CHapter 2 (PfiysicaC (Bac^rouncC CHAPTER 2 PHYSICAL BACKGROUND
The complexity is the norm in physical system and human induced changes on land and water invariably produce environmental feed back system. The area under investigations is a classic example of the above two concepts. While generating the database it has been decided to collect detail information on factors that shape the hydrogeological regime and that would help in giving solutions to the problems. These factors include climate, geomorphology, geology and their components / variables. It is believed that the overlapping the data of various kinds would help in understanding the intricacies of physical system, pinpointing causes of the problems and thereby framing suitable plan for solving the problems. The description of regional setting and data for Eyvanekey basin is outlined below.
Part I: Regional Setting of Alborz Mountain Range
Climate: Climatically the region is influenced by different air masses such as: I -Mediterranean mass from western part of Iran II -Arid and humid Siberian mass from north-west and north of Iran, and III- Arid tropical mass from central desert of Iran. The front originating from Siberia in northern part enters Iran and after collision with the Alborz mountain chain, looses its humidity in the form of rain and snow fall, and then reaches Eyvanekey basin. Therefore, vast variation in climate between the northern flank of the Alborz mountains and southern part can be observed.
10 The broad characteristics of the climatic components of south central Alborz mountain range are as follow (Jamab Consulting Engineers Company, 1998) o Min and max average monthly temperature -14 Cto39 C
Min and max monthly humidity 26-67 % Average annual humidity 41 % Annual rainfall variation 100 to 750 mm Average annual evaporation 2050 mm/year Min and max average wind speed 1.9-2.8 m/s Sunshine duration : 2957 hrs
Topography: There is a noticeable altitude difference in the southern Alborz mountain range from North to South, the highest point being Kholeno peak with 4375 m elevation and the lowest at 927 m. There are several perennial rivers generally running from north to south direction; the most important amongst them being Damavand river, Jajroud river, Haraz river and Karaj river that are the main sources of Tehran domestic water supply.
Geology: The Alborz mountain range is a part of the Alpine Himalayan mountain chain having E - W trend and is formed during late phase of alpine orogeny. Its shape is like a compound anticlinal structure. From the tectonic and stratigraphical point of view, the Alborz mountain range can be divided into three zones: - Western Alborz and Azarbayjan, - Central Alborz, and - Eastern Alborz. The central part of Alborz is divided into two zones as: North central Alborz and south central Alborz . 11 N D
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Skale.s3MSiMe*n< ( ^ 5 - -^iU -*■ J L . h*% iw f n z u H FOKMAIXJN Af«u Afcan) •.* I n n t O K (LAR LIMESTONE) ( JL. 1 ji*i JL* ^ ' J L - liK ^ a a e .M l -.a fM K a k b c v « « iO A l MTHAI FOAMATIOK) flwk * i % e * w ; <»W *Miwt , y . J — JiiU Bsuh u JL t S«iM?iHAKFORMATM)S [)<*•* wd fc*ei*«* L in r> M « . p iift; «M«» i n t i i tRUTEII K W M A TlO r^) i 4!,, -;U) juiJL. OXHniDFOMlATKiro t ^ s i— *-.U UmoM k Lm o «d«c.ihilr a«i«MtfAne*iUi^ Ba»k (.I:»fDFOtM .\TlOS (nnh«t«Wi]i'tMMc(MII AMWMAnOM r « i l t t a M UN SAKf>STnKF) t o/< X- *-U) 'ft - ^..^U ShakaMliMhMKOAKH.'MOItMATIlA) rr:aipK tjl .^jLSi .rc uA 1.X- l-.Jr- Skik. in d M w . Johxitfe ind im r4c« (H AJltT FORM AT10N) S 3 *ji_) ji^JL., —y>» -X- ' O lte ie . ifafc <90LTAN1EH DOU>Mnt Julc « IjU- ^ I v>U- I K.fk*k4irf4okxaitt(BAYANDOR a«J KAHAR FORM'SfK>V»’^ , -JL.*_u P ig ^ .l: RBgional stratigrapfaic cohmm 12 A variety of rocks belonging to Precambrian to recent period are present in the region (Fig. 2.1). The main tectonic activity in south central Alborz mountain o o range is Mosha reverse Fault trending E-W (with 35 to 70 dip) towards North ( G.S.I, 1996). South central Alborz is separated from central Iran region by Atari (Semnan) fault. There are many springs in the region discharging from few to hundreds of 1/s, water. Part I I : Eyvanekey Basin Climate: The data from eleven hydrometeorological stations located in Eyvanekey basin and adjacent areas was collected. The specifications and locations of these stations are incorporated in Table 2.1 and Fig. 2.2 respectively. The data of temperature are presented in Table. 