Ground Water Assessment

The Geological Survey of Ethiopia has been established in 1968 with the aim of studying earth resources. Since its establishment it has done a lot of studies in several parts of the country and found various valuable earth resources which at places are extracted and contributing a lot to the country’s economy. The Groundwater resource assessment core process is one of the early established as a divisions/ departments of the Geological Survey with a major aim of studying the regional groundwater potential that can be used for various purposes. The process presents its results in the form of hydrogeological and hydrogeochemical maps and accompanying reports. It also contributed to detailed hydrogeological studies mainly for water supply and irrigation purposes for both government and private sectors. 

Hydrogeological survey within the Ministry of Mines has started about 41 years back. This survey had assistance from United Nations Development Program (UNDP) and hydrogeologists from United Nation member countries were assigned as capacity building personnel to help the few numbers of hydrogeologists at the time within the Ministry. The assistance from UNDP was later terminated and since then hydrogeological mapping has been independently carried out by Ethiopian hydrogeologists.Hydrogeology, Engineering Geology and Geothermal Department of the Geological Survey of Ethiopia (GSE) was established in 1982. The department had three divisions, Hydrogeology, Engineering Geology and Geothermal divisions. The overall objective of the department was to assess the groundwater potential of the country, study engineering geological aspects and assess geothermal potential of the country.

 The hydrogeology section was established with in this department as a division in 1982 and was carrying out hydrogeological mapping of the country at a scale of 1:250,000 and detail investigation as per the request. In 2009, the Groundwater Resource Assessment (GWRA) has been re-established at a Core Process level to accelerate the hydrogeological mapping coverage of the country which is supported by hydro-geophysical survey and test well drilling.

The general objective of the GWRA is: To prepare and deliver Hydrogeological maps of the country at progressively higher scale starting from 1:250,000 with accompanying report.Having this broad objective, the following specific objectives are being accomplished:

Evaluate rocks and soils as potential water bearing rocks (aquifer) and non aquifers based on their potential

Determine dependable quantity of groundwater resource, which can be developed

Inventory and definition of spatial and temporal distribution of groundwater resource

Select potential sites for water well drilling and development

Determine vulnerability of aquifers/groundwater to anthropogenic pollution, and identify areas and source of pollution.

Assess water quality for different uses

Identify and do detail study on natural contaminants

Identify occurrence of mineral water

Prepare report and maps based on the above data

 The GWRA pursues its work as capital projects, and consultancy services based on the request from the clients. Detail studies and water well sitting are being carried out, concretely to regional hydrogeological mapping, upon request from regional water Bureaus, NGOS’, investors and Federal Government Offices.

RELEVANCE TO THE COUNTRY ECONOMY

For quiet long time, groundwater has not been given as much attention as surface water as a source of water supply. Recurrent drought and increasing demand around the big cities have diverted the attention of decision makers to use groundwater as an alternative source of water supply, along with surface water.

More than 70% of rural water supply is from groundwater. Furthermore, because surface water is not evenly distributed within the country and it is more dependable than surface water, as well as the low cost of groundwater development and other advantages have diverted the attention to develop the groundwater resource. Groundwater is the sole source of water supply in semi and arid areas.

The output of hydrogeological study by the GWRA gives reliable information to develop the groundwater resource, and whether the quality is fit for the desired schemes. The study will help to identify groundwater development priority areas easily and know the amount of exploitable resource, which will reduce the cost of exploration works by the end users.

As the output is used to develop the groundwater resource for irrigation, water supply, industries, etc, it has great contribution to the government endeavor towards poverty alleviation and MDGS’ goal of water supply.

Beneficiaries of the study include the Federal Government Offices, Regional states NGOs’, research institutes and private investors.

Objective

The main objectives of the hydrogeological assessment work is to identify the groundwater potential areas, quality and sustainable groundwater resource that can be used as a major input for poverty eradication strategy and availing suitable groundwater for individual and community consumption.

