity of 3.5 Three Gorges hydropower stations), accounting for 22.9% of China's installed hydropower capacity and 4.1% of China's total installed power capacity. In 2019, China's small hydropower generation capacity reached 253 million MWh, accounting for 19.5% of the total hydropower generation capacity and 3.5% of the total power generation capacity [2]. According to the latest coal consumption standard of 308 g/kWh, the annual power generation of small hydropower stations in 2019 was equivalent to saving approximately 78 million tons of standard coal, reducing carbon dioxide emissions by approximately 195 million tons, and sulfur dioxide emissions by approximately 1.01 million tons. Small hydropower stations in China are mainly distributed in remote mountainous areas, and they are an important part of the local power supply. Small hydropower stations are characterized by decentralized development, local network formation, and local power supply, as well as advantages such as low construction cost, short construction period, and fast return; they are natural supplements to the main power grid and have irreplaceable advantages [3]. The large investment in small hydropower has made a great contribution to solving China's clean energy problems; however, most of the small hydropower stations are run-of-the-river stations, with a wide range of points and no adjustment capabilities. In practice, such stations are in a state of \"power generation with water, but shutdown without water\" in the original \"blind\" state. Their operation and output state are completely dominated by rainfall, with frequent fluctuations and uncertainties. With heavy rain, the power generation of small hydropower stations increases sharply, leading to a large and disorderly influx of small hydropower, causing a great impact on the main network, greatly destroying the power balance of the main network, and endangering the safety of the power system [4]. To realize optimal dispatching and resource allocation and ensure the safe, stable, and economic operation of the power system, it is necessary to make a reasonable small hydropower generation plan. Therefore, it is of great significance to accurately predict the generating capacity of small hydropower stations and provide a reference for the coordinated dispatch of multiple power sources in the power-dispatching department. Different from the well-developed forecasting models and methods of large and medium-sized hydropower stations, small hydropower generation capacity prediction research started late and faced a shortage of data (especially meteorological data and runoff data most relevant to small hydropower generation), large numbers, and poor model versatility. It is often difficult to learn from the mature hydrology and power generation forecasting methods of large- and medium-sized hydropower stations. In view of the above problems, a few scholars have carried out relevant research. Paper [5] took the entire area of small hydropower as the object and assimilated snow observations to improve the forecasting results of power generation capacity of small hydropower in snow-rich areas. Paper [6] decomposed the power generation load of small hydropower into meteorological load components and long-term trend load components and predicted the power generation load of small hydropower by establishing a regression relationship between meteorological factors and meteorological load and a prediction model of long-term trend load characteristics.