HYDROLOGIC CYCLE AND HEAT TRANSPORT MODELING AND ITS APPLICATION TO THE KANDA RIVER WATERSHED, TOKYO. Tsuyoshi Kinouchi. and.

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1 HYDROLOGIC CYCLE AND HEAT TRANSPORT MODELING AND ITS APPLICATION TO THE KANDA RIVER WATERSHED, TOKYO By Tuyoh Knouch Department of Envronment Sytem Management, Fukuhma Unverty, Fukuhma-Sh, Fukuhma, apan and Yangen a Department of Water Reource, Inttute of Water Reource and Hydropoer Reearch, Bejng, Chna SYNOPSIS A phycally baed dtrbuted hydrologcal model (WEP model) a coupled th a nely developed model of heat tranport n rver ater to mulate aterhed-cale hydrologcal and heat tranport procee and the reultng effect on the tream envronment. The model capable of mulatng runoff from a hghly urbanzed aterhed th a dranage ytem of rver channel and a eer netork, hch enable approprate predcton of rver flood and nflo to ateater treatment plant. Such a model degned to nvetgate factor affectng patal and temporal varaton of the tream temperature by ncorporatng anthropogenc heat mpact and urban canopy procee. By applyng the model to the Kanda Rver Waterhed n Tokyo, apan, tream flo and temperature a ell a nflo to a WWTP ere mulated ell. The anthropogenc heat mpact on tream temperature a found to be very gnfcant n nter. INTRODUCTION Stream are thought to have mportant natural functon uch a natural landcapng, conervng habtat, and controllng the mcro-clmate n urban envronment. Such functon can be effectve hen approprate tream temperature and other qualty level are mantaned. Hoever, urban tream are vulnerable to thermal polluton due to varou drect and ndrect anthropogenc mpact uch a the effluent from ateater treatment plant, detructon of rparan vegetaton, rver channelzaton, the runoff from paved urface and global armng. Increaed tream temperature can decreae the envronmental mportance of urban tream and varou ecologcal mpact have been oberved uch a the ncreae n nvave pece. Becaue of ncreang urban ater and energy ate due to populaton groth and hgh energy conumpton lfe-tyle, the temperature and magntude of urban ateater ha ncreaed gnfcantly (Knouch, 1), hch may have reulted n the long-term ncreae n tream temperature. Knouch et al. (2)

2 ndcated that the tream temperature n nter and early prng n the central Tokyo ncreaed at a rate of C/year n rver egment that had a conderable ncreae n ateater heat nput. To conerve envronmental value of urban tream, a frameork need to be provded for predctng tream temperature under varou natural and anthropogenc controllng factor. Although there are many phycally baed n-tream model that are capable of mulatng the hadng effect (Snokrot and Stefan, 3), the mpact of urbanzaton (LeBlanc et al., 4) and global armng (Tung et al., 5), fe tude have modelled and valdated tream temperature varaton conderng hydrologcal procee n a aterhed cale (Chen et al., 6; Haag and Luce, 7). Hoever, the predctve frameork of urban tream temperature need to nclude hydrologcal modelng a the tream temperature very dependent on the hydrologcal behavor of aterhed a ell a on the rparan condton and anthropogenc heatng/coolng factor. In addton, charactertc radaton envronment n channel run through hghly urbanzed area requre pecal modelng of ar-ater heat fluxe. For th purpoe, a phycally baed dtrbuted hydrologcal model developed by a et al. (8~1) a coupled th a nely developed model of heat tranport n rver ater, and the performance of the model a demontrated by applyng t to a hghly urbanzed aterhed n Tokyo, apan, here anthropogenc mpact are gnfcant n modfyng natural hydrologc cycle and the ater temperature. MODEL Modelng hydrologcal ytem th dual dranage netork The mulaton of hydrologcal procee n an urbanzed aterhed th dual dranage ytem baed on the WEP model, a phycally baed dtrbuted hydrologcal model developed by a et al. (8~1). The man feature of th model nclude couplng mulaton of hydrologcal procee and energy tranfer procee, mulaton of nteractve mpact of urface ater and groundater, and the moac tructure thn a grd cell. The mulated hydrologcal procee nclude evapotranpraton, nfltraton, urface runoff, uburface runoff, groundater flo, overland flo, and rver flo. The mulated energy tranfer procee nclude hort-ave radaton, long-ave radaton, latent heat flux, enble heat flux, and ol heat flux. In urbanzed aterhed equpped th eer netork, torm runoff flo don through gutter, lateral ppe and eer ppe durng perod of ranfall. In a combned eer ytem, the tormater mxed th ate from houe and buldng eventually flo nto a ateater treatment plant (WWTP). Untreated ateater n the eer ytem overflo to a rver ytem through combned eer overflo (CSO) outlet follong heavy ranfall. In no-ranfall perod, the ate ater from houe and buldng flo nto the WWTP and the treated ateater dcharged nto tream. To take thee charactertc of dual dranage netork nto account n the WEP model, flo n eer ppe are routed a an overland flo n underground pace, ntead of drectly olvng unteady flo n a eer netork, to reduce modelng complexty. Overland flo routng carred out by mean of the knematc ave method th equvalent roughne parameter deduced from land ue data, hle a ngle value gven for the flo routng n a eer netork. The magntude of CSO depend on the tructure and dmenon of the CSO outlet and the ater level thn the CSO outlet. A th model doe not predct ater level n the CSO outlet, e alternatvely modeled flo at the CSO outlet by ettng the maxmum capacty of tormater nflo to the WWTP a follo: Q j of j n j lm j lm lm j / = Q Q, Q = V CA CA (1)

