Research of basin water balance and water conservation variation based on multi-source data: a case study of Xiaoluan River Basin in Bashang plateau

Water moves among sea, atmosphere, ice and lithosphere, which is described as water cycle or hydrology cycle.In the context of global change and anthropogenic influence since the industrial revolution, unbalanced relationship between input water and output water leads to water resource conserved or short, consequently spatial distributing variously.In this study, long time meteorology and surface water data were obtained from 2001 to 2020, groundwater and land cover were surveyed, soil water data from remote sensing retrieval were collected, and actual evapotranspiration data were generated by ETWatch model.All of these data were applied to water balance accounts in order to illustrate dynamic balanced relationship between precipitation, actual evapotranspiration, runoff and variable storage, as well as analyze water conservation distribution from viewpoints of soil water and groundwater, in order to understand hydrological process conversion, locate key protective ecological space and solve water resource management problems in water conservation zone.Results showed that in Xiaoluan River Basin: (1)Precipitation increased with a trend of 3.76 mm/a, slowly from 2001 to 2015 while fast from 2016 to 2020 and exhibited spatial variability, decreasing gradually from east to west, with the highest value in Saihanba Forest Farm located in the northeast of the basin.(2)Actual evapotranspiration increased with a trend of 2.71 mm/a, lower than that of precipitation.It was lower than precipitation in years with more precipitation, when water was reserved or supplied to evaporate and transpire in later years with less precipitation.The spatial distribution was characterized as "high-low-high" from upper to lower reaches.Actual evapotranspiration of wetland>forest>cultivated land>construction land>grass>sandy and naked land.(3)Runoff decreased with a trend of 0.13 mm/a.The decreasing rate of wet season was greater than that of the whole year, while it showed an increasing trend in dry season, certificating a significant "reducing flood peak and compensating for the drought" effect.(4)Variable storage increased with a trend of 1.17 mm/a in spite of negative value and more and more water resource were stored in the form of soil water and groundwater.Soil water increased with a trend of 0.0018(m³/m³)/a and exhibited spatial variability, decreasing from upper to lower reaches, with the highest value in the ecotone of forest and grass located in the west-north of the basin.Since 2010, high soil water zone stretched from middle to lower reaches.Groundwater maintained stable with a slight rise.The area of groundwater level rising zone was larger than that of falling zone, with high level from August to September.Researching method of water balance in small basin was explored at the view of integrated survey and monitoring, providing support for water resource integrated management.