Modeling Suspended Sediments in Dez Basin (Case Study: The Tale Zang Hydrometric Station)

Transcription

1 International Reearch Journal of Applied and Baic Science. Vol., 3 (2), , 2012 Available online at ISSN X 2012 Modeling Supended Sediment in Dez Bain (Cae Study: The Tale Zang Hydrometric Station) Mohammad Heidarnejad 1, Ali Gholami 2 1.Department of Irrigation, Science and Reearch Branch, Ilamic Azad Univerity, Khouzetan, Iran 2.Department of Soil Science, Science and Reearch Branch, Ilamic Azad Univerity, Khouzetan, Iran Correponding author: Mohammad Heidarnejad, m.heidarnejad@khouzetan.rbiau.ac.ir ABSTRACT: The flow dicharge i alway regarded a the mot important ediment tranport factor, but practically different ediment value have been meaured for a certain value of flow dicharge, hence other factor are alo effective in ediment tranport. In thi reearch, it ha been attempted to modify the ediment rating equation through conidering factor affecting ediment tranport uch a meaurement time. For thi purpoe, the data related to flow dicharge and long-term daily ediment dicharge in Tale Zang Hydrometric tation were ued which i among the firt-cla tation contructed on Dez river. The reult of data homogeneity tet in thi tation howed that all dicharge data are homogenou with a ignificance level equal to 91.4%. Alo baed on the Kolmogorov goodne-of-fit tet, the log-normal ditribution wa elected a the bet tatitical ditribution for annual average dicharge data. Then, the data related to ediment dicharge and the daily flow dicharge were modeled in five mode, i.e. monthly, eaonal, highprecipitation and low-precipitation month, claification and without data eparation and the tatitical index known a minimum mean quare error (MSE) wa ued in order to elect the bet model. The model in which the data were eparated in a monthly manner wa introduced a the modified ediment rating equation and the amount of upended load wa etimated about 345 million of ton during the entire tatitical period, uing the monthly model. Keyword: upended load, ediment rating equation, Tale Zang, Kolmogorov, mean quare error. INTRODUCTION The edimentation i regarded a a very eriou and important natural hazard in development of countrie. The World Bank ha etimated the equivalent lot capacity of dam reervoir, only reulted by edimentation, to be 6 billion USD per year in 1999 that, of coure, will increae by contruction of more reervoir (Fan, 1999). Hence, etimation of upended load in river, which contitute the major part of ediment depoited in dam reervoir, i of paramount importance. The upended load refer to ediment that remain in upended tate for a coniderable period of time due to upward component of turbulent flow (Kuchakzadeh et.al, 2000). In other word, when the aggregate i urrounded by fluid, there i alway a tendency of being depoited for the oil due to it weight, but the hydraulic factor like the velocity hinder thi phenomenon. The firt phyical model of upended ediment wa introduced by Dupuit in Forchheimer offered an equation for upended ediment uing the ubtrate ediment theory and a light modification (Najmaei, 1989). Nowaday, variou method have alo been made common in order to etimate the upended load. In our country, determination of upended ediment load i motly done uing meaurement performed in hydrometric tation, o that the dicharge meaurement i performed imultaneouly with ediment ampling and thee ample are then tranported to local or central laboratorie and are ubjected to vicometer meaurement and baed on the reult obtained from thi vicometry, one can provide the dicharge-ediment curve and obtain the amount of upended olid

