Ecological Status Of Streams Research Articles

Landscape characteristics affecting streams in urbanizing regions of the Delaware River Basin (New Jersey, New York, and Pennsylvania, U.S.)

Widespread and increasing urbanization has resulted in the need to assess, monitor, and understand its effects on stream water quality. Identifying relations between stream ecological condition and urban intensity indicators such as impervious surface provides important, but insufficient information to effectively address planning and management needs in such areas. In this study we investigate those specific landscape metrics which are functionally linked to indicators of stream ecological condition, and in particular, identify those characteristics that exacerbate or mitigate changes in ecological condition over and above impervious surface. The approach used addresses challenges associated with redundancy of landscape metrics, and links landscape pattern and composition to an indicator of stream ecological condition across a broad area of the eastern United States. Macroinvertebrate samples were collected during 2000–2001 from forty-two sites in the Delaware River Basin, and landscape data of high spatial and thematic resolution were obtained from photointerpretation of 1999 imagery. An ordination-derived ‘biotic score’ was positively correlated with assemblage tolerance, and with urban-related chemical characteristics such as chloride concentration and an index of potential pesticide toxicity. Impervious surface explained 56% of the variation in biotic score, but the variation explained increased to as high as 83% with the incorporation of a second land use, cover, or configuration metric at catchment or riparian scales. These include land use class-specific cover metrics such as percent of urban land with tree cover, forest fragmentation metrics such as aggregation index, riparian metrics such as percent tree cover, and metrics related to urban aggregation. Study results indicate that these metrics will be important to monitor in urbanizing areas in addition to impervious surface.

Improving the quantification of land cover pressure on stream ecological status at the riparian scale using High Spatial Resolution Imagery

The aim of this paper is to demonstrate the interest of High Spatial Resolution Imagery (HSRI) and the limits of coarse land cover data such as CORINE Land Cover (CLC), for the accurate characterization of land cover structure along river corridors and of its functional links with freshwater ecological status on a large scale. For this purpose, we compared several spatial indicators built from two land cover maps of the Herault River corridor (southern France): one derived from the CLC database, the other derived from HSRI. The HSRI-derived map was obtained using a supervised object-based classification of multi-source remotely-sensed images (SPOT 5 XS-10 m and aerial photography-0.5 m) and presents an overall accuracy of 70%. The comparison between the two sets of spatial indicators highlights that the HSRI-derived map allows more accuracy in the quantification of land cover pressures near the stream: the spatial structure of the river landscape is finely resolved and the main attributes of riparian vegetation can be quantified in a reliable way. The next challenge will consist in developing an operational methodology using HSRI for large-scale mapping of river corridor land cover, for spatial indicator computation and for the development of related pressure/impact models, in order to improve the prediction of stream ecological status.

Measuring stream macroinvertebrate responses to gradients of vegetation cover: when is enough enough?

Summary1. Management of stream biodiversity is often tightly linked with the restoration and protection of riparian and catchment vegetation. Despite that, there are no established guidelines on how much forest should be retained or replanted in riparian zones and surrounding catchments to maintain or re‐establish instream ecological integrity. In this study, we assess relationships between vegetation cover at multiple spatial scales (reach, segment and catchment) and macroinvertebrate metrics that reflect community structure, ecological condition and biodiversity at 138 Waikato, New Zealand, stream sites sampled in 2006.2. Percentage of catchment vegetation in native forest had stronger relationships with measured diversity and condition metrics than segment or reach scale measures of riparian vegetation. Functional feeding group metrics were weakly associated with upstream catchment vegetation cover.3. Of the macroinvertebrate metrics tested, the RIVPAC O/E and an organic pollution tolerance metric based on species presence–absence (Macroinvertebrate Community Index; MCI) had the strongest relationships with percentage native riparian vegetation, followed by the quantitative MCI and measures of the richness and relative abundance of Ephemeroptera, Plecoptera and Trichoptera faunas. The O/E and MCI indicated that catchments with 80–90% in native forest or scrub (low‐growing trees) were associated with faunas indicative of “clean” water quality.4. Of the biodiversity indices considered Fisher’s α Index of species richness had the strongest relationship with percent native riparian vegetation in the upstream catchment. There are no established thresholds for measuring biodiversity loss in New Zealand streams, but this analysis indicates that on average streams draining catchments with 40–60% upstream native vegetation cover retain 80% of the mean biodiversity present in pristine forest streams.5. This research indicates that riparian management aimed at enhancing macroinvertebrate biodiversity and the ecological condition of streams is likely to be more successful when focused on protecting and/or restoring headwater catchments rather than short stretches of stream.

