Colorado River Basin Hydroclimatic Variability

Abstract

An analysis of annual hydroclimatic variability in the Upper Colorado River basin (UCRB) for the period of 1906-2006 was performed to understand the dominant modes of multidecadal variability. First, waveletbased spectral analysis was employed for streamflow at Lees Ferry, Arizona (aggregate location for UCRB flow), which identified two significant modes: a ''low frequency'' (;64-yr period) mode and a strong ''decadal'' (;15-yr period) component active only in recent decades. Subsequent investigation of temperature and precipitation data for the UCRB indicated that the low-frequency variability is associated with temperature via modulation of runoff efficiency while the decadal is strongly tied to moisture delivery. Simple hydrology and climate model experiments are also provided to support the aforementioned findings.Correlation of UCRB precipitation with global sea surface temperature (SST) anomalies showed a strong link with the equatorial and northern Pacific during periods of heightened variability of the decadal mode. The correlation of UCRB temperature with global SST anomalies showed strongest values in the Atlantic consistent with the Atlantic multidecadal oscillation mode. Wavelet spectral analysis of paleo-reconstructed streamflow at Lees Ferry shows both the low-frequency and decadal flow variability features. Furthermore, the strength of the decadal mode is modulated at an ;75-yr time scale, and these are consistent with epochal variations of overall streamflow variance.

Evidence that Recent Warming is Reducing Upper Colorado River Flows

“…The regression resulted in an adjusted coefficient of determination of 0.70 ( p , 0.0001), and the regression coefficients for both temperature and precipitation were statistically significant at p , 0.0001 (Table 1). These regression results are nearly the same as those obtained by Nowak et al (2012) who performed a regression of UCRB runoff against UCRB temperature and precipitation for the 1906-2006 period. The regression t values for water-year UCRB temperature and precipitation were 26.027 ( p , 0.…”

Runoff and Sediment Yield Variations in Response to Precipitation Changes: A Case Study of Xichuan Watershed in the Loess Plateau, China

“…Since the HRU is the basic spatial unit in the simulation, the spatial distribution of precipitation can be considered by inputting different precipitation data for different HRUs if more precipitation stations are available. (3) Due to the data availability, the precipitation scenarios were set using the empirical method, a method used by other researchers in this situation [21,23]. In future studies, efforts should be made to collect basic data and use climate output models to predict precipitation to conduct in-depth investigations on the trends of future climate change.…”

“…There are two types of predicted future climate change scenarios. First, changes in temperature, precipitation, and evaporation are hypothesized based on the trends and ranges of the meteorological changes in the study area, as well as specialized knowledge, experience, and the time-series statistical analysis method, which is easy to design and apply [21][22][23]; Second, different climate change scenarios can be simulated using models, such as the General Circulation Models [19,24].…”

Hydrology: The interdisciplinary science of water

“…From the analysis of paleoclimatic (tree ring) reconstructions [e.g., Woodhouse et al, 2006;Meko et al, 2007] of Colorado River hydrology, one notes nonstationary variations at interannual and multidecadal time scales driven by El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) [Nowak et al, 2012]. The hydrology of this large region responds to a combination of these factors, such that the long epochal periods with either a negative or a positive water anomaly may be punctuated by decade long periods that either amplify or dampen the century scale variation.…”