Environmental Flows and Levels (EFLs) describe the quantity, quality, timing and range of variability of water flows and levels required to sustain or restore freshwater and estuarine ecosystems and the functions and services they provide. This principle is based on the concept that a balance can be achieved between groundwater left in the aquifer to support groundwater-dependent ecosystems (GDEs), and groundwater withdrawal for human uses. To find this balance, scientists and managers study the ecosystem to determine the following: 
  1. The amount and timing of groundwater flow required to support the species and ecosystem processes in the GDEs;
  2. How groundwater flow into the GDEs will be altered under different withdrawal scenarios;
  3. The amount or degree of ecological change expected at different levels of withdrawal; and
  4. The acceptable level of change in ecological conditions and ecosystem function.
The Nature Conservancy has been working with the U.S. Forest Service to develop and test methods for setting EFLs for GDEs. Learn more by reading our fact sheet at right, explore where we work using the navigation above, and learn more about the USFS' development of protocols for finding and assessing GDEs.
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