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1.
Geochemical fluxes from watersheds are typically defined using mass-balance methods that essentially lump all weathering processes operative in a watershed into a single flux of solute mass measured in streamflow at the watershed outlet. However, it is important that we understand how weathering processes in different hydrological zones of a watershed (i.e., surface, unsaturated, and saturated zones) contribute to the total geochemical flux from the watershed. This capability will improve understanding of how geochemical fluxes from these different zones may change in response to climate change. Here, the geochemical flux from weathering processes occurring solely in the saturated zone is investigated. This task, however, remains exceedingly difficult due to the sparsity of subsurface sampling points, especially in large, remote, and/or undeveloped watersheds. In such cases, springflow is often assumed to be a proxy for groundwater (defined as water residing in fully saturated geologic formations). However, springflow generation may integrate different sources of water including, but not limited to, groundwater. The authors’ hypothesis is that long-term estimates of geochemical fluxes from groundwater using springflow proxies will be too large due to the integrative nature of springflow generation. Two conceptual models of springflow generation are tested using endmember mixing analyses (EMMA) on observations of spring chemistries and stable isotopic compositions in a large alpine watershed in the San Juan Mountains of southwestern Colorado. In the “total springflow” conceptual model, springflow is assumed to be 100% groundwater. In the “fractional springflow” conceptual model, springflow is assumed to be an integration of different sources of water (e.g., groundwater, unsaturated flow, preferential flow in the soil, etc.) and groundwater is only a fractional component. The results indicate that groundwater contributions in springflow range from 2% to 100% overall and no springs are consistently composed of 100% groundwater; providing support for the fractional springflow conceptual model. Groundwater contributions are not strongly correlated with elevation, spring contributing area, spring discharge, or seasonality. This variability has a profound effect on long-term geochemical fluxes. The geochemical fluxes for total springflow overestimate long-term solute release by 22–48% as compared to fractional springflow. These findings illustrate that springflow generation, like streamflow generation, integrates many different sources of water reflecting solute concentrations obtained along many different geochemical weathering pathways. These data suggest that springs are not always ideal proxies for groundwater. Springs may be integrating very distinct portions of the groundwater flow field and these groundwater contributions may become mixed at the spring emergence with much younger sources of water that have never resided in the groundwater system. 相似文献
2.
陆面模式中土壤冻融过程参数化研究进展 总被引：21，自引：0，他引：21
土壤冻融过程在寒区水文和气候系统中有着重要作用。陆面模式中土壤冻融过程的参数化对模式的设计和模拟结果有着关键作用。通过对广泛应用的Bucket，SIB，BATS，VIC，BEAS， LSM等几种主要的陆面模式中的冻融过程参数化方案进行了总结和比较。首先，详尽地描述了土壤冻融与气候变化的数值模拟研究，总结和评述了土壤冻融过程对气候变化的作用。其次，对几种主要的陆面过程模式在土壤水热参数化方案中对冻融过程的考虑及其特点进行了比较和讨论。还对冻结深度和冻结周期的预报模式进行了简介，最后对该领域当前面临的主要研究问题进行了探讨和阐述。 相似文献
3.
J. B. Callegary C. P. Kikuchi J. C. Koch M. R. Lilly S. A. Leake 《Hydrogeology Journal》2013,21(1):25-39
Groundwater in the US state of Alaska is critical to both humans and ecosystems. Interactions among physiography, ecology, geology, and current and past climate have largely determined the location and properties of aquifers as well as the timing and magnitude of fluxes to, from, and within the groundwater system. The climate ranges from maritime in the southern portion of the state to continental in the Interior, and arctic on the North Slope. During the Quaternary period, topography and rock type have combined with glacial and periglacial processes to develop the unconsolidated alluvial aquifers of Alaska and have resulted in highly heterogeneous hydrofacies. In addition, the long persistence of frozen ground, whether seasonal or permanent, greatly affects the distribution of aquifer recharge and discharge. Because of high runoff, a high proportion of groundwater use, and highly variable permeability controlled in part by permafrost and seasonally frozen ground, understanding groundwater/surface-water interactions and the effects of climate change is critical for understanding groundwater availability and the movement of natural and anthropogenic contaminants. 相似文献
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5.
