Victoria Falls is a well-known and popular Tourist spot on the Zimbabwe/Zambia border in South Central Africa.. It used to be known as 'the smoke that thunders' and is found on the River Zambezi. Less well known though are Kariba Lake and Cabora Bassa, both built on the Zambezi River which itself is on the Rift Valley Fault line that runs North and South from Ethopia on the Red Sea. (Actually it starts in the Jordan Valley in Israel.)

Just to speculate, wouldn't it be odd and cataclysmic if that chunk of Africa through which the Rift Valley runs, broke off, and became a large, elongated island? The weight of the water now bearing down on the southernmost end of the Rift which is the Zambezi may just be a contributing factor.

Salvinia Molesta unveiled the ugly side of its face on Lake Kariba around 1960. It dramatically covered huge areas of the water body, significantly putting an end to the hope of developing a large and sustainable fishing industry on the Lake.

It is now posing a threat to Lakes in the USA. To stop salvinia molesta spreading, boaters can ensure that no part of the plant is caught up in any part of the boat's underwater mechanism, or indeed anywhere on the boat. Jet washing both large and small boats assists greatly with this, as does a visual inspection to detect any part of the weed on the boat.

Salvinia Molesta (molesta from the verb 'to molest' - to damage innocence) is an aquatic Brazilian fern. It floats on the water and has leaf-like fronds up to 4 cm in length which have a thick hairy surface. Below the water, long hair-like strands join at the end to form a billowing swirl.

It does best in slow-moving water e.g. lakes, ponds, ditches, marshes and rivers, avoiding brackish or salty waters, but is able to tolerate polluted water. Similarly, it is not affected by wide-ranging temperature variations, though it does best in moderate temperatures.

Sadly, its existence in the US is most probably as a result of being imported for aquarium or garden ponds. Alternatively, importing fresh iced fish may have been the source of contamination.. Silvania Molesta is prohibited in many of the US states, but actually getting rid of it is not simple.

Firstly it has a horrendously rapid growth ability, doubling in surface area almost every 4 days. Secondly growth also occurs downwards which means that it can form an island up to 60 cm thick. As it dies and decomposes, the oxygen in the water is used up, leading to stagnation which in turn kills off plants, insects and fish.

A weevil has been used successfully in trials to control it as have some chemicals. Mechanical means have been employed in getting rid of it, but serious problems are encountered in this method of elimination. How to successfully destroy the huge piles of harvested plants and coping with machinery in shallow water being just two of these problems.

All boating activity, small boats or large boats, is to be enjoyed in the outdoors. Let it remain so for a long time to come as every endeavor is made to keep our lakes clear of avoidable contamination from plants like salvinia molesta.