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Assessing water resources adaptive capacity to climate change impacts in the Pacific Northwest Region of North America
Abstract and Figures
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.
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.
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 systems, and rigid water allocation and water resources operating rules that effectively block adaptive response. Institutional barriers include systematic loss of technical capacity in many water resources agencies following the dam building era, jurisdictional fragmentation affecting response to drought, disconnections between water policy and practice, and entrenched bureaucratic resistance to change in many water management agencies. These factors, combined with a federal agenda to block climate change policy in the US during the Bush administration has (with some exceptions) led to institutional "gridlock" in the PNW over the last decade or so despite a growing awareness of climate change as a significant threat to water management. In the last several years, however, significant progress has been made in surmounting these obstacles, and the region's water resources agencies at all levels of governance are making progress in addressing the fundamental challenges inherent in adapting to climate change.
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... Adaptation plans for responding to climate change in the Pacific Northwest are being developed (e.g., review in National Wildlife Federation 2011). However, several papers emphasize that institutional barriers are a serious impediment to proactive climate change adaptation in water management (Farley et al. 2011b;Hamlet 2011;Safford and Norman 2011). ...
... Farley et al (2011b) describe capacity for institutional responses to climate change among four water sectors in Oregon's McKenzie River basin and found that some sectors have more flexibility (e.g., fish habitat recovery and flood control) than others (e.g., municipal water and fishing guides) for responding to climate change. Hamlet (2011) also examines institutional capacity for water management adaptation, and finds that, although existing institutions have resources to deal with moderate changes, substantial obstacles to climate change adapation exist for large and complex systems such as the Columbia River basin. Lack of a centralized authority for water management decisions, layers of existing laws and regulations, and lack of specificity in some management plans contribute to this concern. ...
... Climate modeling, regional variation, and armed conflict Climate modeling forecasts dramatic regional variation in temperature and precipitation anomalies as a result of changing pressures on weather systems (Hamlet 2011;Hansen et al. 2012;IPCC 2014;US DoD 2011). Within geographically expansive countries, the variation is expected to be large (Hamlet 2011). ...
... Climate modeling, regional variation, and armed conflict Climate modeling forecasts dramatic regional variation in temperature and precipitation anomalies as a result of changing pressures on weather systems (Hamlet 2011;Hansen et al. 2012;IPCC 2014;US DoD 2011). Within geographically expansive countries, the variation is expected to be large (Hamlet 2011). For example, on the African continent, a 2.5°square grid generates 42 separate grids incorporating the Democratic Republic of Congo, with each grid comprising a land area of approximately 270 by 270 km; there are 495 grids on the African continent. ...
The dynamic relationships between climate change and armed conflict have been discussed at length, but there have been few studies that integrate dimensions of climate adaptation into the processes linking climate change to armed conflict. By using geospatial grids for climate change and armed conflict, and country-level climate vulnerability measures of sensitivity and adaptive capacity, we empirically examine the effects of climatic and non-climatic conditions on the probability of armed conflict in Africa. Results suggest that there are close links between climate drivers and armed conflict. Importantly, greater levels of adaptive capacity lead to a lower likelihood of armed conflict. From a policy perspective, our results suggest that enhancing adaptive capacity under conditions of climate pressure will reduce the probability of people taking up arms in response to water scarcity.
... Yet nearly a generation after its passage, the WSRA remains relatively unstudied in terms of how managers interpret and implement its provisions as part of larger resource management, especially in comparison to other preservation-era legislation such as the Wilderness Act (Chesterton & Watson, 2017;Perry, 2017a;Bowker & Bergstrom, 2017). Much has changed in the management of public lands since 1968, including reductions in budgets for agencies managing public lands, shifts in societal values or public infrastructure needs, expansion or new roles for public involvement in collaborative management of protected areas, and a focus on landscape-level management priorities, including the impact of climate change (Clarke & McCool, 1996;Feldman et al., 2005;Daniels & Walker, 2001;Lurie & Hibbard, 2008;Hamlet, 2011;Archie et al., 2012;Weber & Stevenson, 2017). Understanding how the influences above continue to affect resource management surrounding Wild and Scenic Rivers (WSRs), and how agency professionals are responding to such challenges, are important mechanisms for adapting management to new realities while meeting the policy requirements of the WSRA. ...
