Why Do Micro Hydropower Plants Often Choose Low Weir Dams?

Why Do Micro Hydropower Plants Often Choose Low Weir Dams?

Low weir dams are hydraulic structures with a relatively low height, primarily designed for water diversion and raising water levels. They are widely used in micro and small-scale hydropower plants, agricultural irrigation, water resource regulation, and ecological water conservancy projects. Compared to large storage dams, low weir dams have a simpler structure, lower construction costs, and less environmental impact, making them an important form of low-impact water resource development.

I. Basic Functions of Low Weir Dams
Low weir dams are typically built in rivers or streams, and their main functions include:
Raising the upstream water level to create usable head
Guiding water flow into the intake or diversion channel
Stabilizing water flow conditions and improving the reliability of hydraulic or hydropower systems
Intercepting floating debris and some sediment to protect downstream facilities
In micro-hydropower stations, low weir dams are mostly used in run-of-river hydropower systems and do not undertake large-scale water storage tasks.

II. Structural Characteristics
Low weir dams have the following typical structural characteristics:
Low dam height: generally only tens of centimeters to a few meters
Short dam body: mostly built across the river channel
Overflow operation: under normal operating conditions, water can flow directly over the weir
Diverse structural forms: can be concrete, masonry, gabion, or reinforced concrete structures
This structure allows low weir dams to safely overflow during floods, reducing changes to the river’s hydrological conditions.

III. Common Types
1. Concrete Low Weir
Stable structure and good durability, suitable for river sections with good foundation conditions.
2. Masonry Low Weir
Uses local stone materials for construction, lower cost, suitable for mountainous or inaccessible areas.
3. Gabion Low Weir
Composed of metal mesh cages filled with stones, good permeability, environmentally friendly, and strong erosion resistance.

IV. Design and Construction Key Points
1. Flood Control and Discharge Capacity
Low weir dams must have sufficient overflow capacity to ensure safe passage of floods and prevent the dam body from being washed away.
2. Dam Foundation and Erosion Protection Design
Dam foundation treatment and downstream energy dissipation and erosion protection measures are crucial for ensuring long-term safe operation. 3. Water Intake and Sediment Discharge Design
The rational arrangement of water intakes, trash racks, and sediment discharge facilities can effectively reduce the impact of sediment on equipment and channels.
4. Ecological Flow Assurance
The design should ensure sufficient basic ecological water flow downstream, minimizing the impact on the river ecosystem.

V. Application Advantages
Low-weir dams have significant overall advantages:
Short construction period and low construction difficulty
Relatively low investment cost
Limited impact on the natural environment
Simple maintenance and management
Suitable for decentralized, rural, and mountainous projects
Therefore, they are widely used in micro-hydropower stations and ecological water conservancy projects.

VI. Conclusion
Low-weir dams are a safe, economical, environmentally friendly, and practical form of hydraulic structure. Through rational design and standardized construction, they can effectively improve water resource utilization efficiency while maintaining the natural characteristics of the river channel.
In micro-hydropower stations and sustainable water conservancy development, low-weir dams are playing an increasingly important role.