Environment experts have warned that Voi River - the only source of water for Voi town and its environs in Taita Taveta - is flowing towards extinction.
The river has all but disappeared due to massive sand harvesting and brick-making.
Voi River is also the main water source for Aruba Dam in Tsavo East National Park. Its disappearance is expected to deal a big blow to tourism activities in the region.
Senior county and National Environment Management Authority (Nema) officials said the river was shrinking rapidly and that the situation could worsen if urgent intervention measures were not taken to save its ecological status.
Environment and Natural Resources Executive Alexander Mwangeka and Nema County Officer Judith Kalo said ongoing sand harvesting and brick-making activities on the river's banks were illegal.
They said Environmental Impact and Social Assessment (EIA) clearance was needed before such activities could go on. However, this had not been done.
The leaders said the sand harvesting and brick-making had to stop to save this important ecosystem.
Poor farming practices on the river's catchment area had further sealed the river's fate.
The river draws its water from Taita Hills, which, according to the environment officer, were also facing environmental challenges.
"We need to find a lasting solution to the ongoing environmental degradation. There is need to stop human encroachment and poor agricultural practices within its catchment to avert a catastrophe," warned Mr Mwangeka.
He and other environment experts spoke after inspecting the river, which has already disappeared at some points.
According to Ms Kalo, a series of water sources in the area were also on the verge of collapse thanks to increased farming activities as well as uncontrolled sand harvesting and brick-making.