World Water Day: A good time to recognize vital role stormwater management can play in recharging aquifers

Traditionally, stormwater runoff has often been seen as a nuisance or environmental threat; flooding streets, damaging property and polluting water bodies. The primary focus of stormwater management was to move water away from urban and developed areas as efficiently as possible, with less emphasis on capturing its potential as a resource.

However, as communities experience these higher volumes of stormwater and/or water scarcity as a result of changing climate, there is a growing movement to view stormwater as a valuable asset that can be reused. According to a recent survey from Advanced Drainage Systems, the idea of stormwater as a resource appears to be increasing with the American public. 60% of Americans who responded to the survey expressed concern about how stormwater is managed to ensure sustainability and stewardship.

This year’s World Water Day (March 22) is a good time to highlight one way this asset can be reused. When managed and treated properly, stormwater runoff can be used to recharge aquifers in certain areas of the country.

Aquifers are a vital source of water for many parts of the country and recharging them is essential for maintaining the health of our water supply. It not only ensures long-term sustainability, but it also helps preserve ecosystems that depend on groundwater. They serve as a critical source of freshwater for agricultural, industrial, and domestic use. According to the National Ground Water Association (NGWA), more than 40% of Americans depend on groundwater for their drinking water.

However, many aquifers are being depleted at a faster rate than they can naturally replenish, causing serious problems for both human populations and the environment that go beyond the availability of potable water. For instance, a 2022 study from Stanford University showed California farmland will sink unless aquifer levels are recharged.

So how can stormwater management be used to help recharge aquifers? It helps to think of stormwater management in terms of the lifecycle of the raindrop. It means managing stormwater from the moment a raindrop hits the ground until it is returned to the environment.

This approach includes four key steps:

• Capture: Collecting and directing runoff to an underground conveyance system. This can include drain basins, which typically feature a ground-level opening leading to an underground collection system.

• Conveyance: Moving water safely and quickly away from developed sites to prevent flooding damage and reintroduce it to the water cycle.

• Storage: Using retention and detention systems to manage infiltration and recharge stormwater before the treatment process. In certain cases, this can include storing the water for reuse before returning it to the environment.

• Treatment: Removing trash, debris and pollutants from runoff collected in previous steps, ensuring the water is returned to its natural environment in the same or better condition than when first captured.

A key part of this process is storage, which plays a vital role in aquifer recharge by using infiltration basins and ponds to help water seep back into the ground. Detention ponds temporarily hold stormwater and slowly release it, allowing for more time for the water to infiltrate into the ground. Retention ponds are designed to keep water in place for longer periods, which increases the potential for water to seep into the soil and replenish local aquifers.

In developed and urban areas where space is limited and it is not possible to utilize a body of water, below ground containment space can be designed and utilized to effectively store stormwater. This can include storm chambers and modular systems that are designed to provide underground storage for stormwater retention, infiltration, disposal or harvesting for reuse. Depending on the region and the runoff quality and quantity, multiple solutions may even be used.

These solutions can allow the water to slowly percolate through the soil, filtering it and allowing it to seep into the ground to recharge underground aquifers. By creating space for the water to infiltrate, these stormwater management solutions mimic natural processes that would normally occur during rainfall in undeveloped areas.

One example of how stormwater management infrastructure can be designed to help recharge an aquifer is a recent project in Texas. The region’s Edwards Aquifer is the main source of drinking water for nearly two million people and provides water for agriculture and industry in the region. Aquifers in general are vulnerable to pollution when pollutants enter the recharge zone. To help protect the aquifer, the developer of the Natural Grocers store in Georgetown, Texas, chose to employ two stormwater management systems to provide enhanced filtration and debris trapping.

For those involved in stormwater management projects in regions where there is an aquifer, there are two important resources. The first is the United States Environmental Protection Agency (EPA), which released the “Enhanced Aquifer Recharge of Stormwater in the United States: State of the Science Review” report in 2021. The report covers a variety of areas related to the topic, including stormwater infrastructure and methods commonly used, factors that influence stormwater recharge volumes, and best practices for effective and safe stormwater recharge of aquifers.

The second resource is the stormwater management solution provider for the project. The provider should have experts on-hand who can help navigate federal, state and local regulations that pertain to the region’s aquifer. They can also help identify the design requirements and create a solution based on those requirements. This includes not only regulations and building codes, but also site constraints, preferences of communities, soil characteristics, pollutant load, water flow and area rainfall. They take a macro-level view of these factors to make sure the goal of the project is feasibly possible and what type of stormwater solution would best meet that goal.

Effective stormwater management infrastructure doesn’t just manage runoff and prevent flooding — it also can be a powerful tool to help facilitate the reuse of the water for a variety of purposes, including recharging aquifers. For those projects in regions with aquifers, implementing stormwater management solutions that help recharge that aquifer is a critical step in ensuring that freshwater resources remain available for future generations.