Impact of Climate Change on the Peace River Thermal Ice Regime

Transcription

1 CGU HS Commttee on Rver Ice Processes and the Envronment 13th Workshop on the Hydraulcs o Ice Covered Rvers Hanover, NH, September15-16, 25 Impact o Clmate Change on the Peace Rver Thermal Ice Regme Robyn Andrshak and Faye Hcks Department o Cvl and Envronmental Engneerng Unversty o Alberta, Edmonton, Alberta T6G 2W2 Canada aye.hcks@ualberta.ca In ths nvestgaton, a one-dmensonal hydrodynamc model that ncludes rver ce ormaton and meltng processes s developed and used to conduct a prelmnary assessment o clmate change mpact on the ce regme o the Peace Rver n Alberta. The model employs an Euleran rame o reerence or both the low hydrodynamcs and the ce processes (ce cover ormaton and deteroraton) and uses the characterstc-dsspatve-galerkn nte element method to solve the prmary equatons. Ths paper detals the model ormulaton and ts applcaton to the Peace Rver. Model calbraton and valdaton results wth hstorcal data are presented; these ndcate that the present model adequately smulates water temperature and ce ront proles. However, ts urther development to nclude certan dynamc reeze-up processes s requred to rene the ce ront results. Hgher ar temperatures predcted by the CGCM2 clmate model were used to generate uture ce ront proles that correspond to the hstorcal runs. Ths prelmnary clmate change mpact analyss suggests that there s a sgncant potental or a shorter ce-covered season on the Peace Rver by the md-twentyrst century. At the Town o Peace Rver, the average total reducton n ce cover duraton s 28 days (31%) under the scenaro appled.

2 1. Introducton The wnter ce cover that orms on most northern rvers plays an mportant role n ecosystems and water qualty (Prowse and Culp, 23) and n many cases s a sgncant actor n Canada s northern transportaton network (e.g. Gerard et al., 1992; Kuryk and Domaratzk, 1999). Clmate change, n partcular clmate warmng, has the potental to aect not only the duraton and extent o ce cover on northern rvers but also the requency and/or severty o ce jam events (Beltaos and Prowse, 21). Clearly, t s mportant to be able to assess the potental mpact o clmate change and clmate varablty on the ce regme o rvers and to develop adaptve strateges to mnmze the negatve mpacts o these changes. It has been determned that clmate warmng has already occurred n northern Canada; n act, to a greater extent there than the global average (Fgure 1). As partcpants n the Global Energy and Water Cycle Experment (GEWEX), Canadan researchers are nvestgatng the potental eects o clmate change on the hydrology o the Mackenze Rver Basn n collaboraton wth Envronment Canada scentsts. Ther collectve work s known as the Mackenze GEWEX Study (MAGS). Ths project, whch ocuses on assessng the mpact o clmate change on the thermal ce regme o rvers, s one component o the MAGS study, and was also conducted n collaboraton wth Alberta Envronment s Clmate Change Research Group. The partcular rver o nterest or ths nvestgaton s the Peace Rver, located n the upper Mackenze Rver basn. In ths prelmnary nvestgaton, we explore the potental mpacts o clmate warmng on the thermal regme o the Peace Rver or the reach extendng rom Hudson Hope, BC, to Fort Vermllon, AB, as shown n Fgure 2. Ths rver s regulated by hydropower dams at ts upstream end, and as a result thermal ce processes are a domnant eature o ts wnter regme. Buldng on the valdated dynamc hydraulc model o the Peace Rver developed by Hcks (1996) and also appled by Peters and Prowse (21), we employ a ully Euleran ramework to ncorporate thermal ce ormaton and deteroraton processes. The model s valdated wth hstorcal data and then appled to provde a prelmnary evaluaton o the potental magntude and sgncance o clmate change mpacts on thermal ce processes. Ths paper outlnes the development, calbraton, and applcaton o the thermal rver ce model; the prelmnary calbraton and valdaton results or the Peace Rver study reach; and nally applcaton o the model to a clmate warmng scenaro or the Peace Rver. 2. Model Development The model developed or ths study s bult upon the Unversty o Alberta s publc doman, dynamc rver routng model, Rver1D (Hcks and Steler, 1992). Rver1D s a one-dmensonal nte element-based numercal model that solves conservaton o water mass and longtudnal momentum usng the characterstc-dsspatve-galerkn (CDG) scheme. For ths nvestgaton, the rectangular channel verson o the Rver1D model has been enhanced to ncorporate thermal ce related processes ncludng consderaton o water temperature, suspended razl ce, surace ce concentraton, surace razl ce, and sold surace ce. Ice ront locaton s a supplementary soluton varable that determnes where the ree-drt assumpton s appled to surace ce and where surace ce velocty s zero.

