Variability in the flow regime in hydroelectric plants

Peru has more than 70 hydroelectric plants that supply about half of the country’s electricity. But a mix of climate, environmental, and social pressures — including the El Niño phenomenon, which brings unusually warm ocean temperatures and disrupts weather patterns, and growing demand for water in river basins for farming, cities, and industry — is making river flows more unpredictable than ever.

The turbines that generate electricity at these plants rely on a consistent flow of water. Even short-term changes can affect their operating limits and sharply reduce energy output. Over time, these shifts can damage equipment and lead to long shutdowns, cutting into the country’s ability to generate electricity.

Many of Peru’s hydro plants were built decades ago, before modern tools for tracking water and weather were available. As a result, the studies used to design them are now outdated. River conditions have changed, climate patterns are more difficult to predict, and today’s tools for measuring and modeling these changes are far more advanced.

Unfortunately, the regulations that govern these systems haven’t kept up with environmental and technological changes.

Delays in obtaining environmental permits and licenses can stall project development and increase costs. Extreme climate events during the approval process often warrant updated hydrological data, adding complexity and constant adaptation to the process.

While some consequences of flow variation are readily apparent, such as reduced energy generation, others are less obvious yet equally important. Extremely high flows can increase sediment loads, damaging equipment, while prolonged droughts may cause operational stoppages. These challenges underscore the need for adaptive, forward-looking water resource management to ensure long-term sustainability and efficiency.

The Osinergmin report from the first quarter of 2024 underscores the magnitude of environmental risks, noting that natural phenomena and force majeure caused 23% of service interruptions accounting for over half of total downtime. 

Designing for a variable future

During the planning and design stages of a hydroelectric project, it is essential to conduct a rigorous and detailed hydrological analysis of the water flow patterns. Recommended tests include the Hurst exponent, which helps determine whether river flow tends to follow long-term trends, and detrended fluctuation analysis (DFA) to detect changes and fluctuations over time. It is also important to conduct randomness and trend tests to identify significant patterns that could affect the hydraulic design and future operation of the plant.

Designing for resilience: Predictive tools and climate-informed infrastructure

Forecasting tools, including artificial intelligence, are vital for to predicting extreme events such as prolonged droughts or intense floods. Another key consideration is sediment, which can clog hydro equipment and cause significant damage. Using specialized computer models that simulate sediment movement, especially in catchment areas where water collects and flows into the plant, can help inform structural design and reduce the risk.

Climate change scenarios must also be integrated from the outset. Incorporating projections of climate variability allows for resilient infrastructure design that supports long-term technical, economic, and environmental viability.

Real-time operation

Once a hydropower plant is up and running — whether it’s run-of-river, which uses the natural flow of the river with little or no water storage, or reservoir-based, which stores water in a dam and releases it as needed — its ability to generate electricity depends heavily on consistent water flow. Management plans should address infrastructure needs, changing hydrological conditions, downstream ecological requirements, and competing demands from agriculture, urban supply, and conservation.

Regular communication among all users in the watershed is critical for responding to extreme events and optimizing water use. In some cases, forming a watershed committee can help facilitate coordination. For run-of-the-river power plants, which have limited ability to regulate flow, forecasting and early warning systems are vital for anticipating floods or droughts. Reservoir-based plants also benefit from these systems, enabling more precise water release planning for energy generation, environmental needs, and safety.

Continuous improvement of instrumentation and monitoring is also critical. Installing sensors for level, flow, turbidity, temperature, and water quality, both in the reservoir and in the downstream sections, allows for accurate, adaptive management. In run-of-river plants, this helps detect insufficient or excessive flow that may affect the turbine operation or minimum flow requirements. In reservoir plants, robust monitoring networks support storage assessment, forecasting resource evolution, and informed decisions about spillway, gate, or turbine operations.

Technology for resilience