Although an invisible component of the hydrologic cycle, groundwater
generally takes precedence over other water resources in the area of
drinking water supply. Among groundwater resources, karst aquifers tend to
be rich in sufficiently-accessible amounts of high-quality water. During
most of the year, this water requires only disinfection prior to delivery to
the end user. However, in many cases extreme rainfall and/or sudden snow
melt results in transient turbidity, increase in bacterial count and
temporary contamination (e.g. increase in nitrate and phosphate
concentrations). To be able to determine the effect of the precipitation
regime on various groundwater quality parameters, it is necessary to
establish continuous monitoring of the parameter of interest and certain
parameters should be observed at least once a day, if not more often
(continuously). Such monitoring provides sufficiently long time-series of
the considered parameter, so that autocorrelation and cross-correlation
analyses can be undertaken and AR, CR and ARCR modeling used for simulations
and short-term forecasts. Apart from the theoretical background, the paper
presents a case study of the occurrence of nitrates at a karst spring called
?Banja? near the city of Valjevo, Serbia. A ten-year (1991-2000) timeseries
of the discharged volume of water was used in the study, as well as nitrate
concentrations recorded on a daily basis. In addition, daily precipitation
was gauged in the immediate vicinity of the catchment and the rainwater
chemically analyzed. The analyses included nitrate concentrations in
precipitation. The generated timeseries were used for autocorrelation and
cross-correlation analyses of nitrate concentrations in the Banja Spring
pool during the entire period of monitoring, as well as in one wet and one
dry year. The results are presented for all three cases, based on
simulations applying AR, CR and ARCR modeling.
Influence of groundwater quality indicators on nitrate concentrations in the Zagreb aquifer system