The Wild and Scenic Rivers Act (WSRA) provides a high level of protection for free flowing rivers in the United States. Yet more than 50 years after its passage, there is little research exploring management of resources under the Act, including across agencies or private partners managing protected rivers. The research presented here used a mixed-method approach consisting of quantitative rankings and interviews to explore river manager and partner perspectives about the most pressing management actions and barriers for continued river management under the WSRA in concert with the 50th anniversary of the Act. We also explore the role of public-private partnerships in continued management of protected rivers. Our approach consisted of a national sample and replicates a similar effort conducted in concert with the 30th anniversary of the WSRA, providing a unique longitudinal perspective. Results indicate that a continued lack of public understanding or support for Wild and Scenic Rivers (WSRs), a need for dedicated agency funds to manage rivers once designated, and additional guidance about flexibly interpreting WSRA provisions as highly prioritized barriers or future actions. Qualitative results illuminate the importance of public partnerships in garnering political support for additional WSR management resources, key needs for manager exchanges or mentorship programs given the retirement of experienced WSR professionals, and the importance of organized, but varied private partnerships in planning or management of rivers across different regions of the United States. We conclude by discussing next steps for systematically gauging appreciation for WSRs among segments of the public, expanding understandings of the unique benefits associated with WSR designation, and further development of agency-public partnership templates surrounding designated river management.
... Opinions vary about whether large water management systems will be able to accommodate such changes. Some argue that the use of historical records as the basis for planning, combined with rigid reservoir operating rules, limits adaptation to changing conditions (Hamlet, 2011). Uncertainty surrounding the drivers of change complicates efforts to predict and manage under traditional approaches that assume stationarity (Cosens & Williams, 2012;Milly et al., 2008). ...
Around the world, long‐term changes in the timing and magnitude of streamflow are testing the ability of large managed water resource systems constructed in the 20th century to continue to meet objectives in the 21st century. Streamflow records for unregulated rivers upstream of reservoirs can be combined with records downstream of reservoirs using a paired‐watershed framework and concepts of water resource system performance to assess how reservoir management has responded to long‐term change. Using publicly available data, this study quantified how the intra‐annual timing of inflows and outflows of 25 major reservoirs has shifted, how management has responded, and how this has influenced reliability and vulnerability of the water resource system in the 668,000 km² Columbia River basin from 1950 to 2012. Reservoir inflows increased slightly in early spring and declined in late spring to early fall, but reservoir outflows increased in late summer from 1950 to 2012. Average inflows to reservoirs in the low flow period exceeded outflows in the1950s, but inflows are now less than outflows. Reservoirs have increased hedging, that is, they have stored more water during the spring, in order to meet the widening gap between inflows and outflows during the summer low flow period. For a given level of reliability (the fraction of time flow targets were met), vulnerability (the maximum departure from the flow target) was greater during periods with lower than average inflows. Thus, the water management system in this large river basin has adjusted to multi‐decade trends of declining inflows, but vulnerability, that is, the potential for excess releases in spring and shortfalls in summer, has increased. This study demonstrates the value of combining publicly available historical data on streamflow with concepts from paired‐watershed analyses and metrics of water resource performance to detect, evaluate, and manage water resource systems in large river basins.
... Similarly, simulations of reservoir operations for three future periods in Colorado River Basin projected a decrease in the probability of meeting demand from 92% in a historical climate simulation to 59-75% for future simulations (Christensen et al. 2004). In some locations, modified reservoir release policies have been developed to mitigate the impact of hydrologic shifts caused by climate change (Hamlet 2011 in Pacific Northwest Region of North America; Stagge et al. 2017 in Washington, DC). However, another study found that using reservoir balance models developed for a reservoir in Italy, climate change scenarios did not significantly affect the reservoir resilience (Mereu et al. 2016). ...
Climate change has the potential to alter the quantity and timing of runoff, which may pose significant challenges for reservoir management. One challenge is developing operating policies for an unknown and uncertain future. Here, we develop a suite of ‘optimal’ operating policies for the reservoir system of Portland, Oregon. We assess the sensitivity of projected reservoir reliability to the choice of GCMs and time periods used to develop each of our policies. Results indicate that, while different GCMs and fitting periods produce different optimal operating policies, when those policies are applied across all the other GCM scenarios, the overall projected reliability does not change due to the great variability between simulations. Across the simulations, we note a trend of decreasing reliability in the future which is not sensitive to the choice of GCM or fitting period. This indicates that the projected reliability is dominated by uncertainty in climate projections that cannot be mitigated by tuning operating policies to projected changes.
