Assessment of pollution and mitigation strategies in Lake Naivasha, Kenya
Lake Naivasha is a shallow freshwater lake situated in the Kenyan Rift Valley approximately 80km north-west of Nairobi. It measures approximately 160km2 and the lake’s basin is bounded by the Mau Escarpment, Olkaria and Longonot volcanic mountains, Kinangop Plateau, Aberdare Mountain Range and Eburu volcanic pile. The basin experiences warm and semi-arid climate and water-level fluctuations between dry and wet seasons. The lake is drained by rivers Malewa and Gilgil, providing approximately 90% of water to the lake, and the seasonal Karati stream.
Lake Naivasha is a Ramsar site and an important bird and biodiversity area (IBA) hence it is a wetland of international importance. The lake supports four dominant introduced fish species: Common carp Cyprinus carpio, two tilapias (Oreochromis leucostictus and Tilapia zillii) and Black bass Micropterus salmoides. The lake’s landscape supports flower farming contributing 70% of Kenyan flower export and geothermal power generation contributing 15% of Kenya’s electric power. The basin is a home to Hells Gate and Aberdares National Parks, and private wildlife sanctuaries such as Oserian, Crescent Island and Kongoni promoting Kenya’s tourism development. The region experiences rapid population growth as a result of the rapid growth of flower farms, and the development of fishing and tourism industries.
The lake faces a number of challenges including excessive enrichment of nutrients from various sources, fishing pressure, introduction of alien species (such as exotic crayfish Proambarus clarkia, water hyacinth Eichornia cressipes, and all the fish species ), excessive water abstraction from the lake and underground sources. The lake’s basin has experienced an increasing area of land cultivated since the first flower farms of the 1980s indicating potential for pollution discharge from the horticulture industry. Several settlements have come up around the lake to provide housing for people who come to work in the flower farms. This poses further threats to the lake with the lack of waste treatment facilities or piped water supply in majority of the areas. Near these settlements, the lakeshore is also degraded by human use for domestic livestock watering, laundry and washing. The sewerage collection of the adjacent Naivasha town only covers part of the town while the open drains in the town carry wastes dumped into the lake during heavy rains. Besides, deforestation in the catchments, sediments from cultivated farmland, untreated domestic and industrial effluent from Naivasha town and agricultural fertilizers are potential sources of polluted runoff to the lake.
The health of aquatic systems according to Bartram and Balance (1996) require an investigation and evaluation of the aquatic environment including the assessment of water quality parameters, biological life, particulate matter and the physical characteristics of the water body. Given the above potential sources of pollution in Lake Naivasha, the overall aim of this study is to investigate the quality of the aquatic environment and develop mitigation strategies for the Lake.
1. To identify the types and sources of pollutants in Lake Naivasha
2. To measure the levels of pollution in Lake Naivasha
3. To document the existing and potential pollution control and mitigation strategy for Lake Naivasha
Material and Methods
a) Sampling of water quality parameters
Five sampling sites (Fig. 1) will be selected based on their nearness to settlement area at the Southern shore near Elshamere Conservation CentreI, inlet rivers feeding into the lake at the Northern shore where Rivers Malewa and Gilgil enter the lake I, Naivasha town sewerage outlet into the lake at Kihoto shoreline in the north-west (S), flower farms at South-west shoreline (F) and the Crescent Island lagoon (L). Sampling will be done monthly for at least six months in order to monitor pollution with regard to seasonality.
Figure 1: Map of Lake Naivasha showing the location of sampling sites (modified from Anonymous)
Primary data will be collected by measuring the physico-chemical parameters of water using the Aqua meter water quality device (Rostom et al., 2017). This device measures many parameters including water pH, temperature, turbidity, oxidation-reduction materials, dissolved oxygen, specific conductivity, crude oil contamination. This devise is chosen as opposed to the traditional analytical methods for determining water quality in the laboratory that are time consuming and use very high cost apparatus or reagents. Besides, the accuracy of Aqua meter devise measurements according to Rostom (2017) is very high; temperature ±0.1, pH ±0.01, turbidity ±3, conductivity 0.2% of selected range, oxidation-reduction potential (ORP) ±1mV and high dissolved oxygen (HDO) ±0.2%.
b) Sampling and laboratory analysis of heavy metals
Water samples will be taken at different places at each sampling station every month. A PVC tube column sampler will be used for taking samples at 0.5m depth from the surface of water. The collected samples in each station will be mixed in a plastic bucket. A sample of 1 litre will be taken from the mixture and placed in a polyethylene bottle that will be kept refrigerated and transported to the laboratory for analysis of the samples. Whatman membrane filter paper will be used to filter the water samples. The samples will be acidified with 3ml HNO3 per litre and refrigerated in clean, sterile and labeled plastic containers (Ramos et al., 1999). Atomic absorption spectroscopy will be used to determine the presence of heavy metals. Concentrated HCl will be used to extract water samples and preserved in a refrigerator till analysis of Fe, Zn,Cu, Pb,Sb, Ti, Cr, Co, Ni, Cd and Mn.
