Hydrologic Extremes: Patterns, Causes, and Impacts

Drought conditions for 1014, 1931 and 1955 based on the Palmer Drought Severity Index as reconstructed from tree rings and
instrumental data. Yellow-to-red colors are drier than average and blue colors are wetter than average. The spatial patterns of these
droughts illustrate changes in atmospheric circulation patterns. Source: Cook, E.R. and P.J. Krusic. 2004. The North American Drought
Atlas. Lamont-Doherty Earth Observatory and the National Science Foundation.
http://iridl.ldeo.columbia.edu/SOURCES/.LDEO/.TRL/.NADA2004/.pdsi-atlas.html

Water sustains human societies and ecosystems, but it can also pose significant hazards through droughts, flooding, and landslides. Water and hydrologic processes have strong and complex interactions with the carbon cycle, sediment and nutrient transport, and the structure and function of terrestrial, estuarine, and marine ecosystems. Research in the R&D program is conducted to develop a sound scientific basis for quantifying future hydrologic variability and its potential impacts on the Nation’s infrastructure and ecosystems. The science is based on monitoring, analyses of instrumental records of precipitation, streamflow and water quality, and reconstructions of pre-instrumental hydrology using paleoclimate data. Combining these techniques allows researchers to understand the potential rates of hydrologic change, natural patterns of variability and the impacts of hydrologic change on ecosystems and societies. Integrating the data with modeling efforts provides powerful tools to quantify the response and vulnerability of natural and modified environments to hydrologic change.

A diverse range of water-related research under R&D includes small watershed studies and reconstructions of hydrologic conditions ranging from the Holocene (approximately the last 12,000 years) up to the past few centuries, satellite-based studies of land-cover response to hydrologic extremes, and the impacts of climate change on glacier mass balance and water availability.