2.2 and illustrated in Fig 2.3. The data of precipitation is incorporated in Table 2.3 and illustrated in Figs 2.4, 2.5 and 2.6, Figs 2.7 and 2.8 show the plots of the data in Emberger and Demarton’s classificatory system. The data of relative humidity and evaporation are incorporated in Tables 2.4 and 2.5 and illustrated in Figs. 2.9 and 2.10 respectively. Temperature: In order to study the temperature in the mountainous region of Eyvanekey basin, minimum and maximum temperature from Kilan meteorological station is recorded, and mean maximum, mean daily, mean minimum, minimum constant and maximum constant are calculated and presented in Table 2.2. o The mean temperature of the basin is 9.4 C. The coldest month with minimum o o constant o f-19.5 C in January and hottest month with maximum constant of 33.9 C in June (Fig .2.3). 13 Features of Stat tion Row Name of Year of Type of Station Establishment Station Longitude Latitude Elevation 1 Saeed Abad 52-22 35-38 2 1 0 0 1981 Rain Gauge 2 Hoomand ab sard 52-05 35-39 1800 1962 Climatology 3 Cheshmeh ala 52-04 35-45 2170 1981 Rain Gauge 4 Meraa 52-01 35-39 1740 1981 Rain Gauge 5 Bone Kuh 52-25 35-18 1040 1947 Rain Gauge 6 Eyvanekey 52-04 35-20 1050 1981 Rain Gauge 7 Kilan 52-10 35-33 1580 1967 Climatology 8 Hamamak 51-46 35-52 1150 1981 Rain Gauge 9 Chandab 53-04 35-41 1150 1975 Rain Gauge 1 0 Yahr Kahnak 52-29 35-41 2 2 0 0 1967 Rain Gauge 1 1 Javad abad 51-41 35-13 880 1968 Evaporimeter Table 2.1 Specifications of meteorological stations 14 - 5 0 ’ But tmn UYiD iBU} -10’ L e g e n d ■ City Road • Village — Plain Boundary —» Perennial R. Basin Boundary y taari ^ 1 Hydrometeorological Station -35-00' 40' 50 ’ 52-00’ 10’ 20 ’ _____L_ _1_ I _L_ Fig.2.2 : Location o f hydrometeorological stations in and around Eyvanekey basin. 15 U n it: O' Absolute of Absolute of Month MEAN MAX MEAN DAILY MEAN MIN Max. Min. Jan 2 . 6 -3.2 -9 7.9 -19.5 Feb 3.2 -2.5 -8 . 1 11.9 -18.4 Mar 8 . 1 2.3 -3.5 17.8 - 1 1 . 6 Apr. 14.6 8 1.4 24.5 -2.5 May 20.4 1 2 . 8 5.2 28.4 1 . 1 Jun 28.8 19.2 9.6 33.9 6 July 31.2 2 2 . 8 14.4 32.4 9.6 Aug. 30.2 21.9 13.6 30.8 8.5 Sept. 23.1 16.3 9.4 28.7 3.8 Oct. 18.5 11.5 4.4 26.4 -3 Nov. 10.4 4.5 -1.5 2 0 -7.6 Dec. 4.4 -0 . 8 - 6 14.4 -18.8 Year 16.3 9.4 2.5 33.9 -19.5 Table 2.2 Data of temperature from Kilan metereological station (1967- 1999). 16 o O> ON O o I r-I VO ON C _c D c _o *u.s >» 93 > 3 2 u Q. a. < S (D e o fo ri LL(1) C 05 .0 3dniVy3dlAI3i 17 Precipitation: Precipitation in arid areas is altogether low and temporally and spatially unevenly distributed. The largest part of it is consumed by evaporation before it has the opportunity to runoff and contributes to the groundwater recharge. In dry climate the rate of evaporation is greater than the rate of water runoff (Vierhuff, 1999). Table 2.3 shows the maximum rainfall equal to 80.7 mm in month of March in Cheshmeh ala station, while the minimum rainfall equals to 0.2 mm in the month of September in Javadabad station. On the basis of precipitation data from above stations the average yearly Isoheyt map of the Eyvanekey basin is prepared (Fig. 2.5). The average amiual rainfall in Eyvanekey basin varies from 100 mm in the southern part of the plain to more than 350 mm in the northern part of the basin. The average annual precipitation of Eyvanekey basin is 225 mm. The average annual rainfall, of the Eyvanekey plain is 133 mm. Table 2.6 represents the average monthly rainfall data from Eyvanekey rain gauge during the years 1967 to 1999. The classifications suggested by Emberger, De Marton and UNESCO (1979) are used to ascertain the climatic type of the study area. Emberger Coefficient was obtained using following formula : 2000 P Q2= ---- Q2= Emberger coefficient P = Average annual precipitation (mm) o M= Mean maximum temperature in hottest month ( C) K= 273.2(Coefficient of conversion of centigrade to Kelvin) o m= Mean minimum temperature in coldest month ( C) 18 u 00 00 m 00 O vq vq i n C\ Tt; t-^ vq ON i n o CN o q> r n r n VO 'O vd (N in O^ r n i n d Q m i n m (N CN »—H CN i n a l> (N ON ON r n m OO m vq (N q CN m vq MI) (N rn 00 iri ON (N K d i> vd 00 m m r o m vd (N m (N m o\ m ON vq os « r - r n OS lO r - (N VO 00 rnr-;CN rj vq i n g - lO m o (N r " (N m O j vq r n VO O) (N i n ON U VO (N U «N vd vd d a< o< ON vd r n CN r ^ i n i n (N rn m i n a 'O oo 00 ON (N ,, r n (N 00 (N VO q & VO e VO r<-i i n 00 i n (N d vd 00 vd m o < rl- VO m CN m m VO S o3 t n 1 r ' m m ON in Ov o «s ff) «D r- OO ON o l-H a: 1-H 19 % % \ o^ % Os 1^o\ r-I so ON VI s o ••hrf aM « M)V S :q Ml o= 1 2 •4-^ C3 c % C/^ '\ .2 .« % b.es "« s %. e c < r4 si) ’£ \ h /) A. % A. (uiui)|[i3juiB'y 20 -50’ TAAfi.LAXE BUT IBin • UViD iBiO - 1 0 ' L e g e n d - ■ City — ---- Road • VUlBfe ------Plain BoundflJ^ —* PerenniBl R. Basin Boundary -35-00 ■ 40 ‘ 50’ 52-00' 10 ' 2 0 ’ 1 1 1 1 1 1 Fig.2.5.: Average yearly isohyet map for rainfall of Eyvanekey basin. 21 (1) Q CO CD o\ o a\ N M;: O c^ var ' o \ SSKSBsi; Q. cvi 0 ) U) aW) i i i i i i i i i c « < b » _ c 0> CM CNI a es U CN S ro o ■ o 04 1 c ?