Gestão integrada e concertada dos recursos hídricos dos sistemas aquíferos de Iullemeden, Taoudéni/Tanezrouft e do rio Níger
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GICRESAIT is a replication of the Geo-Aquifer project which focuses on the integrated and concerted management of water resources of the Iullemeden, Taoudéni/Tanezrouft and Niger River aquifer systems. The project, led by the Sahara and Sahel Observatory (OSS) and conducted between 2010 and 2016, focused on the entire basin of the Iullemeden-Taoudéni-Tanezrouft Aquifer System (SAIT) which forms a single transboundary aquifer system. The objective of the project was to significantly improve the concerted and sustainable management of the water resources of the SAIT as well as that of the Niger River in a context of climate change.
The GICRESAIT project was based on a participatory approach with all stakeholders and has three components:
- Improving the knowledge of the SAIT;
- Assessment of the vulnerability of SAIT and the establishment of a consultation framework;
- Capacity building, awareness and communication.
The main steps in this project were:
- The collection of data related to hydrogeology, the water cycle and reservoirs from technical services in charge of water resources management in the seven riparian countries, international and sub-regional research organizations as well as from internationally recognized experts;
- The setting up of a Geographic Information System (GIS) and of a structured and homogeneous database for the whole basin;
- The use of Earth observation data and Digital Terrain Models (DTM) to help model recharge and crop water withdrawals;
- Spatial modeling of the aquifer system.
The Sahara and Sahel Observatory (OSS) is an international organization that operates in the arid, semi-arid, sub-humid and dry areas of the Sahara-Sahel region. Created in 1992, the OSS has been based in Tunis (Tunisia) since 2000. OSS has 26 African countries, 7 non-African countries, and 13 organizations among its members. OSS initiates and facilitates partnerships around common challenges related to shared water resources management, implementation of international agreements on desertification, biodiversity and climate change in the Sahara and Sahel region.
The main actions carried out by the OSS are
- The implementation of multilateral agreements on desertification, biodiversity and climate change;
- The promotion of regional and international initiatives related to environmental challenges in Africa;
- The definition of concepts and harmonization of approaches and methodologies related to sustainable land and water resources management and climate change.
OSS necessarily relies on knowledge transfer, capacity building and awareness raising of all stakeholders.
OSS activities and projects are financed respectively by voluntary contributions from member countries, and by grants and donations from development partners. With effective governance mechanisms and a competent, multicultural and multidisciplinary team, OSS makes a high value-added contribution to the international and African institutional landscape.
The management practice implemented in the GICRESAIT project is based on different steps.
Investigations were used to highlight the presence of areas that appear to have particular potential for groundwater exploitation: (i) either a connection with surface water, which ensures a regular supply that sustains the water resource, even during episodes of rainfall deficit due to climate variations. These are:
- The interior delta of the Niger River in Mali;
- The downstream sector of the Dallols in Niger and Nigeria;
- The Mouhoun basin upstream of the Gondo plain in Burkina Faso;
- The Gao Gap in Mali and Niger.
Either (ii) the high strength of the aquifer formations and their permeability, which lead to the possibility of high unit flows in the catchment works. These are:
- The Tahoua sector in Niger;
- The southern sector of the Dhar de Néma in Mauritania;
- The Nara ditch in Mali.
The objective here was to create a simple and user-friendly tool to allow the database managers (OSS and partner countries) to consult and valorize the data from the water points in a transboundary context. The database has made it possible to integrate information on approximately 123,000 water points (time series of levels for the available piezometers), rainfall data (monthly rainfall levels from 1960 to 2011 for 50 stations), hydrological data (quarterly average ratings and monthly average flows from 1960 to 2012 for 5 stations on the Niger River).
Among the water points integrated in the database, some points have no altitude information, and for others it is uncertain. Thus, a specific tool was developed based on the use of a DTM (Digital Topographic Model) to compensate for this deficiency. The altitudes of the water points allow to have a unique reference and can be used to elaborate geo-referenced piezometric sections and maps.
