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Water Abstraction (water + abstraction)

Distribution by Scientific Domains

Life Sciences	90%

Selected Abstracts

Hydrological disturbance benefits a native fish at the expense of an exotic fish

JOURNAL OF APPLIED ECOLOGY, Issue 5 2006
F. LEPRIEUR
Summary 1Some native fish in New Zealand do not coexist with introduced salmonids. Previous studies of disjunct distributions of exotic brown trout Salmo trutta and native galaxiids demonstrated native extirpation except where major waterfalls prevented upstream migration of trout. In the Manuherikia River system, we predicted that water abstraction might be a further factor controlling the spatial distribution of both the invader and a native fish. 2We applied multiple discriminant function analyses to test for differences in environmental conditions (catchment and instream scales) at sites with roundhead galaxias Galaxias anomalus and brown trout in sympatry and allopatry. We then used a supervised artificial neural network (ANN) to predict the presence,absence of G. anomalus and brown trout (135 sites). The quantification of contributions of environmental variables to ANN models allowed us to identify factors controlling their spatial distribution. 3Brown trout can reach most locations in the Manuherikia catchment, and often occur upstream of G. anomalus. Their largely disjunct distributions in this river are mediated by water abstraction for irrigation, together with pool habitat availability and valley slope. Trout are more susceptible than the native fish to stresses associated with low flows, and seem to be prevented from eliminating galaxiid populations from sites in low gradient streams where there is a high level of water abstraction. 4Synthesis and applications. In contrast to many reports in the literature, our results show that hydrological disturbance associated with human activities benefits a native fish at the expense of an exotic in the Manuherikia River, New Zealand. Water abstraction is also known to have negative impacts on native galaxiids, therefore we recommend restoring natural low flows to maintain sustainable habitats for native galaxiids, implementing artificial barriers in selected tributaries to limit trout predation on native fish, and removing trout upstream. [source]

Is structure or function a better measure of the effects of water abstraction on ecosystem integrity?

FRESHWATER BIOLOGY, Issue 10 2009
RUSSELL G. DEATH
Summary 1. Assessments of flow abstractions in streams often focus on changes to biological communities and in-stream physical characteristics, with little consideration for changes in ecosystem functioning. It is unclear whether functional indicators of ecosystem health may be useful for assessing the impacts of reduced discharge on small streams. 2. We used weirs and diversions to reduce stream discharge by over 89% in three small New Zealand streams (11,84 L s,1), ranging in water quality from pristine to moderately impaired. 3. We used both structural (benthic invertebrates) and functional (drifting invertebrates, leaf breakdown, coarse particulate organic matter (CPOM) retention and primary productivity) measures of ecosystem integrity to compare responses to water abstraction in before-after, control-impact designed experiments during summer 2005. 4. At the pristine site, the density of invertebrates, taxon richness, Macroinvertebrate Community Index (MCI), Quantitative MCI, percentage of Ephemeroptera, Plecoptera and Trichoptera individuals and percentage of filter-feeders decreased in response to reduced flows. Only taxon richness decreased at the mildly impaired stream, and reduced discharge had no effect on the invertebrate community at the stream with the lowest water quality. 5. We found that reduced discharge had little influence on the breakdown rate of willow leaves in mesh bags over 1 month. Primary productivity was also relatively insensitive to water abstraction. However, CPOM retention increased with decreased flows. Drift propensity of invertebrates increased at two sites but only within the first few days after flow reduction. 6. Structural measures of ecosystem integrity suggested that the impacts of water abstraction differed among streams of varying water quality, probably because of differences in the sensitivity of invertebrate assemblages in the three streams. In contrast, the three functional measures tested were generally less sensitive to water abstraction impacts, although understanding how stream ecosystems respond to water abstraction clearly requires that both are considered. [source]

Isotope Methods for Management of Shared Aquifers in Northern Africa

GROUND WATER, Issue 5 2005
Bill Wallin
Access to fresh water is one of the major issues of northern and sub-Saharan Africa. The majority of the fresh water used for drinking and irrigation is obtained from large ground water basins where there is minor contemporary recharge and the aquifers cross national borders. These aquifers include the Nubian Aquifer System shared by Chad, Egypt, Libya, and Sudan; the Iullemeden Aquifer System, extending over Niger, Nigeria, Mali, Benin, and Algeria; and the Northwest Sahara Aquifer System shared by Algeria, Libya, and Tunisia. These resources are subject to increased exploitation and may be severely stressed if not managed properly as witnessed already by declining water levels. In order to make appropriate decisions for the sustainable management of these shared water resources, planners and managers in different countries need an improved knowledge base of hydrological information. Three technical cooperation projects related to aquifer systems will be implemented by the International Atomic Energy Agency, in collaboration with the United Nations Educational, Scientific and Cultural Organization and United Nations Development Programme/Global Environmental Facility. These projects focus on isotope hydrology studies to better quantify ground water recharge and dynamics. The multiple isotope approach combining commonly used isotopes 18O and 2H together with more recently developed techniques (chlorofluorocarbons, 36Cl, noble gases) will be applied to improve the conceptual model to study stratification and ground water flows. Moreover, the isotopes will be an important indicator of changes in the aquifer due to water abstraction, and therefore they will assist in the effort to establish a sustainable ground water management. [source]

