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.

1. Modeling of the Groundwater Flow
in the Catchment of the Al-Haza Oasis
and Verification with Isotope Information
Master Thesis
by Saul Montoya

2. 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

3. • 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 Numerical
Groundwater
the Groundwater Groundwater
Management
Budget Modeling

4. STUDY AREA

5. 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

6. 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

7. 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

8. Bahrain
Arabian Gulf
Ghawar Anticline
Geological Cross Section

9. Global View of the Geological Setting

10. Springs Sabkhas
Arabian Gulf
Hydrogeological Cross Section

11. 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

12. 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

13. 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

14. HORIZONTAL BOUNDARY CONDITIONS

15. 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

16. • Evapotranspiration
• Well Abstraction
-60
-50
-40
PUMPING RATE (m3/s)
-30
-20
-10
1940 1950 1960 1970 1980 1990 2000
0
YEAR
• Springs´ Conductance

17. 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

18. 160
150
COMPARISON 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

19. 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

20. 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
160 150
WATER 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

21. COMPARISON WITH MEASURED DRAIN
DISCHARGE
•Computed discharge in Al-Hasa Oasis
in 1900: 4.07m3/s
•Measured outflow in 1900: 10m3/s
•Several approaches of transmissivities and
leakance distribution were done
•Total evapotranspiration in the
Neogene: 7.25m3/s

22. 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

23. 160 150
150
140 ANALISYS OF FLOW RESULTS 140
130
130 120
110
WATER HEAD (m.)
120
Water 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

24. 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

25. Flow Rates (m3/s)
1900 2005
UMM ER RADHUMA AQUIFER
Recharge 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 0,86
Change in storage 0,12 23,13
Discharge 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 0,11
ARUMA AQUIFER
Recharge elements:
By downward flow from Umm Er Radhuma Aquifer 1,35 1,09
By rainfall 0,62 0,36
Change in storage 0,03 7,60
Discharge elements:
By upward flow to Umm Er Radhuma Aquifer 1,95 9,01

26. COMPARISON WITH ISOTOPE
INFORMATION
• 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

28. 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

29. 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

30. PARTICLE TRACKING SIMULATION
PARTICLE D
AGE: 2500 YEARS
PARTICLE C
AGE: 1000 YEARS
PARTICLE A
AGE: 6000 YEARS
PARTICLE B
AGE: 1000 YEARS

31. 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

32. 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

33. SIMULATION OF CONTINUOUS
ABSTRACTION
• 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

34. Heads distribution in
2005 the Umm Er Radhuma
WASA
WELLFIELD
2030
WASA
WELLFIELD

35. 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

36. • 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

37. Modeling of the Groundwater Flow
in the Catchment of the Al-Haza Oasis
and Verification with Isotope Information
Master Thesis
by Saul Montoya