Use of geo-spatial data
An assessment of the available geo-spatial data for the area was conducted and the data was selected to provide a comprehensive and undisturbed representation of the SAIT area. The geo-spatial data selected were:
- MODIS for land cover mapping at 1:2,000,000 scale;
- GlobCover data (ESA GlobCover project) in support;
- LANDSAT for land cover mapping at a scale of 1:200,000 on a South-North transect as a pilot area;
- SRTM v4.1 data for the DTM in order to have a homogeneous and continuous topography on the intervention area.
Modeling of the SAIT system
The Aquifer Systems of Iullemeden, Taoudéni-Tanezrouft have therefore been modeled according to two distinct mathematical models. However, in order to guarantee geological continuity, the western part of the SAI model has been extended to the eastern part of the SAT, over a 125,000 km2 strip with identical hydrodynamic characteristics (Gao Graben).
The mathematical model was developed to establish the water balance of the entire SAIT: (i) to define the hydraulic relationships between groundwater and the Niger River flows, and (ii) to simulate the behavior of groundwater resources in the face of climatic variations, particularly in the event of a decrease in rainfall.
Two main axes were studied by the managers, namely: (i) the drop in aquifer levels caused by climatic stress and increasing exploitation of the resource, and (ii) chemical and bacteriological pollution of aquifers by human activities.
A risk information system, built from the SIRIS (Scores Interaction Risk Information System) method, integrated both the “physical” constraints of the aquifer systems and their environment (recharge, permeability, water depth, free/captive) as well as the anthropic pressures (populations, water demand, well density). The results of the studies have led to a mapping of vulnerable and at-risk areas, which are therefore priority sectors for management.
Monitoring and evaluation indicators
Monitoring and evaluation indicators have been proposed in order to: (i) better understand the social and development dynamics in the SAIT area, (ii) monitor the effects of these dynamics on the environment and on the aquifer systems, (iii) identify the actions to be taken in terms of development and preservation.
The indicators proposed for monitoring were:
- Driving force indicators: population, agricultural areas, census of wells, boreholes and dams, industrial activities, livestock;
- Pressure indicators: quantity of pesticide, volume of production of factories, etc.
The stakeholders of the GICRESAIT project are:
The OSS as project owner, and the technical services of the seven riparian countries:
- The National Agency for Hydraulic Resources (ANRH, Algeria);
- The General Directorate of Water (Benin);
- The General Directorate of Water Resources (Burkina Faso);
- The National Directorate of Hydraulics (Mali);
- The National Centre for Water Resources (Niger);
- The Nigeria Hydrological Services Agency (Nigeria);
Project partners and financiers:
- The Niger Basin Authority;
- The AGRHYMET Regional Center;
- The African Water Facility;
- The French Global Environment Facility.
The study area of the GICRESAIT project covers an area of 2.6 million km² shared by 7 countries:
- Algeria (450,952 km²; 17%)
- Benin (57,338 km²; 2%)
- Burkina Faso (130,174 km²; 5%)
- Mali (1 089 407 km²; 41%)
- Mauritania (256,374 km²; 10%)
- Niger (524,813 km²; 20%)
- Nigeria (120 272 km²; 5%)
The system studied is the Iullemeden, Taoudéni/Tanezrouft Aquifer System (SAIT) and the Niger River, which is a collection of several groundwater aquifers located in geological formations dating from the Primary to the Quaternary period. The groundwater resources considered are those of the intercalary continental aquifers dated from the Upper Cretaceous and the terminal continental aquifers dated from the Tertiary to the Quaternary. The main course of the Niger River crosses the aquifer system over nearly 2,480 km, 1,700 km of which are in Mali (forming a floodplain called the interior delta), 540 km in Niger, 140 km in Benin in the form of the border with Niger, and nearly 100 km in Nigeria (crossing the Sokoto basin). The SAIT system basin is characterized by several climates, from north to south: arid, semi-arid and dry sub-humid. Annual rainfall fluctuates from over 1,000 mm in the south to less than 100 mm in the north of the basin.
The first studies of the Iullemeden Aquifer System (IAS; 2004-2009) led to the adoption of a memorandum of understanding creating a consultation mechanism for the management of the Iullemeden Aquifer System by the Ministers in charge of water in Mali, Niger, and Nigeria.
In 2013, a diagnostic study on the general, legal, and institutional framework of the countries was conducted during the GICRESAIT project.