>% (N Ic in oG B V M « r- ; > VO fS h - -D ei in 0) ro CO LOro roo CNJLO (ujoi) iiejuje^ 22 As already mentioned, in Eyvanelcey basin, the average maximum temperature o in hottest month and minimum temperature in coldest month are 31.2 and -9 C respectively and average annual precipitation is 225 mm. Therefore, 2000 X 225 Q 2= ------=19.7 (31.2+ 273.2)^-(-9+ 273.2) 2 According to Emberger’s climatical classification, the climate in Eyvanekey basin lies in cold dry region. (Fig.2.7 ). The average annual precipitation of Eyvanekey basin is 225 mm and mean annual o temperature is 9.4 C. The plot of these parameters falls in semi-day climate of De Marton’s diagram (Fig.2.8 ). Relative Humidity: The variation of relative humidity is calculated from the data recorded by dry and wet thermometer in Kilan meteorological station. The maximum relative humidity recorded in the month of February is 69% and the minimum relative humidity in month of July is 42.8 %, (Table 2.4, fig. 2.9). Month Jan Feb Mar Apr May Jun Jul Aug Sep Ocl Nov Dec Annual Average 68 69 68.1 58.7 53.6 45.1 42.8 42.9 48.3 56 57.2 66.8 56.4 (%) Table 2.4 : Data of relative humidity from Kilan metereological station (1967-1999) Evaporation: The data of mean monthly evaporation from Javadabad evaporimeter station, which is nearest station to the Eyvanekey basin, for the years 1969 to 1998 is given in Table 2.5 and fig. 2.10. The average annual evaporation is 2469 mm and maximum monthly evaporation equals to 446 mm in the month of July. The minimum monthly evaporation is 33 mm in the month of February. 23 a: >-S5 LU I H Ou_ X H- Z O h- LUCO Q -J fi O o .2 z o trUJ s 3 H < "3.2 LU Q. « E "y Sf s • • r- r4 S S § !? S S g ( 3D ) luapii^aoo s,ja6 jaqLU3 L=55 ^=35 L=28 U=24 L=20 Mean Annual Temperature ("C) Fig . 2.8 : Deinarton's Climatic Classification. 25 0)o CD CD Q g in CN o ^ CD -G ID O ov I t - so On CO : 0)Q. C CO CO *iS 5/5 C O) JZ CM =J < 2 E I « CNI 3 «?j- -3 s/) ^ J= T3 LD I f 3 JS O) J2 CO (D " 3 LO u B © Q. CO E lO < c 0 ^ CO C\ CD < S ei) o> n CD 0 ) CO c CD m o o o o o o o 00 r-- CD IT) CO CM 26 Unit (mm) Row Year Jan Feb Mar Apr May Jun July Aug Sept Oct Nov Dec Annual 1 1969 29.6 28.9 20 71.4 282.8 393.4 412.3 416.2 299.1 227.6 102.9 64.9 2349 2 1970 41 9 35.3 42.9 292 310.9 466.7 459.9 453.9 357.6 246.3 150.3 10.5 2868 3 1971 40 22 41.8 211.2 327 440.1 473.1 441.1 367 208.5 116.4 72.5 2761 4 1972 30 15.8 30 104.4 210.7 352.2 310 368.1 310.9 235.4 16.8 50.4 2035 5 1973 43 20 38.9 207.6 372.8 485.5 582.8 613.6 435,3 301.8 135.3 50.1 3287 6 1974 14.3 10 22 74.8 209.3 480.2 670.8 638 430.1 304.4 119.8 55 3029 7 1975 29.2 156 30 101.1 178.2 363.1 667.2 617 379.2 200 142.7 42,9 2766 8 1976 34.3 17.3 34.6 171.7 242.3 380.1 493.5 486.1 359.3 212.9 98.3 36.2 2567 9 1977 17.9 90 66.9 208.5 293.8 390 510.8 492.7 350.4 237.1 104.5 58,8 2821 10 1978 31.7 23 49.9 231.1 303.4 431.4 451,3 473.8 445.2 226.9 128 52.9 2849 11 1979 49.7 44 106.5 215.8 275 370 462.9 409.7 322.4 207.2 119.7 65.7 2649 12 1980 21.7 19.6 97.4 221.7 267.8 360.3 389 429.8 336,5 238.8 102.2 58.6 2543 13 1981 11.2 14 67.8 222.5 311.5 373.5 484.8 429.4 357,8 194.8 127.9 93.5 2689 14 1982 54.4 20.3 39.4 169 204.5 238.8 427.8 442.7 317.5 158 9 72.6 27.3 2173 15 1983 20 10 24.3 147 236.7 343.6 364.5 398 9 347.4 220.8 144.1 63.4 2321 16 1984 30 10 40 201,8 215.4 409.1 477.4 411.2 390 1 230 108.2 23.5 2547 17 1985 45 40 60 237.3 294.1 398.8 441.4 443.4 349 269.4 161.5 38.4 2778 18 1986 33 23 73.3 129.6 204.9 347.8 534.7 461.5 296.1 164.2 68.1 29.5 2366 19 1987 44.3 43.4 60.3 188.5 317.4 368.8 399.8 394,8 291.9 158.8 61.4 44.8 2374 20 1988 32.4 39.8 84.8 170.7 228.9 383.6 436.3 405.3 272.4 165.5 108.3 53.8 2382 21 1989 23.8 13 12.9 179 223.3 357.4 427.2 399.4 311.8 191.3 116.9 55.5 2312 22 1990 24.5 25.3 35.6 152.6 303.3 386.5 4142 430.3 34 2 9 193 108.5 64.9 2482 23 1991 16.4 52 74.6 166.9 262.4 377.9 410 1 400.6 301 175.1 114 45.5 2397 24 1992 60 50 100 167.2 181.6 280 9 413.3 351.4 268.9 170 103.8 42.8 2190 25 1993 33 1 73 62.9 206.9 216.6 329.2 408.9 365,1 3II.9 172.1 100 44 2324 26 1994 20 70 104.4 160.6 215.9 338.7 398.6 363 282.9 157.1 78 32 8 2222 27 1995 3 9 3 72 89.5 168.2 204.3 284.1 385.1 360.8 263.9 158.1 99.5 37.2 2162 28 1996 24.1 30 29.3 114.7 172.4 302 348.2 321.1 271.4 156.8 101.5 48.5 1920 29 1997 56 15.4 46.7 156.1 255.1 335.4 360.2 340.4 256 183.5 44 13 2062 30 1998 73.9 53 4.9 167.2 220 303 363 1 309.8 254.3 39.6 25.6 40 1854 Average 34.16 33.19 53.05 173.90 251.4 369.1 446 429 329.3 200.20 102.7 47.23 2469 Max 73.9 90 106.5 292 372.8 485.5 670.8 638 445.2 304.4 161.5 93.5 3287 1 Min 11.2 10 4.9 71.4 172.4 238.8 310 309.8 254.3 39.6 16.8 10.5 1854 Table 2.5: Data of mean monthly and annual Evaporation from Javadabad station 1969 - 1998. 