NAIROBI, Jan. 16 (Xinhua) -- A hydrologist expert with the United Nations Educational, Scientific and Cultural Organization (UNESCO) on Wednesday urged Africa to pursue rainwater harvesting in order to mitigate climate change.

"One way for Africa to mitigate climate change is through rainwater harvesting which can be used to recharge groundwater which is a reliable source of water," Jayakumar Ramasamy, regional hydrologist at UNESCO's Regional Office for Eastern Africa, told reporters, noting that rainfall patterns in Africa are changing due to climate change.

He said that UNESCO had already conducted a detailed mapping of all groundwater potential in Africa.

He revealed that groundwater will be the ultimate source for water in most parts of Africa and especially in the arid and semi-arid areas as surface water is reducing.

Ramasamy also decried the unsustainable exploitation of groundwater in Africa due to uncontrolled drilling of boreholes.

"As a result, the level of groundwater is reducing and this can lead to serious negative effects," he said.

Simon Chelugui, cabinet secretary of Kenya's Ministry of Water and Sanitation, said that in Africa 75 percent of the population use groundwater as the main source of drinking water, livestock rearing and urban water supply.

"It is a critical source of water supply for rural communities living far from surface water sources, and communities in arid and semi-arid lands," Chelugui said.

He observed that groundwater sustains ecosystems and also the base flow of rivers.

The government official noted that the African continent has a long history of groundwater use and some aquifers have had a transformational effect on the lives of communities. An aquifer is an underground layer of water-bearing rock.

He revealed that groundwater flow is not limited by national boundaries as 72 trans-boundary aquifers have been discovered in Africa.