Spatiotemporal variation of stable isotopic composition in precipitation: Post‐condensational effects in a humid area

In the present study, a 2‐year dataset on δ¹⁸O and δ²H in precipitation is used to investigate hydrometeorologic controls on the isotopic compositions in a temperate maritime climate. Data was collected in Denmark along a transect of Six sampling stations across a landscape with a small topographic gradient and predominant westerly winds. Data showed the local meteoric water line for this region is expressed by the equation δ²H = 7.4δ¹⁸O + 5.4‰. A significant trend correlating enriched isotopic values to humidities around 70% during dry season and more depleted isotopic values to humidities around 90% during wet season was derived from the dataset. Temperature was found to only influence the isotopic composition in a secondary way, whereas no significant relationship was obtained for precipitation amount and evapotranspiration. It is suggested that subcloud post‐condensation exchange strongly influences the isotopic composition at the study site. A simple model of evaporation on falling rain was applied with the aim to reproduce observational data and show the potential influence of changing humidity conditions on precipitation compositions. The rather simple model approach did not fully explain the observational data, but it highlights the drastic isotopic changes from a falling raindrop that potentially can occur due to its release into a dryer atmosphere. This study shows that regional conditions and especially humidity can alter the isotopic composition in precipitation substantially even in regions without major topographic and hydrometeorologic gradients.     

Determination of radionuclides in water at uranium mining remediation – a comparison of analytical methods

The corporate purpose of Wismut GmbH is to decommission its former mining holdings and to rehabilitate the landscape and the environment. Sample taking and analysing the value of contaminants are necessary steps for the remediation of waste rock piles, the recycling of contaminated areas, controlled flooding of uranium mines. Main emphasis lies on the determination of heavy metals and radionuclides of natural decay chains of U‐238 and U‐235. Yearly about 60 000…70 000 determinations of radionuclides in waters were done. Facing this high output of determinations it is a permanent task for laboratory and quality management to ask: Are the results of different methods comparable to each other? Is there a preferred analytical technology? Which matrix influences exist? and What about the analytical costs? Answers to these important questions are given in this report. Summarizing our investigations done in the last few years it is possible to say that – by using different analytical methods the results of radionuclides in water samples (surface or groundwater) are comparable, – a not negligible influence of Ra‐223, Ra‐224 and Ra‐228 may exist by using the DIN 38404 C18 method to determine Ra‐226, – a preferred method cannot be defined, – the choice of the analytical method should include analytical questions (the sample matrix, the occurrence of other disturbing radionuclides, the necessary detection limit) and economical questions (costs, other parameters to be determined).     

Constraining water age dynamics in a south-eastern Australian catchment using an age-ranked storage and stable isotope approach

Improving our knowledge of the travel times of water through catchments is critical for the management and protection of water resources and to improve our understanding of fundamental catchment behaviour. In this study we use the age-ranked storage framework StorAge Selection (SAS) to investigate travel times in the Corin catchment, a headwater catchment in the south-east of Australia covered by native Eucalyptus species. Few studies have applied the SAS framework globally and in energy-intensive areas where catchment losses are heavily in favour of evapotranspiration relative to streamflow. A combination of observed and modelled values of oxygen-18 (δ¹⁸O ), the stable isotope in water, are used to constrain storage selection preferences of streamflow and evapotranspiration and the size of the catchment active storage. The highest performing parameter combinations that could reproduce δ¹⁸O in streamflow were dependent on a strong preference for young water in evapotranspiration, and a mixture of weak young and old water preference in streamflow. The mean travel time of streamflow over the study period 2007–2019, weighted by the flow rate, is limited to within a probable range of 2.81–9.77 years. The size of the active storage, a key parameter in the SAS framework, was poorly identified, and in combination with the isotopic inputs into the model, contributed to the uncertainty of the results. We discuss the implications of the results with respect to the study area, as well as within the context of SAS research globally and identify ways to improve the modelling process.     

