DEVELOPING A PROTOCOL TO DESCRIBE AND DELINEATE EPISODIC STREAM PROCESSES ON ARID LANDSCAPES FOR PERMITTING SOLAR POWER PLANTS

Like their perennial, temperate-region counterparts, episodic streams in arid and semi-arid (dryland) areas transport and disperse water, sediment, seed and organic matter, and provide refugia – processes that collectively produce habitat values and biodiversity that are considerably higher than in adjacent uplands. But episodic streams are more prone to flash floods, debris flows, rapid channel switching, and rapid bank erosion.

Large-scale solar power plants will eventually cover thousands of acres in dryland regions of California. Drainage reconfigurations for these projects greatly modify the watershed’s morphology often with detrimental impacts to associated ecosystems. As well, projects that fail to incorporate the site’s fluvial processes into their designs face costly remediation measures to protect the project’s performance and capital investments.

Industry and public partners recognize the need to minimize the negative impacts from solar power plant projects in dryland areas. Although the relationship between habitat and physical/hydrological processes is much better understood in perennial than in episodic stream systems, and few reliable protocols exist for describing and delineating processes in dryland streams, nevertheless, many of the concepts, theories, and practices used in design and described in permit applications for sites in ephemeral landscapes is based on those used in perennial systems. This problematic information gap often overlooks or misinterprets critical ecological or physical factors, leading to delays in the permitting process or inappropriate project designs.

To address this shortcoming, this project, funded by the California Energy Commission, will: 1) produce a scientifically based, geomorphic and ecological stream delineation method for project applicants to use to design and develop sustainable, low-impact projects in dryland environments; 2) provide oversight agencies a rigorous and consistent method to evaluate proposed projects and mitigation; and 3) provide a formalized tool with broad application for use in siting and permitting any development project, developing land use and resource management plans, or evaluating land use and resource management practices in ephemeral stream environments.