... Barsugli ve ark. [5] ve Hamlet [6] tarafından belirtildiğine göre; son yıllarda, yerel ve bölgesel ölçekte yüzey iklimindeki tarihsel trendler oldukça dikkate değer bir konu olarak kabul edilmektedir ve iklim üzerinde oluşabilecek olumsuz değişimleri azaltmak için birçok strateji geliştirilmiştir. Tarihsel iklim üzerindeki küresel veya geleneksel ölçekteki gözlemler veya gelecekteki iklim projeksiyonları, yerel ve bölgesel ölçek planlamaları için daha az kullanışlıdır [5]. ...
Precipitation, temperature and streamflow parameters are the most important hydro-meteorological variables that reveal climate change/climate variability in the planning and management of water resources. Parametric and non-parametric trend tests are used to analyze long-term gradual changes or trends on hydro-meteorological variables. The Mann-Kendall test and Sen's slope estimation method are used as widely as from past to present and have shown very good performance in determining the trend for hydro-meteorological variables. The trend analysis for hydro-meteorological parameters will provide many benefits to water managers in better management and planning of water resources. In this study; informations on the most commonly used trend tests on hydro-meteorological variables was compiled, examples of trend analysis for different regions of the world were put forward, and a general evaluation was made on the importance of trend analysis in the direction of these examples. Özet Yağış, sıcaklık ve akış parametreleri, su kaynaklarının planlanmasında ve yönetiminde iklim değişimi/iklim değişkenliğini ortaya koyan en önemli hidro-meteorolojik değişkenlerdir. Hidro-meteorolojik değişkenler üzerinde uzun zamanlı kademeli değişimleri veya eğilimleri analiz etmek için parametrik ve parametrik olmayan trend testleri kullanılmaktadır. Hidro-meteorolojik değişkenler için trendin belirlenmesinde Mann-Kendall testi ve Sen'in eğim tahmini yöntemi geçmişten günümüze kadar çok yaygın olarak kullanılmakta ve çok iyi bir performans ortaya koymaktadır. Hidro-meteorolojik parametrelere ilişkin yapılacak olan trend analizi, su kaynaklarının daha iyi yönetimi ve planlanmasında su yöneticilerine birçok fayda sağlayacaktır. Bu çalışmada; hidro-meteorolojik değişkenler üzerinde en yaygın olarak kullanılan trend testlerine ilişkin bilgiler derlenmiş, dünyanın farklı bölgeleri için trend analizi örnekleri ortaya konulmuş ve bu örnekler doğrultusunda trend analizinin önemi konusunda genel bir değerlendirme yapılmıştır. Anahtar Kelimeler: İklim değişimi, yağış, sıcaklık, akış, trend analizi, Mann-Kendall testi 1. Giriş İklim değişimi, yıllar veya daha uzun periyodlar için var olan iklim ortalamalarındaki büyük değişimler olarak ifade edilmektedir. İklim değişimi küresel ölçekte oluşmasına rağmen, iklim değişiminin etkisi bölgeden bölgeye farklılık göstermektedir [1]. Bundan dolayı, iklim değişiminin izlenmesinde meteorolojik değişkenlerdeki değişimlerin analizi oldukça önemli bir konudur [2]. Özellikle bir bölge için mevcut ve geçmişteki hidro-meteorolojik değişkenlerin değişimleri ve trendlerin bilgisi, nüfus artışı ve ekonomik büyümeden dolayı suya olan gereksinimin artması ve küresel ısınma, su
... Many coupled human-environment systems in Idaho centered on issues of water resources are being impacted by population growth, land-use change, and climate change. Idaho has been among the fastest growing states in the past decade (Sheridan, 2007;Smutny, 2002;Travis, 2007), relies heavily on snowmelt runoff for agricultural productivity and energy production (Hamlet and Lettenmaier, 1999;Hamlet, 2011), and has seen substantial declines in spring snowpack over the past century (e.g., Mote et al., 2005Mote et al., , 2018. Continued changes in these drivers of state-level water resources in the coming half-century are reasoned to impact Idaho's waterscapes (Tohver et al., 2014). ...
