Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ering ff Open Access , 2,3 Discussions Sciences ects Research Earth System Earth ff Hydrology and and Hydrology , C. P. Weaver 1,* 1 ects Research Laboratory, ff 2876 2875 , P. J. Wigington Jr. , and J. L. Ebersole 1 4,** , R. L. Comeleo , E. A. Sproles 1 2 ects projected for the MFJD. A major strength of the HL approach is that results ff ects provided by groundwater in the high aquifer permeability portions of the upper ect survival, growth and reproduction of salmonids in these watersheds, with great- ff ff now at: Centro de Estudios Avanzados en Zonas Áridas, La Serena, Chile This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. US EPA, National Center for EnvironmentalThe Assessment, US Washington, Global D.C., Change USA ResearchORISE Program, post-doc, Washington, c/o D.C., USA US EPA, National Health and Environmental E US EPA, National Health and Environmental E retired can be applied to similarly classified, ungaged basins. Information resulting from such summer baseflow, but impactse could potentially be mitigatedSandy. The by Middle streamflow Fork John bu Daydominated. basin (MFJD), The in basin northeastern Oregon,with experiences is an a snowmelt- increase net inspring loss to dry of winter climate seasonality, wet representing area.area. and a 20–60 Altered The moist % seasonality MFJD reduction climate and/or in alsoa area, magnitude snowmelt-dominated experiences of along major seasonal streamflows shiftsest could from e potentially a small switch fromthere very is a wet modest to increase in wetSandy fall and climate, basin, winter on with water the due no western to slopebut increased change of precipitation. there in the For the Cascades, are seasonality. HL However, major climatemeability, class changes which does in not experiences change, seasonality, especially a for 100 % areas with loss low of aquifer spring per- seasonality. This would reduce aquifer permeability, terrain,1971–2000 and HL soil climate permeability. indicesfrom We the are ECHAM evaluate and recalculated changes PCM usingios. climate when Changes models 2041–2070 with in the simulation the climate A2, results major class A1b, changes and were in B1 modest seasonality emission class (4–18Oregon scenar- %) for shifts five statewide. from of However, being the there 13 % sixfive were snow-dominated realizations realizations, to representing (excluding 4–6 a PCM_B1): % 56–68 snow-dominated %basin under reduction these in scale, snowmelt-dominated projected area. At changes the for the Siletz basin, in Oregon’s coast range, include Classification can allow assessmentstheir responses of to the stressors. hydrologic Here(HL) functions we approach demonstrate of to the assess landscapes useand vulnerability and of basin to a potential scales. hydrologic landscape future The climate HL change classification at statewide has five components: climate, seasonality, Laboratory, Corvallis, Oregon, USA * ** Received: 28 January 2014 – Accepted: 22Correspondence February to: 2014 S. – G. Published: Leibowitz 11 ([email protected]) MarchPublished 2014 by Copernicus Publications on behalf of the European Geosciences Union. Abstract P. E. Morefield Corvallis, Oregon, USA 2 3 4 Hydrologic landscape classification assesses streamflow vulnerability to climate change in Oregon, USA S. G. Leibowitz 1 Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/11/2875/2014/ 11, 2875–2931, 2014 doi:10.5194/hessd-11-2875-2014 © Author(s) 2014. CC Attribution 3.0 License. 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erences in ff orts. ff 2878 2877 ects on seasonal snow accumulation (Sproles et al., 2013) and subse- ff In the PNW, human demand for water, human land uses within watersheds, and The impacts of these changes are expected to vary due to regional di Potential impacts of climate change include transitioning of snow into rain, result- growth and survival of stream salmonids. salmon embryos and juvenilesvenile (Quinn, salmon 2005). due Winter to flows1983), displacement, can particularly injury, cause during or mortality high-magnitude exhaustion ofmates events (Tschaplinski (e.g., ju- that and see could US Hartman, increase EPA,imum 2013). under temperatures Increased future (Arismendi synchrony cli- et offuture al., summer climate 2013) low flows may change and increasingly scenarios.tion max- stress Other for salmonids shrinking low under space flow (Chapman, stressesother 1966), food include reduced sources drift increased (Harvey of et competi- macroinvertebrate al.,sites prey 2006), (Cairns and and et increased al., incidence 2005; of McCullough et disease al., and 2009) para- – all factors that can lead to reduced Battin et al., 2007;of Mantua these et stocks al., under 2010).agement the Threatened Endangered in and Species the endangered Act status regionare often of (McClure cued drive many et water by and al., hydrologicditions basin and 2013). during man- thermal Pacific both salmon regimes, winter and and and trout streamflow summer life and can histories temperature strongly con- regulate survival and growth of associated impacts on waterwith quality costly can repercussions. For conflict example, withrestoration expenditures needs in associated with the of river US aquatic and exceedassociated species, stream USD with 1 often billion recovery annually of (Bernhardt Pacificexceed et salmon USD al., in 300 the 2005), million Snake with annually River costs and (Huppert, basin temperature alone 1999). projected regimes Anticipated to in changesnificant the to concern streamflow next for century long-term for viability PNW of rivers cold-water and salmonids streams (Beechie are et of al., sig- 2006; quent contributions of snowmelt to baseflow.significant Luce declines and in Holden low (2009) flow found statistically regimessheds. from This 1948 can to have 2006 significant indrinking 72 implications % water for of and human PNW study water summeryear, water- needs when habitat water for of demand irrigation is aquatic and at biota its during peak. the driest portions of the have dramatic e ticularly relevant, because considerable portionsthe of freezing the point snowpack (Nolin accumulate and close Daly, to 2006). As a result, increases in air temperature can rates, changes in theand fate shifts and in transport important of aquatic2007; ecosystem nutrients, Karl processes sediments, et and al., and functions 2009; toxic (Kundzewicz Johnson et chemicals, al., et al., 2012;meteorological US forcing, EPA, physiographic 2013). setting, and interactioncesses, with land local use, ecosystem and pro- water management.the In timing the western of US, Fritze streamflowwatersheds. et In shifting al. the (2011) US towards found Pacific earlier Northwest (PNW), in the transition the from year snow to in rain is snowpack-dominated par- ing in diminished snowpack and2004; shifts Stewart in et streamflow toHolden, al., earlier 2009; 2004, Stewart, in 2005; 2009; the Mote season2011; Barnett and (Service, Johnson et Salathé, 2010; et al., Abatzoglou, al.,clude 2011; 2005; 2012; changes Fritze Mote in et Nolin, extreme al., et high 2012; and al., US low 2005; flow EPA, events, 2013). Luce alteration Other of and groundwater possible recharge impacts in- Climate change is likelysources. to Changes have in significant,across the long-term much amount implications of and for theexperiments freshwater intensity suggest re- United of these States precipitation trends willtinued (Groisman have warming continue et been accompanied throughout by al., observed the a 21st(Intergovernmental 2005, general century, intensification Panel 2012). with of on con- the Climate global Climate2013). modeling hydrologic cycle Change, This calls 2007; into Karl questiondation et the for water concept al., management of 2009; for “stationarity” decades Kharin that (e.g., has et Milly provided et al., the al., foun- 2008). and basin scales without requiring detailed modeling e 1 Introduction assessments can help inform management responses to climate change at regional 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects of ers the ff ff ). Prognos- erent regions across Oregon. Implica- ff 2880 2879 http://waterdata.usgs.gov/or/nwis/rt ects the hydrologic cycle across geographies (Sawicz ff ectively supporting the needs of practitioners involved in the man- ff ort and additional analysis is often required to place the climate informa- ff The purpose of this paper is twofold: first, we provide results from an analysis for the In contrast, a classification-based approach to assessing climate impacts on hydro- While informative, both data- and model-based studies have deficiencies. Diagnostic Context-specific tools and methods for vulnerability assessment provide critical sup- It is well understood that, while climate change is a global phenomenon, natural well as vulnerability ofSecond, salmonids, through which the are use anof of important this this water-dependent approach case resource. to study supportapproach we with climate-related provide information decision-making: a about i.e., proof-of-concept integration potentialexploration application of can future the climate also HL change. be Thisand leveraged type to lessons of advance learned focused a from,change broader vulnerability such dialogue assessment. approaches about the to need inform for, management-relevant climate state of Oregon, using the HLclimate classification realizations to show may how impact results water fromfor resources. six three Results potential case future are study presented basins statewidetions representative and of of these di results for the magnitude and timing of water resources are discussed, as fication developed by Wigingtontegrated et measures al. of (2013) the forand key the (b) drivers state an of of approach theclimate for Oregon hydrologic coupling change provides characteristics these (a) to of drivers in- impacts. watersheds, trace with This information multiple, contextualization about management-specific of potential oftenpossibility pathways future hard-to-interpret of of more climate e climate information o change agement of landscapes andstressors. watersheds in the face of both climate change and other ity of information that models can provide. logic systems couldderstanding support of a how broad-scale climateet analysis a al., that 2011; Safeeq provides et a al., systematic 2013). un- In particular, the hydrologic landscape (HL) classi- (Sivapalan et al., 2003). Deficiencies in process understanding also constrain the qual- Safeeq et al., 2013). A secondjected approach climate is change to into use dynamic prognosticchanges hydrologic studies will models that be to integrate expressed pro- better hydrologicallySurfleet understand (Tague et how and these al., Grant, 2012). 2009; Elsner et al., 2010; studies are constrained by datawetter limitations areas and, (for in example, the western see US, map are at biased towards sources. port for needed synthesis andsuch translation at information local is to to regional employies levels. diagnostic One approaches to way that to analyze use provide historical observation-based stud- stream, snow, and climate data over multiple decades (e.g., a result, e tion in thepects context of of the the particularIn management particular, decision there endpoints or is an of managementthat urgent can need concern need help for (Johnson and practitioners translational and frame sciencedecision-relevant other their and Weaver, climate science decisions 2009). critical change applications contextually vulnerability as- bymation assessments. supporting on This robust likely would and changes includethese in infor- changes the on timing local and watersheds, quantity and of possible water consequences resources, on the local e aquatic re- resource management responses tolocal climate (Dozier, 2011). change This (e.g., refersteristics adaptation) both of are a to particular inherently spatial decision/management scale, context.tant as This challenge situation well presents for as an informing to impor- future the management climate unique adaptation risks, charac- with as scientific such information information about is often non-local and somewhat generic. As tic studies can provideclimate a impacts. more spatially-balanced However,with and they poor deterministic are spatial understanding commonly resolution, of or applied focused at on gaged broad basins geographic to scales allow for model validation 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1.0 (driest) to 1.0 (wettest), − and partition all of the drainage area for 2 2882 2881 minimum drainage area threshold. The resulting assess- 2 ner, 1985). There is less overall precipitation east of the Cascades, ff The climate index is based on the Feddema (2005) Moisture Index (FMI), which was Precipitation follows a Mediterranean climate, with the greatest amounts during win- Westerly winds with moisture-laden marine air from the Pacific Ocean are the state’s modified from Thornthwaite (1948). Theand FMI is ranges calculated from as: The assessment unitsstream were network defined with a using 25 km ment drainage units areas have derived ana average from given stream area a or of river synthetic without 44and the km units seasonality being indices nested. were Below, we calculated,specifics review since how on the they the climate are aquifer the permeability,Wigington terrain, basis et and for al. soil the (2013). permeability current work; indices are found in Wigington et al. (2013) developed an HLwatershed classification system using components that of the control climate- and the through watersheds magnitude, and delivery,dices and stream (Figs. networks. S1 movement and These of S2(3) components water in aquifer consist the into permeability, (4) Supplement): of terrain, (1) five andlated annual (5) in- climate, for soil (2) each permeability. climate These of indices seasonality, 5660 were calcu- assessment units across Oregon (Fig. S3 in the Supplement). 13 970 mm (Ru but snowfall can stillAlthough be the considerable in Coast the Rangetively higher has low elevations overall the (annual (Leibowitz average highest of et 25–76 precipitationin al., mm) the in because 2012). Willamette of the its Valley state, is lower elevation. not snowfall Snowfall common. is rela- 2.2 Initial 1971–2000 hydrologic landscape maps fluenced by ocean surface temperaturecillation fluctuations and such the as Pacific the Decadal El Oscillation Niño-Southern (Fleming Os- et al., 2007). ter months. The abundance ofsonal winter precipitation snowpack results in in the the accumulation Cascades, of a with sea- annual average depths ranging from 7620 to and elsewhere in the Pacific Northwest, precipitation and temperature variability is in- Cascades are generally mildtures and, east on of the the coast, Cascades relatively are uniform, more whereas extreme tempera- (Taylor and Hannan, 1999). In Oregon major source of precipitation.itation Oregon’s to mountain their ranges westCascades produce create and orographic a rain precip- strong shadows demarcationthe between to dry the their eastern wet western two-thirds eastthe third (Fig. (Taylor of moderately 1). and the wet Moisture Hannan, state Willamette conditions and the 1999). in Valley (760–1520 wetter western The mm coastal Oregon average areas range annualRange from (1780–2290 precipitation) mm), (2540–5080 to mm). and the In(200–380 very mm) contrast, wet except areas rain at east forests high of of elevations the the in Coast Cascades the mountains. are Temperatures generally west dry of the central Oregon, the Wallowa andBasin Blue in Mountains the in southeast, the theOchoco northeast, Klamath the Mountains and Northern Siskiyou in Mountains Great the tohave state’s the extensive center. southwest, areas and The of the Klamath,nately metamorphic Siskiyou, volcanic bedrock. in and origin Eastern Blue (Loy Oregon Mountains et al., bedrock 2001). is predomi- to over 3000 m. Theern Cascade and Mountains central-eastern run north-south, sectionsprised (Loy dividing of et the highly weathered, state al., low into 2001). permeabilityweathered, bedrock, west- The higher and Western the permeability High bedrock Cascades Cascades (Tague are have andlocated less Grant, com- adjacent 2004). to The Coast theintrusions Range Pacific is of Ocean volcanic and rock. isand The comprised Cascade Willamette of Mountains, Valley, sedimentary located containsdeposits. bedrock between sedimentary Other with the major and Coast physiographic volcanic Range features rocks include overlain the by Columbia flood Plateau in north- 2.1 Study area The State of Oregon, locatedologic in and the climatic Pacific conditions. Northwestern Elevation ranges US from (Fig. sea 1), level has along diverse the ge- Pacific coast 2 Methods 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | < (1) “M” = C) and 0 ◦ ≥ 0, there is , in > T FMI ∗ m > , in mm) was cal- 0 S PACK ∆ 0, the net decrease in < “S” (semiarid); and FMI ∗ m = ) (2) 1 was summed for each of four − “W” (wet); 0.33 . Fall and winter seasons (here- ∗ m 0 m 0 0.66 PACK = S S ∆ ≥ − is a bias-corrected, estimated snow- PACK 0.33 − ∗ m et al., 2000) for a total of six realizations ≥ FMI ∗ m ć . Finally, > m were based on 30 year (1971–2000) monthly FMI 2884 2883 T > enovi > S 0.33 (PACK ć − 0 m − and S ) ). Conversely, if m P m < S PET 0 m − “D” (dry); S m = PET PET P that is restricted to nonnegative values (Leibowitz et al., 2012). ( across both equilibrium and transient climate sensitivity (Inter- ≥ m = 2 0.33 “V” (very wet); 0.66 P P < ∗ m if = ≥ − 1 if P PACK 0.66 − PET FMI ∆ ≥ is monthly surplus (mm) and PACK − > P − and PET are mean annual precipitation and potential evapotranspiration (in PET 1 “A” (arid). m m S P = ( S = = represents the amount of water available from atmospheric sources, taking into ac- For each of the two GCMs, we processed projections under three emissions sce- For the seasonality index, monthly snowmelt modified surplus ( m 0 0 0.66 respond to distinct concentrationsscenario of describes a greenhouse heterogeneous gases future, (GHGs). with The global A2 per emissions capita wealth and fertility demonstrated among the highestto and a lowest global doubling climate ofgovernmental sensitivities, Panel CO on respectively, Climate Change,global 2007). climate However, as sensitivity will rank be order discussed does further, not necessarily holdnarios at regional drawn scales. from theReport Intergovernmental on Panel Emissions on Scenarios (Naki Climateof Change’s future (IPCC) climate. Special Eachble future of development these of emissions technology, society scenarios and is the environment intended that to ultimately describe cor- plausi- than ten GCMs, weburg (ECHAM) limited and the our Parallel Climate analysisa Model large to (PCM) GCMs. range output Our of intent fromcombinations was that projected the were to changes likely bracket European to in produce Centretial both climate choice large HAM- of and by the small ECHAM including relative and changes. model/emission PCM This models ini- scenario was motivated by the fact that these models We projected future HLcalculating distributions the under climate various and climatetemperature seasonality change data indices, realizations produced using by by mean general re- circulationperiod monthly models precipitation was (GCMs) and selected for 2041–2070. to This used represent bias-corrected potential and mid-21st statisticallyet downscaled century (BCSD) al., changes. climate To 2007) simulations do drawnIntercomparison (Maurer this, Project from we phase the 3 (CMIP3; Worldtion Meehl output Climate et for Research al., the 2007). Programme’s period BCSD from Coupled provides 1950–2099. Model simula- While BCSD results are available for more after referred to as winter)Mediterranean were wet combined season. because they encompass Oregon’s normal 2.3 Projected 2041–2070 hydrologic landscape maps the season with the maximum average accumulated FMI seasons: fall (October–December), wintersummer (January–March), (July–September). spring The (April–June), seasonality and each assessment index unit was one of then three defined classes (fall by or assigning winter, spring, to or summer) based on count potential evapotranspiration anda snowpack/snowmelt. net If increase inamount snowpack of (accumulation surplus exceeds watersnowpack snowmelt), ( causes thereby a reducing net the tation release into of snowpack). In water this (output case exceeds any conversion of precipi- − culated for each assessment unit based on Leibowitz etS al. (2012): where pack value for month S average day length. Annual mean normals, using 400 m PRISMthen climate defined data by (Daly assigningtypes: et FMI each al., assessment 2008). unit The(moist); climate to 0 index the was following Feddema moisture where mm), respectively, and FMI is unitless.as PET a was function calculated of according to saturated Hamon water (1961) vapor density (a function of temperature, 5 5 25 15 20 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 T (3) − and P . Deficits i data were : T ∗ S . We also pro- 0 and S P . These were then used to 0 S erences among the six realiza- ff is the area of assessment unit i A 2886 2885 cient technologies. Selection of these three scenarios ffi C across the state. The 2041–2070 44 %. In December (the month with the greatest precip- ◦ −

