Glacier Snow Meltwater Research Articles

Seasonal and spatial variations of water recharging in the Yangtze River using hydrogen and oxygen stable isotopes

Water and material cycles in rivers are controlled by diverse sources of recharge and flow paths, which exhibit spatial and temporal variations in the contributions of water sources and hydrologic processes. To assess the variation of water recharging, the stable isotope abundances of hydrogen and oxygen (δ2H and δ18O) of 152 water samples collected from the Yangtze River mainstream during May (the flat season) and September (the wet season) in 2021 were analyzed. Bayesian modelling was used to calculate the contribution rates of precipitation, glacier snow meltwater, and groundwater. The isotopic compositions of precipitation and the river exhibited comparable seasonal and spatial characteristics. The Bayesian model results showed that the mainstream was governed by precipitation, with a greater contribution of precipitation in the lower reaches during the wet season. Lakes had a larger contribution during the flat season, as evidenced by the greater increase in the magnitude of δ18O values in the mid-lower reaches during this period. The mid-lower reaches of the river had a decreased river evaporation line (REL) slope, which could be owe to lake replenishment. In addition to intensifying the seasonal variations in the contribution ratios of the lakes, the emplacement of the Three Gorges Dam (TGD) reduced the groundwater contribution of the reservoir. This study enhances our understanding of the hydrological and material cycles in the Yangtze River Basin and provides vital baseline knowledge on the contribution of different recharge sources in the mainstream.

Soil water sources and their implications for vegetation restoration in the Three-Rivers Headwater Region during different ablation periods

Abstract. Amid global warming, the timely supplementation of soil water is crucial for the effective restoration and protection of the ecosystem. It is therefore of great importance to understand the temporal and spatial variations of soil water sources. The research collected 2451 samples of soil water, precipitation, river water, ground ice, supra-permafrost water, and glacier snow meltwater in June, August, and September 2020. The goal was to quantify the contribution of various water sources to soil water in the Three-Rivers Headwater Region (China) during different ablation periods. The findings revealed that precipitation, ground ice, and snow meltwater constituted approximately 72 %, 20 %, and 8 % of soil water during the early ablation period. The snow is fully liquefied during the latter part of the ablation period, with precipitation contributing approximately 90 % and 94 % of soil water, respectively. These recharges also varied markedly with altitude and vegetation type. The study identified several influencing factors on soil water sources, including temperature, precipitation, vegetation, evapotranspiration, and the freeze–thaw cycle. However, soil water loss will further exacerbate vegetation degradation and pose a significant threat to the ecological security of the “Chinese Water Tower”. It emphasizes the importance of monitoring soil water, addressing vegetation degradation related to soil water loss, and determining reasonable soil and water conservation and vegetation restoration models.

Contribution of the cryosphere to runoff in “Chinese water tower” based on environmental isotopes

Cryospheric meltwater is an important runoff component and it profoundly influences changes in water resources in the Tibetan Plateau. Significant changes in runoff components occur in the three-river headwater region (TRHR), which is an important part of “Chinese Water Tower” due to climate warming. However, these effects remain unclear owing to the sparse and uneven distribution of monitoring sites and limited field investigations. Quantifying the contribution of cryospheric meltwater to outlet runoff is a key scientific question that needs to be addressed. In this study, we analyzed 907 precipitation, river water, ground ice, supra-permafrost water, and glacier snow meltwater samples collected from October 2019 to September 2020 in the TRHR. The following results were obtained: (1) There was significant spatio-temporal variation in stable isotopes in different waters; (2) The seasonal trends of stable isotopes for different waters, the relationship between each water body and the local meteoric water line (LWML) confirmed that river water was mainly recharged by precipitation, supra-permafrost water, and glacier snow meltwater; (3) Precipitation, supra-permafrost water, and glacier snow meltwater accounted for 52%, 39%, and 9% of river water, respectively, during the ablation period according to the end-member mixing analysis (EMMA); (4) In terms of future runoff components, there will be many challenges due to increasing precipitation and evaporation, decreasing snow cover, glacier retreat, and permafrost degradation. Therefore, it is crucial to establish the “star-machine-ground” observation networks, forecast extreme precipitation and hydrological events, build the “TRHE on the Cloud” platform, and implement systematic hydraulic engineering projects to support the management and utilization of water resources in the TRHR. The findings of environmental isotope analysis provide insights into water resources as well as scientific basis for rational use of water resources in the TRHR.

