MODELLING THE GROUNDWATER FLOW IN THE CATCHMENT OF THE AL-HAZA OASIS
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MODELLING THE GROUNDWATER FLOW IN THE CATCHMENT OF THE AL-HAZA OASIS

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This thesis deals with the numerical modeling of the groundwater flow in the Al-Haza Oasis catchment that is located in the Eastern Province of Saudi Arabia.

This thesis deals with the numerical modeling of the groundwater flow in the Al-Haza Oasis catchment that is located in the Eastern Province of Saudi Arabia.

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    MODELLING THE GROUNDWATER FLOW IN THE CATCHMENT OF THE AL-HAZA OASIS MODELLING THE GROUNDWATER FLOW IN THE CATCHMENT OF THE AL-HAZA OASIS Presentation Transcript

    • Modeling of the Groundwater Flow in the Catchment of the Al-Haza Oasisand Verification with Isotope Information Master Thesis by Saul Montoya
    • INTRODUCTION• The Arabian Peninsula lie in the Sahara climate zone• The Kingdom of Saudi-Arabia is covered by large deserts of rock and sand• Low precipitation and a very arid climate• No continuous surface water; existing groundwater filled during the last ice age
    • • Continuous increase in groundwater extraction• The groundwater level has fallen dramatically in some areas of the Kingdom• Sustainable groundwater management and conservation schemes have to be adopted Quantification of NumericalGroundwater the Groundwater GroundwaterManagement Budget Modeling
    • STUDY AREA
    • OBJECTIVES• Investigation of the groundwater flow patterns in the Hofuf Area and the catchment of the Al Haza Oasis – Numerical 3D finite-difference model – Transient boundary conditions – Calibration with measured head information• Verification of the flow results with isotope information• Simulation of continuous extraction till the year 2030
    • AQUIFER SYSTEM• Sedimentary formations dipping east- northeast towards the Arabian Gulf• The dipping of the formations is interrupted by structures• The thickness of the deeper formations increases to the east
    • Age Formation Member QUATERNARY SUPERFICIAL DEPOSITS   HOFUF   NEOGENE DAM    HADRUKH   ALAT KHOBAR TERTIARY DAMMAN  ALVEOLINA LIMESTONE EOCENE SAILA SHALE  MIDRA SHALE RUS   PALAEOCENE UMM ER RADHUMA   CRETACEOUS ARUMA    Generalized Litho-stratigraphic Sequence in Eastern Saudi Arabia
    • Bahrain Arabian Gulf Ghawar AnticlineGeological Cross Section
    • Global View of the Geological Setting
    • Springs Sabkhas Arabian GulfHydrogeological Cross Section
    • MODEL CONCEPTUALIZATION• Aquifer system modeled with MODFLOW using the visual interface of GMS• Transient simulation: – Block Centered Flow Package (BCF) – Strong Implicit Procedure Solver (SIP) • 200 iterations per time step • Acceleration parameter: 0.07 – Rewetting of dry cells is allowed
    • VERTICAL AND HORIZONTAL DISCRETIZATION• 5 layers in the vertical direction• Square mesh of 148 rows and 225 columns, uniform grid size of 2km x 2km 2 Km 2 Km
    • TIME DISCRETIZATION• The transient simulation starts from the last glaciation to December 2005• 120 stress periods, of different lengths and with different numbers of time steps Stress Period  Time Steps per Str.  Stress Period   Interval   Interval Period Duration Duration 1 to 50 8 200 years 10000 years 50 to 54 1 10 years 40 years 55 to 120 1 1 year 65 years
    • HORIZONTAL BOUNDARY CONDITIONS