Intercomparison of soil pore water extraction methods for stable isotope analysis and interpretation of hillslope runoff sources

Intercomparison of soil pore water extraction methods for stable isotope analysis has been a focus of recent studies in relation to plant source waters, which found a wide isotopic variance depending on the extraction method. Few studies have yet explored extraction effects for mobile pore waters that relate to hillslope runoff. This is because it is extremely difficult in natural systems to control the boundary conditions in order to assess and compare impacts of pore water extraction on resulting hillslope flow. With our new semicontrolled experiments on outdoor mini‐hillslopes, we studied mixing and runoff processes by means of stable isotopes of water and quantified relations between pore water extraction methods. We tested the null hypothesis that nondestructive and destructive pore water sampling methods sample the same soil water pool. Three hillslopes were mounted on load cells, filled with loamy sand textured soils from the Landscape Evolution Observatoryat Biosphere 2, equipped with soil moisture and temperature sensors, a bottom outflow, and a surface runoff gauge for isotope sampling. We followed the precipitation isotopic composition over and through the soil profile. One hillslope was instrumented with suction cups, on the second we installed sampling ports for in‐situ soil water vapour measurements, and the third hillslope was sampled destructively for applying the centrifugation and vapour equilibrium methods. All hillslopes were sampled at four depths (0–10, 10–20, 20–30, and 30–40 cm) at three different downslope positions. ²H and ¹⁸O analyses were performed via laser spectroscopy. We found no isotopic differences between rainfall, surface runoff, and bottom outflow. The in situ vapour ports' soil isotope data showed the widest spread over all hillslope positions and depths. Centrifugation's and suction cups' isotope results plotted closest to the local meteoric water line and within the range of hillslope runoff and bottom outflow data. Hillslope position did not influence the soil isotope results. These results suggest caution be used in the field when selecting an extraction technique for matching soil waters to runoff waters. Soil suction lysimeters and centrifugation appeared to be the most appropriate tools in this regard.     

A study of soil water movement combining soil water potential with stable isotopes at two sites of shallow groundwater areas in the North China Plain

In the shallow groundwater areas of the North China Plain (NCP), precipitation infiltration and evapotranspiration in the vertical direction are the main processes of the water cycle, in which the unsaturated zone plays an important role in the transformation process between precipitation and groundwater. In this paper, two typical sites in Cangzhou (CZ) and Hengshui (HS) of Hebei province with shallow water tables were selected to analyse the relationship among precipitation, soil water and groundwater. At each site, precipitation, soil water at depths 10, 20, 30, 50, 70, 100, 150, 200, 300 cm, and groundwater were sampled to analyse the stable isotope compositions of hydrogen and oxygen. The soil water potentials at the corresponding depths were observed. Although the climates at the two sites are similar, there are some differences in the infiltration process, soil water movement and groundwater recharge sources. Evaporation occurred at the upper depths, which led to the decrease of soil potential and the enrichment of heavy isotopes. At the CZ site, precipitation infiltrated with piston mode, and an obvious mixture effect existed during the infiltration process. Preferential flow may exist in the soil above 100 cm depth. However, at the HS site soil water moved in piston mode, and groundwater was mainly recharged by precipitation. When precipitation recharged the groundwater it experienced a strong evaporation effect. The results of the soil water movement mechanism provides the transformation relationship among precipitation, soil water and groundwater in the middle and eastern NCP. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterization of surface and ground water δ18O seasonal variation and its use for estimating groundwater residence times

¹⁸O is an ideal tracer for characterizing hydrological processes because it can be reliably measured in several watershed hydrological compartments. Here, we present multiyear isotopic data, i.e. ¹⁸O variations (δ¹⁸O), for precipitation inputs, surface water and groundwater in the Shingobee River Headwaters Area (SRHA), a well‐instrumented research catchment in north‐central Minnesota. SRHA surface waters exhibit δ¹⁸O seasonal variations similar to those of groundwaters, and seasonal δ¹⁸O variations plotted versus time fit seasonal sine functions. These seasonal δ¹⁸O variations were interpreted to estimate surface water and groundwater mean residence times (MRTs) at sampling locations near topographically closed‐basin lakes. MRT variations of about 1 to 16 years have been estimated over an area covering about 9 km² from the basin boundary to the most downgradient well. Estimated MRT error (±0·3 to ±0·7 years) is small for short MRTs and is much larger (±10 years) for a well with an MRT (16 years) near the limit of the method. Groundwater transit time estimates based on Darcy's law, tritium content, and the seasonal δ¹⁸O amplitude approach appear to be consistent within the limits of each method. The results from this study suggest that use of the δ¹⁸O seasonal variation method to determine MRTs can help assess groundwater recharge areas in small headwaters catchments. Copyright © 2005 John Wiley & Sons, Ltd.     