Study on recharge source and influence mechanism of plant water in the Three-River Headwaters Region, China

This study, based on the stable isotope tracer technique (δ18O and δ2H), focuses on the recharge sources of plant water in the Three-Rivers Headwaters Region in Qinghai province, China. The oxygen and hydrogen isotope signatures of trees and shrubs were more depleted than those of herbs. However, the d-excess pattern was the opposite of the patterns of stable isotopes of oxygen and hydrogen. From the distribution of stable isotope characteristics of water bodies, the direct source of plant water was determined to be soil water, whereas the indirect sources were river water, supra-permafrost water, soil water, precipitation, and ground ice. The contribution proportions of soil water layers between 0 cm and 20 cm and between 40 cm and 60 cm to the plant water were higher than those of other soil water layers for trees. More importantly, the plant water of shrubs was similar to trees in the cold region. The analysis of the indirect recharge sources of plant water revealed that soil water was still the major source of plant water, while glacier snow meltwater, precipitation, and ground ice meltwater are also the main supply sources of plant water. The proportion of supra-permafrost water to plant water was relatively high, mainly because herbs grow in the active layer in the cold region. Therefore, the proportion of plant water recharged by supra-permafrost water and ground ice meltwater was higher than that of other water bodies during the plant growing season.

Critical role of groundwater discharge in sustaining streamflow in a glaciated alpine watershed, northeastern Tibetan Plateau

As the hydrologic buffering capacity of glaciers diminishes on climate warming, groundwater stored in the glaciated alpine watersheds becomes an important source of streamflow, quantifying the groundwater contribution to this streamflow is significant for better predictions of the impact of rapidly disappearing glaciers on regional water resources. However, the role of groundwater in sustaining streams remains unclear. Here, we selected the upper Shule River Basin (USRB) on the northeast Tibetan Plateau (NETP) as a case to address this knowledge gap through a comprehensive study of geochemistry and stable isotopes data, the application of an end member mixing model and the baseflow hydrograph separation program (HYSEP). Our results indicate that even though the potential sources of streamflow exhibited distinct monthly differences during December 2012‐December 2013, the groundwater was the dominant contributor to streamflow generation in the USRB. The groundwater contributed 45% to 100% of the monthly mean streamflow, and the annual mean value of 70%. By contrast, the glacier-snow meltwater and precipitation only contributed 12% and 18% of the annual discharge. The volume contributed by groundwater was calculated as 9.93 × 108 m3, approximately six times higher than the input of the glacier-snow meltwater (i.e., 1.63 × 108 m3). From 1954 to 2018, the volume of the groundwater discharge to the streamflow in the USRB continuously increased from 4.83 × 108 m3/a (65% of total streamflow) in the 1950s to 10.34 × 108 m3/a (71% of total streamflow) in the 2010s, an increase of 2.14 times. The retreating glacier, as well as increasing precipitation and temperature, were determined to be the main reasons for the increase in groundwater discharge to the streamflow. Our findings suggest that groundwater contribution is more important than was previously thought in the glaciated alpine watersheds on the NETP.

Hydrological effects of multiphase water transformation in Three-River Headwaters Region, China

The present study focuses on the influence of multiphase water transformation on the hydrology of the Three-River Headwater Region. Climatic factors, accelerated transformation of water bodies, and changes in runoff patterns were evaluated based on long-term field observations. Subsequently, we estimated that changes in climatic factors have prolonged the ablation period and accelerated warming since 1990. Additionally, the glacier retreat rate during 2001–2013 was accelerated by approximately 16.23% compared with that during 1976–2001, whereas the ratio of snowfall in annual precipitation has decreased by 2.37% since 1990. The beginning of the freezing cycles of lakes along with the complete cycles were delayed. Moreover, snow sublimation significantly increased after 1990. Amplitudes of frost days (number of days with daily minimum temperature below 0°C) during 1991–2019 were eight times higher than those during 1960–1990. Furthermore, the contribution of moisture recycling to precipitation increased by 9.74% from1979 to 1990 to 1991–2019. The variations in actual evaporation increased from −1.257 mm/a during 1980–1990 to 0.865 mm/a during 1991–2017 and the runoff increased by 66.83×108 m3/10a during 1991–2012. July experienced the highest rainfall and runoff. During the multiphase water transformation, the runoff recharge sources changed significantly, thus, changing the historical trend of recharge in the headwaters of rivers only by the glacier snow meltwater by providing a new recharge mode. However, the accelerated multiphase water transformation caused by climate warming increased the challenges in water resource management and flood control in alpine regions.

