GROUNDWATER AS PART OF THE WORK OF LAKE CHAD BASIN ...

BACKGROUND
GROUNDWATER AS PART OF THE WORK
OF LAKE CHAD BASIN COMMISSION (LCBC)
Presented by
Engr. Muhammad Sani ADAMU
Executive Secretary
Lake Chad Basin Commission
N’Djamena, Chad
Situated in the eastern part of the Sahel region of Africa, at the southern edge
of the Sahara desert, Lake Chad and its active basin constitutes an important
freshwater resource shared by Cameroon, the Central African Republic, Chad,
Niger and Nigeria. The surface area of the lake varies considerably with the
amount of annual rainfall, and the recent historical variation in the surface area
of the lake has ranged from approximately 25,000 to 2,000 km2. Lake Chad is
Africa’s fourth largest lake (in terms of surface area) after Victoria, Tanganyika
and Nyassa.
Lake Chad is shallow – its average depth being 1.5 m – and is of relatively
small volume. Two of Lake Chad’s tributaries, the Chari and Logone rivers,
supply approximately 95% of the Lake’s surface water input. The lake is
subject to considerable evaporation and yet is not saline. For thousands of
years Lake Chad has been a centre of development, trading and cultural
exchange between the people’s living to the north of the Sahara and those to
the south. Today close to thirty million people depend for their livelihood on
activities carried out in the lake and its active basin which includes important
wetlands and floodplains covering 966,955 km2. The main economic activities
of the people in the basin include fishing, farming, animal husbandry, mining
and commerce.
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The geological and geo-morphological development of the basin has been
conditioned by the slow and ‘’cool’’ rifting of the West and Central African Rift
System which has formed a regional hydrological sink – the Lake Chad water
body. The contributing sub-basins are underlain by basement complex in the
supper source areas and by a progressively thick sequence of sedimentary
deposits towards the lake.
The hydro-stratigraphy in the sedimentary aquifers underlying the lake are only
partially understood and the hydro-dynamic linkages to the Lake Chad water
body are therefore conjectural. However, it is apparent that the close
interaction between rainfall, evaporation, the generation of lateral inflow to the
lake and the groundwater leakage under the body of the lake influence the
overall lake balance. A distinction has to be made between hydrological and
hydro-geological context of each influent tributary, and the aggregate water
balance of Lake Chad itself. Equally there is a marked distinction between a
humid period (prior to 1973) and the current drought regime that has persisted
over the three decades.
The significant feature of the hydrological context is the persistent change in
the rainfall patterns over the basin as a whole. In the last 30 years isoheytal
contours of mean rainfall have shifted to the south by an order of several
hundred kilometers. The results of this shift are that areas that had
experienced a mean rainfall of 320 mm (for example) now receive les than 210
mm. in the hydrological active upstream basins, this large decrease in mean
rainfall per annum has brought about a proportionally larger decrease in the
basin yield, as river runoff, effluent groundwater flow, and flow thresholds are
greatly reduced. This persistence in the rainfall regime is therefore resulting in
a very attenuated basin yield and has to be set against burgeoning human
demands upon the land and water resources of the system generally.
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For the realization of the socio-economic potentials of the Lake Chad Basin,
four riparian States of the Lake Chad, namely Nigeria, Niger, Cameroon and
Chad signed a Fort-Lamy (now N’Djamena) Convention on 22 nd May 1964
formally creating a Lake Chad Commission with a broad mandate of drawing
up, managing and implementing economic development projects, Integrated
Water Resources Management conflict resolution among States, and
promotion of regional integration, cooperation and security. In 1987 the
Summit of the Heads of LCBC Member States (the highest decision-making
body) decided to restructure LCBC. The restructuring programme was
supported by UNDP and has been implemented since 1990. The resulting
structure is a light organization that focuses on transboundary activities with
emphasis on the integrated management of land, water and other natural
resources of the Lake Chad Basin.
At the time of is creation, the mandate of LCBC covered an area referred to as
‘’Conventional Basin’’ of 427,300 sq.km, representing only about 18% of the
hydrological basin. This conventional basin therefore excludes the largest
desert expanses of Algeria, northern Niger, Libya and Sudan. In particular it
also excluded the upstream part of the active basins of the Chari-Logone and
Komadugu-Yobe River Systems.
