North Western Sahara Aquifer System...

North Western Sahara Aquifer System (NWSAS) 2012 State of the Water Report

Donor: African Water Facility/African Development BankGrant Recipient: CEDAREAWF Grant Agreement No.: 5600155002351Project ID No.: P-Z1-EAZ-027Document Name: North Western Sahara Aquifer System (NWSAS) 2012 State of the Water ReportDocument Type: RegionalVersion: English, Final Version (V2)Countries: Algeria, Libya, TunisiaRegion: North Western Sahara Aquifer System (NWSAS) Main Authors: Khaled AbuZeid, Ph.D., P.E.; Mohamed Elrawady, M.Sc., CEDAREContributors: Mekki Hamza, Ph.D., Abdel Madjid Demmak, Ph.D., Abdulgader Abufayed, Ph.D.Design & Layout: Eng. Tamer El-HakimDocument Date: March, 2015

For reference purposes, this publication should be referred to as:AbuZeid, K., Elrawady, M., CEDARE (2015). “North Western Sahara Aquifer System (NWSAS) 2012 State of the Water Report”, Monitoring & Evaluation for Water In North Africa (MEWINA) Project, Water Resources Management Program, CEDARE.

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

2. NWSAS State of the Water (SOW) Indicators, Values, and Analysis . . . . . . . .9

2.1. Water & Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

2.2. Water & Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

2.3. Water & Land Use Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

2.4. Water & Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

2.5. Water & Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

2.6. Water & Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

2.7. Water & Governance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

2.8. Water & International Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

3. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Annex: The NWSAS Numerical Model (OSS, 2002) . . . . . . . . . . . . . . . . . . . . . . .40

List of Tables

Table 1. Summary of NWSAS Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Table 2. Water & Availability Indicator Values . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Table 3. Water & Uses Indicator Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Table 4. Evolution of Water Points in NWSAS . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Table 5. Water & Land use Changes Indicator values . . . . . . . . . . . . . . . . . . . . . .25

Table 6. Water & Population Indicator values . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

Table 7. Water & Quality Indicator Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Table 7a. Salinity of the IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

Table 8. Water & Eco-systems indicator values . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Table 9. Water & Governance Indicator Values . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Table 10. Water & International Relations Indicator Values . . . . . . . . . . . . . . . . .36

List of FiguresFigure 1. Geographical and Hydrological Extent of the Aquifer . . . . . . . . . . . . .8

Figure 2. Renewable and Non-Renewable Water Resources of NWSAS . . . . . . .11

Figure 3. MEWINA Countries Areas inside NWSAS Aquifer . . . . . . . . . . . . . . . .11

Figure 4. NWSAS Countries Potential Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Figure 5. Piezometric Heads of the IC Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Figure 6. Piezometric Heads of the TC Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . .14

Figure 7. Unconfined/ Confined surface interface for IC . . . . . . . . . . . . . . . . . . .15

Figure 8. Unconfined/ Confined surface interface for TC . . . . . . . . . . . . . . . . . .16

Figure 9. Map of the Top of the IC (Depth to Piezometric Surface) . . . . . . . . . .17

Figure 10. Map of the Bottom of the IC (Depth to the Bottom of the Confined Layer) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Figure 11. Extraction Zones of NWSAS in 2012 . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Figure 12. NWSAS Major Withdrawal Zones by Country . . . . . . . . . . . . . . . . . . .21

Figure 13. Historical Withdrawals from NWSAS (OSS, 2014) . . . . . . . . . . . . . . . .22

Figure 14. NWSAS Countries Withdrawals from Blue Groundwater . . . . . . . . . . .22

Figure 15. NWSAS Countries Withdrawals from Exploitable Non-Renewable Blue Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Figure 16. NWSAS Countries Average Draw-Down in 2012 . . . . . . . . . . . . . . . . . .24

Figure 17. Areas of High Risk of Depletion in the Aquifer Domain (OSS, 2014) 24

Figure 18. Irrigated and Rain-Fed agriculture in the NWSAS Domain . . . . . . . .27

Figure 19. Total Aquifer Bound and Dependent Population . . . . . . . . . . . . . . . . .28

Figure 20. Per Capita Share of renewable Groundwater and Groundwater Withdrawals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Figure 21. NWSAS Monitoring Network (Besbes and Horriche 2007) . . . . . . . . .31

Figure 22. Salinity Map of IC in 2012 (OSS, 2014) . . . . . . . . . . . . . . . . . . . . . . . . .32

Figure 23. Salinity Map of TC in 2012 (OSS, 2014) . . . . . . . . . . . . . . . . . . . . . . . . .33

