Forecasting Variations and Trends in Water-Main Breaks

Effective planning for the renewal of water distribution systems requires accurate quantification of the structural deterioration of water mains. Direct inspection of all water mains in a distribution system is almost always prohibitively expensive. Identifying water-main breakage patterns over time is an effective and inexpensive alternative for gauging the structural deterioration of a water distribution system. While the structural deterioration of the pipe is generally considered to be a steady, monotone process, some of the environmental and operational stresses acting upon it are time dependent, steady, or transient. These stresses result in sets of "noisy" breakage rate data that often mask the underlying deterioration (aging) patterns, especially in small data sets. If the cause of these random stresses can be identified and attributed to measurable phenomena (for example, temperatures, precipitation, and so on), a more accurate pipe deterioration pattern can be obtained. Further, better predictions of water-main breakage could be made if these phenomena could be forecast with any degree of accuracy. A method is presented for analyzing how breakage rate patterns of water mains are affected by time-dependent factors. The method is versatile enough to consider any number of underlying factors, but the solution becomes more complex and more data are required as the number of factors increases. A case study is presented to demonstrate the method. Several time-dependent factors were examined, some of which were found to be significant contributors to the time variation of breakage rates.