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 knowledge on Earth’s water assets, even in distant areas. 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 lots of liquid water. In reality, Alaska holds about 40% of U.S. surface water assets. This contains greater than 12,000 rivers, hundreds extra streams and creeks, and a whole bunch of hundreds of lakes.

So when the Floor Water and Ocean Topography (SWOT) satellite launches this month from California’s Vandenberg Area Drive Base, it is solely pure that Alaska can 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 Area Company and the UK Area Company.

SWOT will measure the peak of practically all water on Earth’s floor, from massive rivers to lakes and reservoirs to the ocean. It’s going to fill in gaps in distant locations like Alaska and in lots of nations the place floor water knowledge is sparse or nonexistent. These measurements can be priceless to water administration and catastrophe preparedness businesses, 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 value 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 lots of massive rivers aren’t monitored. The quantity of water flowing by such rivers impacts all the things from the well being and biodiversity of fish species to transportation and ingesting water availability.

This dearth of Alaskan river info made USGS a logical option to function a SWOT early adopter. SWOT knowledge will complement a system at the moment in growth to watch these rivers, utilizing radar altimetry knowledge from the U.S.-European Jason-2 and -3 and European Area 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 venture, in its third yr, entails utilizing space-borne devices to measure the elevation and movement of rivers. USGS companions embrace 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 Recreation.

“Alaska is a spot that would significantly profit from distant remark for streamflow estimates,” stated USGS hydrologist Robert Dudley. Dudley stated Alaska is a good 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 twenty years of NASA analysis to measure water floor ranges in lakes and rivers. The information will permit scientists and water managers to know how typically streams expertise low- and high-flow situations and to develop a reference level to guage 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 differ in some massive rivers, and Landsat can measure how river widths differ. However neither knowledge supply by itself gives all the knowledge wanted to calculate an inexpensive estimate of how a lot water is flowing by a river with out doing tough and expensive on-the-ground calibration. SWOT adjustments 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 adjustments. Conversely, even a tiny change in water elevation in a shallow-banked river can imply much more water is flowing by it.

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

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

Local weather change is inflicting quite a few hydrological adjustments in Alaska that SWOT will assist examine, stated Jack Eggleston, chief of the USGS Hydrologic Distant Sensing Department. “Quickly rising 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 attributable to 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’ve not earlier than,” stated Tamlin Pavelsky, NASA’s SWOT freshwater science lead, primarily based on the College of North Carolina, Chapel Hill. “That is necessary, as a result of Alaska, being within the Arctic, can be the place in the USA experiencing probably the most climate change proper now. If you wish to know why that issues, take into consideration what number of assets we get from Alaska.”