The WATER-HM Satellite Mission Concept

1
1. The Problem
3. Measurements Required Two dimensional
mappings of h, which yield dh/dt and dh/dx
Coverage from a pulse limited altimeter severely
under samples rivers and especially lakes. For
example, a 16-day repeat cycle (i.e., Terra)
coverage misses 30 of rivers and 70 of lakes
in the data bases (CIA-2 UNH UH) whereas a 120
km swath instrument misses very few lakes or
rivers (1 for 16-day repeat and 7 for 10-day
repeat)
100 Inundated!
In-situ methods provide a one-dimensional,
point-based view of water surfaces in situations
where a well defined channel boundary confines
the flow. In practice, though, water flow and
storage changes in many riverine environments are
not simple, and involve the spatially complex
movement of water over wetlands and floodplains
and include both diffusive flows and narrow
confined (channel) hydraulics. Wetlands and
floodplains are governed by the dynamics of water
movement, and as described next, are vital to
ecology and to climate and weather.
Although in situ gauge measurements are the
backbone of much of our understanding of surface
water dynamics globally, these gauge networks
provide essentially no information about
floodplain flows and the dynamics of wetlands.
In situ networks are generally best in the
industrialized world and are worse in sparsely
settled areas (e.g., high latitudes and tropics).
For instance, the network of stream gauges in
the Potomac River (expressed in number of gages
per unit drainage area) is about two orders of
magnitude greater than in the Amazon River basin.

Measurements required to answer the science and
applications questions require multi-dimensional
sampling protocols distributed globally
essentially a space based solution. Water
surfaces are strongly reflective in the
electromagnetic spectrum, thus nadir viewing
radar altimeters have been highly successful in
measuring the elevation of the worlds oceans.
Expansion of this technology to inland waters,
which have much smaller spatial dimensions than
the oceans, has met with some success despite the
construction of existing radar altimeters for
ocean applications which are designed to average
over relatively large areas, and hence are
problematic for surface water applications where
the lateral extent is comparatively limited.
Water flow across wetlands and floodplains is
complex as demonstrated in the plot of Actual
dh/dt acquired with repeat-pass interferometric
SAR. Because this method has a far off-nadir look
angle, it requires flooded vegetation to return
the radar pulse to the antenna after it is
specularly reflected from the water surface. The
repeat pass also limits the method to dh/dt
measurements, only (not h, not dh/dx).
The WATER-HM Satellite Mission Concept Water And
Terrestrial Elevation Recovery Hydrosphere
Mapper This poster describes the WATER portion of
the joint concept Where is water stored on
Earths land surfaces, and how does this storage
vary in space and time? Doug Alsdorf, U.S. WATER
alsdorf.1_at_osu.edu earthsciences.osu.edu/water L
ee Fu, JPL Hydrosphere Mapper llf_at_pacific.jpl.nas
a.gov sealevel.jpl.nasa.gov Nelly Mognard,
CNES WATER nelly.mognard_at_cnes.fr
www.legos.obs-mip.fr/recherches/missions/water/
4. The Solution KaRIN Ka-band Radar
Interferometer. SRTM, WSOA heritage.
Images of h globally every 8 days.
2. Science Questions Societal Applications
WATER-HM will be an interferometric altimeter
which has a rich heritage based on (1) the many
highly successful ocean observing radar
altimeters, (2) the Shuttle Radar Topography
Mission (SRTM), and (3) a development effort for
a Wide Swath Ocean Altimeter. WATER will provide
surface elevation data in a 120 km wide swath
using two Ka-band synthetic aperture radar (SAR)
antennae at opposite ends of a 10 m boom.
Interferometric SAR processing of the returned
pulses will yield a 5m azimuth and 10m to 70m
range resolution, with elevation accuracy of 50
cm. Polynomial based averaging increases the
height accuracy to about 3 cm. The orbital
repeat cycle is designed to permit a global
sampling of all surface water bodies about three
times a month, or near weekly.

• Ka-band SAR interferometric system with 2 swaths,
  each 50 km in width
• Produces water and land heights and co-registered
  all weather amplitude imagery
• 200 MHz bandwidth (0.75 cm range resolution)
• Use near-nadir returns for SAR altimeter angle of
  arrival mode (e.g. Cryosat SIRAL mode) to fill
  swath
• No data compression onboard data down-linked to
  ground stations

