An assessment of human-induced impacts on urban wetlands: a case study of the Nairobi dam.
Wetlands are among the most productive ecosystems on earth. They support millions of people and provide environmental goods and services including but not limited to reducing impact of floods, regulating water flow, mitigating impacts of drought, recharging ground and surface water bodies, supply and storing of drinking water among others. This project investigated human-induced impacts on urban wetlands, using a case study of Nairobi Dam, an urban manmade wetland whose history dates back from the year 1953. A UNEP study which was done in 2003 showed that the Nairobi Dam was heavily polluted and the dam’s ecosystem was undergoing serious deterioration due to human activities. The UNEP report proposed measures that were to be put in place to mitigate and avoid pollution of the dam. The specific objectives of this study were to determine the chemical elements which lead to pollution loads in the water entering Nairobi dam. The research also examined the socio-economic benefits of Nairobi dam; the study investigated some of the human activities leading to continuous pollution which may not be soon stopped if long term measures are not taken. The study also assessed the implementation by the relevant government institutions of the environmental policy and laws relating to pollution. The study further discussed the effectiveness of rehabilitation and management measures undertaken to conserve the Nairobi Dam. The samples of water from inlet, outlet and also from within the dam were collected. These water samples were transported to Public Health Engineering Laboratory and preserved in a cold room for a night. Cluster sampling was done based on administrative areas ( 7 locations).The seven locations which were used as cluster areas included; Kibera, Lang’ata, Karen, Mugumoini, Nairobi West, Laini Saba and Sarang’ombe. The clusters were based on the seven locations of the study area. The clusters had demographic and ecological characteristics. The seven clustered points were numbered and by use random sampling, the researcher came up with three locations which were used for this study. The three locations included; Laini Saba, Sarang’ombe and Kibera. Since the population was large, the sample size was determined using a equation developed by Cochran (1963).A list of residents was obtained from area administrative officers, the selection of an element was based on equal intervals, starting with randomly selected element on a population list. A total of 85 questionnaires were administered to the residents for data collection. Primary data was obtained from the field through questionnaires, interview schedules and observation schedules. The questionnaires were administered to the sampled residents of the Nairobi Dam and its surroundings. Quantitative data collected using questionnaires were analyzed using bar graphs and pie charts. With the help of the Statistical Package for Social Sciences software, the quantitative data was analyzed. The UNDP 2007 data base research which was conducted was used to compare with the findings of this research. The results showed that chemical pollution loads in the dam water varied from Lead to Copper for organic and inorganic chemicals respectively. These pollution loads were attributed to human activities around the dam and the use of its water. In particular, interviews, observations and literature linked organics to human activities while inorganic were linked to agricultural sources, especially runoff water from surrounding farmlands where inorganic fertilizers are used. The research found out that the environmental policy dealing with pollution was applied selectively and this was the main reason pollution was a friendly activity to the residents. From the findings the study recommended that the policies need to be harmonised if we are to achieve a socio-economic development and wetlands management required multi-disciplinary or multi-sectoral approach. The last recommendation was that the biggest challenge of socio-economic development was corruption and there was need to be dealt with strongly because this vice overlooks implementation of programs.