Influence of groundwater exploitation on the ecological status of streams in a Mediterranean system (Selva Basin, NE Spain)

The ecological status of streams depends on an equilibrium between hydrological processes and biological dynamics. Water discharge is the main requisite for a wealthy riparian habitat. Nevertheless, human practices severely affect water availability through stream water derivation and groundwater withdrawal. In this sense, impacts upon aquifer water storage and its effects on base flow generation have a significant effect on stream biology. Consequently, biological indicators will point out poor conditions resulting from such human impacts. In this paper, the effects of groundwater exploitation on stream discharge and surface water quality are evaluated and compared to biological indicators in a Mediterranean catchment. The stream–aquifer relationship is investigated by considering the hydrological context of each river reach, including human pressures, and the hydraulic head in the contiguous alluvial aquifer, where it exists. These data allow us to differentiate distinct types of reaches that are defined according to a “Stream–Aquifer relationship and chemical Pressure” (SAP) classification, which is used later on to standardize the different hydrochemical and biological features of the sampling points. Stream water and groundwater hydrochemistry are compared to depict the hydraulic behavior of the sampled watercourses during wet and dry periods. Specific elements are used as tracers of groundwater inputs, wastewater influence, or even stagnant conditions during the dry season. This dataset defines a framework to interpret the biological status of each reach based on the Iberian biological monitoring working party indicator (IBMWP). Affinities between hydrological and hydrochemical conditions with biological indicator values allow the causal effects of groundwater exploitation on stream ecology to be defined. The use of multivariate principal component analysis shows that the dataset variance is distributed according to the SAP classification, and that variable grouping is in agreement with the observed hydrological processes and their effects on biological indicator values. This work provides evidence of the importance of groundwater dynamics on biological indicators in a human-modified environment. When using the SAP classification, biological indicators acquire a broader meaning as they reveal the status of biological processes and the causal references. Such information is relevant for water management assessment within the context of the European Water Framework Directive, as it emphasizes the control of groundwater exploitation as a key parameter in the preservation of stream ecological status and the achievement of the objectives of the directive.

Judging a Brook by Its Cover: The Relation between Ecological Condition of a Stream and Urban Land Cover in New England

The US Geological Survey conducted an urban land-use study in the New England Coastal Basins (NECB) area during 2001 to determine how urbanization relates to changes in the ecological condition of streams. Thirty sites were selected that differed in their level of watershed development (low to high). An urban intensity value was calculated for each site from 24 landscape variables. Together, these 30 values reppresented a gradient of urban intensity. Among various biological, chemical, and physical factors surveyed at each site, benthic invertebrate assemblages were sampled from stream riffles and also from multiple habitats along the length of the sampling reach. We use some of the NECB data to derive a four-variable urbanintensity index (NECB-UII), where each variable represents a distinct component of urbanization: increasing human presence, expanding infrastructure, landscape development, and riparian vegetation loss. Using the NECB-UII as a characterization of urbanization, we describe how landscape fragmentation occurs with urbanization and how changes in the invertebrate assemblages, represented by metrics of ecological condition, are related to urbanization. Metrics with a strong linear response included EPT taxa richness, percentage richness of non-insect taxa, and pollution-tolerance values. Additionally, we describe how these relations can help in estimating the expected condition of a stream for its level of urbanization, thereby establishing a baseline for evaluating possible affects from specific point-source stressors.

