ACTA CARSOLOGICA	31/2	4	93-103	LJUBLJANA 2002
COBISS: 1J
THE ROLE OF SARVAK FORMATION IN SUPPLYING POL-E DOKHTAR TOWN (IRAN) WITH DRINKING WATER*
VLOGA GEOLOŠKE FORMACIJE SARVAK ZA OSKRBO MESTA POL-E DOKHTAR (IRAN) S PITNO VODO
mohamad reza ahmadipour1
* The paper was presented at EVOKARST symposium (Postaja, September, 2002)
Lorestan University, KHORRAMABAD, P.O. Box 465, LORESTAN, I.R. OF IRAN
Prejeto / received: 4. 3. 2002
Izvleček	UDK: 628.1(55)
Mohamad Reza Ahmadipour: Vloga geološke formacije Sarvak za oskrbo mesta Pol-e Dokhtar (Iran) s pitno vodo
Formacija Sarvak je najbolj zakrasela formacija v skupini Bagestan, SZ od mesta Pol-e Dokhtar. Njeno južno krilo je zakraselo in najpomembnejše za talno vodo. Za oskrbo s pitno vodo mesta Pol-e Dokhtar, so bili izvrtani trije vodnjaki. Opravljen je bil crpalni (72 ur). Analize kisika-18 in devterija kažejo na meteorni izvor vode. Voda iz vodnjaka Wj ima minimalno, iz W3 pa maksimalno koncentracijo tricija, kar kaže na različen rezidencni čas, kemične analize pa, da gre za vode tipa Ca>Mg>Na in HCO3>SO4>Cl. Med samim vrtanjem so imeli vzorci vode relativno veliko količino NO3 (27 mg/l), ki se je, zaradi zavarovanja področja pred kmetijsko dejavnostjo, znižala. Mesto Pol-e Dokhtar, ki je imelo resne težave z oskrbo s pitno vodo še izpred časov islamske republike, teh zdaj nima več, zahvaljujoč predstavljeni raziskavi. Ključne besede: kraška hidrologija, kemizem kraške vode, pitna voda, Lorestan, Iran.
Abstract	UDC: 628.1(55)
Mohamad Reza Ahmadipour: The Role of Sarvak Formation in Supplying Pol-e Dokhtar Town (Iran) with Drinking Water
The Sarvak formation is the most karstified formation of the Bageston group, NW from town Pol-e Dokhtar. Its southern limb is karstified and the most important for the ground water. Three wells were drilled for supplying the drinking water to Pol-e Dokhtar. The pumping test (72 hours) was carried out. Analyses of oxygen-18 and deuterium indicated that the water is of meteoric origin. Water from the weU1 has the minimal and from the well3 maximal concentrations of tritium which indicate different residence time. Chemical analyses show that the water is of Ca>Mg>Na and HCO3>SO4>Cl type. During the drilling water samples had relatively high NO3 (27 mg/l), which was reduced due to the protection of the area from agricultural activities. Due to this study, the town of Pol-e Dokhtar, which was facing serious problem of drinking water since before the Islamic Republic of Iran, has been solved.
Key words: karst hydrology, karst water chemistry, drinking water, Lorestan, Iran.
INTRODUCTION
The Sarvak formation is the most karstified formation of the Sultan anticline. The anticline is situated in the village of Gol-Goll which is 14 km to the NW of Pol-e Dokhtar city. The mean annual rainfall is 482 mm and mean temperature is 27°C. The location of the study area is shown in Fig. 1.
REGIONAL GEOLOGY OF THE
AREA
The study area is part of the folded Zagros Zone. The general geology of the area includes the quaternary sediments (Q), Gachsaran (GS), Asmari Shahbazan (As-Sb), Kashkan (Kn), Talezang (Tz), Amiran (Am), Gurpi (Gu), Emamhasan (Em), Ham (H), Sarvak (Sv) and Garu (Ga) formations. The last tree formations are classified as the Bangeston group. Geological map of the area is presented in Fig. 2.
Fig. 1: Location of the study area.
Fig. 2: The geological map of the area.
Legend: Al - Alluvium; Gs - Gachsaran; As-Sb - Asmari-Shahbazan; Kn - Kashkan; Tz - Taleh Zang; Am - Amiran; Gu - Gurpi; Ehm - Emam Hasan Member; Il, Sv - Bangeston Group; Ga - Garu.
THE CARBONATE FORMATION OF SARVAK
The carbonate formation of Sarvak is a part of the Bageston group, which constitutes the Sultan Anticline. The sarvak formation with a thickness of 820 meters at the type section of Lorestan in Sefid Kuh (north-west of Khorram abad) is deposited in the southern margin of the Neotethys Ocean. The age of the formation is Albian-Turonian.
