The rapid increase in boreholes across Nairobi has raised growing concern among environmental experts, who warn that unregulated groundwater extraction may be contributing to the city’s worsening floods.
Environmental analyst Mohamed Omar says the widespread drilling of boreholes is gradually altering the natural balance between groundwater and surface water systems.
Rising Dependence on Boreholes
Over the past decade, thousands of private boreholes have been drilled in residential estates, commercial buildings, and institutions throughout Nairobi. Many property owners turned to boreholes as an alternative due to unreliable water supply from Nairobi City Water and Sewerage Company.
While boreholes help address water shortages, experts say their uncontrolled expansion is creating new environmental risks.
How Boreholes Can Increase Flooding
According to Omar, groundwater and soil structure are closely connected. When large amounts of underground water are extracted:
Soil layers that normally store water weaken and compact
The ground loses its natural ability to absorb rainfall
More rainwater remains on the surface during storms
In urban areas like Nairobi, the situation becomes worse because rapid construction has increased impermeable surfaces such as roads, pavements, and buildings.
These surfaces already limit water absorption, meaning heavy rains quickly turn into surface runoff and flooding.
Land Subsidence and Drainage Changes
Experts also warn about land subsidence, a process where continuous groundwater pumping causes the ground to slowly sink or compress.
When this occurs:
Natural drainage patterns shift
Low-lying zones become deeper collection points for water
Flooding becomes more severe during heavy rains
Many neighborhoods near rivers and poorly planned settlements are already experiencing frequent flooding during rainy seasons, leading to property damage and major disruptions to transport networks.
Call for Regulation and Better Planning
Omar says stricter regulation of borehole drilling is urgently needed.
Authorities and urban planners should ensure groundwater extraction remains sustainable and properly monitored.
Experts recommend:
Stronger licensing and regulation of boreholes
Monitoring groundwater using GIS and remote sensing technologies
Expanding green spaces and protecting wetlands
Improving stormwater drainage systems
Without better planning and regulation, specialists warn the growing number of boreholes could further disrupt Nairobi’s natural water balance, increasing the city’s vulnerability to extreme rainfall and flash floods in the coming years.
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