»Surface Water Quality and Surface Water Dynamics
Vital Signs Included in Protocol
- Surface water quality
- Aquatic invertebrates
- Surface water dynamics
- Persistence of seeps and springs
- Lake Amistad elevation (not measured by CHDN)
Parks Where Protocol Will Be Implemented
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AMIS, BIBE, CAVE, GUMO
Justification/Issues Being Addressed
In the CHDN, the Rio Grande and Amistad International Reservoir are the major sources of surface water for humans and aquatic-biological communities along the U.S.-Texas and Mexico border (Porter et al. 2009). Smaller perennial streams and certain intermittent streams provide additional sources of water for park biota and human visitors. Although limited in extent, these microcosms can add considerably to the biodiversity of arid and semi-arid landscapes. However, most streams in the network are intermittent and small, difficult to sample, or perceived as having relatively low monitoring priority. In contrast, several perennial streams in BIBE and GUMO (e.g., McKittrick Creek), though not officially designated as Outstanding Natural Resource Waters (ONRW), are considered critically important to their respective parks. The quality of water in the Rio Grande is of particular concern, given its economic and ecological role it plays in the border region and recent exposure to pollutants (International Boundary and Water Commission 1994, Lee and Wilson, 1997, Van Metre et al. 1997). Monitoring the relevant vital signs will demonstrate whether or not park water quality is being protected or maintained and indicate whether restoration is required. The only impaired water under Section 303(d) of the Clean Water Act in CHDN occurs on Segment 2306 in the Rio Grande. Additionally, chlorophyll a and total phosphorus are listed as Concern Levels for Segment 2306, and nitrate is listed as a Concern Level for Sement 2305 (Amistad Reservoir); http://www.tceq.state.tx.us/compliance/monitoring/water/quality/data/08twqi/twqi08.html.
Lake Amistad (a Rio Grande reservoir) is the largest and most heavily used water body in the network. This reservoir receives significant levels of monitoring (including continuous lake elevation) by other agencies and programs within NPS. Thus, we do not plan to sample Lake Amistad, but we will report on trends of appropriate data sets.