Initial Discovery: According to my grandparents, the Typha domingensis weed (Makuruvia as we call it locally) was not in the lake before; it started to appear around late 1950s as small floating patches. During this period, the lake had higher water levels, which prevented the weeds from anchoring permanently due to fluctuating winds.
Permanent Establishment: Over the following decades, as the lake’s water levels fluctuated and periods of drought occurred, these floating “weed islands” began to anchor to the lake bed and became permanent fixtures.
Current Status: Today, the infestation has expanded significantly, with Typha now estimated to cover up to 75% of the lake’s water surface. It forms a dense barrier up to 2 km wide along the southern, western, and eastern shores. This threatens the existence of the lake and well-being of the surrounding communities.
Direct challenge to fisheries; these Typha islands (Matinga as we locally call them) make it difficult for fishermen to get out into the open water to cast their nets, and even foul the fish nests. They increase the spread of typha these reduces oxygen circulation in water, which negatively affects the fish.
Factors Driving the Spread
The rapid expansion of Typha in Lake Jipe is attributed to several environmental changes:
- Siltation: Increased soil erosion from surrounding agricultural land has led to heavy siltation, making the lake shallower and providing an ideal environment for Typha to flourish.
- Nutrient Enrichment: High levels of nutrients in the water, often from agricultural runoff, act as fertilizer for the weeds.
- Reduced Inflow: Diversion of feeder rivers (like the Lumi River) and deforestation have reduced water inflow, contributing to the shallow, stagnant conditions Typha prefers