Mountain Water Research Articles

Investigating the use of hydro-geothermal energy from tunnel drainage system for de-icing roads: results from a pilot study

De-icing roads is a complex process that requires careful consideration of multiple factors, as traditional de-icing methods can have significant environmental and economic impacts. Therefore, the use of sustainable methods such as renewable energy, can potentially help to mitigate some of these issues. In order to investigate this concept, a thorough investigation into the use of hydro-geothermal energy from a tunnel drainage system for preventing the accumulation of ice and snow on traffic areas at the tunnel portals was conducted.
 As part of this investigation, a pilot system consisting of nine fields with underlying heat pipes was constructed being monitored by several temperature sensors and further equipment. The fields utilise the readily available mountain water from the 1.284 m long road tunnel ´Füssen´ at the German/Austrian border as a natural heat source [1], eliminating the need for a heat pump. The sensor readings were then compared to the results obtained from a coupled hydro-thermal numerical model (Figure 1). The model considers all heat fluxes acting on the free surfaces (e.g. short and long-wave radiation), and determines the heat flux density required to keep the ice and snow free by means of the energy balance formed at the surface of the field. The validation of the simulation is carried out on the basis of the measurement data which were recorded in periods in which the external atmospheric boundary conditions can be determined as precisely as possible.A parameter study was also conducted that included different weather conditions, variable field geometry, pipe materials, and surface materials such as concrete, or asphalt, as well as the minimum field activation times, the results of these studies confirmed, among other things, that the utilization of copper pipes results in higher temperatures on the surface of the road [2]. Furthermore, it was determined that an activation time of 9 hours prior to the forecast of a weather event is sufficient to raise the temperature of the road surface to remain ice-free.
 The results of this study provide compelling evidence for the efficacy of the direct, passive outdoor temperature control concept in mitigating snow and ice accumulation on traffic areas adjacent to tunnel portals. This pioneering approach not only safeguards winter safety by maintaining hazard-free surfaces but also presents the opportunity to extend the lifespan of the traffic areas through the implementation of cooling strategies during the summer season. Notably, upon activation, the road surface consistently achieves the necessary temperature to effectively melt snow and ice during moderately intense snowfall within a relatively short timeframe of approximately 5 to 9 hours. These results highlight the practical viability and efficiency of the direct, passive outdoor temperature control method in combatting snow and ice-related challenges.
 
 It was concluded that the findings of this study have yielded positive results and have served as proof of concept for the utilization of hydro-geothermal energy from tunnel drainage systems but also from other sources as e.g. BHE as a viable means of preventing ice and snow accumulation on roads. The data obtained from numerical simulations and measurements were found to be in agreement. This method holds the potential to greatly enhance the safety and accessibility of roads during the winter months, while also reducing the dependence on traditional de-icing methods that can have detrimental environmental impacts, on top of that, the method has an added benefit of being used in the summer to cool down the roads to prevent heat deformations. The results of this pilot project provide a foundation for further research and development in this field, with the ultimate goal of implementing this technology on a larger scale.

Peran Penting Pokdarwis Dan Kualitas Sumber Daya Manusia Desa Carangwulung dalam Pengelolaan Wisata Alam Grojogan Selo Gonggo

The tourism potential in Carangwulung Village is very diverse and has the opportunity to be developed into a tourist attraction. There are eight tourist destinations that have been developed in Carangwulung village, one of which is the Grojogan Selo Gonggo (GSG ) nature tourism. This tourist attraction is natural attractions that come from mountain water and also pine forests. Opportunities for tourism activities at GSG are very good, if the local community and the management are able to work together to achieve the expected goals. However, the fact is that over time the people who participate in managing the GSG experience a decrease in tourism awareness. This will not affect the future development of GSG natural tourism as tourism that is of interest to tourists. Therefore, the awareness of the Carangwulung village tourism community needs to be increased again so that the development of the GSG nature tourism is not in vain and gets maximum benefits from tourism activities. The formation of POKDARWIS and improving the quality of human resources play an important role in developing GSG natural tourism, with the aim of making GSG a tourist destination that is of interest to many tourists.

