The Greater Los Angeles region faces growing pressure to secure reliable, sustainable water supplies. Local leaders have set a goal of meeting 80 percent of its water needs from local sources by 2045, up from roughly 10 percent in recent years. Capturing water and storing it underground for later use is one of the ways the region plans to reach that goal.
This practice of storing more water in underground aquifers is known as managed aquifer recharge. While managed aquifer recharge can use any type of water, using stormwater is a good option in Los Angeles. When heavy rain falls on the pavement and rooftops that cover much of Los Angeles, most of the water runs off instead of soaking into the ground, which can cause flooding. Using stormwater slows runoff, captures it, and helps it soak into the ground and replenish underlying aquifers. To do this well, we need to understand not only where stormwater can soak into the ground, but also how that water moves between basins. This study looks at both stormwater-recharge potential and how the groundwater basins in the region are connected to give a clear, regional picture of how stormwater can support local water supplies.
Problem Description
Much of Los Angeles is covered by pavement and concrete, which stops rainwater from soaking into the ground. Stormwater control structures (like Low Impact Development (LID) and Best Management Practices (BMP)) help capture this water so it can soak into the ground. But soaking into the ground is not the same as reaching the usable water supply. Some models assume recharge as roughly equal to the amount of water that infiltrates, without evaluating whether the groundwater system can actually accept and transmit that water . In many areas, infiltrated water recharges shallow zones that drain away locally, rather than reaching aquifers of the groundwater system used for water supply.
Another challenge is that groundwater does not stay in one place. It moves between groundwater basins, which are often defined by political or management areas and not hydrology, and the paths it follows can be complex. Often models focus on one groundwater basin, and the connections with neighboring groundwater models are not well understood. Often, groundwater models simplify these connections, which can lead to missing how groundwater moves across the region. To understand the full benefit of stormwater capture for managed aquifer recharge, we need to better understand the regional water movement by understanding the inter‑basin water movement.
Study Objective
This study’s goal is to estimate how well stormwater can recharge the usable groundwater in the Los Angeles region. A second goal is to improve the regional understanding of how groundwater moves between connected basins across the greater Los Angeles region and how those connections influence stormwater‑recharge potential.
Study Approach
USGS scientists, in cooperation with Los Angeles County Public Works, are linking existing numeric groundwater models to simulate the connected flow between groundwater basins. The study relies on previously published models and data rather than new data collection.
After developing a greater Los Angeles region groundwater model that simulates water movement between basins, we can work toward a regional picture of how efficiently stormwater capture can recharge the aquifers that supply the greater Los Angeles region.
The Greater Los Angeles region faces growing pressure to secure reliable, sustainable water supplies. Local leaders have set a goal of meeting 80 percent of its water needs from local sources by 2045, up from roughly 10 percent in recent years. Capturing water and storing it underground for later use is one of the ways the region plans to reach that goal.
This practice of storing more water in underground aquifers is known as managed aquifer recharge. While managed aquifer recharge can use any type of water, using stormwater is a good option in Los Angeles. When heavy rain falls on the pavement and rooftops that cover much of Los Angeles, most of the water runs off instead of soaking into the ground, which can cause flooding. Using stormwater slows runoff, captures it, and helps it soak into the ground and replenish underlying aquifers. To do this well, we need to understand not only where stormwater can soak into the ground, but also how that water moves between basins. This study looks at both stormwater-recharge potential and how the groundwater basins in the region are connected to give a clear, regional picture of how stormwater can support local water supplies.
Problem Description
Much of Los Angeles is covered by pavement and concrete, which stops rainwater from soaking into the ground. Stormwater control structures (like Low Impact Development (LID) and Best Management Practices (BMP)) help capture this water so it can soak into the ground. But soaking into the ground is not the same as reaching the usable water supply. Some models assume recharge as roughly equal to the amount of water that infiltrates, without evaluating whether the groundwater system can actually accept and transmit that water . In many areas, infiltrated water recharges shallow zones that drain away locally, rather than reaching aquifers of the groundwater system used for water supply.
Another challenge is that groundwater does not stay in one place. It moves between groundwater basins, which are often defined by political or management areas and not hydrology, and the paths it follows can be complex. Often models focus on one groundwater basin, and the connections with neighboring groundwater models are not well understood. Often, groundwater models simplify these connections, which can lead to missing how groundwater moves across the region. To understand the full benefit of stormwater capture for managed aquifer recharge, we need to better understand the regional water movement by understanding the inter‑basin water movement.
Study Objective
This study’s goal is to estimate how well stormwater can recharge the usable groundwater in the Los Angeles region. A second goal is to improve the regional understanding of how groundwater moves between connected basins across the greater Los Angeles region and how those connections influence stormwater‑recharge potential.
Study Approach
USGS scientists, in cooperation with Los Angeles County Public Works, are linking existing numeric groundwater models to simulate the connected flow between groundwater basins. The study relies on previously published models and data rather than new data collection.
After developing a greater Los Angeles region groundwater model that simulates water movement between basins, we can work toward a regional picture of how efficiently stormwater capture can recharge the aquifers that supply the greater Los Angeles region.