A GIS Based Water Quality Management - A Case Study Of Water Supply For The City Of Nairobi

Abstract

The ever increasing global population and associated socio-economic development activities have increased the need for abstraction of fresh water and consequently release of wastes to the aquatic environment. Due to lack of controlling mechanisms and treatment facilities, wastes from industries, domestic sewage and agricultural practices find their way into water sources and result in large scale deterioration of the water quality. As a result, it has been recognized that water pollution constitutes a much broader threat than expected and continues to pose serious health risks to the public as well as aquatic life. These anthropogenic impacts make the definition of water quality to more complex, which requires simultaneous consideration of multiple aspects. For possible identification and mitigation of point and non-point contaminant sources that results from these anthropogenic impacts, geographically referencing water quality data and relating these data to other information, such as demography and land use, information is highly important. Water quality assessment with aid of Geographical Information System (GIS) and ultimately its application in the monitoring and analyzing processes is a recent technology driven development. It is a powerful mechanism for establishing relationships between impacts due to natural as well as human activities and its effect on water quality. This thesis has explored a water quality assessment with the aid of Geographical Information System (GIS) and its applications for subsequent manipulations and analyses based on a case study of water supply for the City of Nairobi. The study has focused on exploratory analyses of existing water quality data of Nairobi City Water and Sewerage Company (NCWSC) and relevant field information with application of GIS software. For exploratory analyses of existing water quality data, a GIS software package, the statistical function "Analyzing Patterns and Mapping Clusters" was applied for data manipulations and analyses. The analyses were made based on selected indicator parameters of existing water quality data. The analyses result showed that some of indicator parameters of the water sources and distribution are spatially or regionally variable while others are randomly distributed. Parameters' values were also evaluated in relation to established water quality standards. Based on parameters variability and assessments, it was possible to get information with respect to water quality conditions and status of sources and distributions. The information is useful for implementing control measures and improvements to the water supply system. Furthermore, the study result has revealed some constraints and allowed development of recommendations on the current water quality management system for the City of Nairobi Water Supply. Thus, this case study has proved the validity and applicability of GIS for water quality