,0 0 i 6 to S − erences (deltas) from the 1971–2000 initial normals. Changes in for three case study basins (Fig. 1): the Siletz and Sandy, in west- ff i ∗ A S 1 max = n i × et al., 2000). Therefore, for the climate simulations we discuss here, the P i values) were not included because it was hypothesized (Wigington et al., ć 0 A S represents the area-weighted monthly watershed positive surplus from each 1 C. Average monthly precipitation values for 1971–2000 were then multiplied by assessment units in a basin, and ∗ = ◦ n i S enovi n ć P 9 %, respectively. For the 2041–2070 temperature values, the change deltas for by realization for our analysis, and examined trends in monthly = − We calculated We examined maps showing change in climate class, FMI, seasonality class, and A bilinear interpolation method was used to simultaneously project and resample ∗ 0 ern Oregon, and the Middle Fork John Day in eastern Oregon. Characteristics of the S where of the (negative 2013) that local assessmentriver, units but they have do the notstem ability have channel. the to ability contribute to water remove large to amounts a of mainstem water from the main- not serve as thewater sole water from source multiple for assessmentbasin higher-order scale streams units. can and They be rivers, used foundof which to higher-order receive that estimate streams the HLs and integrated rivers. aggregated hydrologic To do conditions at this, and the they behavior introduced river the term S duced confusion, or error,and matrices seasonality (Congalton, class. 1991) to quantify changes2.4 in climate Case study basins Wigington et al. (2013)sheds noted only for that first HL order ephemeral, assessment intermittent, units and function small perennial as streams; complete they do water- (Figs. S10–S15 in thetions Supplement). ranged Temperature from di 0.9used to to calculate 1.5 projected future valuesupdate of the PET, climate FMI, and and seasonality2070 indices (Figs. and S16–S21 produce in projected the Supplement). HL maps for 2041– monthly temperature were added to 1971–2000 average monthly temperature values to for 2041–2070 as di precipitation were calculated as alated percentage in and changes in temperaturethe were calcu- percent change deltastation to values produce (Figs. projected S4–S9 in 2041–2070in the average July Supplement). monthly The precipitation precipi- maximum (the positivestate month percent ranged change with from the 21 largestchange increases ranged to in from 76 % precipitation)itation), over across the the the maximum six positive realizations, and while minimum the negative minimum changes were negative 2 to 39 and 1/8th degree climate data for theus 2041–2070 to period for match all six thedata realizations. used projection This in allowed and the original 400-meterdetermined HL by grid classification. weighting cell Output the cell sizeto values values from the of of the center the the four of interpolation nearest 1971–2000 the were cell output centers cell by the in distance the input grid. We calculated monthly climatologies global solutions and resource-e provides future climate projectionsand that low assume (B1) a increase relativelyimportant high in to (A2), global medium note GHGs (A1b), byA1b that, trajectory the for produces end the slightly of higher mid-century(Naki GHG the concentrations timeframe 21st than we does Century. the However, considerA1b A2 it experiments in storyline is actually this reflect greater paper, GHG the forcing than the A2 experiments. and on a regional basis.nomic In growth contrast, with the global A1bconverges. population scenario In peaking describes this mid-century a scenario as worldfossil energy global global of technologies. rapid per economies The eco- capita B1 are scenarioglobal wealth balanced assumes convergence the between as same fossil in population pattern and A1b, and but non- with a strong trend toward adoption of sustainable rates converging very slowly, and technological advancement occurring more slowly 5 5 25 20 15 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 0.08. < is mean Q 1 suggests < ∗ is greater than ff Q/S ratio, where erences between global ∗ ff Q/S 1 indicates that runo ratio to assess whether the river expe- > ∗ ∗ Q/S 2888 2887 Q/S is less than available surplus. ff ect on HL characteristics. ff 0.04 to 0.00 category (Fig. 3), which represents the smallest amount of drying. Even Each assessment unit experiences some change in FMI under all six realizations. While trends for the discrete climate class are patchy across the state, changes in For all but the two B1 realizations, changes are always to the next driest climate − the assessment units experience larger absolute changes in FMI and, as a result, this objective of bracketing a rangeresulting of e potential future climate change and investigating the For the three ECHAM> realizations and muchincluding of PCM_A2, PCM_B1, most which changeThese gets is small wetter, within magnitudes absolute the climate of changes class change are (Fig. 2), in predominately sinceto FMI each climate the explain class smaller the has a changes patchiness large that of range in were the FMI observed. change (0.33) relative For in the PCM_A1b realization, many of since the choice of PCMand was presumably intended a to provide smaller aECHAM magnitude lower of model. climate simulated This sensitivity climate baseline discrepancyand change – highlights regional – the compared climate potential to trends,here. the di Nevertheless, even the for use the of long-term both (30-year) models averages in we our consider analysis accomplishes the overall other four realizations there is no change in the aridthe class, since continuous this FMI is are theall driest found class. realizations in every except assessment PCM_B1,tive unit the (i.e., across FMI drier). the values statechanges Changes predominately (Fig. also in 3). become occur FMI For more forA2 are nega- the and all ECHAM_A1b A1b positive and emissionchanges scenarios, ECHAM_B1 (wetter) in FMI the realizations. for than PCM For the PCM_B1, ECHAM model both model. and produces the Note more positive that this extreme was (i.e., contrary to drier) our expectation, PCM_B1, all changes arealso to varies the by initial next class:of wettest the 2.7 climate % mean class. change for Change acrossHowever, the the in all semi-arid fact realizations climate that class ranges class the from toalizations, semi-arid a which a class low both high is contain of ranked arid lowest 17.5 % assessment is units influenced for by that the the change very B1 to wet re- semi-arid. class For (Table all 2). switch to the next wetter class (i.e., changes immediately below the diagonal). For the diagonal are changeschanges to are the mostly next to drier the class. next Under driest the class, ECHAM_B1 but realizations, there are also assessment units that and fairly evenly distributedence across no the change state. for However,plus two all the geographic six adjacent areas realizations: experi- portion thean arc-shaped southeastern of region portion the located between of southernsoutheastern the the Willamette Oregon Ochoco Coast (Figs. Mountains Valley 1 and Range in and Steens Western 2). Mountain in Oregon, and class. This can beagonal seen represents by assessment examining units the that do confusion not matrices change and (Table 3), entries immediately where above the di- Projected changes in climatecentury class change are realizations distributed (Fig. throughout 2).class Oregon The under ranges percentage mid-21st from of 4.4 assessment %a units mean for that of the change 10 % ECHAM_B1 overstable realization all for to six most realizations 18.3 assessment % (Table 2). units. for Thus, The PCM_A1b, climate distribution class with of is units expected that to be change class is patchy groundwater exports, since runo 3 Results and discussion 3.1 Statewide 3.1.1 Climate class and Feddema Moisture Index 30 year (1971–2000) discharge (mm), basedstations. on Wigington data et from al. USriences (2013) Geological Survey use groundwater gage the losses oravailable gains: surplus, a and thus suggestssumed groundwater to imports be (changes in zero storage since are 30 as- year normals are used). Conversely, a three basins are provided in Table 1. This includes the 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , 0 S con- 0 S excludes excludes 0 0 S S values for the 0 S mean more precipi- . Since 0 0 S S , and because 0 S are most of the high elevation values for all assessment units. 0 0 S S 2890 2889 values are mostly negative during the spring and 0 S occur throughout most of the state from November 0 S values from the initial values (Fig. 5b). Note that a negative departure can have 0 0 S S for projected conditions is greater than initial 0 S changes over time. Figure 5a is a time series plot showing the median 0 S , due to less snowpack, and subsequent decreases in spring and summer 0 S are due to reduced winter snowpacks and, subsequently, lower spring and sum- 0 S An example that further illustrates the monthly departure patterns is given in Fig. 6, The observed changes in seasonality (Tables 2 and 4) can be explained by exam- Results for all six realizations suggest large changes from spring and summer to win- which shows theECHAM_A1b realization spatial (see Figs. S22–S26 distribution infive the in realizations). Supplement for Increases results the in forthrough the change other April, in whileperiencing decreases monthly the dominate greatest from declinesmountains, May which in through have June the October. and greatest Thetinues initial to July areas snowpack increase (Figs. in ex- 1 thewinter Wallowa and Mountains 6); through however, June. These increases in fall and in mer snowmelt. However, theredepartures is of no projected similar seasonala pattern positively with valued percent respect departureconditions to during if percent that its month denominator represent is a negative deficit). (i.e., if 1971–2000 departures of projected Through the fall andpositive, winter i.e., seasons (Octoberprecipitation through that goes April), into departurestation snowpack is (Eq. are falling 2), mostly as theIn rain, increases contrast, which in departures generates from more initial summer immediate months surplus (April through and September). Spring lessis and snowpack. low summer precipitation because in of Oregon the Mediterranean climate. This means that the projected decreases 4.2–5.6 % of the assessment unitsing are a projected to 56.2–67.8 be % snowmelt-dominated, reduction represent- of in summer snowmelt-dominated snowmelt units units. – including a complete loss ining how units. Under the remaining five realizations, there is a much larger proportional change: Under PCM_B1 (Table 4), thisdominated, distribution representing experiences a a decline 19.3 to % 10.4 % reduction snowmelt- in the number of snowmelt-dominated spring to winter orchanged summer under to PCM_B1, spring), which except switched to for spring the seasonality one (Table 4). winterter assessment seasonality. Based unit on that the initial5660 distribution assessment of units seasonality had class,as winter 4931 the of seasonality the season (Table state’s 4). with Sinceprecipitation the that seasonality maximum goes is average into defined accumulated snowpackrain-dominated, (Eq. with 2), the this other means 12.9 that % 87.1 being % dominated of by these spring units or are summer snowmelt. sessment units that initially had spring(PCM_A2) seasonality, to with 68.4 a % fairly (ECHAM_A1b). uniformoutliers, The range PCM_B1 of when 56.8 seasonality compared % change with rateswith the are winter clear other seasonality five changes realizations:while (although one the the of rates rounded the for percent assessmentFor summer change units all and is realizations, spring still a seasonality 0.0 change %), are in 42.9 seasonality and is 19.7 always %, to respectively. the next earlier season (i.e., compared with changes in climatethe class. Cascade Seasonality Range in changes western areern Oregon, mostly the Oregon, restricted Blue and to and the Wallowa westernof Mountains portion in assessment of northeast- units the that Northern8.9 change Great % seasonality Basin. for Overall, class ECHAM_A1b, the ranges with percent ever, from a these 2.6 mean % rates of for vary 7.3PCM_B1, PCM_B1 % to zero widely over percent all by six of initial100 % realizations the of seasonality (Table assessment the 2). class. units units How- with For with summer seasonality all winter change. Also, seasonality realizations there change, is except a and large change in as- density of changed assessment units (Fig. 2). 