Tracing the major source area of the mountainous runoff generation of the Heihe River in northwest China using stable isotope technique

Based on the data of δ^18O in precipitation during the period of April 2006 through May 2007 in the upper catchment of the main stream of the Heihe River in the Qilian Mountains, we found that there existed an evident altitude effect on δ^18O in precipitation, and the δ^18O-altitude gradient was -0.18‰/100 m. When δ^18O in river water at the outlet of the mountainous drainage area of the main stream of the Heihe River was combined with the δ^18O-altitude relation, it was realized that the mountainous runoff was generated mostly at high altitudes. Using two component models, we revealed that 80.2% of the annual total mountainous runoff amount was generated at the alpine permafrost-snow-ice zone with an altitude of above 3600 m a.s.I.     

Indian monsoon influences altitude effect of δ~(18)O in precipitation/river water on the Tibetan Plateau

The δ^18O variation in precipitation acquired from 28 stations within the network of Tibetan Observation and Research Platform （TORP） is studied, with the focus on the altitude effect of δ^18O in river water during monsoon precipitation in an effort to understand the monsoon influence on isotopic composition in annual river water. It is found that δ^18O in precipitation on the Plateau is influenced by different moisture sources, with significant Indian monsoon influence on δ^18O composition in plateau precipitation and river water. The δ^18O of water bodies in the monsoon domain is generally more depleted than that in the westerly domain, suggesting gradual rainout of southwesterly borne marine moisture in the course of long-distance transportation and lifting over the Himalayas. The lapse rate of δ^18O in river water with altitude is the largest during monsoon precipitation, due to the increased temperature vertical gradient over the southern Plateau region controlled by monsoon circulation. The combination of δ^18O in river water in monsoon （wet） and non-monsoon （dry） seasons shows a larger lapse rate than that in non-monsoon （dry） season alone. As the altitude effect of δ^18O in precipitation and river water on the Tibetan Plateau results from the combined effect of monsoon moisture supply and westerly moisture supply, the δ^18O composition and its altitude effect on the Plateau during monsoon seasons should be considered in the reconstruction of paleoelevation of the Tibetan Plateau.     

Water isotope variations in the snow pack and summer precipitation at July 1 Glacier, Qilian Mountains in northwest China

This paper presents the stable isotope data of the snow pack and summer precipitation collected at the July 1 Glacier, Qilian Mountains in northwest China and analyses their relationships with meteorologi- cal factors. On an event scale, there is no temperature effect on the δ 18O values in the summer pre- cipitation, whereas the amount effect is shown to be clear. By tracing the moisture transport history and comparing the precipitation with its isotopic composition, it is shown that this amount effect not only reflects the change in moisture trajectory, which is related to the monsoon activities, but is also associated with the cooling degree of vapor in the cloud, the evaporation of falling raindrops and the isotopic exchange between the falling drops and the atmospheric vapor. As very little precipitation occurs in winter, the snow pack profile mainly represents the precipitation in the other three seasons. There are low precipitation δ 18O ratios in summer and high ratios in spring and autumn. The Meteoric Water Line (MLW) for the summer precipitation is δ D = 7.6 δ 18O 13.3, which is similar to that at Delingha, located in the south rim of the Qilian Mountains. The MWL for the snow pack is δ D = 10.4 δ 18O 41.4, showing a large slope and intercept. The deuterium excess (d) of the snow pack is positively correlated with δ 18O, indicating that both d and δ 18O decrease from spring to summer and increase from early autumn to early spring. This then results in the high slope and intercept of the MWL. Sea- sonal fluctuations of d in the snow pack indicate the change of moisture source and trajectory. During spring and autumn, the moisture originates from continental recycling or rapid evaporation over rela- tively warm water bodies like Black, Caspian and Aral Seas when the dry westerly air masses pass over them, hence very high d values in precipitation are formed. During summer, the monsoon is responsi- ble for the low d values. This indicates that the monsoon can reach the western part of the Qilian Mountains.     