3 here Q j of = the overflo to the rver from the CSO outlet j, Q j n = the nflo to a computatonal meh here the CSO outlet j located, Q j lm = the outflo to a dontream computatonal meh from the meh here the CSO outlet j located, V lm = the maxmum nflo capacty at the WWTP, CA = uptream catchment area of the WWTP, CA j = the catchment area at CSO outlet j. V lm gven by V lm = βv TP, here V TP the treatment capacty of the WWTP, β a contant. In practce, common eer degn allo nflo three tme larger than the degned magntude, hch mean β = 3. Hoever, β could be dfferent from the degn ettng n realty, thu β a calbraton factor n th tudy. Seerage from houe and buldng durng perod thout ranfall routed to compute nflo to the WWTP. The flo routng n a eer netork conder the eepage of groundater and ol moture nto eer ppe. The ol moture eepage modeled o that t proportonal to the unaturated conductvty n the ground, and the eepage of the groundater depend on the level dfference of groundater table and the ater level n a ppe. Modelng heat tranport n tream A bac equaton for heat tranport n an open channel rtten a ( AT) ( QT) 1 T Wh h + = ( AD ) (2) A t A x A x x ρ c V ρ c H ρ c H p p p here T = the ater temperature [ C]; A = the cro-ectonal area [m 2 ]; Q = the flo rate [m 3 /]; D = the longtudnal dperon coeffcent; W h = the net heat load from urface flo, uburface flo, groundater flo, treated ateater and combned eer overflo [/]; h = the ar-ater heat flux [W/m 2 ]; = the heat flux from the tream bed to the tream ater [W/m 2 ]; V = the ater volume of tream element [m 3 ]; H = the ater depth [m]; ρ = the denty of ater [kg/m 3 ]; c p = the pecfc heat of ater [/kg/ C]; x = the flo drecton [m]; t = the tme []. The net heat load W h from ource computed a W ( Q p Tp + Q h = ρ c p np Tnp ) (3) here Q p and T p are the magntude and temperature of pont ource (ateater effluent from WWTP and CSO), repectvely; Q np and T np repreent the magntude and temperature of non-pont ource (urface flo, uburface flo and groundater flo), repectvely. Thermal runoff may caue a re of tream temperature to a lethal level durng ranfall perod n hot eaon (Herb et al, 11). Hoever, nce e manly focu on tream temperature varaton durng the lo flo perod, the temperature of the urface runoff aumed to be the ame a the ar temperature. The oberved volume and temperature of the ateater effluent ere ued, though t can be computed from Knouch (1). The temperature of uburface and groundater flo aumed to be the ame a the ground temperature at a pecfed depth. The ground temperature T gd (z, t) at depth z computed from equaton (4) (Carla and aeger, 12) th the ground urface temperature gven by equaton (5). T gd ( z, t) = A ( z n 2a ) n( nωt z nω a + ε ) 6 + An exp 2 = n 1 ω (4) n

