Holocene cool‐water carbonate and terrigenous sediments from southern Spencer Gulf,South Australia     

M. K. Fuller  Y. Bone  V. A. Gostin  C. C. Von Der Borch 《Australian Journal of Earth Sciences》2013,60(4):353-363

Holocene sediments from southern Spencer Gulf are cool‐water carbonate‐rich gravels and sands, dominated by molluscs and Bryozoa. Five sedimentary fades are recognized: (i) molluscan gravel; (ii) branching coralline‐algal gravel, associated with shallow partially protected environments; (iii) molluscan‐biyozoan sand; (iv) mixed bioclastic sand, representative of the deeper central region of the lower gulf; and (v) bryozoan gravel, an isolated fades developed in a semi‐protected micro‐environment. The southern gulf is characterized by complex oceanographic conditions together with variations in water depth and substrate. The sediments share the characteristics of both the southern shelf and upper Spencer Gulf. Grain‐size distribution and sedimentary facies are controlled by a combination of all the above processes. Past sea level fluctuations are recognized from sea floor strand‐line deposits. The relic component of the palimpsest sediments has eroded from the Pleistocene aeolianite dunes. The sediments, therefore, reflect both the modern marine and past environments.  相似文献   

Screening the current soil drainage class map of Flanders (Belgium) for its predictive quality     

J. Van de Wauw  P.A. Finke 《水文研究》2012,26(20):3003-3011

The predictive quality of the current drainage class map of Flanders was evaluated using data from two monitoring networks: one with good spatial coverage but poor temporal coverage and another with better temporal but poor spatial coverage. We combine both networks to obtain 1678 point predictions for mean highest water (MHW) and mean lowest water (MLW) tables by applying time series modelling and total least squares regression. The resulting MHW and MLW point data set was used to evaluate the currency of the existing map and to identify regional differences. The quality of the current map is moderate, and large differences occur between regions. Especially the Campine region shows large and systematic differences, whereas the southeastern hills and chalk–loam region is relatively accurate. If more weight is given to errors in the wetter drainage classes, about 50% of the area of Flanders would benefit from remapping. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Effects of commercial timber harvesting on streamflow regimes in the Plynlimon catchments,mid‐Wales     

M. Robinson  A. Dupeyrat 《水文研究》2005,19(6):1213-1226

This paper presents the first large‐scale British study of the impacts of commercial forest cutting on stream‐flow regimes. The 70% forested headwaters of the River Severn are part of the intensively instrumented long‐term Plynlimon catchment study into the impact of land use on stream flow. The forest area, comprising predominantly Sitka spruce (Picea sitchensis), was planted mainly in the 1930s and 1940s. Harvesting commenced in the mid‐1980s and over the study period about half the forest has been felled. Changes in annual water yield and extreme flows were studied in four nested catchments ranging in area from about 1 to 10 km² and compared with an adjacent benchmark grassland catchment. As expected from earlier process studies the cutting of the forest increased total annual flows. Less expected was the clear evidence that the felling augmented low flows. This informs a long‐standing debate whether upland forestry increases or reduces baseflows. A particularly notable result was the lack of impact of the harvesting on storm peak flows. This may result from the application of forest management guidelines designed to reduce soil damage and erosion during the harvesting, and indicates that the forest itself has a limited impact on flooding. These findings are timely because British forest expansion peaked in the 30 years following the Second World War, and large areas of these woodlands are now approaching economic maturity and will be harvested in the next two decades. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Impact of soil and water conservation measures on catchment hydrological response—a case in north Ethiopia     

Jan Nyssen  Wim Clymans  Katrien Descheemaeker  Jean Poesen  Ine Vandecasteele  Matthias Vanmaercke  Amanuel Zenebe  Marc Van Camp  Mitiku Haile  Nigussie Haregeweyn  Jan Moeyersons  Kristine Martens  Tesfamichael Gebreyohannes  Jozef Deckers  Kristine Walraevens 《水文研究》2010,24(13):1880-1895

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200‐ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post‐harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre‐implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5 mm (RC = 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002–2003 (ΔT/WS = 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Long-Term Variability of Volume and Heat Transport in the Nordic Seas: A Model Study     

Sarah Lundrigan 《大气与海洋》2013,51(2):156-168

This article presents results from a model study of interannual and decadal variability in the Nordic Seas. Fifty years of simulations were conducted in an initial condition ensemble mode forced with the National Centers for Environmental Prediction (NCEP) reanalysis. We studied two major events in the interannual and interdecadal variability of the Nordic Seas during the past fifty years: the Great Salinity Anomaly in the 1960s and early 1970s and the warming of the Arctic and subarctic oceans in the late 1990s.

