Hydrologic Science Priorities for the U.S. Global Change Research Program An Initial Assessment (1999) / Chapter Skim
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2. Science Foundations
2. Science Foundations
Pages 6-15
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From page 6... ...
Toward this end' a better understanding is needed of what causes both short-term and long-term variability in these fluxes that couple the land surface reservoirs of water with each other as well as with the oceans and atmosphere. It is a priority scientific objective to establish how much of the variability in the water cycle is predictable over a range of time and space scales.
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From page 7... ...
For example, feedback between the atmosphere and snow cover, land moisture, vegetation cover, and regional water bodies other Ran the Pacific also induces systematic oscillations and excursions in regional climate. Science Foundations and Basic Processes
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From page 8... ...
may be influenced by large-scale climate variability and local land-atmosphere exchanges in ways that are quite distinct from how those influences affect regional hydroclimate under near-normal conditions. Current hydrologic forecasts (e.g., water supply outlooks or flow forecasts)
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From page 9... ...
For example, the spatial resolution at which atmospheric systems are modeled is from 100 to 10,000 times the scale of heterogeneities in land surface topography, vegetation, soil texture, or snow cover. Similarly, variables like temperature or soil moisture can change significantly in a matter of hours, whereas vegetation changes occur seasonally.
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From page 10... ...
For example, a prediction of snowmelt, runoff, and groundwater recharge over days to weeks may possibly benefit Mom a much finer description of soil and vegetation properties than would land surface feedback into a climate model for seasonal-to-interannual forecasts. For lantatmosphere modeling where the atmospheric boundary layer is the link in the exchanges, there is a natural spatial integration associated with turbulent mixing.
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From page 11... ...
Delineation of pathways is complicated by clifficulties involved in characterizing the land surface (e.g., mapping vegetation and m~crotopography3 and the inability to see into the subsurface. Pathway patterns can be postulated ~nrougn one use of numencar models anal BACK ~magu~y particles, wick represent water molecules and/or chemicals.
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From page 12... ...
? Interachons Between Hydrologic Systems and Ecosystems in aquatic ecosystems, residence times, nutrient fluxes, and many other factors are determined by the rate at which water moves through the hydrologic cycle, yet little is known about how most terrestrial Science Foundations and Basic Processes 12
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From page 13... ...
· Long-term resource management of aquatic ecosystems must be based on a better fundamental understanding of how biogeochemical processes respond to the combined effects of climate vanability, e.g., changes in We nux of organic matter, acid deposition, mineral weathering and of changes in Me hydrologic cycle related to climate warming. Lakes and streams are largely buffered against changes in acidity by m~neral weathering, the rate of which depends on Me supply of acids Mom both precipitation and a basin's terrestnal ecosystem.
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From page 14... ...
Understanding the nature of the dependence of venous aquatic ecosystems on groundwater discharge is needed. Understanding is also needed concerning how to manage water in urban areas to maintain adequate groundwater flows to critical aquatic systems.
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From page 15... ...
Science Foundations and Basic Processes 15
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