Spatial modelling of water pipe bursts in Harare, Zimbabwe

Abstract

Water is a scarce commodity whose availability and utilisation requires diligent planning, distribution and management to ensure its proper use and protection in the interest of humankind and other ecological balances. Currently, Zimbabwe is facing problems of persistent droughts, increasing competition within and between sectors due to increasing demand, imbalances in access to water between consumers and industrial activities, commercial farmers. Therefore, water conservation policy and planning procedures need to be to backed by strong scientific research findings. It is in this context that the main objective of this study was to model pipe burst hazard in the Harare fresh water supply pipe systems as a function of pipe related and terrain factors. Specifically, the study identified pipe leaks and used logistic regression to test whether the leak locations were a statistically significant of pipe age, water pressure, pipe material, as well as terrain factors such as slope. The study also spatially modelled the pipe leak hazard, that is, probability of a leak occurring at a place as a function of factors that significantly explain pipe leaks using logistic regression in a GIS environment. Harare water pipes were digitized in a GIS based system, burst points were collected using GPS and non-burst points were randomly sampled in a GIS based system. A Digital Elevation Model (DEM) of the study area was generated from the map of 1:2500. Map gaps were filled using 90m by 90m DEM using co-Kriging. Pipe age, material, location, type of material and other relevant information was obtained through interviews from Zimbabwe National Water Authority (ZINWA) staff. Results of the research indicated that there was a significant relationship (p<0.05) between pipe related factors such as pressure, slope terrain, pipe material and age.