Unravelling geological controls on groundwater flow and surface water-groundwater interaction in mountain systems: A multi-disciplinary approach

Mountain water resources are considered to be the world’s water towers. Still, despite their importance for downstream societies and ecosystems and their vulnerability to climate change, they remain poorly understood – It is the case in particular of mountain groundwater systems. Their complexity makes them difficult to conceptualize, while their remoteness makes them difficult to study, both observationally and instrumentally. Understanding mountain hydrogeological systems is mostly limited by the lack of characterization of the subsurface geologic framework and by the limited understanding of the role of geological structures on groundwater flow and on surface water-groundwater interaction. Removing methodological barriers is therefore a necessary step for improving the understanding of mountain hydrogeological systems.To tackle this problem, we develop a comprehensive multi-disciplinary approach to gain insights into the hydrogeological role of geological structures in ungauged mountain catchments. The methodology consists of several complementary methods: (1) geological mapping at multiple scales; (2) a geophysical study including on-ground Electrical Resistivity Tomography (ERT) and, gravimetry transects, and a UAV-based magnetic survey; (3) hydraulic data, including a 9 km long transect of streamflow measurements in the recession period, the long-term Normalized Difference Vegetation Index (NDVI), and varied hydric markers (e.g., a thermal spring and a puddle). The methodology is tested in the Parque Nacional del Río Clarillo, an ungauged catchment in the Andes Mountains (≈130 km2) that is illustrative of the complexity of mountain hydrosystems featuring fault zones, weathered zones, intrusive rocks, and volcano-sedimentary successions.An increase of approximately 50% in the streamflow is observed over a short distance of 1 km. Such a localized and significant increase in the baseflow is not related to any superficial supply and can only be explained by groundwater exfiltration. Based on the multiscale geological mapping and geophysical survey, a regional N-S fault and a secondary set of E-W local faults are identified in the vicinity of the resurgence area, which conjointly are likely to export groundwater from a neighbouring subcatchment up to the resurgence area. Downstream of the resurgence area, no significant change in the baseflow is observed, corresponding to the presence of an impermeable granitic pluton identified by the geological and geophysical mapping. Finally, a fractured zone in the Andean foothills is identified in the volcanic unit, which coincides with a perennial thermal spring, indicating upwelling flow and hydrogeological connectivity between the mountain block and the alluvial basin.The results strongly support the ability of the proposed methodology to identify geological structures that substantially impact the evolution of the baseflow through the catchment. The complementary multi-disciplinary methods are used innovatively to infer the link between geological and hydrogeological structures. The methodology does not aim to fully characterize the geological framework of the catchment but pragmatically focuses on hydrogeologically pertinent structures that may impact baseflow and consequently catchment management.

Estimation of Optimum Alum Doses of Mountain Water for Water Supply Treatment in Hill Tribe Villages in Chiang Rai Province, Thailand

Hill tribe villages are located in mountainous and remote areas. Primary water supply and drinking water sources are mountain water from a small weir on the mountain. Most mountain waters found turbidity higher than 1 NTU, and water quality was unclean to use and drink. This research applied different concentrations of alum doses to observe turbidity reduction. Optimum alum does apply to reduce turbidity for mountain water samples from Hmong, Karen, Lahu, and Lisu for three seasons. The optimum alum dose is between 20 - 40 mg/l in rainy seasons and 10 – 40 mg/l in summer. The cold season was low optimum alum dose at 10 mg/l for all hill tribe villages. Therefore, alum coagulants can be used to treat the mountain water supply and drinking that can implement the main problem of mountain water in hill tribe village.

