What is ecological flow monitoring, and what are its effects?

　　 Ecological Flow Monitoring It refers to the minimum flow discharged from hydropower stations to maintain the basic ecological functions of waterways and to meet public needs for production, daily life, and other water uses.

　　I. Background of Ecological Flow Monitoring Requirements

　　In recent years, hydropower development in China has expanded rapidly, playing a vital role in promoting regional economic and social progress. However, the accompanying ecological challenges cannot be overlooked. At some hydropower stations, insufficient ecological flows have led to reduced or even complete cessation of water flow in certain river reaches, resulting in drying up and adversely affecting the rivers’ normal ecological functions as well as the production and daily lives of local communities.

　　To protect riverine ecosystems and promote the scientific, rational, and orderly development and sustainable use of water resources, water management and environmental protection authorities across the country have successively introduced measures to rectify or oversee hydropower stations that fail to meet ecological flow‑release requirements.

　　Ecological flow monitoring (including downstream discharge monitoring at hydropower stations) is an essential, long-term supervisory and management tool. It enables the competent authorities to continuously track flow‑related discharges from each hydropower station, thereby playing a critical role in safeguarding the ecological water‑use needs of downstream rivers.

　　II. Configuration of the Ecological Flow Monitoring System

　　1. Monitoring Section Configuration

　　Ecological flow monitoring can be implemented by establishing monitoring stations at the power plant’s discharge outlet and installing online monitoring equipment. Additionally, downstream of the power plant, a cross‑section of the waterway can be designated as a monitoring profile, with online instruments deployed to measure the outflow volume.

　　For riverbed or downstream‑type hydropower stations, the monitoring cross‑section shall be located downstream of the powerhouse’s spillway.

　　For run-of-river hydropower stations, monitoring cross‑sections shall be established downstream of the powerhouse and downstream of the reservoir dam, respectively.

　　2. Monitoring Content

　　Downstream ecological flow monitoring at hydropower stations is primarily conducted using automated quartz‑based sensors, with key parameters including water level and discharge (calculated via a stage–discharge rating curve). The system also integrates rainfall, water quality, imagery/video, and gate‑operation functionalities, providing support for watershed ecological protection, reservoir management, and hydrological and water‑resources applications.

　　3. Monitoring Equipment

　　The online monitoring system primarily comprises a telemetry terminal, ultrasonic/radar water level sensors, rain gauges, industrial cameras, and other components, and is powered by solar energy or grid electricity.

　　III. Functions of the Ecological Flow Monitoring System

　　1. Real-time monitoring of water level, flow rate, rainfall, and other relevant data at the downstream sections of each hydropower station.

　　2. Ecological flow monitoring: Timely or real-time upload of on-site images or videos of the cross‑section at the hydropower station’s discharge (communication method).

　　3. When the water level or flow rate falls below the threshold, the system automatically triggers an alarm upon detecting an abnormal condition.

　　4. Display the distribution of measurement points, their operational status, and alarm status in a macro view using vector maps.

　　5. Ecological Flow Monitoring Automatically stores data, images, and videos, facilitating historical queries and incident tracking. It also automatically aggregates historical data by day, month, year, and other time periods, presenting it in various formats such as reports, charts, and histograms.