Figure 24. Countries Dependencies on NWSAS. . . . . . . . . . . . . . . . . . . . . . . . . . .37

Figure 25. Other Shared Water Resources in NWSAS countries . . . . . . . . . . . . . .37

Figure 26. Other Water Resources in NWSAS Countries . . . . . . . . . . . . . . . . . . . .38

Figure 27. Cooperation Mechanism through OSS (Hamza, 2014) . . . . . . . . . . . .38

6 North Western Sahara Aquifer System (NWSAS) 2012 State of the Water Report

MEW

INA

1. IntroductionThe North-Western Sahara Aquifer System [NWSAS], shared by Algeria, Tunisia and Libya, is one of the largest underground North African transboundary aquifer water resources, and contains significant reserves of non-renewable water. The system covers a total area of more than one million km2.

Today and beyond, the waters of the M NWSAS groundwater resources are crucial to ensure food security for a growing population in the region, and beyond as well as meeting the needs of agriculture, inland aquaculture industry and strengthening infrastructure. The NWSAS system is hyrologically subdivided into two main Aquifers Systems as follows:

Sand Dunes in NWSAS (Libya)

a) Terminal Complex (TC)

This upper Aquifer system consists of three main geological formations:

• Mio- Pliocene sands (Misdah and Pontian respectively)

• Eocene carbonates

• Upper Cretaceous limestones

These different aquifer levels are hydro-dynamically linked, and relatively close.

The system Terminal Complex is characterized by:

7

Introduction


MEW

INA

• Proximity to artesian basin center

• A relatively shallow depth (100-600 m)

• A good average chemical composition of water on the edges and the center of the basin (also varying according to the geological horizon formation considered)

b) Intercalary Continental Infill (IC)

It is a multilayer aquifer system, represented by continental deposits of sandy clay of the Lower Cretaceous. It is characterized by:

• An important powerful central artesian basin in the center (20 to 30 kg / cm2 in the area of Wadi Rhir area),

• High depth (1500 to 2800 m in the Eastern Zone),

• A high water temperature of up to 60 ° above 70°C (77°C at Hazoua wells)

The NWSAS Hydrologic domain is shown in Figure.1 while table 1 shows the values of the basic parameters.

NWSAS Algeria


MEW

INA

Figure 1. Geographical and Hydrological Extent of the AquiferTable 1. Summary of NWSAS Characteristics

Surface Area 1,000,000 km2

Theoretical Reserve 30,000 BCM

Theoretical Recharge 1 BCM

Terminal Complex Recharge: 600 MCM* Average Thickness : 300m* Salinity: 2 to 5 g/l

Intercalary Continental Recharge: 400 MCM* Average Thickness: 50 – 1000m* Salinity: 1 to 4.5 g/l

Management measures in terms of scientific characterization studies of the NWSAS had started in the 1960s, and flourished in 1980s mainly between Algeria and Tunisia, while Libya joined later. The technical cooperation has gradually led to mutual confidence and recognition of the problems and risks affecting the aquifer system (OSS, 2008). Authorities in the three countries have decided in 1997 to carry out a joint study programme to ensure control over possible transboundary impacts (Mamou et al., 2006). In 1999, the project was launched and the Sahara and Sahel Observatory (OSS) was named as the Executive Agency in charge of the project. The first phase of the programme ended in December 2002 with an agreement to establish a “Consultation Mechanism” for the joint management of the NWSAS (Mamou et al., 2006). This mechanism further evolved in 2008 towards a permanent structure composed of: A Council of Ministers in charge of water resources in the three countries, a Steering Committee composed of the national institutions in charge of water resources in the three countries, a national Committee including other institutions concerned with water resources, users associations, non-governmental organizations , National and regional technical working, and a coordination unit led by a coordinator hosted at the OSS.

9

NW

SAS State of the Water (SO

W) Indicators, Values, and Analysis


MEW

INA

2. NWSAS State of the Water (SOW) Indicators, Values, and Analysis

The indicators’ categories for the Shared Aquifer SOW will consider two aspects, the first will address the Aquifer as one unit as if it is a country with its own state of the water indicators values, while the other will address the indicator values for different riparian countries. Unless otherwise mentioned, all indicators are applicable for the Aquifer as a whole and also for each riparian country.

2.1. Water & Availability

The main focus will be Blue Renewable and Non-Renewable Groundwater associated with a transbundary aquifer. In case of renewable aquifers, recharge rates will be presented if available. The indicators are as follows:

• Internal Renewable Groundwater (IRG): Groundwater Recharge is the total volume of water entering the aquifer

• Total Exploitable Non-Renewable Ground Water Resources: The annual extractable amount of non-renewable groundwater according to a pre specified safe yield that is dictated by a pre-specified sustainability period (x number of years) and a specific annual permissible drawdown.

