The working group on “Climate Impacts on Global Mountain Water Security” will address the issues of climate and cryospheric change, and the associated impacts to hydrological functioning and water resources within and downstream of mountain regions globally. The group links strongly to the International Network for Alpine Research Catchment Hydrology (INARCH; http://www.usask.ca/inarch/), which is a cross-cutting project of the World Climate Research Programme’s Global Energy and Water Exchanges (GEWEX) Project. It is also supported by the Mountain Water Futures (MWF) project of the Canadian Global Water Futures (GWF) programme http://www.mountainwaterfutures.ca/. The Grand Challenge that this working group addresses is: how to develop a global scientific approach to better understand, predict and manage alpine water resources in the face of dramatically increasing risks? Three core questions that are central to meeting this Grand Challenge are: (1) What control does climate change have on the security of mountain water? (2) What improvements to the global predictability of mountain water resources are possible through improved models? (3) How do changes in snow, glaciers, frozen ground and vegetation impact mountain water resource predictions? The team has a network of well-instrumented mountain research basins around the world. All of these research basins have weather, snow, glacier and water observations over multiple years and have some predictive models run at various scales. The headwater basins also have local mountain communities that are directly impacted by local water cycling. These observations are embedded near the headwaters of larger river basins that supply water for vast downstream populations. Through affiliating with Future Earth, this group proposes to bring in the human aspects of mountain water cycling – dams, irrigation, upstream water values and use, ecosystem services. There are many indigenous peoples or minority cultures in mountain headwaters and this group will examine water management through their lens, as well as the more traditional consideration of downstream water, uses for communities, agriculture and energy.
Mountain headwater catchments receive and produce a disproportionately large fraction of global precipitation and streamflow, including contributions to floods and essential water supplies for vast downstream areas that include at least one-half of humanity. Mountain snowcover and glaciers also have important atmospheric feedbacks via albedo and surface temperature and are involved in maintaining distinctive local and regional scale cold climates, even in high insolation seasons. Because they lack long-term storage, seasonal snowpacks respond rapidly to climate variability, change and weather extremes – however their seasonal dynamics can be coupled to the long-term dynamics of alpine permafrost and glaciers under climate warming. Ongoing climate warming has already resulted in shorter seasonal snowcover duration, glacier wastage, earlier rise in spring hydrographs, reduced streamflow volume contribution from snowmelt, increases in icemelt and higher frequency of rain-on-snow floods, with follow-on impacts on glacier mass balance, mountain floods, changes in the timing and volume of mountain-derived streamflow and vegetation community change in response to shorter snow-covered season and glacier retreat. As well, mountain communities face threats to their water security from changes to climate and water cycling including flooding and wildfires. The downstream demand for water also means that many mountain communities have been and may be displaced for reservoir development and impacted by water diversions. Even though they are upstream they do not have security of their water supply. The situation is worse downstream, where transboundary waters have little or poor security in some cases, depending on the nature and operability of agreements on sharing waters.
The IPCC WG II Report (2014) suggests that “In many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in terms of quantity and quality.” Understanding the sensitivity of hydrological processes to climate change in high elevation snowy and glacierized headwater catchments is therefore of paramount importance to improving our ability to understand and predict global climate, ecology and water system changes. Such sensitivity may be seriously affected by the specific climate conditions of the different mountain regions that lead to different contribution of the various components of energy and mass balance of the snowpacks and glaciers.
Mountains catchments play a globally important role supplying water for the world, yet the monitoring and modelling of such regions is complex due to poor accessibility, limited data availability and the lack of simulation models that address key glacio-hydrological processes with sufficient detail. Rain-on-snow melt events can generate floods that are highly destructive (e.g. Calgary, 2013) and often poorly predicted because of their complex method of formation and reliance on the temporal and spatial coincidence of substantial snowpacks and intense rainfall. Glacier dynamics are well understood but are not well coupled to snowcover and hydrological understanding. Glacial lake outburst floods are highly destructive in many high mountain regions but have poor predictability due to incomplete understanding of causal mechanisms. There is a need to better understand the processes and characteristics of rain-on-snow and glacial lake outburst floods, how snow/glacier hydrology observations and models can be improved and how snow interactions with vegetation cover impacts hydrological response. Recent advances in the understanding of high altitude meteorology, glacier mass balance and surface properties, behaviour of debris-covered glaciers, feedbacks between the cryosphere and atmosphere and seasonal differences and changes in runoff composition need to be incorporated into predictive models to better define the future of mountain water resources. Uncertainties and deficiencies in atmospheric data, and snow, glacier and hydrological models are primary challenges to accurate estimation of snow and ice melt, and the consequent hydrological response.