Oxygen isotope variation in the water cycle of the Yamzho lake Basin in southern Tibetan Plateau

Given the potential use of stable isotope in the paleoclimate reconstruction from lacustrine records as well as in the local hydrology cycle, it is crucial to understand the processes of stable isotope evolution in catchment in the Tibetan Plateau region. Here we present a detailed study on the water oxygen isotope based on 2 years observation including precipitation, river water and lake water in the Yamzho Lake, south of the Tibetan Plateau. Temporal variation of local precipitation 5180 shows an apparent ＂monsoon cycle＂. In monsoon season, 5180 in waters is lower. In non-monsoon season, δ^18O in precipitation and lake water is higher and higher river δ^18O exists in spring, probably reflecting the effect of land surface evaporation, together with the higher δ^18O values in spring precipitation. It is also found that the surface lake water δ^18O varies seasonally and annually. The lower lake water δ^18O in the late summer is apparently related to the summer monsoon precipitation. The mean δ^18O value of lake water in 2007 is 1.2‰ higher than that in 2004, probably due to the less monsoon precipitation in summer of 2007, as can be confirmed from the precipitation data at the Langkazi meteorological data. It is also found that an obvious shift of vertical lake water δ^18O reflects the fast mixture of lake water. δ^18O values of lake water are over 10‰ higher than those of precipitation and river water in this region due to the evaporation fractionation. The modeled results show that the evaporation process of the lake water is sensitive to relative humidity, and the present lake water δ^18O reflects a relative humidity of 51% in the Yamzho Lake. It shows that the lake will take 30.5 years to reach present lake water δ^18O given a large shift in the input water δ^18O. The modeled results also reveal that surface lake water temperature and inflow δ^18O have slight effect on the isotopic balance process of lake water in the Yamzho Lake.     

Study of altitudinal lapse rates of δ18O in precipitation/river water with seasons on the southeast Tibetan Plateau

Seasonal δ^18O variation in water on the southeast Tibetan Plateau has been studied, showing the consistent variation pattern of δ^18O with altitude indicative of relevant atmospheric circulation processes. Study shows a similar variation pattern of fixed-site river water δ^18O with that of the precipitation δ^18O in southeast Tibet. δ^18O in regional rivers in southeast Tibet demonstrates a gradual depletion with increasing altitude, though the rates vary seasonally. The most depleted river ^18O occurs during the monsoon period, with the lowest δ^18O/altitude lapse rate. The river ^18O during the westerly period is also depleted, together with low δ^18O/altitude lapse rate. The pre-monsoon rivers witness the most enriched ^18O with least significant correlation coefficient with the linear regression, whilst the postmonsoon rivers witness the largest δ^18O/altitude lapse rate. Different coherence of seasonal δ^18O variation with the altitude effect is attributed to different moisture supplies. Though sampling numbers vary with seasons, the δ^18O-H linear correlation coefficients all reach the 0.05 confidence level, thus witnessing the variation features of δ^18O in seasonal river water due to the influence of atmospheric general circulation and land surface processes revealed from the altitudinal lapse rates.     

龙江流域降水、径流时序特征分析

 通过对空间分布于云南沿边地带的龙江流域42a来主要气象站和代表水文站的资料收集,获得各气象站的月降水资料和戛中水文站的月实测天然径流资料.利用数学模型方法,从降水和径流年际变化、年内分配的不均匀性、集中性等方面分析了龙江流域径流的变化规律.得出以下结论:龙江流域降水、径流的年际变化趋势一致,并可能存在一个准8~11a的波动周期(其中径流周期较明显);降水的年内变化较径流变化要显著、剧烈,且降水主要集中在7月,比径流的集中期提前1个月;径流的年内分配主要受降水年内分配影响,但在冬季和春季,受季节特性所决定的流域蓄水和蒸发影响也比较明显.     

Stable isotopic compositions of precipitation events from Kathmandu,southern slope of the Himalayas

Investigation of temporal variations in the stable δ^18O and δD isotopes from Kathmandu＇s precipitation events shows that the relatively enriched δ^18O and δD values in the winter （the dry season, dominated by the westerlies） were positively correlated with temperature, indicating a temperature effect controlling the changes of δ^18O and δD. However, the δ^18O and δD values were depleted in the summer （the wet season, dominated by the Indian monsoon）, which were negatively correlated with precipitation amount, indicating an amount effect. In addition, the comparison of stable isotopes in precipitation from Kathmandu and Mawlong （near the Bay of Bengal） shows that the overall trends of δ^18O and δD values at Kathmandu generally approximate those at Mawlong. However, there remain many differences between the details of the isotopic changes at Kathmandu versus those at Mawlong. Compared with those at Mawlong, the further rainout effect and the more intense lift effect of the oceanic moisture by the high mountains resulted in the more depleted δ^18O and δD values in summer precipitation at Kathmandu. A deuterium excess and the local meteoric water lines reveal that evaporation at Kathmandu exceeds that at Mawlong. The data also show that the Indian monsoon activities at Mawlong are more intense than those at Kathmandu.     

