SUITABILITY OF BROMIDE AS A TRACER FOR WA TER AND NITRATE MOVEMENT INTHE EVAPOTRANSPIRATION ZONE OF SOILS WITH HIGH LEACHING RISK

A simplified soil water model was used in order to determine the amoun t of seepage water and solute transport in the evapotranspiration zone . Studies, which used bromide as a tracer, were conducted during the g rowing period of winter wheat and maize on alluvial soils in the water protection area of Augsburg, southern Bavaria. The estimation of the amount of seepage water was based solely on the meteorological paramet ers air temperature, relative humidity, amount of rainfall plus field and available water capacities. Leaching of the tracer was determined by bromide concentration in the bottom most soil layer, measured in 14 -day intervalls, together with the simulated amount of seepage water. Tracer leaching ranged from 1 % to 22 % of the amount applied, while 5 0 % to 70 % remained in the soil. The plant biomass contained 30 % to 47 %, most of which was in vegetative parts. The nearly complete recov ery of the tracer indicates that the method used allows a practical me ans of determining solute losses out of the evapotranspiration zone. T he use of easily measurable meteorological parameters, and the calcula tion with solute concentrations measured in short intervals, should al low the calculation of solute losses in other drinking water resource areas with relatively little effort.