4 T gd 6 = n 1 [ a co( n t) + b ( nωt) ] (, t) = a + n ω n n (5) n 2 n 2 n A = a + b (6) here n(ε n ) = a n /A n ; A = a ; ω = 2π /τ; τ = the perod; a = the thermal dffuvty; a n and b n are the Fourer coeffcent. The ar-ater heat flux h computed a h = RN c e = I + c e (7) here RN = the net radaton at the ater urface; c = the enble heat flux; e = the latent heat flux; I = the net olar hortave radaton at the ater urface; = the net atmopherc longave radaton at the ater urface. The net radaton RN aocated th many factor uch a the olar zenth angle, the rver tranveral and cro-ectonal dmenon, rparan vegetaton and buldng. Here, e take uch factor nto account, except for the hadng effect of buldng. The net olar hortave radaton I, I and the net atmopherc longave radaton, are gven a I + S = S DIF DIR ( L)(1 α ) / + S ψ (1 ψ ) α (1 α ) DIF ψ (1 α ) + S DIR Lα (1 ψ )(1 α ) /(2h) (8) I + S = S DIR DIR L(1 α ) /(2h) + S L(1 2ψ ) α (1 α ) /(2h) + S DIF ψ (1 α ) + S DIF ( L) ψ α (1 α ) / + S ψ (1 2ψ ) α (1 α ) DIR DIF ψ (1 α ) (9) = ψ ε L ( 1 ψ ) ε ε σt ε σt (1) = ψ ε L + ψ ε ε σt ( 1 2ψ ) ε σt ε σt (11) here ubcrpt and denote the ater urface and the rver de all, repectvely, S DIR and S DIF are donard drect and dffue olar radaton on a horzontal urface at the top of a tream channel canopy, L = the donard atmopherc longave radaton; ψ = the ky-ve factor for the ater urface; ψ = the ky-ve factor for one de all; T = the urface temperature of the rver de all; h = the channel depth; = the channel dth; L = the hado length; ε and ε are the emvty of the ater urface and the rver de all, repectvely, α and α are the albedo of the ater urface and the rver de all, repectvely, σ = the Stefan Boltzmann contant. The ky-ve factor of the ater urface ψ and the rver all ψ are gven from Maon (13) a ψ = 2 [( h ) + 1] 1/2 h (12) 1 2 ( h ) 2 1/ + 1] }/( h ) ψ = {h + 1 [ (13) 2

5 The hado length L computed a (Kuaka et al., 14) h tanθ n L = z θ n (L < ) (L ) (14) here θ z = the olar zenth angle; θ n = the dfference beteen the olar azmuth angle and the tream channel orentaton. The rparan vegetaton and tructure crong the tream modfy the hortave and longave radatve fluxe. We modelled the attenuaton of the olar radaton by the rparan vegetaton a follo: S DIR = f SDIR (15) S DIF = f SDIF (16) f = 1 λi f (17) veg LAI f LAI = LAI L ) ( L L ) (18) ( mn max mn here f = an attenuaton factor for the rparan vegetaton, SDIR = drect olar radaton at the above-canopy level; SDIF = dffue olar radaton at the above-canopy level; I veg = a rparan vegetaton ndex ( : no vegetaton, 1 : vegetaton along one de, 2 : vegetaton along both de); LAI = the leaf area ndex of the rparan vegetaton; L max = maxmum value of LAI; L mn = mnmum value of LAI; λ = a calbrated contant to reflect the hadng effect by rparan vegetaton. The enble heat flux expreed a (Chapra et al., 15) c = c f ( u)( T T ) (19) 1 a here c = ; 2 f ( u) = u ; T a = the ar temperature ( C); u = the nd peed at a heght of 7 m (m/). The ncomng radaton at the above-canopy level (SDIR, SDIF and L ) and the latent heat flux n equaton (7) are computed by a et al. (8). The heat flux from the rver bed to the tream ater ( ) calculated from equaton (2) through (22). 2α ed = ρ ed c p ( Ted T) (2) H ed dt dt ed = k T T ) (21) h ( ed k h 2 2α ed H ed = (22) here T ed = the temperature of the rver bed layer; H ed = the effectve thckne of the rver bed layer; ρ ed = the denty of the rver bed layer; c p = the pecfc heat of the rver bed layer; α ed = the thermal dffuvty of the rver bed layer.

