Drought propagation and construction of a comprehensive drought index based on the SWAT-<i>K</i><sub>C'</sub>: A case study for the Jinta River basin in Northwestern China
Abstract. Reliable drought monitoring and mastering the laws of drought propagation are the basis for regional drought prevention and resistance. Multivariate drought indicators considering meteorological, agricultural, and hydrological information may fully describe drought information; however, too short or missing hydrological variables in cold and arid regions make it difficult to monitor drought. This paper proposes a method combining SWAT and empirical Kendal distribution function (KC') for drought monitoring. The SWAT model, based on the principle of runoff formation, was used to simulate the hydrological variables of the drought evolution process. Three univariate drought indexes, namely meteorological drought (SPEI), agricultural drought (SSI), and hydrological drought (SDI) were constructed using parametric and non-parametric methods to analyze the propagation time of meteorological drought to agricultural drought and hydrological drought. The KC' was used to build a multivariable comprehensive Meteorology–Agriculture–Hydrology Drought Index (MAHDI) that takes into account meteorological, agricultural and hydrological drought to analyze the characteristics of a comprehensive drought evolution. The Jinta River in the inland basin of northwest China was used as the study area. The results show that agricultural and hydrological drought have a seasonal lag time for meteorological drought. The degree of drought in the river basin is high in the northern and low in the southern regions. The MAHDI captured drought conditions characterized by a univariate drought index; however, the ability to characterize mild and moderate droughts is stronger than severe droughts. The index also captured the occurrence and end of drought time; therefore, it is an acceptable comprehensive drought index. In addition, the comprehensive drought conditions showed insignificant drought trends in spring and summer, and showed insignificant warm and humidification trends in autumn, winter and annual scale. The results provided theoretical support for the drought control in the Jinta River Basin. This method may be applied for drought monitoring in other watersheds with a shortage of measured data.