Edwards Aquifer and the Endangered Species Act

Congress passed the Endangered Species Act (ESA) in 1973 to address growing concerns over the rate of disappearance of sensitive plant and wildlife species in the United States. The purpose of the Act was to "provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved and to provide a program for the conservation of such [species]." Under the ESA it is unlawful to "harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect" listed species without a permit from the United States Fish and Wildlife Service (USFWS). These unlawful acts are defined as "take" and include any action that may significantly modify a species' habitat, and consequently disrupt essential life processes such as breeding, feeding, etc. For many threatened and endangered species the US Fish and Wildlife Service defines its critical habitat, and in the case of many of the Edwards Aquifer listed species, also defined springflow values below which "take" occurs.

A Habitat Conservation Plan (HCP) is a planning document required when a party applies for an incidental take permit. "Incidental take" is the lawful taking of a listed species through a permitted activity. A HCP acts as an agreement between a non-Federal partner and the US Fish and Wildlife Service to encourage conservation and recovery of a species by minimizing the effects of lawful takings, while allowing development or continued use of a habitat. The Edwards Aquifer Authority is a groundwater district which acts as the governing body of the Edwards Aquifer and as such, took action to develop a HCP for listed species within the aquifer. The
fountain darter (Etheostoma fonticola), Comal Springs riffle beetle (Heterlmis comalensis), Comal Springs dryopid beetle (Stygoparnus comalensis), San Marcos gambusia (Gambusia georgei), San Marcos salamander (Eurycea nana), Texas wild-rice (Zizania texana), Texas blind salamander (Eurycea rathbuni), and Peck's cave amphipod (Stygobromus pecki) are species listed under the ESA that require various minimum springflows to survive.

The
USFWS San Marcos and Comal Springs Recovery Plan (1993) designated minimum springflows considered as take for the eight T&E species listed above. The Draft Edwards Aquifer Habitat Conservation Plan (EAHCP), (submitted to the USFWS in 2005*), proposed modifications to these threshold levels based on new research. When springflow falls below these defined levels, harm or "take" occurs and triggers corrective action by the Edwards Aquifer Authority in the form of reduced groundwater withdrawals. The table below indicates the minimum springflows below which take occurs under the USFWS Plan and the Draft EAHCP.  The springflows for "potential legitimate risk to population" is the level at which there is a potential for serious injury to the population due to loss of habitat.

*The Draft EAHCP was not approved by the USFWS, however it represents newer research than the 1993 USFWS study.


Table of USFWS and Draft EAHCP definitions of take for selected species at Comal Springs Table of USFWS and Draft EAHCP definitions of take for selected species at San Marcos Springs
  USFWS official "take" determination for selected species at Comal Springs and
  proposed modified minimum springflows by the draft EAHCP.
  USFWS official "take" determination for selected species at San Marcos Springs and
  proposed modified minimum springflows by the draft EAHCP.


  

Note: In 2006 the USFWS inititiated a process to develop a new HCP, referred to as the Edwards Aquifer Recovery Implementation Plan, which should be submitted to USFWS for approval by 2011. This plan may modify the levels delineated in the 2005 Draft EAHCP, as that plan was criticized for its failure to protect species during drought conditions comparable to the drought of record (1947-1957).

The graphs below depict the number of days per year at which the springflow at Comal Springs and San Marcos Springs fell below the minimum level defined as "take" by the US Fish and Wildlife Service and Draft Edwards Aquifer Habitat Conservation Plan. Note the drought of record and its effect on species take.



Graph of number of days per year that take occurred at Comal Springs
Number of days per year that flow at Comal Springs dropped below the level defined as "take" by the USFWS and Draft EAHCP [Figure: Houston Advanced Research Center using USGS data].


Graph of number of days per year that take occurred at San Marcos Springs
Number of days per year that flow at San Marcos Springs dropped below the level defined as "take" by the USFWS and Draft EAHCP [Figure: Houston Advanced Research Center using USGS data].




Resources:

Draft Edwards Aquifer Habitat Conservation Plan

San Marcos and Comal Springs Recovery Plan

USFWS Habitat Conservation Plan under the ESA
 
USGS Edwards Aquifer Resources


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