Modeling of the Groundwater Flow in the Catchment of the Al-Haza Oasis

and 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

Groundwater Management

Quantification of the Groundwater Budget

Numerical Groundwater 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 

TERTIARY

NEOGENE

HOFUF  

DAM  

HADRUKH  

EOCENEDAMMAN

ALAT

KHOBAR

ALVEOLINA LIMESTONE

SAILA SHALE

MIDRA SHALE

RUS  

PALAEOCENE UMM ER RADHUMA 

CRETACEOUS ARUMA  

Generalized Litho-stratigraphic Sequence in Eastern Saudi Arabia

Geological Cross Section

BahrainArabian Gulf

Ghawar Anticline

Global View of the Geological Setting

Hydrogeological Cross Section

Arabian Gulf

Springs Sabkhas

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 Interval

Time Steps per Str. Period

Stress Period Duration

Interval 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

-

10.00

20.00

30.00

40.00

50.00

60.00

70.00

-8000 -7000 -6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000

Year

Rec

har

ge

rate

(m

m/y

ear)

• Recharge

• Initial Heads

-60

-50

-40

-30

-20

-10

0

1940 1950 1960 1970 1980 1990 2000

YEAR

PU

MP

ING

RA

TE (m

3/s)

• Evapotranspiration

• Springs´ Conductance

• Well Abstraction

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

COMPARISON WITH OBSERVED DATA

•Neogene aquifer:

40

50

60

70

80

90

100

110

120

130

140

150

160

1940 1950 1960 1970 1980 1990 2000

YEARW

AT

ER

HE

AD

(m

.)

HC-4-N - ComputedHC-4-N - Observed

70

80

90

100

110

120

130

140

150

160

1940 1950 1960 1970 1980 1990 2000

YEAR

WA

TE

R H

EA

D (

m.)

HD-2-N - Computed

HD-2-N - Observed

•Damman aquifer:

-40

-20

0

20

40

60

80

100

120

140

160

1940 1950 1960 1970 1980 1990 2000

YEAR

WA

TE

R H

EA

D (

m.)

HC-5-K - ComputedHC-5-K - Observed

0

20

40

60

80

100

120

140

160

1940 1950 1960 1970 1980 1990 2000

YEAR

WA

TE

R H

EA

D (

m.)

HH-2-K - Computed

HH-2-K - Observed

•Umm Er Radhuma Aquifer

-100

102030405060708090

100110120130140150160170180190200210

1940 1950 1960 1970 1980 1990 2000

YEAR

WA

TE

R H

EA

D E

LEV

AT

ION

(m

.)

H-14-U - ComputedH-14-U - Observed

-100

102030405060708090

100110120130140150160170180190200210

1940 1950 1960 1970 1980 1990 2000

YEAR

WA

TE

R H

EA

D E

LEV

AT

ION

(m

.)

HH-3-U - ComputedHH-3-U - Observed

COMPARISON WITH MEASURED DRAIN DISCHARGE

•Computed discharge in Al-Hasa Oasisin 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

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

ANALISYS OF FLOW RESULTS

40

50

60

70

80

90

100

110

120

130

140

150

160

1940 1950 1960 1970 1980 1990 2000

YEAR

Wat

er

He

ad (

m.)

HD-5-NEOGENE

HD-5-DAMMAN

HD-5-UMM ER RADHUMA

30

40

50

60

70

80

90

100

110

120

130

140

150

1940 1950 1960 1970 1980 1990 2000

YEAR

WA

TE

R H

EA

D (

m.)

