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1.
Stable isotope values of hydrogen and oxygen from precipitation and ground water samples were compared by using a volumetrically based mixing equation and stable isotope gradient to estimate the season and location of recharge in four basins. Stable isotopes were sampled at 11 precipitation sites of differing elevation during a 2-year period to quantify seasonal stable isotope contributions as a function of elevation. Supplemental stable isotope data collected by the International Atomic Energy Association during a 14-year period were used to reduce annual variability of the mean seasonal stable isotope data. The stable isotope elevation relationships and local precipitation elevation relationships were combined by using a digital elevation model to calculate the total volumetric contribution of water and stable isotope values as a function of elevation within the basins. The results of these precipitation calculations were compared to measured ground water stable isotope values at the major discharge points near the terminus of the basins. Volumetric precipitation contributions to recharge were adjusted to isolate contributing elevations. This procedure provides an improved representation of recharge contributions within the basins over conventional stable isotope methods. Stable isotope values from wells and springs at the terminus of each basin were used to infer the elevations of precipitation important for recharge of the regional ground water flow system. Ancillary climatic, geologic, and stable isotope values were used to further constrain the location where precipitation is entering the ground water flow system. 相似文献
2.
The chloride concentration in Lake Constance, by volume the second largest lake in Europe, has increased by a factor of 2.4
during the past 40 years. Based on a chloride budget for the year 2006, we estimated total chloride imports to the catchment
at 101 kt year−1. Road deicing salts contributed 52%, waste water 23%, farming 11%, soil weathering 9%, precipitation and solid waste incineration
3% to this import. River monitoring programs in Switzerland, Germany, and Austria in 2006 traced an average total chloride
export from the catchment into Lake Constance of almost 70 kt and an export from the lake of 56 kt. About one-third of this
load to the lake originated from the Alpine Rhine catchment (Switzerland), and about 60% from various smaller tributaries
in Austria and Germany. The average annual import of chloride to Lake Constance for the years 1995–2007 was 60 kt, the export
almost 57 kt. This budget is in good agreement with the observed increase in the chloride content of the lake and thus confirms
the appropriateness and quality of the long-term monitoring program conducted by Swiss, German and Austrian laboratories.
For the year 2006, we estimated that about 65% of the chloride spread onto roads for deicing and manure on cultivated land
reached the lake within the year of their application. The missing 35% remained transiently in the soil and groundwater of
the catchment. 相似文献
3.
Yoshihiro Iijima Tsuneo Kawaragi Takehiko Ito Kanat Akshalov Atsushi Tsunekawa Masato Shinoda 《水文研究》2008,22(16):2974-2981
In drylands, water deficit is the primary factor limiting plant growth. In the present study, surface energy balance and plant growth (above‐ground and below‐ground biomass) were measured continuously during the 2002 growing season in semiarid grassland in the northern part of Kazakhstan, Central Asia. Although there was above normal total rainfall during the 2002 growing season (May–November; 244 mm over 183 days), there was a dry period during July and August. Evaporative water was effectively supplied by precipitation and surface soil moisture during the wet season (May and June), during which time above‐ground biomass increased. During the early stages of the dry period, mature plants were likely to tap deeper sources of soil moisture, representing stored snowmelt water. As the soil moisture content decreased during the summer dry period due to the high levels of evapotranspiration and lack of precipitation, the evaporative fraction and above‐ground biomass rapidly decreased, whereas the below‐ground biomass increased. These results suggest that in summer, soil moisture acts to store water, and that soil moisture is essential for plant growth as a direct source of water during the dry period in natural grasslands in the Kazakhstan steppe. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Zongjie Li Jinzhu Ma Lingling Song Juan Gui Jian Xue Baijuan Zhang Wende Gao Zongxing Li 《水文研究》2020,34(12):2810-2822
Here, we studied the isotope characteristics and source contributions of soil water in the permafrost active layer by collecting soil samples in July 2018 in Yangtze River basin. Soil moisture and temperature showed decreasing trends from 0–80 cm, and an increasing trend from 80–100 cm. The value of δ18O and δD first increased and then decreased in the soil profile of 0–100 cm; however, d-excess increased from 0–100 cm. δ18O values became gradually positive from the southwest to northeast of the study area, while d-excess gradually increased from southeast to northwest. The evaporation water line (EL) was δD = 7.56 δ18O + 1.50 (R2 = 0.90, p < 0.01, n = 96). Due to intense solar radiation and evaporation on the Tibetan Plateau, the elevation did not impact the surface soil. The altitude effect of the soil depths of 0–20 cm was not obvious, but the other soil layers had a significant altitude effect. Soil moisture and temperature were closely related to the stable isotopic composition of soil water. The contribution of precipitation to soil water on the sunny slope was 86%, while the contribution of the shady slope was 84%. However, the contribution of ground ice to soil water on sunny slope was 14% and the shady slope was 16%. The contribution of ground ice to soil water increased with increasing altitude on the sunny slope, but the contribution of ground ice to soil water had no obvious trend on the shady slope. 相似文献
5.
