Status and Causes of Deterioration of Wetlands in the Eastern Riftvalley, Case Study of Lake Nakuru - Kenya

Abstract

Lake Nakuru is a shallow hyper-eutrophic, alkaline and saline endorheic lake located in Rift Valley’s eastern arm. Despite its great importance, Lake Nakuru has undergone profound changes due to anthropogenic activities, mostly due to the amplification of industrial and agriculture activities, urban sprawl and rapid population growth in the last few decades. The study aimed to determine the threats facing the lake, to identify the factors leading to water pollution, to evaluate the status of the surface water quality, investigate the seasonal variations in the physio-chemical parameters of the surface water and to assess levels of toxic heavy metals in the surface water and sediments in the lake. Quantitative and qualitative methods of data collections were used. These included questionnaires, insitu measurements, and laboratory analysis as well as field observations. The respondents comprised of 11 KWS staff members and 196 households from 3 sub-locations; Mwariki A, Mwariki B and Pwani. A total of 20 samples were collected in the wet and dry season to measure temperature, pH, DO, alkalinity, TDS, TSS, nutrients (Nitrate, Phosphate, Ammonia) and heavy metals (Cu, Zn, Pb, and Cr) of the surface water and 4 sediment samples were collected to assess heavy metal concentration. The data were processed to descriptive statistics using SPSS and Excel in order to measure distribution trends, dispersions, disparities and associations and inferential statistics, specifically a two tailed t-test was used to assess the significant difference in the lake water parameters in the dry and wet season. Sewage and industrial pollution were amongst the top contributors of water pollution. Physio-chemical properties of the surface water varied in the dry and wet season. Temperature, pH, TDS, TSS and nutrient values were above the permissible limits for aquatic ecosystems. Temperature, TDS, Phosphate, Nitrate and Ammonia concentration were higher in the dry season where as alkalinity, DO and TSS concentrations were greater in the wet season. Concentration of Pb and Cr were higher in the surface water than the recommended limit. From the findings, the highest level of pollution was in the storm drain, lake center, mouth of River Nderit and Lamdiac. Presence of all four metals were detected in the sediments, with the highest concentration at the storm drain. Seasonal variations showed there was a significant difference (p < 0.05) in temperature, DO, TSS, Phosphate and Ammonia levels between both the seasons. The study concludes that the main issues threatening Lake Nakuru are the disruptions to its water quality arising from human activities in the catchment area. Strict implementation of policies related to the protection of Lake Nakuru is required. Legal action should therefore be taken in respect of all of those sectors that discharge toxic chemicals into the feeding rivers and the lake. Public awareness of pollution issues and their implications in the lake is necessary. This can be done through environmental education, as it is critical to enhance, spread knowledge and enable communities to protect the integrity and complexity of nature and ensure that the use of valuable resources is fair and environmentally sustainable.