Potomac Flow-by Stated Management Objectives (1) estimate the amount and quality of biotic habitat available at different flow levels, particularly as it relates to the current minimum flow-by requirement (2) determine what instream flows are required to protect adequate habitat and to prevent a reduction of any representative important species beyond levels from which it cannot recover and re-colonize the area following a drought event.

Potomac Flow-by Stated Management Objectives Many scientific issues to accomplish this objective. (1) estimate the amount and quality of biotic habitat available at different flow levels, particularly as it relates to the current minimum flow-by requirement (2) determine what instream flows are required to protect adequate habitat and to prevent a reduction of any representative important species beyond levels from which it cannot recover and re-colonize the area following a drought event.

Ecological Theory Disturbance = discrete event that causes mortality, alters resources, etc. Extreme event within natural range of variation (e.g., severe drought)

System state Resistance and Resilience Time Noise: - biological - sampling Time System state

3 “parameters” System State Time scale to measure system state, recovery Nature of disturbing force Management objectives direct how these 3 parameters are characterized and dictate data requirements. System state Time

System State Ecological Scale –Single vs. many species –Ecosystem process Ecological Grain –Fine: Abundance –Coarse: Presence/Absence System state Time

System State, 2 examples 1. Population Abundance –Population numbers recover after disturbance to “dynamic equilibrium” –Requires pre-disturbance population estimates –Population data naturally noisy, very dependent on... Where samples taken When samples taken (time since disturbance) Spatial scale of “study area” relative to movement of individuals (metapopulation dynamics) Antecedent population dynamics Life history of species, life stages affected Time System state

System State, 2 examples 2. Community Persistence –All species persist within study area (i.e., stay “in the game”) –Data less noisy (coarser grain) –Target most sensitive species for population estimates? Time System state

Nature of Disturbance Specific components –Magnitude or intensity –Frequency (Once per year? Decade?) –Timing (Spring? Summer?) –Duration Characterize relative to ecological response variables Data quality to characterize? Time System state

Disturbance Frequency/Magnitude Natural “100 yr” drought? Time (years) System state Time (years) System state “Anthropogenic” droughts?

Management Objectives (1) estimate the amount and quality of biotic habitat available at different flow levels, particularly as it relates to the current minimum flow-by requirement (2) determine what instream flows are required to protect adequate habitat and to prevent a reduction of any representative important species beyond levels from which it cannot recover and re-colonize the area following a drought event. Is goal to provide a “high degree of protection” [risk assessment] or simply “quantify habitat at low flows?” CAVEAT: Reduction in “habitat area” per se does not necessarily translate directly into linear biological response. Must consider aspects of system that allow for resilience: –species behavior (movement) and tolerance –landscape scale (refugia, connectivity)

Points for Potomac What is “System State” of interest? Dynamic River System! –Lots of natural flow variation, both intra- annually and inter-annually –Lots of attendant biological variation (“noise”) –Ability to detect response and recovery to “drought” depends on biological data (which appear to be limited) –Ecological Principle -- keep system within natural range of variation and “system” will “persist”.