Runoff and Evapotranspiration Elasticities in the Western United States: Are They Consistent With Dooge's Complementary Relationship?. Issue 8 (9th August 2020)

• Record Type: Journal Article
• Authors: Xiao, Mu; Gao, Ming; Vogel, Richard M.; Lettenmaier, Dennis P.
• Is Part Of: Water resources research. Volume 56:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-09
• Subjects: runoff elasticity; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2019WR026719
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Many studies have examined how runoff (Q) responds to long‐term changes in precipitation (P) and temperature (T), but the effects of potential evapotranspiration (PET) have received less attention. We examine observational data sets for P, T, and Q, along with PET estimated from observations, to determine the extent to which derived P and PET runoff elasticities (𝜀𝑃 and 𝜀𝑃𝐸𝑇, the fractional changes in runoff associated with given fractional changes in precipitation and PET, respectively) meet Dooge's complementary relationship (under certain conditions, 𝜀𝑃 + 𝜀𝑃𝐸𝑇 = 1). We apply three statistical methods and two hydrologic models to estimate 𝜀𝑃 and 𝜀𝑃𝐸𝑇 in 84 headwater river basins in California, Oregon, and Washington. We find that while the estimates of 𝜀𝑃 are generally consistent across two statistical estimators and one model‐based estimator, the estimates of 𝜀𝑃𝐸𝑇 using the statistical methods differ considerably (generally, they are much more negative) from the model‐based estimates, and some appear to be implausible. The model‐based estimates show better conformance to the complementary relationship (and in the median across sites, they sum to close to 1.0). We explore several factors that might explain the failure of the observation‐based estimators, including interaction between P and PET and nonclosure of the water budget at annual time scales. Key Points: Elasticities of runoff to precipitation are more consistent across basins than are runoff elasticities to potential evapotranspiration Complementarity in precipitation and potential evapotranspiration elasticities is better met in model‐ than observation‐based estimates Observation‐based PET elasticity estimates are more sensible when a complementary relationship constraint is imposed