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Asia’s glaciers are a regionally important buffer against drought
Abstract
The high mountains of Asia—encompassing the Himalayas, the Hindu Kush, Karakoram, Pamir Alai, Kunlun Shan, and Tian Shan mountains—have the highest concentration of glaciers globally, and 800 million people depend in part on meltwater from them. Water stress makes this region vulnerable economically and socially to drought, but glaciers are a uniquely drought-resilient source of water. Here I show that these glaciers provide summer meltwater to rivers and aquifers that is sufficient for the basic needs of 136 million people, or most of the annual municipal and industrial needs of Pakistan, Tajikistan, Turkmenistan, Uzbekistan and Kyrgyzstan. During drought summers, meltwater dominates water inputs to the upper Indus and Aral river basins. Uncertainties in mountain precipitation are poorly known, but, given the magnitude of this water supply, predicted glacier loss would add considerably to drought-related water stress. Such additional water stress increases the risk of social instability, conflict and sudden, uncontrolled population migrations triggered by water scarcity, which is already associated with the large and rapidly growing populations and hydro-economies of these basins.
... Rising surface runoff accounted for 42.7% of the total increasing runoff [22]. Pritchard [23] used a combination of CFSR temperature and APHRODITE In XRB, APHRODITE data performed better than WFD data, during both calibration and validation periods [35]. The Tropical Rainfall Measuring Mission (TRMM), National Center for Environmental Prediction (NCEP), Global Precipitation Climatology Project (GPCP), CFSR, and APHRODITE datasets were used to assess the performance of SWAT in the Wunna Basin in India. ...
... In this study, considering the more accurate performance of the CRU TS3.1 and observational datasets than other studied datasets, the simulations of the CRU TS3.1 and observational datasets showed that the actual evapotranspiration in July is almost equal to the July catchment precipitation values. These results are in accordance with those of Pritchard [23], who used a combination of CFSR temperature and APHRODITE precipitation datasets in the SWAT model to simulate water-balance components, especially the actual evapotranspiration in five Asian river basins, including the Aral, Indus, Ganges, Brahmaputra, Tarim, and the lakes of Issyk-Kul and Balkhash. For the Aral Sea Basin in Central Asia, Pritchard reported that summer evaporation is approximately equal to summer precipitation [23]. ...
... These results are in accordance with those of Pritchard [23], who used a combination of CFSR temperature and APHRODITE precipitation datasets in the SWAT model to simulate water-balance components, especially the actual evapotranspiration in five Asian river basins, including the Aral, Indus, Ganges, Brahmaputra, Tarim, and the lakes of Issyk-Kul and Balkhash. For the Aral Sea Basin in Central Asia, Pritchard reported that summer evaporation is approximately equal to summer precipitation [23]. In this study, less actual evapotranspiration occurs in December, January, and February for all datasets studied, including CFSR. ...
In this study, the applicability of three gridded datasets was evaluated (Climatic Research Unit (CRU) Time Series (TS) 3.1, “Asian Precipitation—Highly Resolved Observational Data Integration Toward the Evaluation of Water Resources” (APHRODITE)_V1101, and the climate forecast system reanalysis dataset (CFSR)) in different combinations against observational data for predicting the hydrology of the Upper Vakhsh River Basin (UVRB) in Central Asia. Water balance components were computed, the results calibrated with the SUFI-2 approach using the calibration of soil and water assessment tool models (SWAT–CUP) program, and the performance of the model was evaluated. Streamflow simulation using the SWAT model in the UVRB was more sensitive to five parameters (ALPHA_BF, SOL_BD, CN2, CH_K2, and RCHRG_DP). The simulation for calibration, validation, and overall scales showed an acceptable correlation between the observed and simulated monthly streamflow for all combination datasets. The coefficient of determination (R2) and Nash–Sutcliffe efficiency (NSE) showed “excellent” and “good” values for all datasets. Based on the R2 and NSE from the “excellent” down to “good” datasets, the values were 0.91 and 0.92 using the observational datasets, CRU TS3.1 (0.90 and 0.90), APHRODITE_V1101+CRU TS3.1 (0.74 and 0.76), APHRODITE_V1101+CFSR (0.72 and 0.78), and CFSR (0.67 and 0.74) for the overall scale (1982–2006). The mean annual evapotranspiration values from the UVRB were about 9.93% (APHRODITE_V1101+CFSR), 25.52% (APHRODITE_V1101+CRU TS3.1), 2.9% (CFSR), 21.08% (CRU TS3.1), and 27.28% (observational datasets) of annual precipitation (186.3 mm, 315.7 mm, 72.1 mm, 256.4 mm, and 299.7 mm, out of 1875.9 mm, 1236.9 mm, 2479 mm, 1215.9 mm, and 1098.5 mm). The contributions of the snowmelt to annual runoff were about 81.06% (APHRODITE_V1101+CFSR), 63.12% (APHRODITE_V1101+CRU TS3.1), 82.79% (CFSR), 81.66% (CRU TS3.1), and 67.67% (observational datasets), and the contributions of rain to the annual flow were about 18.94%, 36.88%, 17.21%, 18.34%, and 32.33%, respectively, for the overall scale. We found that gridded climate datasets can be used as an alternative source for hydrological modeling in the Upper Vakhsh River Basin in Central Asia, especially in scarce-observation regions. Water balance components, simulated by the SWAT model, provided a baseline understanding of the hydrological processes through which water management issues can be dealt with in the basin.
... Glacial lake changes are closely associated with climate changes and glacier activities and impact the local hydrologic cycles [1,2]. High Mountain Asia (HMA) develops the most extensive glaciers in the middle and low latitudes [3,4]. In addition to evaporation and flowing into rivers, a fair amount of glacial meltwater is retained in the glacial lakes. ...
... At the same time, the mountainous glacier activities caused by the climate changes are intensifying, such as the rapid retreat of glacier ablation area, glacier surface thinning, and glacier surge [4,53,54]. Glacier changes affect the development and expansion of glacial lakes from several aspects. Glacier surface thinning provides source of water for the glacial lake area expansion, while the rapid retreat of the glacier terminus provides sufficient space for the development of glacial lakes. ...
Changes in a large-scale glacial lake area directly reflect the regional glacier status and climate changes. However, long time series of glacial lake dataset and comprehensive investigation of the spatiotemporal changes in the glacial lake area in the whole High Mountain Asia (HMA) region remained elusive. Satellite remote sensing provides an indispensable way for dynamic monitoring of glacial lakes over large regions. But glacial lakes are quite small and discretely distributed, and the extraction of glacial lakes is usually influenced by clouds, snow/ice cover, and terrain shadows; thus, there is a lack of an automatic method to continuously monitor the dynamic changes of glacial lakes in a large scale. In this paper, we developed a per-pixel composited method named the "multitemporal mean NDWI composite" to automatically extract the glacial lake area in HMA from 1990 to 2020 using time-series Landsat data. There were 19,294 glacial lakes covering a total area of 1471.85 ± 366.42 km2 in 1990, and 22,646 glacial lakes with an area of 1729.08 ± 461.31 km2 in 2020. It is noted that the glacial lake area in the whole HMA region expanded by 0.58 ± 0.21%/a over the past three decades, with high spatiotemporal heterogeneity. The glacial lake area increased at a consistent speed over time. The fastest expansion was in East Kun Lun at an average rate of 2.01 ± 0.54%/a, while in the Pamir and Hengduan Shan, they show slow increases with rates of 0.33 ± 0.08%/a and 0.39 ± 0.01%/a, respectively, during 1990-2020. The greatest increase in lake area occurred at 5000-5200 m a.s.l., which increased by about 45 km2 (~25%). We conclude that the temperature rise and glacier thinning are the leading factors of glacial lake expansion in HMA, and precipitation is the main source of lake water increase in West Kun Lun. Using the proposed method, a large amount of Landsat images from successive years of melting seasons can be fully utilized to obtain a pixel-level composited cloud-free and solid snow/ice-free glacial lake map. The uncertainties from supraglacial ponds and glacial meltwater were also estimated to improve the reliability and comparability of glacial lake area changes among different regions. This study provides important technical and data support for regional climate changes, glacier hydrology, and disaster analysis.
... The Himalayas distribute around 8.6 million cubic meters of water to the downstream regions to maintain the seasonal and yearly flow of these rivers, and therefore, are often referred to as the "Water Tower of Asia" (Dyurgerov and Meier 1997;Singh and Bengtsson 2004;Immerzeel et al. 2010;Bolch et al. 2012). The meltwaters from the Himalayan glaciers provide sustenance to nearly 750 million people and economies of the nearby countries by providing water for several essential purposes like drinking, irrigation, and hydropower generation (Immerzeel et al. 2010;Pritchard 2017). Apart from influencing the hydrological regime, Himalayan glaciers impact the climatic conditions of the Indian subcontinent (Raina and Srivastava 2008). ...
Glacier mass balance is inextricably linked to annual meteorological conditions and is a key indicator for assessing the ice reserves of a glacier. As a result, a number of studies have estimated glacier mass balance using different methods. Here, we have used the improved accumulation area-ratio (IAAR) method to study the mass balance of the Nehnar glacier from 2000 to 2020. This study also aims to study the spatiotemporal behavior and other dynamics of the glacier. Results have shown that the glacier has continuously lost its ice reserves throughout the studied period though at a lower rate since 2010. Its annual specific mass balance has changed from − 50.10 ± 3 cm w.e in 2000 to − 59.46 ± 3 cm w.e. in 2020. The equilibrium line altitude (ELA) of the glacier rose by 90 m and has shifted from 4260 masl in 2000 to 4350 masl in 2020. The glacier has shrunk from an area of 1.64 km² in 2000 to 1.38 km² in 2020 losing nearly 16% of its area. The study highlights the need for continued monitoring of glacier mass balance to better understand and predict the effects of climate change. These findings have important implications for the future of glacier retreat and water reserves of the Jhelum basin.
... Its mountain range is located in the water vapor corridor of the Indian Ocean monsoon, with a westerly circulation, and precipitation is relatively abundant in the mountains [22]. At the same time, the Karakoram Mountains also developed the most intensive mountain glaciers in the Tibetan Plateau and its surrounding regions, and the glacial meltwater produced by them, as an important water resource in the upper reaches of the Indus River, provides sufficient sustenance for the local population and is of great significance for production and life [23]. Scholars' studies of glacier changes in the Karakoram region have found that there is an abnormal mass increase in the Karakoram glaciers [3,[24][25][26], but there is still no clear or consistent understanding of the process of change, the mechanism of occurrence, and Scholars' studies of glacier changes in the Karakoram region have found that there is an abnormal mass increase in the Karakoram glaciers [3,[24][25][26], but there is still no clear or consistent understanding of the process of change, the mechanism of occurrence, and the possible disaster risk. ...
Influenced by global warming, glaciers in High Mountains Asia (HMA) generally show a trend of retreat and thinning, but in Karakoram, Pamir, and West Kunlun there is a trend of glacier stabilization or even a weak advance. In this study, using a bibliometric analysis, we systematically sorted the area, mass balance, and elevation changes of the glaciers in Karakoram and summarized the glacier surges in HMA. The study shows that, since the 1970s, the glaciers in the Karakoram region have experienced a weak positive mass balance, with weakly reducing area and the increasing surface elevation. The north slope of Chogori Peak and the Keltsing River Basin presented a glacier retreat rate with a fast to slow trend. The anomaly is mainly due to low summer temperatures and heavy precipitation in winter and spring in the Karakoram region. There are a large number of surging glaciers in the Karakoram Mountains, the Pamir Plateau, and the West Kunlun region in the western part of HMA, especially in the Karakoram Mountains and the Pamir Plateau, which account for more than 70% of the number of surging glaciers in the entire HMA. The glaciers in the Karakoram and Kunlun Mountains are mainly affected by the synergistic influence of various factors, such as hydrothermal conditions, atmospheric circulation, and topography. However, the glaciers in the Pamir region are mainly influenced by the thermal mechanism of the glacier surge. The glaciers in and around Karakoram are critical to the hydrological response to climate change, and glacial meltwater is an important freshwater resource in arid and semi-arid regions of South and Central Asia, as well as in western China. Therefore, changes in the Karakoram anomaly will remain a hot research topic in the future.
... Water-saving potential (WSP) is a key indicator of irrigation efficiency, and its quantification is crucial for ensuring future freshwater availability and sustainable water resource management in river basins worldwide. Freshwater availability is under significant pressure due to the growing global population and increasing demands for food and energy (Hafeez and Awan 2022;Immerzeel et al. 2020;Pritchard 2017). Future climate changes are anticipated to further exacerbate this situation, intensifying the pressure on available water resources (Huss and Hock 2018;Nepal and Shrestha 2015;Yang et al. 2016). ...
Quantifying water-saving potential (WSP) is crucial for sustainable water resource management in canal command areas and river basins. Previous studies have partially or fully ignored the importance of groundwater in WSP assessments, particularly in irrigated areas. This study is aimed at quantifying WSP in the Lower Chenab Canal (LCC) command area of the Indus River Basin, Pakistan, under various scenarios of future climate change and groundwater recharge. These quantifications are conducted using an empirical model based on the Budyko theory. The model was forced using observed, remote sensing, and CMIP6 future climate data for two Shared Socioeconomic Pathways (SSP245 and SSP585) and their ensembles (cold-dry, cold-wet, warm-dry, and warm-wet) for possible futures. The results showed that the average WSP in the LCC command area was 466 ± 48 mm/year during the historical period (2001–2020). The WSP is projected to decrease by – 68 ± 3% under the warm-dry ensemble scenario (SSP245 and SSP585) and – 48 ± 13% under the ensembled cold-wet scenario by 2100. The results also demonstrated that WSP could be increased by up to 70 ± 9% by artificially recharging 20% of the abstracted groundwater per year in the LCC command area by the late twenty-first century. Our findings highlight the importance of adopting artificial groundwater recharge to enhance the WSP and sustainably manage water resources in the LCC command area. Policymakers should consider these findings when deciding on water resource management in the Indus River Basin.
