Water resource situation of the Republic of Djibouti€¦ · Dalha basalts, the stratoid basalts and the Mabla rhyolites. Dalha basalts sequence Coastal plain sediments Integrating

Water resource situation of the Republic

of Djibouti

Omar ASSOWE DABAR

Integrating Groundwater Management within River Basins

15-17 January 2019 Nairobi, Kenya

Regional Training Workshop on Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya

Introduction

❖ The Republic of Djibouti (23 000 km2) is localized in the Horn Africa.

❖70% of the population live in urban areas, 58% live in the capital (Djibouti city).

2

❖ Djibouti is an arid country which receives, on

average, 150 mm of rain annually and has no

permanent source of surface water.

❖Access to water in Djibouti is a major

challenge for the development of socio-

economic activities.

❖ Harnessing surface and groundwater to

improve access to drinking water for vulnerable

populations is a Government priority

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya

Geological situations

❑ Geological Setting

3

❖ The republic of Djibouti is one of several African

countries located on the East African Rift System

(EARS).

❖ About 90% of the geological formations are

volcanic rocks and 10% are sedimentary formations.

❖ The groundwater in Djibouti is controlled by

volcanic and sedimentary aquifers. Volcanic

aquifers systems are mainly represented by the

Dalha basalts, the stratoid basalts and the Mabla

rhyolites.

Dalha basalts sequence Coastal plain sediments


Climatological conditions

❖ The Republic of Djibouti is characterized by arid to semiarid climate. Two seasons

predominate :

- Cool season (winter) from October to April (20 °C and 30 °C )

- Hot season (summer) from May to September (30 °C and 45 °C) with high rate of

Evapotranspiration amounting to 2000 mm per year

4

Pré

cipitation (m

m)

HOLL HOLL

DIKHIL

Précipitation trends (1960 – 1990)

200

250

300

350

1960 1965 1970 1975 1980 1985 1990

130

140

150

160

170

180

1960 1965 1970 1975 1980 1985 1990


➢ Decrease in rainfall can be observed in different

location.

➢This could strongly impact groundwater recharge

conditions and deteriorate the quantity and quality.

Groundwater situation

5

❖Water resources demands


!(

!(

!(

!(

!(

!(

ARTA

OBOCK

DIKHIL

DJIBOUTI

TADJOURAH

ALI SABIEH

Annual pumping rate millions m3/an

0

0.01 à 0.1

0.1 à 0.5

0.5 à 1

1 à 2

plus de 10

1.7 2.6 3.2

15.2

22.9

28.5

12.5 15.2 1

9.3

29.4

40.8

51.0

0

20

40

60

2005 2010 2015

Vo

lum

e a

nn

uel.

Millio

n m

3

Rural (population+bétail)

Urbain

Agriculture

Total

1.7 2.6 3.2

15.2

22.9

28.5

12.5 15.2 1

9.3

29.4

40.8

51.0

0

20

40

60

2005 2010 2015

Vo

lum

e a

nn

uel.

Millio

n m

3

Rural (population+bétail)

Urbain

Agriculture

Total

❖ The extreme climate condition explains

the lack of permanent rivers, and has

led the country to exploit the only

available water resources, which are

represented by groundwater in the

basaltic aquifer.

➢ The population of Djibouti relies

heavily on groundwater resources for

drinking water and irrigation purposes.

Groundwater situation

6

❖Groundwater degradations


0

10

20

30

40

1960 1970 1980 1990 2000

Cl-

(mm

ol/l

)

70

80

90

100

1984 1986 1988 1990 1992 1994

Wate

r le

vel m

➢ The continuous and severe increase of water demands, due to the rapid

population growth, have led to overexploitation of groundwater, and have

severely depleted its quantity and quality.

Djibouti

Mouloud

Groundwater monitoring

7

❖Surface water mobilisation : Surface water hydrology monitoring-early warning system-Ambouli


Limnigraph

➢With the arid climatic regime, most watercourses in the Republic of Djibouti are temporary and

run for only a few days after any rain event (wadis).

Geochemical characterization of the Bara volcano-sedimentary

aquifer (Republic of Djibouti) : Case study

8

❖ The UNDP is financial supported a program

for developing agro-pastoral as a climate change

adaptation strategy for poor rural communities in

the south-eastern part of the republic of Djibouti

(Bara area).

