Tracer test in Hobøl Creek, Norway, under different flow conditions

The current paper describes a repetition of a tracer test using tritiated water in Hobøol Creek, Norway, under two markedly different flow conditions in August and in October 2002. By carefully fitting a one-dimensional model of the solute transport in the creek, various mixing parameters could be evaluated and compared between the two occasions. The change in residence time in and exchange rate with the hyporheic zone caused by the difference in flow could be well accounted for in terms of the "pumping" theory. The pumping theory represents the hydromechanics of the exchange flow. Further, we found that at least 70% mass recovery is needed to provide an accurate evaluation of model parameters and this can only be achieved up to a limited stream distance.