The fraction of rain that is annually recharged to ground water is a function of the transient quantities of precipitation (wet vs. dry years) as well as other meteorological and geologic factors, and thus it is very difficult to estimate. In this study, we have used long records (20 to 30 years) of precipitation and spring discharge to reconstruct the transient character of yearly recharge. These data sets were used to calibrate numerical ground water flow models on the less than 3 km(2) scale for four separate perched karstic aquifers in the Judean and Samarian Mountains of Israel. The stratification and karstic character of the local carbonate rock aquifers cause ground water to flow through discrete dissolution channels and to discharge at isolated springs. An innovative, dual-porosity approach was used where a finite-difference solution simulates flow in the rock matrix, while the karstic channels are simulated using computationally simple drains. Perched conditions are also simulated innovatively using MODFLOW by treating the bottom unsaturated layer as if it is saturated, but by assuming zero pressure head throughout the "unsaturated" layer. Best fitting between measured and computed spring hydrograph data has allowed us to develop a set of empirical functions relating measured precipitation to recharge to the aquifer. The generic methodology presented gives insight into the suspected changes in aquifer recharge rates between particularly wet or dry years. 相似文献
6.
Extremely alkaline ground water has been found underneath many shuttered steel mills and slag dumps and has been an impediment to the cleanup and economic redevelopment of these sites because little is known about the geochemistry. A large number of these sites occur in the Lake Calumet region of Chicago, Illinois, where large-scale infilling of the wetlands with steel slag has created an aquifer with pH values as high as 12.8. To understand the geochemistry of the alkaline ground water system, we analyzed samples of ground water and the associated slag and weathering products from four sites. We also considered several potential remediation schemes to lower the pH and toxicity of the water. The principal cause of the alkaline conditions is the weathering of calcium silicates within the slag. The resulting ground water at most of the sites is dominated by Ca2+ and OH- in equilibrium with Ca(OH)2. Where the alkaline ground water discharges in springs, atmospheric CO2 dissolves into the water and thick layers of calcite form. Iron, manganese, and other metals in the metallic portion of the slag have corroded to form more stable low-temperature oxides and sulfides and have not accumulated in large concentrations in the ground water. Calcite precipitated at the springs is rich in a number of heavy metals, suggesting that metals can move through the system as particulate matter. Air sparging appears to be an effective remediation strategy for reducing the toxicity of discharging alkaline water. 相似文献
7.
To try to resolve the conflicts surrounding the influence of salts on frost weathering, chalk cubes were immersed, separately, in solutions of sodium chloride, sodium sulphate, and magnesium sulphate at concentrations of 5·5 per cent and 12·5 per cent, in a mixed solution of sodium chloride and sodium sulphate, and in distilled water. The cubes were subjected to six freeze-thaw cycles with temperatures ranging from either +15 to — 10°C or + 15 to — 30°C. The results confirm that frost weathering can be enhanced by the presence of certain salts, but the degree of enhancement depends both on the concentration and type of salt and on the intensity of the freeze-thaw regime. Some, but not all, of the results can be explained by the phase changes that occur during the freezing of the salt solutions. 相似文献
8.
