Drought Propagation in Contiguous U.S. Watersheds: A Process‐Based Understanding of the Role of Climate and Watershed Properties

Abstract

Drought impacts on the society and environment are influenced by how droughts propagate through the hydrologic cycle; however, the physical processes involved in drought propagation are not well understood. In this study, a physically based hydrologic model is used to understand the drought propagation mechanisms and their controlling factors in multiple watersheds selected from different regions of the contiguous United States (CONUS). The characteristics of hydrologic droughts are found to be significantly different in three regions of the CONUS: (1) western U.S. watersheds have long and intense streamflow droughts, (2) Great Plains and southwest U.S. watersheds have low intensity and duration of streamflow droughts, and (3) eastern U.S. watersheds have short but intense streamflow droughts. This spatial pattern of hydrologic drought characteristics is found to coincide with the pattern of climate properties. Highly seasonal recharge driven by winter precipitation or snowmelt leads to longer streamflow droughts in the western United States; whereas humid climate with low seasonality in the eastern United States leads to shorter streamflow droughts. Furthermore, the storage-discharge relationship is identified as a key watershed property which controls the intensity of hydrologic droughts. Higher sensitivity of baseflow to watershed storage in the western and the eastern U.S. watersheds leads to more intense streamflow droughts in these regions. In the Great Plains and southwest United States, watersheds have a lower sensitivity of baseflow to catchment storage which, combined with the highly arid climate, leads to low variability in baseflow, and in turn results in low intensity of streamflow droughts in the region.

Characteristics of Propagation From Meteorological Drought to Hydrological Drought in the Pearl River Basin

“…(2019) analyzed the relationship between socioeconomic drought and meteorological drought in the Datong River Basin and found that El‐Niño Southern Oscillation (ENSO) had the greatest impact on drought propagation among several climate indices. However, global studies have found that there are various factors that can affect the drought propagation, including watershed properties, climate types and human activities (Apurv & Cai, 2020; Gevaert et al., 2018; J. F. Wu et al., 2017). Therefore, drought propagation usually has regional characteristics (N. C. Chen et al., 2020; R. H. Li, Chen, et al., 2020).…”

Regional Drought Risk in the Contiguous United States

“…The renewable water supply deficits during droughts are the highest in the Central US, followed by the Western US, and the lowest in the Eastern US watersheds. The renewable water supply deficits are the largest in the Great Plains region due to large water demands relative to the renewable water availability (Apurv & Cai, 2020), a major fraction of which is fulfilled from the unsustainable use of the deep groundwater from the High Plains aquifer (Scanlon et al., 2012). There is a stark contrast between the water supply drought characteristics in the Western and Eastern US watersheds.…”

“…where N is the number of water supply drought events, WSD i is the water supply deficit during the ith drought event and WD is the annual water demand in the year 2015 (Apurv & Cai, 2020). Figure 2 shows the results of the analysis of the multidecadal variability of meteorological droughts using the moving-window approach.…”

“…As can be seen, the hydrologic drought severity is high in the watersheds of Western US and Eastern US, and low in the watersheds of the Great Plains. The storage-discharge relationship in watersheds plays an important role in determining the severity of hydrologic droughts (Apurv & Cai, 2020). The low hydrologic drought severity in the Great Plains watersheds is due to the low sensitivity of discharge to storage, which buffers the impact of droughts on streamflow ( Figure S3b); while the high sensitivity of discharge to storage in the watersheds of the Western and Eastern US results in high hydrologic drought severity ( Figures S3a and S3c).…”

“…In the watersheds of Western US, there is an accumulation of streamflow deficits in successive years due to highly seasonal recharge and runoff generation, which results in both long duration and high severity of streamflow droughts (Apurv & Cai, 2020; Figure S3a). On the other hand, the duration of streamflow droughts is shorter in the Eastern US watersheds due to the strong control of precipitation over hydrologic drought onset and recovery in humid climate of this region (Apurv & Cai, 2020; Figure S3c).…”