A Bayesian hierarchical trend analysis finds strong evidence for large‐scale temporal declines in stream ecological condition around Melbourne, Australia

Knowledge of temporal change in ecological condition is important for the understanding and management of ecosystems. However, analyses of trends in biological condition have been rare, as there are usually too few data points at any single site to use many trend analysis techniques. We used a Bayesian hierarchical model to analyse temporal trends in stream ecological condition (as measured by the invertebrate‐based index SIGNAL) across Melbourne, Australia. The Bayesian hierarchical approach assumes dependency amongst the sampling sites. Results for each site “borrow strength” from the other data because model parameter values are assumed to be drawn from a larger common distribution. This leads to robust inference despite the few data that exist at each site. Utilising the flexibility of the Bayesian approach, we also modelled change over time as a function of catchment urbanisation, allowed for potential temporal and spatial autocorrelation of the data and trend estimates, and used prior information to improve the estimate of data uncertainty. We found strong evidence of a widespread decline in SIGNAL scores for edge habitats (areas of little or no flow). The rate of decline was positively associated with catchment urbanisation. There was no evidence of such declines for riffle habitats (areas with rapid and turbulent flow). Melbourne has experienced a decline in rainfall, indicative of either drought and/or longer‐term climate change. The results are consistent with the expected coupled effects of these rainfall changes and increasing urbanisation, but more research is needed to isolate a causal mechanism. More immediately, however, the Bayesian hierarchical approach has allowed us to identify a pattern in a biological monitoring data set that might otherwise have gone un‐noticed, and to demonstrate a large‐scale temporal decline in biological condition.

Relationship of stream ecological conditions to simulated hydraulic metrics across a gradient of basin urbanization

The relationships among urbanization, stream hydraulics, and aquatic biology were investigated across a gradient of urbanization in 30 small basins in eastern Wisconsin, USA. Simulation of hydraulic metrics with 1-dimensional unsteady flow models was an effective means for mechanistically coupling the effects of urbanization with stream ecological conditions (i.e., algae, invertebrates, and fish). Urbanization, characterized by household, road, and urban land density, was positively correlated with the lowest shear stress for 2 adjacent transects in a reach for the low-flow summer (p < 0.001) and autumn (p < 0.01) periods. Urbanization also was positively correlated with Reynolds number and % exposed stream bed during months with moderate to low flows. Our study demonstrated the value of temporally and spatially explicit hydraulic models for providing mechanistic insight into the relationships between hydraulic variables and biological responses. For example, the positive correlation between filter-feeding invertebrate richness and minimum 2-transect shear stress observed in our study is consistent with a higher concentration of water-column particulates available for filtration. The strength of correlations between hydraulic and biological metrics is related to the time period (annual, seasonal, or monthly) considered. The hydraulic modeling approach, whether based on hourly or daily flow data, allowed documentation of the effects of a spatially variable response within a reach, and the results suggest that stream response to urbanization varies with hydraulic habitat type.

Evaluation of river basin restoration options by the application of the Water Framework Directive Explorer in the Zwalm River basin (Flanders, Belgium)

AbstractWater managers and researchers strive towards the same objective: the improvement of the quality status of water bodies. However, there is still a gap between the results of academic studies on water systems and the information currently used in water management. The Water Framework Directive (WFD)‐Explorer, a modular toolbox which supports integrated water management in a river basin, attempts to bridge this gap. The toolbox analyses the impact of different restoration measures on river ecology based on expert rules embedded in this simulation environment. The strengths and weaknesses of the toolbox have been tested on the Zwalm River basin in Flanders, Belgium. The ecological status of streams in the basin spans the whole range of nearly pristine headwaters to severely impacted river stretches further downstream. Considering the key bottlenecks in the Zwalm basin and the user‐driven ecological status objectives, several water quality and physical habitat restoration options have been proposed to meet the European Water Framework Directive goals. The positive impact of restoration measures on the ecological quality ratio (EQR) for macroinvertebrates appeared to be the highest for measures affecting the nutrient inflows and thus chemical water body characteristics. However, the spatial scale on which the WFD‐Explorer modelled the impact of physical habitat restoration may have been too coarse to generate reliable results concerning such restoration measures. Hence, the combination of the WFD‐Explorer results with those of more detailed studies on physical habitat restoration impacts might be a promising approach to reliably support decision‐making implementation of the WFD. Copyright © 2008 John Wiley &amp; Sons, Ltd.

