Ethiopia UNCOTROLLED GROUNDWATER EXPLOITATION
FROM THE VULNERABLE
AQUIFERS OF ADDIS ABABA, ETHIOPIA
Tamiru Alemayehu
1Statement
Key Conclusions & Recommendations
• Between 1886-1944, the water supply for Addis Ababa was derived from groundwater in the form of springs and dug wells. Additional demand necessitated treatment of surface water derived from three surface reservoirs (Gefersa, Legedadi and Dire). However, the exponential population growth in the city necessitated the extraction of groundwater in different localities
which requires a delicate aquifer management strategy to avoid over-abstraction.
• Water pollution tends to rise with increasing human population which has relatively low level of economic development in the city. Consequently, pollution of surface and groundwater is one of the most serious problems affecting the health of the population, directly as a consequence of drinking and other uses of contaminated water.
General
• Addis Ababa was established as the capital city of Ethiopia in 1886 (119 years old)
• Currently hosts around 4 million residents.
• First water supply: Springs & Dug wells
• Second supply: Surface water
• Third supply: Surface + Groundwater
• Current supply shortfall: 25% of the population
Aquifer / Country Setting & Characteristics
Location of Ethiopia
Groundwater flow and abstraction
Aquifer vulnerability
Municipal water resource
• Water demand continuously increase.
• Effective recharge is 200mm (Eastern), 150mm
• (Western) and 64mm (central & Southern) part of the city
• Gefersa 30,000 m3 per day
• Legedadi 150,000 m3 per day.
• Dire dam supply 42,000 m3/d for Legedadi center
Tot: 222,000 m3 per day
Map shows more than 600 operational boreholes in the city
Groundwater pollution
Vulnerability class figure
Figure opposite represents risks of groundwater that are potentially sensitive to pollution.
Vulnerability classes ranging from low to high.
Fig/Tbl Key2
Gaps & Innovations Lessons Learned Planned Implementing Actions
Fig/Tbl Key2
E. Coli ranges from 3 to 89 bacteria/100ml derived from domestic sewage both in springs, dug wells and boreholes Bacteria travel time
To depth of 50 m below surface with hydraulic conductivity of 340m/day
2.5 – 4.0 hr.
Primary protection zone: 2000m
Fig/Tbl Key3
Bacteria in groundwater
Abstraction of groundwater characterized by:
• Well spacing: Average distance 50m
• Abstraction from main municipal wells (Akaki well field) 30,000 m3/day and from other municipal well is 10,221 m3/day (sub total~
40,000 m3/d).
• Other private wells tap as much as 50,000m3/d
• Total abstraction is 90,000m3/d :: Again this is not yet sufficient
Abstraction has led to a decrease in the water level through time during extensive pumping.
Groundwater circulation ( map opposite) occurs in 3 major aquifers:
1. Shallow aquifers: made of weathered volcanic rocks and alluvial sediments along the river valleys.
2. Deep aquifers: made of fractured volcanic rocks that tap fresh ground water derived from regional recharge and circulation.
3. Thermal aquifer: that is located at depth greater than 300m in the central part of the city (Filwoha aquifer).
1
Department of Earth Sciences Addis Ababa University, Ethiopia.
• The main water supply aquifer of the city needs further attention to protect the volcanic aquifer from pollution.
• It is observed that no aquifer management regulations are set and the aquifer has no owner, so there is no consideration of the pumping interference and aquifer depletion.
• Due to domestic waste contamination, most of the wells, which are located in the city center are tapping contaminated water.
Therefore, priority should be given to the municipal authority to fulfill the public demand.
The Municipal authority should be implementing the following actions:
• Fix minimum well spacing based on the cone of interference ,
• Control the usage: for example industry, agriculture, business.
• Control the quality as the users confuse the sources of the waterborne disease (Municipal supplies are treated and disinfected)
Aquifer vulnerability Groundwater pollution Bacteria in groundwater
• Main water supply aquifer of the city lies on medium to highly vulnerable zone
• No aquifer management regulations are set
• Due to domestic and industrial waste contamination, most of the wells are tapping contaminated water.
• Due to recent climate changes (excessive heat and low rainfall in the Horn of Africa) Effective recharge to water supply aquifers is progressively decreasing.
• Private owners are not treating the groundwater, and are in risk zones.
Filwoha fault
Fanta Fault
2018.50 2018.60 2018.70 2018.80 2018.90 2019.00 2019.10 2019.20 2019.30 2019.40 2019.50 2019.60 2019.70
Nov- 2001 Nov-
2001 Dec- 2001 Dec-
2001Jan-2002Feb- 2002 Mar-
2002 Mar- 2002Apr-2002 Apr-2002
However, recent international interest, governments and NGOs, engaged in environmental protection have given emphasis to groundwater protection from pollution.
In the current situation well sitting is not following the degree of vulnerability of the aquifers to pollution in the city.
Consequently, many wells are tapping polluted water with E.
Coli that ranges from 3 to 89 bacteria/100ml derived from domestic sewage, both in springs, dug wells and boreholes where vulnerability class falls medium to high.
Innovations Gaps
DISCLAIMER: Poster draft prepared by IWRM.org on behalf of the author. Any inconsistencies between author input materials and the poster is unintentional.