Quantification of water balance components, under arid conditions, is essential to the development of water management policies. This study demonstrates the application of the mass water balance approach for the assessment of water resources in a typical watershed located in the southwestern region of Saudi Arabia. The water balance approach was used, on an event basis, to express the amount of precipitation for 13 storms over a three year period, as a percentage of other hydrological components such as runoff, evaporation, and recharge. The study indicated that 63 per cent of precipitation is lost through evaporation from the water surface during flooding, and from the upper layers of the soil surface immediately after storms. Another 32 per cent is stored in the form of soil moisture in the unsaturated layers below the effective evaporation depth. Only 3 per cent of the precipitation was transformed into surface runoff; however, 75 per cent of this contributes towards groundwater recharge. This study has illustrated that the mass water balance approach can be used, with reasonable accuracy, to quantify the components of the hydrological processes under arid conditions, where a reliable data base is available. This, in turn, will help in the development of appropriate water management policies for arid regions. 相似文献
9.
Irrigation, urbanization, and drought pose challenges for the sustainable use of ground water in the central Couloir sud rifain, a major agricultural region in north-central Morocco, which includes the cities of Fès and Meknès. The central Couloir is underlain by unconfined and confined carbonate aquifers that have suffered declines in hydraulic head and reductions in spring flow in recent decades. Previous studies have surveyed ground water flow and water quality in wells and springs but have not comprehensively addressed the chemistry of the regional aquifer system. Using graphical techniques and saturation index calculations, we infer that major ion chemistry is controlled (1) in the surficial aquifer by cation exchange, calcite dissolution, mixing with deep ground water, and possibly calcite precipitation and (2) in the confined aquifer and warm springs by calcite dissolution, dolomite dissolution, mixing with water that has dissolved gypsum and halite, and calcite precipitation. Analyses of 2H and 18O indicate that shallow ground water is affected by evaporation during recharge (either of infiltrating precipitation or return flow), whereas deep ground water is sustained by meteoric recharge with little evaporation. Mechanisms of recharge and hydrochemical evolution are broadly consistent with those delineated for similar regional aquifer systems elsewhere in Morocco and in southern Spain. 相似文献
10.
Glaciers are of crucial importance for the livelihood of the local populations, which depend on their meltwater for water and energy supplies. For this reason, seasonal variations of oxygen‐18 of glacial stream water and their sources within a small glacial catchment in south western China were investigated during the wet season. The results showed significant difference of oxygen‐18 existed among meltwater, rainwater, ground water and stream water, and significantly seasonal variation of precipitation occurred during the observed period. The streamflow of Baishui catchment was separated into components of ice‐snowmelt and precipitation using oxygen‐18. As shown by the result of the two‐component mixing model, on average, 53.4% of the runoff came from ice‐snowmelt during the wet season, whereas the remaining 46.6% were contributed by precipitation in the catchment. According to monthly hydrograph, the contribution of snow and glacier meltwater varied from 40.7% to 62.2%, and that of precipitation varied from 37.8% to 59.3% in wet season. Uncertainties for this separation were mainly caused by the variation of tracer concentrations. The roles of glacier and snow meltwater should be noticed in water resource management in those glacial regions in south western China. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
11.