3.1.2 Seasonality class and surplus Changes in seasonality class (Fig. 4) have a much more limited geographic distribution, realization has the highest rate of climate class change (18.3 %; Table 2) and a greater 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect will be ff 2892 2891 ect of increased winter rain and decreased spring and summer ff Throughout the remainder of the Northern Great Basin and the Blue Mountains of A large area of central Oregon and portions of western Oregon, including the The overall e to have lower water surplus values on an annual basis and to shift seasonality from elevations and supply waterValleys and for lowlands human are usesEastern typically Oregon and assessment semi-arid rivers units or viameability generally have aquifers. arid snowmelt a If in and mixture a the have ofis low moderate low annual spring. permeability and and aquifer water water low is moves deficits. per- supported rapidly present, to primarily internal streams through watershed as the snowmelt storage releaseate occurs; of summer permeability meltwater. baseflows In aquifers, are assessment snowmelt unitsaquifers waters and with have be moder- released the to opportunity streams(Wigington more to et slowly, resulting percolate al., in into 2013). higher the Throughout summer baseflows eastern Oregon, assessment units are projected and associated low internal storage. eastern Oregon (Fig. S27 in thestudy Supplement), basin, including the mountains Middle occupy Forkcal small John sources Day portions case of of water river for basins; these however, basins. they Winter are snowpacks criti- develop in the mid and high a reduction in water surplustion from and snowmelt-dominated a systems shifting to rainfall-dominated ofsessment systems) seasonality units, in particularly from numerous as- spring at lower towill elevations. winter result Over (transi- in time, concomitant reductions reductions inexperienced in water downstream streamflows, surplus of although individual these assessmentinfluence reductions of units may the be (Wigington shift from et snow-dominated al.,ment assessment units units 2013). to will The rain-dominated likely assess- resultmuch in some smaller reduction (in in summer relative baseflow, terms) but this than e assessment units with low aquifer permeability of precipitation andlogic meltwater, combined flowpaths with and deep longstreams residence and aquifers, rivers. results times Streams in aswith in lower deep water stormflow these drains hydro- peaks areas fromgon and commonly higher assessment (Wigington have summer units et moderated baseflows to al., streamflows than other 2013). streams For in this Ore- region, results from all six realizations project Water surplus increases with increasing elevations in these areas. Rapid infiltration cades, western portionwith of large the winter snowpacks Northern and Great high Basin; permeability aquifers Fig. (Wigington S27 et in al., 2013). the Supplement) tions of watersheds in theserecharge areas and have streamflow. water Watersheds generally surplus haveage that relatively and contributes low water to drains internal rapidly groundwater water through stor- summer watersheds baseflows. and For into streams, five resulting of ineral the very drying six low future (Figs. realizations, 3less these and influence areas 4) on experience summer that gen- baseflows. should reduce winter streamflowsSandy and case have study relatively basin, is composed of mountains (High Cascades, east flank Cas- 3.1.3 Regional trends The mountainous portions of westernmath Oregon Mountains; (Western Cascades, Fig. Coastbasin, S27 Range, are Kla- in rain-dominated the (winter Supplement), seasonality) with which low include permeability the bedrock. All Siletz por- case study creased flood risk.increased Summer drought baseflow risk, in duecharge such to (resulting the areas from combination should of theability be less should low also snowmelt reduced, aquifer have and permeability). leading increasedsome low winter of Areas to aquifer streamflow, the though with dis- increased perhaps winter high less surplusspring aquifer so will and go because perme- summer towards baseflow groundwater recharge.groundwater should Impacts discharge. be to In mitigated the in sectionprojected below, these we hydrologic high provide changes an permeability in overview areas select of by major the regions patterns across of Oregon. seasonality (Fig. 4; Tables 2 and 4). snowmelt on water availabilitysuch will as depend, geology. ingreater In part, winter on areas rains intrinsic with should watershed low generally attributes, result aquifer in permeability increased and discharge mountainous and terrain, possibly in- because of less snowmelt, cause the projected shifts from spring and summer to winter 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) ∗ set S ff are o ) to mean ∗ ∗ S S during the fall ∗ S is seen in January, ∗ S during this winter period, ∗ S slightly lags Q and watershed positive surplus ( 20.6 %) experience a loss of at least Q − values are reduced during the spring and ∗ will probably continue in the Siletz, because S ff 2894 2893 ratio of 1.07 (Table 1), suggesting that the basin will be directly expressed in streamflow. As a re- ∗ ∗ S is somewhat higher than Q/S ects are largest under the PCM_A1b realization: 12.2 % ff Q increases during the fall and winter in all six realizations due to in- ∗ S ects occur in June (Fig. 7d), where 100 % loss is experienced under . Spring and summer runo ff ff Because the Siletz basin is groundwater limited and hydrologically responsive, it The impacts of projected climate change are relatively straightforward in the Siletz Special mention should be made of the Wallowa Mountains in eastern Oregon monthly runo summer months, because ofproportional increased e PET fromthree warmer of temperatures. the The realizations, largest 78 and %. all but PCM_B1 ( can be inferred thatsult, changes increased in precipitation duringstreamflow the winter increases months of could uptially potentially to be cause monthly 19 a %. complete During reduction spring in and contributions summer, of there modified could surplus poten- (i.e., creased precipitation (Fig. 7c). Thewith largest an of equivalent these increase increases of in ally, 29.6 however, these (PCM_A2) increases to are 77.1 relatively (ECHAM_A1b)Shifts small mm. (Fig. to Proportion- 7d), the ranging from drierby 8.0 losses climate to during 20.8 class %. the occur spring and because summer. gains in fall and winter receives small amounts of groundwater inputs. and similar rain-dominated systems.expected In from terms some of ofseasonality class the (Table distribution, 5). very a The wet small e of (V) change the area to is is wet projected to (W)alizations. have This wet climate would climate, units, compared suggest to with minimal 0.0–4.9to impacts % no drier for to change the climate, the other in basin. five re- In spite of these switches flow from storage. Once soilmoves saturation rapidly occurs through in the December system, (theinto and wettest water streamflow. month), held water However, within thepossibly subsurface suggesting is minimal transitioned groundwater imports,Further in evidence spite of of this low aquifer is permeability. a increased PET during spring and summer, suggesting some minimal residual base- rising period, suggesting that thisThis represents is the time balanced needed by for a soil pore lag space in to the fill. declines that occur due to reduced precipitation and ity, and low aquifer permeability,low and to they moderate are soil dominatedcontributions by to permeability. mountainous As basin terrain hydrologic ageologic and function result, controls, on the each an timing assessmentare and areal very unit magnitude basis. similar of makes Because in similar this ofa basin climate steep (Fig. and dissected 7b): low landscape infiltration,winter result limited rain in groundwater delivery. As storage, a and a fasthighest result system of of that these the responds combined factors, quickly three Siletz to case peak the discharge study high is basins the (Figs. 7–9). The Siletz River basinin (Fig. the first 1a; region Table wethe 1) Supplement). described is The (mountainous Siletz in portions is the ofonly fairly uniform western Oregon three in Oregon; Coast HL classes, Fig. composition Range, and S27 (Fig.(Table 5). and 7a), in with initially All occurs the having of same the climate, basin’s assessment seasonality, and units have aquifer very permeability wet climate, winter seasonal- the highest accumulationsmallest of relative snowpack changes in inence the changes, our in six state, which some modeling andsnowmelt high realizations. that elevation are sustains assessment However, summer projected units they baseflow) shift do to to from spring experi- summer have seasonality. (late the 3.2 Case study basins 3.2.1 Siletz River basin permeability aquifers will have littlesnowpack internal loss, water whereas storage assessment to moderateable units to the with store influence moderate some of aquifer winter permeability precipitation and will release be it as(Fig. summer S27 baseflow. in the Supplement). The Wallowas, along with the High Cascades, have spring (snowmelt-dominated) to winter (rain-dominated). Assessment units with low 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | stays ) (Stout Q is approx- Q Oncorhynchus kisutch 2896 2895 is due to the recharge of the high permeability Q erson et al., 2008; Tague et al., 2008). Above 1200 m, ff 0.96; Table 1), suggesting minimal groundwater exports sharply declines, as temperatures fall and more precipi- ∗ = ∗ S Q/S ( ∗ S and the December peak in rises steadily in October and November. The lag between the November then peaks in May due to snowmelt; this water, along with baseflow, sustains ∗ ∗ ∗ S S S The mixed hydrologic characteristics of the Sandy River can be seen in Fig. 8b, These geologic and climatic controls can be seen in the initial HL distribution for Elevation controls the form of winter precipitation in the Sandy, which can fall as Changes in flow that result from climate change could have implications for water- from the basin. peak in aquifer. After November, tation is stored asin seasonal the snowpack. Peak Siletz winter (Fig.elevated discharge through 7b), is April, since therefore because lower precipitationstormflow of than generated is by baseflow not rains contributions in occurring the frombasin. lower, as more the hydrologically rain. upper responsive portion Sandy However, ofhigh and the levels of baseflow throughimately the equal drier to summer months. Over the year, Western Cascades (for example, the Clackamas,Umpqua North basins; Santiam, Fig. McKenzie, and S3 North 2013; in Wigington the et Supplement; al., Sproles 2013). et al., 2013; Surfleetwhere and Tullos, the Sandy (Fig. 8a;permeability Table 5): and the spring upper seasonality (due (eastern)quent to portion spring winter is snowpack snowmelt). dominated accumulation In and byinated subse- contrast, high by the aquifer low lower aquifer (western)the permeability portion HL and of composition winter the of seasonalityunits basin the (due in is Sandy to the dom- is winter Sandyby less are rains). very these uniform Thus, wet, than units as the variescharacteristics in Siletz. between the similarly And the Siletz, apply while the upper to all delivery and of other and lower the processing basins portions of that of water are the a basin. mix These of HL High Cascades and (Sproles et al., 2013).snow The transition upper and portions so of haveIn a the contrast, snowpack Sandy the with commonly a lower liecumulate distinct portions throughout above accumulation are the the and rain-dominated, winter. melt rain- and period. snow commonly does not ac- a seasonal snowpack accumulates throughout the winter and melts during the spring rain, snow, or aCascades rain-snow mix. is A 800–1200 m general (Je threshold for the rain-snow transition in the western slope of theprovinces (Tague Oregon and Cascades, Grant, cancades) 2004; are be Tague characterized broadly et by younger classified al.,and basalts 2008): into snowmelt with upper high two percolate aquifer elevations vertically geologic permeability,rainy (High where and season rain Cas- provide until steady snowmelt. The rechargeized lower from by elevations the a (Western onset Cascades) dissectedprecipitation are of landscape, inputs. character- the low aquifer permeability, and are more responsive to 3.2.2 Sandy River basin The Sandy River basinthe (Fig. Oregon 1b; Cascades, Table and 1) occursof lies in western on our the Oregon; second western Fig. region slope S27 (central of in Oregon Mount and the Hood portions Supplement). in This basin, as well as much of the habitat for salmonids, including threatened cohoet salmon ( al., 2012).modifications, Modified and streamflow large-scale and changesare temperature factors to implicated regimes, in ocean human-caused declines of conditions2012). habitat this In and species an in evaluation marine the of Oregon