Stream flow Simulation by Wetspa Model in Garmabrood Watershed of Mazandaran Province, Iran

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1 ISB th Internatonal Conference on Chemcal, Agrculture, Envronment and atural Scences (CAES-017) Kuala Lumpur (Malaysa) ov. 0-1, 017 Stream flow Smulaton by Wetspa Model n Garmabrood Watershed of Mazandaran Provnce, Iran Mohammad Reza Dahmardeh Ghaleno 1, Mohammad ohtan 1 and Saeedeh Khaled 1 Assstant Professor, Department of Rangeland and Watershed Management, Faculty of Water and Sol, Unversty of Zabol, Zabol, Iran M.Sc. student, Department of Rangeland and Watershed Management, Faculty of Water and Sol, Unversty of Zabol, Zabol, Iran Abstract: Smulaton of stream flow, predcton of the hydrologcal behavor of watersheds and understandng of varous components of the hydrologcal cycle s mportant n order to plan for protecton of water resources. The present paper ams to shed lghts on applcaton of a spatally dstrbuted hydrologc model WetSpa workng on a daly tme scale. The model combnes elevaton; sol and land use data wthn GIS, and predcts flood hydrograph and the spatal dstrbuton of hydrologc characterstcs throughout the watershed. Ths model uses a modfed ratonal method for runoff estmaton. In ths model, runoff s routed along the flow path usng Dffuson-Wave Equaton n turn depends on the slope, velocty and flow path characterstcs. Garmabrood watershed s located n Mazandaran provnce n Iran wth coordnates to E and of to the catchment s covered by an area about 11 km and elevatons n the catchment range from 17 to 3144 m at the outlet, wth average slope of 7.77%. Results of the smulatons show a good agreement between calculated and measured hydrographs at the outlet of the basn. The results showed that WetSpa model predcts the daly hydrographs and maxmum flow rate wth good accuracy, 59% and 80.79% respectvely accordng to the ash Sutclff crtera. Also WetSpa model has well smulated runoff n valdaton perod Keywords: Wetspa model, Runoff, Flood predcton. 1. Introducton Developng the technology of geographcal nformaton system has allowed wdespread accessblty and management on parameters and spatal hydrologc varables. These technques have provded effectve methods to study hydrologc systems, and play an mportant role for expandng the spatally dstrbuted models based on GIS, n whch the spatal nformaton are formed along wth the hydrologc data as area unts [3]. Consderng mssng statstcs and hgh complexty and mpossblty of fully understandng hydrologcal ecosystem n most of watersheds, applyng some approaches and method to estmate runoff n watersheds wth mssng data or ncomplete statstcs wll be essental [3]. Gven adverse consequences and numerous damages caused by runoff as well as complexty of precptaton - runoff process, many methods and models have been proposed. Precptaton-runoff models can smulate processes wthn watershed and serves as a tool to estmate runoff and study hydrologcal processes [6]. WetSpa s a dstrbuted, contnuous and physcal model wth daly or hourly tme step explanng processes of precptaton, runoff and evapotranspraton for both smple and complex contexts. Reference [6], appled WetSpa model wth one hour tme step n small watershed wth an area 67.8 km n Belgum. Statstcal analyss of hydrographc derved from model and observed hydrograph showed that model can well predct ts normal 50

