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FS 3.128

Upstream-downstream connectivity and impacts in the world’s water towers

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Details

  • Full Title

    FS 3.128: Upstream-downstream connectivity and impacts of climate change in the world’s water towers
  • Scheduled

    TBA
  • Location

    TBA
  • Co-Conveners

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  • Assigned to Synthesis Workshop

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  • Thematic Focus

    Adaptation, Cryo- & Hydrosphere, Hazards, Socio-Ecology, Water Resources
  • Keywords

    Mountains, Climate change, Downstream impacts, Knowledge gaps, Adaptation

Description

Mountains, often referred to as the world’s “water towers”, play an important role in global hydrology and for the provision of water resources. This role is being altered by climate change, impacting amount, timing and quality of mountain runoff. While substantial research has focused on changes in snow and glaciers, a holistic perspective is just emerging that interconnects changes in mountains and related impacts far downstream, where mountain runoff is vital for human use and ecosystems across many regions. For this Focus Session we welcome all contributions at catchment, regional and global scales including reviews that provide new insights on key environmental changes and corresponding impacts on interlinked mountain-lowland water systems and opportunities under climate change. These can include, but are not limited to, surface and groundwater supply, disaster risks, human water use, sediments, water quality, aquatic ecosystems, sea-level rise, human culture, economy and well-being, as well as transboundary water management. At the end of this session we would like to synthesize the presented scientific progress and remaining knowledge gaps, and discuss ways forward to enhance our understanding for urgently needed climate change adaptation.

Submitted Abstracts

ID: 3.5063

Isotope derived snowmelt routing in mountainous basins of western Himalaya, India

Suhail Lone
Jeelani, Gh

Abstract/Description

Himalayan cryospheric waters are a vital freshwater source for billions of people living in upstream and downstream regions, thereby playing a crucial role in sustaining the economic stability of the region. However, these critical water resources face significant threats from climate change, potentially disrupting the region’s economic stability. In this study, we used stable water isotopes (δ¹⁸O and δ²H) to investigate the isotopic evolution of cryospheric water and identify the primary sources of streamflow in snow and glacier dominated high-altitude catchments within the Indus River Basin. Newly deposited snow displayed a notable altitude effect, while surface snow exhibited a reverse altitude effect due to evaporation and sublimation processes. Post-depositional changes in snow led to significant isotopic homogenization of δ¹⁸O and δ²H, with isotopic exchange between firn and percolating meltwater resulting in greater enrichment of heavy isotopes in successive snow layers. Bayesian stable isotope mixing model in R indicated that snowmelt contributed significantly to streamflow in the Indus (63±1.2%) and Shyok (58±1.7%) catchments, while glacier melt dominated contributions in the Nubra (64±2.3%) and Suru (60±2.7%) catchments. Groundwater (baseflow) was found to play a critical role in sustaining river and stream flows during winter and spring, ensuring local water availability. The higher slope and intercept of the snow and glacier melt lines compared to global and local meteoric water lines indicated minimal evaporation. The findings suggest that the region’s spatially diverse, rugged topography and microclimates largely dictate the varying contributions of different sources to river flow. With a warming climate causing decreased solid precipitation, continuous glacier mass loss, and earlier snowmelt, the perennial flow of rivers is likely to be inconsistent, posing significant risks to the region’s economic and political stability.

ID: 3.5368

The Ecosystems boost the Water Security in the Central Provinces of Panama

Alberto Pascual

Abstract/Description

The Santa Maria Watershed, has an extension a territory occupies a total area of 3326 km², with a length total of 168 km, representing 4.56% of the land of Panama. Identified as one of the country’s priority catchments it represents a water source for more than 200,000 people living in 15 Local Governments.

The water that’s flow in the system of rivers is generated by physical, chemical and biological characteristics from mountain, grassland and wetland ecosystems, from the source of the river in the upper part, passing through the urban centers and until it drains into the sea, there are multiple landscapes that intervene, are linked and depend of each biome for work together.