3 Exstng rver ce models (e.g. Shen et al., 1995; Lal and Shen, 1989) use an Euleran-Lagrangan approach to model the governng equatons. In contrast, the thermal process equatons modeled n Rver1D have been developed rom control volume prncples n a completely Euleran rame o reerence. Each equaton can be wrtten n the orm: t x ( Φ) + ( UΦ) = ΣF [1] where Φ represents the soluton varable, U the mean or surace ce low velocty, and ΣF the sum o the mass or energy luxes applyng to the control volume. The equatons n ths general orm were subsequently developed nto weak statement ormulatons based on the characterstcdsspatve-galerkn nte element scheme, and then ncorporated nto Rver1D. For each tme step n the transent soluton, the modelng procedure nvolves a decoupled soluton o the total (ce + water) mass and longtudnal momentum conservaton equatons, ollowed by soluton o the water temperature and ce mass conservaton equatons. Ths approach assumes that the drtng ce moves at the surace water velocty, wth ce resstance eects only consdered once the ce tsel s arrested. Ths prelmnary verson o the model does not nclude consderaton o dynamc ce jam ormaton or release processes. Conservaton o thermal energy s used to derve the model or rver water temperature: t ( AC T ) + ( UAC T ) p w x p w = ( B B ) φ wa Bφa Bφw φa > φw > [2] The rst lux term on the rght hand sde o the equaton represents the energy transer between the water and the ar above any open water area. The second lux term accounts or the loss o heat over the ce-covered area. Ths term only apples heat s beng lost, as any heat gan over an ce-covered area s drected towards ce melt. Smlarly wth the nal term, representng heat transer assocated wth sold ce melt, there must be a postve heat transer rom the water to the ce cover or ths term to take eect. Lnearzed water-ar and ce-ar heat exchanges are calculated usng the method descrbed by Lal and Shen (1989). The ce-water heat exchange s computed based on the work o Ashton (1973). Once a zero degree sotherm has developed wthn the smulated reach, the ce mass conservaton component o the model s actvated. The ntal ce mass process beng modeled s the generaton o suspended razl accordng to: A t UA + x 1 ( B B ) φwa = ηc B L razl rse razl ormaton C Tw = [3]

4 Note that the lux term assocated wth razl ormaton requres the water temperature be zero degrees at that locaton. The other lux term quantes the ce mass lost rom suspenson to the surace, due to razl buoyancy. The rse parameter, η, s a calbraton parameter that controls the rate o surace ce ormaton. As razl ce rses, the surace ce coverage ncreases at a rate also nluenced by an ntal razl loe thckness, t, speced by the modeler. The change n surace ce coverage, B, s gven by: ( ) + = + and pore water deposton razl 1 1 C B C e e t x B U t B η [4] At the surace, the razl deposts n proporton to the porosty o razl loes, e. The capture o pore water mass wthn the loe area s also ncluded n the above equaton. The thckness o razl slush on the undersde o pans and sold ce at the surace s derved rom the ollowng two equatons when razl slush exsts: ( ) + = + > > slush melt pore water reezng and pore water deposton razl w a 1 1 φ φ φ φ η w a C L B L B B C e e x A U t A [5] + = + < > sold ce melt pore water reezng 1 a a a a L B L B x A U t A φ φ φ φ [6] When the soluton or razl slush thckness goes to zero, the lux assocated wth pore water reezng no longer apples to the sold ce equaton, whle new terms or growth o columnar ce and sold ce melt due to warm water enter the equaton.