    • INNER BOUNDARY CONDITONS• Initial Heads• Recharge 70.00 60.00 50.00 Recharge rate (mm/year) 40.00 30.00 20.00 10.00 - -8000 -7000 -6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 Year
    • • Evapotranspiration• Well Abstraction -60 -50 -40 PUMPING RATE (m3/s) -30 -20 -10 1940 1950 1960 1970 1980 1990 2000 0 YEAR• Springs´ Conductance
    • MODEL CALIBRATION• Trial-and-error parameter estimation• Calibrated model parameters: – Transmissivity – Hydraulic conductivity – Storage coefficient – Leakance• Geological structures and flow patterns were taken as indirect indicators
    • 160 150COMPARISON WITH OBSERVED DATA 140 HC-4-N - Computed 130 HC-4-N - Observed 120 WATER HEAD (m.)•Neogene aquifer: 110 100 90 80 70 160 60 50 150 40 140 1940 1950 1960 1970 1980 1990 2000 130 YEAR WATER HEAD (m.) 120 110 100 90 HD-2-N - Computed HD-2-N - Observed 80 70 1940 1950 1960 1970 1980 1990 2000 YEAR
    • 160 160 140 140 120 100 •Damman aquifer: 120 WATER HEAD (m.)WATER HEAD (m.) 100 80 60 80 40 60 HH-2-K - Computed 20 HH-2-K - Observed 40 0 HC-5-K - Computed HC-5-K - Observed 20 -20 -40 0 1940 1950 1960 1970 1980 1940 1990 1950 2000 1960 1970 1980 1990 2000 YEAR YEAR
    • 210 210 200 200 190 190 180 180 170 HH-3-U - Computed H-14-U - Computed •Umm Er Radhuma Aquifer 170 160 WATER HEAD ELEVATION (m.) H-14-U - Observed HH-3-U - Observed 160 150WATER HEAD ELEVATION (m.) 150 140 140 130 130 120 120 110 110 100 100 90 90 80 80 70 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0 -10 -10 1940 1950 1960 1970 1980 1990 2000 1940 1950 1960 1970 1980 1990 2000 YEAR YEAR
    • COMPARISON WITH MEASURED DRAINDISCHARGE•Computed discharge in Al-Hasa Oasis in 1900: 4.07m3/s•Measured outflow in 1900: 10m3/s•Several approaches of transmissivities andleakance distribution were done•Total evapotranspiration in the Neogene: 7.25m3/s
    • CALIBRATION ANALYSIS• Aquifer system is multilayered and interconnected• Modeling and calibration part was intensive; however, more runs have to be done• Quality of the results cannot be better than the quality of the input data• Discrepancies are minor, computed heads match reasonably the observed heads
    • 160 150 150 140 ANALISYS OF FLOW RESULTS 140 130 130 120 110 WATER HEAD (m.) 120Water Head (m.) 110 100 100 90 90 80 HH-2-NEOGENE 80 70 HH-2-DAMMAN HD-5-NEOGENE 60 HH-2-UMM ER RADHUMA 70 HD-5-DAMMAN 60 HD-5-UMM ER RADHUMA 50 50 40 40 30 1940 1950 1960 1970 1940 1980 1950 1990 1960 2000 1970 1980 1990 2000 YEAR YEAR
    • WATER BALANCE   Flow Rates (m3/s)   1900 2005 NEOGENE AQUIFER Recharge elements By rainfall 9,98 5,59 By saline water intrusion 0,03 5,49 By upward flow from Damman Aquifer 4,51 0,43 Change in storage 0,59 11,84 Discharge elements By drainage in the Al Hasa Oasis 4,07 0 By downward flow to Damman Aquifer 1,71 14,29 By well abstraction 0 6,24 By evapotranspiration 7,25 2,21 By submarine springs 2,1 0,61 DAMMAN AQUIFER Recharge elements: By downward flow from Neogene Aquifer 1,71 14,29 By rainfall 2,2 1,55 By upward flow from Umm Er Radhuma Aquifer 2,3 0,4 By saline water intrusion 0,01 0,12 Change in storage 0,01 0,64 Discharge elements: By well abstraction 0 8,81 By downward flow to Umm Er Radhuma Aquifer 0,81 7,18 By upward flow to Neogene Aquifer 4,51 0,43 By evapotranspiration 0,53 0,37 By submarine springs 0,37 0,22
