Contributions of Water and Total Nitrogen of Inflow Rivers to West
Dongting Lake Linked to the Yangtze River Using Major Ion Tracing
Abstract
West Dongting Lake (WD) receives water from local rivers, the Yuan and
Lishui Rivers, within the lake basin and is recharged by the Yangtze
River outside the basin through three outfalls. Thus, water pollution
control is more complicated in WD than in lakes disconnected from the
Yangtze River. Here, major ion tracing which was a method rarely applied
in the river-lake system was used to characterize the contribution of
water and total nitrogen (TN) from the inflow rivers to WD, and 9
sampling sites in WD and its inflow rivers were investigated in December
2016 (the dry season, DS), April 2017 (the normal season, NS) and August
2017 (the wet season, WS). Na+ and Cl- were suitable tracer ions used
in the ion tracing model to estimate the water and TN contributions from
inflow rivers to WD. Results showed that the water and TN in WD who
presented river and lacustrine phases were mainly contributed by local
rivers rather than the three outfalls, in which the contribution of Yuan
River was larger than that of Lishui River. However, the contribution
rates of water and TN of the three outfalls to WD during WS reached
above 20% and 30% respectively, indicating that the contribution of
the three outfalls could not be ignored, in which the contributions of
water and TN from Songzi outfall were higher than those from Taiping and
Ouchi outfalls. Therefore, we suggest that the relevant departments
should identify key river management targets during different water
periods, implement refined management over water pollution in WD, and
prioritize the pollutant input of Yuran River and Songzi outfall
(especially during WS).