2 and flood currents. Reference [8] appled WetSpa hydrologcal model to predct runoff flow n Smu, n the area of Lake Vctora n Tanzana. The results of the model showed that model can route flow n rver. Reference [3] n a research tlted as dstrbuted hydrologcal modelng and senstvty analyss n Slovaka Tursa basn found a good conferment between observed and calculated hydrograph at the basn outlet. WetSpa model predcted the daly runoff wth good accuracy, between 74 81% accordng to the ash Sutclff crtera. The results showed that correcton factor of actual evapotranspraton and Kg (evaporaton of groundwater) accounted for the hghest and lowest relatve senstvty respectvely. Reference [10] evaluated applcaton of dstrbuted hydrologcal WetSpa model for Dstrbuted Model Integraton Project n US. They used ntegraton crtera that reflect the dfferences n shape, sze and volume of observed and smulated hydrographs for model performance assessment. Reference [5] evaluated WetSpa dstrbuted hydrologcal model n the Gorganrood basn characterzed wth an area of 6717 km. The smulaton results showed a good agreement between calculated and observed hydrograph, and gven ash - Sutclffe crtera, model predcted daly hydrograph model accuracy about 71 to 77%. In another study usng the WetSpa model, [1] smulated effect of land use change scenaros on flow hydrograph n Karkhe Dnawar basn. In ths study, the capabltes of spatally dstrbuted hydrologc WetSpa model - whch smulates the rver flow wth hourly or daly tme nterval - along wth GIS technques has been appled, to prepare the map of and depresson storage capacty. Results showed that model has potental to smulate daly hydrographs usng 66% ash Sutclffe coeffcents. In ths paper, the methodology of producng the depresson storage capacty n Dnevar watershed km located n Kermanshah provnce, Iran n turn are essental to dentfy and prortze stormy. To put n a nutshell, these two parameters n WetSpa model are extracted from the Lookup table based on the three maps of land use, slope and sol. Reference [] appled PEST model to nvestgate uncertanty of the WetSpa model parameters and ts mpacts on sgnfcant uncertanty n model predcton n Slovaka's Toursa basn. The results showed that relatve evapotranspraton correcton factor has the hghest relatve senstvty. Model uncertanty analyss provded nsght nto the proper parameter sets and proved that model parameter uncertanty does not have sgnfcant effects on uncertanty predcton. Reference [11] dealt wth WetSpa model valdaton and verfcaton n rural basns (Wkra, Kamenna, Sdra) n Poland. The model was auto-calbrated usng PEST, ash Sutclffe and proved relable qualty for modelng hgh flow n two basns, Sdra and Kamenna; however, low flow qualty was not confrmed. Values for Wkra basn were rated very good and good qualty. Reference [1], smulated rver's flow usng WetSpa dstrbuted hydrologcal model smulatons n Chehelcha watershed located n Golestan provnce. Results of model smulatons based on ash-sutclffe crtera estmated daly hydrograph wth relatvely good accuracy over 50 and 57%, for the estmated calbraton and valdaton perods respectvely. Reference [13] assessed Impact of clmate change and urbanzaton drawng upon Wetspa model n Belgum Groteete basn. The results showed that smultaneous effect of these two factors sgnfcantly ncrease the frequency of floods n wnter and low flow n summer. In general, an enormous study n dfferent countres such as Luxembourg, Belgum, Slovaka, Hungary, Tanzana, Thaland, Poland and Iran suggest that WetSpa model n dfferent areas wth varous geography and clmate and dverse topographes as well as n small to very bg basns s well able to smulate flow rangng from flood or daly flow of rvers. In such a way that allowed researchers to calculate mpact of varous factors affectng such as clmate change and land use change on outlet flow as well as the dfferent components of the water balance and hydrologcal phenomena n dstrbuted manner.. Materals and Methods Garmabrood watershed wth an 1133 square klometers area s located n Mazandaran provnce n Iran wth coordnates " to " E and " to ". Its mnmum and maxmum sea above elevaton s 13 and 3136 m respectvely [9]. Fg 1 shows study area locaton. 51

3 Fg. 1: Locaton of the study area. WetSpa s a dstrbuted, contnuous and physcal model wth daly or hourly tme step that explans processes of precptaton, runoff and evapotranspraton for both smple and complex contexts. Ths model uses a modfed ratonal method for runoff calculaton. In ths model, runoff s routed along the flow path usng Dffuson-Wave Equaton n turn depends on the slope, velocty and flow route characterstcs. In ths model for each cell grd, four layers are consdered n vertcal manner whch ncludes followng: canopy cover layer, root zone, transportaton zone and saturaton zone. To runnng model, three land use, sol texture, and elevaton classes' maps are requred. Among clmatologcal parameters, daly precptaton, daly temperature and daly evapotranspraton are necessary. Elevaton classes' map for basn was prepared n sze 90 m. Topographc data were also obtaned usng regonal cartography maps. To run model, clmate parameters on a daly bass, are requred whch these data were provded from the meteorologcal statons n the Garmabrood dstrct of Mazandaran provnce. The Watspa model uses the Tssen method to obtan average clmatc parameters n basn. It also s able to predct and smulate flood n the future. Outlet dscharge s also obtaned from the hydrometrc staton n Garmabrood watershed outlet. In ths paper, the daly precptaton, temperature and dscharge data are obtaned from Mazandaran Regonal Water Co. WetSpa model frst calculates water balance n root zone because ths s the most mportant area n water retenton and at the same tme t controls surface and subsurface runoff, evapotranspraton and groundwater flow. Equaton 1 presents water balance n root zone for each cellular grd: Where D denotes root depth (m), denotes sol mosture varaton (m3/m3), s tme step (h/day), P s precptaton (m/h/d), s ntal loss ncludng stem flow(ia) and depresson storage (Da) n tme step m/h/d, V s surface runoff or surplus precptaton, E s evapotranspraton(m/h/d), R s percolaton on root zone(m/h/d) and F s subsurface flow n tme(m/h/d). Model apples modfed ratonal method to calculate runoff and apples GDD to estmate snow melt runoff. Subsurface s obtaned based on Darcy's law and knematc wave equatons. Groundwater flow s determned usng lnear reservor method. Runoff s routed along the flow path usng dffuson wave approxmatons equaton, whch s n turn dependent on slope, velocty and flow path parameters. Stream flow and surface flow were routed along rver by Sant-Venant dffuson wave approxmatons equaton and s calculated usng followng relaton: Where Q s dscharge (m/s), t s tme (days), X s dstance n flow drecton (m), C denotes knematc wave velocty n pxel and s calculated from (3). V s flow velocty (m/s) and d s dffuson factor n pxel derved from (4) where R s hydraulc radus or average depth and S0 s stream bed slope and s constant. These two parameters depend on velocty and depth [5]. To calculate flow rate at the end of the flow path, Equaton 5, s used as a Sant-Venant lnear response functon [4]. (3) (1) () (4) 5

