Wetland Flora, Fauna, and Water Quality Assessment at Topock Marsh
Historically, the habitats within what is now the Havasu National Wildlife Refuge (Havasu NWR) were created and maintained by the dynamics of the unpredictable Colorado River. However, throughout the 20th century, the river has been regulated through a series of dams and levees, which has changed the dynamics to a late successional environment less susceptible to the unpredictable floods and droughts that characterized the unregulated river. Under this environment, many fish and wildlife species adapted to the unregulated conditions became threatened, endangered, or of special concern to Federal and State resource management agencies [Department of the Interior (DOI), 2009]. Under an Executive Order, President Franklin Roosevelt established the Havasu NWR in 1941 as a refuge and breeding ground for migratory birds and other wildlife.
Over the years, various canals, dikes, and ditches were constructed to help maintain the marshes original productivity (Shoreline, 2006). However, in addition to the water management infrastructure aging over the years, the physical characteristics and overall management of the Colorado River have changed due to flooding, additional water withdrawals, flood control, and hydropower-generation. Add to the mix that the Havasu NWR has frequently reached or exceeded its annual entitlement for diversion of water from the Colorado River, and subsequently the FWS requested an Infrastructure Improvement Project (IIP) to help protect the habitat and species that use the Refuge (DOI, 2009). During construction of the new Firebreak Canal as part of the IIP, water levels dropped considerably lower than normal, so FWS requested USGS FORT scientists to determine how the flora and fauna within the marsh responded to those low flow conditions as well as how they fared once water levels returned to normal. The data collected under this initial agreement was then to be used as background data for managing water in Topock Marsh in the future. In 2013, FWS again approached USGS FORT and requested additional sampling of the marsh and a decision support tool they could use, based on the previously and currently collected data, to determine the best way to manage the water levels to optimize endangered wildlife species habitat. A Decision Support System (DSS) is to be developed, for use by Havasu NWR to compare habitat availability associated with hydrologic scenarios. This approach will help FWS use the best available science to determine more effective water management strategies and it will assist with developing the mandated Havasu National Wildlife Refuge's Comprehensive Conservation Plan (CCP).
This project will help Fisheries and Aquatic Resources Programs to:
- Provide scientific understanding of the biology, health, and diseases of aquatic organisms;
- Provide scientific information and guidance that contribute to the conservation and recovery of aquatic species at risk;
- Provide scientific information about the diversity, species interactions, and life history strategies that affect the condition and dynamics of aquatic communities;
- To understand functional relationships among aquatic species and their habitats;
- Provide science in support of restoration and mitigation of altered aquatic systems;
- Provide scientific support, technical assistance, and information transfer to DOI bureaus and other governmental agencies, and NGOs;
- Improving the level of understanding of the capabilities and the effective management of wetlands in the southwestern U.S. for improved water quality, wetland habitat, and diverse, healthy ecosystems;
- Evaluating potential hazards and developing cost-effective techniques for maintaining healthy, sustainable wetland systems;
- Developing and applying new techniques for the restoration of degraded natural riparian and wetland ecosystems; and
- Providing technical assistance and outreach for client DOI agencies, other government agencies, and NGOs.