The fundamental difference between a dam and a diversion dam lies in their primary purpose and the scale of water impoundment. While a dam typically creates a large reservoir for storage, power generation, or flood control, a diversion dam is specifically designed to raise the water level to redirect water to a designated location, often without creating a significant reservoir.
What is the Difference Between a Dam and a Diversion Dam?
A dam is a general term for a robust barrier constructed across a river or stream to obstruct, direct, or slow down the flow of water, resulting in the formation of a reservoir or lake behind it. Its primary functions often include long-term water storage for various uses like drinking water, irrigation, flood control, or hydroelectric power generation. In contrast, a diversion dam is a specialized type of dam whose main role is to elevate the water level slightly, allowing a portion of the flow to be rerouted into a canal, pipeline, or other conduit for specific purposes, such as supplying water to an irrigation system, a municipal water treatment plant, or a run-of-river hydropower facility.
Understanding Dams (General)
A dam is a monumental structure engineered to serve multiple objectives, often involving the creation of a substantial body of water.
- Primary Purpose: To impound water, creating a reservoir for long-term storage, flood control, hydroelectric power generation, recreation, and navigation.
- Reservoir Size: Typically creates a large, deep reservoir, significantly altering the natural landscape.
- Key Characteristics:
- Water Storage: Designed to hold back vast quantities of water over extended periods.
- Flood Control: Can release water in a controlled manner to mitigate downstream flooding.
- Hydroelectric Power: Many dams integrate powerhouses to generate electricity from the stored water.
- Water Supply: Provides reliable water sources for agriculture, industry, and domestic consumption.
- Recreation: Reservoirs often support activities like boating, fishing, and swimming.
- Examples:
- The Hoover Dam on the Colorado River, primarily for flood control, power generation, and water storage.
- The Three Gorges Dam in China, notable for its massive hydroelectric power capacity and flood control.
Understanding Diversion Dams
A diversion dam, sometimes referred to as a weir, serves a more focused purpose. It's a structure built to facilitate the redirection of water.
- Primary Purpose: Diversion dams are used to raise the water level in order to redirect the water to the designated location. This redirection is crucial for specific applications.
- Reservoir Size: Usually creates a minimal or comparatively small pool upstream, sufficient only to enable the diversion, rather than for large-scale storage.
- Key Characteristics:
- Water Redirection: Its primary function is to channel water away from the main river flow into another system.
- Elevation Control: Raises the water surface elevation just enough to allow gravity flow into an intake structure or canal.
- Run-of-River Systems: Common in run-of-river hydropower schemes, where water is diverted through turbines and then returned to the river downstream.
- Irrigation Intakes: Widely used to feed water into irrigation canals for agricultural use.
- Municipal Water Supply: Can divert water to treatment plants for urban consumption.
- Examples:
- Many smaller weirs built across rivers to feed irrigation canals in agricultural regions.
- Dams specifically designed to funnel water into a penstock for a hydropower plant, where the power generation doesn't rely on a large storage reservoir but rather the consistent flow of the river.
Key Differences at a Glance
The table below summarizes the core distinctions between a general dam and a diversion dam:
| Feature | Dam (General) | Diversion Dam |
|---|---|---|
| Primary Goal | Impoundment, storage, flood control, power generation | Raise water level to redirect flow |
| Reservoir Size | Typically large, significant long-term storage | Generally smaller, minimal impoundment for immediate redirection |
| Main Function | Create a reservoir for various uses and benefits | Facilitate the diversion of water into other channels/systems |
| Impact on Flow | Significantly alters downstream flow patterns due to storage | Modifies flow primarily at the diversion point, often less storage impact |
| Common Uses | Hydroelectric power, large-scale irrigation, municipal supply, flood control, recreation | Irrigation canals, run-of-river hydropower, municipal water intakes |
| Structure Type | Large, robust, often concrete or embankment | Can be smaller weirs, gated structures, or low dams |
In essence, while all diversion dams are technically dams, their specific design and operational focus distinguish them from larger, multi-purpose dams that prioritize water storage and flow regulation.