Sensitivities of subgrid-scale physics schemes, meteorological forcing, and topographic radiation in atmosphere-through-bedrock integrated process models: a case study in the Upper Colorado River basin

Abstract. Mountain hydrology is controlled by interacting processes extending from the atmosphere through the bedrock. Integrated process models (IPMs), one of the main tools needed to interpret observations and refine conceptual models of the mountainous water cycle, require meteorological forcing that simulates the atmospheric process to predict hydroclimate then subsequently impacts surface–subsurface hydrology. Complex terrain and extreme spatial heterogeneity in mountainous environments drive uncertainty in several key considerations in IPM configurations and require further quantification and sensitivity analyses. Here, we present an IPM using the Weather Research and Forecasting (WRF) model which forces an integrated hydrologic model, ParFlow-CLM, implemented over a domain centered over the East River watershed (ERW), located in the Upper Colorado River basin (UCRB). The ERW is a heavily instrumented 300 km2 region in the headwaters of the UCRB near Crested Butte, CO, with a growing atmosphere-through-bedrock observation network. Through a series of experiments in the water year 2019 (WY19), we use four meteorological forcings derived from commonly used reanalysis datasets, three subgrid-scale physics scheme configurations in WRF, and two terrain shading options within WRF to test the relative importance of these experimental design choices for key hydrometeorological metrics including precipitation and snowpack, as well as evapotranspiration, groundwater storage, and discharge simulated by the ParFlow-CLM. Our hypothesis is that uncertainty from synoptic-scale forcings produces a much larger spread in surface–subsurface hydrologic fields than subgrid-scale physics scheme choice. Results reveal that the WRF subgrid-scale physics configuration leads to larger spatiotemporal variance in simulated hydrometeorological conditions, whereas variance across meteorological forcing with common subgrid-scale physics configurations is more spatiotemporally constrained. Despite reasonably simulating precipitation, a delay in simulated discharge peak is due to a systematic cold bias across WRF simulations, suggesting the need for bias correction. Discharge shows greater variance in response to the WRF simulations across subgrid-scale physics schemes (26 %) rather than meteorological forcing (6 %). The topographic radiation option has minor effects on the watershed-average hydrometeorological processes but adds profound spatial heterogeneity to local energy budgets (±30 W m−2 in shortwave radiation and 1 K air temperature differences in late summer). This is the first presentation of sensitivity analyses that provide support to help guide the scientific community to develop observational constraints on atmosphere-through-bedrock processes and their interactions.

Kontaminasi Escherichia coli pada Air Minum Isi Ulang di Wilayah Ciangsana Menggunakan Uji Most Probable Number (MPN)

Water is a basic need for humans. Human life cannot be separated from water, especially the need for drinking water. Water needs have been sourced from groundwater, river water, rainwater, mountain water, and treated seawater. Water that humans need includes clean and healthy useable water for cooking, washing, and bathing, as well as water that is fit for consumption for drinking purposes. The main use of water and very vital for life is the use of drinking water. Drinking water from depot companies for drinking water refills is an industrial business that processes raw water into ready-to-drink water by consumers. This study aims to determine the presence of Escherichia coli contamination in drinking water sold by refilled drinking water depots in the Ciangsana region. The results of the microbiological analysis showed two out of ten samples were positive for coliform fecal, Escherichia coli.

Sewage system diagnosis based on online monitoring technology

ABSTRACT External water (such as rainwater, mountain water and groundwater) will decrease the inflow contaminant concentration in urban sewage plants, and pose challenges in improving the wastewater treatment quality and efficiency. Therefore, removing the external water is vital for this target. A sewage plant in Zhuhai, China, was considered as an example. By performing online flow monitoring, water quality testing, on-site survey and data analysis, the rainfall-derived inflow and infiltration of the sewage system were quantitatively analysed through the pollutant balance method. By proposing key emphases of severe problems, the presented findings will aid in sewage system maintenance and pipeline network renovation.

