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Of Crops, Climate, Canals, and the Cryosphere
UNH leads a National Science Foundation project to assess how climate-, and human-driven change in hydrology will impact agricultural production and land use around Earth’s “third pole”

THIS IS BIG science. Just read the title of the successful National Science Foundation proposal recently won by EOS researchers: “Crops, Climate, Canals, and the Cryosphere in Asia; Changing Water Resources Around the Earth’s Third Pole.”

The third pole is the vast Tibetan Plateau, also sometimes called "the roof of the world.” It is the planet’s biggest and highest plateau at 2.5 million square kilometers (about four times the size of Texas) and at an average elevation of 4,500 meters or about 2.8 miles. It has the biggest ice fields outside of the Arctic and Antarctic and has warmed some 1 to 2 degrees Celsius over the past several decades – a rate similar to most of northern Eurasia and northern North America.

third pole  
The Earth's Third Pole represents the largest and highest collection of mountain ranges in the world. Rivers originating here, fed by glacier and snowmelt, extend in all directions and connect these cold mountain regions with many countries around the Pacific Rim, the Indian Ocean, and Central Asia.  These rivers supply the irrigation water critical for extensive crop production and provide regional food security.
Map by Dominik Wisser, EOS-WSAG.

Like all the high, icy domains of Earth, the third pole serves as a “water tower of humanity” and as the planet warms and climate changes in such regions, a looming water crisis is predicted in the wake of receding glaciers, thawing permafrost, and changes in precipitation patterns. Water is projected to be the issue of the 21st century.

The study area of the project awarded to scientists in EOS’s Complex Systems Research Center spans 18 countries and encompasses all of Central, South, East, and Southeast Asia where some 1.3 billion people depend upon the waters that spring from the Tibetan Plateau to sustain life.

The $1.5 million multidisciplinary, multi-institution study will be an assessment of current and projected water resources in the watersheds of the region’s major rivers, principally the Indus, Ganges, Brahmaputra, Salween, Mekong, Yangtze, Yellow, Amu Darya, Syr Darya, and Irtysh rivers.

Non-sustainable water use ultimately reduces food and water security in these countries, making them more vulnerable to climate variability and change and socioeconomic instability – all elements under the study’s purview.

Given all that, it’s not surprising to hear the project’s lead scientist, CSRC’s Steve Frolking, characterize the task ahead as “enormously daunting.”

Frolking, along with CSRC colleagues Changsheng Li, Richard Lammers, and Dominik Wisser were awarded $827,492 from the NSF to lead the project, with the balance divided among three other collaborating institutions.

Because the aim of the study is to uncover implications for regional food security and economic welfare in the coming decades, it will incorporate economic modeling into the mix – a first for CSRC researchers and part of a growing mandate from funding agencies to integrate physical and social sciences in large research projects with broad impact.

tibet nasa image
  Asia’s Tibetan Plateau contains the world’s largest persistent
ice mass outside of the Arctic and Antarctica. NASA’s Terra
satellite captured this image showing part of a glacier-capped
mountain chain about 110 kilometers (70 miles) west-northwest
of the Tibetan city of Lhasa.

Courtesy of NASA.

“This approach is becoming a bigger part of global change analysis, where you look at the physical or ecological system and also the role humans play as part of that system,” Frolking says. Such an approach, he believes, is part of a trend to ensure “the science is relevant.”

The integrated assessment, which is part of NSF’s new Water Sustainability and Climate program, will also involve team members from the University of Alaska-Fairbanks, Penn State, and Boston University.

The study combines future climate projections, remote sensing and hydrological data together with hydrological, geophysical, agroecosystem, and economic modeling to characterize the relative importance of local precipitation, runoff, groundwater mining, interbasin water transfers, and agricultural and non-agricultural water use for the region's water supply-demand balance.

Daunting indeed.

Breaking new ground
To tackle so large an issue from a single-discipline approach would be impossible, but the blending of physical and social sciences in particular presents uncharted territory for researchers.

Says Frolking, “NSF's requirement to integrate physical and social sciences provided a great opportunity to explore the economic aspects here. The challenge for all of us is that we are generally accustomed to working only within our own specific disciplines, but disciplinary analysis is not enough to address issues of this scope.”

To be successful, Frolking adds, the researchers from different disciplines will “have to learn how to communicate across those divisions. We really don’t know how to do that very well and we don’t know how to do integrated assessments, it’s not a very well-developed enterprise.”

For the study, UNH researchers will focus on modeling the agricultural and water cycle components using a global ecosystem model developed at CSRC and a hydrological model created by researchers in the Water Systems Analysis Group, or WSAG, respectively. (Lammers, Wisser, and Frolking are members of WSAG.)

