Spatial-temporal variability of soil water content in a cropland-shelterbelt-desert site in an arid inland river basin of Northwest China

Abstract

a b s t r a c tKnowledge of the spatial-temporal variability of soil water content (SWC) is critical for understanding a range of hydrological processes. In this study, the spatial variance and temporal stability of SWC were investigated in a cropland-shelterbelt-desert site at the oasis-desert ecotone in the middle of the Heihe River Basin, China. The SWC was measured on 65 occasions to a depth of 2.8 m at 45 locations during two growing seasons from 2012 to 2013. The standard deviation of the SWC versus the mean SWC exhibited a convex upward relationship in the shelterbelt with the greatest spatial variation at the SWC of around 22.0%, whereas a linearly increasing relationship was observed for the cropland, desert, and land use pattern. The standard deviation of the relative difference was positively linearly correlated with the SWC (p < 0.05) for the land use pattern, whereas such a relationship was not found in the three land use types. The spatial pattern of the SWC was more time stable for the land use pattern, followed by desert, shelterbelt, and cropland. The spatial pattern of SWC changed dramatically among different soil layers. The locations representing the mean SWC varied with the depth, and no location could represent the whole soil profile due to different soil texture, root distribution and irrigation management. The representative locations of each soil layer could be used to estimate the mean SWC well. The statistics of temporal stability of the SWC could be presented equally well with a low frequency of observation (30-day interval) as with a high frequency (5-day interval). Sampling frequency had little effect on the selection of the representative locations of the field mean SWC. This study provides useful information for designing the optimal strategy for sampling SWC at the oasis-desert ecotone in the arid inland river basin.

Evaluation of remote sensing‐based evapotranspiration estimates using a water transfer numerical simulation under different vegetation conditions in an arid area

“…Additionally, Galleguillos, Jacob, Prevot, French et al (), Galleguillos, Jacob, Prevot, Lagacherie, et al () claimed HYDRUS‐1D could provide continuous daily AET simulations calibrated with weekly, biweekly, or monthly soil profiles. The spatial–temporal variability of soil moisture in an oasis‐desert transition area in the Heihe River Basin showed that the spatial pattern of soil moisture was temporally stable and that different observation frequencies (5‐day and 30‐day intervals) showed similar characteristics of temporal stability for soil moisture (Shen et al, ). In addition, soil moisture products derived from different methods (in situ measurements, passive microwave remote sensing, MODIS (Moderate Resolution Imaging Spectroradiometer) soil moisture estimates, and soil water balance models) were highly correlated with each other (Gan & Gao, ).…”

“…In this study, the soil profile of each site was categorized into one to three horizons according to in situ observations. In accordance with the soil horizon texture, the bulk density was estimated using expert knowledge and the results of earlier studies conducted within our study area (Shen, Gao, Hu, & Fu, ; Yi et al, ). Generally, the variation coefficients of bulk density were less than 10% for all land cover types (Li & Shao, ).…”

“…The first irrigation after sowing was conducted during day of year (DOY) 142–148 for all farmland sampling sites. Forest in the oasis margin was irrigated once during May to June with 200–300 mm of water (Shen et al, ; Zhang, Shao, & Li, ).…”

“…The first irrigation after sowing was conducted during day of year (DOY) 142-148 for all farmland sampling sites. Forest in the oasis margin was irrigated once during May to June with 200-300 mm of water (Shen et al, 2016;Zhang, Shao, & Li, 2017 AET was calculated at a daily time step using the METRIC model in two steps. First, the instantaneous AET during a satellite overpass was calculated using the residual surface energy balance method based on pixel-wise estimations of net radiation, soil heat flux, and sensible heat flux:…”

Real-Time Management of Groundwater Resources Based on Wireless Sensors Networks

“…In the Daman irrigation district, the groundwater level has dropped 20 m due to unconstrained groundwater exploitation. A number of studies have tried to tackle the groundwater resources management problems using scenario analysis [4,5]. However, selecting the optimal operational procedure or policy is extremely difficult because of the complexity of groundwater systems and relatively limited onsite studies.…”