Disproportional vulnerability of mountain aquatic invertebrates to climate change effects

ABSTRACT Mountain freshwater communities are generally considered sensible to accelerated climatic changes, though their vulnerabilities have not been well evaluated. Individual species or species groups are expected to respond differently depending on their adaptations, traits, or distributions, but this has not yet been distinguished. This work used available climate change vulnerability scores (ccvs) of European Ephemeroptera, Plecoptera, and Trichoptera (EPT) species (n = 1,402) to (1) compare the vulnerability between species pools of different ecoregions including alpine species and alpine endemics, (2) contrast the vulnerability between the different insect orders, and (3) assess the altitude–vulnerability relationship within the European Alps. We revealed fifty alpine Plecoptera and Trichoptera species that are categorized highly vulnerable to climate change effects (= 31 percent of all highly vulnerable European species) with the highest proportions in species inventories of alpine endemics and high-altitude waters (51 percent of high-altitude species are classified as highly vulnerable). The ccvs analysis specifically for mountain waters shows that a disproportionately high number of alpine species, and particularly alpine endemics, will be affected by climate change and suggests that Ephemeroptera may be better prepared than Plecoptera and Trichoptera. Thus, this trait-based evaluation suggests that mountain stream invertebrate communities are undergoing disproportionate restructurings in response to climate change effects more than lowland communities are.

HeadwaterstreamSNevada: Data on riparian vegetation and water parameters of headwater streams in Sierra Nevada, Spain.

Providing historical data on riparian plant biodiversity and physico-chemical parameters of stream water in Mediterranean mountains helps to assess the effects of climate change and other human stressors on these sensitive and critical ecosystems. This database collects data from the main natural headwater streams of the Sierra Nevada (southeastern Spain), a high mountain (up to 3479 m above sea level [m asl]) recognized as a biodiversity super hotspot in the Mediterranean basin. On this mountain, rivers and landscapes depend on snowmelt water, representing an excellent scenario for evaluating global change's impacts. This dataset covers first- to third-order headwater streams at 41 sites from 832 to 1997 m asl, collected from December 2006 to July 2007. Our goal is to supply information on the vegetation associated with streambanks, the essential physico-chemical parameters of stream water, and the physiographic features of the subwatersheds. Riparian vegetation data correspond to six plots sampled at each site, including total canopy, individual number, height and DBH (diameter at breast height) in woody species, and cover percentage for herbs. Physico-chemical parameters were measured in situ (electric conductivity, pH, dissolved O2 concentration, stream discharge) and determined in the laboratory (alkalinity, soluble reactive phosphate-phosphorus [SRP], total phosphorus [TP], nitrate-nitrogen [ -N], ammonium-nitrogen [ -N], total nitrogen [TN]). Watershed physiographic variables comprise drainage area, minimum altitude, maximum altitude, mean slope, orientation, stream order, stream length, and land cover surface percentage. We recorded 197 plant taxa (67 species, 28 subspecies, and 2 hybrids), representing 8.4% of the Sierra Nevada vascular flora. Due to the botanical nomenclature used, the database can be linked to FloraSNevada database, contributing to Sierra Nevada (Spain) as a laboratory of global processes. This data set can be freely used for non-commercial purposes. Users of these data should cite this data paper in any publications resulting from its use.

Melting Alpine Water Towers Aggravate Downstream Low Flows: A Stress‐Test Storyline Approach

AbstractDroughts can lead to extreme low flow situations in rivers, with resulting severe impacts. Upstream snow and ice melt in many of the world's mountain water towers can alleviate the hydrological consequences of drought, yet global warming threatens the cryosphere. To improve the understanding of melt water contributions during drought in the case of future glacier retreat, we developed stress‐test storyline scenarios to model streamflow and tested them in the European river Rhine basin. Meteorological conditions of past drought and low flow years in Europe, 1976, 2003, and 2018, were repeated at three future moments in time, representing nowadays, near future and far future conditions. The latter two conditions were obtained by climate projections under the RCP8.5 scenario. Results show that the low flow situations caused by the meteorological drought situations aggravate in future conditions, more so for the far future and for the year 2003 because of the relatively large glacier ice melt contribution in the past. Summer (July–September) streamflow may decline by 5%–25% far downstream and 30%–70% upstream and the duration of extreme low flow situations may double compared to the selected past drought events. These results are relevant for the Rhine as a major European river but stand exemplary for many other river basins and highlight the importance of cryospheric changes for downstream low flow situations in a changing climate. The stress‐test scenarios allow a glimpse into future extreme low flow events aiding adaptation planning, and might be adapted to include other important low flow drivers.

