The Role of Lakes in Freshwater Supply

Lakes are a significant source of freshwater for most cities across the United States. Ranging from the vast Great Lakes to small reservoirs, these lakes supply water to millions of residents in the United States alone, and this practice is also widespread in other regions of the world, including China and Australia. According to a study published by National Geographic in 2023, only 3% of the water on Earth is freshwater, and only roughly 1% of that freshwater is accessible and suitable for treatment. This makes convenient sourcing from large freshwater bodies, such as lakes, a viable practice for treatment.

Widespread Use of Lake-Based Water

In the US, surface water sources, including lakes, rivers, and reservoirs, account for approximately 63% of public water supplies, according to the U.S. Geological Survey (USGS). The reliance is heavily evident in urban areas that are situated near large lakes or reservoirs. For instance, Chicago utilizes Lake Michigan, while Cleveland and Toledo utilize Lake Erie. These lakes are part of regional water supply systems, thereby highlighting the significance of lake-based sources within urban water systems.

Popularity and Challenges of Lake Sourcing

A water supply based on lakes is popular because it allows municipalities to access large volumes of water at relatively low initial infrastructure costs. Lakes can support sizable populations and provide treatable space that scales with urban growth. Surface water visibility and control, combined with accessibility, contribute to a common preference for lakes over groundwater, which carries costly and technically challenging deep wells.

However, surface water is more hazardous in terms of contamination than groundwater. Lakes are directly affected by environmental factors, including agricultural runoff, urban stormwater, and industrial waste deposits. These deposits feed pathogens, sediments, chemicals, and nutrients that all complicate treatment. Algae can be another significant concern with lake-based sourcing, often caused by phosphorus and nitrogen pollution, which can produce toxic compounds that cannot be readily eliminated by routine disinfection. An example of this occurred in 2014, when microcystin contamination in Lake Erie impacted Toledo, Ohio, leading to a temporary water shutdown.

Treatment facilities handling lake water must employ lengthy, multi-phase treatment processes, including coagulation, flocculation, sedimentation, filtration, and disinfection. More sophisticated methods, such as activated carbon, ozone, or ultraviolet light, are sometimes used to treat newly introduced contaminants in water. Although these processes increase costs and operational complexity, they are necessary to maintain drinking water safety. Despite these problems, lake water is more widely used than groundwater. Its bulk, availability, and ability to serve large urbanizing systems outweigh greater treatment requirements, and surface water constitutes the foundation of the U.S. municipal water supply.

Benefits of Lake-Based Water Supplies

Apart from availability, lakes possess some other advantages. Municipalities benefit from the ability to manage large storage quantities, allowing water utilities to ensure a constant supply during periods of peak demand. Lakes generally maintain more consistent levels during seasonal transitions than groundwater, especially with the implementation of watershed management plans and reservoirs.

Energy efficiency is also a concern. It tends to require less energy to pump water from lakes compared to deep aquifers, which could necessitate high-power pumps and additional infrastructure. While surface water treatment is more labor-intensive, the factors of accessibility, volume, and energy savings tend to make lake-based systems more convenient for municipalities.

Case Studies of Lake-Based Water Systems

Some U.S. municipalities are great case studies of successful lake-based water system implementation:

• Chicago, Illinois: Lake Michigan is the primary water source for the entirety of the Greater Chicago area, serving a population of close to three million. It is brought into one of multiple treatment facilities with intakes pulling directly from this great lake.
• Cleveland, Ohio: Utilizing Lake Erie, the city's treatment plants provide water that meets rigorous federal guidelines, demonstrating the capacity to handle vast surface water sources safely.
• Phoenix, Arizona: The Lake Pleasant Water Treatment Plant supplements the city's general desert water supply with lake-based water, demonstrating the viability of lake-based sourcing in arid lands when complemented with other water management practices.
• Muskegon, Michigan: The Muskegon Water Treatment Plant treats water from Lake Michigan to produce over four billion gallons of drinkable water annually for almost 90,000 people. The plant operates 24/7, with staff members regularly sampling and testing the water throughout the treatment process to ensure optimal water quality.
• Forsyth County, Georgia: With a favorable ruling, this county was able to establish an intake for water treatment on Lake Lanier, where it had previously operated as a groundwater facility, which better met the high demand of residences and farms throughout the service area.

These examples illustrate the diverse applications of lake-based water systems in various geographic and climatic settings throughout the United States.

Lakes are entirely essential in supplying freshwater to U.S. cities. While surface water is more intensely treated due to higher vulnerability to contamination and environmental inputs, its accessibility, quantity, and scalability make it the most common choice for urban water systems. Conservation of lake water sources through watershed management, pollution prevention, and emerging treatment technologies is essential. With increasing urbanization and climate regime shifts, it will be crucial to maintain the safety and reliability of these lake-based systems to ensure both public health and urban development.