potential productivity reduced coast climate summer range sensitivity, Stout streamflows (Stout et and et al. elevated al., water (2012)rearing temperatures concluded would that habitat reduce available for cohodisease, and salmon elevated metabolic and demand. increase stresses associated with competition, ports could further reduce spring and summer discharge. dependent uses within thethe Siletz. Siletz and Irrigation, similar industrial, Coastimportant, Range and basins especially municipal is minimal, use to although of towns such use water along can in be the locally coast. These river systems provide critical of the limited groundwater contributions. However, any reductions in groundwater im- 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | values ∗ S (Fig. 8c and ∗ occur in August S ∗ S . The changes are ∗ S . Changes in hydrology ff suggest the possibility that ect the ability of the upper ff ∗ S ), coho salmon, and steelhead will a are dramatic, and should result in ∗ ∗ S S could increase the likelihood of moder- ∗ S 2898 2897 O. tschawytcha during the drier summer months: reduced snow- ∗ S and decreases in summer ∗ ects S ff 192.8 (PCM_A1b) mm decrease in June, representing 26.6– − , experiences a 55.3 (PCM_B1) to 90.0 (ECHAM_A2) mm increase in Q ects on seasonality are reflected in the changes in ff ) (Good et al., 2005). Spring Chinook salmon, in particular, require cold wa- 73.7 (PCM_B1) to − (Fig. 8c), representing a 36.9–60.1 % projected increase (Fig. 8d). This transition The Sandy basin supports populations of Pacific salmon and trout including threat- The increases in winter These e The HL climate classes do not change within the Sandy, remaining very wet (V) un- ∗ O. mykiss Fig. S27 in the Supplement).drier The than MFJD is the the two largest western of basins. the three Winters basins, here and are is colder much than the maritime climate increased winter streamflows result in increasedthermal scour regimes of spawning impact gravels metabolism and2008). altered and growth of juvenile salmonids (Crozier3.2.3 et al., Middle Fork John Day RiverThe basin Middle Fork Johnflank of Day the (MFJD; Blue Mountains Fig.(the in remainder 1c; northeastern of Table the Oregon, 1) Northern and Great occurs originates Basin within and on our the third the Blue region Mountains southeastern of eastern Oregon; contribute to persistence of thesewhich populations the under groundwater-rich current upper conditions.Chinook basin The could degree salmon to continue and to otherity support of salmonid over-summering reductions of populations in willcould groundwater recharge be also and have dependent snowmelt implications upon runo for the winter sever- survival of salmonid embryos and juveniles, if 2008). Thus, relative changesthe in presence streamflow should of be thehaving less High faster, for shallow Cascades this subsurface deep systems basin, groundwater (Tague because et system, of al., compared 2008). withened areas fall and spring( Chinook salmon ( ter during the summer months tothe fall, support and adults the holding deep in groundwater the sources river that prior provide to cold spawning summer in streamflows likely that have adeep High groundwater Cascades could component) mediatepermeability streamflow occurs of response the within (Tague upper et geological portionsstreamflow al., of formations during 2008). the the where The basin summer are high emerge expected months, to as as mitigate springs rain the lower and impacts in snowmelt on the percolate watershed (Tague vertically and and Grant, 2004, 2009; Tague et al., lower spring and summer flows. However, the Sandy (and similar western slope basins Surfleet and Tullos, 2013). Decreases in summer d): 69.5 % reductions. Proportionately, however, the(83.8–100.0 greatest % losses reductions). of This lossSandy to of sustain summer streamflow during the summer. the Sandy River couldwithin experience the increased same likelihoods water ofate year. both Greater flooding, flooding winter but and mitigatein drought the snowpack likelihood and, for therefore, extreme extreme flooding rain-on-snow events events due (Jones to and reductions Perkins, 2010; sulting in more winterthe rain. highest December, which typicallyS has the mostfrom precipitation and snow topack rain leads also to a decreased summer snowmelt and large reductions in This change is evenwinter more seasonality dramatic switch from forsenting 4.8 low a and permeability 100 21.4 % %, areas loss to of (Table 0.0 5): spring and seasonality. spring 26.2 %, and consistent respectively, repre- across all sixPCM_B1 realizations results (Fig. are less 8c), thanincrease though the due the other to absolute five. increased During magnitudeincreased precipitation. the Compounding of temperatures, wet the which the winter enhanced cause months, precipitation the are rain-snow transition to rise in elevation, re- der all six realizations (Table 5). Therewith are high major changes aquifer in permeability seasonality, however:and and units 4.0 spring % or of winterand basin seasonality 17.7–73.8 area, %, initially respectively, respectively represent representing (Table 69.8 spring a 5). seasonality 19.7–100.0 These % class loss numbers area. in Excluding change high PCM_B1, to permeability, the 0.0–56.0 range of loss is 63.3–100.0 %. 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ ff ff Q/S then be- ∗ for January S ∗ S does not rise in Q in the MFJD has a bi- ∗ S ect on the climate class of the ff values partly reflect irrigation usage. are low from July through the end of ff Q and ∗ 2900 2899 S increases in the MFJD during the fall and winter months ∗ S . The MFJD is representative of many basins in eastern Oregon ff curves for the MFJD further illustrate how winter snowpack dominates peaks. Values for both Q Q and ∗ S Under all six realizations, While projected climate change scenarios had little e The The MFJD is the most diverse of the three basins with respect to HL composition (Ta- range from 130.2–312.8 % for the MFJD, vs. 8.0–20.8 and 55.2–90.1 % for the Siletz ality increases from 40.8snowmelt-dominated to area 52.4–76.1 (43.5–59.6 %. %, This excluding PCM_B1). represents a 19.7–59.6 %(Fig. reduction 9c). in While the overall trendMFJD is has similar the to lowest the magnituderange other of from two change. 8.0 basins For (PCM_B1) (Figs. example, to 7c departures 19.3and and (PCM_A1b) in 60.6–98.9 8c), mm, mm the compared for with the rangesof Siletz of the 29.6–77.1 and basin Sandy, values respectively. While onproportional these an are absolute changes the basis, when the smallest January compared departures to represent the initial largest values (Figs. 7d, 8d and 9d): values units, dry units mostly increaseall but in the area, B1 from realizations; 32.3As slight occurred to reductions with 44.8–52.0 to % the 31.8 Sandy, of % thespring basin occur MFJD for area also (snowmelt-dominated) both is under to those expected to realizations. with winter experience spring major (rain-dominated) seasonality shifts seasonality decline from in (Table area 5). from Units 59.2 to 23.9–47.6 %, while winter season- Siletz and Sandy basins, thisexpected is to not substantially the decline case10.0 % for under of the all basin MFJD. but Wet areaPCM_A2 assessment to the and units 0.0–2.2 two PCM_A1b % are B1 realizations. (Table 5);tively Under scenarios, all little ECHAM_B1 from wet and change climate a PCM_B1, in unitsunits total there disappear area also of is under of decreases rela- the wet forslightly units five increase of in (9.1 area the and to scenarios, 11.3 59.2 %, % from under respectively). 57.8 ECHAM_B1. Area to In of contrast 47.3–56.9 %. to moist the Moist wet units and moist month when the water year in September;Winter low and summer spring runo rechargeprovides some of groundwater the contributions moderate toratio permeability (0.78; baseflow. However, Table aquifer 1) the suggests basin’s in that, low the overall, the upper MFJD basin may be losing groundwater. then increases in March, in response to snowmelt, and peaks in May during the same remains low throughout the winter, though gradually rising through February. Runo per and middle areas,basin the area), lower and basin so is contribute comprised little to of streamflow. units withits dry hydrologic climate character. (32 As %modal occurred of distribution with the (Fig. Sandy 9b).as basin, Values rain, rise but then in fallgins November, in as to December precipitation and rise January initially againresponse due occurs in to to snow the March, accumulation. November dueBecause rains to less because snowmelt, rain pore falls and space in in peaks the the in MFJD soil than May. column in must the first Sandy, and fill. for a shorter period, runo flow. Although these assessment unitsas comprise only the 10 key % sources of of basinwith water area, moist for they climate the function system. andaquifer The spring permeability. rest seasonality These of (49 assessment the % upperless units of basin groundwater contribute basin than is less the area), mostly water uppermost units with per assessment low unit units. to In area moderate contrast and to the MFJD’s up- spring seasonality (i.e., snowmelt-dominated)winter seasonality in at the the easternley). western Eighty-five headwaters mouth percent to (which of the have dry15 basin the % with has lowest of moderate elevations the aquifer in area,ability. permeability; the While located the val- all in remaining of the the middletherefore contributed units of to in the streamflow, the the basin hydrologic Siletzfluenced character (Fig. by of and 9a), headwater the Sandy assessment has MFJD units basins is low that stronglythis had aquifer are in- area very wet perme- has and wet snowmelt moderate climate, driven. aquifer and In permeability, addition, and so contributes groundwater to base- snowpack dominates the hydrologic characterthe of majority the of region, runo andthat snowmelt are comprises similarly snowmelt-dominated. ble 5; Fig. 9a). The basin is comprised of eleven HL classes, which vary from wet with of western Oregon, and summer months are dry and warm. As a result, seasonal 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ∗ S 1.0 mm − should lead ). Winter and ∗ S ects of climate ff , since the latter ∗ S set by groundwater ff is not likely to have ma- ff represents an increase in rain http://www.dfw.state.or.us/fish/ ∗ S 0.78; Table 1). Reduced spring and during the spring could decrease the ∗ = 40.5 mm) and smallest in July ( ∗ S − (Fig. 9b), increased winter is reduced from May through July (Fig. 9c). ∗ ∗ S Q/S s of 118 and 183 wild adult chinook salmon, will not be substantially o S 2902 2901 ff ∗ (Ebersole et al., 2014). The e S 17.3 to 0 and − S Q should approach August and September values of 2.2– ff ects, including mortality, on cold-water fishes (Arismendi et al., ects on salmonids due to reductions in spring and summer ff ff could reduce the number of these cold-water patches. Given the are likely to be greater than our estimates for http://www.dfw.state.or.us/news/2013/july/071213.asp ∗ 0 ; S S ects, since agriculture is the largest private sector economic activity in ects of reduced spring values (Fig. 9d). erences in temperature between cold-water patches and corresponding ff ff ff ∗ ects of these three factors, salmonids in the MFJD could be particularly S ff ects on overwintering mortality of salmonids, since initial values and absolute ff Low summer streamflows and high summer water temperatures are currently a con- Given the relationship between flow. The basin should alsoand non-threatened be salmonids, most due vulnerable to with relatively high respect magnitudes to of impacts changes in to habitat threatened combined e vulnerable to climate change. 3.2.4 Relative vulnerability of salmonids Based on our analysisand of similar basins the occurring three inBlue the case eastern Mountains study portion of basins, of eastern we the Oregonvulnerability Northern would (Fig. with Great S27 respect expect Basin in to the and both the the MFJD relative Supplement) – loss – of to winter have snowpack the and highest summer stream- most at risk. Thewater single patch most occurrence importantchange was factor on May that May predicteddoes the not probability incorporate of moisturetrends cold- in deficits spring (compare Eqs. 2 and 3). Thus, the projected in multiple negative e 2013; Ebersole et al.,number 2014). of Third, cold-water reduced patchestures that during salmonids late use July/early August. to Ebersoleconfluences escape et at high al. (2014) three mainstem examined basins tempera- tributary-mainstem that in cold-water northeastern patches Oregon, including werethe the MFJD). present Di MFJD. at They 53 found streamflow % were of greatest all during observed the confluences hottest time (60 % of for the day, when cold-water fish are have significant ecological repercussionsFalke for et anadromous al., fish 2013). (McMillancould E et be al., even 2012; morewater severe, will due mean to less available several habitat.flows factors. Second, First, may the increasingly reductions timing of in co-occur minimum the with summer amount stream- the of period of maximum temperatures, resulting changes are low. However, altered thermal conditions during the winter months could significantly stress populations ofing salmon distributional and patterns trout and in useand the of 2013, basin thermal the refuges (Li MFJD (Torgersen etrespectively, et experienced due al., al., die-o to 1994), 1999). In driv- high 2007 summer water temperatures ( Although this is not a largeserious area, reductions local in e spring and summerthe discharge basin. could have cern for salmonid survival in the MFJD (Good et al., 2005). Summer temperatures can to modest increases in theLoss slope of of spring the snowmelt dischargethrough should curve June, between cause while November a July and runo substantial April. 