Investigating the origin of solutes in rock glacier springs in the Swiss Alps: A conceptual model

In the current context of climate change, rock glaciers represent potentially important water resources due to the melting of ice they contain and/or their role as high mountain water reservoirs. However, the hydrology of these high-altitude debris accumulations is poorly known. Understanding the origin and quality of rock glacier outflows is essential to evaluate their contribution and impact on headwater systems. In this study, we developed a conceptual model explaining the main hydro-chemical processes in active rock glaciers in the current context of permafrost warming. This conceptual model was derived from isotopic and physico-chemical analyses performed on six rock glacier outflows in the Swiss Alps during the warm season. Similar chemical and isotopic analyses were performed in sources not fed by rock glaciers at all study sites. The ion content (SO42-, Ca2+, Mg2+ and NO3−) of the water emerging from active rock glaciers was globally higher than that of sources not fed by rock glaciers. Besides, the electrical conductivity and the ion content (SO42-, Ca2+ and Mg2+) of the active rock glacier springs increased during the warm season, tracking the increasing perennial ground ice melting. We hypothesized that the ionic fingerprint of melting ice points mainly to the remobilization of chemical compounds stored during a colder period of the past in the cryosphere (e.g., the 1960s–1980s).

A Robotic Tunnel Drainage Inspection Rover

Drainage pipes in tunnels are very complicated to service but still need rather frequent inspections in order to detect the initiation of deposited scales stemming from carbonate that tends to precipitate when the pH-value of the mountain water rises with the release of gaseous carbon dioxide CO2 due to a decreasing water pressure. The drainages enable to design tunnels without resistance to ground water pressure. We present the development of a robot able to autonomously navigate through tunnel drainage pipe systems inspecting for these carbonate scale deposits, and can demonstrate that the currently available test platform is able to traverse autonomously, in between two recharging stops in manholes, a few hundred meters of tunnel pipes thereby acquiring on a localized basis various environmental parameters like pH-value, the water's conductivity, temperature, carbon dioxide concentration in addition to documenting the pipes’ condition with respect to scaling via a video clip that is recorded along with an estimated position in the pipe.

STUDY ON THE SPATIOTEMPORAL DIFFERENTIATION CHARACTERISTICS OF “MOUNTAINS, RIVERS, FORESTS, FIELDS, LAKES, AND GRASS CITIES” IN THE TAI’AN SECTION OF THE YELLOW RIVER BASIN

The natural environment of the Tai’an section of the Yellow River Basin is complex and diverse, the land use function and structure have distinct regional and cultural characteristics. This article is based on literature review, field research and remote sensing image interpretation to construct an analysis variable database. Based on models such as land use dynamics and transfer matrix, the spatiotemporal differentiation and variation characteristics in this area are analyzed. Discovery: ①As a representative area with significant natural background characteristics of “mountain water field”, forest land, cultivated land, and water bodies constitute the main matrix and corridor of land use. ②Over time, the distribution and composition of the spatial distribution in the Tai’an section of the Yellow River Basin have undergone significant changes. The proportion of arable land, forest land and grassland areas to the total land use area has decreased overall, the proportion of building land, water bodies, and unused land has increased. Over 20s, the spatial distribution structure and composition in the study area have undergone significant changes. ③Between 2000 and 2020, cultivated land and construction land constituted the main body and background of land use conversion in this area. This study can provide reference for promoting the coordinated development in the Tai’an section of the Yellow River Basin.

