Interconnected surface water depletions

Source: USGS

KEY INFORMATION

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. Learn more about GDEs by clicking here.

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.

Interconnected Surface Water Depletions

Navigating Groundwater-Surface Water Interactions under the Sustainable Groundwater Management Act (UC Berkeley Center for Land, Energy, and the Environment) This report examines some of the legal and institutional questions that will inevitably arise as GSAs seek to address groundwater-surface water interactions under SGMA.

Groundwater and Stream Interaction in California’s Central Valley: Insights for Sustainable Groundwater Management (The Nature Conservancy) This study models the historical impacts of groundwater use on groundwater levels and stream flow conditions in the Central Valley.

Rivers that Depend on Aquifers: Drafting SGMA Groundwater Plans with Fisheries in Mind (Center on Urban Environmental Law, Golden Gate University) This guide provides specific information that should be included in GSPs to ensure no significant adverse impacts on fisheries.

Environmental Uses of Surface Water (The Nature Conservancy ) This webpage provides a list of freshwater species located within each groundwater basin to aid GSAs in the evaluation of how groundwater management impacts environmental users of surface water.

Addressing Regional Surface Water Depletions in California: A proposed approach for compliance with the Sustainable Groundwater Management Act (Environmental Defense Fund) This report  proposes an approach that is intended to provide a reasonable balance among the conflicting factors of rigor, cost, uncertainty, and enforce-ability that weigh on avoiding the undesirable result of interconnected surface water depletions.

Groundwater Dependent Ecosystems (GDEs)

Introduction to Groundwater Dependent Ecosystems & Sustainable Groundwater Management: (The Nature Conservancy) Guidance for including GDEs in Sustainable Groundwater Management

Including Groundwater Dependent Ecosystems in Groundwater Sustainability Plans (The Nature Conservancy) This guidance document provides a process for local agencies to identify and include GDEs as a beneficial use and user of groundwater.

Mapping Indicators of Groundwater Dependent Ecosystems (The Nature Conservancy) The first step to sustainably manage groundwater dependent ecosystems (GDEs) is to identify where they are.

Best Practices for using the Natural Communities Dataset (The Nature Conservancy) The NC Dataset identifies vegetation and wetland features that are good indicators of a GDE. This document highlights six best practices for using local groundwater data to confirm whether mapped features in the NC dataset are supported by groundwater.

Groundwater Dependent Ecosystems Rooting Depth Database (The Nature Conservancy) Plant rooting depth information can provide a useful insight on what groundwater levels may be needed to sustain GDEs.

Groundwater Dependent Ecosystem Pulse Tool (The Nature Conservancy) GDE Pulse allows groundwater managers to assess changes in groundwater dependent ecosystem (GDE) health using satellite, rainfall, and groundwater data.

Other resources

Publications:

 

Explore groundwater-surface water interaction at the California Water Library

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