Changes in flow regimes of the Yellow River in the Headwater Area of the
Yellow River on the northeastern Qinghai-Tibet Plateau, SW China during
1955-2040
Abstract
Human disturbance has substantially altered real-time flow regimes. The
Headwater Area of the Yellow River (HAYR, above Huanghe’yan Hydrological
Station) on the northeastern Qinghai-Tibet Plateau, Southwest China has
been undergoing extensively streamflow changes, permafrost degradation
and ecological deterioration under a warming climate. However, the
damming of the Yellow River complicates examining the relations between
hydroclimatic variables and streamflow dynamics. In this study, monthly
streamflow of the Yellow River (YR) at the Huanghe’yan Hydrological
Station is reconstructed for 1955-2019 dusing the double mass curve
(DMC) method and then forecasted for the next 20 years (2020-2040) using
Elman Neural Network (ENN) time-series method. Construction of dam
(1998-2000) has caused a reduction of 53.5%-68.4% in annual streamflow
and a reduction of 71.8 %-94.4% in annual streamflow of dry years
(2003-2005) in the HAYR and recent dam removal (September 2018) has
boosted annual streamflow by 123% -210% (2018-2019). Post-correction
trends of annual maximum (QMax) and minimum (QMin) streamflows and the
ratio of the QMax/QMin of the YR in the HAYR (0.18 and 0.03 m3s1yr1
and -0.04 yr1) compared to those of pre-correction values (-0.25,
-0.004 m3s1yr1 and 0.001 yr1) have revealed hydrological impacts of
degrading permafrost. Based on the ENN model predictions, over the next
20 years, the increasing trend of the YR flow in the HAYR would
generally be accelerated at a rate of 0.42 m3s1yr1. Boosting rates
of spring (0.57 m3s1yr1) and autumn (0.18 m3s1yr1) YR flow would
see an advance of snow-melt season and delayed arrival of winter. This
suggests an elongating growing season, which indicates ameliorating
phonological and soil nutrient and hydrothermal environments for
vegetation in the HAYR. These hydrological and ecological change trends
in the HAYR may potentially improve ecological safety and water supplies
security in the HAYR and downstream YR basins.