Publication date: March 25, 2025

Understanding & Forecasting Hydroelectric Power Generation in Japan

Shulman Advisory, in collaboration with Atmospheric G2, is excited to share our third and final article of this mini-series on understanding and forecasting hydroelectric power generation in Japan. As the nation’s most established renewable energy source, hydropower plays a crucial role in energy stability. In this article, we explore the factors influencing hydroelectric output and how advanced forecasting techniques can enhance efficiency and reliability.

Let’s dive in.

Japan has invested significantly in solar and wind power in recent years, but clean, durable and reliable hydropower remains a crucial backup source. To achieve carbon neutrality in 2050 and the intended 46% reduction in greenhouse gas emissions by 2030, it is essential that Japan continues to utilize the use of its hydropower resources. The latest government figures show that the total installed capacity for (small and medium-sized) hydropower generation under the Feed-in Tariff (FIT) and/or Feed-in Premium (FIP) certification schemes (excluding large-scale hydropower facilities) is 10 GW as of March 2024. This has increased from 9.8 GW registered in March 2020, and is expected to grow to approximately 10.4 GW by 2030 (METI).

Japan has several large-scale hydroelectric dams under development. TEPCO has been implementing upgrades to its Kanagawa hydropower project in Nagano to increase its capacity from 940 MW to 2,820 MW (2.8 GW), and upgrades to its Kazunogawa hydropower project in Yamanashi from a current capacity of 1,200 MW to 1,648 MW (TEPCO). However, Japan is shifting its focus to the development of small and medium-sized hydropower over large-scale installations, mainly due to limited site suitability and increased costs.  Implementing small and medium-sized hydropower projects is beneficial, as it utilizes the limited areas available for hydropower generation, which causes less environmental impact and a shorter time for recovering investment costs (METI). On the geographical distribution of hydropower generation, Chubu (particularly Gifu, Toyama and Nagano), Tohoku and Hokkaido are the regions with the highest number of generation capacities. Notably, Gifu and Nagano recorded the highest generation volumes at 718 GWh and at 603 GWh respectively in October 2024 (METI). The Sea of Japan side (e.g., Toyama) specifically gets heavy winter snowfall, with snowmelt providing abundant water resources in spring and summer, ideal for hydropower. This, aided by the mountainous terrain, creates large elevations in these regions, which is ideal for hydropower generation.

In order to achieve its decarbonization objectives and fuel mix targets for 2030 and 2040 respectively, the government has two strategic focuses relating to hydroelectric power: (1) the comprehensive use of hydropower and dams for hydropower generation (improvement of operation of existing dams and active use of unused dams) and (2) new development of small and medium-sized hydropower generation in harmony with the environment and local communities (support for small- and medium-scale hydropower at the stage of considering its introduction and overall cost reduction) (METI). In order to promote development in line with these aims, the Japanese government has established the “Subsidy for Acceleration of Introduction of Hydroelectric Power Generation” to support initial surveys and support projects for the effective utilization of existing facilities (METI). In FY2022, the Japanese government supported 34 preliminary surveys, confirming a total of approximately 8.3 MW of new development potential (24 of which were in the Tohoku and Chubu areas) (METI).

Atmospheric G2 is using the latest AIFS (Artificial Intelligence Forecasting System) weather model technology to provide accurate and detailed forecasts of precipitation across Japan. AIFS is superior to traditional NWP (Numerical Weather Prediction) models because it uses AI to process vast amounts of weather data faster and more efficiently, reducing computation time and energy use. Unlike NWP models, which rely on complex physics equations and require supercomputers to run for hours, AIFS learns patterns from past weather data, allowing it to make accurate forecasts in minutes. This makes AIFS not only quicker but also capable of improving over time as it processes more real-world data. This advanced model processes massive amounts of atmospheric data to predict where and how much rain will fall, helping to track storms, heavy rainfall, and potential flooding. By analyzing pressure systems, wind patterns, and moisture levels, the AIFS model gives meteorologists a clearer picture of upcoming weather conditions. As seen in the latest forecast, this technology is helping to monitor precipitation approaching Japan, allowing for better preparation and response. Whether for daily planning or disaster readiness, Atmospheric G2’s cutting-edge weather tracking ensures that people and industries across Japan stay informed and ready for changing weather conditions.