Drought propagation and construction of a comprehensive drought index based on the Soil and Water Assessment Tool (SWAT) and empirical Kendall distribution function ( K C′): A case study for the Jinta River basin in northwestern China

Abstract

Monitoring drought and mastering the laws of drought propagation are the basis for regional drought pre vention and resistance. Multivariate drought indicators con sidering meteorological, agricultural and hydrological infor mation may fully describe drought conditions. However, se ries of hydrological variables in cold and arid regions that are too short or missing make it difficult to monitor drought. This paper proposed a method combining Soil and Water As sessment Tool (SWAT) and empirical Kendall distribution function (KC0) for drought monitoring. The SWAT model, based on the principle of runoff formation, was used to sim ulate the hydrological variables of the drought evolution pro cess. Three univariate drought indexes, namely meteorologi cal drought (standardized precipitation evapotranspiration in dex; SPEI), agricultural drought (standardized soil moisture index; SSI) and hydrological drought (standardized stream flow drought index; SDI), were constructed using a para metric or non-parametric method to analyze the propagation time from meteorological drought to agricultural drought and hydrological drought. The KC0 was used to build a multi variable comprehensive meteorology agriculture hydrology drought index (MAHDI) that integrated meteorological, agri cultural and hydrological drought to analyze the characteris tics of a comprehensive drought evolution. The Jinta River in the inland basin of northwestern China was used as the study area. The results showed that agricultural and hydro logical drought had a seasonal lag time from meteorologi cal drought. The degree of drought in this basin was high in the northern and low in the southern regions. MAHDI proved to be acceptable in that it was consistent with histor ical drought records, could catch drought conditions charac terized by univariate drought indexes, and capture the occur rence and end of droughts. Nevertheless, its ability to charac terize mild and moderate droughts was stronger than severe droughts. In addition, the comprehensive drought conditions showed insignificant aggravating trends in spring and sum mer and showed insignificant alleviating trends in autumn and winter and at annual scales. The results provided theo retical support for the drought monitoring in the Jinta River basin. This method provided the possibility for drought mon itoring in other watersheds lacking measured data.