• Country’s Area inside the Aquifer

• Potential Volume for Each Country: Based on the country’s area inside the Aquifer on the Aquifer’s total potential yield.

• Inflow to Each Country

• Outflow from Each Country

• Pieozometric Water Heads: Observed from observation wells

• Depth from Water to Basement/Confining Layer (Unconfined Aquifer): The vertical distance measured from the ground water table to the bottom of the unconfined water bearing formation which in some cases could be the top of a confining layer.

• Depth to Water Table (Unconfined Aquifer): The vertical distance from the ground surface to the water table in case of unconfined aquifers.

• Depth to Piezometric Surface (Confined Aquifer): The vertical Distance from the ground surface to the water level of the confined water bearing formation. It is worth mentioning that there are cases where more than one confined water bearing formation are present at different heights within the same vertical domain, and that there are cases where the piezometric surface is above the ground.

• Depth to bottom of Confined layer (Confined aquifer): The vertical Distance from the ground surface to the bottom of the confined water bearing formation.

The indicator values for this cateogory are shown in table (2)


MEW

INA

Table 2. Water & Availability Indicator Values

Units Whole Aquifer Algeria Libya Tunisia Notes

Water & Availability

Internal Renewable Groundwater (IRG) BCM/Year 1.1 0.6 0.27 0.2 OSS

Total Exploitable Non-Renewable Ground Water Resources

BCM/Year 7.745 6.102 0.946 0.697 OSS

Country’s Area Inside The Aquifer km2 (Mapped) 1,000,000 700,000 250,000 80,000 OSS

Potential Volume for Each Country BCM 30,000 20,388 7,282 2,330 OSS

Inflow to Each Country BCM/Year 0.6 0.3 0.2

Outflow from Each Country BCM/Year 1.975 0.296 0.551

Pieozometric Water Heads Meters (Mapped) Mapped

Depth from Water to Basement/ Confining Layer (Unconfined Aquifer)

Meters (Mapped) Mapped

Depth to Water Table (Unconfined Aquifer)

Meters (Mapped)

Depth to Pieozometric Surface (Confined Aquifer)


Depth to bottom of Confined layer (Confined aquifer)


One of the main specific characteristics of the NWSAS Aquifer system is its partial renewability. It is too significant and important for its countries to be utilized up to its rechargeable limit only. Figure (2) shows that 87.5% of the Annual available volume is non-renewable (7.75 BCM) based on a 50 years utilization period and a Draw down not exceeding 1.5 meters at the end of the utilization period.

The Countries area inside the aquifer are shown in Figure (3), it is clear that most of the Aquifer is occupied by Algeria, a fact that is well translated in the volume available for each country shown in Figure (4).

NWSAS Non-Renewable Petrified Trees (Libya)

11

NW




MEW

INA

Figure 2. Renewable and Non-Renewable Water Resources of NWSAS

Figure 3. MEWINA Countries Areas inside NWSAS Aquifer


MEW

INA

Figure 4. NWSAS Countries Potential Volume

The most important indicators that reflect the actual water availability in the NWSAS are the following:

a) Pieozometric Water Heads

b) Depth from Water to Basement/ Confining Layer (Unconfined Aquifer)

c) Depth from the ground surface Pieozometric Surface (Confined Aquifer)

d) Depth from the ground surface the Bottom of Confined layer (Confined aquifer)

Maps showing the values for the above indicators have been obtained from OSS for the year 2012 for both TC and IC.

Figure (5) shows the Pieozometric Water Heads for the IC Aquifer, while Figure (6) shows the same indicator for the TC Aquifer.

The piezometry of the IC aquifer shows that in the Western Basin, there is a total independence from the rest of the aquifer of the Eastern basin with a flow from the Saharan Atlas to the south and southwest. The piezometry of the TC aquifer shows that in the Oriental basin, the Lower Algerian-Tunisian Sahara helps in confining the groundwater flow forming an endorheic basin. The Marwan-Melrhir chotts in Algeria and Gharsa-Djerid chotts in Tunisia constitute the outlet of the aquifer and at the same time the area where the withdrawals by sources and wells are concentrated (OSS, 2012)

The map of Unconfined/ Confined surface interface is shown for IC in Figure (7) and for TC in Figure (8).

13

NW




MEW

INA

Figures (9) and (10) reflect the variable thickness of the Confined IC Aquifer as they show the maps of its Top and Bottom, respectively.