Scientists from the University of Alaska-Fairbanks will do glacier melt and permafrost modeling. An economist from Penn State will do economic modeling and team members from Boston University will do remote sensing and economic modeling.

The DeNitrification-DeComposition or DNDC model, which has been developed by project co-investigator Changsheng Li and colleagues over the last two decades, will be used to estimate crop yield and water requirements. The model has been adapted to function in vast regions of the globe and, today, there is a DNDC model specific to Canada, the UK, Europe, China, and New Zealand.

Notes Frolking, “The DNDC component can obviously be run at a large scale and it allows us to estimate how much water is needed to grow food.”

Just this past October, the Chinese Academy of Hydrological Sciences adopted the DNDC as a core model to develop a Crop Production Warning System for predicting reduced crop productivity caused by droughts. Shortage of irrigation water is becoming an alarming issue across most of northern and western China where drastic climate change is occurring.

According to Li, based on official reports and DNDC modeling results, upland crop production in China was highly variable over the past 15 years in comparison with relatively stable yields during the 1980s and early 1990s. The reasons are not yet clear, but the modeled data indicate the most serious depressions in crop yields in 1997, 2000, and 2005 in northeastern China were related to extremely low precipitation in those years.

“Water for irrigation is decreasing in the western highland regions due to the degradation of glaciers and the construction of new dams,” Li says, “and the groundwater table has dropped rapidly and threatens the major food producing enterprises in the North China Plains.”

The project will also benefit from Li’s connections with scientists in his homeland, which, among other things, should help in tracking down potentially hard-to-obtain data such as river gauge flow measurements.

Moving hydrological data “downstream”
The Water Balance Model developed by WSAG has the capacity to keep track of water over a landscape as big as the third pole. This includes all aspects of water management/redistribution such as irrigation, municipal and industrial use, or pumping water from one watershed to another – the latter being a prevalent practice in the western U.S. where water crises are already occurring. China and India have several huge water diversion projects on the drawing board.

Moreover, WSAG’s model will be able to take climate change scenarios and project how the region might look well into the future with respect to the availability of freshwater for all purposes, including growing food. “And that’s a huge piece,” Frolking says, “in a sense it’s the core element of the whole project.”

tibet nasa image
  Soaring, snow-capped peaks and ridges of the eastern Himalayas create an irregular white-on-red patchwork between major rivers in southwestern China. The Himalayas are made up of three parallel mountain ranges that together extend more than 2900 kilometers.
    Image courtesy of USGS National Center for EROS and NASA Landsat Project Science Office.

Says Richard Lammers, project co-investigator and co-director of WSAG, “What we bring to the project is a modeling and data processing framework that has been developed over many years, and which allows us to go to any part of the world and run the hydrological simulation models to get a macroscale view of that area’s hydrology and water movement.”

In other words, like the DNDC, it is a powerful and flexible model that is generic enough to simulate nearly any global hydrological environment. The model has specific sub-models that incorporate irrigation (the single largest water use globally), impoundment, and diversion.

As Lammers explains, the model takes all this varying data and “moves it downstream” through time to derive potential scenarios in the future.

“We will create time-series maps of how much water there is in the rivers and this will allow us to say, for example, ‘Twenty years from now water will not be available downstream beyond a certain point, which will mean that nation will not be able to irrigate crops in that area.’”

Lammers notes that the project will use the “loosely coupled models” in sequential fashion. For example, the modelers from the University of Alaska-Fairbanks will run their glacier melt model for the Himalaya driven by the Intergovernmental Panel on Climate Change forecasts, or some regional predictions if available. The outcome of that model run would be adapted to the hydrological model and then, using the same IPCC climate drivers, “we’d move that data downstream to get the results,” says Lammers. This same process would, in turn, be done using the DNDC and, finally, economic models.

The project’s biggest challenge, both Frolking and Lammers note, will be linking the results of the physical models to the economic modeling. “We understand each individual piece within our disciplines but tying that altogether will be very challenging,” says Frolking.

Lammers notes that the project will use the “loosely coupled models” in sequential fashion. For example, the modelers from the University of Alaska-Fairbanks will run their glacier melt model for the Himalaya driven by the Intergovernmental Panel on Climate Change forecasts, or some regional predictions if available. The outcome of that model run would be adapted to the hydrological model and then, using the same IPCC climate drivers, “we’d move that data downstream to get the results,” says Lammers. This same process would, in turn, be done using the DNDC and, finally, economic models.

Adds Lammers, “I believe this project will make us aware of the capabilities and limitations of the other disciplines, and that can only be a good thing. It will allow us to learn and become stronger scientists.”

by David Sims, Science Writer, Institute for the Study of Earth, Oceans, and Space. Published in Fall 2010 issue of EOS Spheres.