Event Title

Trends and Patterns in Streamflow Quantiles Associated with Characteristics of Large-Scale Climate Variations in the Western US

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

3-30-2011 2:20 PM

End Date

3-30-2011 2:40 PM

Description

The goal of this research is to better resolve trends and patterns in long-term streamflow records at sites across the Western US during the 20th and 21st centuries, specifically determining the relative contributions of the EI Nino/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and how rapidly they increase or decrease over time. Toward that goal, quantile regression was applied to: (a) identify trends and patterns in both the spread and central tendency of the streamflow distribution (e.g. different effects for wet years, median years, or dry years) between 1912 and 2010 at sites in the Western US; (b) determine the influence of EI Nino/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and their rates of change on trends and patterns of different portions of the streamflow distribution; and (c) distinguish geographical variations in effects of ENSO, PD~ and their rates of change on streamflow trends and patterns. USGS GAGES reference sites were evaluated for periods of record greater than 80 years, record completeness, and location. Six sites were selected for a pilot test to establish the methodology for large-scale analysis of the Western US. Climate conditions differed among the six sites, and their periods of record began in the early 1900's and continued through 2010. Preliminary results show that higher flows increased significantly (alpha = 0.05) at 50% of the pilot sites between 1912 and 2010, and at least 70% of the highest flows at each site occurred since 1960. PD~ and ENSO correlated positively with higher flows, yet results indicate no significant change in ENSO and PD~ during 1912-2010. Annual streamflow from different parts of the distribution (dry, medium, wet) correlated significantly with ENSO, PD~, and their rates of change. The relationships differed regionally according to whether flows were negatively or positively correlated with both PD~ and ENSO. Sites where streamflows correlated negatively with ENSOand PD~ were located in the area encompassing the northwest, eastward to Idaho and southeast into the Great Basin. On the other hand, site locations where flows correlated positively with ENSO and PD~ included the area including mid- to southern California and eastward to New Mexico. Pilot study results improved understanding of which portions of the streamflow distribution exhibited trends over the past century, and regional variations in streamflow trends and patterns. Results also revealed spatial patterns in relationships between streamflow and ENSO, PD~ , and rates of change in climate indices.

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Mar 30th, 2:20 PM Mar 30th, 2:40 PM

Trends and Patterns in Streamflow Quantiles Associated with Characteristics of Large-Scale Climate Variations in the Western US

Eccles Conference Center

The goal of this research is to better resolve trends and patterns in long-term streamflow records at sites across the Western US during the 20th and 21st centuries, specifically determining the relative contributions of the EI Nino/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and how rapidly they increase or decrease over time. Toward that goal, quantile regression was applied to: (a) identify trends and patterns in both the spread and central tendency of the streamflow distribution (e.g. different effects for wet years, median years, or dry years) between 1912 and 2010 at sites in the Western US; (b) determine the influence of EI Nino/Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and their rates of change on trends and patterns of different portions of the streamflow distribution; and (c) distinguish geographical variations in effects of ENSO, PD~ and their rates of change on streamflow trends and patterns. USGS GAGES reference sites were evaluated for periods of record greater than 80 years, record completeness, and location. Six sites were selected for a pilot test to establish the methodology for large-scale analysis of the Western US. Climate conditions differed among the six sites, and their periods of record began in the early 1900's and continued through 2010. Preliminary results show that higher flows increased significantly (alpha = 0.05) at 50% of the pilot sites between 1912 and 2010, and at least 70% of the highest flows at each site occurred since 1960. PD~ and ENSO correlated positively with higher flows, yet results indicate no significant change in ENSO and PD~ during 1912-2010. Annual streamflow from different parts of the distribution (dry, medium, wet) correlated significantly with ENSO, PD~, and their rates of change. The relationships differed regionally according to whether flows were negatively or positively correlated with both PD~ and ENSO. Sites where streamflows correlated negatively with ENSOand PD~ were located in the area encompassing the northwest, eastward to Idaho and southeast into the Great Basin. On the other hand, site locations where flows correlated positively with ENSO and PD~ included the area including mid- to southern California and eastward to New Mexico. Pilot study results improved understanding of which portions of the streamflow distribution exhibited trends over the past century, and regional variations in streamflow trends and patterns. Results also revealed spatial patterns in relationships between streamflow and ENSO, PD~ , and rates of change in climate indices.

https://digitalcommons.usu.edu/runoff/2011/AllAbstracts/34