... These hilly regions consist of glaciers, and several studies report that despite water stress in the area, Asia's glaciers will act as a buffer to drought occurrence in the region. As glacier melt will provide summer water to the regional surface and subsurface water sources, which is sufficient for fulfilling the regional urban population demands (Pritchard, 2017(Pritchard, , 2019. A significant decline was observed in hydrological and soil moisture drought, while meteorological drought increased in the eastern Himalayan cities. Hydrological and Soil moisture drought is declining in all the western Himalayan cities, while the decline is least observed in Srinagar and Jammu, respectively. ...
In 2015 the beginning of the Indian Smart Cities’ mission was one of the significant steps taken by the Indian government to make the urban environment resilient to climate change impact and extreme weather events like drought, floods, heatwaves, etc. This study computes the urban drought risk for Indian smart cities before the beginning of the Indian smart cities mission. This study considers three decadal variability (1982–2013) in meteorological, hydrological, vegetation, and soil moisture parameters for inducing water scarcity and drought conditions in urban regions. Hazards associated with urban drought-inducing parameters variability, vulnerability, and exposure of Indian smart cities were used to compute the Urban drought risk. The research investigations revealed the maximum urban drought risk for Bangalore, Chennai, and Surat cities. Northwest, West Central, and South Peninsular urban regions have higher risk among all the urban regions of India. Indian smart cities mission can be used to make Indian cities resilient to urban drought risk and increase their sustainability. The present research aligned with several national and international agreements by providing an urban drought risk rank for Indian cities, making them less vulnerable to extreme weather events and improving their resilience to climate change.
... Northwest China is among the regions with the most severe water shortages and accounts for approximately 1/4 of the country's total land area (Li et al., 2012;Wang and Qin, 2017). Precipitation is scarce in this region, rivers are mostly recharged seasonally by snowmelt from alpine glaciers, and vegetation is dominated by groundwater-dependent plants in riparian zones (Kraaijenbrink et al., 2017;Pritchard, 2017). ...
Global dryland areas are expanding due to climate change, and this expansion is accompanied by an increased frequency and intensity of drought occurrences. The degree of water stress in drylands is projected to further increase in the future, thereby threatening dryland ecosystem sustainability. Groundwater is among the most important water resources for dryland ecosystems to maintain growth and buffer against drought; thus, it is receiving increasing attention. Although plant-groundwater interactions (PGIs) have been directly observed in academia for 100 years, the mechanisms of their interactions remain unclear due to limited observations. Here, we review the research progress in the indication, intensity and related quantitative methods and mechanism of PGIs, with an emphasis on their divergence at various temporal and spatial scales, and we highlight the controversies or uncertainties that exist. Then, by overviewing the imbalance of plant-groundwater relationships that exist in several typical dryland ecosystems worldwide under climate change and anthropogenic disturbances , we identify the canonical ecological and environmental problems facing drylands both at present and in the future. Finally, we present the main limitations in the study of PGIs in drylands and offer insights into future research priorities. We argue that there are still great difficulties and uncertainties in accurately quantifying the strength of PGIs at present, both in ground monitoring and remote sensing inversion, especially at large scales and high temporal resolutions. While developing physical mechanism-based ecohydrological models is an effective way to address this problem, the current gaps in academia's understanding of the rhizosphere processes of groundwater-dependent plants are among the major constraints. We emphasize the importance of groundwater-dependent plants for dryland ecosystems despite their sparse distribution and that the causes and feedbacks of their changes are not often local but regional.
... High Mountain Asia (HMA) has the greatest extent of glaciers outside the poles (Yao et al. 2007;Yao et al. 2012). The only Hindu Kush Himalayan (HKH) part of the HMA region stores a massive amount of freshwater that feeds millions of people and nurtures the economy in the developing Indian subcontinent and the neighbouring areas (Immerzeel et al. 2010;Frey et al. 2014;Pritchard 2017;Azam et al. 2018). Sikkim Himalayas, where the river Teesta originates, has a tremendous socioeconomic impact on Eastern India's economy and neighbouring Bangladesh. ...
Glacier response patterns at the catchment scale are highly heterogeneous and defined by a complex interplay of various dynamics and surface factors. Previous studies have explained heterogeneous responses in qualitative ways but quantitative assessment is lacking yet where an intrazone homogeneous climate assumption can be valid. Hence, in the current study, the reason for heterogeneous mass balance has been explained in quantitative methods using a multiple linear regression model in the Sikkim Himalayan region. At first, the topographical parameters are selected from previously published studies, then the most significant topographical and geomorphological parameters are selected with backward stepwise subset selection methods. Finally, the contributions of selected parameters are calculated by least square methods. The results show that, the magnitude of mass balance lies between −0.003±0.24 to −1.029±0.24 m.w.e.a−1 between 2000 and 2020 in the Sikkim Himalaya region. Also, the study shows that, out of the terminus type of the glacier, glacier area, debris cover, ice-mixed debris, slope, aspect, mean elevation, and snout elevation of the glaciers, only the terminus type and mean elevation of the glacier are significantly altering the glacier mass balance in the Sikkim Himalayan region. Mathematically, the mass loss is approximately 0.40 m.w.e.a−1 higher in the lake-terminating glaciers compared to the land-terminating glaciers in the same elevation zone. On the other hand, a thousand meters mean elevation drop is associated with 0.179 m.w.e.a−1 of mass loss despite the terminus type of the glaciers. In the current study, the model using the terminus type of the glaciers and the mean elevation of the glaciers explains 76% of fluctuation of mass balance in the Sikkim Himalayan region.
... The automatic procedure adopted in this study provides a basis for the rapid and accurate mapping of the spatial distribution of coniferous forests in the complex terrain. construction of "the Silk Road Economic Belt" and a hot area concerned with the international community [4]. The Tianshan Mountains (TS) is one of the most important parts in the arid area of CA, in which the forest ecosystem has critical ecological values and functions such as carbon sink [5], water resource conservation, flood regulation, water purification, and soil and water conservation. ...
As a distinct species in the Tianshan Mountains (TS) of Central Asia (CA), Picea schrenkiana plays a significant role in water purification, soil and water conservation, and climate regulation. In the context of climate change, rapidly and accurately obtaining its spatial distribution has critical decision-making significance for maintaining ecological security in the arid area of CA and the sustainable development of the “Silk Road Economic Belt”. However, conventional methods are extremely challenging to accomplish the high-resolution mapping of Picea schrenkiana in the TS, which is characterized by a wide range (9.97 × 105 km2) and complex terrain. The approach of geo-big data and cloud computing provides new opportunities to address this issue. Therefore, the purpose of this study is to propose an automatic extraction procedure for the spatial distribution of Picea schrenkiana based on Google Earth Engine and the Jeffries–Matusita (JM) distance, which considered three aspects: sample points, remote-sensing images, and classification features. The results showed that (1) after removing abnormal samples and selecting the summer image, the producer accuracy (PA) of Picea schrenkiana was improved by 2.95% and 0.24%–2.10%, respectively. (2) Both the separation obtained by the JM distance and the analysis results of eight schemes showed that spectral features and texture features played a key role in the mapping of Picea schrenkiana. (3) The JM distance can seize the classification features that are most conducive to the mapping of Picea schrenkiana, and effectively improve the classification accuracy. The PA and user accuracy of Picea schrenkiana were 96.74% and 96.96%, respectively. The overall accuracy was 91.93%, while the Kappa coefficient was 0.89. (4) The results show that Picea schrenkiana is concentrated in the middle TS and scattered in the remaining areas. In total, 85.7%, 66.4%, and 85.9% of Picea schrenkiana were distributed in the range of 1500–2700 m, 20–40°, and on shady slope and semi-shady slope, respectively. The automatic procedure adopted in this study provides a basis for the rapid and accurate mapping of the spatial distribution of coniferous forests in the complex terrain.
... In this article, active strategy aimed at desert utilization is introduced because we found that some plants like Populus are able to adapt to negative environmental changes, and successfully migrate to deserts, as well as continuously expand the distribution. It is very important for 800 million people who live in water scarcity areas of Central Asia supported by very limited meltwater provided by glaciers from the high mountains of Asia-encompassing the Himalayas, the Hindu Kush, Karakoram, Pamir Alai, Kunlunshan and Tianshan Mountains (Pritchard, 2016). ...
Traditionally, plant distribution is thought to be closely related to environmental factors. But recently, it is found that Populus, quite different from other plant taxa, adapted to negative environmental changes, and successfully migrated to different climate zones from its origin places of warm temperate zone. Conversely, Metasequoia is gradually tending to extinction from the Miocene to Quaternary. Based on above contrary cases, two response patterns of plant to negative environmental changes are proposed. One is active adaptation represented by Populus, the other is passive adaptation represented by Metasequoia. The plants of passive strategy characterized for desert prevention might be easily replaced by those of active strategy characterized for desert utilization. Fast growing plants, such as Populus with characteristics of drought and salt tolerance, wind and sand resistance, are selected in Tarim Basin in southern Xinjiang, China, as a good example of desert utilization in the construction of new highways and towns, not only serve as farmland shelterbelt in sandy area. In addition, Populus with high-altitude and cold adaptation has also been selected as an ideal tree planted in Tibet. Therefore, the idea of using Populus as one of the preferred pioneer trees to colonize Mars is proposed.
... The formation of glaciers mainly takes place at high latitudes like the North and South poles and at high altitudes like the Alps, the Andes, and the Himalayas (Scherler et al., 2018). Glaciers in the Himalayas-Karakoram (H-K) region are an important natural resource and serve as a lifeline for more than 800 million people while providing water for potable, agriculture, industries, sanitation, and hydropower purposes (Azam & Srivastava, 2020;Bolch et al., 2012;Pritchard, 2017). A number of 32,292 glaciers are reported for three major river basins, namely, the Indus, the Ganga, and the Brahmaputra (IGB), in the H-K region covering approximately 71,182 sq. ...
The majority of studies discuss the impact of supraglacial debris
on glaciers’ health while the rationale behind the formation and
regional distribution of supraglacial debris in the Himalayan-
Karakoram (H-K) region is sparsely researched. The present
study attempts to evaluate the role of meteorological, topogra-
phical, and geological parameters to understand the regional
distribution and plausible genesis of supraglacial debris in the
H-K area. Glacier-wise Fractional Debris Cover (FDC) for ~5000
glaciers have been estimated using LANDSAT-7 data (1999–
2001) based on the Normalized Difference Snow Index. The
aforementioned parameters, including FDC, are compiled into
a comprehensive database and analysed. Moreover, “2-meter air
temperature” from ERA-5 climatological data is used to estimate
the number of Freeze–Thaw Cycles. Overall meteorological and
topographical parameters show a significant correlation with
the distribution of FDC across the H-K region, more prominently
for glaciers having low FDC (<0.2). FDC distribution shows
a strong dependency on glacier hypsometry with the highest
FDC for “Very Bottom Heavy” glaciers and the lowest for “Very
Top Heavy” glaciers. The glaciers with Limestone bearing lithol-
ogy have maximum FDC and are sparsely distributed, but the
glaciers with quartzite bearing lithology are widely distributed
across the region and have lower FDC.
... Future projections for high-altitude Asian glaciers indicate at least a 50% loss of current ice mass and volume by mid-century as climate change intensifies (Zhao et al. 2014;Rounce et al. 2020). The loss of glacier area and volume across the Himalayan region is of particular concern, since it has both social and environmental implications, with a number of challenges associated with water supplies and future aggravated ecosystem and environmental degradation (Bakke et al. 2016;Pritchard 2017;Higgins et al. 2018;Bolch et al. 2019). ...
In situ experiments were conducted to determine the net ecosystem production (NEP) in cryoconite holes from the surface of two glaciers (Patsio glacier and Chhota Shigri glacier) in the Western Himalaya during the melt season from August to September 2019. The study aimed to gain an insight into the factors controlling microbial activity on glacier surfaces in this region. A wide range of parameters, including sediment thickness, TOC %, TN %, chlorophyll-a concentration, altitudinal position, and grain size of the cryoconite mineral particles were considered as potential controlling factors. From redundancy analysis, the rate of Respiration observed in cryoconite at Chhota Shigri glacier was predominantly explained by sediment thickness in cryoconite holes (37.1% of the total variance, p < 0.05) with Photosynthesis largely explained by the chlorophyll-a content of the sediment (39.6%, p < 0.05). NEP was explained primarily by the TOC content and sediment thickness in cryoconite holes (35.8% and 22.1% respectively, p < 0.05). The altitudinal position of the cryoconite is strongly correlated with biological activity, suggesting that the stability of cryoconite holes was an important factor driving primary productivity and respiration rate on the surface of Chhota Shigri glacier. We calculated that the number of melt seasons required to accumulate organic carbon in thin sediment layers (< 0.3 cm), based on our measured NEP rates, ranged from 11 to 70 years, indicating that the organic carbon in cryoconite holes largely derives from allochthonous inputs, such as elsewhere on the glacier surface. Phototrophic biomass in the same thin sediment layer of cryoconite was estimated to take atleast 4 months to be produced in situ (with mean estimated time upto 1.7 ± 1.5 years). Organic matter accumulated inside the cryoconite holes both through allochthonous deposition and via biological activity on the glacier surface in these areas may have the potential to export dissolved organic matter and associated nutrients to downstream ecosystems. Given the importance of Himalayan glaciers as a vital water source for millions of people downstream, this study highlights the need for further investigation in aspects of the quantification of in situ produced organic matter and its impact on supraglacial melting in the Himalaya.