27 \ \ \ % 00 % ON o\ y-i % asI asVO e o OS % *■> tsV i -a ft % XI « \ ■a0! > \ ez \ 1 e \ £ _o % >- 2 o a % ss es <£ o <5> 0> W) es 4)u > 'S- »N •M <5> Vx6> O 8 8 in8 o8 CM (uiiu) U0IJB40dBA3 28 Topography : As has been mentioned earlier, Eyvanekey basin is located on the southern flank of the Alborz mountain range and the northern part of central desert. There is a considerable elevation difference from north to south of the basin, the highest point located at Zarin mountain, being 3452 m. and the lowest point being 927 m. at the southern tip. Eyvanekey river originates from the eastern part of above mentioned mountain and generally bears a NE-Sw. This branch of the river is called Doab stream. Another branch originating from the western part of the Zarin mountain, called the Jamabrud river which after passing from Ab-Sard, Kilan and Saran villages, ultimately joins the Doab stream. (Fig 2.11) These two streams form the Koorak river. The main geological formation through which these streams flow are Karaj formation, Qom formation and Upper red formation. Another river called the Shoorab (meaning salt water) river; originates from tertiary evaporite formation and meets the Koorak river. As the name of river in the lower reaches. The river course after the confluence of Shoorab with Koorak river is called as zamrud or Namarak river. This segment possess a low slope, passes through conglomerates and ultimately enters the Eyvanekey plain (Photo 2.1). The total catchment area of this river is about 1035 KM. Other than the above mentioned rivers there are three rivers having N-S trend namely the Chandab, Sangab and Karoos, enter the Eyvanekey plain and ultimately meet the Eyvanekey river near the closure of the entire basin (Photo 2.2). Total area of the Eyvanekey basin is 1431 sq. km. while the periphery is 179.5 km. The length of the Eyvanekey river up to the entry into the plain is 72 km and average slope is 4.7 % (Reyah consuhing Engineers, 1996). Drainage pattern: The spatial arrangement of a river and its tributary streams in a drainage network is referred to as the drainage pattern. The drainage patterns 29 L e g e n d ■ city ‘V® Elevation • Yillase V— Plain Boundary -35-ID' ,5^ • River Km 20 — ■— Road Fig.2.11 iPhysiographical regions and major rievers of Eyvanekey basin. 30 Fig. 2.12 : Map showing drainage pattern of EyVanekey basin. 31 are controlled by lithology, geological structure and topography. As seen from Fig. 2.12 the drainage pattern in Eyvanekey basin is dendritic to sub dendnite type. This is particularly dominant along the periphery. The parallel to sub parallel disposition of middle order streams is also seen in the central part of the basin. At few places lower order streams meet the higher order one at right angles. Morphometric Analysis: The quantitative data for Eyvanekey basin was obtained by conducting morphometric analysis using toposheets. The quantitative aspects of the following parameters were studied: 1. Stream order number 2. Bifurcation ratios 3. Hypsometric analysis The data of morphometric analysis is incorporated in Tables 2.6, 2.7 a, 2.7 b and Figs 2.13a, 2.13b. The details of these aspects are described below; Stream Order Number:The streams in Eyvanekey basin are numbered using the procedure suggested by Horton (1945) Jstraheler (1964). Stream No. of streams Bifurcation ratio order jst 542 - 2 nd 123 4.4 3 rd 19 6.47 4>h 4 4.75 S*” 1 4 Table 2.6; Stream order, number of streams and Bifurcation ratios 32 Bifurcation Ratio (Rb): It is the number of stream segments of a given order (Nu) to the number of segments of the next higher order (Nu+1). Bifurcation ratio can be expressed as R b = N u /N u + l The data of bifurcation ratio obtained for different order stream segments are incorporated in Table 2.6. According to Strahler (1964), the weighted mean bifurcation ratio is more meaningful in ascertaining the structural control over the drainage. The values of bifurcation ratio varies from 4 to 6.47. The values higher than 5 are indicative of a strong structural control over the drainage. Hypsometric Analysis: Hypsometric or Area-altitude analysis was carried out to obtain the relationship of the horizontal cross- sectional drainage-basin area to the elevation. The hypsometric integral values throw the light on the stage of the development of the basin. The hypsometric analysis of the Eyvanekey basin is carried out and the data is presented in Tables 2.7 (a) and 2.7 (b ). Contour Area (km2) bet. Relative area Relative height intervals (m) Contours (a/A) (h/H ) 927-1000 194.6 0.136 0.290 1000-1500 508.0 0.354 0.435 1500-2000 384.9 0.269 0.579 2000-2500 284.8 0.198 0.742 2500-3000 51.5 0.036 0.869 3000-3452 7.2 0.005 1 . 