Figure 5. Piezometric Heads of the IC Aquifer


MEW

INA

Figure 6. Piezometric Heads of the TC Aquifer

15

NW




MEW

INA

Figure 7. Unconfined/ Confined surface interface for IC


MEW

INA

Figure 8. Unconfined/ Confined surface interface for TC

17

NW




MEW

INA

Figure 9. Map of the Top of the IC (Depth to Piezometric Surface)


MEW

INA

Figure 10. Map of the Bottom of the IC (Depth to the Bottom of the Confined Layer)

19

NW




MEW

INA

2.2. Water & Uses

The main focus will be direct abstractions from the shared aquifer of interest. The indicators are:

• Withdrawals from Blue Groundwater: Total abstractions from the aquifer

• Withdrawals from Exploitable Non-Renewable Groundwater: Total annual volumes abstracted from the non-renewable groundwater.

• Extraction Zones of the Aquifer: The different zones where clusters of extraction wells are present will be highlighted on a map.

• Annually Observed Drawdown: The decrease in Water levels in Groundwater wells as a direct result of extraction.

NWSAS Dependent Agriculture & Urbanization (Algeria)

NWSAS Dependent Agriculture in Libya


MEW

INA

NWSAS Dependent Agriculture in Tunisia

Table (3) shows the indicator values for the Water & Uses Category.

Table 3. Water & Uses Indicator Values

Units Whole Aquifer Algeria Libya Tunisia

Water & Uses

Withdrawals from Blue Groundwater BCM/Year 3.07 2 0.258 0.52

Withdrawals from Exploitable Non-Renewable Groundwater

BCM/Year 1.726 1.406 0 0.32

Extraction Zones of The Aquifer Numbers/ Mapped 10 3 5 2

Annually Observed Drawdown (Average & Mapped) Meters 1.41 2.05 1.07 1.12

There is lots of evidence of the increased dependency on NWSAS throughout time. The number of identified withdrawal points has increased from 8,800 in the year 2000 to 18,160 in 2008. The annual withdrawals, however, only increased by 0.32 BCM between the two aforementioned years as shown in table (4). The Total expected Withdrawal rate has been estimated to be 7.77 BCM in 2050.

Table 4. Evolution of Water Points in NWSAS

Country

Number of points and withdrawal rates per year Expected Withdrawal rate

2000 2008 2050

No. of points Withdrawal, BCM/year No. of points Withdrawal, BCM/year BCM/Year

Algeria 6,500 1.30 11,410 1.74 6.1

Libya 1,100 0.33 1,150 0.22 0.95

Tunisia 1,200 0.55 5,600 0.54 0.72

NWSAS 8,800 2.18 18,160 2.50 7.77

The total number of withdrawal points are shown for each country in table (4), It is of special concern to note that out of 5600 water withdrawal points available in Tunisia, only 80 wells have permits as will be shown in the “Water & Governance” Section.

21

NW




MEW

INA

Figure 11. Extraction Zones of NWSAS in 2012

Figure (11) shows the Extraction zones in 2012, they can be lumped into 10 major zones as shown in Figure (12). The history of withdrawals by the three countries is shown in Figure (13) up to the year 2012 and shows that the dependence of the three countries on NWSAS has increased asymptotically from 1950 to 1980 and drastically from 1980 onwards.

Figure 12. NWSAS Major Withdrawal Zones by Country


MEW

INA

Figure 13. Historical Withdrawals from NWSAS (OSS, 2014)

Figure 14. NWSAS Countries Withdrawals from Blue Groundwater

23

NW




MEW

INA

Figure 15. NWSAS Countries Withdrawals from Exploitable Non-Renewable Blue Groundwater

Figure (13) focuses on the withdrawals of the three countries in 2012, while Figure (15) specifies the withdrawals from exploitable non-renewable groundwater which is negligible in Libya but amounts to about 70% of the Total Withdrawals from NWSAS Blue Groundwater in Algeria and about 62% of the total Blue Groundwater withdrawals in Tunisia.

The average Draw down in the entire NWSAS domain has been assessed to be 1.41 m and varies from 1.05 to 2.05 in the three NWSAS countries as shown in Figure (16).

Based on the observed drawdowns, the locations and extraction zones under high risk of depletion have been determined and are shown in Figure (17), these areas include important touristic resorts in Tunisia and a strategic city in terms of development in Libya which is Sirt.