... The decrease of water resources along with the partially intense agricultural production, which has decreased quantitatively over the last few decades, are exposed to a growing risk with respect to climate change (Perelet 2007). There is increased water stress, especially in Kyrgyzstan and Uzbekistan with its high population (Pritchard 2017) which also influences the socio-economic development and enhances the potential of conflicts about food security (Fischer et al. 2005;Reyer et al. 2017). Hence, it is of utmost importance to improve the spatio-temporal climate variability in climate models for articulating regional adaptation and mitigation strategies considering the expected threats from climate change (Huang et al. 2014). ...
The current study evaluates the regional climate model REMO (v2015) and its new version REMO-iMOVE, including interactive vegetation and plant functional types (PFTs), over two Central Asian domains for the period of 2000-2015 at two different horizontal resolutions (0.44° and 0.11°). Various statistical metrices along with mean bias patterns for precipitation, temperature, and leaf area index have been used for the model evaluation. A better representation of the spatial pattern of precipitation is found at 0.11° resolution over most of Central Asia. Regarding the mean temperature, both model versions show a high level of agreement with the validation data, especially at the higher resolution. This also reduces the biases in maximum and minimum temperature. Generally, REMO-iMOVE shows an improvement regarding the temperature bias but produces a larger precipitation bias compared to the REMO conventional version with interannually static vegetation. Since the coupled version is capable to simulate the mean climate of Central Asia like its parent version, both can be used for impact studies and future projections. However, regarding the new vegetation scheme and its spatiotemporal representation exemplified by the leaf area index, REMO-iMOVE shows a clear advantage over REMO. This better simulation is caused by the implementation of more realistic and interactive vegetation and related atmospheric processes which consequently add value to the regional climate model.
... In the context of global climate change, arid mountain systems, such as the Tianshan Mountains, have experienced significant changes in temperature in recent decades . The Tianshan has extensive snow and glacier (Aizen et al., 1997), where temperature changes affect melting of snow and glaciers (Huang et al., 2022), which in turn affects regional water systems (Du et al., 2022) and construction of "Silk Road Economic Belt" Pritchard, 2017). However, the meteorological stations are few, and observed data are scarce in Tianshan (Fan et al., 2021), where the temperature change mechanism is still unclear. ...
On the alpine areas such as Tianshan Mountains, snow and glaciers are widely distributed, which are sensitive to temperature changes. However, due to high altitude and scarcity of observed stations, the temperature changes and their causes in Tianshan are unclear. To address this issue, this study integrated Thiel-Sen trend test, Pearson correlation, and wavelet analysis methods to analyze the driving factors of temperature changes in Tianshan. We draw the following conclusions: (1) In the past 40 years, Tianshan warmed at a rate of 0.30 °C/decade. Seasonally, the temperature increased the most in spring and summer; spatially, the east Tianshan experienced the most warming. (2) Climate change has affected significant warming in the Tianshan. (3) The large-scale climate teleconnections found to be associated with warming in the Tianshan include North Pacific pattern, Atlantic Multidecadal Variability (AMV), North Atlantic Oscillation, and Western Hemisphere Warm Pool (WHWP). During the study period, the temperature changes lagged AMV and WHWP by 1.5 months, North Tropical Atlantic Index and Tropical Northern Atlantic Index by 3 months, and Arctic Oscillation by 4 months. This research contributes to understanding the response of dry mountains to global warming and atmospheric circulation changes.
... Himalayan glaciers form one of the largest ice concentrations outside the polar regions, with an areal extent of[40,000 km 2 in the entire Himalaya, including Karakoram (Bolch et al. 2012). The meltwater streams that emerge from the Himalayas help to sustain [750 million people and the economy of the surrounding countries by providing water for irrigation, hydropower, drinking, sanitation, and manufacturing (Immerzeel et al. 2010;Pritchard 2017). The Earth's average temperature has increased by 0.6±0.2°C ...
We examined the two neighbouring Raj Bank and Kosa glaciers of the upper Dhauliganga catchment of Uttarakhand, central Himalaya, India, to assess their variability towards climate change. We performed the analysis of multiple satellite images for the period of 1962–2019 and field-based GNSS data obtained during 2018–2019. Length change, area change, debris cover area, and snowline altitude (SLA) were obtained using that. During the last 57 years (1962–2019), the Raj Bank and Kosa glaciers lost 2.43% (0.32 km2 or 0.006 km2 a−1) and 4.54% (0.45 km2 or 0.008 km2 a−1) area; and for the same time span, their frontal retreat was estimated 639.39 m (11.22 m a−1) and 206.71 m (3.69 m a−1), respectively. The study also depicts that from 1968 to 2019, the Raj Bank glacier shows a significant increase in the debris cover area of 4.41%, while in the Kosa glacier, it was 4.08% only. Between 1968 and 2017, the SLA of the Raj Bank and Kosa glaciers shifted on an average by 82 and 71 m upwards, respectively. Loss in glacial area, enhanced debris cover area, and shift in SLA are the indicators of ice volume loss under the present climatic scenario.
... Some areas of the tropical belt of South America are predicted to become drier and more arid as the climate changes. A drier climate means additional dust, a higher likelihood of wildfires, and increased drought periods (Pritchard, 2017). It is important to understand the implications that weather patterns and climatic changes will have on contaminant release within the cryosphere in order to better predict the impact of contaminant release on downstream water resources. ...
Anthropogenic contamination has been detected in glacial and proglacial environments around the globe. Through mechanisms of secondary release, these contaminants are finding their way into glacial hydrological systems and downstream environments, with potential to impact hundreds of millions of people who rely on glacial meltwater for water, food and energy security worldwide. The first part of our progress report outlined the sources and accumulation mechanisms of contaminants in glacial environments (Part I: Inputs and accumulation). Here we assess processes of contaminant release, pathways to downstream environments, and socio-environmental consequences. We reflect on the potential impacts these contaminants could have for human, ecosystem, and environmental health, as well as framing glacial contaminants within the context of the water-food-energy nexus. Improved understanding of these processes and impacts, while crucially embedding local knowledge, will help to develop key policy and mitigation strategies to address future risk of contaminant release from glaciers.
... Pakistan is mainly an agrarian economy that depends heavily on its irrigation water supplies from the Indus River and its tributaries. More than 30% of the hydropower and approximately 95% of the irrigation water demand of Pakistan are fulfilled by the Indus Basin irrigation system (Pritchard, 2017). Thus, major agricultural areas of Pakistan (e.g., Punjab and Sindh provinces) depend on the irrigation water supplies from the source region of the Indus River (SRIR), consisting of the upper Indus River basin (UIRB), Kabul River basin (KRB), and Jhelum River basin (JRB) (Rizwan et al., 2019). ...
Pakistan experiences extreme flood events almost every year during the monsoon season. Recently, flood events have become more disastrous as their frequency and magnitude have increased due to climate change. This situation is further worsened due to the limited capacity of existing water reservoirs and their ability to absorb and mitigate peak floods. Thus, the simulation of stream flows using projected data from climate models is essential to assess flood events and proper water resource management in the country. This study investigates the future floods (in near future and far future periods) using the integrated flood analysis system (IFAS) model under the RCP2.6, RCP4.5, and RCP8.5 climate change scenarios. Downscaled and bias corrected climatic data of six general circulation models and their ensemble were used in this study. The IFAS model simulated the stream flow efficiently (R2 = 0.86–0.93 and Nash–Sutcliffe efficiency = 0.72–0.92) in the Jhelum River basin (JRB), Kabul River basin (KRB), and upper Indus River basin (UIRB) during the calibration and validation periods. The simulation results of the model showed significant impact of projected climate change on stream flows that will cause the mean monthly stream flow in the JRB to be lower, while that of the KRB and UIRB to be higher than that of the historical period. The highest flow months are expected to shift from May–June (Jhelum basin) and June–July (Kabul basin) to April–May with no changes in the UIRB. Higher frequencies of low to medium floods are projected in the KRB and UIRB, while the JRB expects fewer flood events. Based on the results from the IFAS model, it is concluded that stream flow in the study area will increase with several flood events.
... In addition, the formation and melting of glaciers and permafrost produce obvious seasonal differences in the drought situation of the QTP. In summer, the QTP had high temperature, high evaporation, and a large demand for water by vegetation, but its drought degree was less affected by glacier and frozen soil melting than in spring [92]. In winter, the soil of the QTP gradually freezes, the regional evapotranspiration decreases, and the soil water holding capacity increases, making winter the wettest season of the year. ...
The Qinghai–Tibet Plateau (QTP) is a sensor of global climate change and regional human activities, and drought monitoring will help to achieve its ecological protection and sustainable development. In order to effectively control the geospatial scale effect, we divided the study area into eight geomorphological sub-regions, and calculated the Temperature-Vegetation Drought Index (TVDI) of each geomorphological sub-region based on MODIS Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) data, and synthesized the TVDI of the whole region. We employed partial and multiple correlation analyses to identify the relationship between TVDI and temperature and precipitation. The random forest model was further used to study the driving mechanism of TVDI in each geomorphological division. The results of the study were as follows: (1) From 2000 to 2019, the QTP showed a drought trend, with the most significant drought trend in the central region. The spatial pattern of TVDI changes of QTP was consistent with the gradient changes of precipitation and temperature, both showing a gradual trend from southeast to northwest. (2) There was a risk of drought in the four seasons of the QTP, and the seasonal variation of TVDI was significant, which was characterized by being relatively dry in spring and summer and relatively humid in autumn and winter. (3) Drought in the QTP was mainly driven by natural factors, supplemented by human factors. The driving effect of temperature and precipitation factors on TVDI was stable and significant, which mainly determined the spatial distribution and variation of TVDI of the QTP. Geomorphological factors led to regional intensification and local differentiation effects of drought, especially in high mountains, flat slopes, sunny slopes and other places, which had a more significant impact on TVDI. Human activities had local point-like and linear impacts, and grass-land and cultivated land that were closely related to the relatively high impacts on TVDI of human grazing and farming activities. In view of the spatial-temporal patterns of change in TVDI in the study area, it is important to strengthen the monitoring and early warning of changes in natural factors, optimize the spatial distribution of human activities, and scientifically promote ecological protection and restoration.
... At the same time, it would be interesting to explore the intra-annual changes of glacier elevation. Seasonal meltwater from glaciers is a guarantee of water resources in the surrounding and downstream regions of the HMA, in particular in arid and semi-arid regions [28]. Many studies on glacier elevation changes in the HMA region have focused on the inter-annual variability, and studies on monthly/seasonal changes in glacier elevation are still lacking. ...
Glaciers are sensitive indicators of climate change and have a significant influence on regional water cycle, human survival and social development. Global warming has led to great changes in glaciers over the High Mountain Asia (HMA) region. Glacier elevation change is a measure of glacier mass balance driven by the processes of energy and mass exchange between the glacier surface and the atmosphere which are influenced by climatic factors and glacier surface properties. In this study, we estimated the inter-annual and intra-annual elevation changes of glaciers in the HMA region in 2003–2020 using Ice, Cloud and land Elevation Satellite (ICESat) data and Shuttle Radar Terrain Mission (SRTM) digital elevation model (DEM) data by developing an “elevation-aspect bin analysis method” that considered the difference of glacier elevation changes in different elevations and aspects of glacier topography. The results showed that: (1) The inter-annual change of glacier elevation in 2003–2020 had large spatial heterogeneity. Glacier elevation reduction mainly occurred in the marginal region of the HMA with the maximum decline in the Nyainqentanglha region, while glacier elevation showed increase in the West Kunlun of inner HMA regions in 2003–2020. The glacier elevation change rate showed an accelerating reduction trend in most of the HMA regions, except in the west HMA where the glacier elevation reduction rate showed slowdown tendency. Specifically, the glacier elevation change rate in the entire HMA was −0.21 ± 0.12 m/year in 2003–2008 and −0.26 ± 0.11 m/year in 2003–2020, respectively. (2) The intra-annual change of HMA glacier elevation in 2019 and 2020 showed obvious spatiotemporal heterogeneity, and the glacier thickening period was gradually delayed from the marginal area to the inner area of the HMA. The glaciers in the western marginal part of the HMA (the Tienshan Mountains, Pamir and Hindu Kush and Spiti Lahaul) and Karakoram thickened in winter or spring, the glaciers in the Nyainqentanglha Mountains exhibited spring accumulation. The glaciers in West Kunlun accumulated in two time periods, i.e., from March to June and from July to September. The glaciers in the Inner Tibetan Plateau and Bhutan and Nepal areas experienced spring or summer accumulation, especially in June or July. Moreover, we found that the inter-annual and intra-annual change of glacier elevation could be explained by the changes in temperature and precipitation. A similar analysis can be extended to mountain glaciers in other regions of the world, and glacier change trends could be further explored over a longer time span with the continuous operation of ICESat-2.
... Environmental conditions along the ancient Silk Road system contributed to the economic and cultural development in Eurasia since 1 CE 6,[9][10][11][12][13][14][15][16][17][18][19][20][21] . As the gateway from the Mongolian Plateau to Western Asia and Europe (Fig. 1), the Tien Shan Mountains and its surrounding oases played a critical role in nomadic migration into the inner Eurasian steppes 22,23 . The Tien Shan Mountains not only supplied water and pastures for the steppe empires but also enabled trade caravans from East Asia to cross the vast Gobi Desert along the Silk Road system. ...
