Microbiological irrigation water quality of the Marchfeld canal system.

The Marchfeld basin with a size of approximately 1000 km2 represents the Austrian "granary". To prevent shortage of water as a result of increased ground water removal for irrigation, industrial purposes and drinking water supply, a canal being 18 km in length was constructed from the Danube to the center of the Marchfeld. From there, water is further distributed via two creeks (Russbach and Stempfelbach). This study was intended to evaluate whether the surface water of the Marchfeld canal system can be classified into hygienic-microbiological categories as proposed by DIN (Deutsche Industrienorm) standards for irrigation water. For this purpose, water sampled monthly from three different sampling sites from 1996 to 1999 was examined for E. coli and enterococci. In addition, water samples were examined for salmonella twice a year from 1996 to 1998 and for cryptosporidia six times during the year 1999. Though the water showed varying degrees of fecal load, the results of the examinations revealed that only one of the three sampling sites showed constant quality levels according to the DIN classification system over prolonged periods of time. However, exceeding of the limit values was occasionally observed indicating the need for regular bacteriological examinations. The high variation of the results from the other sampling sites hardly permits a definite classification in one of the quality classes.