VARIATION IN THE RELATIONSHIP BETWEEN SNOWMELT RUNOFF IN OREGON AND ENSO AND PDO¹

Abstract

The value of using climate indices such as ENSO or PDO in water resources predictions is dependent on understanding the local relationship between these indices and streamflow over time. This study identifies long term seasonal and spatial variations in the strength of El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) correlations with timing and magnitude of discharge in snowmelt streams in Oregon. ENSO is best correlated with variability in annual discharge, and PDO is best correlated with spring snowmelt timing and magnitude and timing of annual floods. Streams in the Cascades and Wallowa mountains show the strongest correlations, while the southernmost stream is not correlated with ENSO or PDO. ENSO correlations are weaker from 1920 to 1950 and vary significantly depending on whether Southern Oscillation Index (SOI) or Niño 3.4 is used. PDO correlations are strong from 1920 to 1950 and weak or insignificant other years. Although there are not consistent increasing or decreasing trends in annual discharge or spring snowmelt timing, there are significant increases in fractional winter runoff that are independent of precipitation, PDO, or ENSO and may indicate monotonic winter warming.

Pacific Decadal Oscillation and the Hydroclimatology of Western Canada—Review and Prospects

“…Hanson et al (2004) showed that streamflow, baseflow, and groundwater levels in the Mojave River basin all vary with the PDO but with varying lags and relationships. Beebee and Manga (2004) found that PDO is correlated with spring snowmelt timing and magnitude, spring and summer runoff, and timing of annual floods in Oregon rivers. The strongest correlations were found in the Cascades and Wallowa Mountains, whereas discharges for the southernmost Oregon streams considered in that study were not correlated with PDO or ENSO.…”

“…However, PDO influence in that region has decreased since 1950 as ENSO correlations have strengthened. Winter © 2010 Canadian Water Resources Association and Environment Canada discharge has not increased during the recent warm phase of PDO, suggesting that warming has been insufficient to increase snowmelt in winter (Beebee and Manga, 2004). Jain and Lall (2000) related trends in flood magnitude and timing to ENSO and PDO climate indices for the Black Fork River in Utah.…”

Seasonal flows of international British Columbia-Alaska rivers: The nonlinear influence of ocean-atmosphere circulation patterns

“…Many of the specific hydroclimatic processes inferred, such as higher autumn-winter streamflows or earlier snowmelt freshets under warmer air temperatures, have been widely observed either in this region, or alternatively in other areas of western North America (e.g., [3,22,25,68]). Our inference of higher-thannormal precipitation and streamflow in fall and early winter during ENSO and PDO warm phases is opposite to what is observed for the Pacific Northwest (PNW; [54,58]), to the south of our study area.…”

The association between climate teleconnection indices and Upper Klamath seasonal streamflow: Trans‐Niño Index

“…These large-scale indices are not intended to capture the natural chaotic component of weather but have been shown to characterize the offshore marine atmosphere, which in the western US drives the seasonal onshore weather patterns. Past research has shown that certain large-scale climate variables have a significant relationship to western US hydrology (Mantua et al, 1997;McCabe and Dettinger, 2002;Beebee and Manga, 2004;Gedalof et al, 2004;Grantz et al, 2005;Tootle et al, 2005;Bonsal et al, 2006;Kingston et al, 2006;Kingston et al, 2007).…”

“…Other studies have looked at the relationship between large-scale climate teleconnections and weather or hydrologic phenomena (e.g. Mantua et al, 1997;McCabe and Dettinger, 2002;Beebee and Manga, 2004;Gedalof et al, 2004;Grantz et al, 2005;Tootle et al, 2005;Bonsal et al, 2006;Kingston et al, 2006Kingston et al, , 2007, but these have either not explicitly studied the Klamath Basin, or those that have considered the region have not found a related teleconnection index. In the present study, a teleconnection index related to the hydrology of the Klamath Basin has been found and incorporated into statistical streamflow forecasting models.…”