Temporal and spatial changes of the hydrological cycle are the consequences of climate variations. In addition to changes in surface runoff with possible floods and droughts, climate variations may affect groundwater through alteration of groundwater recharge with consequences for future water management. This study investigates the impact of climate change, according to the Special Report on Emission Scenarios (SRES) A1B, A2 and B1, on groundwater recharge in the catchment area of a fissured aquifer in the Black Forest, Germany, which has sparse groundwater data. The study uses a water-balance model considering a conceptual approach for groundwater-surface water exchange. River discharge data are used for model calibration and validation. The results show temporal and spatial changes in groundwater recharge. Groundwater recharge is progressively reduced for summer during the twenty-first century. The annual sum of groundwater recharge is affected negatively for scenarios A1B and A2. On average, groundwater recharge during the twenty-first century is reduced mainly for the lower parts of the valley and increased for the upper parts of the valley and the crests. The reduced storage of water as snow during winter due to projected higher air temperatures causes an important relative increase in rainfall and, therefore, higher groundwater recharge and river discharge. 相似文献
6.
The ability to detect hydrologic variation in large arctic river systems is of major importance in understanding and predicting effects of climate change in high-latitude environments. Monitoring uranium isotopes (234U and 238U) in river water of the Yukon River Basin of Alaska and northwestern Canada (2001?C2005) has enhanced the ability to identify water sources to rivers, as well as detect flow changes that have occurred over the 5-year study. Uranium isotopic data for the Yukon River and major tributaries (the Porcupine and Tanana rivers) identify several sources that contribute to river flow, including: deep groundwater, seasonally frozen river-valley alluvium groundwater, and high-elevation glacial melt water. The main-stem Yukon River exhibits patterns of uranium isotopic variation at several locations that reflect input from ice melt and shallow groundwater in the spring, as well as a multi-year pattern of increased variability in timing and relative amount of water supplied from higher elevations within the basin. Results of this study demonstrate both the utility of uranium isotopes in revealing sources of water in large river systems and of incorporating uranium isotope analysis in long-term monitoring of arctic river systems that attempt to assess the effects of climate change. 相似文献
7.
Groundwater modeling is an effective tool for managing the groundwater resource and to predict for the future. There is a need for proper quantification of the scarce water resources that are under threat because of the population explosion, industrialization, urbanization and climate change. More than 60% of India is underlained by hard rock aquifers. The Hiranyakeshi watershed of Ghataprabha sub-basin, chosen for the study is also under hard rock aquifer and faces severe groundwater problems. This is due to majority of the agricultural and industrial activities in the watershed depend on the groundwater. A 3-D groundwater flow model, viz. Visual MODFLOW was used for the study with two conceptual layers. The first layer is a weathered zone which is about 20-30m from the top, followed by a second layerof fractured zone which is about 30-40m from the first. The model was simulated for a period of seven years (2008-2014), under transient case. The results from the modeling shows that for the next 10 years the water table is believed to decrease more than 50m in the study area. To overcome this critical stage, the present draft should be reduced by nearly 50%. 相似文献
8.
山东淄博市地下水资源评价及其合理开发利用研究 总被引：12，自引：4，他引：8
本文采用有限单元法进行地下水资源评价以解决评价区供水面积大、精度要求高的矛盾。首先根据实际的开采量和长期观测孔的水位资料,校正数学模型,反求有关参数;然后给定开采方案进行未来水头的预测;最后研究地下水资源的合理开发利用问题。利用有限单元法进行水源地或单一含水层的地下水资源评价已被证明是先进的、有效的。本文是对水文地质条件非常复杂的大面积的区域,用有限单元法进行地下水资源评价的一种尝试,可供类似地区参考。 相似文献
9.
2009年10月在西安召开第八届国际冻土工程会议, 就冻土地区工程设计与建设、季节冻土区工程冻害防治、冻土物理力学特性、 模型发展及其应用、寒区气候、环境及冷生变化、多年冻土水文学、寒区水资源和土地应用等主要议题进行了广泛交流, 报告了近年来冻土工程与环境研究方面的一些新进展. 从冻土工程设计、施工和评价、普通冻土研究、冻土的物理力学性质、冻土模型发展及应用、 气候变化及冰冻圈环境等方面对该次会议交流的成果进行了总结. 与会研究者认为今后的研究一方面要加强理论研究、工程措施机理研究;另一方面要加强寒区环境对气候变化的响应及反馈、以及环境变化与冻土工程措施之间的相互作用研究. 相似文献
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11.