Previous studies demonstrated that the Great Salinity Anomaly observed in the subarctic ocean in 1960 was originally generated by intensified sea-ice and freshwater inflow from the Arctic Ocean. Our model results demonstrate that the increase in the transport of fresh and cold waters through Fram Strait in the 1960s was concurrent with a reduction in the meridional water exchange over the Greenland–Scotland Ridge. The resulting imbalance in salinity and heat fluxes through the strait and over the ridge also contributed to the freshening of the water masses of the Nordic Seas and intensified the Great Salinity Anomaly in the Nordic Seas.

The warming of the Atlantic Waters in the Nordic Seas and Arctic Ocean during the past two decades had an important impact on the variability of these two ocean basins. Some previous observational and model studies demonstrated that the warming of the subpolar Atlantic Ocean in the late 1990s and the meridional transport of the Atlantic Water mass (AW) into the Nordic Seas and Arctic Ocean contributed to this process. At the same time, observations show that the warming of the AW in the Nordic Seas started in the 1980s (i.e., earlier than the warming of the subpolar North Atlantic Ocean). Our model results suggest that this process was triggered by an imbalance in the lateral heat fluxes through Fram Strait and over the Greenland–Scotland Ridge. In the late 1980s the AW transport over the Greenland–Scotland Ridge was stronger than normal while the exchange through Fram Strait was close to normal. The related imbalance in the lateral heat fluxes through the strait and over the ridge warmed the Nordic Seas and caused an increase in the temperature of the AW inflow to the Arctic Ocean in the late 1980s (i.e., about a decade earlier than the warming of the source of the AW in the subpolar North Atlantic Ocean). Thus the model results suggest that the imbalance in lateral heat and salinity fluxes through the strait and over the ridge connecting the Nordic Seas to the North Atlantic and Arctic oceans could amplify the interannual variability in the subarctic ocean.

[Traduit par la rédaction] Cet article présente les résultats d'une étude par modèle de la variabilité interannuelle et décennale dans les mers nordiques. Nous avons effectué des simulations sur une période de cinquante ans en mode d'ensemble de conditions initiales forcé avec les réanalyses des NCEP (National Centers for Environmental Prediction). Nous avons étudié deux événements majeurs survenus dans la variabilité interannuelle et décennale des mers nordiques au cours des cinquante dernières années : la grande anomalie de salinité des années 1960 et du début des années 1970 et le réchauffement des océans Arctique et subarctique vers la fin des années 1990.

Des études précédentes ont démontrées que la grande anomalie de salinité observée dans l'océan subarctique en 1960 a été causée par une intensification de l'apport de glace de mer et d'eau douce depuis l'océan Arctique. Les résultats que nous avons obtenus du modèle montrent que l'accroissement du transport d'eau douce et froide à travers le détroit de Fram dans les années 1960 s'est produit en même temps qu'une réduction dans l’échange méridien d'eau au-dessus de la crête Groenland–Écosse. Le déséquilibre résultant dans les flux de salinité et de chaleur à travers le détroit et au-dessus de la crête a aussi contribué à l'adoucissement des masses d'eau des mers nordiques et a intensifié la grande anomalie de salinité dans les mers nordiques.