Following recommendations by the 19th Royal Commission on Environmental Pollution, the area, causes and rates of upland soil erosion in England and Wales were investigated between 1997 and 1999. This paper describes the methods and results of the field survey of 1999 in which the extent of eroded ground was determined. 2. The area of degraded soil and the volume of eroded material were both determined from the dimensions of individual erosion features at 399 field sites located on an orthogonal grid across the uplands. Using measurements of individual erosion features, degraded soil extent in upland England and Wales was estimated at almost 25 000 ha, 2·46 per cent of the total upland area surveyed. Half this eroded area was revegetated and no longer subject to continued accelerated soil loss in 1999. The total volume of eroded material was estimated at 0·284 km3. Although deposition of eroded material occurred within 20 per cent of eroded field sites, the total volume of redeposited material was less than 1 per cent of the total volume of eroded soil. 3. Erosion was more extensive on peat soils than on dry, wet mineral or wet peaty mineral soils. In addition, the higher incidence of erosion at high altitudes and on low slopes reinforced the relationship between erosion and areas of peat formation. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
12.
Experiments are described in which chalk cubes were soaked in solutions of either sodium chloride, sodium sulphate, or magnesium sulphate at concentrations of 5·5 per cent and 12·5 per cent, or in a mixed solution of sodium chloride and sodium sulphate or in distilled water. After removal of excess liquid, the cubes were subjected to six freeze–thaw cycles with temperatures ranging from either +15 to ?10°C or +15 to ?30°C. The results confirm that frost weathering can be enhanced by the presence of certain salts, but the extent of weathering was much less than that previously reported for samples frozen totally immersed in the same liquids. Evidence is presented which suggests that salt crystallization is the major weathering process operative when non–immersed samples are frozen but a combination of frost and salt weathering operates when fully immersed samples are frozen. 相似文献
13.
藏南羊卓雍错流域水化学主离子特征及其控制因素 总被引：14，自引：1，他引：13
水化学主离子特征是流域湖泊的一个重要特征,对气候以及河流所经地区的环境具有指示作用.本文对藏南羊卓雍错流域水化学主离子组成特征及其控制因素进行分析,结果显示流域内不同水体(湖水、河水、地下水)之间的主离子组成以及水化学类型差异显著.其中,羊卓雍错的水化学类型为SO24--HCO3--Mg2+-Na+,巴纠错为SO24--Mg2+-Na+,沉错为SO24--Na+-Mg2+-Ca2+,普莫雍错为HCO3--SO24--Mg2+-Ca2+,空姆错为HCO3--SO24--Ca2+;流域河水中主要阴离子为HCO3-和SO24-,Ca2+为绝对优势阳离子;流域地下水化学类型则为HCO3--Ca2+.究其原因,流域水体化学组成主要受岩石风化作用控制;除此,羊卓雍错、巴纠错和沉错水化学组成亦受自身蒸发-结晶作用的影响.就入湖河水而言,羊卓雍错入湖河水整体受碳酸盐岩石风化的影响较大,蒸发岩溶解的影响次之;沉错和空姆错入湖河流(卡鲁雄曲)的蒸发岩来源则略大于碳酸盐岩来源;而硅酸盐对流域内河水的水化学性质影响较小.与入湖河水相比,羊卓雍错和沉错湖水的Mg2+、Na+和SO24-含量较高,而Ca2+和HCO3-含量较低.这应该与湖水蒸发强烈使得湖水中Ca2+和HCO3-析出并沉积到湖底有关.而空姆错由于湖泊面积小、入湖河水流量大,致使其湖水与入湖河水的主离子组成差异不显著. 相似文献
14.
To assess the contribution of accumulated winter precipitation and glacial meltwater to the recharge of deep ground water flow systems in fracture crystalline rocks, measurements of environmental isotope ratios, hydrochemical composition, and in situ parameters of ground water were performed in a deep tunnel. The measurements demonstrate the significance of these ground water recharge components for deep ground water flow systems in fractured granites of a high alpine catchment in the Central Alps, Switzerland. Hydrochemical and in situ parameters, as well as delta(18)O in ground water samples collected in the tunnel, show only small temporal variations. The precipitation record of delta(18)O shows seasonal variations of approximately 14% and a decrease of 0.23% +/- 0.03% per 100 m elevation gain. delta(2)H and delta(18)O in precipitation are well correlated and plot close to the meteoric water line, as well as delta(2)H and delta(18)O in ground water samples, reflecting the meteoric origin of the latter. The depletion of 18O in ground water compared to 18O content in precipitation during the ground water recharge period indicates significant contributions from accumulated depleted winter precipitation to ground water recharge. The hydrochemical composition of the encountered ground water, Na-Ca-HCO3-SO4(-F), reflects an evolution of the ground water along the flowpath through the granite body. Observed tritium concentrations in ground water range from 2.6 to 16.6 TU, with the lowest values associated with a local negative temperature anomaly and anomalous depleted 18O in ground water. This demonstrates the effect of local ground water recharge from meltwater of submodern glacial ice. Such localized recharge from glaciated areas occurs along preferential flowpaths within the granite body that are mainly controlled by observed hydraulic active shear fractures and cataclastic faults. 相似文献
15.
