Numerical Model Assessment of Radial-Well Aging

There are 99 radial wells at Belgrade's groundwater source which lies along the banks of the Sava River. The capacity of this source has been declining over time due to two dominant processes: riverbed colmation and well aging. Both have resulted in substantial additional well-maintenance costs. Aging of radial-well laterals is a result of physical, chemical, and biochemical processes which depend on a number of parameters. The objective of the study presented in this paper was to assess changes in hydraulic losses at the entrance to the laterals due to colmation (clogging) of screen slots of the laterals in order to define the well-aging process and take timely action. Groundwater flow to a single well was numerically simulated using a three-dimensional model. Special software was developed for this purpose; in addition to standard groundwater flow calculations, it allows for geometry and spatial positions of well laterals to be specified in a user-friendly manner. This paper highlights reasons for developing the software and its special features. Model application and results are illustrated using a case study of a well which taps the alluvial aquifer of the Sava River and is part of Belgrade's water supply system.