摘要:

A programme of research to characterise, classify, and model New Zealand rivers according to hydrological, water quality, and biological properties is introduced. The results are detailed in the accompanying eight research papers. These studies provide the first national perspective on water quality and biology in New Zealand's rivers using a consistent methodology. They are also the first step toward providing managers with robust models for predicting the effects on aquatic biota of changes in flow regimes and catchment land use. A synthesis of the results is given in this paper together with recommendations for riverine ecoregions in New Zealand.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516426

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

How variability indices were determined for 130 sites on New Zealand rivers and the sites were divided into groups based on these indices. Univariate and discriminant analyses were used to identify the catchment characteristics which contributed to flow variability. Climate, as determined by topography, geographic location, and the composition of the regolith (especially water storage capacity and transmissivity characteristics), accounted for a broad regional distribution of groups. Flow variability decreased with catchment size and area of lake and, to a lesser degree, with catchment slope. Relationships were found between flow variability, and morphological and hydraulic characteristics. The longitudinal variability of water depth and velocity increased with flow variability, indicating a more pronounced pool/riffle structure in rivers with high flow variability. Mean water velocity at mean annual low, median, and mean flow was higher in rivers of low flow variability than in rivers of high flow variability. There were strong associations with periphyton communities and trout distribution and abundance and a weak association with benthic invertebrate communities. Water velocity was the most important hydraulic variable; it could be linked to changes in water temperature, benthic invertebrate and periphyton community structure, and trout distribution and abundance.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516427

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In late summer to autumn 1987, 96 rivers throughout New Zealand were sampled in baseflow (< median flow) conditions, usually on three separate occasions. A wide range of water quality determinands were analysed to characterise water quality comprehensively at lower than median flows. River waters in New Zealand range widely in composition, particularly plant nutrients, but tend to be more dilute than world average freshwater (WAFW) because run‐off (specific yield) of water is generally high. Sodium and calcium are the most important cations in New Zealand rivers which can be described as “calcium‐sodium bicarbonate waters”, whereas WAFW is calcium bicarbonate water. Almost all river sites met existing guidelines and standards for drinking water, ecological protection, and freshwater fisheries.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516428

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Baseflow water chemistry in 96 New Zealand rivers was related to selected environmental variables quantifying lithology, land use, topography, and hydrology. The river sites were clustered using five water quality variables: major ions, phosphorus species, organic and nitrogen species, calcium, and nitrate. Eleven site clusters were identified and the differing water quality regimes discussed. The effect of the environmental factors on water quality was investigated using discriminant analysis. The resultant model assigned 73% of the sites to the correct cluster. The most important environmental variables determining water quality were hydrological variables such as specific yield, and proportional areas in the catchment of soft sedimentary rock, intensive pasture (which was negatively correlated with steep slopes and high altitudes), exotic forest, and volcanically derived rock. Multiple regression equations relating individual water quality determin‐ands to these environmental variables were derived. All equations were highly significant (P< 0.0001) andR2values ranged from 0.65 to 0.83 for conductivity and major ion species, and from 0.46 to 0.70 for nitrogen and phosphorus species. These equations could be used to give a rough indication of likely water quality at unsampled sites which would be valuable in a variety of water management situations.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516429

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Visual clarity and apparent colour (hue) of 96 New Zealand rivers was investigated under baseflow (< median flow) conditions. Visual clarity, measured as the horizontal sighting range of a black disk, ranged 40‐fold from 0.25 to 10.75 m. Only 7% of the clarity observations were “low” (black disk range < 1.2 m), whereas 31% were “high” (> 4 m). Visual clarity was strongly related to nephelometric turbidity (r= ‐0.88) but was less strongly related to suspended solids concentration (r= ‐0.77), even though scattering and absorption of light by suspensoids accounted for most (87 % on average) of overall light beam attenuation. Hue, as described in the field while viewing black disk range, varied from the blues of optically pure water to orange in waters with high concentrations of organic material, particularly yellow substance. There was a weak tendency for clear river waters to be blue‐green in hue whereast turbid waters were more typically yellow‐coloured.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516430