四川若尔盖湿地国家级自然保护区水体氢氧同位素与水化学特征

【目的】了解若尔盖湿地国家级自然保护区水环境特征、水体补给关系,为合理保护和改善湿地水生态环境提供理论参考。【方法】采用液态水/水汽同位素分析仪测定了氢氧稳定同位素丰度,通过离子色谱仪测定八大离子水化学特征指标,对若尔盖湿地国家级自然保护区不同水体(降水、河水、沼泽水、地下水)的化学参数和氢氧稳定同位素[(δ(D)和δ(¹⁸O)]进行分析,研究该区域水化学类型和同位素空间分布特征,探讨了其形成原因和环境意义。【结果】①湖泊水体、黑河及其入沼泽水体、出沼泽水体的主要化学类型都为$HCO_{3}^{-}$-Ca型(重碳酸钙型水);②若尔盖夏季“大气水线”为δ(D) = 8.28 δ(¹⁸O)+13.86,说明受局地水汽、二次蒸发影响小,但蒸发强烈。偏小的δ(¹⁸O)和δ(D)值,反映了雨季受海洋性暖湿气团的影响,降水集中且丰沛,重同位素沿途受雨水冲刷作用较强的特点。HYSPLIT模拟结果证明若尔盖夏季水汽来源于平稳的西风带,受西风环流控制;③降水是其他水体(河水、沼泽水、地下水)最初始的补给来源;河水斜率与沼泽水斜率相近,趋近平行,说明二者的补给关系最为频繁和密切,其中沼泽水接受黑河的支流——果曲、津曲、阿蒙曲、德纳的补给,而黑河的干流与沼泽则是交汇补给。【结论】若尔盖各水体水化学特征主要受流域水岩作用所调控,水体氢氧稳定同位素特征揭示了流域降水、蒸发、大气环流及水文循环过程。     

祁连山北部流域水文相似性与出山径流总量的估计

祁连山北部河流的出山径流对河西走廊水资源的形成具有决定性作用.过去对大型出山河流的水文观测和分析基本确定了祁连山北部的降水产流模式,但由于小型河流缺少观测,对出山径流总量的估计仍然存在很大的不确定性.本文根据疏勒河流域、黑河流域和石羊河流域山区水文观测和气象数据,采用统计模型分析了祁连山北部流域降水-径流关系的相似性.结果表明流域出山流量与汇水面积呈现非线性增加趋势,而蒸散系数随干旱指数增大按照一定的非线性趋势下降.高程效应使得流域出山流量近似取决于平均降水量的单一函数,由此估算出祁连山北部的全部出山流量可达(72.3~84.3)×10~8 m~3·a~(-1),其中石羊河流域、黑河流域的计算结果都大于前人估计值.疏勒河流域的蒸散作用偏强,径流估计值需要进行校正.流域水文相似性有利于减轻水文和气象观测不足造成的影响.     

The mean residence time of river water in the Canada Basin

Seawater was collected from the western Arctic Ocean for measurements of 18О, ^226Ra and ^228Ra. The fractions of river runoff and sea ice melt-water in water samples were estimated by using δ^18О-S-PО^＊ tracer system. The mean residence time of river water in the Canada Basin was calculated based on the relationship between ^228Ra/^226Ra）A.R. and the fractions of river runoff in the shelf and deep ocean. Our results showed that the river runoff fractions in the Canada Basin were significantly higher than those in the shelf regions, suggesting that the Canada Basin is a major storage region for Arctic river water. ^228Ra activity concentrations in the Chukchi shelf and the Beaufort shelf ranged from 0.16 to 1.22 Bq/m^3, lower than those reported for shelves in the low and middle latitudes, indicating the effect of sea ice melt-water. A good positive linear relationship was observed between ^228Ra/^226Ra）A.R. and the fraction of river runoff for shelf waters, while the ^228Ra/^226Ra）A.R. in the Canada Basin was located below this re-gressive line. The low ^228Ra/^226Ra）A.R. in the Canada Basin was ascribed to ^228Ra decay during shelf wa-ters transporting to the deep ocean. The residence time of 5.0-11.0 a was estimated for the river water in the Canada Basin, which determined the time response of surface freshening in the North Atlantic to the river runoff into the Arctic Ocean.     

Simulations of seasonal variations of stable water isotopes in land surface process model CLM

In this study, we simulated and analyzed the monthly variations of stable water isotopes in different reservoirs at Manaus, Brazil, using the Community Land Model （CLM） that incorporates stable isotopic effects as a diagnostic tool for understanding stable water isotopic processes, filling the observational data gaps and predicting hydrometeorological processes. The simulation results show that the δ^18O values in precipitation, vapor and surface runoff have distinct seasonality with the marked negative correlations with corresponding water amount. Compared with the survey results by the International Atomic Energy Agency （IAEA） in co-operation with the World Meteorological Organization （WMO）, the simulations by CLM reveal the similar temporal distributions of the δ^18O in precipitation. Moreover, the simulated amount effect between monthly δ^18O and monthly precipitation amount, and MWL （meteoric water line） are all close to the measured values. However, the simulated seasonal difference in the δ^18O in precipitation is distinctly smaller than observed one, and the simulated temporal distribution of the δ^18O in precipitation displays the ideal bimodal seasonality rather than the observed single one. These mismatches are possibly related to the simulation capacity and the veracity in forcing data.     