ID: 3.9956

Cascading downstream impacts of climate change in the world’s water towers

Daniel Viviroli
Drenkhan, Fabian; Scott, Christopher A.; Somers, Lauren; van Tiel, Marit

Abstract/Description

Mountains, often called the world’s “water towers” due to their important role in global hydrology and water resources including supply for human uses and ecological processes, are interconnected with lowlands in a system that encompasses both natural resources and society. Climate change in mountain regions affects the amount, timing and quality of mountain runoff, with important downstream consequences. While mountain streamflow and corresponding climate change impacts always travel downstream, these impacts can cascade not only spatially and temporally but also causally across a wide set of social-ecological systems. Additionally, upstream-downstream teleconnections can also have important impacts that shape upstream water tower systems, for example, through infrastructure development based on priorities for downstream users.

We synthesize key environmental changes in mountain regions worldwide into an overview and point at their consequences. These include shifts in surface and groundwater availability, disaster risks, water quality, human water use, sediment transport, aquatic ecosystems, and even sea-level rise. We link these dynamics to social processes, considering culture, economy, and well-being in local and transboundary contexts. Additionally, we highlight feedback mechanisms where downstream activities shape upstream water dynamics, including infrastructure (e.g., hydropower), land and water use (roads, mining, tourism), and conservation (glacier protection, low-impact recreation). Our review underscores the importance of an integrated framework for advancing the understanding of interconnected mountain-lowland systems to inform sustainable water management and policy development in rapidly changing mountain regions and beyond.

ID: 3.10568

Community Vulnerability to Changing Mountain Snowpacks in Canada

Mackenzie Ostberg
Pearce, Tristan; Shea, Joseph; Wigglesworth, Jennifer; Hruby, David

Abstract/Description

Climate change impacts in mountain regions, including decreasing mountain snowpack, are expected to continue and, in some instances, accelerate in the future, requiring communities to undertake adaptations. This research examined community vulnerability to changing mountain snowpacks through a mixed-methods case study of McBride and Dunster villages located in the upper Robson Valley, British Columbia, Canada. Our work is distinct from other mountain climate change studies because it explores the interactions among multiple environmental and societal forces that influence sensitivity to changing mountain snowpack and the capacity to adapt. Local lived experiences were gathered through 25 semi-structured interviews and a focus group with a total of 37 community members and thematically analyzed alongside community documents, local news, and quantitative data on snowpack and streamflow changes. Analysis revealed that residents are sensitive to decreases in mountain snowpack due to their reliance on spring run-off for freshwater. Low water availability has impacted food security, wildfire and structural suppression, and human health and well-being, while the local capacity to adapt has been undermined by the centralization of government services and resulting exodus of local people, along with their knowledge and skills. Despite a long history of coping with fluctuations in weather, recent changes, including low precipitation years related to the Southern El Niño Oscillation and heat waves, are considered by many residents to be outside tolerable ranges. Supporting adaptation is rooted in increasing local social capital and cohesion, which requires directing financial and human resources back into northern communities along with decision-making power.

ID: 3.11532

Global variability and future changes in mountain runoff contributions to lowland water use

Sarah Hanus
Burek, Peter; Smilovic, Mikhail; Seibert, Jan; Wada, Yoshihide; Viviroli, Daniel

Abstract/Description

Mountains play a crucial role in global water resources by generating disproportionally high runoff and delaying its release through snow and ice storage. This study quantifies the contribution of mountain runoff to lowland surface water withdrawal (LSWW) across all river basins larger than 10,000 km² worldwide, focusing on seasonal and interannual variability in the recent past. Additionally, we explore projected changes in lowland-mountain water interactions under climate and socio-economic scenarios.
Our results show that 15% of annual LSWW depend entirely on mountain runoff, with monthly variations ranging from 9% to 23%, highlighting strong seasonal reliance. An additional 51% of annual LSWW can originate from either mountains or lowlands. Under the SSP5-8.5 scenario, the absolute volume of lowland water withdrawal reliant on mountain runoff is expected to rise due to socioeconomic developments. At the same time, its relative share may decline on average in many basins as lowland precipitation increases. However, LSWW exhibits substantial interannual variability, with mountain runoff being most critical in years with low lowland runoff. While relative interannual runoff variability is lower in mountain regions than in lowlands in 70% of river basins, the absolute magnitude of runoff fluctuations is higher in mountain regions in nearly 70% of basins.
Our findings highlight the complex and evolving relationship between mountain runoff and lowland water use and reveal a large heterogeneity across river basins worldwide. Understanding these dynamics is essential for ensuring water security in both mountain and lowland regions as global environmental and socio-economic conditions change.

