Focus on social problems

Abstract

The geological changes, which preceded the formation of the sandbar between Lake Chilwa and Lake Chiuta about 9000 B.P., were responsible for the present form of the Lake Chilwa basin as one of closed drainage. The subsequent climatic pattern of alternating wet and dry periods annually, with heavy seasonal rainfall and high evaporation, has produced the conditions of the highly productive, shallow lake, surrounded by a Typha swamp, which experiences both seasonal changes in lake level and periodic low levels every six years or so. The lake is in a senescent stage, but unless there is a sudden change in the climatic trend, which has not been foreseen, the present form of the ecosystem is likely to continue. It will be subject to periodic extremes of lake level, which may be relatively minor, following only one year of lower than average rainfall, which hampers fishing and farming for one year. A range of increasingly more serious lake recessions following more years of lower than average rainfall have been experienced in the last hundred years, which may interfere with the local staple industries for two to five years. Exceptionally high levels (as in 1978) may also occur either for one year or a number of years to which the people must adapt.