Seasonality of stable isotope composition of atmospheric water input at the southern slopes of Mt. Kilimanjaro,Tanzania

To understand the moisture regime at the southern slopes of Mt. Kilimanjaro, we analysed the isotopic variability of oxygen (δ¹⁸O) and hydrogen (δD) of rainfall, throughfall, and fog from a total of 2,140 samples collected weekly over 2 years at 9 study sites along an elevation transect ranging from 950 to 3,880 m above sea level. Precipitation in the Kilimanjaro tropical rainforests consists of a combination of rainfall, throughfall, and fog. We defined local meteoric water lines for all 3 precipitation types individually and the overall precipitation, δD_prec = 7.45 (±0.05) × δ¹⁸O_prec + 13.61 (±0.20), n  = 2,140, R ² = .91, p  < .001. We investigated the precipitation‐type‐specific stable isotope composition and analysed the effects of amount, altitude, and temperature. Aggregated annual mean values revealed isotope composition of rainfall as most depleted and fog water as most enriched in heavy isotopes at the highest elevation research site. We found an altitude effect of δ¹⁸O_rain = ?0.11‰ × 100 m^?1, which varied according to precipitation type and season. The relatively weak isotope or altitude gradient may reveal 2 different moisture sources in the research area: (a) local moisture recycling and (b) regional moisture sources. Generally, the seasonality of δ¹⁸O_rain values follows the bimodal rainfall distribution under the influences of south‐ and north‐easterly trade winds. These seasonal patterns of isotopic composition were linked to different regional moisture sources by analysing Hybrid Single Particle Lagrangian Integrated Trajectory backward trajectories. Seasonality of d excess values revealed evidence of enhanced moisture recycling after the onset of the rainy seasons. This comprehensive dataset is essential for further research using stable isotopes as a hydrological tracer of sources of precipitation that contribute to water resources of the Kilimanjaro region.     

淮南采煤沉陷区积水水文地球化学及氢氧稳定同位素特征

以安徽淮南采煤沉陷积水为研究对象,通过样品采集与测试,研究不同沉陷年限及类型积水水文地球化学和氢氧稳定同位素组成特征及影响因素.结果表明：（1）研究区水化学类型主要为Cl-Na、HCO₃·Cl-Na型,沉陷积水中常量离子主要来源于蒸发岩溶解和硅酸盐风化,受蒸发作用和人为活动的影响明显,水化学组成随沉陷时间和类型变化不大.（2）淮南大气降水线方程为：δD=8.85δ¹⁸O+18.73,沉陷区积水氢氧稳定同位素值在淮南大气降水线右下方依次分布并接近降水线,表明沉陷积水主要来源于大气降水.（3）在降水稀释、水体蒸发及地下水补给的作用下,随着沉陷年限的增加,积水中重同位素越来越贫化,同一年限不同类型的积水同位素值变化较小.     

