CHAD: X-raying the desert for water
Hunting for water
GOZ BEIDA, 3 June 2010 (IRIN) - Geologists are using technology known as magnetic resonance sounding (MRS) to take "x-rays" of the ground to find new water sources in eastern Chad, where more than 300,000 refugees from neighbouring countries have arrived in recent years.
"Given water shortages, we do not have time to search for water with only classical methods," said Jean Bertrand, president of France-based IRIS Instruments, which manufactures the equipment and has trained experts working in Chad to use this technology to find water.
Methods used to search for groundwater typically look at how rocks react to radar and electrical currents, which could lead to false readings of the presence of water, said Bertrand.
"This [magnetic resonance sounding] is direct prospecting, whereas with other geophysical studies we get indirect signs on whether or not there is water. Here, a sign of water means there is water, which means less unnecessary drilling," said Pierre Michel Vincent, a hydrologist who recently worked with the Ministry of Water and the UN Refugee Agency (UNHCR) in Chad.
"Only one out of three boreholes drilled in Chad produces water," he told IRIN. Magnetic resonance sounding sends electrical currents through the earth in search of hydrogen atoms, which gives a reading of how much water rocks hold. "This technique identifies where water is more quickly than traditional geophysical studies."
Refugees who have fled Sudan and Central African Republic constitute 35 percent of eastern Chad's estimated 700,000 population, according to the most recent census. Hydrologist Vincent said there was not enough information on half of the 4,000 recorded water points in the area to know if they still produced water.
|We could drill 500 more wells now and still not have enough water
People from local communities as well as refugees struggle to find half the recommended 15 to 20 litres of water per day for drinking, cooking and bathing, and many were only able to secure six litres a day on average, said UNHCR.
"There is not enough water to provide for the expanded population - we could drill 500 more wells now and still not have enough water," Vincent told IRIN in October 2009.
Erratic and insufficient rainfall in 2009 meant Chad produced 34 percent less food than in 2008, which has wiped out livestock and placed two million at risk of hunger in the country, the government noted.
The eastern town of Iriba, which hosts 55,000 refugees, received 135mm of rainfall in 2009 compared to 1950, when it received three times as much, according to state records.
Photo: IRIS Instruments
|Searching for water through sounding in Goz Beida, October 2009
Equipment manufacturer Bertrand told IRIN the entire sounding kit weighed around 350kg, required training, and cost US$180,000. In the past five years, groups in Mauritania, Algeria, Morocco, Rwanda, Niger, Burkina Faso, South Africa, Mozambique and Namibia have purchased magnetic resonance sounding equipment.
Its drawbacks are that it can only read 150 metres into the ground, and readings are sensitive to electromagnetic signals and power lines, which made readings in cities difficult, Bertrand said.
After training in Goz Beida last October, IRIS Instrument and aid workers identified a promising location for water right outside the city, located 200km south of the eastern town Abéché. Oxfam Intermonde, a global relief NGO, is studying drilling prospects.
Bertrand said sounding complemented current groundwater search techniques, and might not be right for all situations. "If you can cure an illness with an aspirin, then there is no need to order the x-ray. But with worsening water shortages, different techniques need to be considered. The challenge and goal of groundwater exploration is to use the least amount of money to find as much water as possible."