What you need to know:
- Lake Victoria is primarily regulated by precipitation on the surface, catchment input, controlled outflow from a hydroelectric dam on the Nile and evaporation.
- The breakdown of organic materials at the bottom rises to the top, killing fish.
Sensitisation of the public on pollution is taking centre-stage ahead of the World Rivers' day in September and COP 27 in Egypt.
We in the water sector are already feeling the first-hand impacts of climate change and pollution.
We have noticed rising lake levels and a phenomenon that has changed the colour of water and the odour of the lake.
Experts have explained that the lake has a significant impact on regional climate.
Climate variables such as the Intertropical Convergence Zone (ITCZ), El Nino/Southern Oscillation (ENSO), complex orographic forcing and Indian Ocean zonal temperature gradient anomalies impact its thermodynamics and hydrodynamics on diel, seasonal and yearly periods.
The ITCZ, which separates the northeast and southeast monsoons, passes across East Africa twice a year.
First in March-April-May (causing long rains) and again in October-November-December (causing short rains).
The lake is primarily regulated by precipitation on the surface, catchment input, controlled outflow from a hydroelectric dam on the Nile and evaporation.
When the lake becomes isothermal (retains the same temperature), a season of deep vertical mixing depletes oxygen at the bottom.
The breakdown of organic materials at the bottom rises to the top, killing fish.
The decomposing organic waste mixes with water, resulting in a dark colouration and a bad stench.
While the mixing is caused by climatic occurrences, the consequences are becoming more catastrophic.
For example, higher precipitation in the past four years has resulted in a considerable rise in lake levels.
Increased surface runoff carried a large amount of organic material into the lake, which is currently decomposing at the bottom.
This breakdown takes place around June and July due to the seasonal advent of the southeast trade winds, and for a short time towards the end of July, the main body of the lake becomes isothermal in terms of depth.
As a water company operating on the shores of Lake Victoria, we have introduced systems to deal with such risks.
This gives us the confidence to continue drinking water directly from the taps in Kisumu City.
Let’s take care of our rivers and streams for our own welfare.
Mr Thomas Odongo is the Managing Director, Kisumu Water and Sewerage Company Ltd.