The present study focusses on the analysis of water stable isotopes to contribute to understanding the hydrology of the Lake Urema wetland system in central Mozambique towards conservation management.Lake Urema Wetland is located in the Gorongosa National Park at the southernmost extent of the East African Rift System and is situated entirely within the Urema catchment. Of particular concern to the park’s management is the understanding of hydrological processes as these may trigger transformations of ecosystems, habitat losses and wildlife migrations. Concerns over the Lake Urema wetland’s drying up and the trapping of sediments in the floodplain have been raised for some time by conservationists.Water samples were collected for stable water isotope analyses during the wet and the dry seasons for the period 2006–2010 from springs, boreholes, rivers, and Lake Urema. In addition monthly composite precipitation was collected at two rain gauges.The results show that Lake Urema is maintained throughout the dry season merely from water generated during the wet season. It receives water from wet season precipitation and the runoff generated from this precipitation. The water source areas of the lake are the Gorongosa Mountain and the Barue Basement geomorphological units. Consequently, the source of the sediments which have been trapped into the lake and the floodplain has to be identified in these two catchment areas and urgent action is required to rescue the lake. This water body constitutes a groundwater buffer system which supports a unique wetland landscape. The annual inundations’ processes leading to the recharge-drainage cycle in the floodplain are most sensitive to the deposition of sediments, changing hydraulic gradients, and reducing wet season inflows and increasing drainage rates. 相似文献
16.
~~Properties of soils in Grove Mountains,East Antarctica@李潇丽$Institute of Geology and Geophysics,Chinese Academy of Sciences!Beijing 100029,China
@刘小汉$Institute of Geology and Geophysics,Chinese Academy of Sciences!Beijing 100029,China
@琚 相似文献
17.
The resilience of alpine/subalpine watersheds may be viewed as the resistance of streamflow or stream chemistry to change under varying climatic conditions, which is governed by the relative size (volume) and transit time of surface and subsurface water sources. Here, we use end‐member mixing analysis in Andrews Creek, an alpine stream in Rocky Mountain National Park, Colorado, from water year 1994 to 2015, to explore how the partitioning of water sources and associated hydrologic resilience change in response to climate. Our results indicate that four water sources are significant contributors to Andrews Creek, including snow, rain, soil water, and talus groundwater. Seasonal patterns in source‐water contributions reflected the seasonal hydrologic cycle, which is driven by the accumulation and melting of seasonal snowpack. Flushing of soil water had a large effect on stream chemistry during spring snowmelt, despite making only a small contribution to streamflow volume. Snow had a large influence on stream chemistry as well, contributing large amounts of water with low concentrations of weathering products. Interannual patterns in end‐member contributions reflected responses to drought and wet periods. Moderate and significant correlations exist between annual end‐member contributions and regional‐scale climate indices (the Palmer Drought Severity Index, the Palmer Hydrologic Drought Index, and the Modified Palmer Drought Severity Index). From water year 1994 to 2015, the percent contribution from the talus‐groundwater end member to Andrews Creek increased an average of 0.5% per year (p < 0.0001), whereas the percent contributions from snow plus rain decreased by a similar amount (p = 0.001). Our results show how water and solute sources in alpine environments shift in response to climate variability and highlight the role of talus groundwater and soil water in providing hydrologic resilience to the system. 相似文献
18.
