Spatiotemporal water quality variations in the urbanizing Chongqing reach of Jialing river, China

Water quality in rivers usually exhibits markedly spatiotemporal variations as affected by the urbanization, while the magnitude of these effects remain unclear. This study aimed to investigate the spatiotemporal water quality variations in the urbanizing Chongqing reach of Jialing River and its tributary using a 6-yr multisite dataset (January 2010-December 2015). Water quality variables including pH, dissolved oxygen (DO), permanganate index (CODMn), ammonia nitrogen (NH3-N) and total phosphorus (TP) were deciphered. Results showed that the trunk river displayed respectively 1.2%, 39.8% higher pH and DO concentration but 66.9%, 94.7% and 85.2% lower CODMn, NH3-N and TP concentrations relative to the tributary (P < 0.05), due largely to the dilution effects occurring in the trunk river. Dry season presented respectively 1.3%, 18.2%, 102.8% and 32.5% higher pH, DO, NH3-N and TP concentrations than those in the wet season (P < 0.05). DO concentration showed significant inter-annual variations (P < 0.05), and CODMn, NH3-N and TP concentrations all presented markedly decline trends from 2010 to 2015 (P < 0.05). Significant relationships among the study variables were found in different spatiotemporal scales (P < 0.05). Our results are valuable to optimize strategies for sustainable water quality management in rivers experiencing urbanization worldwide.

Automated summary

This study investigated spatiotemporal variations in water quality in the urbanizing Chongqing reach of the Jialing River and its tributary. The trunk river had higher pH and dissolved oxygen concentrations but lower CODMn, NH3-N, and TP concentrations compared to the tributary. Dry season had higher pH, DO, NH3-N, and TP concentrations than the wet season. DO concentration showed significant inter-annual variations, and CODMn, NH3-N, and TP concentrations declined from 2010 to 2015. The study variables showed significant relationships in different spatiotemporal scales.