    •   Flow Rates (m3/s)  1900 2005UMM ER RADHUMA AQUIFERRecharge elements By upward flow from Aruma Aquifer 1,95 9,01 By downward flow from Damman Aquifer 0,81 7,38 By rainfall 1,47 0,86Change in storage 0,12 23,13Discharge elements Well abstraction 0 39.21 By downward flow to Aruma Aquifer 1,35 1,09 By upward flow to Damman Aquifer 2,31 0,35 By evapotranspiration 0,70 0,11ARUMA AQUIFERRecharge elements: By downward flow from Umm Er Radhuma Aquifer 1,35 1,09 By rainfall 0,62 0,36Change in storage 0,03 7,60Discharge elements: By upward flow to Umm Er Radhuma Aquifer 1,95 9,01
    • COMPARISON WITH ISOTOPEINFORMATION• Isotope investigation can give information about groundwater sources, ages, travel times and flow paths• Isotope investigation has been done in the Al Qatif and Al Haza Oasis
    • STABLE ISOTOPE INFORMATION Relationship between δD and δ18O 10 0 -9 -7 -5 -3 -1 1 -10 Al Hasa δD 0/00 Al Qatif -20 c δ2H = 8. δ18O + 10 -30 -40 -50 δ18O 0/00 Relationship between δD and δ18O
    • RADIOACTIVE ISOTOPE INFORMATION•Water samples of the Al Qatif Oasis have a 14 C age of >22000 years•In the Al Haza Oasis the two samples give a 14 C age of >33000 years Al Qatif Oasis Al Hasa Oasis Sample Number 3 H content (TU) Location 3 H content (TU) 126 <0.8 24 <0.7 127 <0.8 25 <2.6 128 <2.3 26 <2.3 129 <0.9 27 <2.5 130 <2.3 28 <0.5 131 <2.7 29 <2.5 133 <2.7 30 <1.2 141 <0.9 31 <2.8 143 <2.2 32 <0.9 125 <2.7 Tritium content in Al Qatif and Al Hasa waters
    • PARTICLE TRACKING SIMULATION PARTICLE D AGE: 2500 YEARS PARTICLE C AGE: 1000 YEARS PARTICLE A AGE: 6000 YEARS PARTICLE B AGE: 1000 YEARS
    • t=0 WATER COMMING FROM THE ARUMA AQUIFER AGE: 6000 YEARS t = 1000 y. t = 5000 y. t = 2000 y. t = 6000 y. t = 4000 y. t = 3000 y.Cross Section following the Tracking of Particle A – Al Haza WATER COMMING FROM THE NEOGENE AQUIFER AGE: 1000 YEARS t=0 t = 1000y.Cross Section following the Tracking of Particle B – Al Haza
    • WATER COMMING FROM THE NEOGENE AQUIFER AGE: 1000 YEARS t=0 t = 1000 y.Cross Section following the Tracking of Particle C – Al Qatif t= 0 WATER COMMING FROM THE DAMMAN AQUIFER AGE: 2500 YEARS t = 1000 y. t = 2000 y. t = 2500 y.Cross Section following the Tracking of Particle D – Al Qatif
    • SIMULATION OF CONTINUOUSABSTRACTION• Impact of actual groundwater extraction till 2030 2005 150 125 WATER LEVEL ELEVATION (m.) 100 75 50 25 HC-4-N (NEOGENE) 0 HC-5-K (DAMMAN) -25 HC-5-U (UMM ER RADHUMA) -50 1940 1960 1980 2000 2020
    • Heads distribution in2005 the Umm Er Radhuma WASA WELLFIELD 2030 WASA WELLFIELD
    • CONCLUSIONS• The industrial, domestic and agricultural activities make the aquifer system overexploited• Flow takes place in the horizontal and vertical direction, allowing exchange between aquifers• Use of indirect and direct indicators is essential to asses the preferential flow directions• The model can represent the groundwater flow in the catchment of the Al Hasa Oasis.• It was corroborated that the aquifer system was in steady state in 1900
    • • Some factors could be improved to get a better conceptualization of the aquifer system• The reliability of this simulation depends on the quality of the abstraction data that has some uncertainties• From the prognostic scenario, the current pumping rates will deplete the whole aquifer system by 2030• It might be that the study area does not cover the whole extension of the Al Hasa catchment• Isotope information confirms the modeling accuracy in the Al Hasa Oasis; although in the coastal region, there is a need to improve the calibration
    • Modeling of the Groundwater Flow in the Catchment of the Al-Haza Oasisand Verification with Isotope Information Master Thesis by Saul Montoya