查看更多>>摘要：Snow is an important form of water storage which profoundly affects the hydrological processes in alpine watersheds, especially the runoff during snowmelt period. As the strong impact of climate change, the concern about snowmelt water to runoff in alpine watersheds is dramatically growing. However, the studies are mainly focused on arid and semi-arid areas, the research on semi-humid regions sensitive to the climate change need to be strengthened. In this study, for evaluating the contribution of snowmelt water to runoff in snowmelt period, we calculated the stable isotope values (8D, 818O and d-excess) of different water bodies including river, snow, rain, groundwater, and snowmelt water in the Erdaobaihe River watershed of Changbai Mountains area. The results indicated that the 818O values of snowmelt water showed an increasing trend with increasing temperature, while the d-excess values of snowmelt water showed a decreasing trend. During the snowmelt period, the snow cover ratio varied from 20.31% to 0.02%. The contribution ratio of snowmelt water to runoff was from 14.4% to 59.8% with average of 42.60% and the total contribution discharge was about 36.56 x 106 m3, which was higher than inland mountainous areas as different elevation and climate. As the stable water source of river, the groundwater contributed 19.2-61.6% with average of 43.88%. The snowmelt water plays an important role in regional water balance. Owing to climate change, the snowfall period in Changbai Mountains was gradually shortening and extreme snowfall events were increasing. The results will provide evidence for further hydrological studies and help to plan future water management strategies in the alpine watershed.
Peters, Chelsea N.Kimsal, CharlesFrederiks, Ryan S.Paldor, Anner...
12页
查看更多>>摘要：Groundwater-surface water interactions and associated water management issues are complicated by the risk of salinization along coastlines. Groundwater pumping can be a driving factor of streamflow depletion and allow for increased stream saltwater intrusion. In this study, we develop an analytical framework combining two analytical approaches to calculate the length of saltwater intrusion at high slack water and the stream depletion rate due to groundwater pumping. We test this framework using data from the Savannah River in southeastern U.S and use it to explore saltwater intrusion in the surface water system. The analytical approach produces an accurate estimate of the position of the salt front at approximately 56 km inland. Current pumping rates decrease streamflow by less than 1%, resulting in an increase in the saltwater intrusion length of 100 m. Increased groundwater pumping scenarios, however, show a risk of extending the saltwater intrusion length up to 4 km inland. In these cases, effects from pumping-induced saltwater intrusion would equal or exceed the impacts of sea-level rise or geomorphic change. Salinity is a critical factor in the ecological balance of this estuarine ecosystem and this analytical approach allows for investigation of hypothetical groundwater development in the region. We show, for the first time, the direct link between groundwater pumping and coastal stream salinity that should be an important management consideration all along developed coastlines.
查看更多>>摘要：Exploring and exploiting high-temperature (even supercritical) geothermal resources are significant to meet energy demands and reduce carbon emissions. The Yangbajing geothermal field is the most exploited in China, with the currently highest temperature (329.8 degrees C) measured in a geothermal well. However, whether there are supercritical geothermal fluids beneath the deep parts of this geothermal field is under controversy. In this paper, the water isotope, chemical compositions, and C-He isotopes of gas samples were collected and analyzed. The geothermal water originated from the mixing of meteoric water and magmatic water (25%). The sources of CO2 in the geothermal field were dominated by the thermogenic degassing of carbonates and metasediments in the crust while the radioactive decay of U and Th in granite is the dominated source of He. The temperatures of three different reservoirs are 150 +/- 15 degrees C, 250 +/- 10 degrees C, and -320 degrees C (with a depth of -8 km), respectively. These were obtained using dissolved gas, soil CO2 flux, and noble gas geothermometers. Unlike other supercritical geothermal fields worldwide with larger, shallower, basaltic magma chambers, the Yangbajing geothermal field has a deep-seated, small-scale, granitic magma chamber. Thus, its geological conditions are not conducive for gestating supercritical fluids. These results are of great significance for exploring and developing hightemperature (even ultra-high-temperature) geothermal resources in China.
查看更多>>摘要：Dolomitization, as one of the most important diagenetic processes in carbonate reservoirs, is essential for reservoir porosity development and evolution. However, the geochemical mechanism of dolomitization is unclear. In this study, theoretical analysis, laboratory physical experiments, thermodynamic calculation and computer numerical simulation were combined to explore the coupled effects of temperature and solution compositions on dolomitization. A series of water-rock reaction experiments at various temperature were firstly carried out. X-ray diffraction (XRD), scanning electron microscope (SEM), ICP-MASS and other analytical methods were used to monitor ion concentration, relative content and surface morphology of all minerals. Secondly, molecular dynamics (MD) simulation and thermo-hydro-chemical (THC) coupling simulation were employed to analyze various processes of dissolution, precipitation and transformation of carbonate rock. Finally, combining thermodynamic calculation, coupled effects of temperature and solution compositions on dolomitization were determined and the optimum formation conditions of dolomite were confirmed. Dolomitization experienced a series of transitional processes from calcite -> Mg-bearing calcite -> high-calcium dolomite -> low-calcium dolomite. At 60 degrees C, 80 degrees C and 95 degrees C, the equilibrium constants of dolomitization are 1.67, 1.75 and 1.80, respectively. Dolomite is formed when Mg/Ca ratio equals 5.3 (at 95 degrees C) and the scope activity of Mg2+ is 32.91-54.52%. It would need a much higher activated Mg2+ or it may be impossible to form dolomite if the Mg/Ca ratio is less than 3. This study has revealed coupled effects of temperature and solution compositions on metasomatism dolomitization, which could provide a basis for evaluating and predicting high-quality carbonate reservoirs.
