Effects of dam construction on biodiversity: A review

The chemical dynamics of lakes and streams affect their suitability as aquatic habitats and as water supplies for human needs Because water quality is typically monitored only weekly or monthly, however, the higher-frequency dynamics of stream chemistry have remained largely invisible To illuminate a wider spectrum of water quality dynamics, rainfall and streamflow were sampled in two headwater catchments at Plynlimon, Wales, at 7-h intervals for 1–2 y and weekly for over two decades, and were analyzed for 45 solutes spanning the periodic table from H+ to U Here we show that in streamflow, all 45 of these solutes, including nutrients, trace elements, and toxic metals, exhibit fractal 1/fα scaling on time scales from hours to decades (α = 105 ± 015, mean ± SD) We show that this fractal scaling can arise through dispersion of random chemical inputs distributed across a catchment These 1/f time series are non–self-averaging: monthly, yearly, or decadal averages are approximately as variable, one from the next, as individual measurements taken hours or days apart, defying naive statistical expectations (By contrast, stream discharge itself is nonfractal, and self-averaging on time scales of months and longer) In the solute time series, statistically significant trends arise much more frequently, on all time scales, than one would expect from conventional t statistics However, these same trends are poor predictors of future trends—much poorer than one would expect from their calculated uncertainties Our results illustrate how 1/f time series pose fundamental challenges to trend analysis and change detection in environmental systems

/pdf/universal-fractal-scaling-in-stream-chemistry-and-its-4hfbxojw83.pdf

Universal fractal scaling in stream chemistry and its implications for solute transport and water quality trend detection

Governing the transition to renewable energy: A review of impacts and policy issues in the small hydropower boom

Water and sediment from Faro and Ganzirri lakes were tested for cadmium, mercury, and lead. These heavy metals have been assessed in serum and muscles of Striped Mullet Mugil cephalus. A haemogram was performed to find effects of heavy metals on haematological variables. Student's t-test showed higher Pb levels in sediments of Ganzirri Lake than Faro Lake. Two-way analysis of variance showed higher Cd and Pb concentration in muscles samples of Striped Mullet from Ganzirri Lake than from Faro Lake. Significant differences were found among haematological parameters as well. Mullet from Ganzirri Lake had lower white and red blood cell and trombocyte counts and higher mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration than those from Faro Lake. Our results indicate a significant presence of lead in the environmental produces an accumulation of this metal in fish muscles.Received April 2, 2014; accepted June 16, 2014.

Bioaccumulation of heavy metals in blood and tissue of striped mullet in two Italian lakes.

Land-cover change and habitat loss are widely recognised as the major drivers of biodiversity loss in the world. Land-cover maps derived from satellite imagery provide useful tools for monitoring land-use and land-cover change. KwaZulu-Natal, a populous yet biodiversity-rich province in South Africa, is one of the first provinces to produce a set of three directly comparable land-cover maps (2005, 2008 and 2011). These maps were used to investigate systematic land-cover changes occurring in the province with a focus on biodiversity conservation. The Intensity Analysis framework was used for the analysis as this quantitative hierarchical method addresses shortcomings of other established land-cover change analyses. In only 6 years (2005-2011), a massive 7.6% of the natural habitat of the province was lost to anthropogenic transformation of the landscape. The major drivers of habitat loss were agriculture, timber plantations, the built environment, dams and mines. Categorical swapping formed a significant part of landscape change, including a return from anthropogenic categories to secondary vegetation, which we suggest should be tracked in analyses. Longer-term rates of habitat loss were determined using additional land-cover maps (1994, 2000). An average of 1.2% of the natural landscape has been transformed per annum since 1994. Apart from the direct loss of natural habitat, the anthropogenically transformed land covers all pose additional negative impacts for biodiversity remaining in these or surrounding areas. A target of no more than 50% of habitat loss should be adopted to adequately conserve biodiversity in the province. Our analysis provides the first provincial assessment of the rate of loss of natural habitat and may be used to fulfil incomplete criteria used in the identification of Threatened Terrestrial Ecosystems, and to report on the Convention on Biological Diversity targets on rates of natural habitat loss.

/pdf/systematic-land-cover-change-in-kwazulu-natal-south-africa-38ihnyljgx.pdf

Systematic land-cover change in KwaZulu-Natal, South Africa: Implications for biodiversity.