An invitation to apply national survey data to ecological research

Previous article No AccessArticlesAn invitation to apply national survey data to ecological researchSteven G. Paulsen, Charles P. Hawkins, John Van Sickle, Lester L. Yuan, and Susan M. HoldsworthSteven G. Paulsen1 Office of Research and Development, US Environmental Protection Agency, 200 SW 35th St., Corvallis, Oregon 97330 USA5E-mail addresses: [email protected] Search for more articles by this author , Charles P. Hawkins2 Western Center for Monitoring and Assessment of Freshwater Ecosystems, Department of Watershed Sciences and the Ecology Center, Utah State University, Logan, Utah 84322-5210 USA6 [email protected] Search for more articles by this author , John Van Sickle1 Office of Research and Development, US Environmental Protection Agency, 200 SW 35th St., Corvallis, Oregon 97330 USA7 [email protected] Search for more articles by this author , Lester L. Yuan3 Office of Research and Development, US Environmental Protection Agency, 1200 Pennsylvania Ave, NW, 8623P, Washington, DC 20460 USA8 [email protected] Search for more articles by this author , and Susan M. Holdsworth4 Office of Water, US Environmental Protection Agency, Ariel Rios Building, 1200 Pennsylvania Ave., NW, 4503T, Washington, DC 20460 USA9 [email protected] Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 27, Number 4December 2008 Article DOIhttps://doi.org/10.1899/08-123.1 Views: 20Total views on this site Citations: 4Citations are reported from Crossref HistoryReceived September 3, 2008Accepted September 3, 2008 Journal History This article was published in the Journal of the North American Benthological Society (1986-2011), which is continued by Freshwater Science (2012-present). © 2008 by The North American Benthological SocietyPDF download Crossref reports the following articles citing this article:Luis Mauricio Bini, Victor Lemes Landeiro, André Andrian Padial, Tadeu Siqueira, Jani Heino Nutrient enrichment is related to two facets of beta diversity for stream invertebrates across the United States, Ecology 95, no.66 (Jun 2014): 1569–1578.https://doi.org/10.1890/13-0656.1W. G. McDowell, A. J. Benson, J. E. Byers Climate controls the distribution of a widespread invasive species: implications for future range expansion, Freshwater Biology 59, no.44 (Feb 2014): 847–857.https://doi.org/10.1111/fwb.12308John M. Faustini, Philip R. Kaufmann, Alan T. Herlihy Downstream variation in bankfull width of wadeable streams across the conterminous United States, Geomorphology 108, no.3-43-4 (Jul 2009): 292–311.https://doi.org/10.1016/j.geomorph.2009.02.005Charles P. Hawkins,* Steven G. Paulsen,† John Van Sickle,‡ and Lester L. Yuan§ Regional assessments of stream ecological condition: scientific challenges associated with the USA’s national Wadeable Stream Assessment, Journal of the North American Benthological Society 27, no.44 (Jul 2015): 805–807.https://doi.org/10.1899/08-122.1

Regional assessments of stream ecological condition: scientific challenges associated with the USA’s national Wadeable Stream Assessment