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The composition of periphyton communities was assessed over an extensive range of New Zealand river environments during late‐summer low flows. The chemical, hydrological, and watershed characteristics of the sites were determined and broad associations developed between communities and several key variables. Eight communities were identified and 91 sites classified into groups according to the presence of the first seven of these communities. Most were dominated by filamentous periphyton taxa. A taxonomic‐biomass classification was also developed by condensing the site groups into three, more general, classes based on their biomass. Sixty‐eight percent of the sites were in the low‐biomass class (i.e., < 20 g m−2ash‐free dry weight). Twenty‐two environmental characteristics of the sites varied significantly across the periphyton groups indicating strong habitat associations by the periphyton. Conductivity of the water was the most important environmental variable. A discriminant model was tested for each classification using an independent dataset to determine whether the groups or classes could be predicted accurately from environmental factors. The models were moderately successful (50 and 57% correct predictions, respectively), but were only sensitive to major changes in values of individual environmental variables.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516431

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Benthic macroinvertebrates were sampled (seven Surber samples per site) in 88 rivers throughout New Zealand in “runs” (velocity 0.4–0.8 m s−1, depth = 0.3–0.6 m), under autumn baseflow conditions (Q < median). Medians and 10–90 percentiles for the following community level characteristics were: taxa richness, 14 and 7–20(0.7 m−2); Shannon Diversity (H’), 1.33and 0.80–1.90; total density, 1900 and 230–6700 m−2; and total biomass, 0.608 and 0.112–2.932 g AFDW m−2. Invertebrate abundance and taxonomic richness were lowest in rivers with beds of silt or sand, or cobbles overlain with sand deposits. Comparisons of environmental factors between sites grouped by TWINSPAN indicated that the degree of catchment development to improved pasture, water temperature, and level of enrichment (indicated by increased nutrients and periphyton biomass) are important factors affecting invertebrate community structure in New Zealand rivers. Mayflies, stoneflies, and predatory caddisflies were associated with cooler, less enriched, steeper, and more elevated sites than snails, crustaceans, chironomids, and worms. Stonefly biomass was minimal at sites having mean annual temperatures >13°C. The following community characteristics emerged as useful indicators of the level of water enrichment: the Macroinvertebrate Community Index (MCI) and its quantitative analog (QMCI); the presence of some species (e.g.,Zelandoperla decorataandBereoptera roria), and the densities of some widely distributed taxa (e.g.,Deleatidiumspp. andPsilochoremaspp.); percentage predator biomass; and the number of ephemeropteran, plecopteran, and trichopteran taxa (EPT). Sites did not separate out clearly into ecoregions, although rivers with “clean‐water” faunas were more predominant in the South Island than in the North Island. This is thought to reflect the greater degree of development of the North Island catchments.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516432

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Data from runs in 88 rivers throughout New Zealand, and a comparison between areas of contrasting substrate size in the Mohaka River, were used to investigate the influences of physical factors on benthic macroinvertebrates. Substrate size preferences were more clearly demonstrated by the comparison of different substrates in the Mohaka River than between runs in the 88 rivers. Taxonomic richness and densities of most collector‐browsers were highest on small cobble‐boulder substrates. However, filterers and a facultative shredder showed strong preferences for large cobbles and boulders and an undescribed orthoclad showed a strong preference for sand. Among the 80 stony‐bedded rivers, those exposed to maximum flows of < 5×, 5–10×, and 10–20× their median flow during 6 weeks before sampling had similar taxonomic richness, densities, and biomass. In contrast, rivers that had experienced maximum flows of > 20× their median flows had markedly lower median taxonomic richness, density, and biomass than less‐flooded rivers. Among the 51 stony, “non‐flooded” sites, those with 1–30% of their catchments developed to improved pasture had similar community composition to, but higher total biomass than those with < 1% development. However, sites with > 30% catchment development (median = 70%) differed significantly (P< 0.1) from those with less developed catchments: the former had lower diversity, taxonomic richness, numbers of ephemeropteran, plecopteran, and trichopteran species (EPT), and had lower biomass of species that are sensitive to changes in water quality related to eutrophication; they had higher biomass of species that are associated with an abundance of periphyton. Trout biomass was also c. 3‐fold lower than in the rivers with lesser‐developed (1–30%) catchments.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516433

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) populations at 157 riverine sites throughout New Zealand were divided into groups based on species, size, and abundance. The groups were examined to determine significant differences in hydrological, water quality, water temperature, biological, in‐stream habitat, and catchment variables between groups. A discriminant model was developed with nine environmental factors which correctly classified 72% of a subset of 65 sites. Fish species distribution was related to climatic (water temperature), geographical, and hydrological factors, whereas fish abundance was determined by factors relating to flow variability, river gradient, in‐stream habitat, and the presence of lakes in the catchment.

ISSN:0028-8330    

DOI:10.1080/00288330.1990.9516434

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor