A reservoir is a man-made body of water designed to store fresh water. These artificial lakes are typically created by constructing a dam across a valley or by excavating land and enclosing an area with retaining walls or levees. They serve as open-air storage areas where water is collected and held for later use, ensuring availability even when natural stream flows vary.
How Reservoirs Are Created and Their Primary Roles
Reservoirs are primarily formed by building dams across river valleys, utilizing the natural topography to create the basin. Rivers and streams that will feed the reservoir are often diverted during initial construction to create a dry work area, allowing engineers to build the dam and impound the water, forming the artificial lake.
Reservoirs serve diverse community and environmental needs. They provide a stable water supply for human consumption and industrial use, particularly during drier periods. Reservoirs also play a role in irrigation, supplementing insufficient rainfall for agricultural lands.
Many reservoirs are integral to hydroelectric power generation, where the energy from falling water drives turbines to produce electricity. They also contribute to flood control by impounding excess water during heavy rainfall, slowly releasing it over time to mitigate downstream flooding. Reservoirs can also support recreational activities like boating and fishing, and improve navigation conditions on rivers by increasing water levels upstream.
From Source to Tap: The Journey of Reservoir Water
Reservoirs gather water from various natural sources, including direct rainfall, snowmelt, and the flow of rivers and streams. They can be on-stream (located on the original streambed) or off-stream (receiving diverted water from a nearby source).
Once collected, water is conveyed from the reservoir through pipelines, canals, and sometimes tunnels to reach treatment plants. After treatment, it is distributed to homes, agricultural areas, and industrial facilities.
Gravity often assists in moving water from elevated reservoirs to lower-lying areas, though pumping stations are also employed to aid in distribution and maintain adequate water pressure. Service reservoirs, often elevated tanks or underground cisterns, store treated water close to consumption points to manage daily demand fluctuations and provide emergency reserves.
Maintaining Reservoir Water Quality
Ensuring the safety and purity of reservoir water is important for public health. Water utilities employ a multi-barrier treatment process. Initially, raw water from the reservoir undergoes screening to remove large debris such as leaves and rubbish.
Following screening, chemicals like alum or ferric chloride are added in a process called coagulation to bind smaller suspended particles, such as silt and sand, into larger, heavier clumps called “flocs.” These flocs then settle to the bottom in sedimentation basins, where they are removed as sludge.
The water then moves to filtration, passing through layers of materials like sand, gravel, or charcoal to remove remaining suspended particles, microorganisms, and algae. The final step is disinfection, where harmful microbes like bacteria and viruses are eliminated, typically using chlorine, ozone, or ultraviolet (UV) light. Continuous testing and monitoring ensure the water meets safety standards before distribution.