A modified soil water deficit index (MSWDI) for agricultural drought monitoring: Case study of Songnen Plain, China.

Available soil water in the root zone is an essential component of the water balance process since it greatly affects the crop water uptake and crop growth. In this study, a modified soil water deficit index (MSWDI) was established on the basis of the concept of readily available water (RAW), with the accumulated effect considered. This modified index was applied in six agro-meteorological stations in Songnen Plain of China to monitor the agricultural drought. The results showed that: 1) The MSWDI showed similar spatial and temporal agricultural drought patterns as its inherent indices, such as the soil water deficit (SWD), soil moisture deficit index (SMDI) and atmospheric water deficit (AWD), but exhibited a delay between atmospheric and soil water processes; 2) The MSWDI has a better correlation with the crop yield than its inherent indices. For example, its overall correlation coefficient is about 0.6 with the crop yields among six study stations and −0.7 for the number of droughts, while their corresponding values are 0.5 and −0.6, 0.5 and −0.6, and 0.3 and −0.4 for SMDI, SWD and AWD, respectively; 3) The MSWDI could also identify a slightly higher number of reported drought events during the 2000–2012 in comparison with SMDI, SWD and AWD, although it also over-predicts the number of drought events same as other indices. It mainly comes from the uncertainty of reported drought events. The proposed index can be used for agricultural drought monitoring and provides a useful tool for agricultural meteorology and water resource management. [ABSTRACT FROM AUTHOR]