Activities

The Groundwater Resource Assessment core process produces hydrogeological maps of several parts of the country at various scales (mostly 1: 250, 000 scale). These maps are produced using fund from government and bilateral projects

Major activities include 

Basic hydrogeological and hydrogeochemical study at 1:250,000 scale. Detail hydrogeological assessment work at various scales. Water quality assessment Services rendered to its external customers. Supervision of water well drilling. Conduct pumping test analysis. Conduct Water quality data analysis and determine its use. Preparation and evaluation of contract document and providing of consultancy services as required by the customers. Customers can provide their request with an official letter mentioning the type and location of the service they are requiring. Attaching terms of reference (TOR) will be appreciated.

Main activities and methods to be followed during Groundwater Resource Assessment:-

Pre-fieldwork activities

Collect and collate all previous data (water points, geological maps, metrological data, land use maps, recent satellite images, soil maps, etc.)Conduct satellite and aerial photo interpretation of the study area.

Prepare a semi-processed hydrogeological map which includes recharge and discharge areas and climatic zone classification of the study area.

Fieldwork activities

  • Re-interpretation of aerial photographs, mosaic maps and satellite imageryon field for reconfirmation of the semi-processed data.
  • Checking & refining the geological and soil maps based on lithologic and permeability variations (Rating permeability variation)
  • Identifying major/minor structural patterns that have effect on the groundwater movement, storage flow, etc., of the groundwater (those which were not visible on images)
  • Additional data collection, checking and further interpretation of data on representative sites, filtering, sorting & plotting of existing hydrogeological data GWL-measure
  • Collection of water samples from springs, boreholes, dug-wells, river, water holes etc, for complete chemical analysis to make water quality assessment. sampling, spring-sampling
  • In-situ testing of water samples for their electrical conductivity and alkalinity using EC-meter and pH-meter respectively. field-equip1, field-equip2,
  • Conduct hydro-geophysical investigations on the selected potential groundwater areas.
  • Supervision of drilling activity which includes lithological logging, well design,  pumping test, etc.

 

Post Fieldwork activities

  • Interpret laboratory results of water and rocks and compile in the report.
  • Conduct data processing, interpretation and map preparation. data processing equipments.
  • Prepare Final and integrated hydrogeological, hydro-geophysical, hydro-chemical and proposed development area maps with accompanying reports. (all three maps in pdf formats)
  • Software to be used includes ArcGIS, Aquachem, Aquifertest, ERDAS, Global mapper, surfer, Modflow, etc. borehole design 

Services rendered to its external customers. 

Supervision of water well drilling. Conduct pumping test analysis. Conduct Water quality data analysis and determine its use.

Preparation and evaluation of contract document and providing of consultancy services as required by the customers. Customers can provide their request with an official letter mentioning the type and location of the service they are requiring. Attaching terms of reference (TOR) will be appreciated.

Future plan

The Groundwater Resource Assessment Core Process is currently started its full implementation of BPR with the aim of satisfying the customers and stakeholders needs and expectations focussed on government developmental strategies. These include: To speed up the coverage of the regional hydrogeological and hydrogeochemical studies by six fold as compared to the previous pace with an accepted quality and standard level. To perform detail hydrogeological and hydrogeochemical assessment work mainly based on customer (stakeholder) request. Groundwater monitoring work focusing mainly on groundwater sustainability, and vulnerability to pollution.

The importance and demand for detailed and speedy hydrogeology mapping especially by Regional Water Bureaus, NGOS’, as well as to meet the MDG goal has become apparent. Such repeated request on one hand and scientific endeavor on the other has brought the thought for the initiation of an accelerated Hydrogeological mapping projects. Hence, a series of project documents has to be formulated with the objective of producing hydrogeological maps of the entire country at 1:250,000 scale.

In light of this, the GWRA has prepared a strategic plan to cover about 32.5 % of the country at a scale of 1:250,000 with in the 5 years (20010/11 – 20014/15), and do detail groundwater resource assessment (covering more than 25,000 km2) on selected area supported with hydro-geophysical study and test well drilling.    

Source of fund

Government and bilateral projects (e.g. Czech Republic). All works are done under the framework of The Ethiopian Groundwater Resources Assessment Program (EGRAP). This program is a collaboration program with the Ministry of Water Resources, and other international projects. 

 HydroGeological Map Coverage of Ethiopia

Scale

Area Covered

1: 2,000,000

100%

 

1: 1,000,000

36.8%

 

1: 500,000

4.8%

 

1:250,000

32.74%

 

1:250,000

9.58% (on-going project)

 

 

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