HH-2-NEOGENEHH-2-DAMMANHH-2-UMM ER RADHUMA

WATER BALANCE  Flow Rates (m3/s)  1900 2005

NEOGENE AQUIFER    Recharge elements    

By rainfall 9,98 5,59By saline water intrusion 0,03 5,49By upward flow from Damman Aquifer 4,51 0,43

Change in storage 0,59 11,84Discharge elements    

By drainage in the Al Hasa Oasis 4,07 0By downward flow to Damman Aquifer 1,71 14,29By well abstraction 0 6,24By evapotranspiration 7,25 2,21By submarine springs 2,1 0,61

     DAMMAN AQUIFER    Recharge elements:    

By downward flow from Neogene Aquifer 1,71 14,29By rainfall 2,2 1,55By upward flow from Umm Er Radhuma Aquifer 2,3 0,4By saline water intrusion 0,01 0,12

Change in storage 0,01 0,64Discharge elements:    

By well abstraction 0 8,81By downward flow to Umm Er Radhuma Aquifer 0,81 7,18By upward flow to Neogene Aquifer 4,51 0,43By evapotranspiration 0,53 0,37By submarine springs 0,37 0,22

  Flow Rates (m3/s)  1900 2005

UMM ER RADHUMA AQUIFER    Recharge elements    

By upward flow from Aruma Aquifer 1,95 9,01By downward flow from Damman Aquifer 0,81 7,38By rainfall 1,47 0,86

Change in storage 0,12 23,13Discharge elements    

Well abstraction 0 39.21By downward flow to Aruma Aquifer 1,35 1,09By upward flow to Damman Aquifer 2,31 0,35By evapotranspiration 0,70 0,11

     ARUMA AQUIFER    Recharge elements:    

By downward flow from Umm Er Radhuma Aquifer 1,35 1,09By rainfall 0,62 0,36

Change in storage 0,03 7,60Discharge elements:    

By upward flow to Umm Er Radhuma Aquifer 1,95 9,01

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

STABLE ISOTOPE INFORMATION

-50

-40

-30

-20

-10

0

10

-9 -7 -5 -3 -1 1

δ18O 0/00

δD

0/0

0

Al Hasa

Al Qatif

δ2H = 8. δ18O + 10 c

Relationship between δD and δ18O

RADIOACTIVE ISOTOPE INFORMATION

•Water samples of the Al Qatif Oasis have a 14C age of >22000 years

•In the Al Haza Oasis the two samples give a 14C age of >33000 years

Tritium content in Al Qatif and Al Hasa waters

Al Qatif Oasis Al Hasa OasisSample Number 3H content (TU) Location 3H content (TU)

126 <0.8 24 <0.7127 <0.8 25 <2.6128 <2.3 26 <2.3129 <0.9 27 <2.5 130 <2.3 28 <0.5131 <2.7 29 <2.5133 <2.7 30 <1.2141 <0.9 31 <2.8143 <2.2 32 <0.9125 <2.7

PARTICLE TRACKING SIMULATION

PARTICLE AAGE: 6000 YEARS

PARTICLE BAGE: 1000 YEARS

PARTICLE DAGE: 2500 YEARS

PARTICLE CAGE: 1000 YEARS

Cross Section following the Tracking of Particle A – Al Haza

WATER COMMING FROM THE ARUMA AQUIFERAGE: 6000 YEARS

t = 0

t = 1000 y.

t = 2000 y.

t = 3000 y.t = 4000 y.

t = 5000 y.t = 6000 y.

t = 0

WATER COMMING FROM THE NEOGENE AQUIFERAGE: 1000 YEARS

t = 1000y.

Cross Section following the Tracking of Particle B – Al Haza

WATER COMMING FROM THE DAMMAN AQUIFERAGE: 2500 YEARS

t = 0

t = 1000 y.t = 2000 y. t = 2500 y.

WATER COMMING FROM THE NEOGENE AQUIFERAGE: 1000 YEARS

t = 1000 y.

t = 0

Cross Section following the Tracking of Particle C – Al Qatif

Cross Section following the Tracking of Particle D – Al Qatif

SIMULATION OF CONTINUOUS ABSTRACTION• Impact of actual groundwater extraction till

2030

-50

-25

0

25

50

75

100

125

150

1940 1960 1980 2000 2020

WA

TE

R L

EV

EL

EL

EV

AT

ION

(m

.)

HC-4-N (NEOGENE)

HC-5-K (DAMMAN)

HC-5-U (UMM ER RADHUMA)

2005

Heads distribution in the Umm Er Radhuma

2030

WASA WELLFIELD

2005

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 Oasis

and Verification with Isotope Information

Master Thesis

by Saul Montoya