 The Sasumua Dam, the Ndakaini-Thika Dam (since 1996) and Chania-B Dam supply Nairobi through interbasin transfer from the Tana River drainage area.About 20% of the supply is from ground water resources which corresponds to around 60,000 to 70,000 m3 per day.Mombasa, Kenya's second largest city, serves its water demand through the Marere Water Works in the south-west, the Baricho Intake at the lower Athi River and from Mzima Springs, upper Athi River, through a 220 km pipeline to the city.