Estimating water fluxes in the critical zone using water stable isotope approaches in the Groundnut and Ferlo basins of Senegal

Sustainable water management in semi-arid agriculture practices requires quantitative knowledge of water fluxes within the soil-vegetation-atmosphere system. Therefore, we used stable-isotope approaches to evaluate evaporation (E_a), transpiration (T_a), and groundwater recharge (R) at sites in Senegal's Groundnut basin and Ferlo Valley pasture region during the pre-monsoon, monsoon, and post-monsoon seasons of 2021. The approaches were based upon (i) the isothermal evaporation model (for quantifying E_a); (ii) water and isotope mass balances (to partition E_a and T_a for groundnut and pasture); and (iii) the piston displacement method (for estimating R). E_a losses derived from the isothermal evaporation model corresponded primarily to Stage II evaporation, and ranged from 0.02 to 0.09 mm d⁻¹ in the Groundnut basin, versus 0.02–0.11 mm d⁻¹ in Ferlo. At the groundnut site, E_a rates ranged from 0.01 to 0.69 mm d⁻¹; T_a was in the range 0.55–2.29 mm d⁻¹; and the T_a/ET_a ratio was 74%–90%. At the pasture site, the ranges were 0.02–0.39 mm d⁻¹ for E_a; 0.9–1.69 mm d⁻¹ for T_a; and 62–90% for T_a/ET_a. The ET_a value derived for the groundnut site via the isotope approach was similar to those from eddy covariance measurements, and also to the results from the previous validated HYDRUS-1D model. However, the HYDRUS-1D model gave a lower T_a/ET_a ratio (23.2%). The computed groundwater recharge for the groundnut site amounted to less than 2% of the local annual precipitation. Recommendations are made regarding protocols for preventing changes to isotopic compositions of water in samples that are collected in remote arid regions, but must be analysed days later. The article ends with suggestions for studies to follow up on evidence that local aquifers are being recharged via preferential pathways.     

Identifying the source of atmospheric moisture over arid deserts using stable isotopes (2H and 18O) in precipitation

Precipitation is a major component of the hydrologic cycle in arid desert areas. To date, however, few studies have been conducted on investigating the isotope characteristics and moisture sources of precipitation in arid desert environments. The Alxa Desert Plateau is a critical arid desert area in North China. This study is the first to analyse the stable isotopic composition of precipitation to identify the sources of atmospheric moisture over this plateau. Our results show that the δD and δ¹⁸O values of precipitation across the plateau change greatly at both daily and monthly timescales, and exhibit seasonal variations. Among the main meteorological parameters, atmospheric temperature is the most predominant factor controlling the isotopic composition and the δD–δ¹⁸O relationship of local precipitation. Analyses of the precipitation isotopes with the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model reveal that (a) the westerly and polar moisture sources are the dominant controls on summer and winter precipitation and (b) the evaporation of local lake water significantly affects winter precipitation even though it only represents a small amount. Based on the isotope data of 2013–2016 precipitation, a local meteoric water line (LMWL) is derived: δD = (8.20 ± 0.22)·δ¹⁸O + (8.15 ± 2.16)‰ for the study site. Compared to the global meteoric water line, the LMWL has a greater slope and lower d‐excess. This can be explained by admixing of atmospheric moisture resulting from the evaporation of local lake water. Based on this LMWL, we are able to trace that groundwater of the Badain Jaran Desert originates from the surrounding mountains with altitudes of <4,000 m. The newly derived LMWL shows that the recharge altitudes of desert groundwater are overestimated on the basis of the previous LMWLs. This study not only provides insights into the hydrological cycle but also offers guidance for water resource management in arid desert areas of China. Additionally, this study provides techniques that can be applied to the analyses of precipitation isotopes in similar arid regions of the world.     

Determination of groundwater discharge rates and water residence time of groundwater‐fed lakes by stable isotopes of water (18O, 2H) and radon (222Rn) mass balances

Lacustrine groundwater discharge (LGD) and the related water residence time are crucial parameters for quantifying lake matter budgets and assessing its vulnerability to contaminant input. Our approach utilizes the stable isotopes of water (δ¹⁸O, δ²H) and the radioisotope radon (²²²Rn) for determining long‐term average and short‐term snapshots in LGD. We conducted isotope balances for the 0.5‐km² Lake Ammelshainer See (Germany) based on measurements of lake isotope inventories and groundwater composition accompanied by good quality and comprehensive long‐term meteorological and isotopic data (precipitation) from nearby monitoring stations. The results from the steady‐state annual isotope balances that rely on only two sampling campaigns are consistent for both δ¹⁸O and δ²H and suggested an overall long‐term average LGD rate that was used to infer the water residence time of the lake. These findings were supported by the good agreement of the simulated LGD‐driven annual cycles of δ¹⁸O and δ²H lake inventories with the observed lake isotope inventories. However, radon mass balances revealed lower values that might be the result of seasonal LGD variability. For obtaining further insights into possible seasonal variability of groundwater–lake interaction, stable water isotope and radon mass balances could be conducted more frequently (e.g., monthly) in order to use the derived groundwater discharge rates as input for time‐variant isotope balances.     