0 Total 1431 - -+ Table 2.7 (a): Hypsometric analysis data of Eyvanekey basin (Integral) From Fig.2.13 (a) it is evident that the hypsometric integral is less than 0.5 and therefore the basin has reached the mature stage of development. The attitude of the basin is shown in Fig. 2.13 (b). 33 5 *S X > "3 0 0,2 0.4 0.6 0.8 Relative Area (a/A) Fig.2.13(a):Hypsometric Cui*ve of Eyvanekey Basin. 34 Altitude above Area between Area above each Percentage of area msl. (m) contours(km^) contour(km^) above each contour 927 1431 100 194.6 1000 1000 1236.4 86.4 508 1500 1500 728.4 50.9 384.9 2000 2000 343.5 24 284.8 2500 2500 58.7 4.1 551.5 3000 3000 7.2 0.5 7.2 3452 Total 1431 -- Table 2.7(b): Hypsometric analysis data (Percentage). 35 o o el X? a « o u t s o «s • ■MUD Ui O O o o O 36 Geology: In the southern part of central Alborz, there are alternative deposits of Paleozoic and Mesozoic formations. The litho stratigraphic and geological column is shown in Fig. 2.1. The regional lithostratigraphic sequence of the Eyvanekey basin includes Precambrian to Quaternary formations. The geological map and cross section along C-C‘ is incorporated in Fig. 2.14 and 2.15. A brief description of these formation is given below. Precambrian Formations : These formation are represented by Bayandor and Kahar Formation (PG Br/Kh), Soltanieh formation (PCS), Barout formation (PGBt) and Zaigon formation (PeZ). Bayandor and Kahar Formation (P€ Br/Kh) : The oldest rocks in the study area belong to the Kahar formation which outcrops on Ayneverzan. The type section of Kahar formation is seen in west of Karaj river comprising mainly of sandy and micaceous shales of green and dark colour, including thin intercalations of quartzite and dolomotic limestones. Above the Kahar formation, prominent outcrop of the Bayander formation, of shales and sandstones is present. Soltanieh Formation (PCS) : The Kahar and Bayander formation are overlain by Soltanieh formation having 1200m. thickness. This has undergone folding And well developed anticline is seen at Aynevarzan. It consist of shales and sandstones. Barout formation (P€Bt) : This formation shows an extensive outcrop on southern flank of Aynevarzan mountain and is composed of shale and sandstones. Zaigon Formation (P€Z) : The Zaigon formation constituted of quartzite overlies the upper Cambrian layer. It is represented by shales and sandstones. 37 Fig^. 14 Geological map of Eyvanekey basin (After Geological S urv^ of ban) 38 ^ r ^ E ^ c » =c ' ■ ‘ ■ ‘ ,^- 1 & 3 , - ^ c ? - f r y . - ^ / . / ^•1* • • ^ « v ’ * A V /( 1 1 i // 1 i x * • ♦ * g *3u 'S> o ■S T 39 Paleozoic Formations : The Palaeozoic formations occupy the northern periphery of Eyvanekey basin. It consists of limestone, dolomite, dolomitic limestone, slate, shale and sandstone. Lalon Formation (Lower Cambrian) (CL): This formation is composed mainly of sandstone with ripple marks and cross bedding. Lalon formation occupy considerable area on Aynevarzan anticline and made up of quartzitic sandstones. Mila Formation (Middle Cambrian-Ordovician) (CM): A type section of this formation is divided into five units and is composed of dark dolomite, limestone with trilobites fossils, sandstone, siltstone and shale. It is exposed on northern flank of Aynevarzan mountain and north of Mosha fault near Mobarak - abad and Imamzadeh Hashem ghats. ^ T h S8^09 Geirud Formation (Upper Devonian) (D-Cg ): This formation which constitutes a total thickness of 750 m. is made up of sandstones, shales, organic limestones, marly limestons, quartzites and green basalts . Jairud formation in the study area occurring on Aynevarzan Gardehlansh mountains is composed mainly of limestone and overlies the top quartzite of Lalon formation. Mobarak formation (Lower Carboniferous) (C): This formation attains a maximum thickness of 450 m and is made up of dark and grey limestones, marls , marly limestones with remains of fossils. Dornd Formation (Lower Permian) (PD): This formation typically consists of red sandstones, siltstones and mudstones with thin layers of limestones. In Aynevarzan and Delichai this formation with less thickness lies Linconformably on the Mobarak formation and is made up of sandstones and shales with intercalations of limestones containing remains of fossils. 