But with the adhesion of Central African Republic in 1994 as the 5 th member of
LCBC, the Conventional Basin has been enlarged to include the upper basin
of the main river systems of Chari-Logone-El Beid and Komadugu-Yobe
covering a total of area of 966,955 sq.km. The Conventional Basin will further
be enlarged with the adhesion of Libya in 2007 and the expected adhesion of
Algeria and Sudan to Lake Chad Basin Commission.
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Current trends
Climate change is regarded as the most important global change relevant to
the Lake Chad Basin. In the past 30 years, the Sahel has experienced the
most substantial and sustained decline in rainfall recorded anywhere in the
world. Since 1971, the average of all stations fell below the 1989-year average
and showed a persistent downward trend since 1951.
A comparison of isohyets of the 1950s, which is regarded as the wettest
decade, with the driest in the 1980s showed considerable shift towards the
south (Olivry et al. 1996). In particular, the 400 mm isohyets moved 200-250
km towards the south in the west of the Lake Chad, 100 km towards the south
in the east but only few tens of kilometers in Ouaddai (Chad).
The 1800 mm isohyets shifted by 300 km to the south at the longitude of
Guera and by 200 km to the south east of Guera, in Nigeria. The reduction in
rainfall was about 100 mm for each 100 km of distance apart from the annual
and spatial variations (LCBC 2000b). The shift showed that areas that had
experienced a mean rainfall of 320 mm (e.g. over the lake itself) received less
than 210 mm (World Bank 2002b)
The dramatic decrease in the surface area and volume of Lake Chad has been
attributed to regional and global climate change as well as water management
practices. Climate change thus remains a major determinant of the future of
the lake’s volume and surface area. This is in addition to having serious
implications for the availability of fresh water in the basin, resulting in
competition, conflicts and migrations.
Climate change has also impacted, and is still impacting on vegetation cover.
There has been a general decline and disappearance of large trees and
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woody species with declining rainfalls, as well as the disappearance of
perennials of the field layer. But the effects on vegetation did not exactly
parallel the shifts of the isohyets, as soil types also had major effects in
maintaining the status quo or in accelerating the rate of degradation, as do the
effects of man and animals. Continuing degradation of the vegetation cover
will have immediate direct implications for agriculture and livestock rearing.
Already the north part of the hydrological basin is experiencing desertification
at the rate of 2-3 km/annum southwards of the basin.
Problems of the Lake Chad Basin
The key attribute of the Lake Chad Basin is its importance as a source of fresh
water for a population of about 30 million spread across six countries:
Cameroon, CAR, Chad, Niger, Nigeria and Libya. Apart from the problems
resulting from climate change, the major transboundary problems of these
countries related to the interactions between water resources and their society
in the Lake Chad Basin which are:
1. Variability of hydrological regime and fresh water availability
2. Decreased viability of biological resources
3. Loss of biodiversity
4. Loss and/or modification of ecosystems
5. Sedimentation in rivers and water bodies
6. Invasive species
7. Other environmental degradation (soil erosion, pollution, etc.)
8. Migration, refugees, farmers/transhumance conflicts.
Other problems of the basin may be political (governance), economical and
cultural which will not be discussed here. But the problem of managing the
water resources is of course very important which needs to be highlighted
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here. Integrated water resources management in the Lake Chad, whether it is
at national or regional level, has been very much hampered by the following
facts which are still prevailing in the region:
1. Bad management practices
2. Poor decision-making
3. Poor data management
4. Absence or poor monitoring systems
5. Absence or poor conservation policies and/or systems
6. Lack of contingencies planning and resources mobilisation
7. Lack of Focus on part of Managers
8. Deficient legal framework (laws, regulations, guideline tariffs, etc)
9. Weak coordination among sectors at national and regional levels
10. Weak and persistent rural economy of Member States of LCBC
11. Poor stakeholders’ participation.
Therefore for Lake Chad Basin to achieve its common Vision 2025 where land,
water and all natural resources are conserved, sustainably exploited, managed
in an integrated manner and shared equitably, in order to ensure poverty
eradication, improved living standard in peace and security, these
predicaments must be overcomed. It therefore follows that LCBC now facing
the following challenges:
1. Environmental degradation
2. Resources management
3. Competition over access to diminishing resources
4. Deep poverty of the populace.
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In order to overcome these challenges, the LCBC with the assistance from
other stakeholders and development partners has mapped out the priority
areas for action as follows:
1. All stakeholders participation
2. Development of IWRM at both national and Basin levels
3. Capacity building involving all stakeholders
4. Assessing and conservation of resources both on the surface and
under the ground
5. Recharging the Lake Chad and other wetlands in the Basin
6. Poverty reduction
7. Promotion of regional security and economic integration.
FRAMEWORK FOR ACTION
Mobilization of political will and ensuring good governance is fundamental to
the realization of the objectives of the vision. It is necessary to have a broad
based support and commitment of all the basin’s stakeholders, donors and
technical support agencies so that sacrifices and investments can be made to
achieve the desired visions goals. This calls for dissemination of information
particularly on the vision itself.