Water isotope characteristics of a flood: Brisbane River,Australia

Flooding associated with tropical storms can cause extreme perturbations in riverine and coastal ecosystems. Measuring isotope variability of tropical storm events can help investigate the impacts of flooding. We measured the water isotope composition (δD and δ¹⁸O) of rain and associated floodwater collected during two storms and subsequent major and minor flooding events in the subtropical coast of eastern Australia. Compared with baseline regional rainfall isotope values of ?15.0 ± 1.9‰ for δD and ?3.3 ± 0.2‰ for δ¹⁸O, floodwater had lower values with ?33.8 ± 2.5‰ δD and ?5.1 ± 0.4‰ δ¹⁸O for the major flood and ?29.4 ± 1.0‰ δD and ?4.6 ± 0.1‰ δ¹⁸O for the minor flood. The low isotope composition of the floodwater was associated with the transport of large quantities of suspended sediments, with sediment loads 30 to 70 times larger than during base flow conditions. Floods carried up to 35% of the annual phosphorus and up to 208% of the currently calculated average annual nitrogen load of the Brisbane River. The dramatic changes caused by a rapid increase in discharge from 2 to 2015 m³ s^?1 over 2 days in the major flood would have major consequences in riverine and coastal ecosystems of the region. These changes could potentially be traced using the isotope composition of the floodwaters. Copyright © 2015 John Wiley & Sons, Ltd.     

A temporal stable isotopic (δ18O, δD,d‐excess) comparison in glacier meltwater streams,Taylor Valley,Antarctica

In this paper, we describe the importance of hyporheic dynamics within Andersen Creek and Von Guerard Stream, Taylor Valley, Antarctica, from the 2010–2011 melt season using natural tracers. Water collection started at flow onset and continued, with weekly hyporheic‐zone sampling. The water δ¹⁸O and δD values were isotopically lighter in the beginning and heavier later in the season. D‐excess measurements were used as an indicator of mixing because an evaporative signature was evident and distinguishable between 2 primary end‐members (glacier meltwater and hyporheic zone). Hyporheic‐zone influence on the channel water was variable with a strong control on streamwater chemistry, except at highest discharges. This work supports previous research indicating that Von Guerard Stream has a large, widespread hyporheic zone that varies in size with time and discharge. Andersen Creek, with a smaller hyporheic zone, displayed hyporheic‐zone solute interaction through the influence from subsurface hypersaline flow. Overall, the evolution of Taylor Valley hyporheic‐zone hydrology is described seasonally. In mid‐December, the hyporheic zone is a dynamic system exchanging with the glacier meltwater in the channel, and with diminishing flow in January, the hyporheic zone drains back into the channel flow also impacting stream chemistry. This work adds new information on the role of hyporheic zone–stream interaction in these glacier meltwater streams.     

A tracer‐based simulation approach to quantify seasonal dynamics of surface‐groundwater interactions in the Pantanal wetland

