Assessment of watershed health propensity using reliability, resiliency, and vulnerability based-standard precipitation drought index and GIS: A case study of northern Maysan Governorate, southern Iraq

Abstract

Abstract A quantitative evaluation of watershed health based on climatic variability is essential for watershed management. This study used a well-known reliability, resiliency, and vulnerability water resources performance framework to assess watershed health for 7 transboundary sub-watersheds between Iraq and Iran, based on a standard precipitation drought index (SPI). The assumption is that rainfall variability is one of the main climatic factors that affect watershed health. The grided monthly rainfall data of PERSIANN (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks) type for 37 water years (1981–2018) were used to calculate SPI and the RRV indicators were calculated with an SPI threshold of 0.1 adapted from previous studies. The non-parametric seasonal Mann-Kendall test and Sen’s slope estimator were used to investigate the trend and value of trend of rainfall and SPI dataset, respectively. The temporal and spatial variation of RRV and watershed health index (WHI) derived from RRV was mapped using geographic information system (GIS). Results revealed that rainfall data did not show any trend, while SPI showed a slightly decreasing trend. The findings of the study noted that RRV had the lowest values of 0.35, 0.19, and 1.45 for the 2017–2018 water year, while the highest values (0.96, 0.99, and 21.06) were recorded for the 1991–1992 node year. Based on the calculated RRV values in most years of the study, all sub-watersheds were considered unhealthy from the standpoint of SPI. Based on the spatial analysis, the northern and northeastern sub-watersheds had less rainfall anomaly and thus appeared relatively healthy as compared to the other parts of the study area.