Propagation of meteorological to hydrological drought for different climate regions in China

Investigating the Spatio-Temporal Variation of Soil Moisture and Agricultural Drought towards Supporting Water Resources Management in the Red River Basin of Vietnam

“…The mean air temperature in the wet season was much higher than those in the dry season and transitional months, subsequently leading to the larger evapotranspiration in the wet season than those in the dry season and transitional months. Both precipitation and air temperature had significant impacts on the soil moisture changes in the northeast and northwest regions, which was reported in other studies [6,9,13,17,[23][24][25][26][27]. However, the impact of temperature on soil moisture appeared to be larger than that of precipitation in the two regions, which was also reported in the previous study [28].…”

“…Meanwhile, most of the remaining areas of the northeast region are covered by the mixed forest. The previous studies [17,[44][45][46][47] have shown that forests could slow down the runoff and thus increase the infiltration, and subsequently increase the soil moisture. Thus, it is inferred that the mixed forest coupled with the relatively steep landform could be the key factors affecting the distribution of soil moisture in these areas.…”

“…In addition to the impacts of meteorological variables, according to [4], soil moisture variation is also impacted by other factors such as (i) land cover type and vegetation, which affect the runoff, infiltration, and evapotranspiration through root water uptake [4,[29][30][31]; (ii) topography, which influences the runoff and infiltration [32,33]; and (iii) soil With respect to land cover and topography, the northeast region has the most dominant land cover and vegetation type is the mixed forest, followed by the cropland/grassland mosaic (Figure 4a) and the elevation decreasing from north to south (Figure 4b). The uppermost areas near the border with China are mainly covered by the cropland/grassland mosaic and have the mountainous and steep landform with an average elevation of 1000-1200 m. The cropland/grassland mosaic could favor soil evaporation and has the weak effect of slowing down the runoff [17,43] while the mountainous landform could facilitate the surface runoff and reduce the infiltration, which resulted in the low soil moisture in these areas for all three seasons (Figure 2). A similar condition could be observed for the lowermost areas of the northeast region with the mainland cover type is the cropland/grassland mosaic.…”

“…In the RRD region, the major land cover type is the irrigated cropland and pasture. The studies by [17,49,50] have shown that the regulation of surface runoff of cropland is poorer than that of forests. Furthermore, this region has a plain landform, which does not have a strong effect on the formation of surface runoff likes those in the other regions in the RRB.…”

“…The VIC model could realistically provide information on soil moisture status since it represents subgrid variability in soil moisture storage capacity by employing the spatial probability distribution function [9]. Despite various studies [9,11,[15][16][17] on soil moisture-based droughts conducted for many regions of the world, the knowledge on spatio-temporal variation and characteristics of agricultural drought in the RRB remains ambiguous so far. Currently, no soil moisture monitoring network is available to provide basic information on soil moisture conditions in the RRB.…”