The Pantanal wetland is one of the least explored regions of South America. It is characterized by an outstanding flora and fauna adapted to a seasonal flood pulse controlled by a dry and a wet season within each year. The resulting inundation covers in average an area of approximately 150 000 km² and is seen as the most important driver for ecological integrity. Evaporation from the large floodplain is supposed to influence the climate of the whole continent. The regional groundwater is connected to the surface water and plays an important role for the characteristic flooding regime by regulating the wetland's water table. The water balance assessment of the wetland and the internal water exchange between surface and groundwater is therefore of high relevance for the conservation of the Pantanal biodiversity. Despite of its importance, water balance studies including groundwater–surface water interactions based on field data are rarely undertaken. This is mainly due to the remoteness and difficulty in accessing this area, which results in lack of data. In our study, we developed a new tracer‐based model to simulate the spatio–temporal surface and subsurface fluxes for a range of water bodies. The model was able to simulate these fluxes considering a dynamic simulation of inflow and outflow using a newly collected 2‐year dataset of water levels, stable water isotopes and chloride collected from several water bodies in the northern Pantanal region. Quantitative differences between water bodies according to their location in the floodplain were determined by the flooding regime and connectivity as well as site‐specific characteristics, such as hydraulic conductivity and water depth. Our model simulated water balance fluxes with a Nash–Sutcliffe efficiency of 0.61, whereas it simulated stable water isotopic compositions better than chloride. We present the first study based on field data for the Pantanal, which is able to quantify water balances fluxes. Because their representation in global climate and land cover products is insufficient, our simulation results are valuable for validating large‐scale models. Copyright © 2016 John Wiley & Sons, Ltd.     

Factors controlling spatial and seasonal distributions of precipitation δ18O in China

Utilising datasets from the Global Network of Isotopes in Precipitation of the International Atomic Energy Agency, and previous isotopic studies, we investigated δ¹⁸O spatial and temporal patterns in Chinese precipitation. Significantly positive relationships existed between precipitation δ¹⁸O and air temperature above the north of 35°N and in high altitude regions above 32°N. Significantly negative relationships between precipitation δ¹⁸O and the precipitation amount existed below south of 35°N. These temperature and precipitation effects became stronger with increasing altitude except in high altitude regions between 32°N and 35°N. The NCEP/NCAR reanalysis data from 1980 to 2004 showed that variations in spatial and seasonal wind fields at 700 hpa and total precipitable water from the ground to the top of the atmosphere were correlated with the monthly spatial distribution of precipitation δ¹⁸O. Basing on this relationship, we established quantitative correlations between the mean monthly precipitation δ¹⁸O and both latitude and temperature in different seasons. We found that spatial variations in precipitation δ¹⁸O could be described well using the Bowen–Wilkinson model and second‐order equations developed during the present study only in winter (from December to February). During the rest of the year, patterns were too complex to predict using simple models. The results suggest that it is difficult to demonstrate variations of precipitation δ¹⁸O throughout the year and for all regions of China using a single model. Moreover, the new models for the relationships among precipitation, latitude, and temperature were better able to depict the variations in precipitation δ¹⁸O than the Bowen–Wilkinson model. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimating the criterion for determining water vapour sources of summer precipitation on the northern Tibetan Plateau

According to the precipitation and δ¹⁸O data obtained during the GEWEX Asian Monsoon Experiment–Tibet Intensive Observation Period, based on the knowledge that δ¹⁸O is lower in precipitation formed from ocean air mass vapour than that from local evaporation vapour, the water vapour sources can be identified from the δ¹⁸O values in precipitation. We attempt to give the identification criterion of δ¹⁸O values in precipitation. The threshold values chosen to distinguish between ocean and local sources are δ¹⁸O < ?20‰ and δ¹⁸O > ?13‰ respectively. According to this criterion, the proportion of local evaporation‐formed precipitation and ocean air‐mass‐formed precipitation in total precipitation was estimated. The average value of precipitation at three sites (NODA, Amdo and AQB) is 249·76 mm. Among this, precipitation formed directly by the ocean air mass vapour is 80·08 mm at most. Precipitation formed by water vapour evaporated from local places is 117·05 mm at least. That is to say that precipitation formed directly by the ocean air mass vapour accounts for 32·06% of the total precipitation at most. Precipitation formed by water vapour evaporated from local places accounts for 46·86% of the total precipitation at least. At least 21·8% of the total precipitation came from water vapour that was evaporated on the way and transported by the monsoon circulation. Copyright © 2005 John Wiley & Sons, Ltd.     