5 In ths case, the sold ce equaton becomes: A t U A + x 1 = Bφa L growth o columnar ce φa > T = w Bφa + L sold ce melt φ < a Bφw L sold ce melt to warm water φ > w [7] In the present verson o the model, the user must specy the tme at whch brdgng occurs at the downstream boundary. When ths tme n the smulaton s reached, the ntal condton or the ce ront locaton s set at the downstream boundary and the approach o ce rom upstream leads to the upstream progresson o the ce ront. A straghtorward conservaton o surace ce method, nspred by that employed n the RICEN model (Shen et al., 1995), s used to ollow the ce ront locaton: C U X ( t + t) = X ( t) t [8] P jux The juxtaposton parameter, P jux, s a calbraton parameter that aects the smulated rate o ce cover advance. Its value s ntended to account or the reducton o ce velocty as pans arrve at the leadng edge o the ce cover as well as any assocated crushng, under-turnng, or consoldaton o loes. Recesson o the ce cover due to melt s handled more naturally by the model. The ce ront locaton moves node by node upstream as the ce thckness at the ce ront decreases towards zero. Intermedate ce ront locatons are not calculated durng the melt process, as they are durng upstream progresson. 3. Model Calbraton and Applcaton to the Peace Rver, Canada 3.1 Data Requrements The data requred to run the Rver1D thermal rver ce model conssts o ntal condtons and nlow tme seres or the hydraulc, water temperature, and ce condtons. A downstream ratng curve or water level tme seres s also requred or the hydraulc modelng component. Fnally, one or more ar temperature tme seres must be speced to drve the thermal modelng components. Heat nput rom solar radaton can also be consdered, but ths eature was not employed n ths prelmnary applcaton, as nsucent data were avalable. Downstream boundary condtons or water temperature and ce condtons are not requred as the nte element method employed n Rver1D uses the applcable natural boundary condtons. Dscharge records and water temperature or the Bennett/Peace Canyon Dam were made avalable by Alberta Envronment and used to develop the upstream boundary condtons or the model. Ice nlow at the upstream boundary was set at zero or all smulatons, whch s

6 consstent wth the physcal stuaton n ths case. Extensve ar temperature records at Fort St. John, BC, the Town o Peace Rver, AB, and at Hgh Level, AB, were used to construct the ar temperature tme seres or the smulatons (staton locatons noted n Fgure 2). For ths study, the average mean daly ar temperature at the rst two statons was used to dene the ar temperature upstream o the Town o Peace Rver and the mean daly ar temperature at Hgh Level was appled to the lower reach. The remanng nput parameter s the tme o ce ront ntaton at the downstream boundary. Ths value was ether estmated or (when known) taken drectly rom hstorcal ce ront observatons provded by Alberta Envronment. 3.2 Model Calbraton and Valdaton Calbraton and valdaton o the thermal rver ce model nvolved two phases: the rst requred calbraton/valdaton o the ar-water heat exchange coecent to observed water temperature data; the second phase nvolved calbratng and valdatng the remanng set o parameters that dctate the smulated ce ront prole. Calbraton / Valdaton Usng Observed Water Temperature Data Water temperature observatons on the Peace Rver n Alberta are currently lmted to two locatons: the Water Survey o Canada (WSC) gauges at Alces Rver (164 km downstream o the Bennett Dam) and the Town o Peace Rver (396 km downstream o the Bennett Dam). As only two years o record were avalable, or the 22/3 and 23/4 ce seasons, the ormer season was used or calbraton and the latter or valdaton. For the calbraton usng the 22/3 data, heat exchange coecents o 15 and 2 W/m 2 were tested (chosen based on the results o prevous studes on the Peace Rver (e.g. Andres, 1993)). The resultng smulated water temperature proles at the Alces and Peace Rver gauge stes are shown n Fgures 3 and 4, respectvely. As the gures llustrate, both values o the heat exchange coecent tested appear to produce modeled water temperatures at Alces that are consstently hgher than the observed values. For the Peace Rver gauge ste, the model appears to produce results comparable to the measured data. However, the smulated water temperatures show hgher peaks and there s no clear ndcaton that one or the other o the heat exchange coecents tested provdes a superor match to the observed data. In the end, or ths prelmnary nvestgaton, t was decded to proceed usng a value o 15 W/m 2 or the heat exchange coecent, as t provded the better representaton o the date the zero degree sotherm reached the Town o Peace Rver. Fgures 5 and 6 compare the smulated water temperature prole (usng 15 W/m 2 or the heat exchange coecent) wth the observed data at the two gauge stes or the 23/4 (valdaton) season. As the gures llustrate, model results are generally consstent wth the measured data, but agan n the case o the Alces ste, the model ndcates hgher water temperatures than those measured. Smlar to the calbraton runs or the Peace Rver gauge, the model results or the valdaton season tend to show hgher peak values than those seen n the data. Overall, the results o ths prelmnary calbraton and valdaton to the water temperature data suggest that the model s producng reasonable results, though not perectly capturng the water