6 The urface temperature of the rver de all (T ) calculated by a mlar formulaton ung equaton (23) through (27). + I = H + G C C (23) dt dt g = k hg ( T Tg ) (24) H C = c f ( u)( T T 1 a ) (25) G C = ρ c g pg 2α H g g ( T T g ) (26) k hg = 2 2α g H g (27) here H C = the enble heat flux from the rver de all; G C = the heat flux from the rver de all nto the ground; H g = the thckne of the rver de all; T g = the nternal temperature of the de all; ρ g = the denty of the de all; c pg = the pecfc heat of the de all; α g = the thermal dffuvty of the de all. A dcrete form of equaton (2) rtten by equaton (28) after Chapra et al. (15). Equaton (28) mplctly olved by mean of the Gauan elmnaton method. dt Q 1 Q D 1 D = T 1 T + ( T 1 T ) + ( T + 1 dt V V V V 1 A da W T + dt ρ c h, p + V ρ c h, p H + ρ c, p H T ) (28) + D = D A /( Δx + Δx 1) / 2 (29) here ubcrpt denote rver element, Δx = the length of rver element. APPLICATION Study area We appled the hydrologcal model coupled th the heat energy tranport model to the Kanda Rver aterhed located n the heart of Tokyo, apan (Fgure 1). Trbutare run n four open channel and one covered channel n uptream ub-aterhed, and eventually merge to the mantream. The Momozono Rver a covered channel all along the tream (Fgure 1). The channel have a trapezodal cro-ectonal hape n mot of ther reache, ome of hch have a mall dtch on the bottom of the channel. The Kanda Rver aterhed ha a combned eer ytem and the aterhed can be dvded nto fve eer catchment. Seage generated n the catchment bounded by a dahed lne (Fgure 1) flo

7 Fgure 1. Outlne of the Kanda Waterhed nto to WWTP thn the aterhed (the Ocha WWTP and the Nakano WWTP), here treated effluent are dcharged nto the Kanda Rver. In all other catchment, the eage tranported to WWTP located outde the Kanda Rver aterhed through the eer ppe acro the aterhed boundary. ranfall th relatvely lght ntenty. Stormater flo n the ame route durng perod of Durng perod of heavy ranfall, the CSO n all eer catchment drectly dcharge nto the Kanda Rver ytem from the CSO outlet located thn the aterhed. Input data and parameter The man nput data requred to run the model are lted n Table 1. prepared ung ArcGIS. Spatal dtrbuton of correpondent data a Stream netork data a reproduced on the GIS platform from the dgtal map by the Geographcal Survey Inttute. The aterhed a dvded nto 9 ub-aterhed. Rver cro-ectonal area a approxmated a a trapezodal hape. The hape data a provded by the map obtaned from the Tokyo Metropoltan Government. The orentaton of the tream channel a calculated for each rver element by utlzng a tool of ArcGIS. Categorzed data of rparan vegetaton and tructure crong channel, hch ere prepared from aeral photograph, are attrbuted to ndvdual computatonal element of rver channel. The actual eer netork data a not ued. Intead, e