Regional assessments describe the status of an entire ecological resource within a region of interest. Considering the global scope of landscape, atmospheric, and waterway alterations, such assessments are critically needed to guide environmental policies that can ensure sustainable management of the planet’s natural resources (Millenium Ecosystem Assessment 2005, Carpenter et al. 2006). Objective regional assessments depend on the application of sound and credible science including sampling designs that allow accurate extrapolation to the whole resource population and indicators that are quantitative, ecologically interpretable, and regionally comparable. In 2006, in response to increasing requests for data describing the quality of surface waters and other ecosystems in the US (e.g., USGAO 1981, 1988, H. John Heinz Center for Science, Economics and the Environment 2002, 2008), the US Environmental Protection Agency and its state and tribal collaborators published the first nationwide assessment of stream ecosystems in the US (USEPA 2006). Producing that assessment required that research teams tasked with designing and implementing the assessment address several technical challenges. Some of those challenges were overcome, others remain in need of additional attention, and some new challenges emerged after the assessment. In this special issue of J-NABS, we have compiled a series of papers that describe some of the major scientific challenges that were encountered during the national Wadeable Streams Assessment (WSA) and some of the lessons learned subsequent to the assessment. Our goal in producing this series was to use the WSA as a case study to illustrate the variety of scientific challenges that can arise when planning and implementing regional assessments, describe how those challenges were addressed for the WSA, describe some important spin-offs that emerged as a consequence of the WSA, and identify remaining knowledge or data gaps that will require attention in future regional assessments. We hope these papers will stimulate thinking about how to improve future assessments in the US and elsewhere. The series consists of 4 sets of papers: 1) policy and overview, 2) WSA-specific case studies, 3) extensions that build on or augment initial WSA results, and 4) an invitation to other researchers to use the WSA data to test other ideas regarding the structure and function of stream ecosystems. The series opens with a paper by Shapiro et al. (2008) that describes the policy background that led to the WSA. Paulsen et al. (2008) then provide an overview of the major findings that emerged from the WSA. The 2 set of papers includes papers that cover issues of survey design and indicator development and application. Olsen and Peck (2008) describe 1 E-mail addresses: chuck.hawkins@usu.edu 2 paulsen.steve@epa.gov 3 vansickle.john@epa.gov 4 yuan.lester@epa.gov

Linking multimetric and multivariate approaches to assess the ecological condition of streams

Few attempts have been made to combine multimetric and multivariate analyses for bioassessment despite recognition that an integrated method could yield powerful tools for bioassessment. An approach is described that integrates eight macroinvertebrate community metrics into a Principal Components Analysis to develop a Multivariate Condition Score (MCS) from a calibration dataset of 511 samples. The MCS is compared to an Index of Biotic Integrity (IBI) derived using the same metrics based on the ratio to the reference site mean. Both approaches were highly correlated although the MCS appeared to offer greater potential for discriminating a wider range of impaired conditions. Both the MCS and IBI displayed low temporal variability within reference sites, and were able to distinguish between reference conditions and low levels of catchment modification and local habitat degradation, although neither discriminated among three levels of low impact. Pseudosamples developed to test the response of the metric aggregation approaches to organic enrichment, urban, mining, pastoral and logging stressor scenarios ranked pressures in the same order, but the MCS provided a lower score for the urban scenario and a higher score for the pastoral scenario. The MCS was calculated for an independent test dataset of urban and reference sites, and yielded similar results to the IBI. Although both methods performed comparably, the MCS approach may have some advantages because it removes the subjectivity of assigning thresholds for scoring biological condition, and it appears to discriminate a wider range of degraded conditions.