Water availability and use are increasingly critical factors determining the resilience and vulnerability of communities in the Western United States (US). Historical water availability and use in the state of Idaho is synthesized by considering the biophysical drivers of climate and surface runoff alongside human drivers of land-use, hydrologic engineering and state water management and policies. Idaho has not experienced chronic water scarcity in the last half century, particularly in comparison to neighboring states to the south. An outlook of water availability and use in Idaho for the next half century is developed that accounts for projected changes in population and climate. The magnitude of annual runoff is not expected to change substantially across much of Idaho, yet the timing of surface water availability is likely to change due to earlier snowmelt and reduced summer surface water availability. We posit that Idaho is well positioned to make institutional and policy decisions that secure its own water resources in the face of changing environmental conditions and resource-based water demands.
Water resources in the Pacific Northwest (PNW) are characterized by significant interannual to interdecadal variation. Paleo‐proxy reconstructions such as those derived from tree‐rings provide longer‐term context and supplement information on this expected range of variability, which can improve planning, management, and response related to extreme events and hydrologic change. However, existing paleo‐proxy reconstructions have yet to address the potential for pronounced within‐ and among‐basin variations in the PNW due to a lack of spatial coverage. Here we develop methodologically consistent reconstructions for 36 gages in the PNW, including the Columbia and Snake River drainages, as well as key coastal watersheds. These reconstructions extend back at least to the 1500s coefficient of efficiency. Reconstruction skill is relatively high (mean R² = 0.63), and snowpack‐ or winter precipitation‐sensitive chronologies from high‐elevation sites provide important contributions to reconstruction skill. At the whole‐region scale, reconstructed variability indicates evidence for drier and wetter years, more persistent decadal variability, and correspondingly longer episodes of deficit and surplus compared to instrumental records. Within the region, this expanded range of extremes appears especially prevalent in the Snake River and southern PNW watersheds. Regionally, cumulative deficits in the early 1500s and mid 1600s rival those of the early 20th century, though persistence and timing vary widely among basins. These reconstructions suggest that considering within‐region variability will be key for water management and planning under climate change, and that sub‐regional adaptation strategies are likely to be advantageous.
The Florida Water and Climate Alliance (FloridaWCA) is a stakeholder–scientist partnership committed to increasing the relevance of climate science data and tools at time and space scales needed to support decision-making in water resource management, planning, and supply operations in Florida. Since 2010, a group of university researchers, public utility water resource managers and operators, water management district personnel, and local planners have engaged in a sustained collaboration for the development, sharing, and application of cutting-edge research to the practical issues of water management and distribution in the highly urbanized state of Florida. The authors, all members of FloridaWCA, present a case study of the organization’s history, its achievements, and lessons learned at the organizational, scientific/technical, and personal levels. Their goals are to 1) describe how the organizational process has contributed to actionable science based on posing and answering questions of importance; 2) share its scientific impact and technical contributions; 3) demonstrate the value of such a stakeholder–scientist partnership, and 4) identify organizational and structural components that have influenced its effectiveness, including personal reflections. The FloridaWCA, having reached its tenth anniversary, continues to evolve today as a sustained stakeholder–scientist partnership resulting in both guiding researchers of what is applicable in the field (creating an area of research that is useful to society) while also helping the practitioners to push the envelope on the state-of-the practices that can be informed by current research.
Plain Language Summary
The Surface Water and Ocean Topography (SWOT) satellite will, for the first time, simultaneously measure elevations and extents of the Earth's surface waters at high resolution. The satellite will measure almost everywhere on Earth as many as seven times every 21 days, with more observations at higher latitudes. In this study, we explored how nonuniform measurements in time, varying by location, impact the ability of SWOT to capture river discharge frequency behavior. Based on the comparison between discharge frequency distributions derived from daily USGS gauge measurements and synthetic SWOT observations, SWOT's unique temporal sampling does not impact observed discharge behavior. When considering both temporal sampling and uncertainty, 78% of the study locations still match the truth discharge frequency distributions. In general, SWOT temporal sampling has minimal impact on derived discharge quantiles, but the combination of both temporal sampling and uncertainty leads to underestimated discharge quantiles. The magnitude of the underestimated discharges for larger quantiles (i.e., ≥75%) is less than the negative bias used for SWOT discharge uncertainty, implying a mitigation of negative bias in discharge at larger discharge quantiles.
