LAKE BARINGO Lake Baringo is a fresh water lake situated some five hours drive to the north of Naivasha. The climate is arid and hot. The area is rather undeveloped with still a relatively low, although rapidly growing, population. The local economy is based on goat herding and small scale agriculture, near streams; there is also some tourism and fishing was an important, albeit small, industry until it collapsed some years ago. Being a freshwater lake, Lake Baringo has populations of hippopotamus and crocodiles as well as an abundant and impressive bird life.

Earthwatch started working on the Lake in 2001, with the objective to further our understanding of the physical and ecological parameters that govern lake variability. This has entailed collecting data on physical, physico-chemical and biological parameters: (i) Monitoring of water quality in the lake and its catchment, (ii) Investigations of macrophytes; species lists and distribution. (iii) Investigations of plankton, species lists and distribution. (iv) Investigations of aquatic macroinvertebrates in the lake and the catchment; species lists and distribution. (v) Investigations of fish; species lists, distribution, and biomass. Water levels and rainfall have varied markedly during the period of investigation.

These variations have, in turn, been associated with variations in the salinity and the concentration of suspended solids in the Lake. Lake conductivity is controlled by the balance of fresh water inflow from rivers in the South and South Easterly parts, and evaporation in the main Lake. Turbidity is caused by the inflow of fine inorganic material via the rivers, and the re-suspension of this material in the extensive shallow areas of the Lake

A number of important findings have emerged showing that:

- Lake Baringo is a highly variable system, governed primarily by changes in lake levels. These changes are well correlated with changes in Water quality, Lake vegetation, and in the composition of plankton community.

- Lake Baringo is very turbid, the turbidity in turn caused to near 100% by inorganic processes (erosion)

- Comparisons with conditions in the main lake, with a smaller and more secluded lake situated to the South (called Lake Kichiritith) suggests that the productivity of the main lake could be higher. The turbid waters are likely the most important factor in constraining biological production.

The findings, in turn, have important implications for management. It is clear that land use changes, mainly over grazing and the clearing of swamp vegetation are threatening the longer term survival of the lake, and are already impacting severely on the lake and its ecosystems. These problems need to be addressed urgently.

Water quality

- The high conductivity and high content of suspended sediment in the lake implies significant constraints for aquatic biota. Areas with better water quality may be found: (i) in the southern part of the Lake, near the two main rivers’ combined outflows; and (ii) in the small lake.
- Physico chemical conditions vary between years. There is also a water quality gradient in the main lake, with fresher water in the south and more alkaline conditions in the north. A plume of fresh water entering the lake can be seen on the Landsat image below.

Sediment Samples of Lake Bottom sediments have been taken, both sediment cores and grab samples. The key findings are: - The sediment is near 100% inorganic in origin, showing that the lakes turbidity is caused by inorganic processes (i.e. erosion of fine volcanic soils in the catchment). - The sediment consists of fine silt and clay, material which settle slowly and which is easily re-suspended by wave action. Plankton - High sediment-driven turbidity is limiting light transparency such that only buoyant Microcystis sp. colonies thrive. Baringo also has very limited zooplankton, probably because of the limited food supply. - The conditions in the small lake are different, with a fairly diverse phyto and zoo plankton, similar to conditions in Lake Naivasha. - Algal chlorophyll a levels are lower in the main lake compared to Kichiritith, whereas nutrient levels are higher. This suggest an under utilized system in the main lake, probably caused by the high turbidity (conductivity may also be important).