Rehabilitating Agricultural Streams in Australia with Wood: A Review

Worldwide, the ecological condition of streams and rivers has been impaired by agricultural practices such as broadscale modification of catchments, high nutrient and sediment inputs, loss of riparian vegetation, and altered hydrology. Typical responses include channel incision, excessive sedimentation, declining water quality, and loss of in-stream habitat complexity and biodiversity. We review these impacts, focusing on the potential benefits and limitations of wood reintroduction as a transitional rehabilitation technique in these agricultural landscapes using Australian examples. In streams, wood plays key roles in shaping velocity and sedimentation profiles, forming pools, and strengthening banks. In the simplified channels typical of many agricultural streams, wood provides habitat for fauna, substrate for biofilms, and refuge from predators and flow extremes, and enhances in-stream diversity of fish and macroinvertebrates.Most previous restoration studies involving wood reintroduction have been in forested landscapes, but some results might be extrapolated to agricultural streams. In these studies, wood enhanced diversity of fish and macroinvertebrates, increased storage of organic material and sediment, and improved bed and bank stability. Failure to meet restoration objectives appeared most likely where channel incision was severe and in highly degraded environments. Methods for wood reintroduction have logistical advantages over many other restoration techniques, being relatively low cost and low maintenance. Wood reintroduction is a viable transitional restoration technique for agricultural landscapes likely to rapidly improve stream condition if sources of colonists are viable and water quality is suitable.

Parametric distance weighting of landscape influence on streams

We present a parametric model for estimating the areas within watersheds whose land use best predicts indicators of stream ecological condition. We regress a stream response variable on the distance-weighted proportion of watershed area that has a specific land use, such as agriculture. Distance weighting functions model the declining influence of landscape elements as a function of their flowpath distances, first to the stream channel (to-stream distance), and then down the channel to the location at which stream condition was sampled (in-stream distance). Model parameters specify different distance scales over which to-stream and in-stream influences decline. As an example, we predict an index of biotic integrity (IBI) for the fish communities in 50 small streams of the Willamette Basin of Oregon, USA, from distance-weighted proportions of agricultural or urban land use in their watersheds. The weighting functions of best-fitting models (R 2 = 0.57) represent landscape influence on IBI as extending upstream tens of kilometers along the stream channel network, while declining nearly to zero beyond a distance of 30 m from the channel. Our example shows how parametric distance weighting can identify the distance scales, and hence the approximate areas within watersheds, for which land use is most strongly associated with a stream response variable. In addition, distance-weighting parameters offer a simple and direct language for comparing the scales of landscape influence on streams across different land uses and stream ecosystem components.

Epilithic diatoms as indicators of water quality and ecological status of streams of Sudety Mountains (South-Western Poland)

Epilithic diatom communities in high-altitude streams in the Polish part of Sudety Mountains were studied in the years 2004-2006 to assess water quality and ecological status. In the Polish river typology, these water bodies have been separated as the type 3: the Sudety stream characterized by a small catchment area (< 100 km 2 ), V- or U-shaped valley, high velocity of flow, significant channel slope and a bed composed of boulders, stones and cobbles. The stream sections under study are located in Karkonosze Mountains and in Snieznik Massif and have been chosen following the European Union's recommendations for reference sites. The Karkonosze streams possess slightly acidic or neutral waters, with very poor electrolyte content, low total hardness and low total P content. Streams in Snieznik Massif have alkaline waters, with poor or medium electrolyte content, higher total hardness and higher total P content. Altogether 184 diatom taxa were determined. Species diversity ranged from poor (8-9 taxa) to moderately rich (82 taxa). The most abundant were Diatoma mesodon, Eunotia exigua, Achnanthidium minutissimum, Fragilaria capucina var. rumpens, Encvonema minutum, Fragilariforma virescens, Gomphonema gracile and Tabellaria flocculosa. Three diatom indices were applied in order to assess water quality: the Trophic Index (TI), the Saprobic Index (SI) and the Index of Pollution Sensibility (IPS). The TI values varied from 0.53 to 1.83 and in majority of the streams indicated ultraoligotrophic or oligotrophic waters. The SI values changed from 1.09 to 1.55 and indicated none (oligosaprobic) or slight (oligo-β-mesosaprobic) organic pollution. The IPS values were usually not lower than 17.7 and indicated waters of low trophy and unpolluted or imperceptibly polluted. Most of the streams studied may serve as reference sites for the Polish type 3 of running waters, i.e. the stream of Sudety Mts.

