Frequency of occurrence of flow regime components
a hydrology-based approach for environmental flow assessments and water allocation for the environment
Sergio Salinas Rodríguez (WWF-Mexico, TU Delft - Water Resources)
Rafael Sánchez-Navarro (Scientific and Technical Review Panel-Ramsar Convention)
Jorge E. Barrios-Ordóñez (National Water Commission)
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Abstract
Hydrological methodologies are the most efficient approaches for environmental flow (eflow) assessments. This paper presents a hydrological methodology for determining eflows in rivers with scarce development to promote proactive environmental water allocations that limit flow alteration and unsustainable water use. The analysis includes the natural intra-annual and inter-annual ranges of flow variability. Eflows are determined based on four hydrological low-flow conditions and a flood regime. The main contribution is that the flow regime components are adjusted to a four-tiered environmental objective class system based on a novel “frequency-of-occurrence” approach. The method is applied in three rivers in western Mexico with highly variable flow regimes. The eflows are largely (96%) within the central range of previous implementations, and the outcomes reveal an overall good and acceptable level of the method’s performance (for 83% of the cases R 2 ≥ 0.84, slope = 1 ± ≤ 0.2), consistent with supporting indices of flow variability.
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