8 Table 1. Lt of man nput data ued for the coupled model mulaton Category Item Source Land urface condton Waterhed boundary Topography Land ue Natonal dgtal nformaton Dgtal map (5m by 5m DEM) Fne dgtal nformaton (13 type of land ue, 1m by 1m rater data) Meteorologcal and hydrologcal condton Sol type Precptaton (19 taton) Relatve humdty (1 taton) Geologc map Hourly data from the Tokyo Metropoltan Government Rver netork and hydraulc dmenon Anthropogenc condton Product of the Geographc Survey Inttute Ar temperature (3 taton) Wnd velocty (3 taton) Sunhne duraton (3 taton) Stream channel Rver profle Rparan vegetaton Crong tructure Populaton Seer catchment boundary Hourly data from AMeDAS by the apan Meteorologcal Agency Dgtal Map (1:25,) Map obtaned from Tokyo Metropoltan Government Aeral photograph Aeral photograph Natonal cenu data by the Mntry of Internal Affar and Communcaton Map obtaned from the Tokyo Metropoltan Government Table 2. Parameter ued for the heat tranport model parameter Rver bed Rver de all Thckne H ed, H g (m).1.3 Denty ρ ed, ρ g (g/cm 3 ) Specfc heat c p, c pg (cal/g/k) Thermal dffuvty α ed, α g (cm 2 /).8.2 Albedo α, α.8.3 Emvty ε, ε.95.9 Value for ater urface aumed that the flo n the eer ppe folloed the terran of the aterhed, hch a found to be a reaonable aumpton. There are three categore of parameter ued n the WEP model (a et al., 8~1): (1) parameter of land urface and rver channel ytem; (2) parameter of vegetaton; and (3) parameter of ol and aqufer. Parameter for the heat tranport model are addtonally pecfed follong Chapra et al. (15) and Oke (16) a lted n Table 2. All of parameter ere ntally pecfed from lterature or etmated accordng to land cover nformaton, obervaton data, and ome parameter are elected for model calbraton. The model calbraton a performed for both tream flo and temperature at locaton here oberved value are obtaned. For flo mulaton, ome flood hydrograph and lo flo ere checked to calbrate parameter uch a the Mannng roughne of the rver flo, β n equaton (1) and the hydraulc conductvty of the rverbed. Parameter β ued to gve V lm n equaton (1) a et to 5 follong the calbraton. Calbraton of parameter for the tream temperature ncludng λ n equaton (17) a carred out to reproduce t eaonal and durnal varaton. Rato of the mpervou area, four type of pervou area and ater urface for each computatonal meh (1m by 1m) ere gven by reclafyng the fne land ue data ung the parameter n Table 3, hch ere deduced referrng to prevou tude (a et al., 9 and 1). The patal dtrbuton data of the topol a generated from geologcal map. The topol n the aterhed

9 Table 3. Land ue clafcaton parameter Land ue clafcaton ued n the WEP model Pervou area (PA) Impervou area (IA) Urban canopy rate n IA Land ue type of the fne dgtal nformaton Water urface rato Paddy rato n PA Tall vegetaton rato n PA Short vegetaton rato n PA Bare ol rato n PA foret paddy 1 other farmland under preparng vacant land ndutral ue houng area houng area commercal area road 1.86 park publc ork rver/lake 1.14 manly the Kanto loam, except for the alluval ol n rparan zone (Fgure 1). The phycal properte for each ol type uch a ol poroty, ol aturated hydraulc conductvty and ol moture ucton relaton curve ere gven from a et al. (9 and 1). Value of Mannng roughne coeffcent for rver flo and overland flo ere et to.15 and.1, repectvely. The ar-ater heat flux n the Momozono rver, a fully covered channel, a computed by ettng the drect and dffue olar radaton a zero and the donard longave radaton from the cover a aumed to be the ame a L. Model applcaton The coupled model a run for the mulaton from anuary 1 to December 31 of 25 n a tme tep of 1 hour (except for overland flo and rver flo routng th a tme tep of 1 mnute) and a grd cell ze of 1m 1m. The computatonal doman nclude 962 grd cell. Rver channel ere dvded nto computatonal element th the longtudnal length of 39m - 45m. The headater of the tream a mantaned by the pumped groundater. Thu, the uptream boundary condton ere et by the contant tream flo and varable ater temperature deduced from the ground temperature. The temperature of the bae flo from the groundater a lkee et at an equvalent temperature of the ground at the depth of the rver bed. Reult Streamflo and nflo to WWTP The mulated reult of lo treamflo ere compared th thoe oberved at Kotobuk and Chtoe (Fgure 1,

10 Table 4. Comparon of mulated tream flo th oberved durng no-ranfall perod Locaton Perod Oberved average flo average flo Kotobuk 25/1/ m 3 /.55 m 3 / Chtoe 25/1/ m 3 /.1 m 3 / Flo rate (m 3 /) Oberved Flo rate (m 3 /) Oberved 7/9 18: 7/9 21: 7/1 7/1 3: 7/1 6: 7/9 18: 7/9 21: 7/1 7/1 3: 7/1 6: Flo rate (m 3 /) /15 18: 8/15 21: 8/16 Oberved 8/16 3: 8/16 6: Flo rate (m 3 /) /15 18: 8/15 21: 8/16 Oberved 8/16 3: 8/16 6: Flo rate (m 3 /) Oberved Flo rate (m 3 /) Oberved Flo rate (m 3 /) 8/25 6: /4 12: 8/25 12: 9/4 18: 8/25 18: 9/5 8/26 9/5 6: 8/26 6: Oberved 9/5 12: Flo rate (m 3 /) 8/25 6: /4 12: 8/25 12: 9/4 18: 8/25 18: 9/5 8/26 9/5 6: 8/26 6: Oberved 9/5 12: Fgure 2. Comparon of mulated flood dcharge th oberved (left: Honan, rght: Aah) Table 4). Mot of the rver reache are covered by a concrete bottom lab and de all, hch prevent ater nteracton beteen rver flo and groundater. A a reult, the treamflo could be qute lo durng perod thout ranfall. Th tuaton a reproduced ell by the mulaton. flood dcharge durng four major torm event n 25 ere compared th hydrograph at Aah and Honan obtaned from oberved ratng curve and meaured ater level. hydrograph relatvely ell reproduced oberved one at Aah for three event (uly 9-1, Augut and