The use of large wood in stream restoration: experiences from 50 projects in Germany and Austria

Summary 1Wood is increasingly used in restoration projects to improve the hydromorphological and ecological status of streams and rivers. However, despite their growing importance, only a few of these projects are described in the open literature. To aid practitioners, we conducted a postal mail survey to summarize the experiences gained in central Europe and compile data on 50 projects. 2Our results indicated the potential for improvement from an ecological point of view, as the number and total wood volume, and the median volume of single wood structures placed in the streams per project, were low compared with the potential natural state. Moreover, many wood structures were placed nearly parallel to the water flow, reducing their beneficial effect on stream hydraulics and morphology. 3Restoration success has been monitored in only 58% of the projects. General conclusions drawn include the following. (i) The potential effects of wood placement must be evaluated within a watershed and reach-scale context. (ii) Wood measures are most successful if they mimic natural wood. (iii) Effects of wood structures on stream morphology are strongly dependent on conditions such as stream size and hydrology. (iv) Wood placement has positive effects on several fish species. (v) Most projects revealed a rapid improvement of the hydromorphological status. 4Most of the wood structures have been fixed, called ‘hard engineering’. However, soft engineering methods (use of non-fixed wood structures) are known to result in more natural channel features for individual stream types, sizes and sites, and are significantly more cost-effective. 5Synthesis and applications. Large wood has been used successfully in several projects in central Europe, predominantly to increase the general structural complexity using fixed wood structures. Our results recommend the use of less costly soft engineering techniques (non-fixed wood structures), higher amounts of wood, larger wood structures and improved monitoring programmes for future restoration projects comparable with those in this study. We recommend the use of ‘passive restoration’ methods (restoring the process of wood recruitment on large scales) rather than ‘active restoration’ (placement of wood structures on a reach scale), as passive restoration avoids the risk of non-natural amounts or diversity of wood loading developing within streams. Local, active placement of wood structures must be considered as an interim measure until passive restoration methods have increased recruitment sufficiently.

Scenarios for redesigning an urban drainage system to reduce runoff frequency and restore stream ecological condition

Monitoring the hydrochemical efficiency of urban stormwater treatment devices is not straightforward as the traditional, automated, In urban areas, efficient drainage of impervious surfaces means that polluted stormwater is frequently delivered to streams. Commonly, catchment urbanization can increase runoff frequency by a factor of 10 or more, as the effective imperviousness - the proportion of the catchment that consists of impervious surfaces drained to streams - is increased. This causes a decline in stream health. To decrease runoff frequency, effective imperviousness must be reduced. This requires urban drainage systems to be redesigned, using techniques such as infiltration and rainwater harvesting, so that stormwater from small rain events is not piped directly to streams but instead is infiltrated, reused or retained. We have developed scenarios that explore alternative urban drainage systems appropriate for a small partly urbanised catchment in Melbourne’s east. These scenarios incorporate, biofiltration basins, swales and dual purpose rainwater tanks that supply water for householders. Our results suggested that sufficient reductions in effective imperviousness and runoff frequency are possible to achieve improvements in stream health.

Evaluation of the Trophic Diatom Index for assessing water quality in River Gharasou, western Iran

Water quality, diatom species composition and biomass estimates were performed in the Gharasou River in western Iran. Five sites along the River Gharasou were sampled every month from April to September 2005. Physical and chemical factors (pH, NO3–N, PO4–P, dissolved oxygen, total suspend solids, total dissolved solids, conductivity, turbidity, chemical oxygen demand and biological oxygen demand) were measured along with biological properties of the periphyton including biomass, ash-free dry mass, chlorophyll-a concentration and the taxonomic composition diatom assemblages. Information from the diatom assemblage was used to calculate the Trophic Diatom Index and biovolume. The TDI was significantly correlated with measures of human disturbance at the sites (e.g. PO4–P, NO3–N and dissolved oxygen) as well as to biomass measures (chlorophyll a, ash-free dry mass and biovolume). The sensitivity of the TDI and its component metrics to environmental stressors supports the use of this index for monitoring ecological conditions in streams in Iran and to aid diagnosis of the cause of their impairment.