7 temperature behavor. A choce o 15 W/m 2 seems a reasonable compromse gven the lmted avalable data or calbraton and valdaton. Clearly more data and addtonal modelng s requred to rene the smulaton results or the Alces gauge ste n partcular. The current overpredcton at Alces may smply relect a queston o the sutablty o the ar temperature data or that locaton or the qualty o the water temperature data at that ste or at the upstream boundary. In any case, the water temperatures were consdered to be adequately modeled or the purposes o ths prelmnary nvestgaton. Calbraton / Valdaton o the Ice Process Parameter Set More than 2 years o hstorcal records, ncludng documentaton o the ce ront progresson n each year, were suppled by Alberta Envronment or calbraton and valdaton o the ce process model components. Unortunately, much o the record s sparse, most notably n terms o the water temperature normaton requred or the nlow boundary condton. In the end, t was decded that, or ths prelmnary nvestgaton, most o the emprcal ce process parameters would be set to typcal values and only the juxtaposton parameter, P, would be adjusted. A value o P jux = 2.5 was ound to produce the best overall ce ront results or the 2 years o hstorcal record smulated. The remanng parameters and ther adopted values were: razl loe porosty =.5; razl rse parameter =.1 m/s; Mannng s n or ce cover =.2; and ce-water heat exchange coecent = 1187 W s.8 /m 2.6 / C (Ashton, 1973). Other varables can also be used to calbrate the model parameters and to assess the qualty o ts perormance: measured water levels, documented surace ce concentratons, and observed ce thcknesses. However, gven the objectve o ths study, whch was to nvestgate clmate warmng nluences on the extent and duraton o ce cover, ce ront locaton was consdered the most relevant. Thus, valdaton conssted o comparng the modeled ce ront locatons to the observed data. In comparng model results to measured ce ront progresson, t was ound that the perormance o the model vared rom year to year. For example, the smulated prole or the years 22/3 and 23/4 extended consderably arther upstream than the observed prole n the reach upstream o the Town o Peace Rver (TPR) and Dunvegan (DUN) as shown n Fgures 7 and 8. However, n other years, such as 1995/96 and 1996/97, the model perormed extremely well, as shown n Fgures 9 and 1. In addton to the necessary approxmatons regardng the nlow boundary water temperatures or those years where the data was suspect or mssng, a key actor contrbutng to ths apparently nconsstent model perormance s the act that, at present, the Rver1D thermal ce model does not consder ce cover consoldaton or hydraulc thckenng. These processes are known to occur on occason along the Peace Rver, partcularly durng the reeze-up perod, and thereore t s not unexpected that the current verson o the model would over-estmate the upstream progresson o the ce cover n such cases. jux