Geochemical evidence of ions’ sources and influences of meteorological factors on hydrochemistry of glacier snow meltwater in the source region of the Yangtze River

This study discusses the hydrochemical components of glacier snow meltwater using the correlation analysis, factor analysis, enrichment factor, and the Gibbs diagram. Water samples were collected from June to September in 2016 and 2017. The results obtained the monthly changes for anions and cations in Yuzhufeng (YZG) and Jianggudiru Glacier (JGG) were notably, with highest concentration of ions recorded in September. The effect of seasonal variation on the chemical characteristics of glacier snow meltwater was determined by studying the interaction between the glacier snow meltwater and the control source. The change of hydrochemical characteristics and hydrological cycle is positive in cold areas under the climate warming. The hydrochemical characteristics of glacier snow meltwater in study area were mainly contributed by crustal sources such as evaporates and carbonate rocks. Certainly, a small part of human input cannot be ignored. There was a close relationship between temperature and hydrochemical characteristics, and the relationship between meteorological factors and other ions except K+ was not clear. It is concluded that the water chemistry of glacier snow meltwater in the Alpine region is mainly controlled by the temperature factor-led ablation.

Response mode of hydrochemical types of river water to altitude gradient in alpine regions.

The study investigates the hydrochemical type and characteristics of river water in permafrost regions in the Tibetan Plateau by analyzing 532 samples collected from the source region of the Yangtze River. The hydrochemical type of the river water was Cl--Na+-SO42-, and its hydrochemical characteristics were primarily influenced by the soil sources, though the influence of the sea sources and anthropogenic factors could not be ignored. Significant negative correlations were found between temperature and NO3-, SO42-, Mg2+, Ca2+, and between precipitation, relative humidity, and SO42- and Mg2+ in the river water. River water in the higher altitudes of over 5000 m above sea level was mainly recharged from glacier snowmelt water and by the supra-permafrost water and precipitation at the altitudes between 3500 and 5000 m above sea level. The controlled sources of hydrochemical characteristics of glacier snowmelt water were different for different ablation rates in the area with elevations of over 5000 m above sea level. Different hydrochemical types in different ablation rates implied the hydrochemical type was extremely sensitive to ablation periods in areas with elevation of over 5000 m above sea level. However, hydrochemical type was not sensitive to ablation periods from 3500 to 5000 m above sea level. The ionic concentration of glacier snowmelt water was mainly controlled by pollutants in glaciers and snow. Melting rates of glacier snowmelt water also had a certain effect on ionic concentration. Meanwhile, the stability of the hydrochemical type implied river water mainly controlled the hydrochemical type from 3500 to 5000 m above sea level. Hydrochemical type had no effect on elevation in end ablation.

Climate background, relative rate, and runoff effect of multiphase water transformation in Qilian Mountains, the third pole region

Multiphase water transformation has great effects on alpine hydrology, but these effects remain unclear in the third pole region. Taking the Qilian Mountains as an example, the climate background and relative rates of multiphase water transformation were analyzed, and the runoff effect was evaluated based on long-term field observations. There are three climatic aspects driving multiphase water transformation, including lengthening ablation period, accelerative warming after 1990, and larger warming in the cryosphere belt than in the vegetation belt. The accelerative multiphase water transformation was quantified by three facts: the glacier area retreat rate accelerated by 50% after 1990, the percentage of snowfall in precipitation decreased by 7% after 1990, and the contribution from recycling moisture to precipitation increased by 60% from 1961–1990 to 1991–2016. Under the multiphase water transformation, the outlet runoff for three inland rivers increased by 5 × 108 m3/10 a after 1990. This runoff increase was concentrated mainly in the ablation period. For the seasonal runoff pattern, maximum runoff lagged maximum precipitation by one month under increasing glacier snow meltwater and thickening permafrost active layer. Meltwater from the cryosphere is a crucial runoff component in the Qilian Mountains. At present, these multiphase water transformations are accelerating, along with the yearly runoff increase, which will obviously have a profound impact on water resources management and flood control in the third pole region.

