Estimation of Evapotranspiration and Other Soil Water Budget Components in an Irrigated Agricultural Field of a Desert Oasis, Using Soil Moisture Measurements

Abstract

Abstract. An accurate assessment of soil water budget components (SWBCs) is necessary for improving irrigation strategies and optimizing the use of fertilizer in any water-limited environment such as the desert oases in arid northwestern China. However, quantitative information of SWBCs is usually challenging to obtain, because, since the water cycle is principally driven by irrigation (I), drainage (D), and evapotranspiration (ET) in desert oasis settings, none of the drivers can be easily measured under actual conditions. Soil moisture is a variable that integrates the water balance components of land surface hydrology, and the evolution of soil moisture is assumed to contain the memory of antecedent hydrologic fluxes, and thus can be used to determine SWBCs from a hydrologic balance. A database of soil moisture measurements from six experimental plots in the middle Heihe River Basin of China (NT1 to NT6, designed to investigate the long-term effects of cropping systems and agronomic manipulation on soil property evolution in the ecotone of desert and oasis) was used to test the potential of a soil moisture database in estimating the SWBCs. The experimental plots were treated as continuous pasture cropping, maize cropping, maize cropping with straw return, maize-maize-pasture rotation, maize-pasture rotation, and maize-pasture intercropping. We first compared the hydrophysical properties of the soils in the plots, including soil bulk density (ρb), vertical saturated hydraulic conductivity (Ks), and soil water retention features, and then determined evapotranspiration and other SWBCs through a data-driven method that combined both the soil water balance method and the inverse Richards function. Our results showed that although the tillage and planting of the past decade have significantly increased the soils' water-holding ability, the magnitude of increase in most of the parameters was independent of the treatments applied across the plots. Despite the relatively flat topography and consciously uniform irrigation, significant variances were observed among the plots in both the cumulative irrigation volumes (between 652.1 mm at NT3 and 1186.5 mm at NT1) and deep drainages (between 170.7 mm at NT3 and 651.8 mm at NT1) during the growing season of 2016. Obvious correlation existed between the volume of irrigation and that of drained water. However, the ET demands for all the plots behaved pretty much the same, with the cumulative ET values ranging between 489.1 and 561.9 mm for the different treatments in 2016, suggesting that the irrigation amounts had limited influence on the accumulated ET throughout the growing season. This work also confirmed that relatively reasonable estimations of the SWBCs in a desert oasis environment can be derived by using soil moisture measurements, and the results will provide a great potential for identifying appropriate irrigation amounts and frequencies, and thus move toward sustainable water resources management, even under traditional surface irrigation conditions.

Soil Water Movement and Groundwater Recharge Under Different Land Uses in a Flood‐Irrigated Area

“…The middle soil was leaching water to the soil below it but at the same time it was receiving water from the soil above it, which resulted in the slower rates of SWCs decrease at 70 and 100 cm depth than those at the top part (20 and 30 cm). The similar patterns of changes in SWCs were observed in irrigated agricultural field of a desert oasis in Northwest China (Li et al 2018).…”

Evaluating performance of soil water movement and groundwater recharge in an irrigated agricultural area of Yinchuan Plain, China

“…The middle soil was leaching water to the soil below it but at the same time it was receiving water from the soil above it, which resulted in the slower rates of SWCs decrease at 70 and 100cm depth than those at the top part (20 and 30cm). The similar patterns of changes in SWCs were observed in irrigated agricultural field of a desert oasis in Northwest China (Li et al, 2018).…”

Irrigation Amounts and Timing Retrieval through Data Assimilation of Surface Soil Moisture into the FAO-56 Approach in the South Mediterranean Region

“…The potential of microwaves in irrigation mapping is actually related to their sensitivity to SSM through the dielectric properties of the soil [17,18]. Several studies have also demonstrated the potential of microwave observations including SSM products for irrigation detection [11,[19][20][21]. Kumar et al [22] were the first to use SSM for irrigation mapping by exploiting the differences between coarse-resolution microwave SSM products (ASCAT, AMSR-E, SMOS, WindSat and ESA CCI) and SSM modeled by a land surface model that does not account for irrigation.…”