Partial rootzone drying (PRD) means that part of the root system is watered as in full irrigation while the rest is exposed to soil drying. This practice is predicted to influence field hydrological circle. We studied the effect of this practice on soil water distribution, root and trunk sap flow, water consumption of pear trees, and capillary contribution from ground water table and water balance for three months in an irrigated orchard with a shallow ground water table. The irrigation treatments included: (a) conventional flooded irrigation (CFI), (b) fixed partial rootzone drying (FPRD), and (c) alternate partial rootzone drying (APRD). Root and trunk sap flows were monitored using a heat-pulse sap flow meter. The results showed that there were significant differences of soil water content in both sides of rootzone under partial drying. The capillary contribution from ground water table was significantly increased in APRD and FPRD when compared with CFI. More significantly, the total irrigation amount was greatly reduced, by 43.64 and 45.84%, respectively, for APRD and FPRD. The two PRD treatments used more soil-stored water while CFI had more drainage. The root sap flow on the wet side was substantially enhanced as a result of PRD, and was greater than that from same side in CFI. The trunk sap flow in FPRD and APRD was smaller than that in CFI. On average, both APRD and FPRD reduced plant daily water consumption by about 9.96 and 17.97%, respectively, when compared to CFI during the PRD period. Daily root water flow was a significant function of the reference evapotranspiration. The daily trunk water flow was also related to the reference evapotranspiration but the CFI carried more water than APRD and FPRD under the same evaporation demand, suggesting a restriction of transpirational water loss in the PRD trees. CFI needed a higher soil water content to carry the same amount of trunk flow than the PRD trees, suggesting the hydraulic conductance of roots in PRD trees enhanced, and the roots had a greater water uptake capacity than in CFI when the average soil water content in the rootzone was the same. 相似文献
19.
ABSTRACT Theoretically, a small drainage basin may be divided into equal areas of downward flow and upward flow of groundwater. In regions where surface water does not obscure the phenomena produced by groundwater, these areas can be differentiated by mapping springs, seepages, groundwater levels, flowing wells, chemical quality of water, natural vegetation, salt precipitates, quality of crops, soap holes, and moist and dry depressions. Mapping and interpretation of field phenomena have been carried out in a section of the Ghostpine Creek valley in a Prairie environment. The relief is gently rolling, the geology is simple, and the climate is cold, humid, and continental. The area of the “north flow-systems” is apportioned as follows: 26 per cent underlain by downward flow; 42 per cent underlain by a mid-line area; and 32 per cent underlain by upward flow. Noting that groundwater flow is nearly parallel to the water table in the vicinity of the mid-line these results comply with the above-mentioned theory of groundwater flow distribution in small drainage basins. Thus, the method is suggested for: 1. A reconnaissance study of the groundwater regime in certain areas, and 2. Specific problems related to groundwater in a Prairie environment, such as: finding suitable locations for dug-out type water supplies, estimating prospects for slough-draining and irrigation, and explanation of the development of certain soil types. For such purposes, the method appears to be competitive with test drilling. 相似文献
20.
In a tropical rainforest catchment, shallow piezometers respond almost instantaneously to rainfall, but the dominant ground water recharge mechanisms are not well understood. To improve understanding, the downward movement of soil water on a runoff plot was traced using tritiated water injected at 0·20 m below the surface which marks the lower boundary of active subsurface storm flow. The tritium pulse was translated slowly down the profile, apparently dominated by interstitial piston flow on the lines described by Zimmermann's theoretical model. This recharge mechanism accounted for about 35 per cent of rainfall or 50 per cent of throughfall. The pulse's advance may have also been delayed by the upward movement of soil water indicated by the distribution of hydraulic potential under different hydrological conditions. The result was an increase in soil water transit time particularly below 1·0 m. There was also evidence in the tracer profiles for rapid by-pass flow but the volumes concerned could not be quantified in this experiment. 相似文献