Water resources in inland regions of central Asia: Evidence from stable isotope tracing

Complex hydrological processes affect valuable water resources in inland regions across arid central Asia. Historically, this was a critical part of the Silk Road, and it is now named the modern Silk Road Economic Belt. Using the Qilian Mountains and Hexi Corridor in China as a case-study of the inland region, we collected a total of 2311 water samples from the area and performed a comprehensive investigation of the water cycle. Results from stable isotope tracing indicate clear spatial patterns. In the upstream mountainous regions, glacier snow meltwater becomes groundwater at the periglacial belt. Supra-permafrost water develops into river runoff in the permafrost region. There are also frequent exchanges between groundwater and river runoff along the vegetation belt. In the middle/downstream region, river runoff becomes groundwater. Throughout these processes, both river runoff and groundwater are consumed by evapotranspiration, are recycled, and make a substantial contribution to precipitation. Overall, the upstream mountainous region is a critical part of the water resources. The cryosphere belt accounts for 44% of the mountainous region but contributes to about 80% of water resources. Recycling of moisture also plays an important role. During the summer months (May to September) moisture recycling accounted for 24% and 14% of precipitation in upstream and middle/downstream regions, respectively. The findings from the stable isotope tracing provide insights into hydrological processes and can help improve water management in inland regions of Central Asia.

Water isotopes and hydrograph separation in different glacial catchments in the southeast margin of the Tibetan Plateau

AbstractSnow and glaciers are known to be important sources for freshwater; nevertheless, our understanding of the hydrological functioning of glacial catchments remains limited when compared with lower altitude catchments. In this study, a temperate glacial region located in the southeast margin of the Tibetan Plateau is selected to analyse the characteristics of δ18O and δD in different water sources and the contribution of glacier–snow meltwater to streamflow. The results indicate that the δ18O of river water ranges from −16.2‰ to −10.2‰ with a mean of −14.1‰ and that the δD values range from −117.0‰ to −68.0‰ with a mean of −103.1‰. These values are more negative than those of glacier–snow meltwater but less negative than those of precipitation. The d‐excess values are found to decrease from meltwater to river to lake/reservoir water as a result of evaporation. On the basis of hydrograph separation, glacier–snow meltwater accounts for 51.5% of river water in the Baishui catchment in the melting season. In the Yanggong catchment, snow meltwater contributes 47.9% to river water in the premonsoon period, and glacier meltwater contributes only 6.8% in the monsoon period. The uncertainty in hydrograph separation is sensitive to the variation of tracer concentrations of streamflow components. The input of meltwater to a water system varies with local climate and glacier changes. The results confirm that hydrograph separation using water isotopes is valuable for evaluating the recharge sources of rivers, especially in ungauged glacial regions. This study provides insights into the hydrological processes of glacial catchments on the Tibetan Plateau, which is important for water resource management.

Hydrochemistry of waters in snowpacks, lakes and streams of Mt. Dagu, eastern of Tibet Plateau

There is little available information on hydrochemistry of waters from glacial source to downstream of glacierized catchments. Here we examine the water chemistry of the snowpacks, lakes and streams at eight sampling sites within glacial basin in Mt. Dagu, east Tibetan Plateau. An air mass trajectory model, correlation analysis, Gibbs model, Piper diagram and hydrograph separation analysis were utilized to investigate the characteristics and solutes sources of these waters. Generally, the TDS (Total dissolved solids; 7.54, 13.95 and 18.70mg/L for snowpacks, lakes and streams respectively) and concentrations of main chemicals in all samples exhibited downstream trend from snowpacks to streams. Of the cations, Ca2+ appeared with the highest concentration followed by K+ and Na+. Of the anions, HCO3– was most abundant, followed by Cl−, SO42− and NO3−. For snowpack samples, the air masses arriving at the sampling sites were typically prevailing from the western Tibet Plateau, central Asia and the northern Mongolia plateau. The fine particulate matter in the Mt. Dagu snowpacks was most likely transported long range from three arid regions above-mentioned. High concentrations of SO42− and NH4+ in snowpacks, with twice as much NH4+ as SO42−, implying that the soluble part of the finer particles was transported as a form of ammonium sulfate. Rock weathering determined the ion components of the meltwater and the water could be classified as calcium and bicarbonate type based on the Piper diagram. The chemical contributions from glacier-snow meltwater were 20%―131% for lake and 5%―79% for stream, while the runoff contribution to lake varied from 65.4% to 84.9%, and 66.1% to 81.6% for stream. This study suggested that glacier-snow meltwater was the mainly runoff contributor to lake and stream water and that snowpack solutes derived from eolian additions exert a significant influence on lake and stream chemistry.

