Water resource situation of the Republic of

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).

❖ 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 2 Geological situations

❑ Geological Setting ❖ 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

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 3 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

Précipitation trends (1960 – 1990) 350 HOLL HOLL 300

250

200 1960 1965 1970 1975 1980 1985 1990

180

Précipitation(mm) 170 160 150 140 130 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.

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 4 Groundwater situation

❖Water resources demands ❖ The extreme climate condition explains the lack of permanent rivers, and has led the country to exploit the only Annual pumping rate millions m3/an 0 available water resources, which are 0.01 à 0.1 0.1 à 0.5 represented by groundwater in the 0.5 à 1 basaltic aquifer. 1 à 2 plus de 10 ➢ The population of Djibouti relies OBOCK !( heavily on groundwater resources for

TADJOURAH drinking water and irrigation purposes. !(

60

DJIBOUTI 51.0 Rural (population+bétail) 51.0 !( ARTA Urbain

!( Agriculture 40.8 Total 40.8

40

29.429.4

28.528.5

22.922.9 19.3 19.3 20

DIKHIL !(

15.215.2

15.215.2 Volume annuel.Million m3

!( Volume annuel.Million m3

12.512.5

3.23.2

2.62.6

1.71.7 0 2005 2010 2015

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 5 Groundwater situation

❖Groundwater degradations ➢ 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.

1984 1986 1988 1990 1992 1994 70

80 Mouloud

90

Water level m level Water 100 40

30

20

(mmol/l) - Cl 10 Djibouti 0 1960 1970 1980 1990 2000

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 6 Groundwater monitoring

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

Limnigraph

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 7 Geochemical characterization of the Bara volcano-sedimentary aquifer (Republic of Djibouti) : Case study ❖ 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.

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 8 Geochemical characterization of the Bara volcano-sedimentary aquifer (Republic of Djibouti) : Case study

Samples T Depth pH EC TDS Hydrochemical types ❖Groundwater Classification (°C) (m) (µS/cm) (mg/l) Petit Bara Zone Na-HCO -Cl ➢The groundwater have moderate to PK48 36 133 7.75 956.9 666 3 Na-HCO -Cl high EC values (from 957 to 4846 PK50 38 90 7.97 1127 795 3 Na-HCO -Cl S/cm), temperature values between PK51 39 135 7.75 1204 811 3 Na-Cl 27 and 43C, and moderately alkaline Didjander 28 170 7.96 2876 1617 Na-Cl pH ranging from 7.31 to 8.38. Omar Jakka 38 161 7.79 2958 2015 Naheel 39 155 6564 3668 Na-Cl-Ca Kourtimaley 37 165 7.8 7731 3254 Na-Cl-Ca ➢The Depth of the boreholes in this area ranges between 80 and 200 m Grand Bara Zone Na-Cl-Mg-Ca-SO Awraoussa 1 36 195 7.81 2692 1842 4 Na-Cl-Ca-SO Iskoutir 32 181 7.81 3258 2363 4 ➢Most of sampled groundwaters are Na-Cl-HCO -SO Gabla-galan 27 156 8.38 2200 1519 3 4 Na-Cl-Mg-Ca-HCO brackish (10 g/L  TDS  1 g/L) with Hambocto F2 35 190 7.26 1896 1329 3 Na-Cl-Mg-Ca-HCO the exception of several fresh waters Hambocto F1 38 150 7.31 1464 988 3 Na-Cl-Mg-SO (TDS  1 g/L) from North of Petit Doudoub Bololé F2 36 103 7.62 2337 1576 4 Na-Cl-Mg-SO Bara (#1–#4), Grand Bara (Hambocto Doudoub Bololé F1 41 93 7.48 4143 3173 4 Dagandalol 43 113 7.8 2871 1879 Na-Cl-SO4 F1) and Dadin3. Na-Cl-Mg-Ca-SO Dagaah-damere 39 170 7.71 4846 3484 4

Mouloud-Dadin Zone Na-Cl-Mg-SO Mindil 36 80 7.46 2630 1824 4 Na-Cl-Mg-SO Mouloud C 39 115 7.49 3035 2075 4 Na-Cl-Mg-SO Mouloud 4 39 140 7.33 2880 1965 4 Na-Cl-HCO Dadin 3 34 139 7.43 1388 980 3

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 9 Geochemical characterization of the Bara volcano-sedimentary aquifer (Republic of Djibouti) : Case study ❖Groundwater Classification ➢ Using statistical method (PCA and HCA) The geochemical data were classified into distinct groups according to the 2 +, 2 +, + +, ------common variables they share using 13 variables (pH, EC, TDS, Ca Mg Na , K HCO3 , Cl , SO4 , F , NO3 , Br ).

Ca Mg Na K Li NH4 HCO3 Cl SO4 NO3 F Br NO2 Site (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) Cluster 1 Petit Bara Zone Cluster 1 contains six samples that 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 characterize waters with low 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 mineralization (805 ≤ EC (μS / cm) 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 ≤1464). This group corresponds to Na- 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 Cl-HCO water type. (South petit Bara Naheel 215 231 852 11 0.2 0.43 95 1987 608 119 0.9 1.74 0.08 3 Kourtimaley 368 165 1080 32 ≤ DL ≤ DL 61 2410 572 122 0.245 1.78 0.008 and Dadin)

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 Cluster 2 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 Cluster 2 contains twelve different water 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 samples characterized by moderate ≤ DL ≤ DL Hambocto F2 115 66.78 169.53 4.98 0.0103 209.68 269.19 131.17 255.67 0.595 2.35 mineralization. (Grand Bara-Mouloud) 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 Cluster 3 Daagah-damere 199.28 123.44 653 15.30 ≤ DL 0.8 95 1271.5 486.5 62 0.09 5.29 0.21 Cluster 3 contains four different water

Mouloud Zone samples characterized by very high 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 mineralization (4143≤ EC (μS / cm) 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 ≤7731). This group correspond to Na-Mg- 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 Cl-SO4 water type (between GB and PB).

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 10 Geochemical characterization of the Bara volcano-sedimentary aquifer (Republic of Djibouti) : Case study ❖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.

Integrating Groundwater Management : 15-17 January 2019, Nairobi, Kenya 11 Thank you