Rubber Dams for Hydropower
On small and medium hydro schemes the dam is not only a weir — it is the element that decides how much head the turbines see, and how fast the water can be let go.
Why a Rubber Dam Fits This Duty
Generating output follows head and flow. A rubber dam raises the upstream level above the natural river bed, so the same turbine sees more head through the same flow. That gain comes without a concrete barrage, and without the construction period a fixed weir would need.
The second duty is protection. If a turbine trips or a flood arrives, the machine hall has minutes, not hours. A deflated bag lies on the sill and opens the full cross-section, dropping the upstream level before it reaches the powerhouse.
Because the crest can be trimmed, the scheme can also follow a seasonal rule: hold a higher pool when flow is scarce, lower it when the river is running hard and the extra head is no longer worth the upstream risk.
How It Works in Practice
Head gain at the intake
The bag holds a stable upstream level, so the intake keeps its designed submergence and the turbine avoids the low-head operation that cuts efficiency at part flow.
Instant opening
Deflation is driven by the same control system that runs the plant. A trip signal or a level alarm can drop the bag without an operator on the dam.
Crest trimming
Inflation pressure sets the crest height. Operators can trade a little head for a little more freeboard ahead of a forecast peak, then restore it afterwards.
Coexistence with gates
Where a scheme already has radial or sluice gates, the rubber dam is often fitted alongside them as the long, low-cost span — the gates handle the extreme events, the bag handles everyday level control.
Choosing the Configuration
Fast response favours air-inflated bags or an air shield dam, where the air chamber under the bag gives quick inflation and a stiff crest. Long, low-head spans on a wide river usually favour water inflation for its economics.
The controlling inputs are the design head, the flood discharge the scheme must pass, and how quickly the plant needs the level to drop. Those three set the bag height, the number of bays and the control logic.
Common Questions
The control system can be interlocked with the plant: a trip or an over-level signal initiates deflation. Manual operation and a backup power source remain part of the design.
Both. It is used as the main weir on new small hydro schemes, and as a replacement for tired fixed weirs or flap gates where the owner wants controllable head.
Related Pages
- Rubber Dam Engineering — Bag construction, anchoring and control options.
- Air Shield Dam — Fast-response pneumatic crest control.
- Project References — Dams delivered for water conservancy and power duties.
Tell Us About the Site
Send the river width, the level you need to hold and the flow you must pass — our engineers will come back with a proposed configuration.