Terrestrial Water Cycle Seminar: Dr. Doug Alsdorf (Ohio State Univ.)

Hosted by the SWOT group


The Surface Water and Ocean Topography satellite mission (SWOT, http://swot.jpl.nasa.gov/) is both a tremendous opportunity for hydrology and a tremendous investment by NASA.  What do we expect to learn from SWOT’s measurements and does this warrant NASA’s funding? While the “Decadal Survey” has already affirmatively answered these questions, important foundational points and related opportunities remain, including the following. (1) Our current methods of measuring floodwater dynamics are either sparsely distributed or temporally inadequate.  As an example, flood depths are measured by using high water marks, which capture only the peak of the flood wave, not its temporal variability.  (2) Discharge is well measured at individual points along stream networks using in-situ gauges, but these do not capture within-reach hydraulic variability such as the water surface slope changes on the rising and falling limbs of flood waves. (3) Just a 1.0 mm/day error in ET over the Congo Basin translates to a 35,000 m3/s discharge error.  Knowing the discharge of the Congo River and its many tributaries should significantly improve our understanding of the water balance throughout the basin.  The Congo is exemplary of many other basins around the globe.  (4) Arctic hydrology is punctuated by millions of unmeasured lakes.  Globally, there might be as many as 30 million lakes larger than a hectare.  Storage changes in these lakes are nearly unknown, but in the Arctic such changes are likely an indication of global warming.  (5) Well over 100 rivers cross international boundaries, yet the sharing of water data is poor.  Overcoming this helps to better manage the entire river basin while also providing a better assessment of potential water related disasters. It is perhaps immoderate to suggest that these points, above, are revolutionary in nature, but these do represent significant and transformational approaches to surface water hydrology.