Abstract: Grey water footprint, a novel concept for water quality evaluation, offers a new idea for quantitatively describing the relationship between water quality and water quantity. In actual calculation, however, the results are often not accurate enough as the severity of water pollution in some period of time is ignored in no consideration of time dimension. In view of this, a calculation and assessment method for grey water footprint in consideration of time dimension is proposed: the grey water footprint and water pollution level in dry season, normal-flow season and wet season of each year are calculated, respectively; in subsequence, the sustainability of grey water footprint in each time period is evaluated based on water pollution level. Results demonstrate that the water pollution level in different time dimensions vary sharply; in particular, the results in consideration of dry season, normal-flow season and wet season are more consistent with the actual situation. In conclusion, compared with traditional method taking account of interannual grey water footprint, the proposed method in this paper is more accurate and effective in evaluating the sustainability of grey water footprint and in reflecting the actual water pollution in each period.

Key words: grey water footprint, time dimension, water pollution level, water quality evaluation, upstream of Dahuofang reservoir