MEW

INA

Figure 16. NWSAS Countries Average Draw-Down in 2012

GhadamesJufrah

Bassin Occidental

Oued Mya

Bassin ArtésienSyrte

Exutoire TunisienChotts

Figure 17. Areas of High Risk of Depletion in the Aquifer Domain (OSS, 2014)

25

NW




MEW

INA

Tunisia Water Cooling System

2.3. Water & Land Use Changes

This category will focus on the Land Use within the Aquifer’s geographical domain, the indicators are as follows:

• Total Irrigated Agricultural land: Total water managed agricultural area in the basin • Total Rainfed Agricultural land: The total rainfed agricultural area • Total Pasture area• Total Forests area• Urban Encroachment on Agricultural land: Is the loss of agricultural land caused by urbanization,

and is expressed by agricultural area lost/ year• Impact of Urban Encroachment on agricultural land: Is the amount of water resources gained or

lost due to urban encroachment on agricultural lands and is assessed through the following indicators: The Decrease in Groundwater Recharge caused by Urban Encroachment: defined as total volume of water that would have naturally entered underground sources of water (typically aquifers) in the urbanized areas from endogenous (internal) precipitation and surface water flow, had urbanization not taken place (FAO).

Table (5) shows the indicator values for the Water & Land Use Changes Category.

Table 5. Water & Land use Changes Indicator values


Water & Land Use Changes

Total Irrigated Agricultural Land ha 270,000 202,000 30,000 38,000

Total Rainfed Agricultural Land ha 102000 133,300

Total Pasture Area ha 23140 2,377,150

Total Forests Area ha 0 0 0

Urban Encroachment on Agricultural Land ha/Year 250 insignificant

The Decrease in Groundwater Recharge caused by Urban Encroachment

BCM/Year 0.00013 insignificant


MEW

INA

NWSAS Dependent Urbanization in Algeria

NWSAS Dependent Urbanization in Libya

NWSAS Dependent Urbanization in Tunisia

27

NW




MEW

INA

The assessment of land use and its changes along the NWSAS domain is of great importance as it provides significantly important information regarding the change in withdrawals and draws trends for the future. As the agricultural sector is the highest water consumer in the three NWSAS countries, assessing the total area of irrigated areas is important to estimate future agricultural dependency on the Aquifer, whereas the increase of the total area of rain-fed agricultural areas could draw expectations that such agricultural dependency on the NWSAS Aquifer might decrease. The Irrigated and Rain-fed agricultural areas in the NWSAS domain are shown by country in Figure (18)

Figure 18. Irrigated and Rain-Fed agriculture in the NWSAS Domain

Another very important indicator related to land use is the Urban Encroachment on Green Cover not only because it traces the decrease in the areas of green cover, but because it also detects the associated change in water withdrawals and consumptions. The Urban Encroachment on green cover amounted to 250 Hectares in 2012 in Libya and the associated decrease in Groundwater recharge as a direct result of that urban encroachment was estimated to be 0.13 MCM.


MEW

INA

2.4. Water & Population

This category will feature different demographical data about a particular aquifer, if the total aquifer-bound population is known. The indicators are as follows:

• Total Population: Total Aquifer bound population

• Internal Renewable Water Resources per Capita: Recharge of the aquifers generated from endogenous precipitation, on a per person basis (Modified from FAO).

• Groundwater Water Withdrawal per Capita: Total annual abstractions from groundwater sources including non-renewable groundwater, on a per person basis (modified from FAO).

Table (6) shows the indicator values for the Water & Population Category.

Table 6. Water & Population Indicator values


Water & Population

Total Aquifer bound and dependent population Number 4,626,517 2,046,517 1,480,000 700,000

Internal Renewable Water Resources Per Capita CM/Capita 238 293 182 286

Groundwater Withdrawal Per Capita CM/Capita 664 977 372 743

Renewable Water Resources per Capita (for the whole country population)

550 3,750 1,585

The total Aquifer dependent population amounts to 4.62 Million inhabitants, those are the population who dwell in the Aquifer’s domain and/or have certain aspects related to their well-being and livelihoods directly related to it. Figure (19) shows the total Aquifer bound and dependent population in the three NWSAS countries.

Figure 19. Total Aquifer Bound and Dependent Population

Figure (20) shows the per capita share of renewable groundwater within the aquifer’s domain and the per capita share of actual groundwater withdrawals. It is clear from the figure that Libya is the only country that depends on the renewable volume of the system which is in good agreement with Figure (15), while the per capita withdrawal in Algeria and Tunisia significantly exceeds the renewable withdrawal.

29

NW




MEW

INA

Figure 20. Per Capita Share of renewable Groundwater and Groundwater Withdrawals


MEW

INA

2.5. Water & Quality

The following indicators are to be assessed in different areas within the Aquifer’s domain:• Chloride Concentration• Nitrate Concentration• Electric Conductivity• Total Dissolved Solids• Fluoride Concentration.