The altitude effect of δ 18O in precipitation and river water in the Southern Himalayas

The lapse rate of water isotopes is used in the study of the hydrologic cycle as well as in the estimation of uplift of the Tibetan Plateau.The greater elevation contrast in the Southern Himalayas allows for a detailed discussion about this lapse rate.We analyze variations of 18δO in precipitation and river water between 1320 m and 6700 m elevations in the Southern Himalayas,and calculate the specific lapse rate of water 18δO.The results show that the multi-year average lapse rate in precipitation over this region is 0.15‰/100 m.The one-year average lapse rate is 0.17‰/100 m from three sites along the Southern Himalayas.The two results agree,but are much lower than the global average of 0.28‰/100 m.This work also shows that there is a difference in precipitation 18δO lapse rate between the monsoon and non-monsoon seasons.The calculated precipitation lapse rate is much lower than that in surface water.     

Potential impacts of a warming climate on water availability in snow-dominated regions

All currently available climate models predict a near-surface warming trend under the influence of rising levels of greenhouse gases in the atmosphere. In addition to the direct effects on climate--for example, on the frequency of heatwaves--this increase in surface temperatures has important consequences for the hydrological cycle, particularly in regions where water supply is currently dominated by melting snow or ice. In a warmer world, less winter precipitation falls as snow and the melting of winter snow occurs earlier in spring. Even without any changes in precipitation intensity, both of these effects lead to a shift in peak river runoff to winter and early spring, away from summer and autumn when demand is highest. Where storage capacities are not sufficient, much of the winter runoff will immediately be lost to the oceans. With more than one-sixth of the Earth's population relying on glaciers and seasonal snow packs for their water supply, the consequences of these hydrological changes for future water availability--predicted with high confidence and already diagnosed in some regions--are likely to be severe.     

2000—2015年黑河流域中上游NDVI时空变化及其与气候的关系

选择西北第二大内陆河黑河流域中上游为研究区, 以2000—2015年逐月NDVI数据、月均温和月降水数据、DEM数据和基础地理信息数据为数据源, 采用RS, GIS 和数理统计分析等方法, 从区域尺度和像元尺度揭示区域NDVI时空变化格局及其与气候的关系。结果显示: 1) 2000—2015年, 黑河流域中上游NDVI总体上呈现增长趋势, 其中夏季的增长速率最大, 明显高于春季和秋季; NDVI快速增长区主要位于中游地区黑河干流两侧的绿洲地带; NDVI显著下降区位于张掖市市辖区、酒泉市市辖区以及其他县城所在地; 2) 夏季NDVI与降水相关性较高, 而春、秋季NDVI与气温相关性较高; 夏季NDVI与夏季降水的显著相关性主要体现在远离黑河干流的大片低覆被草地、戈壁以及荒漠, 而邻近黑河的人工绿洲地带NDVI与降水没有显著相关性; 3) NDVI响应降水的时滞效应较明显, 夏季NDVI对降水的响应普遍存在1个月的时间滞后, 最长能滞后2个月。研究结果可以为区域植被恢复和生态系统管理提供参考。     

Isotopic composition of atmospheric water vapor before and after the monsoon’s end in the Nagqu River Basin

Atmospheric water vapor samples were collected in the Nagqu River Basin in the middle of Tibetan Plateau between August and October in 2004. Results show that there exist some fluctuations of the δ^18O of atmospheric water vapor, especially before and after the monsoon＇s end.Moreover, the variety trend of the δ^18O of atmospheric water vapor inverse correlates with that of dew point. Precipitation events make an important effect upon the variation of δ^18O of atmospheric water vapor. During the whole sampling period, the δ^18O values of atmospheric water vapor are low while precipitation events occurred. The moisture origins w also contribute to the variation of δ^18O of atmospheric water vapor. The oceanic moisture transported by the southwest monsoon results in lower δ^18O of atmospheric water vapor in the Nagqu River Basin. Compared with the influence of the oceanic moisture, the δ^18O values, however, appear high resuiting from the effect of the continental air mass in this region.     

