ELECTRICAL RESISTIVITY IMAGING FOR QUATERNARY AQUIFER IN WADI MURAYKHAT AND WADI SA A, AL AIN AREA, UAE.

Transcription

1 ELECTRICAL RESISTIVITY IMAGING FOR QUATERNARY AQUIFER IN WADI MURAYKHAT AND WADI SA A, AL AIN AREA, UAE. By: Ahmed. El-Mahmoudi KFU University, Water Studies Centre, KSA

2 Figure (#) Map of Al Jaww Plain and locations of Wadi Muraykhat and Wadi Sa a (modified from Warrak, 1986).

3 Objectives These wadis originate from the Oman Mountains range and form the catchment and feeding area of the water resources. So, From the hydrogeological point of view, subsurface investigation of these wadies is very important for better understanding of the Quaternary aquifer system. To Map the subsurface conditions of the Quaternary alluvial aquifer system at Wadi Muraykhat & Wadi Sa a, Al Jaww Plain through (2-D) electrical Resistivity tomography survey.

4 To achieve these Objectives Reviewing the Geology of study area. A series of data including: Borehole data Geophysical Investigations (2-D Resistivity, TEM Data

5 GEOLOGICAL ASPECTS

6 E E E E E E N N N A-Geomorphology N Northern Dunes N IV OMAN MOUNTAINS N N I N N AL AIN III II N Jabal Hafit I N AL JAWW PLAIN N IV N N Southern Dunes OMAN MOUNTAINS I N 10 km I. Mountain areas II. Piedmonts and alluvial plains III. Al Ain urban area IV. Sand dune area Northern sand dune area Southern sand dune area Roads E E E E

7

8 BIDA BINT SAUD N Wadi Towayya AL OHA B-Geological Map of the Study Area, showing the different rock units N Wadi Al Jimi Wadi Al Ain AL AIN Jabal Oha BUREIMI Jabal Huwayya Jabal Qatar Jabal Zarub Wadi Shik N Wadi Idan Wadi Muthaymimah Jabal Malaqet Jabal Muthaymimah Wadi Sa a Jabal Hafit Wadi Muraykhat N 5 km Quaternary alluvium Eocene and Paleocene rocks Thrust fault ~~~~~~ Unconformity ~~~~~~ Unconformity Road Upper For a Formation Simsima Formation Wadi Lower For a Formation ~~~~~~ Unconformity Geologic contact ~~~~~~ Unconformity S Nappe Formation Asmari Formation Thrust fault ~~~~~~ Unconformity Haybi Complex and Hawasina Series

9 C-Surface Lithologic units at Al Jaww Plain OMAN Al Jaww F Plain D F

10 D-Structure Setting Bouguer anomaly map of Al Jaww Plain showing gravity anomaly lows in the centre and gradual increase to the east of the survey area (After Ali et. al 2008).

11 Boundary of concession area (aaproximate) E E N N IQS E N OMAN MOUNTAINS E E N N IQS E N OMAN MOUNTAINS N N N N 10 km 10 km 25 IQS-18 IQS N N N N IQS-8 IQS N N N AL AIN IQS-11 AL AIN N N N Jabal Hafit IQS N 25 Mountains Reprocessed Seismic Line Primary Roads Ground water research project well Jabal Hafit AL JAWW PLAIN N IQS-8 Mountains Thrust Fault Reprocessed Seismic Line Primary Roads E E E AL JAWW PLAIN N E E E Amoco seismic lines and uphole-survey locations (after Woodward, 1994). Generalized subsurface structural features in Al Ain area (after Woodward, 1994).

12 WEST IQS ALTITUDE IN 280 METERS ABOVE SEA LEVEL LAND SURFACE DISTAL ANTICLINE Anticline F5b Syncline F2c EAST DEPTH BELOW DATUM OF 91.5 METERS ABOVE SEA LEVEL, IN SECONDS OF 2-WAY SEISMIC TRAVEL-TIME 1 2 SEISMIC REFLECTOR 1 2 IQS ALTITUDE IN 380 METERS ABOVE SEA LEVEL DEPTH BELOW DATUM OF 91.5 METERS ABOVE SEA LEVEL, IN SECONDS OF 2-WAY SEISMIC TRAVEL-TIME Syncline Anticline F F5b Interpreted seismic lines at Al Jaww Plain and north of Al Jaww Plain, (modified after Woodward, 1994). 2 2 IQS

13 Combined interpretation of the data, which is consistent with all available geological and geophysical data. The position of folds and reverse faults are shown. Also shown are the approximate positions of the Hawasina and S Ophiolite thrust fronts, (After Ali et. al 2008).

