Soil-water storage to a depth of 5 m along a 500-km transect on the Chinese Loess Plateau

Soil-water storage (SWS) is an important indicator of the sustainability of regional water resources and is the foundation for developing strategies of land-use management around the world, especially in areas with deficits of soil water. An investigation of the characteristics of SWS at large regional scales can provide valuable information. We measured SWS and available soil-water storage (ASWS) to a depth of 5 m along a 500-km transect across two climatic regions on the Chinese Loess Plateau (CLP). SWS_{5 m} tended to decrease from southeast to northwest and was 320 mm higher in the subhumid than the semiarid zone. SWS_{5 m} and ASWS_{5 m} were lower in the dry than the rainy season, but SWS_{1 m} and ASWS_{1 m} did not differ significantly between the two seasons except in the 0-100 cm layer. SWS_{1 m} and ASWS_{1 m} tended to increase with depth in the semiarid zone and did not change substantially with depth in the subhumid zone. SWS_{5 m} and ASWS_{5 m} varied with land use, in the orders cropland > orchard > forest in the subhumid zone and grassland > shrubland > forest in the semiarid zone. Climatic conditions and soil textures were predominant factors affecting SWS at the transect scale. SWS_{5 m} and ASWS_{5 m} in the subhumid zone were dependent on clay content, elevation, latitude and the interaction of latitude and temperature, while clay content played a dominant role in the semiarid zone. Understanding this information is helpful for assessing regional water resources, optimizing the rational use of land and modeling eco-hydrological processes on the CLP and possibly in other water-limited regions around the world.