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Trends and shifts in streamflow in Hawaii, 1913-2008

Hydrological Processes

By:
,
DOI: 10.1002/hyp.9298

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Abstract

This study addresses a need to document changes in streamflow and base flow (groundwater discharge to streams) in Hawai'i during the past century. Statistically significant long-term (1913-2008) downward trends were detected (using the nonparametric Mann-Kendall test) in low-streamflow and base-flow records. These long-term downward trends are likely related to a statistically significant downward shift around 1943 detected (using the nonparametric Pettitt test) in index records of streamflow and base flow. The downward shift corresponds to a decrease of 22% in median streamflow and a decrease of 23% in median base flow between the periods 1913-1943 and 1943-2008. The shift coincides with other local and regional factors, including a change from a positive to a negative phase in the Pacific Decadal Oscillation, shifts in the direction of the trade winds over Hawai'i, and a reforestation programme. The detected shift and long-term trends reflect region-wide changes in climatic and land-cover factors. A weak pattern of downward trends in base flows during the period 1943-2008 may indicate a continued decrease in base flows after the 1943 shift. Downward trends were detected more commonly in base-flow records than in high-streamflow, peak-flow, and rainfall records. The decrease in base flow is likely related to a decrease in groundwater storage and recharge and therefore is a valuable indicator of decreasing water availability and watershed vulnerability to hydrologic changes. Whether the downward trends will continue is largely uncertain given the uncertainty in climate-change projections and watershed responses to changes.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Trends and shifts in streamflow in Hawaii, 1913-2008
Series title:
Hydrological Processes
DOI:
10.1002/hyp.9298
Volume
27
Issue:
10
Year Published:
2013
Language:
English
Publisher:
John Wiley & Sons
Contributing office(s):
Pacific Islands Water Science Center
Description:
17 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1484
Last page:
1500
Country:
United States
State:
Hawai'i