Le réchauffement des eaux atlantiques dans les mers nordiques et dans l'océan Arctique au cours des deux dernières décennies a eu un impact important sur la variabilité de ces deux bassins océaniques. Des études observationnelles et par modèle précédentes ont établi que le réchauffement de l'océan Atlantique subpolaire dans les années 1990 et le transport méridien de la masse d'eau atlantique dans les mers nordiques et dans l'océan Arctique ont contribué à ce processus. En même temps, les observations montrent que le réchauffement des eaux atlantiques dans les mers nordiques a commencé dans les années 1980 (c.–à–d. plus tôt que le réchauffement de l'océan Nord-Atlantique subpolaire). Les résultats du modèle suggèrent que ce processus a été déclenché par un déséquilibre dans les flux de chaleur latéraux à travers le détroit de Fram et au-dessus de la crête Groenland–Écosse. À la fin des années 1980, le transport des eaux atlantiques au-dessus de la crête Groenland–Écosse était plus fort que la normale alors que l’échange à travers le détroit de Fram était près de la normale. Le déséquilibre résultant dans les flux de chaleur latéraux à travers le détroit et au-dessus de la crête a réchauffé les mers nordiques et causé une augmentation de la température des eaux atlantiques parvenant à l'océan Arctique à la fin des années 1980 (c.-à-d. environ une décennie avant le réchauffement de la source d'eaux atlantiques dans l'océan Nord-Atlantique subpolaire). Donc, les résultats du modèle suggèrent que le déséquilibre dans les flux de chaleur et de salinité latéraux à travers le détroit et au-dessus de la crête reliant les mers nordiques à l'Atlantique Nord et à l'Arctique pourrait amplifier la variabilité interannuelle dans l'océan subarctique.  相似文献   

Water,restite and granite mineralisation     

A. J. R. White 《Australian Journal of Earth Sciences》2013,60(4):551-555

Dehydration (vapour absent) partial melting reactions in the Earth's crust produce a hydrous granitic melt phase, new anhydrous minerals that are mostly pyroxenes, and new plagioclase more calcic than the initial plagioclase. These solid phases of the melt reaction are restite. If the restite is carried to high levels in the crust as a component of the magma, cooling and crystallisation to granite will result in back reactions in which the H₂O in the melt phase is consumed and is not then available to form a hydrothermal solution. Even in magmas in which some restite has been removed there will be some back reaction and again less H₂O. Only fractional crystallisation will enrich the H₂O in the magma in sufficient amounts to form a substantial quantity of hydrothermal solution and possible mineralisation.  相似文献   

Long‐term final void salinity prediction for a post‐mining landscape in the Hunter Valley,New South Wales,Australia     

G. R. Hancock  A. Wright  H. De Silva 《水文研究》2005,19(2):387-401

Opencast mining alters surface and subsurface hydrology of a landscape both during and post‐mining. At mine closure, following opencast mining in mines with low overburden to coal ratios, a void is left in the final landform. This final void is the location of the active mine pit at closure. Voids are generally not infilled within the mines' lifetime, because of the prohibitive cost of earthwork operations, and they become post‐mining water bodies or pit lakes. Water quality is a significant issue for pit lakes. Groundwater within coal seams and associated rocks can be saline, depending on the nature of the strata and groundwater circulation patterns. This groundwater may be preferentially drawn to and collected in the final void. Surface runoff to the void will not only collect salts from rainfall and atmospheric fallout, but also from the ground surface and the weathering of fresh rock. As the void water level rises, its evaporative surface area increases, concentrating salts that are held in solution. This paper presents a study of the long term, water quality trends in a post‐mining final void in the Hunter Valley, New South Wales, Australia. This process is complex and occurs long term, and modelling offers the only method of evaluating water quality. Using available geochemical, climate and hydrogeological data as inputs into a mass‐balance model, water quality in the final void was found to increase rapidly in salinity through time (2452 to 8909 mg l⁻¹ over 500 years) as evaporation concentrates the salt in the void and regional groundwater containing high loads of salt continues to flow into the void. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Mosaic desert pavement influences water infiltration and vegetation distribution on fluvial fan surfaces     