Sarvak is a thick and coarse-grained carbonate formation of the Sultan Anticline. The geological cross-section along the BB' of the geological map is shown in Fig. 3.
It is overlain and underlain by the thin fine-grained Ilam and the bituminous shaly formation of Garu formations respectively. Due to the tectonic activities, the rocks of the Bageston group have
been folded and faulted. The effect of tectonism is highty developed in the southern limb of Sarvak, which has been thrust over the Ilam formation. The shattering of the rocks (at the contact of Sarvak and Ilam) and the Z type folding on the southern limb of Ilam are indications of the intensity of tectonism (Figs. 4 and 5).
Fig. 3: Cross-Section along BB'.
Fig. 4: Scattering of the rocks at the contact of Sarvak and Ilam.
Fig. 5: The development of Z type folding along the southern limb of Ham.
DEVELOPMENT OF FRACTURES
In general the fractures related to the Sarvak formation are of shear and tensile type (Fig. 6), which has been developed on the southern limb of Sarvak. The tensile fracturing has an important role in karstification.
Fig. 6: Types of fracturing: (a) shear, (b) tensile.
Fig. 7: Development of karrens.
KARSTIC FEATURES
Due to the high intensity of tectonism and the action of dissolution, in the southern limb of sarvak karstic features such as karrens, dolines have been developed. The area is a typical karst in that surface drainage is lacking. Dolines and caves of the larger forms occur at the axes of the anticline. The dolines at the valley floor are circular in shape with different diameters. The karstic features are the main avenues for transmitting and storage of groundwater (Fig. 7).
WELLS
Based on the karstic features and the fractures (especially the tensile factures) in the southern limb of the Sarvak formation, three wells wit the total depth of 525 meters were drilled in order to supply the drinking water of the city of Pol-e Dokhtar with a population of more than 20,000 persons. The wells were drilled at a distance about 1 kilometer from each other. The situation of the wells is shown in the geological map of the area. Fig. 8 shows thle discharge of well (Wj).
The wells were pumped at a constant rate of 40 lit/s for 72 hours by the author. During the pumping test the wells did not show draw down. The calculated transmissivity for the first well (Wj) was 27417 m/day. The high transmissivity indicates the well-developed secondary fractures. At present the wells are being pumped to the city of Pol-e Dokhtar through a pipeline of 400 mm.
Fig. 8: Discharge of the well (Wj).
HYDROCHEMISTRY
In order to study the rock-water interaction, water samples from the wells were analyzed. The result of the chemical analyses of the samples during the pumping test is shown in the Table 1.
Table 1: Chemical analyses of the wells during drilling (mg/l).
Name Ca	Mg	Na	K	S04	HCO3 Cl	NO3	N02 EC	TDS TH	°C	PH
							pScm-1			
Wj 26.8	26.5	18.6	1.95	90.8	195.7 8.5	23	0.019 576	296 174.5	22	7.6
W2 27.8	27.9	26.6	1.95	142	159.2 8.1	27	0.013 660	350 184.5	22	7.5
W3 28.5	31	30.1	2.34	143	170 7.8	28	0.019 716	434 199.5	21	7.8
From the table it can be seen that the concentration of ions increases from W1 to W3. The type of water is Ca>Mg>Na, HCO3>SO4>Cl. The relatively high concentration of SO4 in the water samples can be due to the effect of the Gachsaran formation. The high concentration of NO3 in the
sample was known to be due to the agricultural activities, animal waste and human waste around wells. The concentration of NO3 due to the protection steps from the agricultural activities and the continuous pumping was considerably reduced (Table 2).
Table 2: Chemical analyses of the water samples after protection and continuous pumping (mg/l)
Name Ca	Mg	Na	K	SO4	HCO3	Cl	NO3	no2	EC	TDS	TH	Ph
									ps/Cm			
Wj 73.6	20.64	12.2	1.53	36.5	214	32.153	6.202	0.0066	496	400	270	7.53
W2 75.2	22.56	26	1.8	1.8	210	38.72	9.303	0.0066	544	420	294	7.63
W3 68	32.16	29	2.24	2.24	222	38.91	16.61	0.0099	608	480	330	7.15
The concentration of NO2 in water samples during pumping test and after protection and continuous pumping is shown in Fig. 9.
Fig. 9: The concentration of NO2 in water samples during pumping test and after protection and continuous pumping.
ENVIRONMENTAL ISOTOPES
Sampling of the water samples for analyzing the environmental isotopes (oxygen-18 Deuterium and Tritium) were taken according to the standard of the International Atomic Energy Agency (IAEA) on 12/10/2000. The water samples were analyzed for oxygen-18 and Deuterium at the
facuhy of Earth Sciences, Liverpool University, England during my sabbatical leave. The Tritium analysis was done in Austria. The result of the data is shown in the Table 3.