查看更多>>摘要：Human activities, such as discharging nuclear wastewater into the ocean, can put coasts in the risk of being exposed to radioactive contaminations. The radionuclides may potentially intrude into coastal aquifers from the ocean and endanger the groundwater resources, either laterally through subsurface or vertically through land surface during ocean surge induced inundation. This study attempted to investigate the temporal and spatial scales of these intrusion processes using an experimental site near Bremerhaven, northern Germany. A fully coupled surface-subsurface flow and transport model was employed to simulate the groundwater flow and the transport of TDS (total dissolved salt), H-3 and C-14, under conditions with or without an ocean surge event. Scenarios of different exposure schemes were designed by varying the exposure duration and radionuclide concentrations. The intrusion and post-exposure recovery were assessed via contaminated volume and area, intrusion length, and recovery time. Results show that, depending on exposure duration, the intrusion of H-3 and C-14 can cause serious contamination in the coastal aquifer, with up to 18.9 km(2) land area being contaminated and reaching up to 3.3 km landward from the shore. H-3 shows a 'harder intrusion, easier recovery' pattern due to its higher decay rate. The full recovery may take up to 70 years and 217 years (considering 30-years-exposure) for H-3 and C-14, respectively. An ocean surge event is more likely to exacerbate the intrusion, but it does not significantly change the full recovery time. Shorter exposure duration should be favored to minimize the influences on the coastal aquifer when the total exposure quantity is fixed. This study highlights the severity of radioactive contamination in coastal aquifers and the difficulty of recovery. Thus, cautious decision should be made concerning the possible impacts of releasing radioactive wastewater on coastal life and human beings.
查看更多>>摘要：The interaction between the sewer network and the overland runoff is challenging to study due to the complex flow exchange between the two systems during flooding. The complexity increases when dealing with subcatchments that contain separated urban satellite areas that share the sewer network. Under this context it is possible to devise likely model structures which render determinist approaches spuriously precise. In this paper, a methodology is proposed for to devise multiple model structures for urban flood inundation uncertainty. Seven different model structures are assembled and validated in a case study Baiersdorf for the flood event from 21st of 2007 to produce a probabilistic flood inundation uncertainty map. The results show that the flood inundation extent uncertainty differs across the study area. The overall flood extent uncertainty covers 14.15% of the inundation area. The highest uncertainty is found to be 30.87% at the North part up of the study area. Many small areas of high uncertainty are concentrated in the main urban area, and close to most of the upstream boundary conditions. It is conducted that the highest uncertainties are likely to be found downstream of the coupling points of the 2D overland flow with either the 1D sewer system or the 1D overland flow network. These results highlight the need to consider multiple model structures when estimating the uncertainty of the flood inundation extents.
Barua, ShovonCartwright, IanDresel, P. EvanMorgenstern, Uwe...
13页
查看更多>>摘要：Determining the sources and mean transit times (MTTs) of water that generates streamflows is important for understanding and managing headwater catchments. The sources and especially the MTTs of water that contributes to streamflow in seasonally intermittent streams are far less studied than for perennial streams. Here we use major ions, dissolved organic carbon, stable isotopes, radon and tritium to quantify the sources and MTTs of intermittent streamflows in three headwater catchments (Banool, McGill and Plantation) from a semi-arid area in southeast Australia. At the start of streamflows, the MTTs of stream water varied from 25 to 42 years in the 1.51 km(2) Banool catchment, 3 to 4 years in the 3.38 km(2) McGill catchment and 9 to 14 years in the 3.41 km(2) Plantation catchment. Winter rainfall increased the relative contribution of younger waters in all three catchments. During higher winter streamflows, the MTTs of stream water reduced to <= 5 years in the Banool catchment and <1 year in the McGill and Plantation catchments. The sources of streamflow also differed between the catchments. Regional groundwater, which close to the stream has a residence time of several hundred years, dominated in the Banool catchment, whereas younger water (residence times of up to 9 years) stored in the riparian zone was the main source in the McGill and Plantation catchments. The differences in MTTs between the catchments may reflect land-use differences, especially the presence of plantation forests in the McGill and Plantation catchments. Overall, due to being less well-connected to the regional groundwater, the MTTs of these intermittent streams are far shorter than those reported for perennial headwater streams in southeast Australia. The short MTTs indicate that these intermittent streams are vulnerable to short-term variations in rainfall.
