Insights into water sustainability from a grey water footprint perspective in an irrigated region of the Yellow River Basin

Water sustainability is imperative for socio-economic development. The grey water footprint (GWF) is a useful indicator for quantifying how human activities influence freshwater systems. This study identified the change in GWF for Yinchuan City, an agricultural region in the Yellow River Basin, by the validation of acquired waterquality data. The driving forces of the GWF were analyzed using the logarithmic mean division index (LMDI) decomposition method. The results indicated that the total GWF showed a declining trend during the study period between 2002 and 2017 within the range of 12.6-21.5 x 10(8) m(3)/yr. The agricultural GWF had a relatively stable contribution (30-40%), and the focus should be on the increased proportion of domestic sector in this irrigated region. Economic development and technology effects were the dominant negative and positive factors, respectively, behind the decline in GWF. Although the water pollution levels (0.06-0.12) indicating that the waste assimilation capacity was sufficient to take up the pollutant load, the effect of pollution load on groundwater was cause for concern based on the actual water-quality data. A significant increase in NO3-N in the phreatic water was detected between 2003 and 2013. The dominance of NH4-N for the water supply wells in confined aquifers hinted at the deteriorating water quality, which was attributed to the aquifer leakage under pumping conditions. This study better reflected the current water pollution situation by combining GWF with understanding of the hydrological cycle and the actual water-quality data. Findings in this study will be valuable for addressing water quality threats and to develop sustainability strategies for local authorities.