Assessing water resources adaptive capacity to climate change impacts in the Pacific Northwest Region of North America

Abstract

Climate change impacts in Pacific Northwest Region of North America (PNW) are projected to include increasing temperatures and changes in the seasonality of precipitation (increasing precipitation in winter, decreasing precipitation in summer). Changes in precipitation are also spatially varying, with the northwestern parts of the region generally experiencing greater increases in cool season precipitation than the southeastern parts. These changes in climate are projected to cause loss of snowpack and associated streamflow timing shifts which will increase cool season (October–March) flows and decrease warm season (April–September) flows and water availability. Hydrologic extremes such as the 100 year flood and extreme low flows are also expected to change, although these impacts are not spatially homogeneous and vary with mid-winter temperatures and other factors. These changes have important implications for natural ecosystems affected by water, and for human systems. <br><br> The PNW is endowed with extensive water resources infrastructure and well-established and well-funded management agencies responsible for ensuring that water resources objectives (such as water supply, water quality, flood control, hydropower production, environmental services, etc.) are met. Likewise, access to observed hydrological, meteorological, and climatic data and forecasts is in general exceptionally good in the United States and Canada, and access to these products and services is often supported by federally funded programs that ensure that these resources are available to water resources practitioners, policy makers, and the general public. <br><br> Access to these extensive resources support the argument that at a technical level the PNW has high capacity to deal with the potential impacts of natural climate variability on water resources. To the extent that climate change will manifest itself as moderate changes in variability or extremes, we argue that existing water resources infrastructure and institutional arrangements provide a solid foundation for coping with climate change impacts, and that the mandates of existing water resources policy and water resources management institutions are at least consistent with the fundamental objectives of climate change adaptation. A deeper inquiry into the underlying nature of PNW water resources systems, however, reveals significant and persistent obstacles to climate change adaptation, which will need to be overcome if effective use of the region's extensive water resources management capacity can be brought to bear on this problem. Primary obstacles include assumptions of stationarity as the fundamental basis of water resources system design, entrenched use of historic records as the sole basis for planning, problems related to the relatively short time scale of planning, lack of familiarity with climate science and models, downscaling procedures, and hydrologic models, limited access to climate change scenarios and hydrologic products for specific water s...

Rethinking the longitudinal stream temperature paradigm: region-wide comparison of thermal infrared imagery reveals unexpected complexity of river temperatures

“…Our results have implications for biological conservation and management of riverine thermal regimes (Hamlet, 2010;Kaushal et al, 2010;IPCC et al, 2014), aquatic biota and ecosystem processes (Ficke et al, 2007;Mantua et al, 2010), which respond to climate change and other anthropogenic impacts. First, our findings illustrate the variety of spatial patterns of summertime thermal habitat present within and among rivers.…”

Seasonal hydrologic responses to climate change in the Pacific Northwest

“…A number of authors have previously studied the impact of climate variations on streamflow in the PNW [e.g., Hamlet and Lettenmaier , ; Payne et al ., ; Luce and Holden , ; Lee et al ., ; Elsner et al ., ; Hamlet et al ., ; Luce et al ., ; Safeeq et al ., ]. The motivations for these studies stem from the region's vast hydropower resources [ Lee et al ., ], dangers of flooding [ Payne et al ., ], endangered species issues related to anadromous fish [ Mantua et al ., ], agricultural water uses [ Vano et al ., ], and the need to manage reservoir systems to balance these needs [ Hamlet , ].…”

“…Elsner et al . [] classified PNW watersheds into rain‐dominated, transitional, and snow‐dominated based on the ratio of peak snow water equivalent (SWE) to accumulated winter (October to March) P. This classification scheme has been useful to water managers in the region and therefore has been included in subsequent user‐funded studies [e.g., Hamlet , ; Hamlet et al ., ; Tohver et al ., ]. In this work, we also create a classification scheme to identify drivers of hydrologic change, but we base our analysis on modeled hydrologic sensitivities to P and T changes rather than results derived from GCM output.…”

Development and testing of a snow interceptometer to quantify canopy water storage and interception processes in the rain/snow transition zone of the North Cascades, Washington, USA

“…In the Western United States, communities rely on the snowpack as a vital water resource, since up to 70% of annual streamflow is provided by snowmelt alone [ Mote et al ., ]. As climate change projections indicate a loss of snowpack and a shift in snowmelt timing to earlier in the season [ Hamlet , ], we must look for ways to optimize the available snowpack depth and duration. Findings from studies on the impact of forest structure on snowpack suggest that silvicultural manipulation in second‐growth forests may help to balance a negative trend in snowpack snow water equivalent (SWE) by reducing the magnitude of snow intercepted by the trees [e.g., Jost et al ., ].…”