Di Dato, MariainesD'Angelo, ClaudiaCasasso, AlessandroZarlenga, Antonio...
14页
查看更多>>摘要：Groundwater has been increasingly used to provide low-carbon heating and cooling of buildings with open-loop shallow geothermal systems. Water is generally reinjected into the same aquifer after the heat exchange in order to avoid the aquifer depletion. However, this can result in the return of part of the injected water to the production well(s), causing a gradual thermal alteration known as thermal feedback. Thermal feedback is a major design issue of open-loop shallow systems but, so far, it has been mainly addressed neglecting the heterogeneity of the aquifer properties. This study investigates the impact of aquifer heterogeneity on two main metrics that characterize thermal feedback: thermal breakthrough time (i.e., the first arrival time of the thermal plume) and recirculating ratio (i.e., the fraction of water coming back to production well). A stochastic approach was adopted performing a large number of numerical simulations that cover a wide range of possible scenarios. The results highlight that conductivity heterogeneity plays a major influence on the temperature evolution at the production well. The breakthrough time alone might lead to misleading evaluations of the system efficiency, given that a few particles can reach the production well by traveling in the highly-conductive layers. Conversely, both the heterogeneity and the thermal dispersivity have a negligible impact on the recirculating ratio, which quantifies the long-term evolution of thermal feedback. As a consequence, the available approaches based on advection-only and homogeneous medium are a robust tool to predict the long-term behavior of shallow openloop geothermal systems.
查看更多>>摘要：Fecal coliform (FC) indicators are commonly used to evaluate microbial or fecal contamination in surface water. As an important tributary of the Yangtze River in China, the Tuojiang River not only receives polluted water but is also a source of drinking water. Previous studies have reported the presence of conventional chemical pollutants, but the contamination and human health risk of FC in this watershed have usually been ignored. In this study, monthly FC concentration data from 2008 to 2018 were utilized to analyze the spatiotemporal distribution and to assess human health risk for daily drinking water by quantitative microbial risk assessment (QMRA) and disability adjusted life year (DALY) models. The results showed that there were significant monthly variations in the concentrations of FC, and the concentrations in May to August were significantly higher than those in other months. The annual concentration in the whole watershed increased slowly from 2008 to 2018. The annual probability of falling ill (Pill_year) caused by FC upstream, midstream and downstream was 4.30 +/- 3.92 x 10(-5), 1.38 +/- 0.49 x 10(-5) and 3.38 +/- 2.72 x 10(-5), respectively. It was found that 5.82% of the DALY values were greater than the limit of 10(-6) per person per year (pppy) and could be defined as high health risk points. A total of 37.3% of samples could be deemed potential risk points whose DALY values were between 10(-7) and 10(-6) pppy. There were significant spatial differences in FC concentrations and health risk among upstream, midstream, and downstream regions. With the rising health-risk value, the high-risk region has transferred from downstream to upstream since 2015. Furthermore, we found that domestic wastewater and livestock sewerage were deemed to be primary sources of FC in the Tuojiang watershed. Moreover, the increasing health risk faced by the local people in the watershed should receive more attention from the public and government. The results of this study could provide insight into the management of FC pollution and health risks, such as sewage treatment, livestock manure management, and personal dietetic hygiene.
查看更多>>摘要：The impact of monsoon on rainfall in the Lancang-Mekong River Basin (LMRB) has been well understood, but its impact on flood characteristic across the basin is still unclear. To investigate this impact, the Variable Infiltration Capacity (VIC) hydrological model was used to generate the basin-wide discharge and extract flood characteristics. Indian Summer Monsoon (ISM), Western North Pacific Monsoon (WNPM), and their combined effect (ISWN) were considered and represented by monsoon index. The monsoon impact area was firstly obtained based on the monsoon impact on rainfall, followed by the anomaly analyses of flood characteristics within the impact area to quantify the monsoon impact on floods at local and spatial scales. The results show that the ISM and WNPM (or ISWN) can significantly modulate up to 20% of the rainfall interannual variability in the western and eastern parts of the basin, respectively. The monsoon impact on flood is regionally distributed with impact in tributary larger than mainstream. Over half of the monsoon impact areas show the flood start date averagely advances (delays) 8-12 days, flood volume averagely increases (decreases) by 9%-17.5% and Q10 averagely increases (decreases) by 7.4%-14.4% during the strong (weak) monsoon years. Also, the comparisons between monsoon local and spatial impacts reveal that the trade-off of water from different areas can disturb the monsoon impact on flood, suggesting that more stations should be used when using the observed data to analyze the monsoon impact. More importantly, the ISM tends to cause the severe flood in northern Thailand, while WNPM and ISWN mainly induce the severe flood in the southeastern part of the LMRB. This study could help to increase the knowledge of the impact of climate change on flood and help with the regional flood managements.
NSTL
Elsevier