Chapter 6. Center for the Study of Earth from Space (CSES), 1985-2002
Reciprocal Coupling between Runoff and Channel Networks
Gupta
works with river flows that shape landforms and create channel networks.
The space-time dynamics of river flows depends on the geometry and hydraulic-
geometry of networks. This reciprocal coupling between channel
networks and river flows is depicted in empirical power-law relationships
that have been observed within the last 50 years. However, in the last
decade his group has pioneered new ideas to understand these empirical
power laws on the basis of newly developing mathematical ideas of scale invariance
(self-similarity) and scale dependence. This body of work has been
carried out concurrently in three complementary phases.
Phase (a) involved spatial analyses of large channel networks using
digital terrain models through a Ph.D. dissertation by S. Peckham (1995).
It showed major discrepancies between data and predictions by the wellknown
random model developed in 1967, and led to the development of
a new class of random self-similar network models through a Ph.D. dissertation
by Seth Veitzer (1999). Veitzer received an American Geophysical
Union student award in nonlinear geophysics (2000) for this work.
Research on phase (b), involving new developments in statistical scaling
theories of space-time precipitation, was conducted jointly with Ed
Waymire (mathematics department, Oregon State University) and
through a Ph.D. dissertation by Thomas Over (1995). Phase (c) involving
signatures of self-similarity in empirical analyses of floods was carried
out in collaboration with David Dawdy (private consultant and researcher,
San Francisco). Since 1996, the researchers have focused on developing
a physical basis for these empirical statistical scaling
relationships using conservation laws. Sandra Castro (1998) took the
first step on this problem in a master's thesis. This work is continued
through collaborations with Waymire and M. Sivapalan (University of
Western Australia). Peter Furey took another step on space-time analyses
of low flows pioneering new ideas through a Ph.D. dissertation completed
in 2001. A long-term goal of this entire body of research is to make
hydrologic predictions from basins that have inadequate stream flow
data in space and time. Referred to as poorly gauged and ungauged, most
basins worldwide fall into this category.
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