Sediment samples will be collected using core sediment grab sampler. Several cores of sediments will be collected at different locations per sampling site every month to make a composite bulk sample (Mudrock and Macknight, 1994). The samples will be kept in clean plastic bags and chilled on ice box for transport to the laboratory for determination of heavy metals. The sediment samples will be dried in the laboratory at 1050C, ground and sieved. About 1.0g of the fine dried grains will be digested with a mixture of concentrated H2O2, HCl and HNO3 and preserved in a refrigerator till analysis (Saeed and Shaker, 2008).
Samples of four dominant fish species of Lake Naivasha; common carp Cyprinus carpio, tilapias (Oreochromis leucostictus and Tilapia zillii) and black bass Micropterus salmoides will be collected from commercial fish catch of the lake. The four species will be studied to indicate their levels of bioaccumulation of heavy metals since they have different niches within the lake’s aquatic system. The total lengths and total weight of each specimen will be taken. Fish samples will be transported in ice box to the laboratory. Samples of different fish organs/tissues taken will be sorted in the lab. Heavy metals will be extracted by Atomic Absorption Spectrophotometer instrument using the atomic absorption method for fish as described by AOAC (1990). Historical data on the above parameters shall be obtained from the Kenya Marine and Fisheries Research Institute (KMFRI) upon which changes in water quality parameters shall be evaluated. The values obtained for each of the water quality parameters shall be compared with the WHO recommended standards to evaluate variations with the actual values.
c) Measuring organic pollution level
Phytoplanktons are primary producers in aquatic ecosystems including lakes. Their presence can be used as an indicator to determine the nutrient level which is the basis for preparing and monitoring the strategies for lake management. Members of the cyanobacteria group, for example, are particularly important since they often form nuisance blooms. Their dominance is an indication of poor water conditions in lakes (Bhateria and Jain, 2016) while some of the species produce harmful toxins (Fakioglu, 2013).
Chlorophyll-a concentration is expected to give the strongest indication of organic pollution in the sampling locations. Chlorophyll-a measurement involves the measure of phytoplankton standing crop biomass, which increases with increasing loading rates of nutrients, mainly phosphates and nitrates. The water samples will be tested for water quality parameters and analyzed in a spectrophotometer for chlorophyll-a levels. Chlorophyll-a extraction will be done using ethanol as recommended by Porra et al. (1989) and Seely and Jensen (1965). Water samples will be forced through a 2cm diameter filter paper which will be transferred to a dark vessel (in order to prevent chl-a degradation by light) and 30ml of boiling ethernal poured into the vessel. The vessel content will be put in a spectrophotometer cuvette and analysed for absorbance, both before and after treatment by acidification.
d) Documenting existing and potential pollution control strategies
This study will also focus on stakeholder involvement and empowerment of local people and institutions. The study will first document the existing pollution control strategies. Secondly, a participatory stakeholder-based pollution control and mitigation protocol will be developed as a product of this research using the baseline data obtained and analyzed in the study. The strategy will involve establishment of formal and informal structures or groupings of stakeholders through stakeholder analysis. The stakeholders will include local communities, flower farms, county governments in the Lake’s basin, relevant government departments and parastatals, and non-governmental organizations. Two seminars will be presented to stakeholders to share research results. This will be followed by a workshop through which existing pollution control and mitigation measures will be shared and new ones identified and recommended for Lake Naivasha.
Through advocacy visits to relevant institutions, the stakeholders will be engaged to develop and implement measures that address the identified pollution problems in Lake Naivasha. This will include stricter adherence to discharge standards from flower farms and urban discharges, and rehabilitation of degraded riparian areas along rivers and the Lake. Examples of potential pollution mitigation strategies that shall be likely recommended include development and installation of a central urban waste water treatment plant and chemical treatment of water to reduce phosphates; community involvement in monitoring and data collection and awareness raising on risks associated with poor land management practices in the lake basin; and design of a sewer system to cover settlement areas outside sewerage coverage around the lake to reduce potential faecal contamination.