黑河流域不同土地利用类型下水体N,P质量浓度特征与动态变化

通过对黑河流域中游地区11年在不同河流断面的长期监测和区域内不同土地利用类型下不同水体,如地下水、泉水、水库水和河流水的空间选点取样分析,来研究干旱区不同土地利用类型下水体N,P等植物营养元素的质量浓度特征与动态变化特征.河水与浅层地下水TP,NH4-N和NO3-N质量浓度均呈沿流域出山口至下游地区显著增加,同时还具有明显的季节变化趋势及随时间递增趋势.不同的土地利用类型对径流中氮素质量浓度有明显的影响,林地面积比例增加使径流水中氮素质量浓度明显减少,而绿洲农田面积成比例增加,氮素变化规律则呈相反趋势.对日趋严重的水体N,P污染问题提出一些建议.     

东北平原西部山前台地区地下水环境同位素分析--以洮儿河流域中上游为例

根据地表水体样品、地下水样品的同位素测试结果,绘制δD δ18O关系图、δ18O H关系图,从而对东北平原西部山前台地区的地下水补迳排关系进行分析·获得该地区雨水线方程δD=7 1781δ18O-8 1151;高程效应关系式δ18O=-0 0049H-8 209;同时认为大兴安岭山区是该区地下水的补给区,补给源是大气降水,区内地下水循环迟缓,主要为1991年以来大气降水补给;地下水形成年龄在3 26～10 6年之间;地下水形成时年平均气温略低于现代年平均气温·     

界河黑龙江重点监测断面水环境状况分析

选取了黑龙江流域黑河及同江两个重点断面,研究了其水环境状况,结果表明,2004—2005年,黑河江段高锰酸盐指数较高,同江江段氨氮浓度较高,地表径流将大量的有机质带入界河黑龙江是河流中高锰酸盐指数超标的主要原因．计算了2001--2005年松花江向界河黑龙江输入的高锰酸盐指数和氨氮年通量的大小,结果显示年通量的大小主要是由流量决定的．     

Summer monsoon and dust signals recorded in the Dasuopu firn core, central Himalayas

In September 1997, a 15-m firn core was recovered from an elevation of 7 000 m a. s.l. from the Dasuopu Glacier in the central Himalayas. The analysis of δ18O values and major ion (Ca2+ , Mg2+ , NH4+ , SO42- and NO3-) concentrations shows that average annual accumulation is 0.75 m (water equivalent) in the Dasuopu firn core. The seasonal variations of δ18O values and major ion concentrations in the core indicate that present summer monsoon and dust signals are recorded with high-resolution in the Dasuopu Glacier. δ18O in precipitation are controlled by amount effect in summer monsoon season, more negative δ18O is representative of summer monsoon signal in snow layers. Higher concentrations of Ca2+ , Mg2+ , SO42- and NO3-are dominated by spring dust storm imput derived from the arid and semi-arid desert regions in central Asia. Also EOF analysis verifies that high spring concentrations of major ions are consistent. Due to the possibly different sources, the secondary variations of NH4+ and NO3- are negatively relevant with that of Ca2+ and Mg2+ .     

Characteristics of δ 18O in precipitation over Eastern Monsoon China and the water vapor sources

Monsoon circulation is an important carrier of water vapor transport, and it impacts the precipitation of the monsoonal regions through the constraints and controls of large-scale water vapor transport and distributions as well as the water vapor balance. An overall research on stable Hydrogen and Oxygen isotopes in precipitation over Eastern Monsoon China could benefit a compre-hensive understanding of the monsoonal precipitation mechanism. Seventeen field stations of the Chinese Network of Isotopes in Precipitation (CHNIP) have been selected to collect monthly composite precipitation samples during the years 2005―2006. Components of δD and δ¹⁸O have been analyzed to achieve the spatiotemporal distributions. The established Local Meteoric Water Line δD=7.46 δ¹⁸O+0.90 based on the 274 obtained monthly samples could be treated as isotope input functions across the region, due to basically reflecting the specific regional meteorological conditions over Eastern Monsoon China. The δ-value de-pleted from coastal to inner area. In Southern China and Northeastern China there were typical periodic patterns of δ¹⁸8O. Differ-ent dominant affecting metrological factors have been raised with different regions. From south to north, the temperature effect of δ¹⁸18O enhanced, while the amount effect changed from existing at an all-year-scale in Southern China to being only remarkable during the main rainy seasons in North China and Northeastern China. Main geographical controls varied from altitude in South-ern China and North China to latitude in Northeastern China. Furthermore, δ¹⁸O had an implication of advance and retreat of the monsoon as well as rainfall belt transfer δ¹⁸O was also a tracer for the movement path of typhoon and tropical storms.