2.4 reduction mm. in The e discharge fromif April the basinsummer is discharge losing will negatively groundwater impact agriculturethe (i.e., in MFJD the area, to which flood uses water irrigate from approximately 1430 ha of cropland (NMFJDRLAC, 2011). and large decrease inless the winter snowpack, amount snowmelt-derived ofThese moisture declines available are for largest snowpack. infor June As all ( six a realizations). On result a of of proportional basis, the however, initial the July loss represents 100 % and Sandy, respectively. This shift to greater January and abundance of steelhead redds (Falkein et al., steelhead 2013) (McMillan and the etjor expression al., of e anadromy 2012). Increased winter runo news/071907.asp spring temperatures and hydrologic regimestributional also patterns strongly of regulate life salmonids history in and the dis- basin; for example, influencing the distribution 5 5 25 20 10 15 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , and basin 0 S are mediated by will increase win- ∗ ∗ S S ected a modest number of ff are relatively small, compared ∗ ects. The MFJD, in northeastern ff S ect on timing of delivery. Also, because emission scenarios (A2, A1b, and B1). ff 2 are proportionately small. The Sandy basin, ∗ 2904 2903 S ects on salmonids will be highly contingent upon the ff ect on spring and summer baseflows, high aquifer permeability ff ects of these changes in timing and delivery of ff generally increases in the fall and winter, representing a loss of snowpack, ects of relatively large changes in winter and summer ects on salmonids. The Sandy basin, as well as others in the High Cas- ff ∗ ff S ects of hydrologic and thermal regime shifts on phenology and environmental ects of climate change. Decreased spring and summer snowmelt from reduced ff ff could also have greater impacts on salmonids in the MFJD and similar areas, com- values are initially large, changes in While the ECHAM model has higher sensitivity to climate change than the PCM The specific e ∗ ∗ variability of climate change. In addition, results for statewide seasonality, these impacts, compared withother the irrigated Sandy. areas Our inthe analysis semi-arid e suggests eastern that Oregon theS could MFJD be and particularlypared vulnerable with to other regions. model (Intergovernmental Panel onwe Climate found Change, 2007), that as statewide(Fig. discussed changes 3) previously, were in greater climate for class the (Tables PCM 2 model. and This 3; demonstrates Fig. the anticipated 2) regional and FMI pected to have anin e such basins has theOregon, potential is to the moderate most these dependentmost e of impacted the area, three because of basinsmate both on classes. changes spring Moderate in snowmelt. aquifer seasonality Thus, permeability and it in switches is the to the drier upper cli- basin is less able to reduce pacts in diverse hydroclimatic and geologiccould settings, support and management. to Basins illustrate such howmeability, as have the the relatively low approach Siletz internal are water rain-dominated storage withinto and, low the as per- streams a and result, produces water very drainsready low rapidly delivered summer as baseflows. rain, Because there precipitation isS is relatively little al- e however, includes higher elevation areasexperience that shifts accumulate from snowpack, snowmelt-dominated and to those rain-dominated. While areas this would be ex- because and decreases in the spring and fall, due tothe reduced snowmelt. geology of thedemonstrate basin. how We the discuss HL in approach can detail be results useful from for three understanding climate case change study im- basins to declines to 10.4 %, representing a 19.3 % reduction. The shifts in seasonality occur units to 4.2–5.6 %67.8 snow-dominated % reduction under in the snowmelt-dominated units. five Under realizations, PCM_B1, representing snow-dominated area a 56.2– fect the distribution of HLsgeneral in circulation Oregon, models using run climate outputStatewide with from three results the CO found ECHAM and thatstudy PCM units changes (4.4–18.3 in %). However, climatefive there of class were the major a realizations, changessummer with in seasonality. 56.8–68.4 Although seasonality % seasonality class changed loss less for of– under spring 19.7 the PCM_B1 and seasonality realization 42.9 and % for 100still % spring and substantial. loss summer of Overall, seasonality, respectively – Oregon the shifts changes were from initially having 12.9 % snow-dominated suitability for growth, development, and survival (Crozier et al., 2008). 4 Summary and conclusions We examined how a range of mid-21st century climate change realizations would af- the basin, however, so anynegative decreases e in flowcades, or east increases flank in Cascades, and temperature easternin could portion the have of Supplement), the Northern shouldsince Great have the Basin intermediate e (Fig. S27 vulnerability withter rains respect and reduce to spring hydrology, andwill summer snowmelt. moderate However, high these permeability impacts. aquifers net E e et al., 2012). The Siletzof basin, western as Oregon well (Fig. as S27 other innerable the basins to Supplement), within climate should the be change, mountainous theto since portions least current changes hydrologically conditions, vul- in and winter becauseand there summer is relatively flows. little Summer linkage streamflows between and winter rains temperatures are already a concern in suitability and availability, particularly during the summer months (see also Ruesch 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects. ff (Figs. 7b, ∗ S and to make inferences Q ff ects (Wigington et al., ff for most of Oregon. We ff curve from a similarly clas- erent trajectories of the A2 ff ff would allow for more objective ∗ S from et al., 2000). Thus, our finding of greater Q ć results can then be used to assess overall , Eq. 3, for basins) to evaluate these e ∗ ects of climate change on individual basins ff ff 2906 2905 S ects from any future changes in extreme hy- enovi ff ć ects of constituent assessment units. We make use ff ect basin streamflow, using aquifer permeability class curve for the ungaged basin, which can be produced ff ects of geology. ∗ ff S erences in the results and model performance for CMIP3 and ff eld et al., 2013a, b). ffi is not quantified, so our conclusions regarding future discharge must be in- ff emissions, results consistently showed greater impacts for the A1b scenario, 2 , Eq. 2, for assessment units, and 0 S values (Figs. 4, 5, 7, 8 and 9) were variable with respect to the two models. Regard- The strength of our approach is that it can be applied to similarly classified, ungaged Another possible limitation is that our study does not use the most recently available Our analysis has several limitations. First, the relationship between modified surplus In this paper, we have demonstrated that the Wigington et al. (2013) HL approach ∗ vulnerability with respect to quantity and timing of discharge, as well as resources and climate variables (e.g., temperature, precipitation,processes winds, humidity, (e.g., etc.) El and dynamical Niño-Southernare Oscillation, few storm substantive tracks, di etc.)CMIP5 (She conclude that there basins. In such afor case, any the basin inet Oregon al. through (2012) the snowmelt use model,sified, of is gaged the compared basin. 400 with The m the interpreted PRISM runo runo data and the Leibowitz resents an earlier generation ofCMIP5, models most (and greenhouse of gas thethe scenarios) new basic compared Representative Concentration to assumptions Pathways greenhouse andclosely gas model scenarios onto map structures the quite are previousnarios. very Initial generation diagnostic similar. (Special analysis Also, Report of on results Emissions for North Scenarios) America sce- across a wide range of HL approach could serve as2013). a These framework factors for could evaluating these exacerbate e or mitigate against climate impacts. climate change data. Wedataset note that that was our assessed analysisPanel in on made the Climate use Change, IPCC of 2007). fourth(the Although the CMIP5 assessment more CMIP3 ensemble), recent report we multi-model modeling did (Intergovernmental results notin use are the these, available IPCC in fifth part assessment because report the are model not runs yet assessed published. In addition, while CMIP3 rep- mental Panel on Climatewith Change, an understanding 2012). of Whileresults how our would average not monthly analysis be hydrologic cando appropriate conditions provide not for will flood deal managers change, or with the of drought the planning. influences which Third, of could the vegetation, influence Oregon land vulnerability HLs use, to or climate other change human activities (Nolin, – 2012) all – although the heaviest downpours, which are likely to increase with climate change (Intergovern- period. As such,droclimatic our events. study For example, ignores our e approach does not address the frequency of the then utilize the relationshipabout between how climate modified change surplus willto a and account runo for the mitigating e and runo terpreted for each basin8b, by and examining 9b). the Use relationshipsconclusions. of between Second, a our model that analysis estimates makes use of 30 year normals for the 2041–2070 of the classification itselfclasses – – as changes well in as theand changes in distribution the of variables used theThe to climate define two and these modified classes seasonality (FMI, surplusfrom Eq. rain terms 1, and represent snowmelt, and the so amount are the of major water drivers entering of runo the system and A1b emission scenarios for the mid-century period thatcan we provide analyze. a method for mappingHLs and provide interpreting vulnerability integrated to measures climateof change. of watersheds. The This the information key allowsprovides drivers for a a of systematic broad-scale understanding the (e.g., of statewide)cycle hydrologic how analysis characteristics across climate that geographies. change In willcan impact addition, be the e evaluated hydrologic by combining e ing CO compared to A2. Whilethe the end A2 of scenario the ultimately 21stframe results Century, we A1b in consider produces the in greater this highest emissionsimpacts paper emissions for under (Naki the by mid-century the time- A1b scenario is consistent with the di S 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , orts, Science, , 1991. ff 10.1038/nature04141 , 2011. , 2007. 10.1016/0034-4257(91)90048-b 10.1002/joc.2137 2908 2907 . , 2011. 10.1073/pnas.0701685104 , 2008. 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K., Karambiri, H., Lakshmi, V., Liang, X., 5 5 20 25 15 10 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | semi-arid, = dry, S = Mean Eleva- Relief ∗ summer. moderate, D = = Q/S ) tion (m) (m) 2 wet, M spring, u = = 2916 2915 very wet, W = fall or winter, s Site No. Area (km = values from Wigington et al. (2013). ∗ ECHAM_A2 ECHAM_A1b ECHAM_B1 PCM_A2 PCM_A1b PCM_B1 MEAN Q/S Proportion of assessment units that changed from initial climate or seasonality class Attributes of the Siletz, Sandy, and Middle Fork John Day case study basins. Drainage StreamSiletzSandyMiddle Fork John Day 14044000 USGS 1334 Drainage 14305500 14137000 0.78 523 681 1455 1.07 0.96 1695 400 1005 1051 3161 ws 0.00u 0.673ALL 1.00 0.087 0.00 0.684 0.089 1.00 0.00 0.619 0.080 1.00 0.00 0.568 0.074 0.643 1.00 0.00 0.083 0.197 1.00 0.00 0.026 0.564 0.429 0.000 0.073 0.905 VW 0.175M 0.094D 0.161S 0.236 0.123A 0.148 0.018ALL 0.182 0.00 0.090 0.138 0.140 0.047 0.017 0.060 0.113 0.00 0.219 0.037 0.136 0.005 0.281 0.213 0.044 0.208 0.160 0.049 0.324 0.023 0.00 0.277 0.028 0.119 0.00 0.042 0.070 0.175 0.110 0.085 0.183 0.168 0.00 0.057 0.137 0.053 0.027 0.222 0.100 0.045