11 25 2 Oberved 25 2 Oberved Inflo (m 3 /) Inflo (m 3 /) /8 18: /9 6: 7/9 18: Oberved 7/1 6: 7/1 18: 7/11 6: 8/12 12: /13 12: 8/14 12: 8/15 12: Oberved 8/16 12: Inflo (m 3 /) 15 1 Inflo (m 3 /) /24 12: 8/25 8/25 12: 8/26 8/26 12: 8/27 9/3 9/4 9/5 9/6 9/7 9/8 Fgure 3. Comparon of mulated nflo to the Ocha WWTP durng four ranfall event Augut 25-26) and at Honan for to event (uly 9-1 and Augut 25-26) a hon n Fgure 2. Mot abrupt change of dcharge ere oberved durng the ranfall event of Augut 25-26, n hch the ater level roe about 1.5m thn 4 mnute. Smlar feature are mulated for th event even though hourly ranfall data are ued. hydrograph for ranfall perod from September 4 to 5, hch a caued by the approach of the typhoon No.14, overetmated the peak dcharge and the total volume at both locaton. Durng th perod, floodng occurred along the tream channel and the runoff a temporally tored n detenton reervor located uptream of the aterhed, hle the model doe not deal th thee procee. Fgure 3 ho the correpondent nflo to the Ocha WWTP. Durnal varaton and abrupt change of the nflo ere mulated ell, although the mulated bae nflo underetmated meaured one probably due to the ettng of the eepage modelng. Our obervaton hoed that the eepage account for about 2% of the total nflo to the WWTP n Tokyo (Nakayama et al., 17). Therefore, further verfcaton may be needed for the modelng of ol-ater eepage from the ground urroundng the eer ppe. Water temperature The mulated tream temperature are compared th thoe oberved (Fgure 4). Modeled tream temperature matched ell th thoe oberved at Goryo throughout the year. Modeled tream temperature at Mank ho larger ampltude of the durnal varaton than thoe oberved n the fall and nter eaon. Akebono, here e tarted temperature meaurement from November 25, exhbted flatter temperature varaton than thoe oberved at Goryo and Mank. Th manly becaue the ateater effluent from to WWTP compre the man porton of the treamflo at Akebono and thu the durnal temperature varaton domnated by the effluent temperature that ha mall durnal ampltude. In addton, our montorng detected udden decend of the tream temperature at Akebono, folloed by the oon recovery to the prevou temperature level. For example, the phenomenon occurred n the mornng of the 23rd of November, probably due to the temporal reducton n ateater effluent to.8m 3 / from t daly average of 2.1m 3 /. Thee abrupt temperature change at Akebono ere alo ell captured by the mulaton (Fgure 4). Stream