2 particle for different time period (like an annual bai). It hould be noted that the tatitic employed i related to the long-term period, otherwie there would be high diperion in dicharge-ediment curve (Majedi and Zaker,1998). The relation that one can etablih between ediment dicharge and flow dicharge i a follow (Shafai, 1998): b (1) = a W In which: = ediment dicharge, uually in term of ton per day. w = flow dicharge, uually in term of m 3 /. And a, b are equation coefficient. In fact, by meauring the flow dicharge, ampling the depoited particle and experimental vicometry and preparing different curve and related calculation, one can find out the value of water and ediment croing the ediment meaurement tation over long period of time. adimi and oddoui (1998) analyzed the upended ediment of diolved material in Namak Lake (Perian for Salt Lake) bain and found out that the exponential equation model i the bet type of regreion relation between data of flow dicharge and correponding data related to upended ediment dicharge in that bain. Horowitz (2002) addreed the prediction of upended load in the Miiippi river uing ediment rating curve and found out that the ediment rating curve can be ued for bet evaluation of annual ediment load in a 20-year period. Eder et al. (2010) addreed the tudy of upended ediment load regarding hyterei effect and found out that ome parameter uch a rainfall amount, water percentage of oil and maximum rainfall intenity are affective on upended ediment load. Carlo et al (2011) invetigated the bain cale and it effect on upended ediment load. Their reult howed that there i a direct relationhip between bain urface area and the ediment amount. In thi reearch, it ha been attempted to modify Equation (1) uing flow dicharge and long-term daily ediment dicharge (48 year), while conidering the factor affecting ediment tranport uch a meaurement time, and etimating the upended ediment load in Tale Zang hydrometric tation uing the modified equation. MATERIAL AND METHODS The bain area of the Dez river i geographically retricted between 10 o 48 ' to 21 o 50 ' eat longitude and 31 o 34 ' to 34 o 7 ' north latitude. Total urface area of the bain amount to km 2 and it perimeter i equal to 900 km. Thi bain i located on outhwetern lope of Zagro Mountain and it land uually have a teep lope and for thi reaon and becaue of interference of other factor like human activitie, irregular and uninterrupted grazing (continuou cut down of tree), the iue of eroion and ediment play effective role. The hydrometric and ediment meaurement tation in the entrance of the Dez dam known a the Tale Zang tation i among the firt-cla tation contructed on the Dez river. Thi tation i 20 km far from the dam location. The bain urface area i km 2 in the poition of the tation. The meaurement of water dicharge in thi tation have been tarted ince 1334 and the annual mean dicharge i m 3 /(Minitry of Energy, 1996). In order to modify the ediment rating equation in the Tale zang hydrometric tation and before any action with regard to analyzing the tatitic of ediment dicharge and daily current, it i neceary to inure for quality and homogeneity of data. Therefore, the oftware TH wa employed for teting the data homogeneity which include an advanced verion of Smirnov- Kolgomorov method and i baed on comparing experimental ditribution performance in two ection of a ample. Alo, the Kolmogorov goodne-of-fit tet wa performed uing thi oftware in order to elect the bet tatitical ditribution for dicharge data. Then, regarding the error in the ediment rating equation (Equation (1)), thi equation wa modified through conidering factor affecting ediment tranport like meaurement time and flow dicharge, o that the ediment dicharge and daily dicharge data were modeled in 5 mode, i.e. without data eparation (Model A), monthly eparation (Model B), eaonal eparation (Model C), high-precipitation and low-precipitation month (Model D) and claification (Model E). 403

3 In the above tate, high-precipitation and low-precipitation month are referred to thoe month whoe average monthly dicharge are larger than or equal to average annual dicharge and lower than it, repectively. Alo in the claification model, data eparation were conducted in three range, i.e. lower than annual average dicharge (cla 1), between the average and twice a much (cla 2) and higher than twice the annual average dicharge (cla 3). Then, the regreion relationhip wa etablihed between correponding data of water dicharge and upended ediment dicharge baed on the invetigated model, and then the coefficient of ediment b,a ) were obtained (which are the ditance between the interection of the bet fitting rating equation ( line with vertical axi and origin and the lope of the bet fitting line on the logarithmic paper, repectively) and the ediment rating equation wa obtained for different model. Moreover, in order to elect the mot uitable model, the tatitical characteritic minimum mean quare error(mse) wa employed uing the below equation and the oftware MINITAB: = ( log io log ) SSE ic (2) SSE MSE = (3) DF (4) R= ( log i log )( log wi log w) 2 ( log i log ) ( log wi log w) In above equation: SSE= um of quared error, MSE= mean quared error, R= Correlation coefficient, io = calculated upended ediment dicharge, wi = meaured flow dicharge, w = average meaured dicharge, = average meaured upended load, DF = degree of freedom. Finally, uing the modified model and regarding the daily flow dicharge, the amount of upended load wa etimated during the entire deired tatitical period in the Tale Zang hydrometric tation. RESULTS The reult obtained from data homogeneity tet in the Tale Zang hydrometric tation how that the data related to average daily dicharge are homogeneou with a ignificance level equal to 91.4% (Figure 1). Alo, uing the Kolmogorov goodne-of-fit tet, the log-normal ditribution i the bet tatitical ditribution for average annual dicharge data whoe obtained reult i hown in Figure 2. In thi diagram, Pf repreent the probability of fitting index. The ummary of deired equation from invetigated model in the Tale Zang hydrometric tation i hown in Table 1. Alo by ubtituting the daily dicharge into equation of the monthly elected model, the amount of upended load during the entire tatitical period under tudy, wa etimated equal to 345 million of ton. Alo, the ediment rating curve for the entire year i hown in Figure