4 Consderng a lmted system between upstream and downstream cross-secton, soluton for equaton n pxel outlet can be expressed usng a Gaussan probablty densty functon as n (6). U (t) = (6) Where U(t) s flow response functon used to determne unt hydrograph and allows routng flow path to basn outlet.t0 s flow travel tme(t), s flow tme standard devaton and fnally flow hydrographs n outlet whch combned n downstream are calculated from (7): (7) Where represents dscharge, U s flow path response functon, s lag tme and V s outlet runoff volume. Model nputs nclude dgtal elevaton data, sol type, land use, tme seres of precptaton and evaporaton so that all hydrologcal processes cab be smulated n Gs. In the present research, daly data on flow, ranfall, temperature and evaporaton n Terosk hydrometrc statons for years , , and were used for calbraton and Valdaton..1. Model Valdaton and Effcency Metrcs Model Bas Model bas can be smulated as relatve mean dfference between the observed and predcted flow n a great smulaton and these crteron s expressed as follows: QS Qo 1 MB (8) Qo 1 Were MB s model bas, Qs and Qo represents smulated and observed flow n th tme step (m3/s) and s the number of tme steps durng smulaton. MB low values ndcate a better fttng and value zero represents perfect smulaton of observed flow. RMSE XO XS RMSE (9) wherexo and XS s observed and smulated dscharge respectvely, represents number of tme steps durng smulaton. The lower ths value, the better smulaton model wll be and t has not a gven nterval. ash-satcleffe coeffcent ash-sutclffe crteron (1970) ndcates that how well flow rates smulated by the model are correct, the equaton s as follows. Qs Qo S 1 1 Qo Qo 1 (10) Where S s ash-satcleffe effcency ndex used to evaluate potental to smulate flow channel, rangng from a negatve value to 1 and s 1 represents full complance between observed and smulated hydrograph. ash-satclffe Low Logarthmc ash - Sutclffe (11), focuses on evaluaton of low-flow smulaton. (5) 53

5 Qs lnqo ln 1 SL 1 (11) lnqo ln Qo 1 log ash-sutclffe effcency coeffcent SL s used to assess low flow rates. In a complete smulaton, SL equals to one. ash-satclffe Hgh ash Sutclffe crteron provded n (1) whch s used to evaluate potental to smulate hgh flow. 3. Results SH Qo QoQs Qo Qo QoQo Qo Once wetspa model was run, gven daly data on flow, ranfall, temperature, evaporaton and land use, sol and dgtal elevaton maps, frst model was calbrated for a two years perod ( to ) and was valdated for two statstcal years ( to ). Results are presented n table 1. As t can be seen n Table 1, results of the assessment crtera ndcated that n calbraton perod model was run wth necessary effcency. TABLE I: Values for Model Effcency Crtera Durng Calbraton Perod Effcency crteron calbraton Valdaton model bas to flow volume balance RMSE Total ash-satclffe coeffcent (%) ash-satclffe hgh (%) ash-satclffe low (%) Comparson of observed and smulated hydrograph gven fg and 3 shows that model can well smulate hgh flow (peak flow) to runoff estmaton, but t has low accuracy n predcton of low flow whch t can presumably attrbuted to smplfcaton of groundwater n model or lack of accurate evapotranspraton of groundwater estmaton durng dry perods. At the same tme, usng base flow n the summer to agrculture and farmng can be consdered as determnant factor. (1) Fg. : Model calbraton durng two statstcal years ( to ) 54