40 Ruteh Formation (Upper Permian) (PR): This formation constitutes a total thickness of 300 m and is composed of limestones containing coral fossils and brachiopods; which are characteristic of middle and upper permian. In Aynevarzan anticline this formation is disposed as cliffs of limestone of dark grey and black colour with fossil remains. Mesozoic Formation : Mesozoic formations generally lie conformably above the rocks of Palaeozoic age including formations such as Elik, Shemshak (Jurassic), Delichai (Jurassic), Lar (Jurassic) and Tizkuh (cretaceous) with 4000-5000 m thickness. Elika Formation ( Triassic ) ( R‘‘e , R‘e ) ' This possesses a total thickness of 300 m It is made up of pink - yellow limestones which contains fossil remains. In the study area, Elika formtion occurs on the northern flank of Aynevarzan anticline with thin layers of gypsum. Shemshak Formation (Lower Jurassic) (Js,J^) : Rocks of this formation have extensive outcrops and rest generally unconformably on Permian or Triassic limestones. Typically, they consist of greenish - grey to grey shaly mudstones and sandstones with thin coal seams, plant remains and bivalves. Dalichai Formation ( Middle Jurassic ) (JD) : Rocks of this formation are mainly made up of marly limestones, marls and shales, containing ammonites. In most of the places in the Alborz mountain range there is a stratigraphical gap of Dalichai formation due to highly erodable lithology and hence usually the Lar formation overlies the Shemshak formation. Lar Formation (Upper Jurassic) (JL) : The total thickness of this formation is about 2500 m Rocks of the Lar formation are made up principally of 41 pure and dolomitic limestones. Characteristically, they include layered and nodular chert of white or violet colour. Lar limestones are light grey and yellow in colour with highly compact and thin bedded layers containing of ammonites. Tizkuh Formation ( Lower cretaceous ) (K^ t) •' This formation exhibit a total thickness of about 250 m. and are composed of fine grained Orbitolinid limestones. This formation occupies a minor area in Eyvanekey basin. Cainozoic Formations : Tertiary rocks show greatest areal extent in the study area and is divided into two parts namely: Palaeogene and Neogene, Palaeogene rocks consist of mostly lavas, tuffs and agglomerates and are represented by Lower red formation, Qom formation (OM) and Upper red formation. Neogenes are represented by oligocene, miocene (Qm) and lower pliocene formations and are made up of sandstones, gypsiferous mudstones (M3), shales (M), evaporites and conglomerates of Hezardarreh (m.) and Kahrizak (Pl-Q), with extensive areas in north and south parts of Eyvanekey basin. Fajan Formation (Eocene) (€f): The type section of Fajan formation with 1500m. thickness is made mainly of conglomerates and is developed in the middle part of Eyvanekey basin. Ziyarat Formation (€z)‘- This formation is observed with very small areal extent near Saran village and is composed of marl, marly limestones and gypsum lenses at the base of the formation. Karaj Formation .-This formation covers a large part of the study area. It consists of various volcanic rocks, tuffaceous sediments, carbonaceous and siliceous shales . This formation is mostly characterised by its peculiar green colour. The Karaj formation constitutes a total thickness of about 4000 m 42 Lower red Formation (Oligocene): The formation unconformably overlies Eocene volcanics and conformably underlies the Miocene Qom formation. It exhibits a maximum thickness of 1000 m and contains Andesites , dacites , tuffs , and agglomerates (Oi'^) in the lower part and conglomerates , sandstones , shales and marls in the upper part which are generally red in colour. In the eastern and southern part of Eyvanekey plain this formation is composed mainly of gypsum, salts and volcanic rocks (Photo 2.5). Qom Formation (Oligocene) (0-M): The most characteristic rocks of this formation are light coloured, white to yellow and pink limestones, green grey marls, halites, gypsum layers and sandstones. Tuff beds are locally interbedded in the sediments, but a great thickness of green tuffs and volcanic rocks accompanies the sediments of the Qom formation. Upper Red Formation (Miocene): This formation overlies the Qom formation and is composed mainly of red marls, sandstones, mudstones, evaporites (salt and gypsum) and shales with a similar lithology of the Lower red formation. In the south and southeast of Eyvanekey basin, upper red formation is represented with large areal extent and ranges in thickness from 3500 to 6000 m. Due to the presence of gypsum, marls and halites in this formation to large areal extent and development of these rocks in Eyvanekey basin, quality of surface and ground water is considerably affected and influenced negatively. Quaternary Formations : These are mainly composed of sedimentary continental deposits and volcanics. They are divided into four different units namely: terraces (Qt), alluviums (Qal), travertines and young basaltic lavas (Oi'^). Hezardarreli Formation (Miopliocene ) or A series (M - pi ): Lithologically this formation is composed of homogenous conglomerates containing pebbles, gravels , and sands either with sandy, silty , siliceous or marly 43 matrix along with lenses of clays and sands. The size of gravel varies between 10-30 cm; are light grey in colour and not well rounded. About 90% of the source is from Karaj formation; which is transported and remaining 10% from other formations. Due to lateral compressions they are folded and faulted in NS or NE- SW directions and unconformably underlined by younger alluvium. In Eyvanekey basin they are conformably overlying the Upper red formation with a gradual border and well developed in a large part of Kilan mountains. Due to presence of clay and compact sandy matrix, this formation is almost impermeable (Photo 2.4). Kahrizak Formation (Pliopliostocene ) or B series (PL - Q): This formation (B series) unconformably overlies the A series which is made up of conglomerates containing grains of pebbles, gravels, sands, silts, clays and rarely rock fragments with a few meters in diameter; which constitutes a total thickness of 60-70 m. It is darker in colour compared to A series with dip varying in between 5^-10°. Kahrizak formation with relatively low permeability doesn’t constitute an important source of water potential. This formation in the related study area occurs in Eyvanekey mountain (north and east of - Eyvanekey City) which contains conglomerates with sandy and clayey matrix with low degree compaction. In the north of Eyvanekey and lower most part of the basin deposition of silt layers is taken place on the B series (Photo 2.3). Tehran Alluvial Formation (Holocene) or C series (Q): This series is composed of alluvial fans and sediments which are formed by erosion of Hezardarreh (A series) and Kahrizak (B series) formations carried by major rivers and flood currents. These fluvial sediments are composed of grains of gravels, sands, pebbles, silts with sandy and clayey matrix. The grains of this formation are large in the northern part of the alluvial fan with very little clay content and gradually changes to finer and smaller size towards the southern part of the basin containing more silts and clays. 44 The samples collected from wells dug in the north and central part of the plain shows that 90 to 95 % of the grains are made up of gravel and pebbles and 5 to 10 % of clays and sands. Due to the presence of numerous joints fractures and intercormection between these joints, favourable and considerable number of aquifers and ground and water resources are formed in C series. Recent Alluvial Deposits or ( D SERIES ) .'These are the most recent deposits which are transported and deposited by fluvial action along the banks of rivers at foot hills and alluvial fan where the rivers enter to the plains. These deposits contain pebbles, gravels and some amount of clays. D series at Eyvanekey river bed in the northern side of the Eyvanekey city are widely spread but possess very low thickness(Photo 2.8). Eyvanekey Plain : Eyvanekey plain consists of a syncline with NW - SE axis, which is filled by sediments derived by erosion of rocks. These sediments belongs to Hezardareh (A series) and Kahrizak (B series) formations. Eyvanekey plain can be divided into two distinct parts : A) Northern part of alluvial fan composed of coarse grained pebbles, gravels, sands and in less amounts clays. These sediments have been derived from igneous rocks, tuffs, sandstones, limestones, and marls present in the upstream area. B) Southern part of the plain composed of fine grained clay, silt and sand with a large amount of salt and gypsum deposits and surfacial salt crystalisation (Photos 2.6 and 2.7). The maximum thickness of alluvial deposits in the northern part of alluvial fan is more than 250 m and in the lowermost part of the plain it reduces considerably. The depth to bed rock varies from place to place. It is composed of A series and B series in the northern part of the plain and of Tertiary deposits in the southern part. In the east and south-east of the plain, the bed rock consists of gypsum and salt deposits. 45 Tectonics : The major part of the study area is located on the southern central Alborz mountain range and a smaller part occurs in the central Iran. Eyvanekey basin consists of following six tectonic units (Fig.2.16 ) • Mosha - Fasham thrust fault • Southern flank of Sarbandan anticline • Ab- sard thrust fault • Highly folded zone • Gentle anticlines and synclines foldings. • Desert ( Kavir) thrust fault ( Pishwa fault) Mosha -Fasham Thrust Fault : This fault on the southern flank of central Allborz, with E - W trend, passing from the north of the capital Tehran, is of great importance.lt is a overthrust fault with 400 km length and is one of the active Quaternary faults. Sarbandan Anticlinarium : The southern flank of this anticline consists of older formations, which