Study catchment
Chenqi catchment is located in the Puding Karst Ecohydrological
Observation Station of Guizhou Province, southwest China, and has an
area of 1.25 km2 (Fig. 1). It is a typical cockpit
karst landscape, with surrounding conical hills separated by star-shaped
valleys (Zhang et al., 2011; Chen et al., 2018). The catchment, which is
drained by a single underground channel/conduit, can be divided into two
units: depression areas with low-elevation (<1340 m) and
steeper hillslopes with high elevation ranging from 1340 to 1500 m. The
site has a subtropical wet monsoon climate with mean annual temperature
of 20.1 °C, and the highest temperatures in July and lowest in January.
The annual precipitation is 1,140 mm, with a distinct wet summer season
from May to September and a dry winter season from October to April. The
average monthly humidity ranges from 74 to 78%.
Geological strata in the study basin include dolostone, thick and thin
limestone, marl and Quaternary soil. Limestone formations 150–200 m
thick lie above an impervious marl formation, which allows precipitation
to recharge perched groundwater on the marl that discharges in the lower
areas (mostly as hillslope springs). On hillslopes, Quaternary soils
developed on carbonate rocks are very thin, and the average soil
thickness is less than 30 cm. Some limestone fragments are mixed in with
the soils, and the rock outcrop area is 10–30%. The vegetation
characteristics include deciduous broad-leaved forest at the top and
middle of the hillslope and crops (including rice paddies) on the
depression where soils are also thicker.
At Chenqi, discharge of a hillslope spring (HS) located at the foot of
the eastern steep hillslope and the underground channel at the catchment
outlet were measured (Fig. 1). An automatic weather station was
established on the upper hillslope to record precipitation, air
temperature, wind, radiation, air humidity and air pressure.
Additionally, precipitation, hillslope spring discharge and catchment
outlet flows were sampled daily for hydrogen
and oxygen
isotopes analysis. These hydrometric and
isotopic data were used to analyze the seasonal cycles, and short-term
dynamics of stream water and precipitation isotopes and aid model
calibration.