GICRESAIT

The GICRESAIT project was based on a participatory approach with all stakeholders and has three components:

1. Improving the knowledge of the SAIT;
2. Assessment of the vulnerability of SAIT and the establishment of a consultation framework;
3. 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.

Responsible entity

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.

Detailed explanation

The management practice implemented in the GICRESAIT project is based on different steps.

Hydrogeological investigations
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.

Data base
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.

Vulnerability assessment
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.