Spatial variability and temporal stability of actual evapotranspiration on a hillslope of the Chinese Loess Plateau
ZHANG Yongkun1, HUANG Mingbin2,*()
1State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining 810016, China 2Institute of Soil and Water Conservation, Northwest Agriculture and Forestry University, Yangling 712100, China
Actual evapotranspiration (ETa) is a key component of water balance. This study aimed to investigate the spatial variability and time stability of ETa along a hillslope and to analyze the key factors that control the spatiotemporal variability of ETa. The potential evaporation, surface runoff and 0-480 cm soil water profile were measured along a 243 m long transect on a hillslope of the Loess Plateau during the normal (2015) and wet (2016) water years. ETa was calculated using water balance equation. Results indicated that increasing precipitation during the wet water year did not alter the spatial pattern of ETa along the hillslope; time stability analysis showed that a location with high time stability of ETa could be used to estimate the mean ETa of the hillslope. Time stability of ETa was positively correlated with elevation (P<0.05), indicating that, on a hillslope in a semi-arid area, elevation was the primary factor influencing the time stability of ETa.
ZHANG Yongkun, HUANG Mingbin. Spatial variability and temporal stability of actual evapotranspiration on a hillslope of the Chinese Loess Plateau. Journal of Arid Land, 2021, 13(2): 189-204.
Fig. 1Sampling sites in (a) Liudaogou watershed and (b) layout of 38 soil water content monitoring locations spaced at 5 m intervals on a hillslope. Surface runoff experimental plots and evaporation pans at the upper (sampling site, 1-13), middle (sampling site, 14-27), and lower (sampling site, 28-38) slope positions.
Property
Soil profile (cm)
Statistical parameter
Slop position
Upper
Middle
Lower
ELE (m)
Max
1170
1151
1140
Min
1152
1141
1131
Mean±SD
1159±4.72a
1146±3.83b
1136±3.13c
Slope (°)
Max
24.32
16.56
9.21
Min
34.10
25.43
16.23
Mean±SD
27.69±2.90a
22.69±3.09b
12.12±2.07c
Ks (cm/h)
0-30
Max
6.20
7.66
6.31
Min
1.57
1.97
0.89
Mean±SD
3.00±1.52a
3.76±1.78b
2.52±1.65a
BD (g/cm3)
0-30
Max
1.61
1.73
1.74
Min
1.25
1.32
1.13
Mean±SD
1.39±0.09a
1.48±0.1a
1.53±0.11a
LAIm (m2/m2)
Max
1.86
2.32
2.96
Min
0.62
0.61
0.55
Mean±SD
1.13±0.33a
1.56±0.22b
1.47±0.25b
Clay (%)
0-200
Max
16.62
16.26
16.80
Min
9.42
12.33
5.46
Mean±SD
13.56±2.24a
14.70±1.2a
12.97±3.15a
Silt (%)
0-200
Max
40.33
41.71
42.44
Min
26.55
31.58
15.59
Mean±SD
35.26±4.94a
37.20±2.89a
31.57±7.28a
Sand (%)
0-200
Max
64.02
55.65
78.95
Min
43.32
42.69
40.76
Mean±SD
51.19±7.01a
48.10±4.00a
55.46±10.38a
Table 1 Soil properties, topographic attributes, and vegetation features at different slope positions along the hillslope
Fig. 2Distributions of daily precipitation and temperature in the study area during the observation period in 2015 and 2016
Fig. 3Comparisons of potential evapotranspiration (PET) values respectively calculated by evaporation pan and penman equation at the upper slope position on the hillslope