Hydrological disturbance benefits a native fish at the expense of an exotic fish

Surface water balance to evaluate the hydrological impacts of small instream diversions and application to the Russian River basin, California, USA

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2009
Matthew J. Deitch
1.Small streams are increasingly under pressure to meet water needs associated with expanding human development, but the hydrologic and ecological effects are not commonly described in scientific literature. 2.To evaluate the potential effects that surface water abstraction can have on flow regime, scientists and resource managers require tools that compare abstraction to stream flow at ecologically relevant time scales. 3.The classic water balance model was adapted to evaluate how small instream diversions can affect catchment stream-flow; the adapted model maintains the basic mass balance concept, but limits the parameters and considers surface water data at an appropriate timescale. 4.This surface water balance was applied to 20 Russian River tributaries in north-central California to evaluate how recognized diversions can affect stream flow throughout the region. 5.The model indicates that existing diversions have little capacity to influence peak or base flows during the rainy winter season, but may reduce stream flow during spring by 20% in one-third of all the study streams; and have the potential to accelerate summer intermittence in 80% of the streams included in this study. 6.The surface water balance model may be especially useful for guiding river restoration from a hydrologic perspective: it can distinguish among streams with high diversion regimes that may require more than just physical channel restoration to provide ecological benefits, and can illustrate the extent to which changing the diversion parameters of particular water users can affect the persistence of a natural flow regime. 7.As applied to Russian River tributaries, the surface water balances suggest that reducing demand for stream flow in summer may be as important as physical channel restoration to restoring anadromous salmonids in this region. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Basking site and water depth selection by gharial Gavialis gangeticus Gmelin 1789 (Crocodylia, Reptilia) in National Chambal Sanctuary, India and its implication for river conservation

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009
Syed Ainul Hussain
Abstract 1.The species diversity of inland waters is among the most threatened of all ecosystems and in many parts of the world it is in continuing and accelerating decline. Such decline could be restrained by acknowledging the scope of target species, so that all relevant stages in their life cycle are considered. 2.The gharial Gavialis gangeticus is a prominent riverine species of the Indus, Ganges, Brahmaputra and Mahanadi river systems that is becoming increasingly rare due to reduction in water flow and available nesting beaches, modification of river morphology and increased mortality in fishing nets. Despite these threats, scientific information on habitat selection by gharial is still inadequate, which hinders conservation measures. 3.This paper presents the population status, basking site selection and water depth preferences of different size-classes of gharial based on a study conducted in the National Chambal Sanctuary, India. 4.Between 1992 and 2007 a 40% decline in the gharial population was observed in the National Chambal Sanctuary. The decline was prominent in the recruitment class (<120,cm), which primarily comes from the nests laid in the wild, and also in sub-adults (>180 to 270,cm) comprising both wild and reintroduced gharial. 5.Along the Chambal River, gharial preferred sandy parts of the river banks and sand bars for basking and showed less preference for rocky river banks and rocky outcrops. Clay river banks were least preferred. 6.Juvenile gharials <120,cm and 120,180,cm preferred water depths 1,3,m and 2,3,m, respectively. Gharial >180,cm (including sub-adults and adults) preferred water depths >4,m. 7.Increasing demands for sand for development activities, and water abstraction for irrigation and energy generation coupled with mortality in fishing nets, are likely to affect gharial and other aquatic species, and steps need to be taken to maintain the minimum river flow necessary to sustain ecosystem processes. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Habitat selection of freshwater-dependent cetaceans and the potential effects of declining freshwater flows and sea-level rise in waterways of the Sundarbans mangrove forest, Bangladesh

