How much water does a river need?

Abstract

1. This paper introduces a new approach for setting streamflow‐based river ecosystem management targets and this method is called the ‘Range of Variability Approach’ (RVA). The proposed approach derives from aquatic ecology theory concerning the critical role of hydrological variability, and associated characteristics of timing, frequency, duration, and rates of change, in sustaining aquatic ecosystems. The method is intended for application on rivers wherein the conservation of native aquatic biodiversity and protection of natural ecosystem functions are primary river management objectives. 2. The RVA uses as its starting point either measured or synthesized daily streamflow values from a period during which human perturbations to the hydrological regime were negligible. This streamflow record is then characterized using thirty‐two different hydrological parameters, using methods defined in Richter et al. (1996). Using the RVA, a range of variation in each of the thirty‐two parameters, e.g. the values at ± 1 standard deviation from the mean or the twenty‐fifth to seventy‐fifth percentile range, are selected as initial flow management targets. 3. The RVA targets are intended to guide the design of river management strategies (e.g. reservoir operations rules, catchment restoration) that will lead to attainment of these targets on an annual basis. The RVA will enable river managers to define and adopt readily interim management targets before conclusive, long‐term ecosystem research results are available. The RVA targets and management strategies should be adaptively refined as suggested by research results and as needed to sustain native aquatic ecosystem biodiversity and integrity.

Large wood debris recruitment on differing riparian landforms along a Gulf Coastal Plain (USA) stream: a comparison of large floods and average flows

“…In addition to debris recruitment, large floods probably provide a number of additional ecological benefits to streams and riparian areas, including stimulating recruitment of aquatic fauna, maintenance of habitat heterogeneity and providing pulses of biologically important material that stimulate productivity (Michener and Haeuber, 1998). This is consistent with the growing recognition that diverse natural hydrological regimes are important in controlling the structure and function of stream ecosystems (Decamps et al, 1995;Gore and Shields, 1995;Stanford et al, 1996;Wootton et al, 1996;Richter et al, 1997). While large floods are infrequent, and thus unpredictable events, their occurrence can be linked to long-term variations in climate.…”

Macroinvertebrate community response to inter‐annual and regional river flow regime dynamics

“…A total of 201 hydrological variables were derived for each site from the raw river flow time-series based on the Range of Variability Approach (RVA) and Indicators of Hydrological Alteration (IHA) methodology and its derivatives (Richter et al, 1996;Richter et al, 1997;Olden and Poff, 2003). These variables were derived from the raw daily, monthly or annual series (as appropriate) independently of the regime classification outlined above and were only transformed if required to comply with the underlying assumptions of parametric statistical tests (e.g., a normal distribution).…”

River Hydrology, Flow Alteration, and Environmental Flow

“…The widely accepted natural flow paradigm (sensu Poff et al 1997), where the flow regime of a river, comprising the five key components of variability, i.e., magnitude, frequency, duration, timing, and rate of change, is recognized as central to sustaining biodiversity and ecosystem integrity (Poff and Ward 1989;Karr 1991;Richter et al 1997;Rapport et al 1998;Rosenberg et al 2000). These components can be used to characterize the entire range of flows and specific hydrologic phenomena, such as floods or low flows, which are critical to the integrity of river ecosystems.…”