8 Despte these lmtatons n the model s capabltes, t stll produces sucently reasonable results to be useul n conductng a prelmnary assessment o the potental nluences o clmate change on the thermal ce regme o the o Peace Rver. For example, based on the 2 years o hstorcal record smulated, Rver1D predcted the average duraton o ce cover and dates o reeze-up and break-up at the Town o Peace Rver to wthn two days o the observed. The maxmum extent o ce smulated was, on average, 5 km arther upstream than the observed value. 4. Clmate Change Analyss The Canadan CGCM2 clmate model was selected to assess the mpact o clmate change on the hstorcal wnter seasons modeled. Two standardzed uture clmate scenaros were avalable rom the Mackenze GEWEX Study (MAGS) research network database; these are commonly reerred to as A2 and B2. The A2 scenaro, whch s based on larger populaton growth and hgher cumulatve CO 2 emssons over the perod 199 to 21 than the B2 scenaro, was chosen or ths study, n order to examne the more severe clmate predcton. The CGCM2 model provdes mean monthly temperature change projectons relatve to the perod 1961 to 199 or varous locatons n Canada. For ths prelmnary analyss, the md-range projecton or the year 25 was selected over the two extremes o 21 and 28. To assess the potental eects o clmate change on the wnter regme o the Peace Rver, t was necessary to assume that the mean monthly ar temperature change projectons rom the clmate change scenaro could be appled drectly to the mean daly hstorcal values used as model nput. Other compoundng potental eects o clmate warmng, such warmer water temperatures n the hydropower dam reservor and/or a delay n the tmng o ntal ce cover brdgng at Fort Vermlon, could not be consdered here but do warrant uture nvestgaton. Intutve judgment suggests that neglectng these actors would mean that the results o ths analyss would lkely underestmate the potental mpact o warmng on the duraton and extent o the rver s ce cover. Examples o clmate change ce ront proles compared wth the hstorcal smulatons are presented n Fgures 11 through 14, or the same example years presented n the prevous secton. The predcted November, December, January, February, March, and Aprl temperature ncreases or the southern regon (ncludng the Town o Peace Rver) o.37, 4.2, 5.11, 3.85, 4.1, and 1.85 C, and.3, 3.82, 5.67, 3.9, 4.5, and 1.7 C or the northern regon, clearly have a sgncant mpact on the overall ce ront progresson. In partcular, the duraton and maxmum extent o ce cover are reduced. As Fgure 15 llustrates, the maxmum upstream extent o the ce cover would be expected to be consstently urther downstream o the dam, by an average o 6 km. Fgure 16 presents more ste specc results, at the Town o Peace Rver, where re-analyss o 2 years o hstorcal ce smulatons reduced the duraton o ce cover there by an average o 28 days or 31% compared to the hstorcal observatons rom the same tme perod. 5. Conclusons The purpose o ths nvestgaton was to apply the Rver1D thermal ce model to the Peace Rver and to assess the potental mpacts o clmate change on the rver s thermal ce regme. In

9 general, t was ound that the model produced reasonable predctons o ce cover progresson or the valdaton perod, when takng nto account the lmted avalablty o some nput data (partcularly nlow water temperature data). However, because the model s currently capable o modelng thermal ce processes only, t cannot precsely capture ce cover progresson n years where dynamc processes, such as secondary ce cover consoldaton, sgncantly nluence the locaton o the ce ront. Nevertheless, the model s capablty s consdered adequate or the purposes o ths prelmnary study. To explore the potental mpacts o clmate change on the Peace Rver thermal ce regme, the valdated model was then appled or the same hstorcal perod, usng the ar temperature changes ndcated or Fort St. John, the Town o Peace Rver, and Hgh Level under the A2 clmate change projecton or the year 25, generated by the CGCM2 model. An mportant consderaton aectng the nterpretaton o these results s that ncreased ar temperatures would also potentally have an mpact on the upstream water temperature boundary condton (.e. by ncreasng the reservor water temperatures) and would lkely delay the tme o rst ce ormaton at the downstream boundary. Both these eects would tend to delay the development o the ce cover, and lead to earler thermal melt. Thus, n ths context, the results ndcated here are lkely conservatve n terms o the degree o clmate change mpact on the rver s ce regme that mght occur under the CGCM2/A2 scenaro. Results o ths prelmnary clmate change mpact assessment suggest that there s a sgncant potental or a shorter ce-covered season under the clmate change scenaro nvestgated. In terms o the delay n the date o reeze-up at the Town o Peace Rver, an average o 13 days s ndcated and or break-up, the average date s 15 days earler. These results amount to a 28-day reducton n duraton o ce cover at the Town o Peace Rver. The smulated mnmum ce ront dstance downstream o the Bennett Dam was an average o 6 klometres greater ater clmate change was appled, as compared to the hstorcal model results. Gven the lmted nput and valdaton data, the act that the model only consders thermal ce processes at ths tme, the lack o consderaton o the eects o clmate change on reservor outlow temperatures and ce cover ntaton date, and uncertantes assocated wth the meteorologcal clmate change analyss tsel (as well as ts applcablty or ths partcular perod o record), these quanttatve averages cannot be consdered rm predctons. However, ther magntudes do dentely suggest that there wll be a measurable, and possbly even sgncant, mpact attrbutable to clmate change on the uture ce regme o the Peace Rver. Thereore, t s mportant to start developng adaptve strateges as well as mproved models and data archves, n order to gan a more relable quanttatve assessment o these mpacts. 6. Recommendatons or Future Research Numerous opportuntes exst to mprove the current Rver1D thermal model. The most mmedate need s to ncorporate the physcs o ce cover stablty and mechancal thckenng nto the current verson. Ths should greatly mprove the model s consstency when smulatng the ce ront prole rom year-to-year. Secondarly, computaton o ce loe velocty can be advanced to nclude the eect o channel constrcton on the passage o large concentratons o

