Measuring Spatial Accessibility of Water Points in Dodoma City Council Adaptation of the Two-step Floating Catchment Area Method

Context and background Conventional methods for measuring water point accessibility based on threshold demand or distance, result in uniform indices that may be inflated/deflated at different dwelling places within administrative units. Goal and Objectives: This study aims to increase the accuracy of estimated spatial accessibility of water points by adapting the Two-step Floating Catchment Area method which is based on both threshold demand and distance. Methodology: The two-step floating catchment area method was examined and its limitations were illustrated using the hypothetical scenario. Then, the two-step floating catchment area method was refined by introducing a demand-balancing factor in its first step and proposing weighted averaging instead of unweighted summing of supply-to-demand ratios in its second step. The conventional and refined two-step floating catchment area methods were implemented using QGIS 3.28 to quantify the spatial accessibility of water points in Dodoma City Council. The latter method was based on the disaggregated population at grids of 200 m by 200 m. Results: Regardless of threshold distance, the conventional method generated a uniform accessibility index for each Ward. Meanwhile, the refined floating catchment area method resulted in heterogeneous accessibility indices above zero within the threshold distance and zero beyond the threshold distance. The study further revealed the preservation of demand and supply by the refined two-step floating catchment area method in the hypothetical scenario and Dodoma City Council. Thus, accessibility indices estimated by the refined two-step floating catchment area might be more accurate, realistic and reliable for water supply professionals and decision-makers.