12 Stream temperature ( C) Stream temperature ( C) Stream temperature ( C) Stream temperature ( C) 3 25 Goryo Oberved 5 3/25 3/3 4/4 4/9 4/14 4/19 4/24 4/29 5/4 5/9 5/14 5/19 5/ Goryo Oberved 1 5 7/27 8/1 8/6 8/11 8/16 8/21 8/26 8/31 9/5 9/1 9/15 9/2 9/25 3 Mank Oberved 9/27 1/2 1/7 1/12 1/17 1/22 1/27 11/1 11/6 11/11 11/16 11/21 11/26 12/ Akebono Oberved (No ateater effluent) /21 11/22 11/23 11/24 11/25 11/26 11/27 11/28 11/29 11/3 12/1 Fgure 4. Comparon of mulated tream temperature th oberved The bottom fgure nclude reult for the hypothetcal cae of no ateater effluent. temperature mulated by aumng no ateater nput ere far belo the temperature mulated th ateater nput (Fgure 4, bottom), and the maxmum dfference of tream temperature a found to be approxmately 12 C. Th ugget that there a trong nfluence of ateater effluent on the tream temperature n the Kanda Rver, and potental mpact on the habtat for fh and nvertebrate and algae groth. CONCLUSIONS A frameork a preented for the tream temperature predcton under dtrbuted anthropogenc and natural heat ource n the urbanzed aterhed. The predctve model developed n th tudy baed on a model of heat tranport n rver ater ncorporated nto a phycally baed dtrbuted hydrologcal model (WEP model). Th coupled model can mulate dynamc hydrologcal repone of an urbanzed aterhed th a dranage ytem of rver channel and a combned eer netork, hch enable approprate predcton of nflo to ateater treatment plant and treamflo. Stream temperature predcton conder the nfluence of heat nput by ateater effluent, groundater eepage, urface runoff a ell a the atmopherc radaton, and the heat budget thn a rver canopy. Th model a appled to the Kanda Rver aterhed n Tokyo, and hoed that t could reproduce ell lo flo and flood runoff, ncludng nflo to

13 the WWTP. Overall magntude of the mulated tream temperature agreed ell th thoe of oberved. Impact of anthropogenc heat nput from WWTP ere found to be very gnfcant n nter. Abrupt change of tream temperature n a tme cale of everal hour ere attrbuted to the fluctuaton of the volume of ateater effluent. Further mprovement are neceary to more accurately mulate oberved eaonal and durnal varaton n the tream temperature throughout the year. ACKNOWLEDGMENTS Th reearch project a fnancally upported by CREST (Core Reearch for Evolutonal Scence and Technology) of the apan Scence and Technology Corporaton a a part of the reearch project Water and Energy Forcng due to Urbanzaton n Land-Atmophere-Coatal Sytem organzed by Prof. Manabu Kanda (Tokyo Inttute of Technology). REFERENCES 1. Knouch, T.: Impact of long-term ater and energy conumpton n Tokyo on ateater effluent: mplcaton for thermal degradaton of urban tream, Hydrologcal Procee, Vol.21, pp , Knouch, T., Yag, H. and Myamoto, M.: Increae n tream temperature related to anthropogenc heat nput from urban ateater, ournal of Hydrology, Vol.335, pp.78-88, Snokrot, B.A. and Stefan, H.G.: Stream temperature dynamc: meaurement and modelng, Water Reource Reearch, Vol.29, No.7, pp , LeBlanc, R.T., Bron, R.D. and FtzGbbon,.E.: Modelng the effect of land ue change on the ater temperature n unregulated urban tream, ournal of Envronmental Management, Vol.49, pp , Tung C., Lee T. and Yang Y.: Modellng clmate change mpact on tream temperature of Formoan landlocked almon habtat, Hydrologcal Procee, Vol.2, pp , Chen, Y.D., McCutcheon, S.C., Norton, D.. and Nutter, W.L., Stream temperature mulaton of foreted rparan area: II. Model applcaton, ournal of Envronmental Engneerng, ASCE, Vol.124, No.4, pp , Haag, I. and Luce, A., The ntegrated ater balance and ater temperature model LARSIM-WT, Hydrologcal Procee, Vol.22, pp , a, Y., N, G., Kaahara, Y. and Suetug, T.: Development of WEP model and t applcaton to an urban aterhed, Hydrologcal Procee, Vol.15, No.11, pp , a, Y., N, G., Yohtan,., Kaahara, Y. and Knouch, T.: Couplng mulaton of ater and energy budget and analy of urban development mpact, our. of Hydrologc Eng., ASCE, Vol.7, No.4, pp , a, Y., Knouch, T. and Yohtan,.: Dtrbuted hydrologc modelng n a partally urbanzed agrcultural aterhed ung ater and energy tranfer proce model. our. of Hydrologc Eng., ASCE, Vol. 1. No. 4, pp , Herb, W. R., anke, B., Mohen, O. and Stefan, H. G.: Thermal polluton of tream by runoff from paved urface, Hydrologcal Proce, Vol.22, pp , Carla, H. S. and aeger,.c.: Conducton of heat n old 2nd edton, Oxford Unv. Pre, London, Maon, V.: A phycally-baed cheme for the urban energy budget n atmopherc model, Boundary-Layer Meteorology, Vol.94, No.3, pp , Kuaka, H., Kondo, H., Kkegaa, Y. and Kmura, F.: A mple ngle-layer urban canopy model for atmopherc model: comparon th mult-layer and lab model, Boundary-Layer Meteorology, Vol.11, No.3, pp , 21.

