Interconnected Surface Water Depletions

​Graphic credit: USGS

Though considered legally separate, groundwater and surface water are physically interconnected resources. SGMA recognizes this interconnection and requires that GSPs avoid “depletions of interconnected surface water that have significant and unreasonable adverse impacts”. Additionally, GSPs must consider impacts to groundwater dependent ecosystems.

Lakes, wetlands, rivers, and other surface water bodies interact with groundwater in two main ways: surface water bodies “gain” or receive water from of the groundwater system or they “lose” or provide water to groundwater. The extent to which this exchange been surface water and groundwater systems occurs depends on the hydraulic gradient between systems.

In much of California, groundwater pumping has lowered the hydraulic gradient in these systems, such that surface water bodies largely lose water to underlying groundwater systems. A study by The Nature Conservancy in 2016​ estimates that there is approximately 900,000 acre feet less in the Sacramento River from groundwater pumping and other causes. However, in some groundwater basins the connection between these systems remains, providing support for plant and aquatic species particularly in dry months and years.


​Soon, the Groundwater Exchange will be integrated with the California Water Library so that documents on groundwater and surface water interaction will appear here automatically.  In the meantime, you can view those documents by clicking here.