arid. Seasonality classes: w Climate Seasonality = A Table 2. by realization. Climate classes: V area and Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | arid. 81 81 720 704 720 704 5660 1143 1031 1981 1143 1031 1981 5660 = TOTAL TOTAL 81 81 720 704 720 704 5660 5660 1143 1031 1981 1143 1031 1981 TOTAL TOTAL 7 77 46 81 (1) (0.951) (0.0232) (0.00353) semi-arid, A 35 81 33 81 (1) (1) = (0.0167) (0.0177) 36 0 165 0 1971 1935 (0.16) (0) (0.995) (0.977) (0.0349) (0) dry, S 142 0 127 0 1946 1948 (0.138) (0) (0.123) (0) (0.983) (0.982) = 42 0 0 150866 0 0 993 889 113904 0 0 128 0 0 (0.84) (0.182) (0)(0.862) (0) (0.161) (0)(0.877) (0) (0.213) (0) (0) (0.963) (0.0597) (0) (0) 2918 2917 moderate, D 107591 0 0 0 169576 0 0 0 = (0.818) (0.839) (0.148) (0) (0) (0) (0.0936) (0) (0) (0) 54 0 0 0 662 155554 0 0 0 (0.94) (0.136)(0.787) (0) (0) (0) (0.0472) (0) (0) (0) Projected (2041–2070) – PCM_A2 Projected (2041–2070) – ECHAM_A2 Projected (2041–2070) – ECHAM_A1b Projected (2041–2070) – ECHAM_B1 wet, M 170974 0 0 0 0 126 0 0 0 0 1036 (0.236)(0.852) (0) (0) (0) (0) (0.175)(0.906) (0) (0) (0) (0) = 158988 0 0 0 0 101 0 0 0 0 1089 (0.14) (0) (0) (0) (0) (0.219) (0) (0) (0) (0) (0.864) (0.953) VWMDSA VWMDSA (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0)(0) (0) (0) (0) (0) (0) (0) (0) (0) (0)(0) (0) (0) (0) (0) (0) 550 594 (0.764) (0.825) VWMDSA VWMDSA (0) (0) (0) (0)(0) (0)(0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0) (0)(0) (0)(0) (0.00194) (0) (0) (0) (0) (0.00151) (0) (0.0494) 562 619 (0.86) V S A SA 0 0 0 0 0 0 0 0 0 V D D 0 0 0 M 0 0 M very wet, W W W 0 (0.781)