Understanding changes in water availability is critical for Central Asia; however, long streamflow reconstructions extending beyond
the period of instrumental gauge measurements are largely missing. Here, we present a 785-year-long streamflow reconstruction
from spruce tree rings from the Tien Shan Mountains. Although an absolute causal relationship can not be established, relatively
high streamflow rates coincided roughly with the period of Mongol expansion from 1225 to 1260 CE and the rise of the Timurid
Empire from 1361 to 1400 CE. Since overall wetter conditions were further found during the Zunghar Khanate period 1693–1705
CE, we argue that phases of streamflow surplus likely promoted oasis and grassland productivity, which was an important factor for
the rise of inner Eurasian steppe empires. Moreover, we suggest that the streamflow variation might be critical for plague outbreaks
in Central Asia, and propose several explanations for possible links with Europe’s repeated Black Death pandemics. We demonstrate
that 20th-century low streamflow is unprecedented in the past eight centuries and exacerbated the Aral Sea crisis, which is one of
the most staggering ecological disasters of the twentieth century
... The precipitation variability in Pakistan and neighboring countries has led to water shortage and stress. The contribution of Glaciers in the high mountain region to stabilize the surface water run-off especially during the dry periods has not been well monitored (Pritchard, 2017). Indirectly, the melting glaciers, however, play a significant role to stabilize surface runoff during the droughts Immerzeel et al., 2010;Hussain, 2020;Shoaib, 2019). ...
... By contrast, farmers in north India extract the currently reliable but quickly dwindling static groundwater stored in the thick alluvial aquifers. Additionally, they are also protected by meltwater of the Himalayan glaciers that acts as a buffer to drought stress (including the 2002 mega drought; Pritchard, 2017). These differences are reflected in the predominant rice growing area, characterized by a larger interannual variation in AP (south) than in WB (north; Figure S7 in Supporting Information S1). ...
Characterizing local to regional scale water cycles and water resources will be crucial for achieving the United Nations' water‐related Sustainable Developmental Goals. However, quantification and understanding of groundwater extraction across scales have been hampered by inadequate water usage reporting and limited information on irrigation practices. Here we analyze observations from ∼15,000 groundwater monitoring wells and the Gravity Recovery and Climate Experiment satellites together with irrigation, agricultural, and meteorological datasets to show how drought‐induced coupling between natural and anthropogenic groundwater storage variations has caused sustainability challenges in India, the world's biggest consumer of groundwater for irrigation. Notably, the mechanisms and consequences of such coupling differ significantly depending on aquifer types. In Andhra Pradesh's hard rock aquifer, groundwater declines have been limited, despite the nearly constant water scarcity that its farmers face. Moreover, its free farm power policy involves an annual irrigation energy consumption of 26 billion kWh that costs US$ 2.5 billion, possibly unparalleled compared to any other part of the world of similar size (0.27 million km²). In West Bengal's highly permeable alluvial aquifer, the water table is declining rapidly (15 cm/yr) due to a policy that encourages irrigation. Situated between these two states, Odisha's aquifer shows substantial resilience to drought, owing to the state's relatively natural landscape and forest restoration policy. The findings of this study provide new insights to understand the divergent aspects of groundwater irrigation in north versus south India, which can enable development of adaptation and mitigation strategies to avert the looming water crisis.
... As the source catchment area of many rivers in Central Asia, the Tianshan Mountains incorporate 10,778 glaciers (with an area of approximately 13,567 km 2 ) [1], supplying valuable freshwater resources to oasis agriculture and livestock downstream, and nurturing nearly 50 million people from Kazakhstan, Kyrgyzstan, and China [2]. However, the warming characteristics of the climate in the Tianshan Mountains have been very obvious for more than half a century. ...
Under the influence of climate change, the hydrological processes of glaciers have undergone significant changes, a fact which is seriously affecting agricultural production in the downstream region of the Tianshan Mountains, China. In order to explore the intrinsic relationship between climate change and hydrological elements, we proposed an “evaluation-driving-prediction” system to study it. First, we constructed a glacier-enhanced soil and water assessment tool model (GE-SWAT) and used a two-stage calibration method to optimize the model parameters. Next, a scenario analysis was used to evaluate the driving factors of historical runoff changes. Finally, we projected future runoff changes using bias-corrected regional climate model (RCM) outputs. The results of the case study on the Jinghe River Basin in the Tianshan Mountains show that from 1963 to 2016, total runoff increased by 13.3%, 17.7% of which was due to increasing precipitation and 1.8% of which was negated by rising temperatures. The glacier runoff increased by 14.5%, mainly due to the rising temperatures. A 3.4% reduction in snowmelt was caused by a lower snowfall/precipitation ratio, which significantly reduced the snowfall from June to August. The RCM projection indicated that the warming and humidification phenomenon in the study area will continue at least through to the mid-21st century. A consistent increase in glacier runoff and total runoff is projected, but the contribution rate of the glacier runoff will have little to no change under the RCP4.5 and RCP8.5 emission scenarios. Our research demonstrates the simulation performance of the GE-SWAT model in a basin with moderate glacier cover. This method is shown to be efficient in quantifying the impact of climate change on glacier hydrological processes and predicting future streamflow changes, providing a good research reference for similar regions.
... The precipitation variability in Pakistan and neighboring countries has led to water shortage and stress. The contribution of Glaciers in the high mountain region to stabilize the surface water run-off especially during the dry periods has not been well monitored (Pritchard, 2017). Indirectly, the melting glaciers, however, play a significant role to stabilize surface runoff during the droughts Immerzeel et al., 2010;Hussain, 2020;Shoaib, 2019). ...
Human-induced anthropogenic variations cause a significant change in the local climate, which in turn lead to variations in different climatic regions. The effects of global warming have wide spatial variability, feedback of climate change, like, surface temperature towards precipitation, surface, and subsurface runoff are critical. As the climate, variability is critically important for nature and society, especially if it increases in amplitude and fluctuations become more persistent. However, the issues of weather surface temperature is changing, and if so, whether this has a positive or negative impact on precipitation, surface and ground runoff, and theirs distinguish response to different climate classes, are subjects of ongoing debate. The current research is mainly concerned with distinguishing the response of surface temperature on the precipitation, storm surface run off, and subsurface runoff on different climate classes over the mainland of Pakistan, for a time duration of 71 years, from 1948–2018. Here, we used monthly based two sets of GLDAS (Global Data Assimilation System) datasets i.e. GLDAS-2.0 (1948-2010) and GLDAS-2.1 (2011-2018) having the spatial resolution of 0.25°×0.25° for surface temperature, precipitation, and runoff. While, for regional based climatic classification, Köppen Grignard climate classification map was used. The spatial-temporal trend of all the involving parameters has been estimated using Mann-Kendall’s trend. Spatial-temporal variation in the precipitation, surface temperature, and runoff fluctuations have been detected in different climatic regions. We showed that annually based variability of surface temperature has positive feedback over the surface runoff over the entire region as well as different climate regions of Pakistan. Despite the declining precipitation trend, the temperature seems to be a major cause of the melting of glaciers leading to an increase in the runoff. Based on our findings of established trends and corresponding mechanistic ‘feedback’ we hypothesize that increasing temperature might risk severe water shortage and cause disastrous floods in the future. Furthermore, different climatic zoning’s surface temperature variability contributed to observed variation in the precipitation, surface, and subsurface runoff variability, which in turn contributed to the persistent droughts. Changes in surface temperature and their impact on precipitation and runoff deliver valued evidence for understanding the region’s sensitivity over the entire region in Pakistan.
... The Himalayan terrain, besides having a characteristic tectonic framework (Thakur, 1980), also provides an ideal environment for glacier-related studies (Owen, 2020). With the sustenance of almost 1.4 billion population on the freshwater provided by the Himalayan cryosphere (Pritchard, 2017), assessment of these glaciers becomes crucial for ascertaining their overall status. Therefore, for the future viability of these potential "water towers", it is imperative to understand the past and the present state of the glaciers. ...
Glacier specific studies, in a relatively unexplored terrain of Ladakh, hold immense importance tocomprehend not only the glacier response but also its synchronicity with the general regional trend. Accordingly, in this study, the Kangriz glacier in the Suru sub-basin, western Himalaya, has been taken up for multiparametric (area, terminal retreat, debriscover, snow line altitude, surface dynamics) assessment for the period 1971–2018. Results reveal an overall shrinkage of 3.3 ± 1.6%, with an expansion in the supraglacial debris cover by 45% (1971–2018). Concomitantly, the glacier surface velocity has reduced by 10.85 ± 5.68 ma⁻¹ (35%), from 31.2 ± 5.8 ma⁻¹ (1993/94) to 20.3 ± 1.7 ma⁻¹ (2017/18), with mass wastage of −0.52 ± 0.19 m w.e.a⁻¹ during 2000–17. The notable glacier degeneration is synchronous with regional warming (Tmax increase by 7%, Tmin increase by 43%, Tavg increase by 64%) and a decrease in precipitation by 3% (significant at α <0.05). Besides, frontal dynamics have changed recently, with an enhanced intensity of terminal retreat (2016–2018: 57 ± 13(Stdev) ma⁻¹). The overall glacier status suggests a degenerative pattern of the glacier, which is in sync with the other western Himalayan glaciers. In view of the recently amplified ice-calving events and rapid mass loss observed in the snout region, the frontal glacier morphology may change drastically in the coming years .
... The increasing global warming is contributing to the disappearance of mountain glaciers worldwide, which act as sources of water for mountain areas [11] and those surrounding them. For example, H. D. Pritchard [12] reports that glaciers are essential sources of fresh water in the western river basins of the high-mountain Asia region (Pakistan, Tajikistan, Uzbekistan, Kyrgyzstan, and Xinjiang in northwestern China), particularly during droughts. This is because these regions re-ceive little precipitation during summer when water demand for irrigation is highest. ...
Despite the fact that the Fann Mountains are among the most popular tourist destinations in Tajikistan, they are still in the first stage of tourism development. This represents a great opportunity for the implementation of the principles of sustainable tourism, which will avoid the mistakes associated with the uncontrolled tourism development currently observed in other mountain areas of the world. The aim of this article is to demonstrate, using the example of the Fann Mountains, how hydrogeosites in mountain areas can be valorised for the needs of cognitive tourism. The valorisation methods used in previous research to this point have focused on the evaluation of the objects themselves. This study additionally takes into account features of the surroundings of hydrogeostations, such as the visibility range, the vertical development of the view, and the diversity of the landscape. The conducted value assessments of the sites and their surroundings show that in both internal and external assessments the highest values were achieved by lakes and wetlands. This means that the evaluation of the surroundings has a strong influence on the results obtained and the choice of hydrogeotourism attractions.
... In Asia, with rapid economic and population growth, the increasing water resource demand has led to some regional water shortage crisis (Huntington, 2006;Sivakumar, 2011;Wilson et al., 2017;Liu et al., 2021;Chen et al., 2021;. High Asia (26°~46° N and 62°~105° E) refers to a vast area with the Tibetan Plateau as the centre and extending to the surrounding areas (Pritchard, 2017). Under the influences of the Asian monsoon and westerlies, High Asia usually has a relatively large amount of water resource, which is stored in the form of glaciers, snow and permafrost Mölg et al., 2014;. ...
High Asian glaciers and precipitation have directly or indirectly influenced the freshwater supply of billions of people and natural ecosystems in surrounding areas. To better understand the hydroclimatic changes in the High Asian transboundary river basins in the context of global warming, more precipitation‐sensitive proxy data are needed. In this paper, we used the tree‐ring cores of Pinus densata and Picea brachytyla from the southern Tibetan Plateau (TP) to establish a tree‐ring width composite chronology and estimate hydrological annual (September‐August) precipitation (r2 = 47.0%, P < 0.01) for the Lohit River basin from 1720 to 2019. Our reconstructed precipitation was closely linked with the glacier mass balance of Shishapangma peak, which may provide us with some evidence for glacier fluctuations in the southern TP. Our precipitation reconstruction successfully captured recent dry trends and generally agreed with other tree ring‐based precipitation reconstructions from nearby regions. In addition, reconstructed precipitation variations were inconsistent with recorded monsoon‐season Brahmaputra discharge. This article is protected by copyright. All rights reserved.
... In the past few decades, similar to other permafrost areas, SRYR has experienced more swift warming [62,63]. As a consequence, glacier shrinkage and permafrost degradation are accelerating [64][65][66], and thus, the water environment has undergone profound changes [67,68]. The temperature of permafrost has increased [69], and the soil active layer has deepened [70], resulting in the increase in runoff and DOC concentration in the water body. ...
Rivers as the link between terrestrial ecosystems and oceans have been demonstrated to transport a large amount of dissolved organic carbon (DOC) to downstream ecosystems. In the source region of the Yellow River (SRYR), climate warming has resulted in the rapid retreat of glaciers and permafrost, which has raised discussion on whether DOC production will increase significantly. Here, we present three-year data of DOC concentrations in river water and precipitation, explore the deposition and transport processes of DOC from SRYR. Results show that annual mean concentrations of riverine DOC ranged from 2.03 to 2.34 mg/L, with an average of 2.21 mg/L. Its seasonal variation is characterized by the highest concentration in spring and summer (2.65 mg/L and 2.62 mg/L, respectively), followed by autumn (1.95 mg/L), and the lowest in winter (1.44 mg/L), which is closely related to changes in river runoff under the influence of precipitation and temperature. The average concentration of DOC in precipitation (2.18 mg/L) is comparable with riverine DOC, while the value is inversely related to precipitation amount and is considered to be the result of precipitation dilution. DOC deposition flux in precipitation that is affected by both precipitation amount and DOC concentration roughly was 86,080, 105,804, and 73,072 tons/yr from 2013 to 2015, respectively. DOC flux delivered by the river ranged from 24,629 to 37,539 tons/yr and was dominated by river discharge. Although permafrost degradation in SRYR is increasing, DOC yield is not as significant as previously assumed and is much less than other large rivers in the world.
