Re-thinking Environmental Flows: From Allocations and Reserves to Sustainability Boundaries.

**Richter, B.D. 2009. Rivers Research and Applications 25: 1-12.**

ABSTRACT: Attempts to implement environmental flows have encountered many obstacles. Many water allocation systems include a system of prioritization among water uses that generally does not favor environmental flow protection, or do not allow for protection of high flow events for ecological purposes. It has proven very difficult to implement complicated environmental flow prescriptions that attempt to mimic natural flow variability within water allocation systems. Additionally, many water allocation systems do not adequately address interconnections between surface water and groundwater, or releases from dams. It is time to re-think our approaches to protecting environmental flows. As with water quality protection, environmental flows should be viewed not as an ‘‘allocation’’ of water, but rather as a desirable outcome of integrated management of water and land resources for long-term sustainability. In this sense, environmental flows should be managed in a manner similar to water quality protection, in which the influences of diverse land and water use activities are regulated to ensure that the ecological and social values of water are optimized. Both water quality and environmental flow management protect a vast array of important social benefits that are sustained by managing for healthy freshwater ecosystems. In this paper I offer a definition of sustainable water management that explicitly recognizes the fact that society derives substantial benefits both from out-of-stream extractions of water as well as by maintaining adequate flows of water within freshwater ecosystems. To help facilitate sustainable water management, a

‘‘Sustainability Boundary Approach’’ is described for use in setting quantitative water management goals. When the cumulative hydrologic impacts of water and land uses are managed within these sustainability boundaries, the full array of values associated with water can be more fully realized.