Water uptake of riparian plants in the lower Lhasa River Basin,South Tibetan Plateau using stable water isotopes

Riparian plants can adapt their water uptake strategies based on climatic and hydrological conditions within a river basin. The response of cold-alpine riparian trees to changes in water availability is poorly understood. The Lhasa River is a representative cold-alpine river in South Tibet and an under-studied environment. Therefore, a 96 km section of the lower Lhasa River was selected for a study on the water-use patterns of riparian plants. Plant water, soil water, groundwater and river water were measured at three sites for δ¹⁸O and δ²H values during the warm-wet and cold-dry periods in 2018. Soil profiles differed in isotope values between seasons and with the distance along the river. During the cold-dry period, the upper parts of the soil profiles were significantly affected by evaporation. During the warm-wet period, the soil profile was influenced by precipitation infiltration in the upper reaches of the study area and by various water sources in the lower reaches. Calculations using the IsoSource model indicated that the mature salix and birch trees (Salix cheilophila Schneid. and Betula platyphylla Suk.) accessed water from multiple sources during the cold-dry period, whereas they sourced more than 70% of their requirement from the upper 60–80 cm of the soil profile during the warm-wet period. The model indicated that the immature rose willow tree (Tamarix ramosissima Ledeb) accessed 66% of its water from the surface soil during the cold-dry period, but used the deeper layers during the warm-wet period. The plant type was not the dominant factor driving water uptake patterns in mature plants. Our findings can contribute to strategies for the sustainable development of cold-alpine riparian ecosystems. It is recommended that reducing plantation density and collocating plants with different rooting depths would be conducive to optimal plant growth in this environment.     

The importance of oxygen isotope provenance in relation to solute content of bulk meltwaters at Imersuaq Glacier,West Greenland

Stable oxygen isotope analysis and measurement of several dissolved cations and anions of bulk meltwater samples have provided information about the hydrochemical environment of the glacial hydrological system at Imersuaq Glacier, an outlet tongue from the Greenland ice‐sheet, West Greenland. The samples were collected at frequent intervals during the period 20–28 July 2000 in a small (<20 L s^?1) englacial meltwater outlet at the glacier margin. The results document the following findings: (i) a marked diurnal variation of δ¹⁸O is related to the composition of oxygen isotope provenances, mainly near‐marginal local superimposed ice and basal up‐sheared ice further up‐glacier; (ii) a relationship is seen between all base cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), SO₄^2? and δ¹⁸O, indicating that solute acquisition is provided by solid–solution contact with the up‐sheared ice—as the relationship with Cl^? is weak the influence of seasalt‐derived solutes is small in the area; (iii) when the melt rate is high, two diurnal maxima of δ¹⁸O values and solute concentrations are measured, and it is suggested that a snow meltwater component is responsible for the second maximum of δ¹⁸O—a short residence time leads to a delayed decrease in ion concentrations. Copyright © 2003 John Wiley & Sons, Ltd.     

Topographical effects on the distributions of rainfall and 18O distributions: a case in Miyake Island,Japan

In this paper, we try to calculate precipitation in Miyake Island, Japan. In order to know the temporal and spatial variations of precipitation, we have set 15 rain gauges randomly in the island to collect the monthly precipitation data since June 1994. It is found that the precipitation is very different from point to point. First, we used statistical methods to get the correlations between the monthly precipitation at our survey points and that at the weather station. Next, regression analyses were used to establish formulae to calculate precipitation as a function of altitude, aspect of the geomorphological surface and wind direction. Based on these results, distributions of monthly and yearly precipitation and δ¹⁸O over the island were assessed. The results show that landscape patterns strongly influence precipitation distribution over the island, with the highest precipitation being found on the windward side, about 400–600 m above sea level. Even at places at the same altitude, the precipitation was different because of the aspect of the landscape. At the same time, altitude effects for δ¹⁸O on both the windward and leeward sides were −0·10‰/100 m and −0·15‰/100 m, respectively. Comparing with the distribution of precipitation distribution, it was also found that δ¹⁸O for the windward and leeward sides was different from that for precipitation, which means that both topographical effects must be considered separately. © 1998 John Wiley & Sons, Ltd.