Dynamic changes in soil moisture in three typical landscapes of the Heihe River Basin

The water diversion scheme of Heihe River Basin was implemented in 2000. Herein, we investigated the dynamic changes in soil moisture content and analyzed the fundamental reasons supporting the water diversion plan in this typical inland river basin in northwest China. Accordingly, we selected three typical landscape gradients—a mountain water conservation forest belt, an artificial sand-fixing forest belt at the edge of a desert oasis, and a desert riparian forest belt in the upper, middle, and lower reaches of the Heihe River Basin, respectively. In these diverse landscapes, an environmental measuring system was used to continuously monitor the dynamic and differentiation regularity of soil moisture in the 0–160 cm layer for 5 years. The results revealed that 1) the soil moisture content in each landscape increased and varied significantly across seasons. In the upper and middle reaches, the soil moisture content was significantly higher during the growing season than in the non-growing season, whereas the lower reach displayed a converse pattern. 2) The distribution of soil moisture at various depths of soil profiles varied significantly for each landscape. As the soil depth increased, the soil moisture in the upper reach decreased. Although the deep layers (120–160 cm) could store water in the non-growing season, the stored water was consumed during the growing season. The soil moisture content in the mid-reach initially increased, later decreased, and ultimately attained its highest level at 40–60 cm; however, the soil moisture content in the lower reach increased, and reached its highest level at 120–160 cm. 3) In the upper and middle reaches, the coefficient of variation of soil moisture decreased with an increasing soil depth, whereas the lower reach exhibited a converse trend. Similarly, the coefficient of variation of soil water storage were higher during the non-growing season than during the growing season within the upper and middle reaches, whereas an opposite trend was observed in the lower reach. 4) Since the implementation of the Heihe river water diversion plan, the soil moisture content in both the upper and middle reaches have increased but that of the lower reach has fluctuated and declined, especially in the shallow depths during the growing season. The present findings imply that the lower reaches of the Heihe River may require additional water transfers during the growing season.

Postseismic mountain aquifer leakage drives multi-annual forearc basin recharge in the Atacama Desert

In response to a 7.8 Mwb earthquake in June 2005 in the hyper-arid Atacama Desert, postseismic mountain aquifer leakage was triggered at several sites. By creating data-driven models for selected water level time series, previously unconsidered processes of postseismic mountain aquifer leakage are analysed. Post-event lag-time changes imply that the hydraulic conductivity of the assessed mountain aquifer doubled in response to the earthquake, initiating a multi-year period of augmented mountain-block recharge to the forearc basin. An estimate of the magnitude of mountain water releases after June 2005 suggests that released storage water exceeded the recharge provided by a 100-year rainfall event fourfold. During an observation period of 43 years two such events likely occurred in the study area. The frequency of postseismic mountain aquifer leakage, its contribution to draining eventual head decays in the Atacama Desert as well as its importance for forearc basin water budgets are discussed.

Looking beyond glaciers to understand mountain water security

Looking beyond glaciers to understand mountain water security

Identification and Construction of Ecological Nodes in the Fuzhou Ecological Corridors

