Case Study

Colorado River Indian Tribe- Chemehuevi Indian Tribe: Floating Vegetated Islands and Traditional Ecological Knowledge for Water Quality Data Collection and Control of Harmful Algae Blooms


Case Study: Regional Sustainable Environmental Science: Floating Vegetated Islands and Traditional Ecological Knowledge for Water Quality Data Collection, and Control of Harmful Algae Blooms

The Lower Colorado River Basin, traditional homelands of the Colorado River Indian Tribe (CRIT) and Chemehuevi Indian Tribe (CIT), has experienced harmful algae blooms, polluted water quality, and a disturbance of natural ecosystem function due to a history of hydromodifications along the river and upstream pollution. The Colorado River spans 1,450 miles, draining an expansive watersheds of 7 U.S. states from the Rocky Mountains to the Gulf of California. The Tribal waterways and ecosystems of CRIT and CIT are located on the far southwestern portion of the river basin, and have been particularly impacted by dams, channelization, and bank armoring along the Colorado River. These hydromodifications have created conditions for excessive runoff of pollutants such as nutrients, pharmaceuticals, and inorganics. Such pollutants have created and unhealthy riparian ecosystem conducive to the growth of blue green algae, Cyanobacteria, which creates Harmful Algae Blooms (HABs) via growth from the excess nutrients which results in health threatening toxic levels of the algae in the water. Accordingly, the CRIT and CIT, in partnership with EPA Region 9, implemented a floating vegetative island pilot project to identify and define qualitative and quantitative early indicators of riparian ecosystem function, and the effectiveness of these islands to protect and reduce the nutrient loads and resulting HABs.

The project was used to measure and mitigate the amount of Cyanobacteria causing HABs within two selected monitoring sites using the vegetated island method, which has been proved in controlled experiments to increase nitrogen removal in aquatic ecosystems. After two islands were constructed from recycled plastics, selected plants were placed into each island, and each island was equipped with two instrument probes for remote sensing and imagery data, with additional measurements obtained upstream and downstream of the floating islands. In addition to water quality data loggers that were attached in the water column below the island, the project also attached POCIS data samplers under each floating island to monitor Microcystin data associated with HABs. Photographs were taken to monitor plant growth at each site, and data collected were compared and correlated to alterations in water quality and ecosystem function.

This data collection process enabled CRIT, CIT, and EPA Region 9 to create landscape level metrics for different ecosystem types and interpret spatial trends in water quality representing increase or decrease in pollutants, and potential proliferation of algal blooms. This research was then used to evaluate, and provide input to Tribal, federal, state, and private management programs with information to prevent land use practices that destroy ecosystems and improve best management practices to monitor and reduce HABs.

How Did They Do It? Applicable Tribal-FERST Tools 
CRIT, CIT, and EPA Region 9 recognized the threat to Tribal natural resources and determined a strategy to monitor and combat this issue.  CRIT CIT and EPA Region 9 recognized that the altered and disturbed riparian and terrestrial ecosystem within the Lower Colorado River was not fully providing the ecological services required to meet nutritional, cultural, societal, and economic needs of the Tribal community. These pollution contaminants from anthropogenic activities and naturally occurring toxins were causing HABs that were known to have impacts to human health and ecosystem quality. This recognition highlighted the need for a project to evaluate and manage this ecosystem proactively and gather data and understand the relationship between water quality and riparian functional condition to allow environmental managers to effectively manage and monitor for water quality in the region.   
CRIT and CIT partnered with EPA to outline a scientific approach for two floating vegetative wetlands.  The scientific approach included ten research tasks for establishing potential condition using CRIT and CIT Traditional Environmental Knowledge (TEK), data monitoring, analysis, presentations on the outcome of the research, and continuation of the study.  
 CRIT, CIT, and EPA complete a ten-step research process to collect and analyze data, modify sampling and construction techniques, and communicate to stakeholders in order to improve land management programs. The RESES study concluded that floating vegetated islands are able to absorb nutrients and trace metals from waterways, improve ecological physical function process, and work best when placed in backwater areas far from high winds and wave action. Observations in respect to cyanobacteria concluded that cyanobacteria/blue-green algae/HABs indicate the degradation of stream and wetland ecosystem physical functioning processes, cyanobacteria is a leading indicator and driver for improving degraded aquatic ecosystems, and cyanobacteria increases in toxicity when oxygen is depleted. The most efficient means of reducing and preventing HABs is to improve ecological functions from source water and the receiving water areas. Restoration objectives and approaches that have been suggested following this report include controlling invasive vegetation, planting native trees and salt tolerant plants, and restoring natural watershed condition, stream plant and animal communities, stream bank erosion, and reconnecting the stream channel to its floodplain. This project successfully provided stakeholders and decision makers with improved scientific information, improved approaches, and tools to assess, predict and manage risk of nutrients, HABs, associated toxicity events, and the resultant ecological, health, and economic impacts.  EPA Office of Research and Development published the results from this study in a publicly accessible report to document their process and encourage further data collection on floating vegetative islands in water quality monitoring and restoration efforts. The report in its entirety can be found following this link: (Hyperlink: RESES Report).