How to develop a global scientific approach to better understand, predict and manage mountain water resources in the face of dramatically increasing risks?
It is important to better understand mountain cold regions hydrological processes, improve their prediction and find consistent measurement strategies. It is hence necessary to develop transferable and validated model schemes of different complexity that can support research in data sparse mountain areas. This leads to the following research questions:
What control does climate change have on the predictability, uncertainty and security of mountain water?
What improvements to the global predictability of mountain water resources are possible through improved physics, downscaling, data collection and assimilation in models?
How do transient changes in perennial snowpacks, glaciers, ground frost, and vegetation impact mountain water resource predictions?
Activities and Outputs:
The working group, in collaboration with and as part of the broader INARCH and MWF of GWF communities, will engage in and support field-based research, and model development, testing, and application activities to address the grand challenge and questions above. Specific modelling activities will focus on impacts within high mountain regions and on river systems, and will include:
Assembling climate change scenarios and hydrological model forcing data;
Setup, testing, calibration/validation, and scenario generation for atmospheric and hydrological models over various high mountain regions globally, including climate model downscaling and bias correction;
Running climate scenarios/sensitivity analyses, and linking these to hydrological models to examine impacts on water availability (e.g. timing, magnitude, and duration of flows) and better understand and predict water management concerns.
Relating these results to water security of mountain communities, impact on mountain cultures and ecosystem services and to downstream water use for communities, energy and food.
Key hydrological models to be used include fine-scale, physically based models such as the Cold Regions Hydrological Model (CRHM; www.usask.ca/hydrology/CRHM.php) platform, developed at the University of Saskatchewan’s Centre for Hydrology, and larger regional scale models such as the Modélisation Environmentale Communautaire (MEC) – Surface and Hydrology (MESH) model developed and maintained by Environment and Climate Change Canada (ECCC). The Weather Research and Forecasting (WRF) model, developed at the US National Center for Atmospheric Research (NCAR) is a state of the art atmospheric model that will be used for generating climate change scenarios and providing driving data for land surface and hydrological model applications.
This working group will collaborate with local research scientists and decision-making/water management entities to improve understanding and prediction of the changing alpine climate, cryosphere, terrestrial ecosystems, and water cycling, as well as extreme events. Specific mountain regions of initial focus include the southern Andes (Chile and Argentina), the high mountain regions of Asia including the Hindu-Kush-Himalaya and Tibetan Plateau (supplying water to China, India, Nepal, Tajikistan, Pakistan, Afghanistan, Bhutan, and Bangladesh), parts of the European Alps and the Pyrenees, the North American Cordillera, potentially others such as the New Zealand Alps, African Atlas Mountains, Torngats, Pamirs and others around the world.
The significance of the proposed grand challenge is emphasized by the fact that half of the global population receives water from alpine catchments. This working group will contribute to the goals of INARCH and Global Water Futures, and will link to many other international initiatives such as GEWEX, the High Mountain initiative of WMO and the International Hydrological Programme (IHP) of UNESCO. In doing so, the group will have important global impact as it directly addresses concerns raised by the UN IPCC Working Group II Report (2014) outlined in the motivation above.
John Pomeroy (Chair), University of Saskatchewan, Saskatoon, SK, Canada
Matthias Bernhardt, University of Natural Resources and Life Sciences (BOKU), Wien (Vienna), Austria
Sean Carey, Principle Investigator, GWF Mountain Water Futures, School of Geography and Earth Sciences, McMaster University, Hamilton, ON, Canada
Pablo Dornes, Universidad Nacional de la Pampa, Santa Rosa, Argentina
Masaki Hayashi, Department of Geoscience, University of Calgary, Calgary, AB, Canada
Xin Li, Cold and Arid Regions Environmental and Engineering Research Institute (CAREERI), Chinese Academy of Sciences (CAS), Lanzhou, China
Ignacio Lopez Moreno, Institute for Pyrenean Ecology (IPE), Spanish National Research Council (CSIC), Zaragoza, Spain
James McPhee, Department of Civil Engineering, University of Chile,
Brian Menounos, Department of Geography, University of Northern British Columbia,
Prince George, BC, Canada
Pradeep Mujumdar, Indian Institute of Science, Bangalore, India
Alain Pietroniro, Water Survey of Canada, Environment and Climate Change Canada,
Saskatoon, SK, Canada