It is in this spirit that the following actions are being done by all stakeholders at
all levels including leaders of the riparian states
1. Campaign to save Lake Chad Basin (launched since 1994)
2. Engaging the Parliamentarians
3. Engagement of political and traditional leaders of the Basin
4. Establishment of Inter-Ministerial Committee (IMC) in the Member
States
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5. Adoption of Vision, Master Plan, Strategic Action Plan and
Programme
6. Implementation of key projects.
These key projects are geared towards the preparation of Strategic Action
Programme, improving the knowledge management capacity of LCBC,
recharging the basin wetlands (IBWT) as well as assessment of the
underground water potentials in the Lake Chad Basin.
For quite a long time since before the creation of the Lake Chad Basin
Commission in 1964, groundwater all over the Lake Chad Basin has been
exploited for water supply, animals’ consumption and to a lesser extent for
industrial use. But there has never been an attempt to assess the quantity,
quality and location of underground water, except recently when LCBC and
some stakeholders started to think of the idea as an alternative to the
diminishing surface water of the basin. So far LCBC has carried out few
projects on underground water assessment since its inception. Notable studies
carried out in the last four decades, includes:
1. Survey of groundwater resources in the Lake Chad Basin which
was carried out between May 1967 and 1972 with assistance from
UNDP and FAO. It deals with the survey of groundwater conducted
with a view to supplementing and, above all, extending present
knowledge regarding the resources available in the Lake Chad Basin.
The work done involved mainly the exploration of various known or
assumed aquifers. It made possible, in particular:
- to determine the limits of artesian activity and the extent of the
lower Pliocene aquifer in Cameroon and Chad
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- to discover in these countries the existence of deeper artesian
water resources, attributes to the terminal continental
formation, and to evaluate the extent of this aquifer in the Chad
Basin
- to discover in Niger the existence of deep aquifer attributed to
the Hamadian continental and intercalated continental
formations respectively and to give a first assessment of their
extent
- to increase the data available leading to an improved
knowledge of the general phreatic aquifer
- to specify that chemical composition of the groundwater makes
it unsuitable for irrigation, except possibly in the north of the
Conventional Basin.
Particular recommendations are given for each aquifer and for
each country. They regard:
- the establishment under the aegis of the LCBC of a network for
observing fluctuations in and the dynamic properties of the
phreatic aquifer;
- the control of utilization of the limited resources of the lower
pliocen aquifer;
- the exploitation, in conjunction with the surveying of the
terminal continental aquifer in Cameroon, Nigeria and Chad;
- the utilization of the aquifers in the Hamadian continental and
the intercalated continental formations.
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This project produces two main documents:
- Hydro-geological study
- Drilling investigations and data
2. Monitoring and management of groundwater resources in the
Lake Chad Basin
This project was funded by the ‘’Fonds d’Aide et de Coopération de
la Rération de la République Francaise’’ between 1991-1993. The
studies were carried out by BGRM within the framework of the
LCBC/M003/91 Contract, concluded between the Lake Chad Basin
Commission and the BRGM.
The aim of this project is to provide the Lake Chad Basin
Commission (LCBC) with new tools for the management of
groundwater resources, namely:
- In the first stage ‘’the design and definition of a piezometric
network, updating of data and implementation of an aquifer
surveillance system’’ and the proposition of a system of
quantitative and qualitative monitoring and control of
groundwater in the Conventional Basin;
- In the second stage ‘’Modeling of aquifer, resources evaluation
and simulation of exploitation’’ with the characterization by a
grid-numerical modeling of the two principal aquifer systems
exploited in the basin. It results in the installation at LCBC
Headquarters in N’Djamena of two models allowing the
simulation of exploitation in each aquifer.
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As a conclusion this project reiterates the pressing need for
rational management of groundwater resources in the Lake
Chad Basin. It also recommended the controlling of artesian
losses from the confined aquifers. Finally, brief mention was
made of the various studies and installations dealing with
groundwater resources which could be carried out in the future
under the auspices of LCBC.