Temporal and Spatial Variations of Hydrological Processes on the Landscape Zone Scale in an Alpine Cold Region (Mafengou River Basin, China): An Update

This study investigates precipitation, snow, groundwater, glaciers and frozen soil in different landscape zones using isotopic and hydrogeochemical tracers. The aim of this study is to identify temporal and spatial variations, as well as hydrological processes in the alpine cold region. The results show that there was no significant difference in water chemical characteristics of various waterbodies, and no obvious temporal variation, but exhibited spatial variation. In the wet season, various waterbodies are enriched in oxygen δ18O and deuterium δD due to a temperature effect. Precipitation and the temperature decrease during the dry season, which cannot easily be affected by secondary evaporation. The d-excess (deuterium excess) of various waterbodies was greater than 10‰. There are no altitude effects during wet and dry seasons because the recharged water resources are different in the wet and dry seasons. It is influenced by the freezing-thawing process of glacier snow and frozen soil. The river water is recharged by thawed frozen soil water and precipitation in the wet season, but glacier snow meltwater with negative δ18O and δD is less (14–18%). In the dry season, glacier snow meltwater and groundwater are the dominant source of the river water, and thawed frozen soil water is less (10–15%).

The influence from the shrinking cryosphere and strengthening evopotranspiration on hydrologic process in a cold basin, Qilian Mountains

Under a warming climate, the cryosphere shrinking is accelerating and the evopotranspiration is strengthening, which have caused the spatial and temporal changes of water resources and water cycle in inland river basins. With a vast area of 1.0×104km2 and an annual average evopotranspiration of 515mm, the influence from recycling moisture to precipitation and the contribution from cryosphere meltwater to runoff have been quantified in source region of Heihe river basin at the central Qilian Mountains, where 365 glaciers locate within an area of 77.22km2, whiles frozen soil accounts for 80% of the region. Results indicated that frozen soil meltwater and glacier snow meltwater have contributed by 28% and 7%, on average, to the outlet river water in the basin, respectively. It was founded that evaporation and transpiration moisture were responsible for 10% and 17%, on average, of local precipitation, respectively. These findings provide new progresses on isotopic hydrology of cold basin, which will strengthen further understanding on the role of frozen soil meltwater and local moisture recycling in the water cycle for inland river basins.

Contribution from frozen soil meltwater to runoff in an in-land river basin under water scarcity by isotopic tracing in northwestern China

Cryosphere meltwater has been recognized as an important source of local water resources. However, there are few assessments on the contribution from frozen soil meltwater. In this study, we quantify the fraction from frozen soil meltwater and glacier snow meltwater to runoff in Shiyang River, an in-land river basin of northwestern China, where glaciers were disappearing and frozen soil was in degradation. A large number of samples for precipitation, surface water, groundwater, frozen soil meltwater and glacier snow meltwater have been collected and analyzed for their isotopic compositions. Results indicated that runoff was mainly generated from the cryosphere belt, and it was found that frozen soil meltwater was responsible for 20%, on average, of the outlet river water during flood season in the basin. The contribution rates from frozen soil meltwater to the outlet river runoff changed among the seven sub-basins. The results confirmed that frozen soil meltwater has played an important role in runoff of in-land river basins, and evaluating its influence on the hydrological process under a climate warming scenario is of great significance.