... Rapid changes in the climate coupled with anthropogenic change (due to land use change or population growth) is impacting such land-atmosphere processes, and in turn streamflow (Immerzeel et al., 2020;Wang et al., 2015;Wang et al., 2019). The snowpack of the Tibetan Plateau (TP) has an important role in the water cycle for prominent Asian basins including the Brahmaputra, Yellow and Yangtze (Bai et al., 2016;Cai et al., 2017;Pritchard, 2017). These rivers serve as prominent sources of fresh water supply and satisfy agricultural, energy and consumption needs for some of the most populated regions of the world (Cuo et al., 2014;Han et al., 2019;Ray et al., 2015). ...
Modelling the impact of climate change on streamflow for remote or data sparse regions is a challenge for hydrologists, as large datasets are often needed to adequately characterise the processes that dominate. The Tibetan Plateau, which forms the headwaters of the Brahmaputra and many other major rivers in the Indo-China region, is not closely monitored due to its harsh environment. This lack of monitoring is significant as regards its substantial snow resources, of considerable importance given the influence these have on the supply of water to downstream communities. This research uses a conceptual hydrologic model developed to simulate the impact of the changing climate in such large, snow-covered, data sparse catchments, to adequately understand the likely changes in future water availability in the highly populated Brahmaputra basin and surrounding areas in the Tibetan Plateau. A multivariate nested recursive bias correction (MRNBC) approach is used for correcting systematic biases present in the climate model simulations of temperature and precipitation jointly across multiple timescales preserving the dynamic relationships amongst the variables. The results disclose that monthly snow cover fraction in the near future (2041-2060) and far future (2071-2090) will decrease significantly with respect to the historical period (1981-2000). While the annual streamflow is noted to be increasing for the basin, water supply reliability exhibits a reduction, partly as a result of the increased spill volume arising from greater snowmelt concentrated over the wet period, and partly the increase in evaporation losses due to higher temperatures. While the above results pertain to the Brahmaputra basin, similar changes are expected for the other major rivers that originate in the Tibetan Plateau.
... Not only is the Himalayas in northern India a significant supply of water, but they also manage India's climate. As a water tower endowed with a large number of glaciers, it serves as a unique drought-resistant entity by establishing a regional buffer against drought [56]. Glaciers in the Himalayas melt in the summer and give water to rivers and aquifers. ...
An extended drought period with low precipitation can result in low water availability and issues for humans, animals, and plants. Drought forecasting is critical for water resource development and management as it helps to reduce negative consequences. In this study, scientometric analysis and manual comprehensive analysis on drought modelling and forecasting are used. A scientometric analysis is used to determine the current research trend using bibliometric data and to identify relevant publication field sources with the most publications, the most frequently used keywords, the most cited articles and authors, and the countries that have made the greatest contributions to the field of water resources. This paper also tries to provide an overview of water issues, such as drought classification, drought indices, historical droughts, and their impact on Asian countries such as China, Pakistan, India, and Iran. There have been many models established for this purpose and choosing the appropriate model for study is a long procedure for researchers. An appropriate, comprehensive, pedagogical study of model ideas and historical implementations would benefit researchers by helping them to avoid overlooking viable model options, thus reducing their time spent on the topic. As a result, the goal of this paper is to review drought-forecasting approaches and recommend the best models for the Asian region. The models are divided into four categories based on their mechanisms: Regression analysis, stochastic modelling, machine learning, and dynamic modelling. The basic concepts of each approach in terms of the model’s historical use, benefits, and limitations are explained. Finally, prospects for future drought research in Asia are discussed as well as potential modelling techniques.
... In hydrology, the term buffering describes the properties of water reservoirs that alleviate asynchronicities between water supply and demand and mitigate the effects of high rainfall variability on water availability (e.g., Riebsame 1988;Calow et al. 2010;Pritchard 2017). In geomorphology, the term buffering is used with respect to the delayed and dampened sediment output from a catchment that results from internal storage of sediment (Brunsden and Thornes 1979;Armitage et al. 2013;Hoffmann 2015). ...
This study presents a conceptual framework of buffering through storage and recycling of elements in terrestrial ecosystems and reviews the current knowledge about storage and recycling of elements in plants and ecosystems. Terrestrial ecosystems, defined here as plant-soil systems, buffer inputs from the atmosphere and bedrock through storage and recycling of elements, i.e., they dampen and delay their responses to inputs. Our framework challenges conventional paradigms of ecosystem resistance derived from plant community dynamics, and instead shows that element pools and fluxes have an overriding effect on the sensitivity of ecosystems to environmental change. While storage pools allow ecosystems to buffer variability in inputs over short to intermediate periods, recycling of elements enables ecosystems to buffer inputs over longer periods. The conceptual framework presented here improves our ability to predict the responses of ecosystems to environmental change. This is urgently needed to define thresholds which must not be exceeded to guarantee ecosystem functioning. This study provides a framework for future research to explore the extent to which ecosystems buffer variability in inputs.
... The Himalayan glaciers serve as an indispensable water resource, supplying freshwater to the major river systems of Indus, Ganga and Brahmaputra. These glaciers influence every aspect of life, i.e., agricultural productivity, hydroelectric facilities, flood forecasting, water supply for urban and industrial use, tourism, wildlife and biotic ecosystems (Pritchard, 2017;IPCC, 2019). Of the major river basins of the Himalaya, the Indus possesses the highest meltwater fraction, with a total contribution of about 40% from snow and glacier melt (Lutz et al., 2014). ...
Glacier mass balance time-series measurements have immense importance in comprehending the overall regional hydrology and meteorology of the mountain systems. Such assessments are critical in the Indus River basin (compared to the Ganga and Brahmaputra), which besides having a significant contribution from the glaciers, also exhibits considerable heterogeneity in glacier response. Thus, to quantify this variability in glacier behavior and thereby develop a comprehensive understanding of the past as well as the future evolution of the glaciers, we reconstruct the annual surface mass balance records of 75 glaciers (size >1 km²) in the Suru sub-basin, western Himalaya for the period 1994-2018. We apply a remote sensing-based equilibrium line altitude-mass balance approach, supported by geodetic mass balance estimates (for 18 major glaciers) and limited field measurements. Our findings suggest a persistent negative mass balance of the glaciers (average: -0.69 ± 0.28 m w.e.a⁻¹, cumulative: -16.56 m w.e), varying from -0.46 ± 0.27 (1997) to -0.79 ± 0.28 (2018) m w.e.a⁻¹ during the study period. This overall mass loss coincides with an increased temperature (Tavg increased 0.5 °C; Tmin increased 0.27 °C; Tmax increased 0.06 °C) and reduced precipitation (by 4%) in the valley during 1994-2018, which shows the sensitivity of these glaciers to climate change. Within the Suru sub-basin, smaller, cleaner and high-altitude mountain glaciers of the Ladakh range have experienced greater mass loss (cumulative: -20.88 m w.e) compared to the Greater Himalayan range (cumulative: -13.44 m w.e). We observe latitudinal variability in mass loss in the Western Himalaya, with the highest mass loss rates in the Greater Himalayan Range (>-0.9 m w.e.a⁻¹) and lowest in the Karakoram Range (<-0.1 m w.e.a⁻¹), suggesting a transitional response of the Suru sub-basin glaciers (-0.69 m w.e.a⁻¹). The overall regional picture suggests synchronicity in the mass loss pattern of western Himalayan glaciers, predominantly controlled by the climatic conditions. Meanwhile, the variability in their mass loss rates is attributed to the unique glacier characteristics.
... On regional and local scales, glaciers are significant contributors to seasonal river flows, serving as frozen reservoirs of water that supplement runoff during warm and dry periods of low river flows [3,4,[9][10][11][12]. In High Mountain Asia, glacial meltwater is critical to the water security of 800 million downstream residents [13][14][15]. In other regions where glacial runoff plays a key role in regional water source supplements, such as the Pan-arctic [16,17], Gulf of Alaska [9,18], and around the Alps [10] and Andes [19], ongoing glacier changes also raise concerns about the sustainability of water supplies and the resulting impacts on water management and climate adaptation [3,[20][21][22]. ...
Glacial changes have great effects on regional water security because they are an important component of glacierized basin runoff. However, these impacts have not yet been integrated and evaluated in the arid/semiarid inland river basins of western China. Based on the degree-day glacier model, glacier changes and their hydrologic effects were studied in 12 subbasins in the Shiyang River basin (SYRB), Heihe River basin (HHRB) and Shule River basin (SLRB). The results showed that the glacier area of each subbasin decreased by 16.7–61.7% from 1965 to 2020. By the end of this century, the glacier areas in the three basins will be reduced by 64.4%, 72.0% and 83.4% under the three climate scenarios, and subbasin glaciers will disappear completely after the 2070s even under RCP2.6. Glacial runoff in all subbasins showed a decreasing–increasing–decreasing trend, with peak runoff experienced in 11 subbasins during 1965~2020. The contribution of glacial meltwater to total runoff in the basin ranged from 1.3% to 46.8% in the past, and it will decrease in the future due to increasing precipitation and decreasing glacial meltwater. However, the scale differences in glacier runoff are significant when aggregated over the region/basin/subbasin. This suggests that the results of large-scale generalization may be misleading for subbasin glacier water resource evaluations. Therefore, the hydrological effects of glaciers should be studied more in subbasins to provide an accurate reference for practical water resource management.
To investigate the evolution of precipitation over Asian continent in the Holocene and the associated mechanisms, we used a set of simulations of the transient climate evolution over the past 21,000 years (TraCE‐21ka), multimodel results from the Paleoclimate Modeling Intercomparison Project Phase 4 (PMIP4), and proxy records in Asia. The TraCE‐21ka results showed a tripole pattern in suborbital‐scale precipitation trends over the Asian continent during the Holocene, with a trend of increase over southern parts of the monsoon regions and arid Central Asia (ACA), and a trend of decline over northern parts of the monsoon regions and their areas of transition with ACA. This tripole pattern was corroborated by proxy records from multiple regions and multimodel results from the PMIP4. Further analysis based on single‐forcing simulations of TraCE‐21ka indicated that influences from different external forcings were different on the Asian precipitation in the main rainy seasons in the Holocene and that their combined effects shaped the tripole pattern. In summer, orbital forcing, by reducing solar radiation in mid‐to‐high latitudes and weakening the land‐sea thermal contrast, has been the dominant factor in the long‐term evolution of precipitation in the monsoon region and West Asia. In winter and spring, changes in meltwater flux played dominant roles in intensifying local water cycle and horizontal moisture advection, which drove the trend of increase in precipitation in ACA. Additionally, changes in greenhouse gas concentration and continental ice sheet forcings both also contribute to the increase in precipitation in ACA.
Drang Drung and Pensilungpa are neighbouring glaciers in the western Himalayas, sharing the same meteorological conditions and climate zone. The Drang Drung glacier is a clean glacier, whereas the Pensilungpa glacier is notable for its considerable accumulation of debris. The present study explores the topographical features of the Drang Drung and Pensilungpa glaciers and investigates how topography affects their response to climate change. Additionally, a comparison is made between these glaciers with others in the basin to assess their representativeness of the region. The study utilized Landsat Imagery and ASTER GDEM data from 1976 to 2020. The results revealed that the mean accumulation area ratio (AAR) for Drang Drung and Pensilungpa was 54% and 49%, respectively, during this period. Drang Drung has lost 8.16 km2 (10.73%) of its area, while Pensilungpa has lost 2.25 km2 (9.84%) of its area. The debris cover of Pensilungpa increased from 1.86 km2 in 1976 to 2.32 km2 in 2020, whereas the debris cover area of Drang Drung has increased comparatively more, from 4.01 km2 to 4.76 km2. Within the same time frame, the snowline altitude (SLA) shifted upward by an average of 104 m and 88 m for Drang Drung Pensilungpa, respectively. Further, our findings revealed a substantial connection between the size of glaciers and the speed at which their area is diminishing. The mean slope was identified as a key factor in influencing the rate at which the area is lost, and the retreat rates of the glaciers. The reduction in glacial area, increased debris coverage, and changes in SLA are key indicators of ice volume loss under prevailing climatic conditions. The present study recommends that long-term field-based data and the incorporation of multi-temporal satellite imagery are crucial to mitigate uncertainties in detecting changes in Himalayan glaciers. These approaches would contribute to a more accurate understanding of glacial changes, and would aid in forecasting future scenarios considering ongoing global warming trends.
