Water mission to gauge Alaskan rivers on front lines of climate change

The upcoming Floor Water and Ocean Topography mission will present a trove of information on Earth’s water sources, even in distant places. Alaska serves as a case examine.

Whereas Alaska straddles the Arctic Circle and is roofed by huge expanses of frozen land, the state additionally has quite a lot of liquid water. The truth is, Alaska holds about 40% of U.S. surface water sources. This contains greater than 12,000 rivers, 1000’s extra streams and creeks, and a whole lot of 1000’s of lakes.

So when the Floor Water and Ocean Topography (SWOT) satellite launches this month from California’s Vandenberg House Drive Base, it is solely pure that Alaska will probably be among the many first beneficiaries of this mission led by NASA and the French space company Middle Nationwide d’Études Spatiales (CNES), with contributions from the Canadian House Company and the UK House Company.

SWOT will measure the peak of practically all water on Earth’s floor, from giant rivers to lakes and reservoirs to the ocean. It’ll fill in gaps in distant locations like Alaska and in lots of international locations the place floor water information is sparse or nonexistent. These measurements will probably be useful to water administration and catastrophe preparedness companies, universities, civil engineers, and others who want to trace water of their native areas.

Alaska’s sheer measurement, rugged terrain, and restricted transportation infrastructure make conventional stream gauging price prohibitive. Whereas streamflows in many of the United States are repeatedly monitored by a U.S. Geological Survey (USGS) community of greater than 8,500 stations, there are at the moment solely 113 gauges in Alaska, and plenty of large rivers aren’t monitored. The quantity of water flowing by way of such rivers impacts all the pieces from the well being and biodiversity of fish species to transportation and consuming water availability.

This dearth of Alaskan river info made USGS a logical option to function a SWOT early adopter. SWOT information will complement a system at the moment in growth to observe these rivers, utilizing radar altimetry information from the U.S.-European Jason-2 and -3 and European House Company Sentinel satellites (developed within the context of the European Copernicus program led by the European Fee), and visual imagery from the NASA-USGS Landsat satellites. The undertaking, in its third yr, entails utilizing space-borne devices to measure the elevation and movement of rivers. USGS companions embody the Alaska Division of Transportation and Public Services, Nationwide Climate Service’s Alaska-Pacific River Forecast Middle, U.S. Fish and Wildlife Service, and Alaska Division of Fish and Sport.

“Alaska is a spot that would significantly profit from distant statement for streamflow estimates,” stated USGS hydrologist Robert Dudley. Dudley stated Alaska is a superb take a look at case for scientists and water managers to work with new space-based instruments like SWOT and put them to fast use.

USGS is compiling a historic report of estimated stream discharges, constructing on greater than 20 years of NASA analysis to measure water floor ranges in lakes and rivers. The info will enable scientists and water managers to grasp how typically streams expertise low- and high-flow situations and to develop a reference level to judge present situations.

The SWOT benefit

Dudley says SWOT has quite a few benefits over present satellite-based river measurement strategies. Altimeters like these on the Jason collection of satellites can measure how water ranges range in some giant rivers, and Landsat can measure how river widths range. However neither information supply by itself gives all the knowledge wanted to calculate an affordable estimate of how a lot water is flowing by way of a river with out doing troublesome and dear on-the-ground calibration. SWOT modifications that by measuring each water ranges and width concurrently.

For instance, if a river has steep banks, it will not essentially seem wider or narrower as its discharge price modifications. Conversely, even a tiny change in water elevation in a shallow-banked river can imply much more water is flowing by way of it.

SWOT may even measure a river’s slope, which gives scientists a method to estimate how briskly water is working off the panorama. Usually talking, the steeper the slope, the quicker the water.

And SWOT will accumulate the information wanted to estimate stream flows , each time it flies over a river, which in Alaska will probably be about as soon as each 5 days. SWOT’s radar can also see by way of clouds, eliminating information gaps brought on by clouds in Landsat and different visible-light imagery.

Local weather change is inflicting quite a few hydrological modifications in Alaska that SWOT will assist examine, stated Jack Eggleston, chief of the USGS Hydrologic Distant Sensing Department. “Quickly growing temperatures are inflicting streamflows to extend on the North Slope, the place permafrost is melting,” he stated. “That is additionally altering the seasonality of streamflow, with excessive flows brought on by snow soften occurring earlier within the yr.”

“SWOT goes to permit us to see what is going on on in Alaska hydrologically in ways in which we have not earlier than,” stated Tamlin Pavelsky, NASA’s SWOT freshwater science lead, based mostly on the College of North Carolina, Chapel Hill. “That is vital, as a result of Alaska, being within the Arctic, can be the place in america experiencing essentially the most climate change proper now. If you wish to know why that issues, take into consideration what number of sources we get from Alaska.”