Analysis of variance (ANOVA) will be used to analyze water parameters and to evaluate the significant difference in the concentration of heavy metals in the water, sediments and fish species. Data that are not normally distributed across all the sampling locations shall be analyzed using Kruskal Wallis test. Principal Component Analysis (PCA) shall be used to determine whether each sampling location has a distinct set of characteristics.
A. O. A. C. (1990). The Association of Official Analytical Chemists. Official Methods of
Analysis. 15th ed. “Atomic Absorption Method for Fish”. Washington, D.C.
Bartram, J. and Balance, R. (Eds). (1996). Water Quality Monitoring. A practical guide to the design and implementation of freshwater quality studies and monitoring programmes. UNEP/WHO. TJ Press (Padstow) Ltd, Padstow, Cornwall
Bhateria, R. and Jain, D. (2016). Water quality assessment of lake water: a review. Sustain. Water Resour. Manag. 2:161-173.
Mudrock, A. and Macknight, S. D. (1994). Techniques for aquatic sediments sampling. Lewis Publ. Boca Raton.
Parker, R. C. (1972). Water analysis by atomic absorption spectroscopy. Varian techtron, Switzerland. In: E. I. Adeyeye (Editor), Determination of trace heavy metals in fish and in associated water and sediment from some fish ponds. Int. J. Environ. Stud. 45: 231-238.
Rostom, N. G., Shalaby, A. A., Issa, Y. M. and Afifi, A. A. (2017). Evaluation of Mariut Lake water quality using hyperspectoral remote sensing and laboratory works. The Egyptian Journal of Remote Sensing and Space Sciences 20:S39-S48
Saeed, S. M. and Shaker, R. M. (2008). Assessment of heavy metals pollution in water and sediments and their effect on Oreochromis niloticus in the northern delta lakes. Egypt.8th Interl. Symposium on Tilapia in Aquacult.
Required Items Item Description Units Rate/ Unit Amount (KSh.)
Stationeries Project Laptop 1 50000 50000
Writing pads 16 145 2320
Pens/pencils 18 80 1440
Lab & field data collection 200000
Lab costs equipment (see list in Appendix 1)
Monthly Lab charges 6 20000 120000
Consumables Boat hire/fuel 30 5000 150000
Local transport/fuel 60 800 48000
Airtime/Internet 60 500 30000
Research permits 1 3000 3000
Personal allowances \
Principal Investigator (PI) 60 8000 480000
Co-PI 60 6000 360000
Field Assistants (2) 40 4000 160000
Results Seminars 2 30000 60000
dissemination Workshop 1 80000 80000
Publications 3 20000 60000
Advocacy 5 20000 100000
Unforeseen costs Contingency (5%) 95238
Grand total in kesh 1,999,998
Grand total in US Dollars 19,999.98 $
• Project laptop – For data storage and analysis
• Lab equipment – Lump-sum amount (approx. @200,000) for equipment and reagent costs. This could vary depending on either availability for purchase or hire
• Monthly lab charges – 6 months lab charges at KMFRI labs or University of Nairobi labs for analysis of data approx. @ 20,000 per month
• Boat hire/fuel – 30 days boat hire and fuel approx. @ 5000 per day for water, sediments and fish samples collection
• Research permit – Research permit obtained from NACOSTI @ 3,000
• Principal investigator (PI) & Co-PI – Working for 60 days @ 8000 and 6,000 respectively (30 days field data collection, 3 days reconnaissance, 15 days data analysis, 4 days for organization and implementation of training workshops, 8 days advocacy)
• Field assistants – Two data collection field assistants paid @2000 for 30 days, 10 days paid for assistance/support during reconnaissance visit, capacity building/training workshops and advocacy
• Seminars – Two seminars @30000 each to share research results with relevant stakeholders at local and national levels
• Workshop costs – stakeholder analysis, stakeholder workshop on potential pollution control and mitigation measures
• Publications – Three publications in international peer reviewed journals @20000 per publication
• Advocacy costs – five visits to relevant institutions for advocacy, production of publicity materials, transport, personnel costs
Appendix 1: List of potential lab/field equipment and reagents
• Aqua meter
• PVC tube column sampler
• Plastic basket
• Polyethylene bottle
• Cooler box
• Filter paper
• HNO3 acid
• Plastic containers (lab use e.g. refrigeration)
• Atomic absorption Spectrophotometer
• Conc. HCl
• Core sediment grab sampler
• Weighing scale
• Measuring ruler
• Fish sampling/dissecting kit