Covariability of climate and stream flow in the Upper Rio Grande from interannual to interdecadal timescales - PDF

Study region:
The Upper Rio Grande (URG) flows from its headwaters in Colorado, U.S., and provides an important source of water to millions of people in the U.S. states of Colorado, New Mexico, Texas, and also Mexico.
Study focus: We reassess the explanatory power of the relationship of sea surface temperatures (SST) on URG streamflow variability on interannual to interdecadal timescales. We find a significant amount of the variance of spring-summer URG streamflow cannot be fully explained by SST.
New hydrological insights: We find that the interdecadal teleconnection between SST and streamflow is more clear than on interannual timescales. The highest ranked years tend to be clustered during positive phases of the Pacific Decadal Oscillation (PDO). During the periods ofdecadal high flow (1900 – 1920, and 1979 – 1995), Pacific SST resembles a positive PDO pattern and the Atlantic a negative Atlantic Multidecadal Oscillation (AMO) pattern; an interbasin pattern shown in prior studies to be conducive to high precipitation and streamflow. To account for the part of streamflow variance not explained by SST, we analyze atmospheric Reanalysis data for the months preceding the highest spring-summer streamflow events. A variety of atmospheric configurations are found to precede the highest flow years through anomalous moisture convergence. This lack of consistency suggests that, on interannual timescales, weather and not climate can dominate the generation of high streamflow events.

REFERENCE

Pascolini-Campbell, M.A., R. Seager, A. Pinson and B.I. Cook, 2017: Covariability of Climate and Upper Rio Grande Streamflow. J. Hydrology: Regional Studies 13, 58-71, doi.org/10.1016/j.ejrh.2017.07.007.

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Causes of Interannual to Decadal Variability of Gila River Streamflow over the past Century - PDF

Study region: The Gila River, New Mexico, is characterized by two peaks in streamflow: one in the winter–spring (December–May), and summer (August–September). The region is influenced both by Pacific SST variability as well as the North American Monsoon. Study focus: The mechanisms responsible for the variability of the winter–spring and summer streamflow peaks are investigated by correlation of streamflow with precipitation and sea surface temperature for 1928–2012. Decadal variability in the flow record is examined for a longer term perspective on Gila River streamflow using tree ring-based reconstructions of the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Index (SPI). New hydrological insights for the region: Results indicate a strong influence of winter–spring precipitation and Pacific SST anomalies on the winter–spring streamflow, with El Nino˜ conditions in the Pacific causing increased precipitation and streamflow. Decadal Pacific variability helps explain the transition from high winter flow in the late 20th century to lower flows in the most recent decade. The summer streamflow has a somewhat weaker correlation with precipitation and Pacific SST than the winter–spring streamflow. Its variability is more likely influenced by local North American Monsoon precipitation variability. PDSI and SPI reconstructions indicate much more severe and extended periods of droughts and pluvials in past centuries as well as periods of concurrent winter and summer drought.

REFERENCE

Pascolini-Campbell, M.A., R. Seager, D.S. Gutzler, B.I. Cook and D. Griffin, 2015: Causes of Interannual to Decadal Variability of Gila River Streamflow over the past Century. J. Hydrol. Regional Sys., 3, doi:10.1016/j.ejrh.2015.02.013, 494-508.