University of Washington water expert Dennis Lettenmaier will speak on Jan. 25 on the evolution of hydrological models for long-range stream flow forecasting and their potential for assessing climate change on western U. S. water resources.
Free and open to the public, the 4 p.m. talk, "Implications of Hydrologic Variability and Change for Western Water Management," will be held in the auditorium of the Cooperative Institute for Research in Environmental Sciences. The CIRES auditorium is room 338 in the CIRES building on the University of Colorado at Boulder campus.
"We now have the capability to simulate the hydrology of large river basins," Lettenmaier said. Traditionally, hydrologists have used "bottom-up" modeling approaches, in which a river basin's drainages are represented one by one, a painstaking and time-consuming process.
"It is well known that considerable stream-flow forecasts for the upcoming season can be derived from knowledge of the initial hydrologic conditions," he said. "For many years hydrologists produced accurate stream-flow forecasts for the spring and summer by knowing how much snow was on the ground in early April."
Today, ensemble weather and climate forecasts -- all the parts being viewed as one -- are available, providing information about precipitation and temperature during the forecast period.
"As a result, hydrologists have the skill to forecast even when initial conditions have only a modest influence on future stream flow," he said.
Forecasters can gauge how much snow may be anticipated before it falls and make stream-flow forecasts as long as a year in advance.
But "ensemble" weather and climate forecasts provide information about precipitation and temperatures during the forecast period, he said.
Ensemble forecasts also are being used for climate impact assessment, he said. In this case, coupled land-ocean-atmosphere models are designed over simulation periods as long as a century or more.
Lettenmaier will address how the use of large-scale hydrology models can assess the implications of water variability up to a decade in advance using models relative to greenhouse warming trends. He will focus on the implications of climate variability and changing water management in the West.
Lettenmaier, a professor in the civil and environmental engineering department at the University of Washington since 1976, served as program manager for NASA's Land Surface Hydrology Program at NASA Headquarters in Washington, D.C., in 1997 and 1998.
In 1990, he received the American Society for Civil Engineers first Huber Research Prize. In fall 2000 he won the American Geophysical Union Hydrology Section Award for his innovative integration of atmospheric and hydrologic sciences.
The chief editor for the American Meteorological Society's Journal of Hydrometeorology, Lettenmaier has published more than 100 peer-reviewed articles.
Lettenmaier's talk is part of the Distinguished Lecture Series program sponsored by CIRES, a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration. Lecture series administrators invite speakers with interdisciplinary communication skills to address the general public.
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