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009
B.D. Smith
Abstract 1.Generalized additive models of sighting data for cetaceans collected during two surveys of waterways in the Sundarbans mangrove forest of Bangladesh indicated that Ganges River dolphin Platanista gangetica gangetica distribution was conditionally dependent (P<0.05) on low salinity, high turbidity, and moderate depth during both low and high freshwater flow; and Irrawaddy dolphin Orcaella brevirostris distribution was conditionally dependent (P<0.05) on low salinity during high freshwater flow, high and moderate depths during low and high freshwater flow, respectively; low and high-low extremes of turbidity during low and high freshwater flow, respectively; and high temperature and increasing numbers of large,small channel confluences during low freshwater flow. 2.According to sighting data collected over a 3-year period by the captains of three nature tourism vessels, there were significant differences between the actual and expected frequencies of Ganges River dolphin sightings and individuals according to various channel types (chi-square=64.22, P<0.0001 and chi-square=134.14, P<0.0001, respectively, df=6) and of Irrawaddy dolphin sightings and individuals (chi-square=15.28, P=0.0182, and chi-square=29.42, P<0.0001, respectively, df=6), with shared preferences for wide sinuous channels with at least two small confluences or one large confluence. 3.The dependency exhibited by both species for environmental characteristics associated with abundant freshwater flow, including low salinity and the availability of confluences, make them particularly vulnerable to habitat loss due to upstream water abstraction and sea-level rise. 4.Although the results of this study may not affect plans for construction in India of large-scale, inter-basin water transfer projects that will result in further declines in freshwater flows, or decisions within the international community about CO2 emissions affecting global sea levels, they can be used to prioritize locations where protective measures could be employed to benefit the long-term conservation of both species. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Ostracoda (Crustacea) from the Turkish Ramsar site of Lake Ku, (Manyas Gölü)

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2001
Selçuk Alt, nsaçl
Abstract 1.,Lake Ku, (Manyas Gölü), an important bird conservation area, was sampled in the summer, autumn, winter and spring of 1997, and the seasonal and spatial distributions of ostracods were investigated. Many of the taxa collected are useful indicator species for monitoring conditions within lake basins. 2.,The findings suggest that the L. Ku, ecosystem is already substantially degraded. Pollution, coupled with extensive water abstraction for irrigation, have damaged the value of the lake, both commercially (as an inland waters fishery), and as an important site for wetland bird conservation. 3.,This work shows that ostracod faunal analysis has value in the study of such sites, particularly where more formal physical, chemical and biological monitoring methods are inappropriate or unavailable. Copyright © 2001 John Wiley & Sons, Ltd. [source]

A comparison of current and historical fish assemblages in a Caribbean island estuary: conservation value of historical data

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2008
K. L. Smith
Abstract 1.Historical data are often one of the only resources available for documenting and assessing causes of environmental change, particularly in developing regions where funding for ecological studies is limited. In this paper, previously unpublished data from a year-long study (1977) of the fish community of the Espiritu Santo estuary are presented. This dataset is among the oldest and most extensive surveys of a Caribbean island estuarine fish community. 2.A comparison of these historical data with data collected in June and July 2004 using identical sampling methods allowed description of potential long-term changes in the fish community, identification of vulnerable species, and assessment of potential drivers of change. 3.Results strongly suggest a decline in species richness and abundance in the Espiritu Santo estuarine fish community, with greater declines in freshwater-tolerant than marine or euryhaline species. Declines in freshwater inflow to the estuary, due to large-scale upstream water abstractions for municipal use, have increased since the initial 1977 survey. 4.This is the first study to examine long-term change in the fish community of a tropical island estuary. Additional research and conservation efforts are needed to understand mechanisms of change and to protect Caribbean island estuarine fish communities. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Floodplains of a regulated southern alpine river (Brenno, Switzerland): ecological assessment and conservation options

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2002
M. Brunke
Abstract 1.The fifth-order southern alpine Brenno River and its floodplains are severely impaired by embankments, water abstractions and the construction of dams for hydropower generation. The river's annual mean discharge is reduced to 27% of the natural flow and the number of small (50,100 m3 s,1) and medium-sized (101,150 m3 s,1) floods is reduced significantly. 2.Lateral hydrological connectivity has decreased strongly as a result of the flow regulation, whereas the significance of vertical connectivity has increased. The remnants of the middle and lower floodplains still contain springbrooks, ponds, and intermittently connected channels, which are all sustained by emerging groundwater. 3.Aquatic floodplain habitats can be classified partially by faunal composition. The lotic/lentic gradient appears to be a dominant compound factor structuring invertebrate assemblages when considering all aquatic habitats. The exfiltration of groundwater in conjunction with a reduced lateral connectivity enables the occurrence of many stenotopic species. 4.A comparison of present floodplains with those shown on historical maps shows that the fluvial landscape has changed markedly. The proportions of functional floodplain units characterized by autogenic succession and trends to late successional stages (i.e. senescence) have increased. 5.Floodplains of the Brenno river are still considered to represent important ecological areas and they are protected by law. Whilst the legislative protection of floodplains is the basis for conservation, this does not include the restoration of driving hydrological processes. An annual release of small- and medium-sized floods could generate a diversity of disturbances, thereby promoting rejuvenation and counteracting senescence. 6.Alternative conservation options that circumvent ongoing contracts of water use, though generally promising, are limited because of the operation of hydropower schemes. At present the exfiltrations of groundwater mitigate the impacts of flow regulation on the ecological integrity of the floodplains. Copyright © 2002 John Wiley & Sons, Ltd. [source]