Spatiotemporal variations of groundwater level and gully impact in two
peatland watersheds in the Source Region of the Yellow River
Abstract
The spatiotemporal variability of groundwater level (GWL) is an
important property of peatland hydrology that directly affects
fluctuations of water storage. Nonetheless, current understanding of the
variations of GWL in different time scales still remains unclear. In
this study, two peatland watersheds (0.151 km 2 for W1
and 0.844 km 2 for W2) in the Zoige Basin in the
Source Region of the Yellow River (SRYR) were selected for monitoring
the temporal variability of GWL using self-recorded water loggers during
2017-2021. The main results demonstrate that: (1) GWL variations tended
to be controlled by gully drainage in sites adjacent to the gully and be
more synchronized with rainfall in sites distant from the gully. The GWL
near the gully that cuts through the peat layer was lower than that near
the gully without cutting through the peat layer, with a maximum
difference between the former and the latter of 58.3 cm, indicating the
effect of longitudinal attenuation of the GWL in W1. (2) Because
rainfall had a lag effect on the GWL, the length of lag gradually
decreased with increased rainfall intensity (i.e., the lag time of sites
far away from the gully was about 18 min shorter than that of sites
close to the gully in W1). (3) The peak values of the GWL occurred
simultaneously with the maximum and minimum rainfall in W2, and the peak
occurrence time was related to the ratio of precipitation to
evaporation. In the downstream sites, GWL fluctuated more intensively
than the upstream ones in W2. Moreover, the average GWL of the upstream
sites was 14.3 cm higher than that of the middle ones, indicating a
decreasing trend of water storage along the gully. (4) The GWL
discrepancy between wet and dry seasons was explicit, but the difference
was smaller in the upstream sites due to limited gully incision and
higher water storage within the peat layer. Additionally, rainy days
dominate the GWL change in wet and dry seasons, but the different
rainfall intensity resulted in a stable GWL in the dry season and an
oscillating GWL in the wet season in W2. This study uncovers the
spatio-temporal variation of groundwater level in two peatland
watersheds, which is of great significance for understanding runoff
variation, ecohydrological processes, and wetland shrinkage in the SRYR.