Table 7. Water & Quality Indicator Values


Water & Quality

Concentration of Chloride in The Aquifers Domain

PPM/ Mapped 2500 2500 2500 2500MEWINA Algeria

Nitrate Concentration PPM/ Mapped

Electric Conductivity 1/OHM (S/M)

Total Dissolved Solids PPM/ Mapped 180-32,700 180-32,700 684-9,950 800-10,320 OSS (Mapped)

Fluoride Concentration PPM/ Mapped

Water Quality Monitoring has always been an important priority to the NWSAS countries, the full monitoring network is shown in Figure (21)

Water quality varies between the TC and IC. Based on historical records, the TDS concentration varies from below 180 mg/l to 10,320 mg/l in the IC and from 411 mg/l to 32,700 mg/l in the CT with anomalies existing due to intensive mining, irrigation water return, and surface water recharge.

A summary of Total Dissolved Solids data for the IC collected from 4000 water points distributed in the three riparian countries is presented in table (7a). It can be seen from this table that the salinity for most samples in IC groundwater is 1.5-4 g/l in Algeria, 1.5-4 g/l in Tunisia, and is less than 2 g/l in Libya. Salinities exceeding 1 g/l limits water use for domestic purposes.

Figures (22) and (23) show the salinity maps of IC and TC, respectively, in 2012.

Table 7a. Salinity of the ICCountry No. of

samplesSalinity class, TDS (mg/l)

0 - 1 1 – 2 2 - 3 3 – 4 4 – 5 5 - 10

Libya 124 1 95 10 8 6 3

% (0.9%) (76.7%) (8.2%) (6.5%) (4.9%) (2.5%)

Algeria 226 0 7 87 68 50 13

% 0 (3.1%) (38.5%) (30.1%) (22.1%) (5.8%)

Tunisia 286 131 97 36 8 6 8

% (45.8%) (33.9%) (12.6%) (2.8%) (2.1%) (2.8 %)

31

NW




MEW

INA

Figure 21. NWSAS Monitoring Network (Besbes and Horriche 2007)


MEW

INA

Figure 22. Salinity Map of IC in 2012 (OSS, 2014)

33

NW




MEW

INA

Figure 23. Salinity Map of TC in 2012 (OSS, 2014)


MEW

INA

2.6. Water & Ecosystems

The following indicators are to be assessed within the Aquifer’s domain:• Number of Groundwater Based Ecosystems • Number of RAMSAR Wetlands in The Aquifer Domain • Number of Endangered Species • Number of Invasive Species

NWSAS Dependent Kabraun Lake in Libya

Table (8) shows the indicator values for the Water & Eco-systems Category

Table 8. Water & Eco-systems indicator values


Water & Ecosystems

Number of Groundwater Based Ecosystems Number 19 8 11

Number of RAMSAR Wetlands in The Aquifer Domain Number 7 0 7

Number of Endangered Species Number

Number of Invasive Species Number

As far as ecosystems are concerned, there are 8 Sebkhas and national parks in Libya, as well as natural reserves and many wadis, springs, and oasis. There are also 11 Groundwater based Eco-systems along the NWSAS Domain in Tunisia as well as 7 RAMSAR accredited wetland sites.

35

NW




MEW

INA

2.7. Water & Governance

The following indicators are to be assessed within the Aquifer’s domain:

• IWRM Plan (Yes/No): The Presence of a plan for the whole Aquifer or the presence of individual country plan related to the country’s part in the Aquifer.

• Well Permits to date: The total number of Authorized wells

• Volumetric Groundwater Rights: The Total Volume of Groundwater Rights associated with all well permits

• Unlicensed Groundwater Abstractions: Defined as the difference between the total volume of withdrawals and the Volumetric Water Rights.

Table (9) shows the indicator values for the Water & Governance Category

Table 9. Water & Governance Indicator Values


Water & Governance

IWRM Plan (Yes/No) Yes/No yes No

Well Permits to date CM/Capita 80

Volumetric Groundwater Rights BCM/Year 0.0135

Unlicensed Groundwater Abstractions BCM/Year 0.222

There are currently 80 wells permits issued in 2012 in the NWSAS domain in Tunisia, with volumetric rights amounting to 13.5 MCM annually. The unlicensed abstraction, however, amounts to 222 MCM annually. The total number of withdrawal points are shown for each country in table (4), It is of special concern to note that out of 5600 water withdrawal points available in Tunisia, only 80 wells have permits.

2.8. Water & International Relations

The following indicators are for countries only, and not for the Basin as a whole:

• Dependency Ratio: The percent of annual volumes abstracted from the Basin of interest to total annual available water resources.


