Abstract: Based on the 1-D water quality model of stream, which taking into account the continuous discharge of groundwater along the stream way, a new analytical solution is proposed by superposition theorem. According to this new analytical solution, parameters estimation of stream water quality model response to groundwater discharge is analyzed quantitatively. The solute concentration decays when the groundwater discharge, a spot of pollution source, enters to streams and moves to lower reaches. The influence of seriate line-source to the decay of solute concentration in streams is not simply equal to the addition influence of several point-sources. It refers to line-source when describing the water exchange between aquifers and streams. Taking Yinghe River, Anhui Province as an example, the study of the deviation degree of parameters estimation of stream water quality model due to groundwater discharge shows that, the influence of the groundwater discharge to the variation rule of solute long streams, which affects the comprehensive attenuation coefficient k greatly, cannot be described simply by k in theory.

Key words: groundwater, water quality modelling, water exchange, analytical solution