Geospatial techniques to predict the spatial distribution of water quality in Nyandungu wetland

Abstract

The Nyandungu wetland, located in a rapidly urbanising region, is facing significant water quality challenges due to increasing human activities. This study aims to provide a comprehensive spatial analysis of E. coli contamination in the wetland, using kriging interpolation methods to map the distribution of this pollutant. E. coli was chosen as the main indicator of pollution because of its prevalence and implications for public health, serving as a critical marker for faecal contamination in water bodies. To achieve the objectives of this research, water samples were taken from various points in the Nyandungu wetland. These samples were analyzed for E. coli concentrations and their geographical coordinates were recorded to facilitate spatial analysis. The study used variogram analysis to understand the spatial structure of the data, followed by kriging interpolation to estimate E. coli concentrations at unsampled locations. The results were visualized using ArcGIS 10.8, creating thematic maps and interpolated surfaces illustrating the spatial distribution of E. coli contamination. These visualizations were enhanced by overlaying other geographical layers, providing a complete context for the analysis. The results revealed significant spatial variability in E. coli concentrations in the wetland, with some areas showing higher levels of contamination. For instance, observed concentrations ranged from as low as 10 CFU/100ml at some sampling points to as high as 94,300,000 CFU/100ml at others. Kriging interpolation predicted E. coli concentrations at unsampled locations, with values ranging from -5,065,838 CFU/100ml to 23,817,700 CFU/100ml, indicating areas of both potential underestimation and overestimation of contamination. These results highlight the need for targeted interventions to mitigate sources of pollution and protect the wetland ecosystem. In addition to E. coli, other water quality parameters such as pH, temperature, biochemical oxygen demand (BOD), dissolved oxygen (DO) and heavy metals were analyzed to provide an overall understanding of the state of the wetland. These parameters were also spatially analyzed to identify areas of concern and their potential impact on the ecological health of the wetland. In conclusion, this research provides a detailed methodological framework for the spatial analysis of water quality using kriging interpolation. The knowledge gained from this study is crucial for the sustainable management of the Nyandungu wetland and can inform future efforts to monitor and improve water quality in similar ecosystems