MEW

INA

• Shared Waters related Bilateral/ Multilateral Agreements and/or Memorandums of Understanding and Cooperation Mechanisms: The number of Bilateral or Multilateral agreements or other sort of cooperation a particular country is involved in. These agreements should be solely intended for transboundary water resources related to NWSAS.

• Presence of Other Shared Water Bodies in Riparian Countries

• Presence of other Water Resources: The total volume of Renewable Water Resources available annually to each Riparian country from sources other than NWSAS

Table (10) shows the indicator values for the Water & International Relations Category

Table 10. Water & International Relations Indicator Values


Water & International Relations

Dependency Ratio of Each Riparian Country % NA 2 0.94 2.9

Bilateral / Multilateral Agreements & Cooperation Protocol or MOUs Between Riparians

Number NA 1 1 1

Presence of Other Transboudray Bodies in Riparian Countries

Number NA 3 2 2

Presence of other Water ResourcesBCM/Year

22.54 22.98 16.884

International Relations are an essential aspect in any shared water body. The strategic importance of a particular water body to any country is dictated by the degree of dependency of that country on that shared water source. Figure (24) reflect the low dependencies of Algeria, Libya, and Tunisia on NWSAS due to the fact that the tree countries enjoy significant annual volumes of green water which is defined as the direct beneficial consumptions from precipitation by Rain-fed , pasture, and forests area. Such volumes of Green Water contribute positively to the overall annual available water resources and therefore play a role in diminishing the annual available NWSAS volumes in comparison to the total available water resources.

Another important aspect related to the significance of a particular water body to each country in terms of political relations is the presence of other shared water resources. Figure (25) shows the other shared Water Resources in NWSAS countries. Algeria shares the Rachidia Basin with Morocco, the Tindouf Aquifer with Morocco and Mauritania, the Taoudeni Basin with Mali and Mauritania, the Djado- Mourzouk Basin with Chad, Libya and Niger, the Aire Cristalline Aquifer with Mali and Niger, the Tin Serinine Basin with Niger, and the Medjerda River Basin with Tunisia. Tunisia also shares the Djeffara plain with Libya, and the Medjerda River with Algeria. Libya in turn shares the Nubian Sand Stone Aquifer System with Chad, Egypt, and Sudan, the Djado- Mourzouk Basin with Chad, Niger, and Algeria, and Djeffara plain with Tunisia.

Figure (26) shows the total volume of Renewable Water Resources for each NWSAS country excluding the Renewable Blue Water Resources within the NWSAS system. It is clear that the three countries have relatively close values.

37

NW




MEW

INA

Figure 24. Countries Dependencies on NWSAS

Figure 25. Other Shared Water Resources in NWSAS countries


MEW

INA

Figure 26. Other Water Resources in NWSAS Countries

The Sahara and Sahel Observatory (OSS) is a great example of cooperation between NWSAS Riparians. It was named as the Executive Agency in charge of the project. The first phase of the programme ended in December 2002 with an agreement to establish a “Consultation Mechanism” for the joint management of the NWSAS (Mamou et al., 2006). This mechanism further evolved in 2008 towards a permanent structure composed of: A Council of Ministers in charge of water resources in the three countries, a Steering Committee composed of the national institutions in charge of water resources in the three countries, a national Committee including other institutions concerned with water resources, users associations, non-governmental organizations , National and regional technical working, and a coordination unit led by a coordinator hosted at the OSS. Figure 27 shows the Institutional Organogram of NWSAS.

Figure 27. Cooperation Mechanism through OSS (Hamza, 2014)

39

References


MEW

INA

3. ReferencesAbuFayed, 2014, State of the Water in the North Western Sahara Aquifer, MEWINA Libya Unit

OSS, 2014, Maps for the State of the Water in the North Western Sahara Aquifer, MEWINA Tunisia Unit –OSS.

CEDARE (2014), “North Western Sahara Aquifer System (NWSAS) M&E Rapid Assessment Report”, Monitoring & Evaluation for Water In North Africa (MEWINA) Project, Water Resources Management Program, CEDARE.

Dammak, 2014, State of the Water in the North Western Sahara Aquifer, MEWINA Algeria Unit

Hamza, 2014, State of the Water in the North Western Sahara Aquifer, MEWINA Tunisia Unit

Mamou, A., Besbes, M., Abdous, B., Latrech, D.J., and Fezzani, C. (2006), “North Western Sahara Aquifer System (NWSAS).” In Non-Renewable Groundwater Resources - A guidebook on socially-sustainable management for water-policy makers (eds. S. Foster and D.P. Loucks), 68-74. UNESCO, Paris.