TOTAL 550 1144 745 1017 2090 114 TOTAL 594 1162 698 1017 2073 116 =

nta (1971–2000) Initial nta (1971–2000) Initial A 0 0V 0 0SA 4 0 0 0 0 0 0 0 0 0 V S 0 0 0 3 D 0 0 0 D 0 0 2 M 0 0 M 0 0 W 0 W 0

TOTAL 562 1146 709 1016 2100 127 TOTAL 619 1190 718 1038 2011 84

nta (1971–2000) Initial nta (1971–2000) Initial Continued. Confusion matrices for initial (1971–2000) vs. projected (2041–2070) climate class by Table 3. Table 3. realization. Entries are numbersof of the assessment initial climate units.total; class Parenthetical values represented number sum in to is the one the byonal projected row). proportion represent climate Diagonal changes class entries to shown (cell drier inClimate value conditions, bold. classes: divided while Entries V by entries to row the to right the of left the represent diag- wetter conditions. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 81 81 720 704 720 704 1143 1031 1981 5660 1143 1031 1981 5660 TOTAL TOTAL 0 81 63 84 (1) (0) (0.778) (0.0424) 7 7 7 0 0 722 722 722 (0) (0) 286 0 4931 5660 4931 5660 4931 5660 1897 1868 TOTAL TOTAL TOTAL (0.943) (0.277)(0.958) (0) 0 0 0 0 0 0 0 0 0 (0) (0) (0) (0) (0) (0) (0) (0) (0) 943 228745 0 0 (0.915) (0.324) (0)(0.723) (0) 0 0 0 0 0 0 (0) (0) (0) (0) (0) (0) 236 228 275 (0.327) (0.316) (0.381) 2920 2919 0 0 0 0 (0) (0) (0) (0) 238476 0 0 0 655 (0.93) (0.676) (0.208) (0) (0) (0) w s u w s u w s u (1) (1) (1) (0) (1) (0) (1) (0) (1) Projected (2041–2070) – PCM_B1 4931 4931 4931 Projected (2041–2070) – PCM_A1b Projected (2041–2070) – ECHAM_A2 Projected (2041–2070) – ECHAM_B1 (0.673) (0.684) (0.619) Projected (2041–2070) – ECHAM_A1b 0 0 0 0 0 (0) (0) (0) (0) (0) 905 202 0 0 0 0 1111 (0.281) (0) (0) (0) (0) (0.972) (0.792) summer. s 486 s 494 s 447 u 0 7 u 0 7 u 0 7 w w w

=

TOTAL 5417 243 0 TOTAL 5425 235 0 TOTAL 5378 282 0

nta (1971–2000) Initial nta (1971–2000) Initial nta (1971–2000) Initial VWMDSA VWMDSA (1) (0) (0.0696) (0) (0) (0) (0) (0.222) (0)(0) (0) (0) (0.0854) (0) (0.057) (0) (0) (0) (0) (0) (0) (0) (0) (0)(0) (0) (0) (0) (0) (0) 720 518 (0.028) (0.719) spring, u = A 0 0V 0 0S 0 A 0 0 0 0 0 0 113 0 18 S 0 0 0 0 V D 0 0 88 D 0 0 0 M 0 49 M 0 0 W 32 W 0