4 Figure 1: The reult of homogeneity tet for data related to flow dicharge in the Tale Zang tation Figure 2: The reult of fitting tet for tatitical ditribution in the Tale Zang tation 405

5 (ton/day) y = x R 2 = w (m 3 /ec) M O D E A Figure 3: The ediment rating curve for the entire year in the Tale Zang tation Table 1- Summary of parameter conidered from invetigated model in the Tale Zang tation Separation of data Time of meaureme nt All year Claificatio n of rate All clae of rate clae All clae of rate DF 361 a b R (%) 94 SS E MS E March April May June B July Augut September October November December January February Spring Summer All clae C Fall of rate Winter High water All clae D month of rate Low water month Cla E All year Cla2 Cla = Sum of quared error= SSE, correlation coefficient= R, ediment rating equation= ( of freedom= DF, mean quare error for each model= (MSE) m, mean quared error=mse 0.08 b a w ( )m MS E ), degree 406

6 CONCLUSIONS The reult obtained how that the coefficient of the ediment rating equation i a function of elected model and the quality of data eparation. The relationhip between upended ediment and dicharge i of direct type and the amount of upended ediment alo increae with increae of dicharge. Regarding the minimum mean quare error criterion over which the difference between ediment tranport function and the meaured data reache a minimum, model B wa introduced a the modified ediment tranport model in the Tale Zang hydrometric tation in which the data eparation i conidered a monthly. In fact thi model i highly in accordance with the effect of climate factor (uch a rainfall) and hydrological factor (uch a runway) which appear in data eparation in a monthly manner. In contrat, the model in which no data eparation ha been performed ha the highet error value in etimating the upended load which agree with the reult of Moaedi in Atrak bain (reference(moaedi, 1998)). Alo, regarding the more uitable reult of the monthly model in thi reearch, it i uggeted to tudy thi model in ome other hydrometric tation with different climate condition in order to make the reult more reliable. REFRENCES Fan SS (1999) An overview of three edimentation tudie in the US, n: Jayawardena, A. W., J. H. W. Lee, and Z. Y. Wang(ed). River Sedimentation Theory and Application. alkema, otterdam, PP Kuchakzadeh S and Yuefi K (2000) Theory and application of ediment tranport, Univerity of Tehran pre, 446 P. Najmaei M (1989) Engineering hydrology, econd volume, IUST publication, 608 P. Majedi M, Zaker H (1998) Method of ediment meaurement and dicharge of ediment from reervoir dam, proceeding of 4 th workhop of profeional committee in dam hydraulic, 19 P. Shafai Bajetan M (1998) Hydraulic of ediment, Shahid Chamran Univerity of Ahvaz, 470 P. adimi F and Sobhani A (1998) Determining the tatitical ditribution pattern for upended ediment of Namak Lake bain, Reearch and Contruction, No. 44, PP Horowitz A J (2002) The ue of rating (tranport) curve to predict upended ediment concentration: a matter of temporal reolution. Turbidity and other ediment urrogate workhop,u.s.geological Survey, 7P. Eder A, Strau P, Krueger T, uinton J N (2010) Journal of hydrology, 389( ), Elevier. Carlo Gonzalez J, Ramon J, Batalla A (2011) Journal of CATENA. No. 6. Elevier. Minitry of Energy (1996) Sedimentology and ediment meaurement of the Dez dam, Tehran Reearch and Study Center of Water Reource, 86 P. Moaedi A (1998) Hydrological izing of edimenting reervoir ytem for irrigation and water upply. Ph.D. Thei. Technical univerity of Budapet. Hungary, 101 P. 407