Its results were the subject of a meeting of the ministers in charge of water resources of the SAIT, held in Abuja in March 2014, which resulted in an agreement in principle on the protocol for the creation of a consultation mechanism, with a legal personality, for the integrated and concerted management of water resources of the SAIT.
Evidence of benefits from implementation
The project has identified the presence of sectors that have a particular potential for groundwater exploitation due to either:
- A connection with surface water, which ensures a regular supply that supports the water resource, even during episodes of rainfall deficit;
- Important and very permeable aquifer formations.
Figure 2 : Map of areas identified as having high groundwater potential.
Replication potential in SUDOE region
The practice has the potential to be reproduced if that sufficient data (piezometric, rainfall) are available to feed the mathematical model.
It should be noted that this type of project applies preferentially to transboundary aquifers and their governance and resource sharing issues. This type of project presents an interesting potential for replication in the context of a downscaling for transregional management issues.
This type of project also requires significant financial support since the project has received financial support from the African Water Facility (AWF) and the French Global Environment Facility (FFEM) for 1.7 M€.
The work carried out within the framework of the GICRESAIT project is a first step on the scale of the transboundary basin and complementary work is necessary to deepen the knowledge of the sectors with strong potential identified.
The indicators developed within the framework of the project are intended to be expanded as national IWRM progresses in the SAIT areas and integrated into a monitoring framework for this integrated management strategy.
As a result of the project findings, OSS has proposed the development of a regional master plan containing planned actions for the resources of the Niger River, included in the Niger Basin Authority (NBA) Sustainable Development Action Plan (SDAP).
The planned actions are:
- To establish a regional diagnosis on the current and future water needs of the countries by 2030 and 2040 in terms of drinking, agricultural and industrial water supply, in relation to adaptation to climate change;
- Identify the potential for agricultural, mining and industrial development by country;
- Plan water allocation from high potential areas by 2030 and 2040 and related investments;
- Strengthen the role and action of a consultation mechanism.
These actions are aimed at:
- The progressive satisfaction of the water needs of the populations;
- The development of the basin’s arable land, estimated at over 137 million hectares;
- The improvement of the quantitative and qualitative food security of the countries;
- The establishment of a transboundary regional infrastructure promoting economic development;
- The creation of jobs and increased income for farmers.
However, capacity building of staff and technical services is needed to contribute to the development of a regional master plan for the allocation of shared water resources.
Key points of the innovative method
> Integrated management of a transboundary aquifer
> Identification of areas with high groundwater exploitation potential
> Concerted management mechanism
The innovative practice was suggested by Yvan KEDAJ (Aqua-Valley) and Abdel Kader DODO, Lamine BABA SY, and Nabil BEN KHATRA (OSS) participated in the interview.
OSS (2014). Gestion intégrée et concertée des ressources en eau du système aquifère Iullemeden – Taoudéni – Tanezrouft. Plaidoyer GICRESAIT : http://www.oss-online.org/sites/default/files/OSS-GICRESAIT-plaidoyer.pdf – consulté en ligne le 14 janvier 2022.
OSS (2017). Note aux décideurs. La mobilisation des eaux souterraines du Système Aquifère d’Iullemeden-Taoudéni/Tanezrouft, un élément de solution ? : http://www.oss-online.org/sites/default/files/OSS-GICRSAIT-Note-Decideurs_Fr.pdf – consulté en ligne le 14 janvier 2022.
OSS (2017). Gestion Intégrée et Concertée des ressources en eau du système aquifère d’Iullemeden Taoudéni-Tanezrouft et du fleuve Niger. Synthèse finale : http://www.oss-online.org/sites/default/files/OSS-GICRESAIT-SynthFinale_Fr.pdf – consulté en ligne le 14 janvier 2022.
OSS (2017). Atlas des ressources en eau du système Aquifère transfrontalier d’Iullemeden, Taoudéni-Tanezrouft : http://www.oss-online.org/sites/default/files/OSS-GICRESAIT-Atlas.pdf – consulté en ligne le 14 janvier 2022.
Observatoire du Sahara et du Sahel : http://www.oss-online.org/
GICRESAIT-fiche projet : http://www.oss-online.org/gicresait/ – consulté en ligne le 14 janvier 2022.
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