Legitimizing Fluvial Ecosystems as Users of Water: An Overview

Abstract

We suggest that fluvial ecosystems are legitimate users of water and that there are basic ecological principles guiding the maintenance of long-term ecological vitality. This article articulates some fundamental relationships between physical and ecological processes, presents basic principles for maintaining the vitality of fluvial ecosystems, identifies several major scientific challenges and opportunities for effective implementation of the basic ecological principles, and acts as an introduction to three specific articles to follow on biodiversity, biogeochemistry, and riparian communities. All the objectives, by necessity, link climate, land, and fresh water. The basic principles proposed are: (1) the natural flow regime shapes the evolution of aquatic biota and ecological processes, (2) every river has a characteristic flow regime and an associated biotic community, and (3) aquatic ecosystems are topographically unique in occupying the lowest position in the landscape, thereby integrating catchment-scale processes. Scientific challenges for the immediate future relate to quantifying cumulative effects, linking multidisciplinary knowledge and models, and formulating effective monitoring and assessment procedures. Additionally, forecasting the ecological consequences of changing water regimes is a fundamental challenge for science, especially as environmental issues related to fresh waters escalate in the next two to three decades.

Nitrous oxide fluxes from the littoral zone of a lake on the Qinghai-Tibetan Plateau

“…We considered this related to the drastic hydrological dynamics in the littoral zones of lakes. In fact, for riparian or littoral zones, the hydrological regime often entails large temporal fluctuations in water table elevation (Naiman et al 2002;Nilsson and Svedmark 2002), which significantly influence the process of denitrification and N 2 O emissions (Hefting et al 2003). Therefore, in the littoral zones of Lake Huahu, the complicated temporal variation of N 2 O emissions should be partly explained by temporal variation of standing water depths (Table 1) The estimation of N 2 O emissions is very difficult due to technical difficulties in measurements and the large spatiotemporal variation in N 2 O production, consumption, and transport rates (Hefting et al 2003).…”

Nitrous Oxide Emissions from Newly Created Littoral Marshes in the Drawdown Area of the Three Gorges Reservoir, China

“…However, we found that N 2 O emissions were significantly correlated with the fourth component, influenced by water temperatures and soil water content (Table 2). In fact, for riparian or littoral marshes, the hydrological regime often entails large temporal fluctuations in water table elevation (Naiman et al 2002;Nilsson and Svedmark 2002), which significantly influence the process of denitrification and N 2 O emissions (Hefting et al 2003). Therefore, in such littoral marshes of the TGR, the complicated temporal variations of N 2 O emissions should be partly explained by the temporal variation of the standing water table and thermal conditions in the growing season.…”

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

“…Temporal and spatial variability in river flow is recognised as a fundamental control on instream habitat structure and availability, and riverine ecosystem biodiversity and integrity (Naiman et al, 2002;Richter et al, 2003;Arthington et al, 2006;Dudgeon et al, 2006). Instream faunal communities are adapted to the 'natural' flow regime and the variability in magnitude, frequency, timing and duration of high, low and intermediate flow events (e.g., Jowett and Duncan, 1990;Lytle and Poff, 2004;Monk et al, 2006).…”