TOTAL 752 1160 743 1056 1886 63 TOTAL 518 1107 714 973 2183 165

nta (1971–2000) Initial nta (1971–2000) Initial Continued. Confusion matrices for initial (1971–2000) vs. projected (2041–2070) seasonality class fall or winter, s = Table 4. by realization. Entries are numbers ofof assessment the units. initial Parenthetical seasonality number class isby the represented row proportion in total; the values projected sumw seasonality class to (cell one value by divided row). Diagonal entries shown in bold. Seasonality classes: Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7 7 7 722 722 722 5660 4931 4931 5660 4931 5660 TOTAL TOTAL TOTAL 0 0 0 0 0 4 (0) (0) (0) (0) (0) (0.571) 0 0 0 0 1 0 (0) (0) (0) (0) 312 258 580 (0.432) (0.357) (0.803) 2921 2922 (0.000203) (0) Projected (2041–2070) – PCM_A2 Projected (2041–2070) – PCM_B1 w s u w s u w s u Projected (2041–2070) – PCM_A1b (0) (1) (0) (1) (1) (0) (0.429) (1) (1) 4931 4931 4930 (0.568) (0.643) (0.197) s 410 s 464 s 142 u 0 7 u 0 7 u 0 3 w w w

TOTAL 5341 319 0 TOTAL 5395 265 0 TOTAL 5072 584 4

nta (1971–2000) Initial (1971–2000) Initial nta (1971–2000) Initial Hydrologic landscape (HL) composition (% area) of three case study basins for ini- Continued. HL Class 1971–2000Siletz River ECHAM_A2VwLML ECHAM_A1bVwLMM ECHAM_B1VwLTH PCM_A2WwLMM PCM_A1b 63.25WwLTH PCM_B1 34.81Sandy River 1.94 63.25 – 31.83 – 1.81 63.25 2.97 31.83Middle Fork John 0.13 Day River WsLML 63.25WsLMM 31.83 –WsMML 2.97 63.25WsMMM 1.94 31.83MwLMM 4.42MwMMM 63.25 1.81 2.16 2.97MwMTM – 24.57 3.39MsLML 0.13 63.25 0.28 2.22MsLMM 34.81 8.25 2.97MsMML – 1.94MsMMM – –MsMTM – 15.90 10.23 – 15.08 4.53SwMML 2.22 –DwLMM 1.94 21.10 –DwMML – 23.62 0.28DwMMM 15.90 – 15.08 5.74DwMTM 2.22 1.94 – – 12.51 5.79 – – – – 9.58 3.48 16.89 24.36 0.25 10.12 – – 5.74 3.48 18.29 12.51 11.38 – 3.37 17.32 – 5.58 9.18 – 3.48 – 0.28 8.25 18.64 5.74 – 18.29 – 15.08 – – 17.32 – 0.25 – 16.11 22.01 9.18 5.74 2.22 – 4.54 – – 9.82 – 17.32 12.51 – – 5.74 – – 3.48 4.64 22.80 0.03 2.22 17.32 24.22 3.48 3.37 11.71 2.28 – 9.18 25.94 3.48 16.64 2.22 – – – 9.82 17.32 9.18 – – – 0.03 – 4.64 0.69 0.28 0.28 – – VwHMMVwLMLVwLMMVsHMM 3.99VsLMM 9.33 12.11 69.78 73.77 4.79 16.90 9.33 73.77 – 16.90 – 9.33 48.18 16.90 48.18 – 9.33 16.90 – 73.77 9.33 25.59 16.90 17.73 25.59 9.33 16.90 – 9.33 – – 56.04 – – Table 5. tial (1971–2000) conditions andSupplement projected for (2041–2070) HL realizations. class See definitions. key in Fig. S2 in the Table 4. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

43

ECHAM_A1b;

case study 44 (b) ECHAM_A2;

(a) PCM_B1. (f) 2924 2923 PCM_A1b; (e) Middle Fork John Day. (C) ; Sandy; (B) (C)Middle Fork John Day. Change in climate class by realization: (a) ECHAM_A2; (b) ECHAM_A1b; (c) (c) (b) ECHAM_A1b; ECHAM_A2; (a) realization: by in class climate Change

PCM_A2; (d) Sandy; 2. Figure PCM_A2; (d) PCM_B1. PCM_A1b;ECHAM_B1; (f) (e) Elevation map of Oregon with major features and locations with locations major and three1. Elevation Oregon features of of map

(B) 1 2 3 4 5 Change in climate class by realization: Elevation map of Oregon with major features and locations of three case study basins: basins: (A) Siletz Figure Siletz; ECHAM_B1; 3 4 5 1 2 Fig. 2. (c) Fig. 1. (A) Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ECHAM_A2; ECHAM_A1b;

46 45 (a) (b)

PCM_B1. (f) ECHAM_A2; (a) by realization: (a) ECHAM_A2; (b) (b) ECHAM_A2; (a) realization: by PCM_A1b; (e) PCM_B1. (f) 2926 2925 PCM_A2; (d) PCM_A1b; (e) ECHAM_B1; (d) PCM_A2; ECHAM_B1; (d) PCM_B1. (e) PCM_A1b; (f) ECHAM_B1; Change in Feddema Moisture Index (unitless) Change in seasonality class by realization: (a) ECHAM_A2; (b) ECHAM_A1b; (c) ECHAM_A1b; (b) ECHAM_A2; by realization: (a) class in seasonality Change

PCM_A2; (c) (d) Figure 4. ECHAM_B1; (d) PCM_A2; (d) PCM_B1. PCM_A1b;ECHAM_B1; (f) (e)

ECHAM_A1b; (c) Figure 3.

1 2 3 4 5 4 5 3 1 2 Change in Feddema Moisture Index (unitless) by realization: Change in seasonality class by realization: ECHAM_A1b; ECHAM_B1; Fig. 4. (c) Fig. 3. (b)

47 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | monthly monthly

48 from initial monthly mod- cent departures. (B) res (B) from initial initial from (B) departures (A) and percent 2070 departures ), by realization. Note: A total of six of the 5,660 assessment units had an units an 5,660 assessment had six the of of total A Note: by realization. ), S′ , in mm) for the ECHAM_A1b , in mm) for ECHAM_A1b the S′

Δ ( 47

, in mm) for the ECHAM_A1b realization. 0 modified surplusmodified ( one departure percent for month, to zeros. These due set undefined were divide by values to zero when calculating the median per 2041- 5. Median Figure

monthly monthly S

∆ 3 4 5 6 1 2 2928 2927 and percent departures (A)

Change modified in surplus monthly cent departures. ), by realization. Note: a total of six of the 5660 assessment units had an unde- 0 S res (B) from initial initial from (B) departures (A) and percent 2070 departures 6. Figure realization. realization. ), by realization. Note: A total of six of the 5,660 assessment units had an units an 5,660 assessment had six the of of total A Note: by realization. ), S′ 1 2 4 5 3 Change in monthly modified surplus ( Median 2041–2070 departures Fig. 6. ified surplus ( fined percent departure forwhen one calculating month, the due median to percent divide departures. by zeros. These values were set to zero Fig. 5. 2041- 5. Median Figure surplusmodified ( one departure percent for month, to zeros. These due set undefined were divide by values to zero when calculating the median per 6 1 2 3 4 5 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2041– 2041– (D) (D) (B) (B) (D) (D) ECHAM_A2 ECHAM_A1b ECHAM_B1 PCM_A2 PCM_A1b PCM_B1 ECHAM_A2 ECHAM_A1b ECHAM_B1 PCM_A2 PCM_A1b PCM_B1 Q S* Q S* , by realization; and , by realization; and ∗ ∗ S S Initial (1971–2000) HL distribution; Initial (1971–2000) HL distribution; Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep (A) (A) 0 0 , in mm) and watershed positive surplus , in mm) and watershed positive surplus 0 0

300 200 100 300 200 100

-100 -100 Q Q 600 500 400 300 600 500 400 300 200 100 200 100

S initial from res u u depart Percent S initial from res u u depart Percent

* *

(mm) S r o o Q (mm) S r o o Q

* * 2930 2929 , by realization (July and August values undefined (C) (C) ∗ , by realization. ∗ S S (A) (A) 2041–2070 departures from initial monthly 2041–2070 departures from initial monthly (C) (C) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Results for the Siletz River basin, Oregon. 0 Results for the Sandy River basin, Oregon. 0

100

100 -100 -200 -100 -200

(mm) S initial om r r f Departures S initial om r r f Departures (mm)

* * comparison of initial mean monthly discharge ( comparison of initial mean monthly discharge ( , in mm); , in mm); ∗ ∗ S S 2070 % departures from initial monthly Fig. 8. (B) ( due to divide by zeros). 2070 % departures from initial monthly (B) Fig. 7. ( Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (D) (B) ECHAM_A2 ECHAM_A1b ECHAM_B1 PCM_A2 PCM_A1b PCM_B1 Q S* , by realization; and ∗ S Initial (1971–2000) HL (A) , in mm) and watershed posi- Q Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 0 , by realization (August and September 0 ∗ 300 200 100

-100 600 500 400 300 200 100

S

S initial from res u u depart Percent

* (mm) S r o o Q * 2931 (C) (A) 2041–2070 departures from initial monthly (C) comparison of initial mean monthly discharge ( , in mm); ∗ S (B) Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep 0 Results for the Middle Fork John Day River basin, Oregon.

100 -100 -200

Departures f Departures (mm) S initial om r r * 2041–2070 % departures from initial monthly values undefined due to divide by zeros). Fig. 9. distribution; (D) tive surplus (