Chemical weathering processes has become a growing issue in research on carbon cycling, however, mineral weathering by sulfuric acid and carbonic acid and its possible impacts on carbon cycle are yet unknown over the typical glacial catchment. To investigate the mechanisms of mineral weathering processes and its influence, the spatial–temporal variations of the major ions in Mingyong River, a glacier‐originated river located on the southeastern edge of the Qinghai‐Tibetan Plateau, were investigated. The seasonal and spatial variations in river solutes were resulted from the hydrological conditions and different mineral weathering rates. The results showed that the major ion compositions of the river waters were characterized by the dominance of Ca ²⁺ , Mg ²⁺ , HCO 3 ⁻ , with a significantly rich in SO 4 ²⁻ . A systematic increase in ionic concentrations (apart from NH 4 ⁺ and NO 3 ⁻ ) was observed in the river water from non‐monsoon to monsoon season as well as from upstream to downstream. Piper diagram results showed 100% (upstream‐midstream) and 72.5% (downstream) contributions to Ca‐HCO 3 type, respectively, indicating that a dominated carbonate weathering to the river chemistry. The (Ca ²⁺ +Mg ²⁺ )/HCO 3 ⁻ against (SO 4 ²⁻ /HCO 3 ⁻ ) scatter suggested that sulfuric and carbonic acid are responsible for chemical weathering. An increased contributions of sulfuric acid from upstream (43%) to downstream (87.3%) on the (Ca ²⁺ +Mg ²⁺ ) and from upstream (29.6%) to downstream (88.3%) on HCO 3 ⁻ using the stoichiometry analysis during the monsoon season. Contrarily, H 2 SO 4 ‐related dissolution (>65%) processes controlled the carbonate weathering during the non‐monsoon season, which indicated that sulfuric acid played a significant part in the process of rock dissolution that intensifies weathering. The effects of accelerated weathering on drinking and irrigation suitability suggested that the Mingyong River water is subject to a salinity hazard. This research demonstrates that the weathering of catchments involving sulfuric acid has the potential to alter carbon cycle and should be considered in global carbon cycle models.
The Himalayan ecosystem is fragile and needs robust management strategies for sustainability of natural resources such as water and vegetation. Therefore, reliable precipitation estimation becomes quite important from operational and regulation standpoints. It is crucial for numerous activities including policy/planning, agriculture, reservoir operations, disaster management, and others. In addition, reliable information on temporal variability of precipitation is also crucial for various applications such as agricultural and hydrological. The western Himalaya receives two distinct weather systems during summer and winter. Summer is responsible (largely) for rainfall and winter is for snowfall. Therefore, we hypothesize that there may not be a single set of parameterization schemes that can represent well both the weather systems. To investigate, we set up the WRF modeling system and performed six experiments with a combination of three microphysics (MP3, MP3, and WSM6) and two cumulus schemes (KF, and BMJ). It was found that the precipitation along the Himalayan foothills (near to basin terminal) is underestimated in four out of six experiments. Only experiments with BMJ cumulus scheme along with WSM6 and MP8 microphysics were able to show a considerable amount of precipitation along these foothills. It was noted that all six experiments showed high precipitation in the upstream region and over the mountain peaks and ridges in North-Western Himalaya. For DJF, each experiment was found to have large biases and none of them represented the observation with high confidence. However, the selection of observation reference data itself is a challenging task because of data paucity in this region. Therefore, the closest experiment to the most appropriate observation was selected as the reliable configuration (MP8_KF: MP8 microphysics and KF cumulus scheme) for DJF precipitation simulation. In this study we have, for the first time, reported the role of seasonal sensitivity for the climate scale simulations as we found that different schemes were suitable for different weather systems.
The Qinghai Tibet Plateau (QTP), known as the Roof of the World and the Water Tower of Asia, has the largest number of lakes in the world, and because of its high altitude and near absence of disturbances by human activity, the plateau has long been an important site for studying global climate change. Hydrological stations cannot be readily set up in this region, and in situ gauge data are not always publicly accessible. Satellite radar altimetry has become a very important alternative to in situ observations as a source of data. Estimation of the water levels of lakes via radar altimetry is often limited by temporal and spatial coverage, and, therefore, multi-altimeter data are often used to monitor lake levels. Restricted by the accuracy of waveform processing and the interval period between different altimetry missions, the accuracy and the sampling frequency of the water level series are typically low. By processing and merging data from eight different altimetry missions, the developed datasets provided the water level changes for 362 lakes (larger than 10 km2) in the QTP from 2002 to 2021. The period for the lake level change series, which affords high accuracy, can be much longer for many lake systems. The present datasets and associated approaches are valuable for calculating the changes in lake storage, trend analyses of the lake levels, short-term monitoring of the overflow of lakes, flooding disasters on the plateau, and the relationships between changes in the lake ecosystems and changes in the water resources.
Volume 1: Spatio-Temporal Monitoring of Forests and Climate is aimed to describe the recent progress and developments of geospatial technologies (remote sensing and GIS) for assessing, monitoring and managing fragile Himalayan ecosystems and their sustainability under climate change. It is a collective research contribution from renowned researchers and academicians working in the Hindu Kush Himalayan (HKH) mountain range. The Himalayas ecosystems have been facing substantial transformation due to severe environmental conditions, land transformation, forest degradation and fragmentation. The authors utilized satellite datasets and algorithms to discuss the intricacy of land use/land cover change, forest and agricultural ecosystems, canopy height estimation, above-ground biomass, wildfires, carbon sequestration, and landscape restoration. Furthermore, the potential impacts of climate change on ecosystems, biodiversity and future food and nutritional security are also addressed including the impact on the livelihood of people of the Himalayas. This comprehensive Handbook explains the advanced geospatial technologies for mapping and management of natural resources of the Himalayas.
Glacier health across High Mountain Asia (HMA) is highly heterogeneous and strongly governed by regional climate, which is variably influenced by monsoon dynamics and the westerlies. We explore four decades of glacier energy and mass balance at three climatically distinct sites across HMA by utilising a detailed land surface model driven by bias-corrected Weather Research and Forecasting (WRF) meteorological forcing. All three glaciers have experienced long-term mass losses (ranging from -0.04$\pm$0.09 to -0.59$\pm$0.20 m w. e. a$^{-1}$) consistent with widespread warming across the region. However, complex and contrasting responses of glacier energy and mass balance to the patterns of the Indian Summer Monsoon were evident, largely driven by the role snowfall timing, amount and phase. A later monsoon onset generates less total snowfall to the glacier in the southeastern Tibetan Plateau during May-June, augmenting net shortwave radiation and affecting annual mass balance (-0.5 m w.e. on average compared to early onset years). Conversely, timing of the monsoon's arrival has limited impact for the Nepalese Himalaya which is more strongly governed by the temperature and snowfall amount during the core monsoon season. In the arid central Tibetan Plateau, a later monsoon arrival results in a 40 mm (58\%) increase of May-June snowfall on average compared to early onset years, likely driven by the greater interaction of westerly storm events. Meanwhile,a late monsoon cessation at this site sees an average 200 mm (192\%) increase in late summer precipitation due to monsoonal storms. A trend toward weaker intensity monsoon conditions in recent decades, combined with long-term warming patterns, has produced predominantly negative glacier mass balances for all sites (up to 1 m w.e. more mass loss in the Nepalese Himalaya compared to strong monsoon intensity years) but sub-regional variability in monsoon timing can additionally complicate this response.
There was sufficient evidence to indicate a nearly balanced glacier mass change (termed glacier anomaly) for Karakoram Mts. since the 1970s, in contrast to worldwide glacier mass losses caused by climate warming. Recently, this anomalous phenomenon was detected over the neighboring western Kunlun and Pamir Mts. However, the southeastern limit of this glacier anomaly remains uncertain, owing to the paucity of glacier mass balance observations across the interior and northern Tibetan Plateau (INTP). In this study, we presented a decadal glacier mass balance estimation in the INTP by differencing the SRTM DEM with the topographic data produced from TanDEM-X bistatic InSAR images. From 2000 to 2012, decade-average glacier mass balances of between −0.339 ± 0.040 and 0.237 ± 0.078 m w.e. yr−1 were detected over 22 glacierized areas. Significantly, we found a gradient and switch of glacier mass loss over the southeastern portion to glacier mass gain over the northwestern portion. This varying spatial pattern illustrates that glacier anomaly has existed over the northwestern or even central zone of the INTP since the early 21st century. This study provides important evidence for the model simulation of both glacier evolution and atmospheric circulations in investigating the prevailing mechanism of the regional anomalous phenomenon.
Climate change is a significant threat to people living in mountainous regions. It is essential to understand how montane communities currently depend especially on the provisioning ecosystem services (ES) and the ways in which climate change will impact these services, so that people can develop relevant adaptation strategies. The ES in the Gurez Valley, in the Western Himalayas of Pakistan, provide a unique opportunity to explore these questions. This understudied area is increasingly exposed not only to climate change but also to the overexploitation of resources. Hence, this study aimed to (a) identify and value provisioning ES in the region; (b) delineate indigenous communities’ reliance on ES based on valuation; and (c) measure the perceptions of indigenous communities of the impact of climate change on the ES in Gurez Valley. Semi-structured interviews and focus group discussions were used to classify the provisioning ES by using the ‘Common International Classification on Ecosystem Services’ (CICES) table and applying the ‘Total Economic Valuation (TEV)’ Framework. Results indicate that the indigenous communities are highly dependent on ES, worth 6730 ± 520 USD/Household (HH)/yr, and perceive climate change as a looming threat to water, crops, and rearing livestock ESS in the Gurez Valley. The total economic value of the provisioning ES is 3.1 times higher than a household’s average income. Medicinal plant collection is a significant source of revenue in the Valley for some households, i.e., worth 766 ± 134.8 USD/HH/yr. The benefits of the sustainable use of ES and of climate change adaptation and mitigation, are culturally, economically, and ecologically substantial for the Western Himalayans.
Glaciers are known as natural “solid reservoirs”, and they play a dual role between the composition of water resources and the river runoff regulation in arid and semi-arid areas of China. In this study, we used in situ observation data from Urumqi Glacier No. 1, Xinjiang Uygur Autonomous Region, in combination with meteorological data from stations and a digital elevation model, to develop a distributed degree-day model for glaciers in the Urumqi River Basin to simulate glacier mass balance processes and quantify their effect on streamflow during 1980–2020. The results indicate that the mass loss and the equilibrium line altitude (ELA) of glaciers in the last 41 years had an increasing trend, with the average mass balance and ELA being −0.85 (±0.32) m w.e./a (meter water-equivalent per year) and 4188 m a.s.l., respectively. The glacier mass loss has increased significantly during 1999–2020, mostly due to the increase in temperature and the extension of ablation season. During 1980–2011, the average annual glacier meltwater runoff in the Urumqi River Basin was 0.48×108 m3, accounting for 18.56% of the total streamflow. We found that the annual streamflow in different catchments in the Urumqi River Basin had a strong response to the changes in glacier mass balance, especially from July to August, and the glacier meltwater runoff increased significantly. In summary, it is quite possible that the results of this research can provide a reference for the study of glacier water resources in glacier-recharged basins in arid and semi-arid areas.
Central Asia is a data scarce region, which makes it difficult to monitor and minimize the impacts of a drought. To address this challenge, in this study, a high-resolution (5 km) Standardized Precipitation Evaporation Index (SPEI-HR) drought dataset was developed for Central Asia with different time scales from 1981–2018, using Climate Hazards group InfraRed Precipitation with Station’s (CHIRPS) precipitation and Global Land Evaporation Amsterdam Model’s (GLEAM) potential evaporation (E p ) datasets. As indicated by the results, in general, over time and space, the SPEI-HR correlated well with SPEI values estimated from coarse-resolution Climate Research Unit (CRU) gridded time series dataset. The 6-month timescale SPEI-HR dataset displayed a good correlation of 0.66 with GLEAM root zone soil moisture (RSM) and a positive correlation of 0.26 with normalized difference vegetation index (NDVI) from Global Inventory Monitoring and Modelling System (GIMMS). After observing a clear agreement between SPEI-HR and drought indicators for the 2001 and 2008 drought events, an emerging hotspot analysis was conducted to identify drought prone districts and sub-basins.
Glaciers are a reliable freshwater resource in arid regions of West China and the vulnerability of its changes is closely related to regional ecosystem services and economic sustainable development. Here, we took the Qilian Mountains as an example and analyzed the spatiotemporal characteristics of glacier changes from 1998 to 2018, based on remote sensing images and the Second Chinese Glacier Inventory. We estimated the basic organizational framework and evaluation index system of glacier change vulnerability from exposure, sensitivity and adaptability, which covered the factors of physical geography, population status and socio-economic level. We analyzed the spatial and temporal evolutions of glacier change vulnerability by using the vulnerability evaluation model. Our results suggested that: (1) Glacier area and volume decreased by 71.12±98.98 km2 and 5.59±4.41 km3, respectively, over the recent two decades, which mainly occurred at the altitude below 4800 m, with an area shrinking rate of 2.5%. In addition, glaciers in the northern aspect (northwest, north and northeast) had the largest area reduction. Different counties exhibited remarkable discrepancies in glacier area reduction, Tianjuan and Minle presented the maximum and minimum decrease, respectively. (2) Glacier change vulnerability level showed a decreasing trend in space from the central to the northwestern and southeastern regions with remarkable differences. Vulnerability level had increased significantly over time and was mainly concentrated in moderate, high and extreme levels with typical characteristics of phases and regional complexity. Our study can not only help to understand and master the impacts of recent glacier changes on natural and social aspects but also be conducive to evaluate the influences of glacier retreat on socio-economic developments in the future, thus providing references for formulating relevant countermeasures to achieve regional sustainable development.
Himalayan glaciers are undergoing rapid mass loss but rates of contemporary change lack long-term (centennial-scale) context. Here, we reconstruct the extent and surfaces of 14,798 Himalayan glaciers during the Little Ice Age (LIA), 400 to 700 years ago. We show that they have lost at least 40 % of their LIA area and between 390 and 586 km3 of ice; 0.92 to 1.38 mm Sea Level Equivalent. The long-term rate of ice mass loss since the LIA has been between − 0.011 and − 0.020 m w.e./year, which is an order of magnitude lower than contemporary rates reported in the literature. Rates of mass loss depend on monsoon influence and orographic effects, with the fastest losses measured in East Nepal and in Bhutan north of the main divide. Locally, rates of loss were enhanced with the presence of surface debris cover (by 2 times vs clean-ice) and/or a proglacial lake (by 2.5 times vs land-terminating). The ten-fold acceleration in ice loss we have observed across the Himalaya far exceeds any centennial-scale rates of change that have been recorded elsewhere in the world.