❖The context of this project is based on the

settlement of a hundred families in this area. All

boreholes are used for drinking purpose.

❖The study area is located in the south-eastern

part of the country. The Petit Bara and Grand

Bara zones correspond to sedimentary basins

limited to the East by the Dalha basalts (8.3–

4.3Ma) and to theWest by the Stratoid basalts (3–

1 Ma).

❖ Twenty two borehole waters were collected in

this area and analysed.




9

❖Groundwater Classification


➢The groundwater have moderate to

high EC values (from 957 to 4846

S/cm), temperature values between

27 and 43C, and moderately alkaline

pH ranging from 7.31 to 8.38.

➢The Depth of the boreholes in this

area ranges between 80 and 200 m

➢Most of sampled groundwaters are

brackish (10 g/L TDS 1 g/L) with

the exception of several fresh waters

(TDS 1 g/L) from North of Petit

Bara (#1–#4), Grand Bara (Hambocto

F1) and Dadin3.

Samples T

(°C)

Depth

(m)

pH EC

(µS/cm)

TDS

(mg/l)

Hydrochemical types

Petit Bara Zone

PK48 36 133 7.75 956.9 666Na-HCO3-Cl

PK50 38 90 7.97 1127 795Na-HCO3-Cl

PK51 39 135 7.75 1204 811Na-HCO3-Cl

Didjander 28 170 7.96 2876 1617Na-Cl

Omar Jakka 38 161 7.79 2958 2015Na-Cl

Naheel 39 155 6564 3668 Na-Cl-Ca

Kourtimaley 37 165 7.8 7731 3254 Na-Cl-Ca

Grand Bara Zone

Awraoussa 1 36 195 7.81 2692 1842Na-Cl-Mg-Ca-SO4

Iskoutir 32 181 7.81 3258 2363Na-Cl-Ca-SO4

Gabla-galan 27 156 8.38 2200 1519Na-Cl-HCO3-SO4

Hambocto F2 35 190 7.26 1896 1329Na-Cl-Mg-Ca-HCO3

Hambocto F1 38 150 7.31 1464 988Na-Cl-Mg-Ca-HCO3

Doudoub Bololé F2 36 103 7.62 2337 1576Na-Cl-Mg-SO4

Doudoub Bololé F1 41 93 7.48 4143 3173Na-Cl-Mg-SO4

Dagandalol 43 113 7.8 2871 1879 Na-Cl-SO4

Dagaah-damere 39 170 7.71 4846 3484Na-Cl-Mg-Ca-SO4

Mouloud-Dadin Zone

Mindil 36 80 7.46 2630 1824Na-Cl-Mg-SO4

Mouloud C 39 115 7.49 3035 2075Na-Cl-Mg-SO4

Mouloud 4 39 140 7.33 2880 1965Na-Cl-Mg-SO4

Dadin 3 34 139 7.43 1388 980Na-Cl-HCO3



10

❖Groundwater Classification


➢ Using statistical method (PCA and HCA) The geochemical data were classified into distinct groups according to the

common variables they share using 13 variables (pH, EC, TDS, Ca2 +, Mg2 +, Na +, K +, HCO3-, Cl-, SO4

-, F-, NO3- , Br-).

Site

Ca

(mg/l)

Mg

(mg/l)

Na

(mg/l)

K

(mg/l)

Li

(mg/l)

NH4

(mg/l)

HCO3

(mg/l)

Cl

(mg/l)

SO4

(mg/l)

NO3

(mg/l)

F

(mg/l)

Br

(mg/l)

NO2

(mg/l)

Petit Bara Zone

PK48 26.75 22.74 151.6 4.1 0.017 0.01 347.84 100.09 65.65 12.43 0.825 0.41 0.006

PK50 24.9 22.19 187.66 4.36 0.04 ≤ DL 352.87 146.99 77.92 17.73 0.705 0.715 ≤ DL

PK51 23.1 21.07 222.9 4.34 0.01 ≤ DL 307.88 189.05 88.86 14.81 0.78 0.85 0.003

Didjander 88 63.18 383.99 18.45 0.9 0.13 237.09 609.5 197.62 32.49 0.01 2.88 0.033