Dejin Wang  Wenzhi Zhao  Hong Zhou  Weicheng Luo  Hu Liu 《水文研究》2021,35(9):e14373

Desert pavements (DPs) are critical for maintaining ecological stability and promoting near-surface hydrological cycling in arid regions. However, few studies have focused on eco-hydrological processes of DPs in the ecological systems of fluvial fans. Although DP surfaces appear to be barren and flat, we found that the surfaces are characterized by surface mosaic patterns of desert pavement (mosaic DP) and bare ground (mosaic BG). We investigated the effects of mosaic DP on water infiltration and vegetation distribution at six sites in fluvial fans (one on a hillside and five within the sectors of fans) along a southwest belt transect in northern Linze County, in the central Hexi Corridor (China). We found significant differences in mosaic DP between the hillside and sector sites in terms of pavement thickness and vesicular horizon thickness (Av thickness), particle composition, and bulk density, although significant differences were absent for mass soil water content, gravel coverage, and surface gravel size. The mosaic DP inhibited water infiltration by the pavement layer, where the sorptivity (S), initial infiltration rate (i_int), steady-state infiltration rate (i_sat) and infiltration time (T) averaged 1.19 cm/min^-0.5, 0.64 cm/min, 0.13 cm/min and 12.76 min, respectively. Where the pavement layer was scalped, the S, i_int, and i_sat increased by 0.27 cm/min^-0.5, 0.52 cm/min, and 0.40 cm/min, respectively, and the T reduced by 7.42 min. Water infiltration was mainly controlled by the pavement layer thickness (+), Av thickness (−), surface gravel coverage (−), fine earth (+) and fine gravel (−) in the pavement layer. The DP surfaces only had a sparse covering of shrubs, but an abundance of herbs. Few shrubs were present on the mosaic DP, but a greater number of shrubs and herbs grew on the mosaic BG. It can be concluded that DPs can maintain vegetation stability for different surface mosaic patterns. This study deepens our understanding of the eco-hydrological cycle of DP landscapes in arid regions.  相似文献   

Application of a Bayesian model to infer the contribution of coalbed natural gas produced water to the Powder River,Wyoming and Montana          下载免费PDF全文

Jason M. Mailloux  Kiona Ogle  Carol D. Frost 《水文研究》2014,28(4):2361-2381

The Powder River Basin (PRB) of Wyoming and Montana contains significant coal and coal bed natural gas (CBNG) resources. CBNG extraction requires the production of large volumes of water, much of which is discharged into existing drainages. Compared to surface waters, the CBNG produced water is high in sodium relative to calcium and magnesium, elevating the sodium adsorption ratio (SAR). To mitigate the possible impact this produced water may have on the quality of surface water used for irrigation, the State of Montana passed water anti‐degradation legislation, which could affect CBNG production in Wyoming. In this study, we sought to determine the proportion of CBNG produced water discharged to tributaries that reaches the Powder River by implementing a four end‐member mixing model within a Bayesian statistical framework. The model accounts for the ⁸⁷Sr/⁸⁶Sr, δ¹³C_DIC, [Sr] and [DIC] of CBNG produced water and surface water interacting with the three primary lithologies exposed in the PRB. The model estimates the relative contribution of the end members to the river water, while incorporating uncertainty associated with measurement and process error. Model results confirm that both of the tributaries associated with high CBNG activity are mostly composed of CBNG produced water (70–100%). The model indicates that up to 50% of the Powder River is composed of CBNG produced water downstream from the CBNG tributaries, decreasing with distance by dilution from non‐CBNG impacted tributaries from the point sources to ~10–20% at the Montana border. This amount of CBNG produced water does not significantly affect the SAR or electrical conductivity of the Powder River in Montana. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Temporal patterns and controls on runoff magnitude and solution chemistry of urban catchments in the semiarid southwestern United States     

Erika L. Gallo  Paul D. Brooks  Kathleen A. Lohse  Jean E. T. McLain 《水文研究》2013,27(7):995-1010

Urban expansion and the scarcity of water supplies in arid and semiarid regions have increased the importance of urban runoff to localized water resources. However, urban catchment responses to precipitation are poorly understood in semiarid regions where intense rainfall often results in large runoff events during the short summer monsoon season. To evaluate how urban runoff quantity and quality respond to rainfall magnitude and timing, we collected stream stage data and runoff samples throughout the 2007 and 2008 summer monsoons from four ephemeral drainages in Tucson, Arizona. Antecedent rainfall explained 20% to 30% of discharge (mm) and runoff ratio in the least impervious (22%) catchment but was not statistically related to hydrologic responses at more impervious sites. Regression models indicated that rainfall depth, imperviousness and their combined effect control discharge and runoff ratios (p < 0.01, r² = 0.91 and 0.75, respectively). In contrast, runoff quality did not vary with imperviousness or catchment size. Rainfall depth and duration, time since antecedent rainfall and event and cumulative discharge controlled runoff hydrochemistry and resulted in five specific solute response patterns: (i) strong event and seasonal solute mobilization (solute flush), (ii) event chemostasis and strong seasonal flush, (iii) event chemostasis and weak seasonal flush, (iv) event and seasonal chemostasis and (v) late seasonal flush. Our results indicate that hydrologic responses of semiarid catchments are controlled by rainfall partitioning at the event scale, whereas wetting magnitude, frequency and timing alter solute stores readily available for transport and control temporal runoff quality. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献