Patterns of regional hydroclimatic shifts: An analysis of changing hydrologic regimes

Abstract

Temporal shifts in precipitation and runoff regime curves appear throughout the continental United States, but differ from region to region. This paper explores these regime shifts by building upon a hydroclimatic classification system that partitions the United States into clusters of similarly behaved catchments using four simple hydroclimatic indicators. Hydroclimate data from over four hundred catchments over a 55 year period (belonging to the MOPEX data set) are analyzed to reveal how the indicators have shifted before and after 1970, before and after 1975, and before and after 1980. Statistically significant hydroclimatic changes in these indicators are explored qualitatively, suggesting which catchments today might resemble other catchments tomorrow. Thus, a preview of current locations in one class under future conditions is provided by observing existing locations of another class. The classification system structure enables organization of these data, allowing patterns of regime change to emerge without highly specified models at each individual site. Regional analyses explore changes in mean seasonal precipitation/runoff regimes, including shifts in the daily variability of precipitation and runoff. Additionally, changes in regime curves of minimum and maximum precipitation/runoff observations are analyzed and discussed. Results indicate that after 1980, classifications typically found in the southeastern quarter of the United States have expanded northward and westward. Regionally, the Midwest and Rocky Mountains seem to demonstrate more frequent, but less intense storms after 1980, while southeastern catchments receive much less water in the form of precipitation and runoff than in previous years.

Understanding the Role of Climate Characteristics in Drought Propagation

“…However, the previous studies of drought propagation have not fully considered the effects of other climate characteristics, such as climate aridity and the timing of the precipitation within the year, on the propagation of droughts. Indeed, many studies of regional variations of catchment water balances have shown that climate aridity and the timing of precipitation with respect to potential evapotranspiration, as well as seasonality, can have a significant impact on both annual and seasonal water balances (Berghuijs et al, 2014;Coopersmith et al, 2014). For this reason, we present an extension of the drought propagation analysis by van Loon et al (2014) to include the effects of both climate aridity and the timing of precipitation.…”

Assessing baseflow index vulnerability to variation in dry spell length for a range of catchment and climate properties

“…The baseflow index (BFI), the ratio between the volume of baseflow and the volume of total streamflow, was originally recommended in the low flow studies (Institute of Hydrology, ) for indexing the effect of geology on low flows; however, the BFI now represents a general index of catchment hydrological response. Among various applications, BFI has been implemented as an index of river flow regime classification (Bejarano, Marchamalo, Garcia de Jalon, & Gonzalez del Tanago, ; Kennard, Mackay, Pusey, Olden, & Marsh, ; Olden, Kennard, & Pusey, ) and, as such, has also been used to detect hydrological regime changes along with other low flow indices (Coopersmith, Minsker, & Sivapalan, ; Crooks & Kay, ; Sawicz et al, ).…”

Identification of changes in floods and flood regimes in Canada using a peaks over threshold approach

“…Mudelsee et al (2003) report that there is no upward trend in floods in a small number of large European rivers. Coopersmith et al (2014) described changes in hydrologic regimes, including flood events, for the continental United States. Hodgkins et al (2015) assessed 1204 reference and reference-like hydrometric stations in North America and Europe and found no compelling evidence of consistent changes in major floods over the past 80 years.…”