3. Management of groundwater resources for the sustainable
development of the Lake Chad Basin
Within the framework of UNESCO/LCBC and with the BMZ financial
support, this project was carried out between July 1997-December
2007 with the objective to contribute to the better management and
planning of water resources and to the development of manpower
infrastructure and aimed at the establishment of a simulation model
to characterize the upper aquifer behavior under three different
climatic scenarios to facilitate groundwater resources management in
the Lake Chad.
Activities implemented
Within the framework of the project and with the objective of
improving the knowledge of the aquifer system, the following
activities have been conducted:
- An inventory of control points for piezometer head values (a
piezometer is a borehole drilled to measure the fluctuating
water level or ‘’head value’’ of groundwater) covering an area
in both Chad and Cameroon, that was conducted in May of
1998, during which 7 new boreholes were installed and 10 old
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ones were restored. These control points were also used for
the determination of hydraulic and hydro chemical parameters;
- Two surveys of head values using 374 control points: one
piezometric survey was conducted at the end of the dry season
(April – June 1998 and 1999) and the other at the end of the
wet season (December – January 1998-1999 and 2000) to
measure the difference in water levels between dry and wet
seasons;
- Two water samples collection campaigns for chemical
analyses: one coinciding with the end of the dry season of
1998, and another with the end of the wet season of 1998­
1999. Each campaign consisted of the collection of 100 water
samples for chemical analyses, 75 for the determination of 18 O
and Deuterium ( 2 H), and 58 samples for the determination of
Tritium ( 3 H) contents;
- The different hydrological units (Quaternary or ‘’upper aquifer’’)
Lower Pliocene or ‘’intermediate aquifer’’ and Continental
Terminal or ‘’Lower aquifer”) were spatially defined;
- Hydraulic parameters (transmissivity characterizing the ability
of am aquifer to drain water, storage coefficient characterizing
the capacity of the aquifer to store water, etc.) were
established from data obtained with pumping tests conducted
within the framework of the project;
- Hydrological modeling of the upper aquifer;
- Simulations of the upper aquifer behavior were conducted
under three different climatic scenarios (dry, medium, wet).
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Objectives achieved or to be achieved in the near future
Within the framework of UNESCO/LCBC and with the BMZ
financial support, the project ‘’Management of Groundwater
Resources for the Sustainable Development of the Lake Chad
Basin’’ has been carried out with the main following objectives:
- Knowledge and quantification of water resources and recharge
in the upper aquifer under three climatic scenarios (medium,
dry and humid), as well as its suitability in terms of quality for
various uses such as water supply and irrigation;
- Evaluation of the aquifer recharge from floodplains and surface
water;
- Transfer of software for chemical analyses interpretation
(AQUACHEM) as well as for hydro geological modeling
(MODFLOW) to Maiduguri and Ngaoundere Universities.
There are current negotiations for organizing an interregional
workshop for the dissemination of results in the region at the
Maiduguri University in Nigeria, one location of the UNESCO
Virtual Laboratory on Drying Lakes.
4. Sustainable Water Management Lake Chad - BGR Component
This project is yet to kick start, but is a second phase to the on-going
first phase project being carried out by the German Agency for
Technical Cooperation (GTZ) on Sustainable Water Management
Lake Chad aimed at developing a GIS based knowledge
management system at the LCBC and formalizes data exchange
between member countries and the LCBC.
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The overall goal of the two phases Project ‘’Sustainable Water
Management Lake Chad’’ (GTZ and BGR) with a planned total
implementation period of nine years is that the LCBC manages
transboundary water resources sustainably. The goal of the second
phase project – the BGR component (duration of three years) is:
‘’The LCBC coordinates the exchange of information on groundwater
resources with its member States and integrates this information into
its knowledge management with the aim of developing a sustainable
water resource strategy’’.
The approach will rely to a large extent on capacity building. This will
include training of national water resources experts of the member
countries in collecting, processing and analyzing groundwater data.
Within the LCBC a unit will be established and trained to regionally
assess and analyze the combined national data and to feed
information into the development of an integrated water resources
strategy considering interaction with relevant other sectors.
The implementation period of this project will start from the second
half of 2007 up to mid 2010.
Engr. Muhammad Sani ADAMU
N’Djamena, 1 st July 2007
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