10 surace ce. Fnally, consderaton o natural channel geometry would acltate valdaton o water levels, not just ce ront progresson. The brdgng phenomenon s stll not completely understood and remans largely ste specc. It would be extremely benecal, partcularly wth respect to modelng clmate change eects on rver ce, to have a relable brdgng crteron bult-nto the model. Future research, modelng, and eld observaton could reveal a great deal about ths aspect o the rver s ce regme. Other ssues not currently ncluded n the model such as lateral thermal nlow and snow cover could also be the ocus o uture work. Contnued and mproved data collecton s also crtcal to the qualty and success o ths and other rver ce studes. For the Peace Rver, one or more addtonal water temperature montorng stes downstream o the Town o Peace Rver would provde extremely useul calbraton and valdaton data. The hydropower dam s dscharge temperature should contnue to be measured and reservor models should be developed to assess the mpact o clmate change on the seasonal water temperature boundary condton. Fnally, addtonal clmate change scenaros can be nvestgated wth the current model and the mportance o the nlow water temperature and date o brdgng on the overall ce ront smulaton can be determned. Lst o Symbols A lqud water low area (m 2 ) A suspended razl ce low area (m 2 ) A sold ce low area (m 2 ) A low area o razl slush at the surace (m 2 ) B top wdth o channel (m) B surace ce wdth or coverage (m) C suspended razl ce concentraton (dmensonless) C surace ce concentraton (dmensonless) C p specc heat o water (J/kg/ C) e porosty o razl slush (dmensonless) L latent heat o ce (J/kg) P jux juxtaposton parameter (dmensonless) t tme (s) t ntal razl ce thckness (m) T w water temperature ( C) U mean water velocty (m/s) U surace ce velocty (m/s) x longtudnal dstance along channel centrelne (m) X locaton o ce ront / dstance rom upstream boundary (m) t soluton tme step (s)

