Improved eco-hydrological classification of rivers

Abstract

The flow regime is recognized as a key factor determining biological and physical processes and characteristics in rivers. Because of this, there is interest in classification and regionalization of rivers in order to delineate patterns in flow regime character at landscape scales. The River Environment Classification (REC) is an a priori mapped classification of rivers. The REC is based on a hierarchical model of 'controlling factors', which are assumed to be the dominant causes of variation in physical and biological characteristics of rivers at a variety of spatial scales. The first and second levels of the REC are based on climate and topography and are expected to discriminate rivers according to differences in their flow regimes. Classes are assigned to individual 'sections' of the river network based on categorical description of the climate and topography of each section's unique watershed. This paper describes a test of the REC's ability to explain variation in hydrological character of rivers. Flows that were measured continuously at 335 sites distributed throughout New Zealand were summarized by 13 flow variables and were classified using the REC. Principal components analysis was used to show that the REC classes have distinctive flow regime characteristics. We quantified the classification strength (i.e. the extent to which the mean between-class inter-site dissimilarity exceeds the mean within-class inter-site hydrological dissimilarity) of the REC based on the 13 flow variables. The classification strength of the REC was greater than for two existing regionalizations and a classification that is based on climate, but which does not account for the river network. We attribute the increased classification strength of the REC to its explicit consideration of the causes of spatial variation in flow regimes among rivers and its representation of the network spatial structure of rivers.

Flow variability and macroinvertebrate community response within riverine systems

“…Previous studies have demonstrated limited application of ecological data following environmental classification (e.g. Snelder, et al, 2005). Detailed long-term hydrological observations are available for many locations across Europe and North America, in particular, and long-term river flow records have been reconstructed based on climatological data and other proxies (for example Jones and Lister, 1998).…”

A methodology to diagnose the effect of climate change and to identify adaptive strategies to reduce its impacts in conjunctive-use systems at basin scale

“…Moreover, its ability to 28 detect variations in hydrologic characteristics (Snelder et al 2005), invertebrate 29 assemblages (Snelder et al 2004a) and nutrient concentrations (Snelder et al 2004b) has 30 been demonstrated. The REC is based on a hierarchical scheme of controlling factors (or 31 classification levels) that are assumed to be the dominant causes of variation in the 32 physical and biological characteristics of rivers at a variety of spatial scales.…”

“…Therefore, 33 different classification solutions are possible using the same schema of controllingfactors, with the choice of level depending upon the objective. In particular, the first and 1 second levels, "climate" and "source-of-flow" respectively, were those used to 2 discriminate rivers according to their differences in flow regime (Snelder et al 2005). which allowed their agreement to be tested.…”

Implementation of an eco-hydrological classification in Chilean rivers

“…Methods based on regionalization, also known as ecoregions, respond to a physical focus which considers the control variables of fl uvial processes and their patterns (González del Tánago & García de Jalón 2006;Bailey et al 1978). The ecoregions are homogeneous zones with regard to certain characteristics or parameters on a determined spatial scale (Snelder et al 2005;Omernik & Bailey 1997;Bailey et al 1978). Snelder and Biggs (2002) pointed out that these ecoregions are unable to represent the longitudinal gradients in a river ecosystem, which were synthesized in the River Continuum Concept (Vannote et al 1980); therefore the use of such ecoregions for river classifi cation are limited.…”

“…Snelder and Biggs (2002) developed the River Environmental Classifi cation (REC) to classify the rivers of New Zealand based on the following premises: a) Ecological patterns are dependent on a number of factors associated with the regional scale of the various physical processes; b) The ecological characteristics of rivers respond to fl uvial processes; and c) Classes are assigned to each segment of river geographically independent. In the REC, the typology of each river segment is determined by the hierarchical superposition of controlling factors, which are the principal causes of the spatial variation of the hydrological pattern at a determined scale (Snelder et al 2005, Snelder & Biggs 2002.…”