This chapter assesses climate information relevant to regional impact and risk assessment. It complements other WG1 chapters which focus on the physical processes determining changes in the climate system and on methods for estimating regional changes.
This chapter is new in the IPCC WGI assessment reports, in that it represents a contribution to the “IPCC Risk Framework”. Within this framework, climate-related impacts and risks are determined through an interplay between the occurrence of climate hazards and their consequences depending on the exposure of the affected human or natural system and its vulnerability to the hazardous conditions. In Chapter 12, we are assessing climatic impact-drivers that could lead to hazards or to opportunities, from the literature and model results since AR5. This will particularly support the assessment of key risks related to climate change by WGII (Chapter 16). Despite the fact that impacts may also be induced by climate adaptation and mitigation policies themselves, as well as by socioeconomic trends, changes in vulnerability or exposure, and external geophysical hazards such as volcanoes, the focus here is only on ‘climatic’ impacts and risks induced by shifts in physical climate phenomena that directly influence human and ecological systems.
The Indus basin is one of the regions in the world that is faced with major challenges for its water sector, due to population growth, rapid urbanisation and industrialisation, environmental degradation, unregulated utilization of the resources, inefficient water use and poverty, all aggravated by climate change. The Indus Basin is shared by 4 countries – Pakistan, India, Afghanistan and China. With a current population of 237 million people which is projected to increase to 319 million in 2025 and 383 million in 2050, already today water resources are abstracted almost entirely (more than 95% for irrigation). Climate change will result in increased water availability in the short term. However in the long term water availability will decrease. Some current aspects in the basin need to be re-evaluated. During the past decades water abstractions – and especially groundwater extractions – have augmented continuously to support a rice-wheat system where rice is grown during the kharif (wet, summer) season (as well as sugar cane, cotton, maize and other crops) and wheat during the rabi (dry, winter) season. However, the sustainability of this system in its current form is questionable. Additional water for domestic and industrial purposes is required for the future and should be made available by a reduction in irrigation requirements. This paper gives a comprehensive listing and description of available options for current and future sustainable water resources management (WRM) within the basin. Sustainable WRM practices include both water supply management and water demand management options. Water supply management options include: (1) reservoir management as the basin is characterised by a strong seasonal behaviour in water availability (monsoon and meltwater) and water demands; (2) water quality conservation and investment in wastewater infrastructure; (3) the use of alternative water resources like the recycling of wastewater and desalination; (4) land use planning and soil conservation as well as flood management, with a focus on the reduction of erosion and resulting sedimentation as well as the restoration of ecosystem services like wetlands and natural floodplains. Water demand management options include: (1) the management of conjunctive use of surface and groundwater; as well as (2) the rehabilitation and modernization of existing infrastructure. Other demand management options are: (3) the increase of water productivity for agriculture; (4) crop planning and diversification including the critical assessment of agricultural export, especially (basmati) rice; (5) economic instruments and (6) changing food demand patterns and limiting post-harvest losses.
Significance
Ethnic divides play a major role in many armed conflicts around the world and might serve as predetermined conflict lines following rapidly emerging societal tensions arising from disruptive events like natural disasters. We find evidence in global datasets that risk of armed-conflict outbreak is enhanced by climate-related disaster occurrence in ethnically fractionalized countries. Although we find no indications that environmental disasters directly trigger armed conflicts, our results imply that disasters might act as a threat multiplier in several of the world’s most conflict-prone regions.
The applicability of six fine-resolution precipitation products, including
precipitation radar, infrared, microwave and gauge-based products, using
different precipitation computation recipes, is evaluated using statistical
and hydrological methods in northeastern China. In addition, a framework
quantifying uncertainty contributions of precipitation products,
hydrological models, and their interactions to uncertainties in ensemble
discharges is proposed. The investigated precipitation products are Tropical
Rainfall Measuring Mission (TRMM) products (TRMM3B42 and TRMM3B42RT), Global Land
Data Assimilation System (GLDAS)/Noah, Asian Precipitation – Highly-Resolved Observational Data Integration Towards
Evaluation of Water Resources (APHRODITE), Precipitation Estimation from Remotely Sensed Information
using Artificial Neural Networks (PERSIANN), and a Global Satellite Mapping of Precipitation (GSMAP-MVK+) product. Two
hydrological models of different complexities, i.e. a water and energy
budget-based distributed hydrological model and a physically based
semi-distributed hydrological model, are employed to investigate the
influence of hydrological models on simulated discharges. Results show
APHRODITE has high accuracy at a monthly scale compared with other products,
and GSMAP-MVK+ shows huge advantage and is better than TRMM3B42 in relative bias (RB),
Nash–Sutcliffe coefficient of efficiency (NSE), root mean square error (RMSE), correlation
coefficient (CC), false alarm ratio, and critical success index. These findings
could be very useful for validation, refinement, and future development of
satellite-based products (e.g. NASA Global Precipitation Measurement).
Although large uncertainty exists in heavy precipitation, hydrological
models contribute most of the uncertainty in extreme discharges.
Interactions between precipitation products and hydrological models can have
the similar magnitude of contribution to discharge uncertainty as the
hydrological models. A better precipitation product does not guarantee a
better discharge simulation because of interactions. It is also found that a
good discharge simulation depends on a good coalition of a hydrological
model and a precipitation product, suggesting that, although the
satellite-based precipitation products are not as accurate as the
gauge-based products, they could have better performance in discharge
simulations when appropriately combined with hydrological models. This
information is revealed for the first time and very beneficial for
precipitation product applications.
Soil and Water Assessment Tool (SWAT) was used to assess the water yield and evapotranspiration for the Gomti River basin, India for over a period of 25 years (1985–2010). Streamflow calibration and validation of results showed satisfactory performance (NSE: 0.68– 0.51; RSR: 0.56–0.68; |PBIAS|: 2.5–24.3) of the model. The water yield was higher in the midstream sub-basins compared to upstream and downstream sub-basins whereas evapotranspiration per unit area decreased from upstream to the downstream. Both evapotranspiration and water yield at upstream and midstream sub-basins increased from 1985 to 2010, whereas water yield at downstream decreased from 1985 to 2010. We found that the spatial and temporal patterns of evapotranspiration and water yield were closely linked to climatic conditions and irrigation in the basin. The long-term trends in water yield point to a drying tendency of downstream sub-basin covering the districts of Jaunpur and Varanasi.
Global gridded precipitation is an essential driving input for hydrologic models to simulate runoff dynamics in large river basins. However, the data often fail to adequately represent precipitation variability in mountainous regions due to orographic effects and sparse and highly uncertain gauge data. Water balance simulations in tropical montane regions covered by cloud forests are especially challenging because of the additional water input from cloud water interception. The ISI-MIP2 hydrologic model ensemble encountered these problems for Andean sub-basins of the Upper Amazon Basin, where all models significantly underestimated observed runoff. In this paper, we propose simple yet plausible ways to adjust global precipitation data provided by WFDEI, the WATCH Forcing Data methodology applied to ERA-Interim reanalysis, for tropical montane watersheds. The modifications were based on plausible reasoning and freely available tropics-wide data: (i) a high-resolution climatology of the Tropical Rainfall Measuring Mission (TRMM) and (ii) the percentage of tropical montane cloud forest cover. Using the modified precipitation data, runoff predictions significantly improved for all hydrologic models considered. The precipitation adjustment methods presented here have the potential to enhance other global precipitation products for hydrologic model applications in the Upper Amazon Basin as well as in other tropical montane watersheds.
Scarcity of in-situ observations coupled with high orographic influences has prevented a comprehensive assessment of precipitation distribution in the high-altitude catchments of Indus basin. Available data are generally fragmented and scattered with different organizations and mostly cover the valleys. Here, we combine most of the available station data with the indirect precipitation estimates at the accumulation zones of major glaciers to analyse altitudinal dependency of precipitation in the high-altitude Indus basin. The available observations signified the importance of orography in each sub-hydrological basin but could not infer an accurate distribution of precipitation with altitude. We used Kriging with External Drift (KED) interpolation scheme with elevation as a predictor to appraise spatiotemporal distribution of mean monthly, seasonal and annual precipitation for the period of 1998–2012. The KED-based annual precipitation estimates are verified by the corresponding basin-wide observed specific runoffs, which show good agreement. In contrast to earlier studies, our estimates reveal substantially higher precipitation in most of the sub-basins indicating two distinct rainfall maxima; 1st along southern and lower most slopes of Chenab, Jhelum, Indus main and Swat basins, and 2nd around north-west corner of Shyok basin in the central Karakoram. The study demonstrated that the selected gridded precipitation products covering this region are prone to significant errors. In terms of quantitative estimates, ERA-Interim is relatively close to the observations followed by WFDEI and TRMM, while APHRODITE gives highly underestimated precipitation estimates in the study area. Basin-wide seasonal and annual correction factors introduced for each gridded dataset can be useful for lumped hydrological modelling studies, while the estimated precipitation distribution can serve as a basis for bias correction of any gridded precipitation products for the study area.
Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (∼5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.
Soil and Water Assessment Tool (SWAT) was used to assess the water yield and evapotranspiration for the Gomti River basin, India for over a period of 25 years (1985–2010). Streamflow calibration and validation of results showed satisfactory performance (NSE: 0.68– 0.51; RSR: 0.56–0.68; |PBIAS|: 2.5–24.3) of the model. The water yield was higher in the midstream sub-basins compared to upstream and downstream sub-basins whereas evapotranspiration per unit area decreased from upstream to the downstream. Both evapotranspiration and water yield at upstream and midstream sub-basins increased from 1985 to 2010, whereas water yield at downstream decreased from 1985 to 2010. We found that the spatial and temporal patterns of evapotranspiration and water yield were closely linked to climatic conditions and irrigation in the basin. The long-term trends in water yield point to a drying tendency of downstream sub-basin covering the districts of Jaunpur and Varanasi.
We present glacier thickness changes over the entire
Pamir–Karakoram–Himalaya arc based on ICESat satellite altimetry data for
2003–2008. We highlight the importance of C-band penetration for studies
based on the SRTM elevation model. This penetration seems to be of
potentially larger magnitude and variability than previously assumed. The
most negative rate of region-wide glacier elevation change (
Among meteorological elements, precipitation has a large spatial variability and less observation, particularly in high-mountain Asia, although precipitation in mountains is an important parameter for hydrological circulation. We estimated precipitation contributing to glacier mass at the median elevation of glaciers, which is presumed to be at equilibrium-line altitude (ELA) such that mass balance is zero at that elevation, by tuning adjustment parameters of precipitation. We also made comparisons between the median elevation of glaciers, including the effect of drifting snow and avalanche, and eliminated those local effects. Then, we could obtain the median elevation of glaciers depending only on climate to estimate glacier surface precipitation.
The calculated precipitation contributing to glacier mass can elucidate that glaciers in arid high-mountain Asia receive less precipitation, while much precipitation makes a greater contribution to glacier mass in the Hindu Kush, the Himalayas, and the Hengduan Shan due to not only direct precipitation amount but also avalanche nourishment. We classified glaciers in high-mountain Asia into summer-accumulation type and winter-accumulation type using the summer-accumulation ratio and confirmed that summer-accumulation-type glaciers have a higher sensitivity than winter-accumulation-type glaciers.
Human population growth, economic development, climate change, and the need to close the electricity access gap have stimulated the search for new sources of renewable energy. In response to this need, major new initiatives in hydropower development are now under way. At least 3,700 major dams, each with a capacity of more than 1 MW, are either planned or under construction, primarily in countries with emerging economies. These dams are predicted to increase the present global hydroelectricity capacity by 73 % to about 1,700 GW. Even such a dramatic expansion in hydropower capacity will be insufficient to compensate for the increasing electricity demand. Furthermore, it will only partially close the electricity gap, may not substantially reduce greenhouse gas emission (carbon dioxide and methane), and may not erase interdependencies and social conflicts. At the same time, it is certain to reduce the number of our planet’s remaining free-flowing large rivers by about 21 %. Clearly, there is an urgent need to evaluate and to mitigate the social, economic, and ecological ramifications of the current boom in global dam construction.
Ice volume estimates are crucial for assessing water reserves stored in
glaciers. Due to its large glacier coverage, such estimates are of
particular interest for the Himalayan–Karakoram (HK) region. In this study,
different existing methodologies are used to estimate the ice reserves:
three area–volume relations, one slope-dependent volume estimation method,
and two ice-thickness distribution models are applied to a recent, detailed,
and complete glacier inventory of the HK region, spanning over the period
2000–2010 and revealing an ice coverage of 40 775 km2. An
uncertainty and sensitivity assessment is performed to investigate the
influence of the observed glacier area and important model parameters on the
resulting total ice volume. Results of the two ice-thickness distribution
models are validated with local ice-thickness measurements at six glaciers.
The resulting ice volumes for the entire HK region range from 2955 to 4737 km3, depending on the
approach. This range is lower than most previous estimates. Results from the
ice thickness distribution models and the slope-dependent thickness
estimations agree well with measured local ice thicknesses. However, total
volume estimates from area-related relations are larger than those from
other approaches. The study provides evidence on the significant effect of
the selected method on results and underlines the importance of a careful
and critical evaluation.
