A General Protocol for Restoration of Regulated Rivers

Abstract

Large catchment basins may be viewed as ecosystems in which natural and cultural attributes interact. Contemporary river ecology emphasizes the four‐dimensional nature of the river continuum and the propensity for riverine biodiversity and bioproduction to be largely controlled by habitat maintenance processes, such as cut and fill alluviation mediated by catchment water yield. Stream regulation reduces annual flow amplitude, increases baseflow variation and changes temperature, mass transport and other important biophysical patterns and attributes. As a result, ecological connectivity between upstream and downstream reaches and between channels, ground waters and floodplains may be severed. Native biodiversity and bioproduction usually are reduced or changed and non‐native biota proliferate. Regulated rivers regain normative attributes as distance from the dam increases and in relation to the mode of dam operation. Therefore, dam operations can be used to restructure altered temperature and flow regimes which, coupled with pollution abatement and management of non‐native biota, enables natural processes to restore damaged habitats along the river's course. The expectation is recovery of depressed populations of native species. The protocol requires: restoring peak flows needed to reconnect and periodically reconfigure channel and floodplain habitats; stabilizing baseflows to revitalize food‐webs in shallow water habitats; reconstituting seasonal temperature patterns (e.g. by construction of depth selective withdrawal systems on storage dams); maximizing dam passage to allow recovery of fish metapopulation structure; instituting a management belief system that relies upon natural habitat restoration and maintenance, as opposed to artificial propagation, installation of artificial instream structures (river engineering) and predator control; and, practising adaptive ecosystem management. Our restoration protocol should be viewed as an hypothesis derived from the principles of river ecology. Although restoration to aboriginal state is not expected, nor necessarily desired, recovering some large portion of the lost capacity to sustain native biodiversity and bioproduction is possible by management for processes that maintain normative habitat conditions. The cost may be less than expected because the river can do most of the work.

Effects of experimental flooding on riverine morphology, structure and riparian vegetation: The River Sp�l, Swiss National Park

“…However, only recently has the importance of multiple sequential floods been emphasized for restoring the integrity of rivers downstream of reservoirs (Stanford et al, 1996), reflecting the premise of the natural flow regime as an inherent property of flowing waters (Poff et al, 1997). For instance, Kondolf and Wilcock (1996) suggested that two flood flows per year were necessary for maintaining habitat turnover of riparian areas.…”

“…The present study shows the results of multiple experimental floods over a three year period on the morphology of a canyon confined river downstream of a reservoir used for hydropower production. The floods were experimental in the sense that individual floods varied in magnitude depending on the particular needs at the time; an idea in line with adaptive management perspectives (Stanford et al, 1996).…”

The Scope of Uncertainties in River Restoration

“…Brookes and Sear, 1996;Gilvear, 1999;Kondolf, 2000;Sear, 1994), ecosystem theory (e.g. Richards et al, 2002;Stanford et al, 1996), hydraulic engineering (e.g. Shields, 1996) and detailed design procedures (Miller et al, 2001;Shields et al, 2003;Wheaton et al, 2004b).…”

“…Using a 'process-based' approach can make intuitive sense for passive approaches to restoration. For example, providing fl ow releases from a reservoir to mimic a natural hydrograph and encourage mobilisation and reorganisation of sediments, may restore the processes that 'allow the river to do the work' (Stanford et al, 1996;Trush et al, 2000). However, active approaches are considered favourable when natural or passive recovery may take an unacceptably long time (Montgomery and Bolton, 2003).…”

Hydrological and Hydraulic Aspects of Restoration Uncertainty for Ecological Purposes

“…A range of variation of the indices may then be set, based upon ±1 standard deviation from the mean or between the 25th and 75th percentiles. Variability in stream fl ow is essential in sustaining ecosystem integrity (long term maintenance of biodiversity and productivity) and resiliency (the capacity to endure natural and human disturbances - Stanford et al, 1996). This method is intended to defi ne interim standards, which can be monitored and revised.…”