Research

Hydrology and Water Resources

Current Research

Current research at the Climate Impacts Group (CIG) on Pacific Northwest (PNW) climate and hydrology/water resources includes:

Hydrologic Aspects of Climate

• 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.
• Reconciling Projections of Future Colorado River Streamflow. Within the Upper Colorado River Basin, reductions in naturalized streamflow (water management effects removed) by the mid 21st century have been projected to range from 6 to 45% in published studies, and a recent analysis of future P-E (a proxy for runoff) suggests an "imminent transition to a more arid climate in southwestern North America".
• Implications of 21st Century Climate Change for the Hydrology of Washington State. The hydrology of the Pacific Northwest (PNW) is particularly sensitive to changes in climate because seasonal runoff is dominated by snowmelt from cool season mountain snowpack, and temperature changes impact the balance of precipitation falling as rain and snow. Based on results from 39 global simulations performed for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4), PNW temperatures are projected to increase an average of approximately 0.3°C per decade over the 21st century, while changes in annual mean precipitation are projected to be modest, with a projected increase of 1% by the 2020s and 2% by the 2040s.

Regional Hydrologic Forecasting

• UW Westwide Hydrologic Forecast System and Surface Water Monitor. Over the last decade, great strides have been made in land surface modeling at regional to continental scales. The North American Land Data Assimilation System (NLDAS) has developed new approaches for estimating current land surface moisture conditions (e.g., soil moisture, snow and runoff) as well as retrospective reconstructions of the same variables. The University of Washington Westwide Hydrologic Forecast System and Surface Water Monitor (SWM) meld these advances into a system that serves both hydrologic forecast and drought management objectives.

Applications to Water Resource Management

• Droughts and Water Shortages: Economic Impacts and Reducing Vulnerability. Drought presents a significant economic risk to Washington State. Indicators are important to monitor and forecast drought conditions, characterize and compare drought severity, and provide a basis for triggering drought responses. Responses are important to reduce drought impacts, and include mitigations and adaptations taken before, during, and after a drought.
• West-Wide Drought Forecasting System: A Scientific Foundation for NIDIS. Forecasts and real-time assessments of drought offer the potential to mitigate drought impacts. However, current drought monitoring systems for the western U.S. lack a predictive component for specific hydrologic indicators. Further, given that hydrologic impacts account for most drought losses, USGS data are essential to making drought forecasts useful. We are developing a drought forecast and nowcast system for the western U.S., which will serve as a scientific framework for prediction and assessment of agricultural (soil moisture) and hydrologic (streamflow) drought in the region.
• Using NOAA Climate Forecasts with Hydrologic Assessment to Reduce Drought Vulnerability and Improve Water Management in Washington State. The purpose of this research is to develop and implement climate and hydrologic forecasts for water management in the States of Washington and California, to assess the net economic benefits of this forecast information, and to serve as a model implementation of the National Integrated Drought Information System (NIDIS).
• Climate Impacts on Infrastructure Systems in Washington State. Although few statistically significant changes in extreme precipitation have been observed to date in the state's three major metropolitan areas, regional climate model simulations generally predict increases in extreme precipitation over the next half-century, particularly around the Puget Sound. In that region, existing drainage infrastructure designed using mid-20th century rainfall records may, therefore, be subject to rainfall regimes that differ from current design standards.
• Effects of Climate Change on Energy Supply and Demand in the Pacific Northwest and Washington State. Approximately 70 percent of electrical energy consumption in the Pacific Northwest (PNW) is generated by hydropower (Bonneville Power Administration 1994). Because streamflow, mostly within the Columbia River basin, is the main power source, its climatic sensitivity has been a concern, and has been the topic of several previous studies. Regional hydropower production in the Columbia River basin has a profound impact on Washington's energy supply.
• Paleoreconstructions of Pacific Northwest Streamflow. Paleoclimatic streamflow reconstructions derived from proxy records (such as tree-rings) play an important role in water resources planning and management. Longer records based on paleoclimatic reconstructions can provide a better understanding of the probability of distributions of such extreme events by dramatically increasing the temporal sample size.
• Development of Optimized Flood Control Rule Curves for the Columbia River Basin in Response to Climate Change and Interannual Climate Variability. Flood control operations, which are an important element of many multi-objective water resources systems, must ultimately create a balance between flood risk and other system objectives such as water supply or hydropower production. Water resources operating policies that attempt to preserve this balance are usually predicated on assumptions of stationary climate conditions derived from historic streamflow records. Recent climate research has demonstrated, however, that regional climate varies on interannual and decadal time scales, and that systematic changes in temperature are occurring in response to global warming and other factors.
• Climate Change Impacts On Water Management in the Puget Sound Region, Washington, USA. Climate change is projected to result, on average, in earlier snowmelt and reduced summer flows, patterns that are not well represented in the historical observations used for planning and reliability analyses by water utilities. We extend ongoing efforts in the Puget Sound basin cities of Everett, Seattle, and Tacoma to characterize differences between historic and future streamflow and the ability of the region's water supply systems to meet future demands.
• Climate Change Impacts On Water Management and Irrigated Agriculture in the Yakima River Basin, Washington, USA. The Yakima River Reservoir system supplies irrigation water to over 180,000 irrigated hectares (450,000 acres). Runoff is derived mostly from winter precipitation in the Cascade Mountains, much of which is stored as snowpack and runs off in the spring and early summer. Climate change during the 21st century is expected to result in earlier snowmelt runoff, and reduced summer flows.

Related Work

Hydrology and water resources research at the CIG benefits from externally funded, climate-related research projects and programs that key CIG research personnel conduct or are otherwise affiliated with, including the following:

• As part of the Accelerated Climate Prediction Initiative (ACPI) funded water management investigations for the western US, CIG-affiliated researchers and graduate students have been involved with:
  • A study of adaptive management strategies for the Columbia River basin in response to climate change using the ColSim reservoir operation model (Payne et al. 2004). These investigations were some of the first attempts to look explicitly at the transient variability of the climate model simulations for the PNW, and to attempt to mitigate the impacts of these changes in streamflow variability using conventional water resources engineering techniques. Contact: Alan Hamlet.
  • A study on the implications of climate change on California’s Sacramento-San Joaquin River basin hydrology and water resources (Van Rheenen et al. 2002). The impacts of climate variability and change on water resources in California’s Central Valley were studied using a suite of models that predict future precipitation and temperature, watershed hydrology, and reservoir system performance. Results from the water resources system model indicate that achieving and maintaining status quo system performance in the future would be nearly impossible under projected climate change. Demand modification and system infrastructure improvements will be required to account for the volumetric and temporal shifts in flows predicted to occur in the Sacramento-San Joaquin River basins. Contact: Dennis Lettenmaier.
• Nick Bond (UW/JISAO) and Gabe Vecchi (NOAA/PMEL) are examining the relationships between the tropical Madden-Julian Oscillation and precipitation and flooding in the PNW.