Ecological corridor construction is an important support of the current pursuit of high-quality urbanization. Fuzhou is a mountain–water city characterized by a unique spatial structure. However, rapid urbanization has exacerbated the rate of ecosystem fragmentation, negatively impacting the livable living environment. The construction of ecological corridors is of great significance for efforts to restore the broken landscape and form the urban ecosystem as an organic whole in Fuzhou. In the present study, Fuzhou was considered as the study area, and the water, green, and ventilation corridors, as well as surface temperature data, were analyzed using the kernel density analysis method to generate surface-temperature-based ecological nodes. The impacts of various corridors and surface temperatures on the construction of the Fuzhou ecological corridors were assessed using ecological theory, and the ecological resistance surfaces of the influencing factors were obtained. We constructed ecological corridors for the mitigation of the urban heat island in Fuzhou using the MCR model with four levels and then evaluated the network connectivity of the corridors. The results revealed the following findings: (1) The study area comprises 32 ecological nodes, including nine in Minhou County and Changle District, four in Mawei and Cangshan Districts, and two in Gulou, Taijiang, and Jin’an Districts. (2) Fuzhou contains 63 ecological corridors with a total length of approximately 494.65 km. These include 31 first-level (201.16 km), 11 second-level (98.56 km), 14 third-level (129.12 km), and 7 fourth-level (65.81 km) corridors. (3) The degree of closure (α), the point rate of lines (β), the degree of connectivity (γ), and the degree of connectivity (Cr) indexes of the network structure for the ecological corridors were 0.27, 2.03, 0.72, and 0.87, respectively. They indicate that the overall ecological effectiveness of the network is high and can provide a theoretical basis for the construction of ecological corridors in the future.

Implementation of household-scale clean water treatment technology for the mountain farming community, Jajar village, Gandusari district, Trenggalek

Currently, the need for clean water which is a vital source for people's lives has not been fully met for all Indonesians, including the mountain farming community, Jajar Village, Gandusari District, Trenggalek Regency. So far, the mountain farming community members of Jajar Village have used mountain water for household needs where cloudy and unstable water conditions are a problem that must be faced. If this problem continues, it will lead to serious health problems and social conflicts in the community. Therefore, through community service activities, we made a practical clean water treatment tool, with easily obtained materials, that can be implemented in hilly areas such as in Jajar Village, Gandusari District, Trenggalek Regency. The filtration system used is an upflow and downflow system where the water undergoes a filtration process twice in the material that has been selected and arranged in a systematic way. The materials used are available and easy to obtain in Jajar Village, so that people can discover easily about the benefits of these materials. After making a water filtration system with the community, then physical testing is conducted on the quality of the water produced. From the test results of the effectiveness of the implementation of clean water treatment technology applied to mountain farmers in Jajar Village, it shows that in general the filtered water has met the physical requirements for the level of turbidity, taste, and smell, as well as the quantity and continuity of water are always available when needed.

Protecting the Mountain Water Towers of Spain’s Sierra Nevada

Students and community members monitor the health of mountain water reserves, which capture and release water, evening out wet and dry periods downstream.

Warming-induced monsoon precipitation phase change intensifies glacier mass loss in the southeastern Tibetan Plateau

Glaciers are key components of the mountain water towers of Asia and are vital for downstream domestic, agricultural, and industrial uses. The glacier mass loss rate over the southeastern Tibetan Plateau is among the highest in Asia and has accelerated in recent decades. This acceleration has been attributed to increased warming, but the mechanisms behind these glaciers' high sensitivity to warming remain unclear, while the influence of changes in precipitation over the past decades is poorly quantified. Here, we reconstruct glacier mass changes and catchment runoff since 1975 at a benchmark glacier, Parlung No. 4, to shed light on the drivers of recent mass losses for the monsoonal, spring-accumulation glaciers of the Tibetan Plateau. Our modeling demonstrates how a temperature increase (mean of 0.39 ∘C ⋅dec-1 since 1990) has accelerated mass loss rates by altering both the ablation and accumulation regimes in a complex manner. The majority of the post-2000 mass loss occurred during the monsoon months, caused by simultaneous decreases in the solid precipitation ratio (from 0.70 to 0.56) and precipitation amount (-10%), leading to reduced monsoon accumulation (-26%). Higher solid precipitation in spring (+18%) during the last two decades was increasingly important in mitigating glacier mass loss by providing mass to the glacier and protecting it from melting in the early monsoon. With bare ice exposed to warmer temperatures for longer periods, icemelt and catchment discharge have unsustainably intensified since the start of the 21st century, raising concerns for long-term water supply and hazard occurrence in the region.