为深入理解热喀斯特湖与多年冻土间的相互作用,本文以青藏高原北麓河盆地典型热喀斯特湖区域为例,构建考虑热传导和热对流过程的水-冰-热耦合模型,对热喀斯特湖作用下的多年冻土退化特征及热喀斯特湖的水均衡进行模拟,计算地质环境和气候变暖对热喀斯特湖水均衡和冻土的影响。研究结果表明：热喀斯特湖周围冻土逐步退化并形成贯穿融区,导致地下水循环模式发生改变;在地表温度作用下,形成的活动层厚度为3.35 m;热喀斯特湖在整个模拟时段内表现为负均衡,其排泄量在285～388 a间显著增加;地层渗透性能决定了热喀斯特湖和生态环境的发展方向;气候变暖加速多年冻土向季节冻土转变。研究结果可为进一步认识寒旱区生态水文过程提供科学依据。 相似文献
12.
Relation of streams, lakes, and wetlands to groundwater flow systems 总被引：24，自引：10，他引：14
Thomas C. Winter 《Hydrogeology Journal》1999,7(1):28-45
Surface-water bodies are integral parts of groundwater flow systems. Groundwater interacts with surface water in nearly all
landscapes, ranging from small streams, lakes, and wetlands in headwater areas to major river valleys and seacoasts. Although
it generally is assumed that topographically high areas are groundwater recharge areas and topographically low areas are groundwater
discharge areas, this is true primarily for regional flow systems. The superposition of local flow systems associated with
surface-water bodies on this regional framework results in complex interactions between groundwater and surface water in all
landscapes, regardless of regional topographic position. Hydrologic processes associated with the surface-water bodies themselves,
such as seasonally high surface-water levels and evaporation and transpiration of groundwater from around the perimeter of
surface-water bodies, are a major cause of the complex and seasonally dynamic groundwater flow fields associated with surface
water. These processes have been documented at research sites in glacial, dune, coastal, mantled karst, and riverine terrains.
Received, April 1998 · Revised, July 1998, August 1998 · Accepted, September 1998 相似文献
13.
Hydrogeology and sustainable future groundwater abstraction from the Agua Verde aquifer in the Atacama Desert,northern Chile 总被引：1，自引：0，他引：1
Javier Urrutia Jorge Jódar Agustín Medina Christian Herrera Guillermo Chong Harry Urqueta José A. Luque 《Hydrogeology Journal》2018,26(6):1989-2007
The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m3/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity. 相似文献
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15.
Playas are ephemeral, closed-basin wetlands that are hypothesized as an important source of recharge to the High Plains aquifer in central USA. The ephemeral nature of playas, low regional recharge rates, and a strong reliance on groundwater from the High Plains aquifer has prompted many questions regarding the contribution and quality of recharge from playas to the High Plains aquifer. As a result, there has been considerable scientific debate about the potential for water to infiltrate the relatively impermeable playa floors, travel through the unsaturated zone sediments that are tens of meters thick, and subsequently recharge the High Plains aquifer. This critical review examines previously published studies on the processes that control recharge rates and chemistry beneath playas. Reported recharge rates beneath playas range from less than 1.0 to more than 500 mm/yr and are generally 1–2 orders of magnitude higher than recharge rates beneath interplaya settings. Most studies support the conceptual model that playas are important zones of recharge to the High Plains aquifer and are not strictly evaporative pans. The major findings of this review provide science-based implications for management of playas and groundwater resources of the High Plains aquifer and directions for future research. 相似文献
16.
我国季节性冻土区公路路基冻害及其防治研究进展 总被引：8，自引：4，他引：4
近年来,季节性冻土区公路路基冻害研究已取得了长足的进步,但是,因受气候、环境、冻融循环等不同因素的影响,季节性冻土区公路路基冻害问题依然突出.随着国家公路规划网的逐步实施,将有更多的公路工程向季节性冻土区推进,为了将已有的研究成果更好地应用于工程实践,需对其进行综合评述.基于前期的研究基础,总结我国季节性冻土区公路路基冻害的主要破坏形式及分布区域,讨论影响路基冻害的几个主要因素,分析和总结已有公路路基冻害防治措施的研究现状,提出季节性冻土区公路工程面临的问题和研究建议,为深化季节性冻土区公路路基冻害及其防治研究提供新思路. 相似文献
17.