Omar Jakka 89.95 68.86 435.67 8.45 0.022 ≤ DL 218.97 697.75 234 54.31 0.425 2.69 0.002

Naheel 215 231 852 11 0.2 0.43 95 1987 608 119 0.9 1.74 0.08

Kourtimaley 368 165 1080 32 ≤ DL ≤ DL 61 2410 572 122 0.245 1.78 0.008

Grand Bara Zone

Awraoussa 1 116.96 65.9 321.24 11.65 0.041 ≤ DL 140.76 519 295 71 0.64 2.59 ≤ DL

Iskoutir 145.73 65.19 440.13 8.165 0.015 ≤ DL 100.94 818.47 319.19 50.76 0.28 3.5 0.009

Gabla-galan 36.17 50.32 382.5 7.94 0.037 0.13 235.06 356 192.93 247.48 0.385 2.26 ≤ DL

Hambocto F2 115 66.78 169.53 4.98 0.0103 ≤ DL 209.68 269.19 131.17 255.67 0.595 2.35 ≤ DL

Hambocto F1 58.37 38.69 185.97 4.08 0.01 ≤ DL 239.72 249.78 112.53 49.83 1.01 1.27 ≤ DL

Doudoub Bololeh F2 70.97 61.92 327.53 7.65 0.0175 ≤ DL 166.09 517.22 240.18 55.075 0.675 2.085 ≤ DL

Doudoub Bololeh F1 165 134.78 507.45 13.13 0.03 ≤ DL 107.71 1120.4 418.7 59.11 0.61 4.125 ≤ DL

Dagandalol 88.54 57.43 453 8.26 0.037 ≤ DL 213.31 572.09 334 142.02 0.885 2.5 ≤ DL

Daagah-damere 199.28 123.44 653 15.30 ≤ DL 0.8 95 1271.5 486.5 62 0.09 5.29 0.21

Mouloud Zone

Mindil 55.11 92.56 361.21 9.75 0.015 ≤ DL 283.67 481.35 301.09 47.3 0.52 2.51 ≤ DL

Mouloud C 82.15 79.79 442.92 10.94 0.015 ≤ DL 188.86 686.89 336.51 79.6 0.425 2.73 ≤ DL

Mouloud 4 96.52 92.21 377.29 8.31 0.028 ≤ DL 177.47 625.53 329.03 75.78 0.615 2.56 ≤ DL

Dadin 3 46.96 26.37 217.5 5.07 0.03 ≤ DL 443.57 157.32 102.89 33.82 1.51 0.4 0.07

Cluster 1

Cluster 1 contains six samples that

characterize waters with low

mineralization (805 ≤ EC (μS / cm)

≤1464). This group corresponds to Na-

Cl-HCO3 water type. (South petit Bara

and Dadin)

Cluster 2

Cluster 2 contains twelve different water

samples characterized by moderate

mineralization. (Grand Bara-Mouloud)

Cluster 3

Cluster 3 contains four different water

samples characterized by very high

mineralization (4143≤ EC (μS / cm)

≤7731). This group correspond to Na-Mg-

Cl-SO4 water type (between GB and PB).



11

❖Groundwater Contaminations


➢Some of the groundwater analyzed present

high nitrate concentration (up to 50 ppm ;

WHO).

➢The lowest values are found in Petit Bara and

Dadin , while the highest values are found in Grand

Bara (up to 250mg/L in alluvium groundwaters from

boreholes #13 and #18; up to 150 mg/L in basalt

groundwaters from #11 and #12) and in the central

area (up to 120 ppm in #7 and #8).

➢It should be noted that people living in the

Republic of Djibouti are mostly nomad, and hence

have no agricultural tradition. The local nomads, who

raise goats and cheeps, do not have a fixed

settlement, hence not septic tanks.

➢Therefore, in many cases, natural soil might

contribute mainly for nitrate concentrations in the

study area as observed in some semi-arid or arid

regions over the world.

Thank you

Documents

Water resource situation of the Republic of Djibouti€¦ · Dalha basalts, the stratoid basalts and the Mabla rhyolites. Dalha basalts sequence Coastal plain sediments Integrating