Global models of weather and climate could be
constrained spatially and temporally by stream
discharge and surface storage measurements. Yet
this constraint is rarely applied, despite
modeling results showing that precipitation
predicted by weather forecast models is often
inconsistent with observed discharge. For
example, Roads et al. (2003) found that the
predictions of runoff by numerical weather
prediction and climate models were often in error
by 50, and even 100 mismatches with
observations were not uncommon. Coe (2000) found
similar results for climate model predictions of
the discharge of many of the worlds large
rivers. The inter-seasonal and inter-annual
variations in surface water storage volumes as
well as their impact on balancing regional
differences between precipitation, evaporation,
infiltration and runoff are not well known.
Lacking spatial measurements of wetland locations
and sizes, hydrologic models often do not
properly represent the effects of surface storage
on river discharge. Errors can exceed 100
because wetlands moderate runoff through
temporary storage and change the surface area
available for direct interception of
precipitation and free evaporation. While earth
system models continue to improve through
incorporation of better soils, topography, and
land-use land-cover information, their
representations of the surface water balance are
still greatly in error, in part due to the
absence of an adequate observational basis for
quantifying river discharge and surface water
storage.
As the heritage for WATER HM, SRTM is already
providing measurements of water surfaces around
the world. The top panel shows h measurements on
the Amazon River and the derived dh/dx curve.
Discharge estimated from these data is within 8
of the gauged discharge. The bottom panel shows h
measurements above and below the Hoover Dam in
Columbus Ohio the height difference matches the
dam.
Recent efforts have demonstrated that direct
water surface-to-atmosphere carbon evasion are an
important component of the carbon cycle.
Calculation of organic carbon fluxes requires
knowledge of the spatial distributions of aquatic
ecosystem habitats, such as herbaceous
macrophytes and flooded forests, and estimates of
carbon evasion require measurements of the
spatial and temporal variations in the extents of
inundation.
177 Participants from 28 Countries on 5
Continents (and growing!) Rodrigo Abarca del Rio,
Jose Achache, Graeme Aggett, Mohammad Khaled
Akhtar, Doug Alsdorf, Kwabena Asante, Sima
Bagheri, Georges Balmino, Richard Bamler, Luis
Bastidas, Subhashranjan Basu, Okke Batelaan, Paul
Bates, Matt Becker, Ed Beighley, Philippa Berry,
Keith Beven, Mike Bevis, Charon Birkett, Mark
Bishop, Leonid Bobylev, Mikhail Bolgov, Bodo
Bookhagen, Jeff Booth, Elizabeth Boyer, Robert
Brakenridge, Rafael Bras, Alexander Braun, Andrew
Brooks, Richard Bru, Stephen Burges, Stephane
Calmant, Anny Cazenave, Richard Ciotola, Michael
Coe, Jean-Francois Cretaux, Bruno Cugny, Bob
Curry, Marc De Batist, Biao Deng, Stephen Dery,
Reinhard Dietrich, Remco Dost, Claude Duguay,
Victor Dukhovnyi, Bernard Dupre, Michael
Eineder, Theodore Endreny, Jay Famiglietti,
Balazs Fekete, Naziano Filizola, Andrew Folkard,
Bruce Forsberg, Rick Forster, Georgia Fotopoulos,
Peter Gege, Santiago Giralt, Scott Goetz, Kalifa
Goita, Richard Gross, Jean-Loup Guyot, Andreas
Guentner, Stephen Hamilton, Jim Hamski, Peter
Hildebrand, Simon Hook, Matt Horritt, Martin
Horwath, Faisal Hossain, Paul Houser, Jinming Hu,
Cheinway Hwang, Motomu Ibaraki, Walter Illman,
Hiroshi Ishidaira, Shafiqul Islam, Stephane
Jacquemoud, Mike Jasinski, Eric Jeansou, Ola
Johannessen, Joel Johnson, Natalie Johnson, Hahn
Chul Jung, Essayas Kaba, Jobaid Kabir, Josef
Kellndorfer, Brian Kiel, Yunjin Kim, Wolfgang
Kinzelbach, Jean Klerkx, Toshio Koike, Alexei
Kosarev, Andrey Kostianoy, Pascal Kosuth, Chuck
Kroll, Sunil Kumar De, Xi-Jun Lai, Venkat
Lakshmi, Bruno Lazard, Sergey Lebedev, Brigitte
Leblon, John Lenters, Dennis Lettenmaier, Xu
Liang, Peter Luk, Yaoming Ma, Ian Maddock, Jun
Magome, Dushen Mamatkanov, Ramiz Mammedov, Marco
Mancini, Andrew Marcus, Bryan Mark, Thomas
Maurer, Kyle McDonald, Daene McKinney, John
Melack, Yves Menard, Carolyn Merry, Philip
Micklin, George Miliaresis, Bill Mitsch, Nelly
Mognard, Delwyn Moller, Alberto Montanari,
Richard Moore, Andreas Neumann, Stefan Niemayer,
Eni Njoku, Daniel O'Connell, Jonathan Partsch,
Tamlin Pavelsky, Christa Peters-Lidard, Lasse
Pettersson, Al Pietroniro, Bill Plant, Will
Pozzi, Shavkat Rakhimov, Naama Raz Yaseef,
Philippe Renard, Jacques Richard, Ernesto
Rodriguez, Ake Rosenquist, Carlos Saavedra, Stein
Sandven, Frank Schwartz, Frederique Seyler,
Yongwei Sheng, C.K. Shum, Trey Simmons, Murugesu
Sivapalan, Leonard Sklar, Larry Smith, James
Smith, Detlef Stammer, Bob Su, Kuniyoshi
Takeuchi, Ryan Teuling, Julian Thompson, Eric
Thouvenot, Wim Timmermans, Laurent Tocqueville,
Kevin Toomey, Peter Troch, Muhammad Noaman Ul
Haq, Susan Ustin, Nick van de Giesen, Zoltan
Vekerdy, Charles Vorosmarty, Wolfgang Wagner,
Claudia Walter, Matt Wilson, Eric Wood, Ouan-Zan
Zanife, Jianyun Zhang, Tiam Zhang, YunxuanZhou
Funding provided by CNES, JPL and the Terrestrial
Hydrology Program at NASA
Designed by Natalie Johnson and Jonathan Partsch,
the Ohio State University