11 η razl rse parameter (m/s) densty o water (kg/m 3 ) combned densty o razl slush and pore water (kg/m 3 ) densty o ce (kg/m 3 ) φ a net rate o heat exchange per unt area between ce and ar (W/m 2 ) φ w net rate o heat loss per unt area between ce and water (W/m 2 ) φ net rate o heat loss per unt area between water and ar (W/m 2 ) wa Acknowledgments Fundng or ths study was provded by the Clmate Change Research User s Group (CCRUG) at Alberta Envronment as well as by the Natural Scences and Engneerng Research Councl o Canada (NSERC) through the MAGS (Mackenze GEWEX Study) Research Network. Ths support s grateully acknowledged. The authors would also lke to thank Km Westcott and Chandra Mahabr o Alberta Envronment, or ther support o ths project. We truly apprecate ther nterest and assstance n ths research. Thanks are also extended to Martn Jasek o BC Hydro or provdng hstorcal data or the study, and to BC Hydro/Glacer Power/Alberta Envronment or ther jont montorng program on the Peace Rver whch provded the detaled data or 22/3 and 23/4. We also thank the MAGS research group or supplyng the clmate change GCM model results used n ths study. Reerences Andres, D.D. (1993). Eects o Clmate Change on the Freeze-up Regme o the Peace Rver: Phase I Ice Producton Algorthm Development and Calbraton. Report No. SWE 93/1, Envronmental Research & Engneerng Department, Alberta Research Councl, Edmonton, Alberta, 52 pp. Ashton, G. D. (1973). Heat Transer to Rver Ice covers. Proc. 3 th Eastern Snow Conerence, Amherst, Massachusetts, Ashton, G.D. (1986). Rver and Lake Ice Engneerng. Water Resources Publcatons, Lttleton, Colorado, 485 pp. Bletaos, S. and Prowse, T.D. (21). Clmate Impacts on Extreme Ice-jam Events n Canadan Rvers. Journal o Hydrologc Scences, Vol. 46, No. 1, Gerard, R., Hcks, F.E., MacAlpne, T., and Chen X. (1992). Severe Wnter Ferry Operaton: The Mackenze Rver at Ft. Provdence, NWT. Proc. o the 11 th Internatonal Assoc. or Hydraulc Research Ice Symposum, Ban, Alberta, June 1992, Hcks, F.E. and Steler, P.M. (1992). A Characterstc-Dsspatve-Galerkn Scheme or Open Channel Flow. ASCE Journal o Hydraulc Eng., Vol. 118, No. 2, Hcks, F.E. (1996). Hydraulc Flood Routng wth Mnmal Channel Data: Peace Rver, Canada.. Canadan Journal o Cvl Eng., Vol. 23, No. 2,

12 Kuryk, D. and Domaratzk, M. (1999). Constructon and Mantenance o Wnter Roads n Mantoba. Proc. o the 1 th Workshop on the Hydraulcs o Ice-covered Rvers, Wnnpeg, Lal, A.M.W., and Shen, H.T. (1989). A Mathematcal Model or Rver Ice Processes (RICE). Report No. 89-4, Department o Cvl and Envronmental Engneerng, Clarkson Unversty, Potsdam, New York, 164 pp. Peters, D.L. and Prowse, T.D. (21). Regulaton Eects on the Lower Peace Rver, Canada. Journal o Hydrologc Processes, Vol. 15, Prowse, T.D. and Culp, J.M. (23). Ice Breakup: A Neglected Factor n Rver Ecology, Canadan Journal o Cvl Eng., Vol. 3, Shen, H.T., Wang, S., and Lal, A.M.W. (1995). Numercal Smulaton o Rver Ice Processes. Journal Cold Regons Eng., Vol. 9, No. 3,

13 Study area Fgure 1. Wnter temperature trends, (Adapted rom: Clmate Research Unt, Unversty o East Angla, U.K., Locaton o ar temperature statons Upstream boundary Downstream boundary Fgure 2. Peace Rver basn, showng study reach rom Hudson Hope to Fort Vermllon. (Adapted rom: Hcks, 1996)

14 1 9 8 Smulated: Smulated: Observed h wa = 2 W/m 2 h wa = 15 W/m Nov-1 Nov-8 Nov-15 Nov-22 Nov-29 Dec-6 Dec-13 Dec-2 Dec-27 Jan-3 Jan-1 Jan-17 Jan-24 Jan-31 Water Temperature ( C) Fgure 3. Peace Rver water temperature calbraton to the Alces gauge (22/3) Smulated: Smulated: Observed h wa = 2 W/m 2 h wa = 15 W/m 2 Water Temperature ( C) Nov-1 Nov-8 Nov-15 Nov-22 Nov-29 Dec-6 Dec-13 Dec-2 Dec-27 Jan-3 Jan-1 Jan-17 Jan-24 Jan-31 Fgure 4. Peace Rver water temperature calbraton to the Town o Peace Rver gauge (22/3).