MEW

INA

Annex: The NWSAS Numerical Model (OSS, 2002)

The knowledge of hydrogeology in the Algerian, Tunisian and Libyan Sahara was synthesized and a conceptual model was drawn up. The structure adopted includes four aquifer layers: The Terminal Complex, the Turonian, The Intercalary Continental (with the upper sandstones in Tunisia) and The Cambro-Ordovician (COD), separated by three aquitards: the lagoon Senonian, the Cenomanian and the Carboniferous. The used software is the PMWIN (PM5 version)

The period taken as reference for steady-state calibration of the model is 1950, considered as a state of equilibrium. The period 1950-2000 was adopted as the reference period for the model calibration in transient state.

Piezometric Map of the Terminal Complexbasins

Pizometric Map of the IntercalaryContinental basins

Western basin

Eastern basin

Central basin

Source: OSS, 2002

a) The exploratory simulations:

The exploratory simulations enable us to assess the ability of the NWSAS to achieve the three countries objectives for water resources demand and to define how far we can go in abstracting water resources.

The exploratory simulations are run for 50 years, the initial reference state being the year 2000 state as reproduced by the model. A reference scenario called the “Zero simulation”, which consists of keeping the year 2000 withdrawals rates and calculating changes in the system over the next 50 years (year 2050) was run.

Following this reference scenario, several other scenarios were performed.

b) Results of the exploratory simulations:

b1) Scenario zero: maintenance of current situation

This simulation is the indispensable reference for estimating the effects of any likely additional withdrawals from the system.

41

Annexes


MEW

INA

Drawdowns are calculated by reference to the piezometric levels reproduced by the model in the year 2000. The figures below show the drawdown map in the IC and TC layers in the year 2050

In this case, the 2000 year withdrawals will be kept constant in all three countries as follows:

Country Water bearing layers The Year 2000 Withdrawals (MCM)

Tunisia

IC 81

TC 455

Total 1 536

Algeria

IC 856

TC 698

Total 2 1,554

LibyaTotal 3 602

GRAND TOTAL 2,692

With this scenario, the drawdown (IC layer) will not exceed the 30 m in the transboundary region (Ghadames -Debdeb- Borj El Khadra). The Tunisian outlet discharge (El Hamma) will drop from 1.54 to 0.94 CM/s.

Scenario zero: Drawdowns (m) in the IC layer (Year 2050)


MEW

INA

Scenario zero: Drawdowns in the TC layer (Year 2050)

With this scenario, the drawdown (TC layer) in Tunisia will vary from 5 to 30 m (Year 2050).

b2) High – scenario in the IC water bearing layers:

This scenario simulates an additional abstraction of 129 CM/s in the IC layer distributed as follows:

• Algeria : 118.5 CM/s

• Tunisia : 2.2 CM/s

• Libya : 8.35 CM/s

With this scenario, the drawdown will exceed 200 m in Borj El Khadra (Year 2050). The Tunisian outlet discharge “El Hamma” will drop to 0.13 CM/s and an additional drawdown in Nefzaoua – Djerid of 30 – 50 m is expected.

43

Annexes


MEW

INA

Drawdowns (m) in the IC layer

Drawdowns (m) in the TC layer (high scenario)

b4) Ghadames-Debdeb-Borj El Khadra Scenario:

This scenario simulates an additional abstraction of 6.35 CM/s from the IC layer distributed as follows:• Libya : 2.85 CM/s

• Algeria : 2.8 CM/s


MEW

INA

• Tunisia : 0.7 CM/s

In this scenario, the expected drawdowns are very high. It will reach about 200 m in Ghadames (Libya), Debdeb (Algeria), and Borj El khadra (Tunisia). The Tunisian outlet discharge “El Hamma “which feeds the Djeffara aquifer will drop to 0.13 CM/s. Artesianism will disappear in some Algerian zones.

Drawdowns (m) in the IC layer (2050 year)

Through various simulations and scenarios, the NWSAS model which is supplied from the database and the Geographic Information System has allowed:

• to improve knowledge of the basin

• to highlight zones that require additional study

• to identify risks

• to demarcate the most vulnerable zones

However the intensive withdrawals from the NWSAS non-renewable groundwater in the most vulnerable zones (chotts) involves three main types of risks:• Salinization of the aquifer by chotts flow reversal;

• Excessive well depths implying high cost of drilling and pumping;

• Drying up of natural outlets.

These risks, obviously, are not all equally serious; the first is the major one. A decision- maker might agree to increases in pumping costs, but should categorically avoid the risk of salinization by chotts, because it is irreversible.

45

Annexes


MEW

INA

Salinization of the aquifer by reversal flow of the chott

North Western Sahara Aquifer System...

Documents

Transcript of North Western Sahara Aquifer System...