Impacts of large dams are well-known and quantifiable, while small dams have generally been perceived as benign, both socially and environmentally. The present study quantifies the cumulative impacts of small dams on the water quality (physico-chemistry and invertebrate biotic indices) and quantity (discharge) of downstream rivers in 2 South African regions. The information from 2 South African national databases was used for evaluating the cumulative impacts on water quality and quantity. Physico-chemistry and biological data were obtained from the River Health Programme, and discharge data at stream flow gauges was obtained from the Hydrological Information System. Multivariate analyses were conducted to establish broad patterns for cumulative impacts of small dams across the 2 regions - Western Cape (winter rainfall, temperate, south-western coast) and Mpumalanga (summer rainfall, tropical, eastern coast). Multivariate analyses found that the changes in macroinvertebrate indices and the stream's physico-chemistry were more strongly correlated with the density of small dams in the catchment (as a measure of cumulative impact potential) relative to the storage capacity of large dams. T-tests on the data, not including samples with upstream large dams, indicated that the high density of small dams significantly reduced low flows and increased certain physico-chemistry variables (particularly total dissolved salts) in both the regions, along with associated significant reductions in a macroinvertebrate index (SASS4 average score per taxon). Regional differences were apparent in the results for discharge reductions and the macroinvertebrate index. The results suggest that the cumulative effect of a high number of small dams is impacting the quality and quantity of waters in South African rivers and that these impacts need to be systematically incorporated into the monitoring protocol of the environmental water requirements.

/pdf/ecological-impacts-of-small-dams-on-south-african-rivers-26kydtzwb4.pdf

Ecological impacts of small dams on South African rivers Part 1: drivers of change - water quantity and quality

Water quality monitoring tools that rely on data from stress-response tests with continuous exposure at constant concentrations are not always appropriately protective when stressor exposure in the field is episodic in nature. The present study identifies various approaches that have attempted to account for episodic stressor exposure, describes the development of a toxicological effects database of episodic stressor exposure collated from published scientific literature, and discusses whether any discernible trends are evident when these data are reviewed. The episodic stressor exposure literature indicated that few generalizations can be made regarding associated biological responses. Instead, when attempting to characterize the hazard of a certain episodic pollution event, the following situation-specific information is required: the specific species affected and its age, the specific stressor and its concentration, the number of exposures to the stressor, the duration of exposure to the stressor, and the recovery time after each exposure. The present study identifies four main challenges to the inclusion of episodic toxicity data in environmental water quality management: varying stressor concentration profiles, defining episodic stressor concentration levels, variation resulting from routes of exposure and modes of action, and species-specific responses to episodic stressor exposure. The database, available at http://iwr.ru.ac.za/iwr/download, could be particularly useful for site-specific risk assessments related to episodic exposures.

Review of toxicological effects caused by episodic stressor exposure.

This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments. Keywords: cumulative impacts, reduced low flows, environmental water quality, Ephemeroptera, Trichoptera

https://www.ajol.info/index.php/sajr/article/download/184297/173667

Ecological impacts of small dams on South African rivers Part 2: Biotic response – abundance and composition of macroinvertebrate communities

This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa - the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments.

/pdf/ecological-impacts-of-small-dams-on-south-african-rivers-gom15y37jg.pdf

Ecological impacts of small dams on South African rivers Part 2: Biotic response - abundance and composition of macroinvertebrate communities

Macroinvertebrates were sampled from 15 sites along a dry-land river in northwestern Zimbabwe to assess biotic responses to land use changes along the course of the river. The headwater sites were protected by a riparian corridor of native forest, but this was replaced by intensive subsistence agriculture in the mid-reaches while the lower reaches were located within a protected wildlife area with diverse and wide riparian forests. Canonical correspondence analysis indicated that intensive agricultural activities within the mid-reaches caused severe degradation of the stream physical habitat through increased fine sediment deposition. This coincided with a significant decline in macroinvertebrate richness, diversity, and abundance at the agriculturally impacted mid-reach sites. The presence of wide riparian zones at the lower river sites resulted in significant improvements in stream physical habitat quality, and this was paralleled by significant recovery or reappearance of taxa that had disappeared from the mid-reaches. We suggest that restoration of the riparian vegetation within the mid-reaches of the Nyaodza River would lead to improved physical habitat and biotic health of this dry-land river.

Changes in biota along a dry-land river in northwestern Zimbabwe: declines and improvements in river health related to land use

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