6 Fg. 3: Model valdaton durng two statstcal years ( to ) 4. Dscusson and Concluson Untl now, Wetspa model has been appled and studed n enormous areas ncludng Barbc basn n Belgum [4], Alzette Rver Basn n Luxembourg [7], karst rver basn Somu n Vetnam [6], Hornad watershed n Slovaka [3]. Lterature revew ndcated that model mght well handle a varety of hydrologcal processes under dverse topography, sols, land-use, and areas and has great potental n ths feld. In ths study, model was valdated n Garmabrood watershed wth tme seres -years data on daly ranfall, temperature, evaporaton rate. Accordng to calbraton results, model outperforms under hgh flow compared to hgh flow whch ths may be attrbuted to model weakness n low flow estmaton but as a whole model smulated total flow wth acceptable accuracy. In ths case, small ash - Sutclffe coeffcent for low flows can be found n elsewhere [10], [3] and [8]. However valdaton results are unacceptable and ths may be due to the model structure or data and basn condtons. 5. Acknowledgments Ths research was supported by the Unversty of Zabol wth the UOZ-GR Grant code. 6. References [1] M. Aznmehr, A. Bahremand, and A. Kabr, Smulatng the effects of landuse change scenaros on flow hydrograph usng the spatally dstrbuted hydrologcal model, WetSpa, n the Dnvar Watershed, Karkheh, Iran, Watershed Engneerng and Management, vol. 7, pp , 016. [] A.Bahremand, and F. De Smedt, Dstrbuted hydrologcal modelng and senstvty analyss n Torysa watershed, Slovaka, Journal of Water Resources Management, vol., pp , 007. [3] A.Bahremand, F. De Smedt, J. Corluy, Y.B. Lu, J. Poorova, L. Velcncka, and E. Kunkova, WetSpa Model Applcaton for Assessng Reforestaton Impacts on Floods n Margecany Hornad Watershed, Slovaka, Watershed Resource Management, vol. 1, pp , 006. [4] F. De Smedt, Y.B. Lu, and S. Gebremeskel, Hydrologcal modelng on a catchment scale usng GIS and remote sensed land use nformaton. pp: In: C.A. Brebba (ed.), Boston: WTI Press [5] A. Kabr, M. Mahdav, A. Bahremand, and. oora, Applcaton of a geographcal nformaton system (GIS) based hydrologcal model for flow predcton n Gorganrood rver basn, Iran, Journal of Agrcultural Research, vol.5, pp. 3-31, 010. [6] Y.B. Lu, and F. De Smedt, Flood Modelng for Complex Terran Usng GIS and Remote Sensed Informaton, Water Resources Management, vol. 19, pp ,

7 [7] Y.B. Lu, S. Gebremeskel, F. De Smedt, L. Hoffmann, and L Pfster, A dffusve transport approach for flow routng n GIS-based flood modelng. Journal of Hydrology, vol. 83, pp , 003 [8] J. Rwetabula, F. De Smedt, and M. Rebhun, Predcton of runoff and dscharge n the Smyu Rver (trbutary of Lake Vctora, Tanzana) usng the WetSpa model. Hydrology and Earth System Scences. Vol. 4, pp [9] K. Saber Chenar, H, Abghar, M, erfanan, and S. Gholzadeh, Short-term model of optmzaton operaton of water resources usng partcle swarm optmzaton and compared wth genetc algorthm. Watershed Management Research. vol. 97, pp.97: [10] A. Safar, F. De Smedt, and F. Moreda, WetSpa model applcaton n the Dstrbuted Model Intercomparson Project (DMIP). Journal of Hydrology. vol. 418, pp.78-89, 01. [11] B.Porretta, J. Chormansk, S. Ignar, T. Okruszko, A. Brandyk, T. Szymczak, and K. Krezalek, Evaluaton and verfcaton of the WetSpa model based on selected rural catchments n Poland. Journal of Water Land Dev. vol.14, pp , 010 [1] F. Yaghoub, and A.R. Bahremand, Streamflow Smulaton usng Spatally Dstrbuted Hydrologc Model, WetSpa n Chehel-Cha Watershed n Golestan Provnce. Journal of Water Land Dev. vol.18, pp , 011. [13] T. Vansteenkste, M. Tavakol, V. tegeka, and P. Wllems, Clmate change mpact on rver flows and catchment hydrology: a comparson of two spatally dstrbuted models. Hydrologcal processes. vol.7, pp ,