The response of a multi-layered coastal aquifer in southeast Australia to decades of groundwater pumping, and the groundwater age, flow paths and salinization processes were examined using isotopic tracers. Groundwater radiocarbon and tritium contents decline with distance and depth away from basin margins; however, in the main zone of pumping, radiocarbon activities are generally homogeneous within a given depth horizon. A lack of tritium and low radiocarbon activities (<25 pMC) in groundwater in and around the pumping areas indicate that seasonal recovery of water levels is related to capture of old water with low radioisotope activities, rather than arrival of recently recharged water. Mechanisms facilitating seasonal recovery include release of water from low-permeability layers and horizontal transfer of water from undeveloped parts of the basin. Overall stability in seasonally recovered water levels and salinities for the past three decades indicate that the system has reached a dynamic equilibrium with respect to water balance and salinity, following a major change in flow paths and solute distributions after initial development. Groundwater δ18O, δ2H and chloride contents indicate mixing between fresh meteoric-derived groundwater and marine water at the coast, with the most saline groundwater approximating an 80:20 mixture of fresh to oceanic water. 相似文献
18.
Thomas F. Corbet 《Hydrogeology Journal》2000,8(3):310-327
Numerical simulation was used to enhance conceptual understanding of the post-Pleistocene hydrogeology of a layered sequence
of clastic and evaporite sediments. This work is part of an effort to evaluate the suitability of the Waste Isolation Pilot
Plant (WIPP), New Mexico, USA, as a repository for transuranic waste. The numerical model is three-dimensional, extends laterally
to topographic features that form the actual boundaries of a regional groundwater system, and uses a free surface with seepage
face as an upper boundary condition to simulate the effect of change in recharge rate on the position of the water table.
Simulation results suggest that the modern-day flow field is still adjusting to the drying of the climate that has occurred
since the end of the Pleistocene Epoch. A wetter climate at the end of the Pleistocene resulted in a shallow water table,
and patterns of groundwater flow were controlled by the intermediate features of the land-surface topography. As the climate
became drier and the water table declined, groundwater flow began to increasingly reflect the land-surface topography at the
scale of the entire groundwater basin. The modern-day flow pattern has not equilibrated with either the present recharge rate
or the position of the water table.
Received, November 1998/Revised, December 1999/Accepted, January 2000 相似文献
19.
对水文科学的研究现状、主要进展和发展趋势进行了系统深入的总结和分析,其结果表明,社会需求是水文科学发展的根本动力,技术进步是水文科学发展的源泉。水文科学不仅要研究地表水文过程,还要研究各圈层界面上水分和能量交换过程,不仅要研究水在运动转化过程中的物理过程,还要研究水中各种化学成分的化学过程,特别需要加强水在水文循环和运动中生物过程的研究,从而使水文学向生态水文学的方向迈进。目前,生态水文学、全球气候变化影响是水文学研究的热点领域之一。今后除了进一步继续完善和深化水文科学的理论体系,还要不断丰富水文科学的社会服务功能,为经济建设和社会发展提供科技支撑。 相似文献
20.
A thick lens of fresh groundwater exists in a large region of low permeability in the southern Lihue Basin, Kauai, Hawaii,
USA. The conventional conceptual model for groundwater occurrence in Hawaii and other shield-volcano islands does not account
for such a thick freshwater lens. In the conventional conceptual model, the lava-flow accumulations of which most shield volcanoes
are built form large regions of relatively high permeability and thin freshwater lenses. In the southern Lihue Basin, basin-filling
lavas and sediments form a large region of low regional hydraulic conductivity, which, in the moist climate of the basin,
is saturated nearly to the land surface and water tables are hundreds of meters above sea level within a few kilometers from
the coast. Such high water levels in shield-volcano islands were previously thought to exist only under perched or dike-impounded
conditions, but in the southern Lihue Basin, high water levels exist in an apparently dike-free, fully saturated aquifer.
A new conceptual model of groundwater occurrence in shield-volcano islands is needed to explain conditions in the southern
Lihue Basin.
Electronic Publication 相似文献