The impact of urban patterns on aquatic ecosystems: An empirical analysis in Puget lowland sub-basins

Landscape change associated with urbanization poses major challenges to aquatic ecosystems. Extensive studies have shown that the composition of land cover within a watershed can account for much of the variability in water quality and stream ecological conditions. While several studies have addressed the relationship between watershed urbanization and biotic integrity in streams, few have directly addressed the question of how urban patterns influence ecological conditions. These studies typically correlate changes in ecological conditions with simple aggregated measures of urbanization (e.g., human population density or percent impervious surface). We develop an empirical study of the impact of urban development patterns on stream ecological conditions in 42 sub-basins in the Puget Sound lowland region on a gradient of urbanization. We hypothesize that ecological conditions in urbanizing landscapes are influenced through biophysical changes by four urban pattern variables: land use intensity, land cover composition, landscape configuration, and connectivity of the impervious area. Using community measures of benthic macroinvertebrates as indicators of in-stream biotic integrity we examined the relationships between urban development patterns and ecological conditions in these basins. Significant statistical relationships were found between landscape patterns—both amount and configuration of impervious area and forest land—and biotic integrity of streams suggesting that patterns of urban development matter to aquatic ecosystems.

Beyond Masses and Blooms: The Indicative Value of Oligochaetes

The European Water Framework Directive (WFD) defines a framework for assessing water bodies in Europe in the future. The conditions in the Directive impose a strong demand for “new” assessment systems. The AQEM project developed an assessment system for European streams using macroinvertebrates. Almost 900 samples were taken in about 400 streams covering 29 stream types distributed over eight countries. The role of the Oligochaeta within this European database was analysed. Almost half a million specimens of oligochaetes were collected in 772 samples. Eight families, 41 genera and 69 species were recorded, although identification emphasised the families Tubificidae and Naididae. Three countries identified oligochaetes to species level, most others restricted their identifications to easy identifiable taxa. Numbers of specimens, species, genera and families differed strongly between the countries due to method, although standardised, and taxonomic knowledge. About 50% of all collected oligochaete taxa had assigned biological and ecological indicator values for metric calculation in the AQEM assessment system. A further refinement of this indication list as well as increased coverage of oligochaete taxa was advised. Weighted averaging was used to evaluate the relation between oligochaete distribution and ecological quality class. It was concluded that when higher taxonomic levels are used in assessment, the quality evaluation results become biased. Furthermore, oligochaetes can tell us much more about the ecological status of streams than is commonly assumed. Differences in ecological optima among Limnodrilus udekemianus, Ilyodrilus templetoni, Aulodrilus pluriseta, Nais communis, and Spirosperma ferox are shown.

Linking catchment characteristics and water chemistry with the ecological status of Irish rivers

Requirements of the EU Water Framework Directive for the introduction of ecological quality objectives for surface waters and the stipulation that all surface waters in the EU must be of ‘good’ ecological status by 2015 necessitate a quantitative understanding of the linkages among catchment attributes, water chemistry and the ecological status of aquatic ecosystems. Analysis of lotic ecological status, as indicated by an established biotic index based primarily on benthic macroinvertebrate community structure, of 797 hydrologically independent river sites located throughout Ireland showed highly significant inverse associations between the ecological status of rivers and measures of catchment urbanisation and agricultural intensity, densities of humans and cattle and chemical indicators of water quality. Stepwise logistic regression suggested that urbanisation, arable farming and extent of pasturelands are the principal factors impacting on the ecological status of streams and rivers in Ireland and that the likelihood of a river site complying with the demands of the EU Water Framework Directive, and be of ‘good’ ecological status, can be predicted with reasonable accuracy using simple models that utilise either widely available landcover data or chemical monitoring data. Non-linear landcover and chemical ‘thresholds’ derived from these models provide a useful tool in the management of risk in catchments, and suggest strongly that more careful planning of land use in Ireland is essential in order to restore and maintain water quality as required by the Directive.