HEFR as hydrology analysis tool HEFR: Hydrology-Based Environmental Flow Regime Strengths and Weaknesses Strengths Uses readily available data (i.e. gage records) Relatively simple to calculate (nice tools) Weaknesses Lack of theoretical basis (linkage of a particular statistic to environmental health). Has not been applied anywhere Specificity - most matrix methods give a range for each criteria, HEFR is specific; reporting a single number implies that only that number is protective of the environment. The precision of the numbers is not justified by the method. Sensitive to flow separation method and period of record. The values in the matrix will change depending on the parameters used in the analysis and the period selected, even in cases where the historical flows describe basically natural conditions. There is very low confidence in the tables produced by the HEFR method alone describing a flow regime adequate to support a sound ecological environment without considering other environmental factors (biology, water quality and geomorphology). Questions for BBEST Pick a period Pre-Impoundment Post-Impoundment Current Conditions Period of Record Pick a definition for wet, average and dry Wet 75% Average 50% Dry 25% Pick a statistical method (original or frequency‐based) If frequency based, then define frequency HEFR and the Flow Regime Components Subsistence flows? Base flows? Pulse flows? Flood flows?