Draft Hydrology science questions for WATER HM Dennis P. Lettenmaier Department of Civil and Environmental Engineering University of Washington Water HM Inaugural Science Working Group Meeting Washington, D.C. October 29, 2007

Why are the science questions important? They provide the overall motivation for the mission NASA’s niche in the earth sciences is to bring technology to bear on issues related to scientific discovery Science questions provide the rationale for linkages to other programs (ICSU, UN, etc.) Nonetheless, societal relevance, and potential for transition to operations, play an important role

From meeting agenda: Science questions: What is the spatial and temporal variability in the world's terrestrial surface water storage and how can we predict these variations more accurately? How much water is stored on a floodplain and subsequently exchanged with its main channel? How much carbon is potentially released from inundated areas? Applications questions : Can health issues related to waterborne diseases be predicted through better mappings? What are the policy implications that freely available water storage data would have for water management?

From ESAS RFI: What is the spatial and temporal variability in the world’s terrestrial surface water storage? What is the global distribution of freshwater runoff delivered to the oceans and what is its inter-seasonal and inter-annual variability? How much water is stored on a floodplain and subsequently exchanged with its main channel? What are the local and continental-scale responses of braided rivers to climate induced changes in glacier mass-balances? What are the temporal and spatial relationships in biogeochemical fluxes from fluvial and wetland environments and how do they contribute to global budgets of carbon and nutrients? What are the water surface elevations across a flood wave in urbanized and natural environments and what are the corresponding extents of inundation? What are the policy implications that freely available water storage data would have for water management? Can health issues related to waterborne diseases be predicted through better mappings?

From ESAS (Chapter 4) “The wide swath altimeter will measure spatial fields of surface elevations for both inland waters and the ocean. These will lead to new information about the dynamics of water stored at the land surface (in lakes, reservoirs, wetlands, and river channels), … For rivers, … the resulting discharge estimates will constitute fundamentally new measurements for many parts of the globe where there is no in situ stream gauge network, or where the network is too sparse to estimate surface water dynamics at large scales. “

From ESAS (Chapter 11) “The change in water stored in lakes, reservoirs, wetlands, and stream channels, and the discharge of streams and rivers, are major terms in the water balance of global land areas. Yet both terms are poorly observed globally; observations of these variables are now provided almost exclusively by in situ networks, the quality and spatial distribution of which varies greatly from country to country. More importantly, even where the density of in situ gages is relatively high, the point data are unable to capture the spatial dynamics of wetlands and flooding rivers …”

From ESAS Chapter 4 mission summaries

Straw man: 2 science questions, 2 applications questions Science questions: How much liquid water is stored on Earth’s land surfaces, and what are its dynamics? How and to what extent do the hydrodynamics of inundated areas control the propagation of flood waves in major rivers, and what are their implications for regional and global carbon and other constituent fluxes?

Applications questions: How much water is stored in the world’s artificial reservoirs, what are its space-time dynamics, and what effect will freely available information about global reservoir storage have on water management, particularly in trans-boundary rivers? How do the dynamics of seasonally and ephemerally inundated areas affect the propagation of disease vectors, such as malaria, and can knowledge of, and the capability to predict, such dynamics reduce the incidence of waterborne disease?

Estuaries – at the intersection of hydrological and ocean sciences Should there be both science and applications questions related to estuaries?