Hydrology and Water Resources: Current Research

Hydrologic Effects of 20th Century Warming and Climate Variability in the Western U.S.



Although in the past climate has frequently been assumed to be stationary in time, it is now widely recognized as an important variable affecting hydrologic processes at a number of different time scales. This improved understanding of the role of climate has resulted in major research initiatives to improve the understanding of climate dynamics and the impacts of climate variability and climate change on various scientific, engineering, and management problems. Understanding past hydroclimatic variability is a central component of this research. Historic observations are the basis for relating climatic variability to hydrologic processes, and provide the foundation for constructing and evaluating hydrologic models based on these physical relationships. Using models, it is possible to more fully analyze the impacts of climate in the observed record, and also to project the impacts of climate forwards in time with lead times ranging from a few months up to a century or more.

Given suitable hydrologic simulation models and meteorological driving data sets, another important use of the observed climate record is to produce simulated hydrologic data as surrogates for long-term observations. Such an approach can improve the temporal and spatial resolution of observed hydroclimatic data, provide surrogates for unmeasured variables, and provide a means for more fully evaluating observed changes in climate and hydrologic variability at the regional and river basin scale. The use of models, for example, can facilitate clearly-defined diagnoses and sensitivity analyses that are not possible using observations alone. Models also facilitate the examination of relatively large areas in a consistent manner, avoiding problems with inconsistencies between observing systems, missing data, or other issues frequently encountered in the analysis of observed data. Furthermore, given that neither model simulations nor observations are perfect realizations of the past, corroborating data from both sources greatly strengthens conclusions derived from analysis of the historic record.

The project has produced a series of publications exploring the effects of 20th century warming and climate variability on a number of important hydrologic and water resources variables using both observed and simulated data.


Scripps Institute of Oceanography (California Applications Program)

Primary Funding


Related Publications

For publications on climate impacts on PNW water resources, please see CIG Publications.

Adam, J.C., A. F. Hamlet and D. P. Lettenmaier. 2009. Implications of global climate change for snowmelt hydrology in the 21st century. Hydrological Processes 3(7), 962-972.