The hydrological role of the meltwater resources in the Indus, Ganges, Brahmaputra, Syr Darya, Amu Darya and Mekong river basins is, for the first time, comprehensively assessed at the basin scale. The states of the meltwater resources in the baseline (1961-1990) and current (2001-2010) periods are analyzed using the following characteristics: specific glacier runoff (average depth of annual discharge from glaciercovered area), basin total glacier runoff, shares of renewable and nonrenewable components in glacier runoff, total seasonal surface snowmelt from non-glaciated areas, portion of seasonal snowmelt lost for the recharge of groundwater aquifers, the contribution of glacier runoff and seasonal snowmelt to mean annual flow (MAF). The report presents a critical review of relevant publications and assessment of methods and data availability, compatibility, accuracy ranges and suitability for basin-scale studies. The evaluation of meltwater components is based on a wide range of data compiled from published sources: glacier mass budget items, rates of glacier mass balance, areal extent and total volume of glaciers and seasonal snow, terrestrial water budgets, and recharge rates of groundwater aquifers. Glacier runoff is evaluated using a semidistributed model developed for this study. The evaluation of seasonal snowmelt is based on the published outcomes of a fully distributed model. It is demonstrated that glaciers and seasonal snow play a negligible role as contributors to MAF in the Mekong Basin (<1%) and an insignificant role in the Ganges and Brahmaputra basins (7% and 3%, respectively). In the Indus Basin, meltwater contributes around 35-40% to the total flow with seasonal snowmelt and glacier runoff shares being approximately equal. In the Amu Darya and Syr Darya basins, meltwater resources contribute 69% and 79%, respectively, to mean annual streamflow, and the share of seasonal snowmelt by far outweighs that of glaciers. From 1961-1990 to 2001-2010, the total values of meltwater components decreased by 6-25% in all the basins, apart from Mekong where snowmelt increased by 30% due to a slight increase in the snow cover extent. Meltwater contribution to annual flow decreased at the same time by 5% in the Indus and Amu Darya basins and by 20% in the Syr Darya Basin. In other study basins, contribution of meltwater to flow changed by less than 0.5%. The most pronounced change occurred in the composition of glacier runoff: the share of the nonrenewable component in the total glacier runoff increased from 16-30% to 26-46% in all study basins. At the same time, the share of the renewable component decreased more significantly due to the overall reduction of glaciercovered areas. As a result, total contribution of glacier runoff to MAF decreased in all study basins. It is shown that, future reduction of glaciers and seasonal snow cover due to climate change (CC) will mainly affect the seasonality of river flow and only marginally impact MAF in the Indus, Amu Darya and Syr Darya basins. In the Ganges, Brahmaputra and Mekong basins, future changes in glacier and seasonal snow extent will have little effect on hydrological regime altogether.
Central Asia features an extreme continental climate with mostly arid to semi-arid conditions. Due to low precipitation and therefore low water availability, water is a scarce resource and often the limiting factor for socio-economic development. The aim of this model study was to compare the uncertainties of hydrological modelling induced by global and regional climate data sets and to calculate the impacts on estimates of renewable water resources. Within this integrated model study the hydrological and water use model Water Global Assessment and Prognosis 3 (WaterGAP 3) is being applied to all river basins located in Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan, and Mongolia in five arc minutes spatial resolution (~6 × 9 km/grid cell). The model was driven by different global and regional climate data sets to estimate their impact on modelled water resources in Central Asia. In detail, these are the global TS data set of the Climate Research Unit (CRU), the WATCH forcing data (WFD) developed within the EU–FP6 Project “WATer and global Change”, the Global Precipitation Climatology Centre (GPCC) Reanalysis product v6, and the regional Aphrodite’s Water Resources data set (Aphrodite). The performance of the model is then being evaluated by comparing modelled and observed river discharge for the time period 1971–2000. Finally, the uncertainties in modelled water availability induced by the different data sets are quantified to point out the consequences for water management. Over the entire region, mean and maximum annual precipitations given by the various data sets differ by 13 % and up to 42 %, respectively. In addition, considerable deviation of temporal dynamics is found in some locations, where a pairwise comparison showed poor agreement between CRU and GPCC/WFD (Nash–Sutcliffe efficiency 0.27/0.23). Thus, also modelled discharge shows high temporal and spatial variations which leads to differences in median model efficiency of 0.11 between the data sets.
Despite the recognized importance of reservoirs and dams, global datasets describing their characteristics and geographical distribution are largely incomplete. To enable advanced assessments of the role and effects of dams within the global river network and to support strategies for mitigating ecohydrological and socioeconomic costs, we introduce here the spatially explicit and hydrologically linked Global Reservoir and Dam database (GRanD). As of early 2011, GRanD contains information regarding 6862 dams and their associated reservoirs, with a total storage capacity of 6197 km(3). On the basis of these records, we estimate that about 16.7 million reservoirs larger than 0.01 ha - with a combined storage capacity of approximately 8070 km(3) - may exist worldwide, increasing Earth's terrestrial surface water area by more than 305 000 km(2). We find that 575 900 river kilometers, or 7.6% of the world's rivers with average flows above 1 cubic meter per second (m(3) s(-1)), are affected by a cumulative upstream reservoir capacity that exceeds 2% of their annual flow; the impact is highest for large rivers with average flows above 1000 m(3) s(-1), of which 46.7% are affected. Finally, a sensitivity analysis suggests that smaller reservoirs have substantial impacts on the spatial extent of flow alterations despite their minor role in total reservoir capacity.
Ongoing and projected future changes in glacier extent and water storage globally have lead to concerns about the implications for water supplies. However, the current magnitude of glacier contributions to river runoff is not well known, nor is the population at risk to future glacier changes. We estimate an upper bound on glacier melt contribution to seasonal streamflow by computing the energy balance of glaciers globally. Melt water quantities are computed as a fraction of total streamflow simulated using a hydrology model and the melt fraction is tracked down the stream network. In general, our estimates of the glacier melt contribution to streamflow are lower than previously published values. Nonetheless, we find that globally an estimated 225 (36) million people live in river basins where maximum seasonal glacier melt contributes at least 10% (25%) of streamflow, mostly in the High Asia region.
The reanalysis at National Centers for Environmental Prediction (NCEP) focuses on atmospheric states reports generated by a constant model and a constant data assimilation system. The datasets have been exchanged among national and international partners and used in several more reanalyses. The new data assimilation techniques have been introduced including three-dimensional variational data assimilation (3DVAR), 4DVAR, and ensembles of analyses such as ensemble Kalman filter (EnKF), which produce not only an ensemble mean analysis but also a measure of the uncertainty. The new climate forecast system reanalysis (CFSR) was executed to create initial states for the atmosphere, ocean, land, and sea ice that are consistent as possible with the next version of the climate forecast system (CFS) version 2, which is to be implemented operationally at NCEP in 2010. Several graphical plots were generated automatically at the end of each reanalyzed month and were displayed on the CFSR Web site in real time.
Mass loss of Himalayan glaciers has wide-ranging consequences such as changing runoff distribution, sea level rise and an increasing risk of glacial lake outburst floods (GLOFs). The assessment of the regional and global impact of glacier changes in the Himalaya is, however, hampered by a lack of mass balance data for most of the range. Multi-temporal digital terrain models (DTMs) allow glacier mass balance to be calculated. Here, we present a time series of mass changes for ten glaciers covering an area of about 50 km2 south and west of Mt. Everest, Nepal, using stereo Corona spy imagery (years 1962 and 1970), aerial images and recent high resolution satellite data (Cartosat-1). This is the longest time series of mass changes in the Himalaya. We reveal that the glaciers have been significantly losing mass since at least 1970, despite thick debris cover. The specific mass loss for 1970-2007 is 0.32 ± 0.08 m w.e. a-1, however, not higher than the global average. Comparisons of the recent DTMs with earlier time periods indicate an accelerated mass loss. This is, however, hardly statistically significant due to high uncertainty, especially of the lower resolution ASTER DTM. The characteristics of surface lowering can be explained by spatial variations of glacier velocity, the thickness of the debris-cover, and ice melt due to exposed ice cliffs and ponds.
Himalayan glaciers are a focus of public and scientific debate. Prevailing uncertainties are of major concern because some
projections of their future have serious implications for water resources. Most Himalayan glaciers are losing mass at rates
similar to glaciers elsewhere, except for emerging indications of stability or mass gain in the Karakoram. A poor understanding
of the processes affecting them, combined with the diversity of climatic conditions and the extremes of topographical relief
within the region, makes projections speculative. Nevertheless, it is unlikely that dramatic changes in total runoff will
occur soon, although continuing shrinkage outside the Karakoram will increase the seasonality of runoff, affect irrigation
and hydropower, and alter hazards.
Streamflow in the Himalayan rivers is generated from rainfall, snow and ice. The distribution of runoff produced from these sources is such that the streamflow may be observed in these rivers throughout the year, i.e. they are perennial in nature. Snow and glacier melt runoff contributes substantially to the annual flows of these rivers and its estimation is required for the planning, development and management of the water resources of this region. The average contribution of snow and glacier melt runoff in the annual flows of the Satluj River at Bhakra Dam has been determined. Keeping in view the availability of data for the study basin, a water balance approach was used and a water budget period of 10 years (October 1986-September 1996) was considered for the analysis. The rainfall input to the study basin over the water budget period was computed from isohyets using rainfall data of 10 stations located at different elevations in the basin. The total volume of flow for the same period was computed using observed flow data of the Satluj River at Bhakra Dam. A relationship between temperature and evaporation was developed and used to estimate the évapotranspiration losses. The snow-covered area, and its depletion with time, was determined using satellite data. It was found that the average contribution of snow and glacier runoff in the annual flow of the Satluj River at Bhakra Dam is about 59%, the remaining 41% being from rain.
This paper seeks to explain evidence of distinctive late- and post-Little Ice Age glacier change in the Karakoram Himalaya and a recent, seemingly anomalous, expansion. Attention is directed to processes that support and concentrate glacier mass, including an all-year accumulation regime, avalanche nourishment, and effects related to elevation. Glacier basins have exceptional elevation ranges, and rockwalls make up the larger part of their area. However, more than 80% of the ice cover is concentrated between 4000 and 5500 m elevation. Classification into Turkestan-, Mustagh-, and Alpine-type glaciers is revisited to help identify controls over mass balance. Estimates of changes based on snowlines, equilibrium line altitudes, and accumulation area ratio are shown to be problematic. Extensive debris covers in ablation zone areas protect glacier tongues. They are relatively insensitive to climate change, and their importance for water supply has been exaggerated compared to clean and thinly covered ablation zone ice. Recent changes include shifts in seasonal temperatures, snowfall, and snow cover at high elevations. Understanding their significance involves rarely investigated conditions at higher elevations that lack monitoring programs.
Process-based hydrologic models are usually calibrated prior to application to ensure that they closely match reality. However, different hydrologic response to varied climatic conditions might affect model calibration and validation. A case study was conducted for a 901 km2 watershed of northern Michigan to compare the effects of calibrating the Soil and Water Assessment Tool (SWAT) watershed model with different climatic datasets representing drought (1948–1949) versus average (1969–1970) conditions. The effects of the different climatic conditions on parameter response and sensitivity were evaluated, and performance of the two calibration versions was compared using a common validation period, 1950–1965. For the drought- and average-calibration periods, models were well calibrated, as indicated by high Nash-Sutcliffe efficiency coefficients (E = 0.8 and 0.9), and low deviation of discharge values (D = 2.9% and 3.4%). Evapotranspiration parameters differed under the two sets of climatic conditions. The plant water uptake compensation factor (EPCO), appropriately reflected plant water uptake patterns in varied climatic conditions. Snow melting parameters differed between the two scenarios. A comparison of baseflow values simulated by SWAT versus those computed by a hydrograph separation method showed that the SWAT method treated most snowmelt as surface runoff, whereas the latter method treated much of it as baseflow. The drought-calibrated version of the model performed much better during the validation period (1950–1965) (E = 0.8, D = 2.6%) than did the average-calibrated version (E = 0.4, D = 41.4%).
The hydrological budget of Himalayan rivers is dominated by monsoonal rainfall and snowmelt, but their relative impact is not well established because this remote region lacks a dense gauge network. Here, we use a combination of validated remotely-sensed climate parameters to characterize the spatiotemporal distribution of rainfall, snowfall, and evapotranspiration in order to quantify their relative contribution to mean river discharge. Rainfall amounts are calculated from calibrated, orbital, high-resolution Tropical Rainfall Measurement Mission data, and snow-water equivalents are computed from a snowmelt model based on satellite-derived snow cover, surface temperature, and solar radiation. Our data allow us to identify three key aspects of the spatiotemporal precipitation pattern. First, we observe a strong decoupling between the rainfall on the Himalayan foreland versus that in the mountains: a pronounced sixfold, east-west rainfall gradient in the Ganges plains exists only at elevations <500 m asl. Mountainous regions (500 to 5000 m asl) receive nearly equal rainfall amounts along strike. Second, whereas the Indian summer monsoon is responsible for more than 80% of annual rainfall in the central Himalaya and Tibetan Plateau, the eastern and western syntaxes receive only ?50% of their annual rainfall during the summer season. Third, snowmelt contributions to discharge differ widely along the range. As a fraction of the total annual discharge, snowmelt constitutes up to 50% in the far western (Indus area) catchments, ?25% in far eastern (Tsangpo) catchments, and <20% elsewhere. Despite these along-strike variations, snowmelt in the pre- and early-monsoon season (April to June) is significant and important in all catchments, although most pronounced in the western catchments. Thus, changes in the timing or amount of snowmelt due to increasing temperatures or decreasing winter precipitation may have far-reaching societal consequences. These new data on precipitation and runoff set the stage for far more detailed investigations than have previously been possible of climate-erosion interactions in the Himalaya.
