Satellite Hydrology Group

Principal Investigators: Doug Alsdorf and Michael Durand


The Satellite Hydrology Group uses measurements made with spaceborne instruments to study rivers, lakes, wetlands, and floodplains. Led by Dr. Doug Alsdorf and Dr. Michael Durand, this group uses passive and active microwave measurements, such as radar, to measure surface water and snowpack. The group is working to better quantify the amount of water stored in snowpacks in the United States using satellite measurements.

The group's work includes defining an upcoming satellite, Surface Water and Ocean Topography (SWOT). Rivers are fundamentally two-dimensional in their structure and function. This is evident in the Amazon River, where the floodplain width is measured in kilometers. Because of their sensitive to climatic changes, arctic lakes pose another hydrologic measurement challenge. SWOT measurements will enable new understanding of these complex systems. SWOT will track freshwater resources, and measure ocean currents. The project is a joint effort between NASA, the Jet Propulsion Laboratory, and the French space agency, CNES.

The Satellite Hydrology Group's research helps answer the questions:

  • How much water is on the Amazon floodplain? This amount plays an important role in the global carbon budget by allowing carbon to bubble-out of the water and directly into the atmosphere. Using satellites, we have estimated the volume at 285 cubic km.
  • How much water is on the Congo interfluvial wetlands? Like the Amazon, this volume should also play a role in the global carbon budget - but for now that role remains unquantified. Nevertheless, satellites allow us to estimate the Congo wetland volume at 111 cubic km.
  • In both cases, i.e., the Amazon mainstem and the Congo rivers, we find that the amount of water fluxing through their wetlands is a fraction of the volume discharged at the mouths of the rivers. Surprisingly, the amounts are small: the amount of water on the Amazon mainstem floodplain is only about 5% of the river discharge and, in the Congo, the amount is about 8% of its river discharge. 
  • How does the water fill and decant these systems? Despite the broad-brush, cursory similarities of the Amazon and Congo, where both are large tropical wetlands, the manner in which water flows into and out of them differs. The Amazon appears to be dominated by fluvial processes such that the mainstem river supplies water to the floodplain and allows it to flow back to the river. In the Congo, our preliminary observations based on satellite measurements suggest that the rivers do not deliver water to the wetlands.