the quality variations of the drinking water sources in the rural regions of sabzevar county in a five year period

background and purpose: water is the most important limiting factor of sustainable development. poor quality of water sources and lack of appropriate management in some regions are the main reasons of water crises in the country. this study was conducted to assess water sources quality and the trend of their change in rural area of sabzevar county in a five year period. materials and methods: in total 43 sources of water in villages or complexes with more than 700 population were selected randomly and their physico-chemical and microbiological variables were studied. for microbiological characteristics 801 samples from those 43 sources were taken and examined in a five year period. results: the results showed that the average microbial contamination of all 801 samples from 43 sources during a five year period was 12.3 with a variance of 13.3. total dissolved solids (tds) index was 349.02 ppm with variance of 193.704 ppm. in three sources, the tds index had statistically significantly difference with the maximum level of 500 ppm. the maximum limit of ec of water from wells in a three years period has increased from 2526 in year 1 to 3213 in year three of study. among 43 sources of rural drinking water, just one source, with average 4.7± 3.9 ppm had statistically significantly difference with the upper limit maximum of 1.5 mg per litter. conclusion: having positive result of e-coli in some of water sources and high level of some physico-chemical indexes and the increasing trend of declining quality of water sources in a five year period of study, therefore creating a gis based data bank of water quality for continues monitoring of change in water quality, improvement and filtration of some sources, and replacement with a sources of better quality are essential.