14 15. Chapra, S.C., Pelleter, G.. and Tao, H.: QUAL2K: A modelng frameork for mulatng rver and tream ater qualty, veron 2.4: documentaton and uer manual, Cvl and Env. Eng. Dept., Tuft Unverty, Medford, MA., Oke, T.: Boundary Layer Clmate 2nd edton, Routledge, Ne York Nakayama, Y., Kanda, M. and Knouch, T.: The nvetgaton of the ater and heat tranfer n urban eage ytem baed on the temperature obervaton at the ateater treatment plant, ournal of apan Socety of Hydrology and Water Reource, Vol.2, No.1, pp.25-33, 27. (In apanee) APPENDIX NOTATION The follong ymbol are ued n th paper. a a n, b n = thermal dffuvty; = the Fourer coeffcent; c pg = pecfc heat of the de all; c p = pecfc heat of the rver bed layer; c p = pecfc heat of ater; f = an attenuaton factor for the rparan vegetaton; h t = channel depth; = tme; u = nd peed at a heght of 7 m; x z A CA = channel dth; = flo drecton; = depth from the ground urface; = cro-ectonal area; = uptream catchment area of the WWTP; CA j = catchment area at CSO outlet j; D = longtudnal dperon coeffcent; G C = heat flux from the rver de all nto the ground;

15 H = ater depth; H C = enble heat flux from the rver de all; H g = thckne of the rver de all; H ed = effectve thckne of the rver bed layer; I = net olar hortave radaton at the ater urface; I = net olar hortave radaton at the rver de all; c = enble heat flux; e = latent heat flux; h = ar-ater heat flux; = heat flux from the tream bed to the tream ater; = net atmopherc longave radaton at the ater urface; = net atmopherc longave radaton at the rver de all; I veg = rparan vegetaton ndex ( : no vegetaton, 1 : vegetaton along one de, 2 : vegetaton along both de); L LAI = hado length; = leaf area ndex of the rparan vegetaton; L max = maxmum value of LAI; L mn = mnmum value of LAI; L = donard atmopherc longave radaton; Q = flo rate; Q n j = nflo to a computatonal meh here the CSO outlet j located; Q lm j = outflo to a dontream computatonal meh from the meh here the CSO outlet j located; Q np = magntude of non-pont ource (urface flo, uburface flo and groundater flo); Q of j = overflo to the rver from the CSO outlet j; Q p = magntude of pont ource (ateater effluent from WWTP and CSO); RN SDIF = net radaton at the ater urface; = dffue olar radaton at the above-canopy level; S DIF = donard dffue olar radaton on a horzontal urface at the top of a tream channel canopy;

16 SDIR = drect olar radaton at the above-canopy level; S DIR = donard drect olar radaton on a horzontal urface at the top of a tream channel canopy; T = ater temperature; T a = ar temperature; T g = nternal temperature of the de all; T gd (z, t) = ground temperature at depth z and tme t; T np = temperature of non-pont ource (urface flo, uburface flo and groundater flo); T p = temperature of pont ource (ateater effluent from WWTP and CSO); T ed = temperature of the rver bed layer; T = urface temperature of the rver de all; V = ater volume of tream element; V lm = maxmum nflo capacty at the WWTP; V TP = treatment capacty of the WWTP; W h = net heat load from hydrologcal ource; α g = thermal dffuvty of the de all; α = albedo of the ater urface; α ed = thermal dffuvty of the rver bed layer; α = albedo of the rver de all; β = a calbrated contant to compute V lm ; ε = emvty of the ater urface; ε = emvty of the rver de all; λ = a calbrated contant to reflect the hadng effect by rparan vegetaton; θ n = dfference beteen the olar azmuth angle and the tream channel orentaton; θ z = olar zenth angle; ρ g = denty of the de all; ρ ed = denty of the rver bed layer; ρ = denty of ater;

17 σ = the Stefan Boltzmann contant; ψ = ky-ve factor for the ater urface; ψ = ky-ve factor for one de all; Δx = length of a rver element.