This paper describes the application of deterministic optimization to the main stem Missouri River reservoir system and the development and testing of inferred optimal operating rules from these model results. An implicit stochastic optimization approach is taken and tested using a simplified simulation model. This work illustrates the applicability and limitations of applying deterministic optimization to development of strategic operating rules for large-scale water resource systems. For this multipurpose multireservoir system, simple data display and simulation modeling are found to be superior to classical regression techniques for inferring and refining promising operating rules from deterministic optimization results.
Scenarios of global climate change were examined to see what impacts they might have on transboundary water management in the Columbia River basin. Scenario changes in natural streamflow were estimated using a basin hydrology model. These scenarios tended to show earlier seasonal peaks, with possible reductions in total annual flow and lower minimum flows. Impacts and adaptation responses to the natural streamflow scenarios were determined through two exercises: (a) estimations of system reliability using a reservoir model with performance measures and (b) interviews with water managers and other stakeholders in the Canadian portion of the basin. Results from the two exercises were similar, suggesting a tendency towards reduced reliability to meet objectives for power production, fisheries, and agriculture. Reliability to meet flood control objectives would be relatively unchanged in some scenarios but reduced in others. This exercise suggests that despite the high level of development and management in the Columbia, vulnerabilities would still exist, and impacts could still occur in scenarios of natural streamflow changes caused by global climate change. Many of these would be indirect, reflecting the complex relationship between the region and its climate.
In western North America, snow provides crucial storage of winter
precipitation, effectively transferring water from the relatively wet
winter season to the typically dry summers. Manual and telemetered
measurements of spring snow-pack, corroborated by a physically based
hydrologic model, are examined here for climate-driven fluctuations and
trends during the period of 1916-2002. Much of the mountain West has
experienced declines in spring snowpack, especially since midcentury,
despite increases in winter precipitation in many places. Analysis and
modeling show that climatic trends are the dominant factor, not changes
in land use, forest canopy, or other factors. The largest decreases have
occurred where winter temperatures are mild, especially in the Cascade
Mountains and northern California. In most mountain ranges, relative
declines grow from minimal at ridgetop to substantial at snow line.
Taken together, these results emphasize that the West's snow resources
are already declining as earth's climate warms. Joint Institute for the
Study of the Atmosphere and the Ocean Contribution Number 1073.
As part of the National Assessment of Climate Change, the implications of future climate predictions derived from four global climate models (GCMs) were used to evaluate possible future changes to Pacific Northwest climate, the surface water response of the Columbia River basin, and the ability of the Columbia River reservoir system to meet regional water resources objectives. Two representative GCM simulations from the Hadley Centre (HC) and Max Planck Institute (MPI) were selected from a group of GCM simulations made available via the National Assessment for climate change. From these simulations, quasi-stationary, decadal mean temperature and precipitation changes were used to perturb historical records of precipitation and temperature data to create inferred conditions for 2025, 2045, and 2095. These perturbed records, which represent future climate in the experiments, were used to drive a macro-scale hydrology model of the Columbia River at 1/8 degree resolution. The altered streamflows simulated for each scenario were, in turn, used to drive a reservoir model, from which the ability of the system to meet water resources objectives was determined relative to a simulated hydrologic base case (current climate). Although the two GCM simulations showed somewhat different seasonal patterns for temperature change, in general the simulations show reasonably consistent basin average increases in temperature of about 1.8-2.1°C for 2025, and about 2.32.9°C for 2045. The HC simulations predict an annual average temperature increase of about 4.5°C for 2095. Changes in basin averaged winter precipitation range from -1 percent to +20 percent for the HC and MPI scenarios, and summer precipitation is also variously affected. These changes in climate result in significant increases in winter runoff volumes due to increased winter precipitation and warmer winter temperatures, with resulting reductions in snowpack. Average March 1 basin average snow water equivalents are 75 to 85 percent of the base case for 2025, and 55 to 65 percent of the base case by 2045. By 2045 the reduced snowpack and earlier snow melt, coupled with higher evapotranspiration in early summer, would lead to earlier spring peak flows and reduced runoff volumes from April-September ranging from about 75 percent to 90 percent of the base case. Annual runoff volumes range from 85 percent to 110 percent of the base case in the simulations for 2045. These changes in streamflow create increased competition for water during the spring, summer, and early fall between nonfirm energy production, irrigation, instream flow, and recreation. Flood control effectiveness is moderately reduced for most of the scenarios examined, and desirable navigation conditions on the Snake are generally enhanced or unchanged. Current levels of winter-dominated firm energy production are only significantly impacted for the MPI 2045 simulations.