15 1 9 8 Smulated: Observed h wa = 15 W/m Nov-1 Nov-8 Nov-15 Nov-22 Nov-29 Dec-6 Dec-13 Dec-2 Dec-27 Jan-3 Jan-1 Jan-17 Water Temperature ( C) Jan-24 Jan-31 Fgure 5. Water temperature model valdaton at the Alces gauge (23/4) Smulated: Observed h wa = 15 W/m 2 Water Temperature ( C) Nov-1 Nov-8 Nov-15 Nov-22 Nov-29 Dec-6 Dec-13 Dec-2 Dec-27 Jan-3 Jan-1 Jan-17 Jan-24 Jan-31 Fgure 6. Water temperature model valdaton at the Town o Peace Rver gauge (23/4).

16 Dstance Downstream o Bennett Dam (km) TPR DUN Smulated Ice Front Ice Front Observatons Nov-1 Nov-15 Nov-29 Dec-13 Dec-27 Jan-1 Jan-24 Feb-7 Feb-21 Mar-7 Mar-21 Apr-4 Apr-18 May-2 Fgure 7. Modeled and observed ce ront prole (22/3). Dstance Downstream o Bennett Dam (km) TPR DUN Nov-1 Nov-15 Nov-29 Dec-13 Dec-27 Jan-1 Jan-24 Feb-7 Feb-21 Mar-6 Mar-2 Apr-3 Apr-17 May-1 Smulated Ice Front Ice Front Observatons Fgure 8. Modeled and observed ce ront prole (23/4).

17 Dstance Downstream o Bennett Dam (km) TPR DUN Smulated Ice Front Ice Front Observatons Oct-15 Oct-29 Nov-12 Nov-26 Dec-1 Dec-24 Jan-7 Jan-21 Feb-4 Feb-18 Mar-3 Mar-17 Mar-31 Apr-14 Apr-28 Fgure 9. Modeled and observed ce ront prole (1995/96). Dstance Downstream o Bennett Dam (km) TPR DUN Oct-15 Oct-29 Nov-12 Nov-26 Dec-1 Dec-24 Jan-7 Jan-21 Feb-4 Feb-18 Mar-4 Mar-18 Apr-1 Apr-15 Apr-29 Smulated Ice Front Ice Front Observatons Fgure 1. Modeled and observed ce ront prole (1996/97).

18 Dstance Downstream o Bennett Dam (km) TPR DUN Smulated Ice Front Future Clmate Ice Front Nov-1 Nov-15 Nov-29 Dec-13 Dec-27 Jan-1 Jan-24 Feb-7 Feb-21 Mar-7 Mar-21 Apr-4 Apr-18 May-2 Fgure 11. Smulated hstorcal and uture clmate ce ront proles (22/3). Dstance Downstream o Bennett Dam (km) TPR DUN Nov-1 Nov-15 Nov-29 Dec-13 Dec-27 Jan-1 Jan-24 Feb-7 Feb-21 Mar-6 Mar-2 Apr-3 Apr-17 May-1 Smulated Ice Front Future Clmate Ice Front Fgure 12. Smulated hstorcal and uture clmate ce ront proles (23/4).

19 Dstance Downstream o Bennett Dam (km) TPR DUN Smulated Ice Front Future Clmate Ice Front Oct-15 Oct-29 Nov-12 Nov-26 Dec-1 Dec-24 Jan-7 Jan-21 Feb-4 Feb-18 Mar-3 Mar-17 Mar-31 Apr-14 Apr-28 Fgure 13. Smulated hstorcal and uture clmate ce ront proles (1995/96). Dstance Downstream o Bennett Dam (km) TPR DUN Oct-15 Oct-29 Nov-12 Nov-26 Dec-1 Dec-24 Jan-7 Jan-21 Feb-4 Feb-18 Mar-4 Mar-18 Apr-1 Apr-15 Apr-29 Smulated Ice Front Future Clmate Ice Front Fgure 14. Smulated hstorcal and uture clmate ce ront proles (1996/97).

20 Modeled Future Clmate Modeled Hstorcal Fgure 15. Modeled hstorcal versus uture clmate change mnmum ce ront dstance (n klometres) rom the Bennett Dam n Brtsh Columba Modeled Future Clmate Modeled Hstorcal Fgure 16. Modeled hstorcal versus uture clmate change duraton o ce cover (n days) at the Town o Peace Rver n Alberta.