shows an acute dip bedding and has been responsible for major mountains of the study area. AB - Sard Thrust Fault: This fault 605 Km in length has a NE - SE trend and dips towards SE. Highly Folded Zone : This zone belongs to Tertiary deposits, which consists mostly of volcanic formations. There are a number of faults in different directions, but generally trending towards NW- SE direction . Gentle Anticlines and Synclines : This zone consists of upper Tertiary formations which show a very gentle dips. 46 FigJ2.16: Tectonic nup of Eyvaneikey basin and adjacent areas 4 7 Desert Thrust Fault (Pishwa Fault): This fault is located adjacent to desert, the length of it is about 15 Km. It has NW - SE trend. In addition to the above mentioned faults, there are many other minor faults in different directions. They generally trend in N - S and NE - SE directions (GSI, 1996). Interpretation and Discussion : From the foregoing description it can be seen that the study area constitutes a part of southern-Alborz mountain range and the northern part of the central desert. The climatic data collected from eleven meteorological stations o o indicate that there is a wide variation in diurnal temperature from -19.5 C to 33.9 C.(Table 2.2). The rainfall decreases from north to south from 350 mm to 100 mm. According to Emberger’s classification the climate of Eyvanekey basin resembles cold dry region whereas according to De-martonns classification, it is semi dry climate (Figs 2.6 and 2.7). The relative humidity values range from 42 % to 69 %.The average annual evaporation is very high up to 2469 mm . According to UNESCO (1979) and classification based on the ratio between average annual precipitation (P) and annual reference evaporation (Eo), the climates can be grouped into five classes as follows: Hyper-arid = P/Eo<0.03 Arid = 0.03 0.75 The values of this ratio obtained in the present study for 100 m and 350 mm rainfall respectively are 0.04 to 0.14. indicating that the area falls in the category of arid climate. There is a considerable elevation difference from north to south the highest and lowest points being 3452 m and 927 m. Several rivers meet 48 Eyvanekey river at the lower reaches of the study area (Fig 2.1). These rivers e.g. Chandab, Sangab, Karoos, Zamrud, and Koorak, initially flow almost parallel to each other. The drainage pattern as seen from the drainage map (Fig.2.12) indicates that though over view is of dendritic to sub-dendritic type , parallel to sub parallel and rectilinear disposition of lower and middle order streams can also be seen. Such type of heterogeneous drainage is the reflection of variation in lithology and structural control, such as folding, faulting and subsequent fracturing and jointing. The values of bifurcation ratio obtained in present study indicate that the ratio is above 5 in case of 2"‘* and order streams (Table 2.6). This higher value also substantiates the structural control (Strahler, 1964). The hypsometric data (Table 2.7 ; Fig 2.13) indicate that the basin has reached the mature stage of development. A variety of rock types belonging to Precambrian, Paleozoic, Mesosoic, Cenozoic and Quaternary ages are present in the study area (Fig 2.1) These mainly include the volcanic rocks such as andesites and sedimentary rocks such as limestones, marls, sandstones, tuffs, shales, clays, etc. Evaporite deposits including gypsum and halite are present in the form of beds, lenses and incrustations. These evaporites are dominantly seen in the southern part of the basin. These formations have undergone tectonic disturbances such as folding and faulting. While interpreting the hydrogeological regimes both in terms of quality and quantity of groundwater. Hydrogeologist should take into account this physical setup. The structurally disturbed strata and rock types are responsible for the development of drainage pattern. Further, weathering of rocks is intense due to physical and chemical processes. In such a terrain one can expect good quantity of recharging of water during rainy season. Recharging can also takes place during spring season due to snowfall in the mountains in the northern part of 49 the basin. The groundwater, if obstructed at the interface of pervious formation such as clay beds and bedrock, emerges in the form of springs. Several such springs are present in the study area. But they yield water for a short period and then either disappear or ooze water in the form of seepages. The climatic and lithological settings of the study area is also conducive for water rock interaction. Water when come in contact with soluble salts such as gypsum, halite, marl etc. can imbibe salinity. Thus one can expect a good amount but low quality waters in the Eyvenkey Plain. 50