Study on the contribution of cryosphere to runoff in the cold alpine basin: A case study of Hulugou River Basin in the Qilian Mountains

Global warming would inevitably lead to the increased glacier–snow meltwater and mountainous discharge. Taking an example the Hulugou River Basin in the Qilian Mountains, this study confirmed the contribution of cryosphere to runoff by means of the isotope hydrograph separation. The hydro-geochemistry and the isotope geochemistry suggested that both the meltwater and rainwater infiltrated into the subsurface and fed into the river runoff of the Hulugou River Basin in the form of springs. The isotopic composition of river water and underground water was close to the Local Meteoric Water Line, and the δ18O and δD ranged among precipitation, glacier–snow meltwater and frozen soil meltwater. The results indicated that 68% of the recharge of the Hulugou River water was the precipitation, thereinto, glacier–snow meltwater and frozen soil meltwater contributing 11% and 21%, respectively. For tributary-1, precipitation accounted for 77% of the total stream runoff, with frozen soil meltwater accounting for 17%, and glacier–snow meltwater only supplied 6%. During the sampling period, the contribution of surface runoff from precipitation was 44% to tributary-2, and glacier–snow meltwater had contributed 42%; only 14% from frozen soil meltwater. For tributary-3, precipitation accounted for 63% of the total runoff, and other 37% originated from the frozen soil meltwater. According to the latest observational data, the glacier–snow meltwater has accounted for 11.36% of the total runoff in the stream outlet, in which the calculation has been verified by hydrograph separation. It is obvious that the contribution of cryosphere has accounted for 1/3 of the outlet runoff in the Hulugou River Basin, which has been an important part of river sources. This study demonstrated that the alpine regions of western China, especially those basins with glaciers, snow and frozen soil, have played a crucial role in regional water resource provision under global warming.

Increasing precipitation and baseflow in Aksu River since the 1950s

The Aksu River is the most important recharge source of the Tarim River in northwest China, representing 73.2% of the total volume to the Tarim River in the dry season. There are three types of recharge: glacier-snow melt water, precipitation, and groundwater. Precipitation and baseflow in the basin play a decisive role. The dynamics of precipitation in the last past 50 years were investigated. The digital filtering method was used to separate baseflow from surface flow. Relationships between precipitation and baseflow were identified by correlation analysis and wavelet analysis. The major findings of this study include: 1) In the past 50 years, step changes of both precipitation and baseflow in the drainage basin occurred, and both precipitation and baseflow performed a significant increase trend since the 1960s. The 1990s was the wettest decade of precipitation, and baseflow in the late 1990s was the wettest. 2) The time scale of the annual precipitation time series in the Aksu River Basin are 3, 6, 12, and 27 years, of which the six-year cycle oscillation is the strongest and a main cycle. Aksu River basin annual precipitation is manifested in the smaller time scales, as the time scale increases, the smaller its role is. 3) The baseflow showed an increasing trend in all seasons, and precipitation exhibits a monotonic increasing trend in summer and autumn, and decreasing trend in spring and winter. 4) The responses of baseflow to precipitation were different by season. Precipitation and baseflow have significant common power in the 4–6 year band from 1980 to 1998, and the baseflow has a 0–3 months lag from precipitation.

Hydrologic processes in the different landscape zones of Mafengou River basin in the alpine cold region during the melting period

Summary Hydrologic processes of glacier, snow, frozen soil, groundwater, surface water and precipitation have always been the common concern of hydrologists. The purpose of this study is to identify the hydrologic processes in different landscape zones, based on the isotopic and hydrochemical analysis of glacier, snow, frozen soil and groundwater. The chemical compositions were characterized by Ca–HCO 3 in the glacier snow zone, Mg–Ca–SO 4 –HCO 3 in the alpine cold desert zone, Ca–Mg–HCO 3 in the marsh meadow zone, Ca–Mg–HCO 3 in the alpine shrub zone, and Na–Ca–SO 4 in the mountain grassland zone. The end-member mixing model was employed for hydrograph separation. The results showed that during the melting period Mafengou River water was recharged by glacier–snow melt water about 34%, thawed frozen soil water in each of the landscape zones about 12%, and groundwater about 54%. This study suggested that Mafengou River water during the melting period was mainly recharged by glacier–snow melt water, groundwater and thawed frozen soil water.