Joburg's water leaks problem

HOW BAD IS IT? NO MONEY IS RECOVERED FOR 46% OF SUPPLY IN THE CITY'S SYSTEM

- Sean Christie

• Lot of flow in rivers is from the city's sanitation system.

In the dry season in Johannesburg, there is more leaked water running in the Jukskei River than naturally occurring river water, a study has found.

This raises troubling questions about the state of Johannesburg's water reticulation.

The river's identity crisis was revealed by hydrologist Simon Lorentz, who started analysing water samples from the Jukskei's daylight point (the point at which the water emerges above ground for the first time) in 2018.

Lorentz subjected the samples to isotope analysis, a process that investigates the ratio of oxygen and hydrogen isotopes in order to determine, among other things, where the water comes from.

Lorenz found that the "isotopic signature" of those water samples was consistent with water from Johannesburg's water pipes.

Here's the technical description in the report:

"The source of water sampled from the Jukskei main channel discharge is either a reticulated water or sewage water leak.

"Characteristic of reticulated water isotope signals, those sampled from the taps in the upper Jukskei catchment reflect an evaporated state, being positioned to the right of the local meteoric water line (LMWL Pretoria).

"This verifies the evaporation process in the supply dams and reservoirs of the reticulated water. The water sampled from the Jukskei main channel has the same evaporated signature."

Another way researchers can tell that a lot of the water flowing in the Jukskei comes from unnatural sources is to look at the amount of water entering Hartbeespoort Dam downstream. Water management specialist Stuart Dunsmore, who has been working on a catchment management plan for the Upper Jukskei, has done just this.

According to Dunsmore, the Jukskei covers 19% of the Hartbeespoort Dam's supply catchment, yet it contributes almost 40% of its annual inflow.