Impact of rainfall variability on groundwater levels in Ruiru municipality, Kenya

Abstract

Groundwater accounts for the largest fresh water resources in the world. However, there has been limited exploitation of this vital resource in many areas. Where groundwater resources have been utilised, they have been over-exploited, polluted, wasted and mismanaged. In Ruiru municipality, groundwater is a major component of the water supply, contributing about 70% of the water demand. Rising population numbers and industrial development have led to a high water demand, increased water scarcity and more reliance on ground water. Assessing the effect of rainfall variability on groundwater levels of boreholes in Ruiru municipality will help in assessing the sustainability of groundwater resources in the area. Groundwater levels were measured using a dipper and spatial locations of the boreholes were established and mapped using GIS. Rainfall data was collected from the Kenya Meteorological Department and the Water Resources Management Authority. The water table fluctuation method was used to estimate recharge. There was an impact of rainfall variability on groundwater levels. The results showed a decline in groundwater levels during low rainfall periods. The rainfall variability, caused by climate change, brought about prolonged droughts and low recharge in the area. Climate change should be mitigated to cap the decline in groundwater and abstraction controlled to ensure that groundwater resources are managed properly to avoid depletion.