Water balance-based approach to improve understanding of Drought Development

Abstract

This work provides a water balance-based approach to improve understanding of drought trends by calculating root storage deficits in the United States. To do this, data is ultimately compiled from 1125 watersheds for the years 2001 to 2016. The root storage deficit is then determined using iteratively optimized transpiration values minus the water available to plants and compared to the latent heat of the FLUXCOM energy fluxes data. The stimulus for this work is a better understanding of desiccation processes. Answers to this are given only indirectly. For example, no concrete consequences can be derived from the calculated root storage deficits. Further-more, it turns out that the water cycle-based approach provides clearly interpretable results only for catchments with sufficient water supply. Thus, increasingly arid catchments do not satisfy the general conditions required for the calculations. Catchments in which the root storage deficit exceeds one meter are declared as ever-growing deficit. In these catchments an increased dry-ing process is to be assumed. In all other catchments, temporally congruent developments are shown for both applied methods. Due to the increased dependence on incoming precipitation, calculations performed with the CHIRPS dataset were repeated with the CRUNCEP dataset. This turns out to be generally smaller but confirms the drying processes suggested by the CHIRPS dataset. In contrast, the extents of drying suggested for both methods differ by up to 972 mm for the CHIRPS precipitation dataset, with holistically calculated root storage deficit maxima differing by an average of 178mm. This work is nonetheless useful because otherwise only grid dataset-based and thus statistically adjusted approaches are common in climatological science. Thus, the water cycle-based approach provides a concrete application of the raster values to point measurements.