14 HYDROGEOLOGICAL ASPECTS

15 25 o 52 o 53 o 54 o 55 o 56 o Sha am LEGEND Northern limestone aquifer Ophiolite aquifer Eastern gravel aquifer Western gravel aquifer Sand dune aquifer Coastal sabkha Cultivated areas Main Cities A-Different Aquifers in N UAE. A r a b i a n G u l f Dubai Umm Al Qaiwin Ajman Sharjah Ras Al Khaimah Al Dhaid Al Shiuab Al Khatt Masafi Al Faiyah Al Madam OMAN Hatta Dibba Khor Fakkan Gulf of Oman Fujairah 25 o Kalba Dalma Bani Yas Abu Dhabi Al Hayer 24 o Jabal Dhanna Jabal Hafit Al Ain Al Jaww Plain 24 o Al Sih O M A N Madinat Zayed Al Wagan U N I T E D A R A B E M I R A T E S 23 o S A U D I Liwa 23 o A R A B I A 50 km 52 o 53 o 54 o 55 o 56 o

16 B- Geologic Framework of the Eastern Region of Abu Dhabi Emirate (after Bright, 1998) Age Quaternary Pliocene- Miocene Geologic Sequence Eolian Sand Alluvium Post-Fars Upper Fars Approximate Thickness (m) Hydrologic Unit Unsaturated overburden Surficial Aquifer system Eolian Sand Quaternary Alluvium Altered Tertiary Deposits Unaltered Tertiary Deposits Clastic Limestone Deep Limestone Miocene- Oligocene Paleocene- Eocene Cretaceous Lower Fars Fm. Asmari Fm. Dammam Fm. Rus Fm. Umm er-radhuma Fm. Simsima Fm. Qahlah Fm. Juweiza Fm ,200 3,000 Basal Confining system Pre-Tertiary Deposits

17 C-Quaternary Aquifer Geometry

18

19 D-Flow System and water level assessment (After Al Nuaimi, 2003)

20 Geophysical Investigations

21 A-2-D Resistivity Data Acquisition

22 Base Map of 2-D Resistivity Profiles Well No.GWP Jabal Hafit 2` 1` 2 1 4` 4 3` ` 6` 7 8 7` 8` 13` 13 12`12 11` 11 10` 10 9` Legend Wells provided by WED Main Road 3 3`2-D Resistivity Profile

23 Typical TEM data from sounding Zarub-2-2 and Zarub Zarub-2-2 Zarub-2-11 The observed data and the model response Interpreted layer resistivity.

24 Base map showing the Electromagnetic survey at Al Qura'a area north of Al Ain (after US Geological Survey, 1993)

25 WSTA 8 Th Gulf Water Conference, 3-6 March , Manama, Bahrain DEPTH (m) Below land surface LITHOLOGY RESISTIVITY (Ohm.meters) Resistivity model of typical resistivities for interdune soundings at Al Qura a, north of Al Ain (after US Geological survey, 1993). DESCRIPTION , R1: Surface resistive layer (aeolian sand and alluvium, dry) C1: Upper conductive layer (mostly clay and silt) R2: Upper resistive layer (alluvial sand and gravel; possible calcareous cement) R3: Primary resistive layer (alluvial sand and gravel; good permeability; fresh water where saturated) C2: Conductive layer (mostly clay and silt) C3: Conductive layer (mostly clay and mudstone; poor water quality)

26 Depth (meters) GWP sand & gravel 20 sand & gravel calcareously cemented sand gravelly clay 60 clay Resistivity (ohm-m) 1000 Well GWP-18 log information. The solid and dashed lines) green &red) are the deep and medium induction logs. The heavy line (Blue) is the blocked resistivity model based upon the induction logs. Layer lithology is shown (After Fitterman, et al.1991).

27 2 2` 6 6` 12 12`

28 Gravel and sand zone of moderate resistivity Paleo channel Surface resistive layer (Dry alluvium) 1 1` Conductive Layer (Clay & Mudstone Conductive Layer (Clay & Mudstone Figure (#) 2-D Resistivity profile along line 1-1` 11 Gravel and sand zone Of moderate resistivity Paleo channel Surface resistive layer (Dry alluvium) 11` Conductive Layer (Clay & Mudstone Conductive Layer (Clay & Mudstone Figure (#) 2-D Resistivity profile along line 11-11`

29 Conclusions 2-D resistivity tomograms of the Thirteen profiles indicate clearly the different hydrostratigraphic units of Quaternary aquifer along the eastern margin of Al Jaww plain Erosional unconformities at the base of the Quaternary alluvium are traced along some of the (2-D) profiles. These unconformities represent the paleochannels in the bed rock that were formed in the geological past by the ancient wadies. These paleochannels are promising targets for fresh groundwater, as they contain appreciable thickness of water-bearing formations that are recharged from the surrounding mountain region. ( Channel Deposits serve as both storage reservoirs and recharge zones for the shallow aquifer system in Al Jaww Plain. This contribution will provide the technical support for planners, decision makers, and researchers in the field of groundwater development and management. Especially, Now days Aquifer Storage and Recovery system (ASR) Projects are implemented in Al Ain area and elsewhere at UAE.

30 Thank You For your attention