Using precipitation and temperature data for the 20th century in
combination with a macroscale hydrologic model, we evaluate changes in
flood risk in the western U.S. associated both with century-scale
warming and interannual climate variations. In addition, we examine the
implications of apparent increases in precipitation variability over the
region since the mid-1970s. We use detrended temperature data
representing early and late 20th century climate to force the variable
infiltration capacity hydrologic model and show that spatially
homogeneous temperature changes over the western U.S. in the 20th
century on the order of +1°C per century have resulted in
substantial changes in flood risks over much of the region. Although
changes specific to particular geographic areas are apparent in some
cases, the overall changes due to observed warming trends are well
categorized by midwinter temperature regimes in each watershed. Cold
river basins where snow processes dominate the annual hydrologic cycle
(<-6°C average in midwinter) typically show reductions in flood
risk due to overall reductions in spring snowpack. Relatively warm
rain-dominant basins (>5°C average in midwinter) show little
systematic change. Intermediate or transient basins show a wide range of
effects depending on competing factors such as the relative role of
antecedent snow and contributing basin area during storms that cause
flooding. Warmer transient basins along the coast in Washington, Oregon,
and California, in particular, tend to show increased flood risk. While
the absolute value of simulated changes in flood risk is affected by
basin scale, the nature of the relationship of flood risk to basin
temperatures in midwinter is largely scale-independent. Climate
variations associated with Pacific Decadal Oscillation (PDO) and El
Niño Southern Oscillation (ENSO) also have strong effects on
flood risks. In contrast to the effects associated with 20th century
warming, the climate variability signal is characterized by regional
scale patterns related to the geographic distribution of cool season
precipitation also identified in many previous studies. In general, the
largest changes in simulated flood risks are associated with years when
PDO and ENSO are "in phase," particularly in the southwest. Changes in
the variability of cool season precipitation after about 1973, the
causes of which are uncertain, are shown to result in increased flood
risk over much of the western U.S. in the simulations.
Pacific Northwest temperatures have warmed by 0.8 °C since 1920 and are predicted to further increase in the 21st century. Simulated streamflow timing shifts associated with climate change have been found in past research to degrade water resources system performance in the Columbia River Basin when using existing system operating policies. To adapt to these hydrologic changes, optimized flood control operating rule curves were developed in a previous study using a hybrid optimization-simulation approach which rebalanced flood control and reservoir refill at a monthly time step. For the climate change scenario, use of the optimized flood control curves restored reservoir refill capability without increasing flood risk. Here we extend the earlier studies using a detailed daily time step simulation model applied over a somewhat smaller portion of the domain (encompassing Libby, Duncan, and Corra Linn dams, and Kootenai Lake) to evaluate and refine the optimized flood control curves derived from monthly time step analysis. Moving from a monthly to daily analysis, we found that the timing of flood control evacuation needed adjustment to avoid unintended outcomes affecting Kootenai Lake. We refined the flood rule curves derived from monthly analysis by creating a more gradual evacuation schedule, but kept the timing and magnitude of maximum evacuation the same as in the monthly analysis. After these refinements, the performance at monthly time scales reported in our previous study proved robust at daily time scales. Due to a decrease in July storage deficits, additional benefits such as more revenue from hydropower generation and more July and August outflow for fish augmentation were observed when the optimized flood control curves were used for the climate change scenario.
Water has always been the key element of human development, quality of life, and transportation in the Pacific Northwest(PNW).Whileseeminglyabundantwhenirrigationwasfirstdevelopedinthe19thCentury,todaymanyPNW rivers are fully allocated, leading to conflict in times of drought, a situation which may be exacerbated by the effects of climatechange.InthePNW,waterismanagedbyanarrayofFederal,State,andnon-governmentalentities,eachwithits own perspective and mission. This paper discusses the relative merits of solutions based on supporting market mechanisms through improved definitions of water rights on the one hand, and authoritative mandates on the other.