Table 3: The water samples analyses for oxygen-18, deuterium and tritium.
T	Altitude	d D (SMOW)	S 018	Tritium	Sample
(°C)	(m)	(0/00)	(0/00)	(TU)	
22	770	-14.9	-3.89	8.7	W 3
22	740	-18.2	-3.18	10.3	W 3
From the table it can be seen that the water samples with higher concentration of oxygen-18 (lower negative values) are recharged from lower altitude and vice versa.
Water samples show different values of Tritium (TU) in which the well (Wj) with 8.7 TU has the lowest and the well (W3) with 10.3 TU has the highest concentrations. In general the wells with higher values of Tritium have a lower residence time than those with lower concentrations.
CONCLUSIONS
The karstic features such as karrens and dolines are the main avenues for transmitting and storage of groundwater in the southern limb of Sarvak formation. Due to the protection of the area around the wells, the concentration of nitrate was reduced.
Analyses of the stable isotopes show that the water samples have different recharge area (altitude effect). The W1 with lower concentration of tritium has higher residence time than the W.
SUGGESTIONS
Since the wells are the only source of fresh-water drinking of the city therefore the following points are recommended:
1	- The wells must be protected from any source of pollution
2	- Piezometric wells must be drilled around the wells in order to have a continuous record of
water level.
3	- Isotopic analyses must be carried out for a longer time in order to have a better understanding
of recharge and residence time of the wells.
ACKNOWLEDGEMENT
The author wishes to thank the authorities of Water-sewage Corporation of Lorestan province for its financial support. The author also thanks Dr. Jim Marshall of the faculty of Earth Sciences, Liverpool University for his fruitful discussions.
REFERENCES
Ahmadipour, M.R., 1998: Hydrogeologicai Studies of Alashtar Basin., proceedings ofthe 2nd International Symposium on karst water resources, Iran, july., 1998 Tehran-Kermanshah Ahmadipour, M.R., 1999: Groundwater in the karst of Lorestan, proccedings of the first National conference on engineering geology and the environment, 1999 Tarbiat Moallem University-Tehran
Fryar, A.E. et al., 2000: Journal of contaminant hydrology, vol. 40, pp 335-363 George H. Davis, 1996: Structural Geology of Rocks and Regions Hill D. Hem., 1986: study and interpretation of the chemical characteristics of natural water Hill, A.R., 1982: Nitrate distribution in the groundwater of Allison Region of Ontario Groundwater, Vol. 20, No. 6, pp. 696-70
VLOGA GEOLOŠKE FORMACIJE SARVAK ZA OSKRBO MESTA POL-E DOKHTAR (IRAN) S PITNO VODO
Povzetek
Formacija Sarvak je najbolj zakrasela formacija v skupini Bagestan pri vasi Gol-Gol, okoli 14 km severozahodno od mesta Pol-e Dokhtar. Zaradi tektonske aktivnosti in raztapljanja, so v južnem krilu formacije Sarvak razvite kraške oblike, kot npr. škraplje in vrtače. Zakraselo podzemlje je najpomembnejše tako za pretakanje kot tudi za hranjenje talne vode. Za oskrbo s pitno vodo mesta Pol-e Dokhtar, ki šteje preko 20.000 prebivalcev, so bili v južnego krilo Sarvak formacije izvrtani trije vodnjaki. Avtor je opravil črpalni preizkus v trajanju 72 ur. V vodnjakih se ni pokazal pomembnejši upad gladine. Da bi ugotovili izvor vode in njen čas zadrževanja v podzemlju, so bile na vzorcih vode opravljene analize okoljskih izotopov. Analize kisika 18 in devterija so naredili na Fakulteti za znanosti o Zemlji univerze v Liverpoolu (Anglija). Vsi vzorci vode so bili v okviru meteorne vode, kar kaže tudi na tak izvor vode. Analize tricija so bile opravljene v Avstriji. Voda iz vodnjaka Wj ima minimalno, iz W^ pa maksimalno koncentracijo tricija, kar kaže, da ima voda v vodnjaku Wj daljši rezidenčni čas, kot v vodnjaku W^. Kemične analize vzorcev vode kažejo, da gre za vode tipa Ca>Mg>Na in HCO3>SO4>Cl. Med samim vrtanjem so imeli vzorci vode relativno veliko količino NO3 (27 mg/l). Zaradi črpalnega preizkusa in zaradi zavarovanja področja pred kmetijsko dejavnostjo, se je koncentracija NG^ znižala na 7,1 mg/l. Mesto Pol-e Dokhtar, ki je imelo resne težave z oskrbo s pitno vodo še izpred časov islamske republike, teh zdaj nima več, zahvaljujoč predstavljeni raziskavi.