1 Rivers of Diversity: Evolving Water Regulation in California and the European Union Gabrielle Bouleau (1), Matt Kondolf (2) (1) UMR G-EAU, Cemagref, 361 rue Jean-François Breton, F-34196 Montpellier, France gabrielle.bouleau@cemagref.fr (2) LAEP, University of California, Berkeley, kondolf@berkeley.edu 1. Introduction Aquatic and riparian areas have long been recognized as biodiversity ‘hotspots’ in the landscape, and thus have been the focus of many environmental regulations. Principal threats to aquatic biodiversity have been water quality degradation from pollution, morphological modifications and reduction in water quantity from diversions for human uses. Adequate flows in rivers are increasingly recognized as essential to maintain or restore aquatic ecosystems 1 , and such ecosystem flows must be implemented in the context of water rights. With changes in runoff regimes anticipated from climate change, threats to aquatic biodiversity will be severe if water rights and regulations established in past eras cannot be modified to reflect emerging objectives of biodiversity and ecosystem health 2 . Rivers and their floodplains support a wide range of conditions (reflecting variations in vegetation, substrate, groundwater levels, frequency and seasonality of inundation, and microclimate), which in turn provide a wide range of habitats and thus support many, diverse species. Riparian zones are arguably the most diverse parts of many landscapes 3 . From a human perspective, rivers and floodplains have multiple functions besides supporting biodiversity: water supply, flood storage and conveyance, groundwater recharge, improvement of water quality, and corridors for wildlife migration. Artificial changes to river morphology (such as straightening for navigation or drainage) reduce habitat complexity. Water diversions reduce river flows, commonly reducing available aquatic habitat, and in extreme cases, drying out rivers. Even less extreme reductions in flows can affect water quality by affecting temperature and reducing dilution of contaminants. The combination of such pressures threatens biodiversity. Regulations targeting water quality have also implications on water quantity through these linkages. To find inspiring examples of regulatory adaptation, scholars often look to comparisons among developed countries of the European Union (EU) and states of the United States of America (US), notably California 4 . Political analysts 5 and environmental historians 6 have 1 G. Mathias Kondolf et al., "Process-Based Ecological River Restoration; Visualizing Three-Dimensional Connectivity and Dynamic Vectors to Recover Lost Linkages," Ecology and Society 11, no. 2 (2006), N LeRoy Poff et al., "River Flows and Water Wars: Emerging Science for Environmental Decision Making," Frontiers in Ecology and the Environment 1, no. 6 (2003), N. Ward, P. Lowe, and H. Buller, "Implementing European Water Quality Directives: Lessons for Sustainable Development," in The Politics of Sustainable Development, ed. S. Baker, et al. (London: Routledge, 1997). 2 Joseph B. Knox and Ann Foley Scheuring, Global Climate Change and California: Potential Impacts and Responses (University of California Press, 1991). 3 Robert J. Naiman et al., Riparia: Ecology, Conservation, and Management of Streamside Communities (Amsterdam: Elsevier Academic Press, 2005). 4 David Vogel, "The Hare and the Tortoise Revisited: The New Politics of Consumer and Environmental Regulation in Europe," in Environmental Policy in the European Union, ed. Andrew Jordan (Earthscan, 2005). 5 Philipp Genschel and Thomas Plumper, "Regulatory Competition and International Co-Operation," Journal of European Public Policy, Volume 4, Issue 4 December 1997 , pages 4, no. 4 (1997), Giandomenico Majone, Regulating Europe (Routledge, 1996), Aseem Prakash and Matthew Potoski, "Racing to the Bottom? Trade, Environmental Governance, and Iso 14001," American Journal of Political Science 50, no. 2 (2006), Sebastiaan Princen, "Trading up in the Transatlantic Relationship," Journal of Public Policy, no. 24 (2004), David Vogel,