Spatio-temporal variations in selected water quality parameters and trophic status of Lake Baringo, Kenya

Abstract

Lacustrine and riverine ecosystems provide important goods and services, including being habitats for aquatic biodiversity, local micro-climate moderation and a source of economic livelihoods for riparian communities. At the same time, however, they fact continuing anthropogenic and natural threats that can affect their water quality, ecological integrity and biodiversity. The present study focused on assessing spatio-temporal variations in water quality and trophic status of Lake Baringo, a Ramsar site in Kenya. A number of physicochemical parameters, including nutrient loads, trophic status and organic pollution indices, were evaluated for the lake from water samples collected from March 2008 to December 2020. The results of the present study indicated five parameters (turbidity, fluoride, urn:x-wiley:13205331:media:lre12367:lre12367-math-0001, total phosphorus and DO) exceeded the permissible limits for drinking water based on WHO standards. The water quality index (WQI) values ranged between 556.04 and 693.54, being well above the WHO recommended limit (WQI = 100), indicating Lake Baringo water to be unsuitable for human consumption. The fluoride (F−) ions and water turbidity contributed the most relative weights to the lake's WQI. The organic pollution index (OPI) for the lake varied from 4.33 to 4.67, significantly above the organic pollution scale of 1.0–3.9 and indicating the lake is not organically polluted. A positive relationship was found between turbidity and rainfall, suggesting the influence of catchment activities on the lake. The nutrient load had less effect on both the WQI and OPI of the lake, indicating low inputs from the catchment. The lake's trophic status shifted between eutrophic and mesotrophic conditions from 2008 to 2020, based on the Carlson's trophic status index (CTSI) values. Application of a holistic and integrated lake basin management (ILBM) approach is recommended for the management of Lake Baringo and its watershed in order to sustain its ecological processes and the associated riparian community economic livelihood support from the lake.