Supplying safe drinking water is an essential issue in human societies since any development is
determined by the level of public health. Nowadays, preserving water supplies is gaining increasing importance
in international communities. While municipal tap water is mainly safe and drinkable, water preserved in supply
resources, tankers and air tanks is not suitable for drinking. These reservoirs are susceptible to microbial
contamination such that bacterial accumulation within 3 days reaches 15000 per ml, i.e., 150 times greater than
the limit (100 CFU/ml). Considering the fact that contamination of water supplies may naturally result from fecal
material, domestic and agricultural sewage, the first step in determining the quality of drinking water of
reservoirs is obtaining information about qualitative changes of water in terms of time and place and identifying
contamination factors, while performing appropriate tests for examining parameters affecting water safety. Based
on total coliform and fecal coliform, the present study undertakes to evaluate bacterial contamination of urban
and rural drinking water resources and reservoirs in Roudsar. Accordingly, 16 stations of water resources (wells
and springs) and reservoirs (from the ground and the air) were sampled in a pattern of monthly replication
covering a period of 5 months from September 2012 to January 2013. A total number of 80 samples was obtained,
which were tested in terms of parameters such as temperature, pH, turbidity, chlorine residual, microbial tests
including MPN and HPC, EMB culture, gram staining, observance under the microscope. For resources and
reservoirs where contamination was observed for several consecutive months, differential and selective tests
of IMViC were conducted. Data analysis was performed using SPSS and Excel. Average contamination indexes
of total coliform and fecal coliform in urban and rural stations of central Roudsar in a 5-month period were both
20%, while they were 38% and 25%, respectively, for rural stations.