USGS Scientific Investigations Report 2010–5016 Development of an Environmental Flow Framework for the McKenzie River Basin, Oregon

Table 8. Indicators of Hydrologic Alteration parameters used to quantify hydrologic changes resulting from dams and canals, McKenzie River, Oregon.

[Data from The Nature Conservancy (2007)]

Hydrologic Alteration Indicators (IHA) parameter group	Hydrologic parameters	Ecosystem influences
1. Magnitude of monthly water conditions	Mean or median value for each calendar month	* Habitat availability for aquatic organisms * Soil moisture availability for plants * Availability of water for terrestrial animals * Availability of food/cover for fur-bearing mammals * Reliability of water supplies for terrestrial animals * Access by predators to nesting sites * Influences water temperature, oxygen levels, photosynthesis in water column
2. Magnitude and duration of annual extreme water conditions	Annual minima, 1-day mean Annual minima, 3-day means Annual minima, 7-day means Annual minima, 30-day means Annual minima, 90-day means Annual maxima, 1-day mean Annual maxima, 3-day means Annual maxima, 7-day means Annual maxima, 30-day means Annual maxima, 90-day means Number of zero-flow days Base flow index: 7-day minimum flow/annual mean flow	* Balance of competitive, ruderal, and stress-tolerant organisms * Creation of sites for plant colonization * Structuring of aquatic ecosystems by abiotic versus biotic factors * Structuring of river channel morphology and physical habitat conditions * Soil moisture stress in plants * Dehydration in animals * Anaerobic stress in plants * Volume of nutrient exchanges between rivers and floodplains * Duration of stressful conditions such as low oxygen and concentrated chemicals in aquatic environments * Distribution of plant communities in lakes, ponds, floodplains * Duration of high flows for waste disposal, aeration of spawning beds in channel sediments
3. Timing of annual extreme water conditions	Julian date of each annual 1-day maximum Julian date of each annual 1-day minimum	* Compatibility with life cycles of organisms * Predictability/avoidability of stress for organisms * Access to special habitats during reproduction or to avoid predation * Spawning cues for migratory fish * Evolution of life history strategies, behavioral mechanisms
4. Frequency and duration of high and low pulse	Number of low pulses within each water year Mean or median duration of low pulses (days) Number of high pulses within each water year Mean or median duration of high pulses (days)	* Frequency and magnitude of soil moisture stress for plants * Frequency and duration of anaerobic stress for plants * Availability of floodplain habitats for aquatic organisms * Nutrient and organic matter exchanges between river and floodplain * Soil mineral availability * Access for waterbirds to feeding, resting, reproduction sites * Influences bedload transport, channel sediment textures, and duration of substrate disturbance (high pulses)
5. Rate and frequency of water condition changes	Rise rates: Mean or median of all positive differences between consecutive daily values Fall rates: Mean or median of all negative differencesbetween consecutive daily values Number of hydrologic reversals	* Drought stress on plants (falling levels) * Entrapment of organisms on islands, floodplains (rising levels) * Desiccation stress on low-mobility stream edge (varial zone) organisms