ID: 3.12479

The impact of melting glaciers and snowpacks on crop production in Asia.

Hester Biemans
Gulpen, Marijn; Mertzanis, Nikos; Lutz, Arthur; Khanal, Sonu; Immerzeel, Walter; Khaniya, Manoj

Abstract/Description

The high mountains of Asia, often called ‘the Third Pole’, store large volumes of water in their glaciers and snowpacks. Twelve large river basins, fed with meltwater from these mountains, are home to almost 2 billion people. In their floodplains, a significant fraction of the global food is produced (34% and 23% of the global rice and wheat production respectively). This makes the ‘Third Pole’ a very important region globally in terms of water reserves on which both water- and food security for a huge population heavily depend.
The water supply from the Third Pole mountains faces many threats. Glaciers and snowpacks are melting at unprecedented rates, and large parts of these reservoirs are likely to disappear by the end of the 21st century. The dependence of downstream populations on mountain water resources is however increasing, mainly due to increasing water needs, continuing groundwater depletion and changes in (monsoon) precipitation.
In this presentation we will show how some of the intensive agricultural systems in Asian river basins depend on the stable and reliable flow of meltwater in specific seasons, when precipitation is absent. We will show how we quantify the links between the water stored in the High Mountains of Asia and the water- and food security of the people living downstream, evaluate how those links will change in the future, and use this understanding to support adaptation design. More in general, this presentation emphasizes the need for a more integrated, holistic approach to assess the impact of changes in the mountains on downstream water users.

ID: 3.12697

Networking: how the river network shapes spatiotemporal drought behavior

Joren Janzing
Wanders, Niko; Verhoeve, Steye; Brunner, Manuela

Abstract/Description

Streamflow droughts evolve in space and time. Such spatiotemporal evolution of streamflow drought is not just driven by changing hydrometeorological conditions, but also by the river network: the drought signal from different tributaries interact as these tributaries merge. However, little is known about the exact role the river network plays in shaping such spatiotemporal drought relationships. Here, we use large-scale hydrological model simulations over Europe to study the role of the river network in shaping spatiotemporal drought relationships in different hydroclimates such as mountain and lowland regions. We apply complex network theory to study drought connections between different river branches. In particular, we focus on the spatiotemporal relationships between upstream and downstream rivers, between droughts in snow and rainfall-dominated rivers and between different river basins. We find that the stream order is important for the drought connectivity between different river branches, whereas the hydroclimatic context can determine where in a basin the drought signal emerges first. As the river network influences the temporal characteristics of the drought signal, this can also influence larger-scale spatiotemporal drought connections between different river basins. Finally, as hydroclimatic conditions are changing due to climate change, we show that such changes can also lead to changes in drought connectivity over time. Our results have implications for water management, as a better understanding of the role of the river network in shaping spatiotemporal drought behavior can help with projecting drought impacts and designing drought impact relief strategies.

ID: 3.13062

Vulnerabilities to Water Supply in the Southern Andes: Land Use, Climate, and Infrastructure Issues

Rolando Célleri

Abstract/Description

Lowland areas depend on water flowing from distant headwater regions, while Andean cities and communities are situated at these headwaters. As a result, they rely on water sourced from small catchment areas, making them particularly vulnerable to shifts in the hydrological cycle and changes in land use. Tropical Andean ecosystems, such as paramo and cloud forests, have historically provided a reliable water supply for downstream communities. However, recent shifts in land cover, land use practices, and erratic weather patterns are increasingly threatening this water supply. This study highlights some of the most urgent challenges to water security in tropical Andean communities, focusing on issues like deforestation, wetland drainage, road construction, rainfall-triggered landslides, and the construction of future dams. The city of Cuenca in the southern Andes will serve as a case study. Additionally, aging water infrastructure combined with rapid urban growth is driving an increased demand for water. This dual pressure is leading to significant conflicts among water users. Addressing these challenges requires an interdisciplinary approach to water and land use management.

