The Shifting Roles of the EU, the US and California
Edited by David Vogel and Johan Swinnen
Chapter 4: Rivers of Diversity: Water Regulation in California and the EU
Gabrielle Bouleau and Matt Kondolf 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. The 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, 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 (Knox and Scheuring, 1991). 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 (Naiman et al., 2005). 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...
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