By Emily Newton
Every water system begins with a source, which entails an intake structure. While these components are universal across different waterways and all serve a similar purpose, they vary widely. There are many kinds of intake structures and professionals in the industry should understand them all.
With more than half of the global population expected to live in water-stressed areas by 2050, water infrastructure management will become increasingly important. That includes capitalizing on the design of water intake structures.
The function of intake structures remains essentially the same across all systems. They draw water in and provide initial filtering to provide freshwater to various facilities — whether a treatment plant or hydroelectric plant. While that purpose may not shift between different structures, the conditions they must account for do.
Some intakes may encounter more polluted waterways or have to separate algae, which can go on to serve as a low-impact fuel source. Others may deal with relatively few contaminants but need more significant volumes of water. Even more must adapt to changing weather, currents and tides.
Since groundwater sources vary so much, the intakes that reside in them are also subjective. Choosing the right type of intake structure can substantially impact a water system’s function. Similarly, maintenance professionals must understand their differences to appropriately service each one’s unique needs.
You can differentiate between different types of intake structures in a few ways. One of the most straightforward is to divide them by their design, which falls into two broad categories — towers and submerged intakes.
Intake towers or exposed intakes are some of the most used intake structures. As their name implies, these extend above the water’s surface, often resembling a tower. Openings at various levels let water flow into the system regardless of its current depth.
Exposed intakes divide further into two subcategories — dry towers and wet towers. Dry intake towers hold no water apart from their intake pipes, which lead directly to the next step in the system. This allows workers to enter the structure to inspect or repair it easily. By contrast, wet towers hold water equal to their level in the source.
The primary advantages of intake towers are their ease of use and versatility. Since they often feature intakes at multiple levels, they can handle various tides, volumes and currents. Having exposed elements above water makes it easier for maintenance workers to access them.
Conversely, submerged intakes are entirely underwater. These structures resemble drains, sitting on the bed of the body of water they occupy, often near the middle or point of greatest depth.
Whereas intake towers use the water’s lateral movement and currents to push water into their pipes, submerged intakes rely on gravity. Water naturally drops through a grate or screen into the mouth. From there, pumps drive the falling water into these submerged wells to the treatment facility or hydroelectric plant.
While submerged intakes are less common, they have several unique advantages. They’re typically more affordable, as they require less infrastructure. They also don’t impact the water source’s flow as heavily, helping preserve the natural environment and avoiding interfering with boat travel.
You can also distinguish between intake structure designs by their water source. Since different bodies of water have various characteristics, each has a different ideal intake structure. For freshwater systems, these categories are river, canal, lake and reservoir intakes.
Rivers account for two-thirds of drinking water in the United States, so river intakes are some of the most common of these structures. These are often towers, as rivers have stronger currents and may rise and fall more than lakes, requiring more versatile infrastructure.
While these towers may reside near river banks, they often sit closer to the middle to provide sufficient depth. Even with multiple intake levels, it’s best to construct these facilities where there’s more water available to ensure consistent volumes throughout the year. Similarly, wet towers are typically the ideal choice, as they better adapt to changing water levels.
River intake design must also consider their intake screens, as stronger currents could bring in more contaminants. T-intake screens are the most popular choice, as they can withstand harsh conditions and remove plenty of debris.
Lakes hold 20.9% of global freshwater, so these intakes are another type you’ll frequently find. While some structures use towers, submerged intakes are often the ideal option in these environments.
Lakewater typically doesn’t rise and fall as much as rivers and features less lateral movement. As a result, submerged intakes are sufficient and opting for these structures lets you collect more water with minimal disruption to the ecosystem. Some systems may install several submerged intakes to provide maximum water volume.
These intakes typically feature a bell mouth and reinforced crib to protect the system from debris and wave damage. While contaminants aren’t as prominent a problem with submerged lake intakes as in rivers, these mouths should still have robust screens.
Another water intake structure design you may encounter is a reservoir intake. These structures manage water systems across America’s many dams, whether they produce power or not.
While reservoirs may look and behave like lakes, these intakes typically more closely resemble river intakes. Towers are often the structure of choice, thanks to their easy accessibility. These intakes must function correctly for the rest of the dam to operate as intended, so serviceability is a leading concern with their design.
Reservoir intakes should stand close to the dam itself, aiming for maximum depth. Dry towers may be ideal in areas that see more volatility or are more crucial to maintain.
A less-common type of water intake structure is the canal intake. These unique structures are typically part of the canal wall, jutting slightly into the interior.
Screens on the side of the canal wall allow water to flow into intake systems but keep debris out. Placement is crucial here to avoid disturbing the canal’s normal flow and minimize contamination. You should place the intake screen below the canal’s minimum water level but at least 1/10 meter above the bed.
The design of water intake structures has a profound impact on the facilities and areas they serve. Water systems should carefully consider their needs and environmental considerations to determine which will work best. Then, they can choose a design that meets their water and maintenance requirements without compromising ecological protections or budgets.
Emily Newton is a construction and industrial journalist. She is also the Editor-in-Chief for Revolutionized Magazine. Keep up with Emily by following her by subscribing to Revolutionized’s Newsletter.