Are the North American deserts expanding? Some climate signals from groundwater storage conditions

Abstract

The areal average underground water storage in a natural catchment is directly manifested by the low flow or baseflow features from that catchment. Accordingly, an analysis was conducted of the annual lowest flows of twelve prototype near‐pristine river basins with long streamflow records and minimal confounding human activities in four deserts of North America, namely the hot Chihuahua, Sonora, and Mojave deserts and the cold Great Basin desert. Except possibly for those in the Sonora Desert, the analysis has revealed no evidence that these few remaining pristine watersheds have undergone consistent or significant negative terrestrial water storage trends over the past century in their riparian aquifers and therefore no evidence of any increase in their aridity. Thus, if groundwater conditions in these deserts have been deteriorating, this suggests that it is likely attributable to human activities rather than to climate change. The situation in the Sonora Desert is unclear, on account of remaining questions regarding human impact. The reliability of the methodology is further probed by comparing the shorter term groundwater changes in all four deserts with well‐known concurrent sea surface temperature changes in the Pacific Ocean; the groundwater storage changes appear to be related, albeit weakly, to the El Nino‐Southern Oscillation and to the Pacific Decadal Oscillation; in the three hot deserts, the El Nino‐Southern Oscillation effect decreases with eastward distance from the Pacific Ocean, but not that of the Pacific Decadal Oscillation. Copyright © 2011 John Wiley & Sons, Ltd.

Satellite‐derived estimates of forest leaf area index in southwest Western Australia are not tightly coupled to interannual variations in rainfall: implications for groundwater decline in a drying climate

“…To provide a robust measure for y that best reflects the annual value for basin storage, Brutsaert (, ) proposed use of the lowest 7 days daily mean flow, y L 7 . Brutsaert () provides detailed justification for setting K = 45 days and we adopt this operational value in this study. As noted by Brutsaert (), it is the sign and significance of the trends that are of significance and not their exact values.…”

“…Changes to the annual baseflow trend over time can be used to derive the trend in areal average underground storage ( S ) in a catchment using (Brutsaert, ) where K is a characteristic drainage timescale, also referred to as the storage coefficient, y = Q/A, the rate of flow of the stream per unit catchment area [LT −1 ], Q = Q ( t ), the volumetric rate of flow in the stream [L 3 T −1 ], and A is the area of the basin [L 2 ].…”

“…Brutsaert () provides detailed justification for setting K = 45 days and we adopt this operational value in this study. As noted by Brutsaert (), it is the sign and significance of the trends that are of significance and not their exact values.…”

“…In the case of a normal distribution, the JB statistic asymptotically has a chi-squared distribution with two degrees of freedom. Changes to the annual baseflow trend over time can be used to derive the trend in areal average underground storage (S) in a catchment using (Brutsaert, 2012)…”

Groundwater storage trends in the Loess Plateau of China estimated from streamflow records

“…Brabets and Walvoord (2009) investigated streamflow trends in the Yukon River basin of Alaska and Canada and found changes in streamflow patterns correlated with a PDO regime shift. More recently, Brutsaert (2012) found that the PDO and ENSO affected groundwater storage in four desert regions of North America. Kuss and Gurdak (2014) showed that groundwater levels in major aquifers in the U.S. are partially controlled by interannual to multidecadal climate variability with ENSO and PDO exerting a greater control than North Atlantic Oscillation and Atlantic Multidecadal Oscillation.…”