ID: 3.13183

Linking Basin Hydrology to Local Water Security in a Transboundary Glacierized Himalayan River Basin

Tejal Shirsat
Boyer, Elizabeth; Hadjimichael, Antonia; Kulkarni, Anil; Taloor, Ajay Kumar; Scott, Christopher

Abstract/Description

Hindukush Himalayan (HKH) region known as the Water Tower of Asia, plays a critical role in assuring water security for billions of people and threatened ecosystems in the Indian sub-continent. Impacts of synoptic-scale changes in climatic conditions, and increasing socio-economic requirements impact the water security in the HKH. Moreover, lack of adequate considerations of local water management practices and values limits our ability to truly understand water security and devise effective solutions. In this regard, the present study aims to connect the basin-scale hydrology to water security in the Chenab River Basin at the local scale of an administrative unit by integrating qualitative and quantitative methods. The Chenab River is a major tributary of the Indus River that originates in the Lahaul range of the Western Himalayas. In this study, we analyzed the hydrological regime of the Chenab River basin having a drainage area of 28,900 km2 and an elevation range of 287 to 7044 m. The basin consists of 2,802 glaciers covering 2,864 km2, implying heavy reliance of the basin’s water security on glaciers and snowpack. The Spatial Processes in Hydrology (SPHY) model was used to estimate basin hydrological regime and contributions of water balance components i.e. snowmelt, glacier melt, rainfall runoff and baseflow/groundwater in the present. The basin hydrology is later linked to local water security by integrating model outputs with household surveys to understand the reliance of downstream villages on the local water resources. This assessment will advance understanding of the basin’s hydrological dynamics and responses at local and regional scales and provide essential insights for holistic water management in this hydrologically and institutionally complex basin.

ID: 3.13951

Constructed Wetlands for bioremediation of Acid Rock Drainage in the Peruvian Andes: Implementation, monitoring and replicability

Vladimir Alfonso León Menacho
Aguirre Falcón, Kiara; Asensi Dasi, Enrique; Hernández Crespo, Carmen; Martín Monerris, Miguel

Abstract/Description

Climate change-accelerated glacial retreat and weathering of rocks with metallic sulphides generate acid rock drainage (ARD), characterised by high concentrations of H⁺, SO₄²-, Fe and other heavy metals. This natural geochemical process is a critical environmental problem in the Peruvian Andes, where ARD impacts water quality and hydrological connectivity from mountain ecosystems to downstream river systems. The community of Canrey Chico, in the Ancash region, is a unique case where ARD directly affects the local population, causing environmental and socio-economic risks due to the use of river water for agricultural and livestock activities. In response to this problem, and under a participatory approach, a Bioremediation Pilot Plant was implemented for research purposes. This plant includes constructed wetlands (CW) with different configurations, both full-scale and prototypes. The objectives of this study were: (1) design and implement CW systems, (2) monitor effluent quality for potential agricultural and livestock reuse, and (3) assess the potential for replicability of these solutions in other areas affected by ARD. The implemented CW are unique systems in terms of the water they treat. They have been designed and implemented with the participation of local people, who have traditional knowledge and an interest in improving water quality. In addition, research is being carried out to optimise these systems. As a result, a significant reduction in the concentration of SO₄²- (27±12%) and heavy metals (Fe: 88±5%, Al: 96±2%, Co: 98±1%, Cd: 79±22%, Zn: 96±2%, Cu: 90±10%, Ni: 98±1%, Be: 71±18%), as well as an increase in pH to 6.37±0.15, which allows the potential reuse of water as established by national legislation. These systems can be optimised and replicated in hydrographic units affected by ARD in the Andes and in other regions of the world with similar problems, depending on the type of water use and the needs of the population.