Webinar: Forest Management and Warming Effects on southwestern US river flow

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Thursday, February 15, 2018
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1pm ET

Register now at https://attendee.gotowebinar.com/register/1910071987307779842

Presenter: Marcos Robles, Conservation Scientist at The Nature Conservancy, Center for Science and Public Policy

Recent studies suggest that climate change has altered the flow and provision of water from western US rivers to downstream cities and natural communities, but fewer studies have examined hydrological influences related to a century of fire suppression. This study evaluated the effects of changing forest and temperature conditions on 20th century flow patterns in the Salt River in central Arizona. After removing the influence of precipitation and temperature, seasonal and annual flows declined by 8-29% in the first half of the century. In the same time frame, fire suppression led to a 2-3-fold increase in median basal areas and canopy cover and a 10-fold increase in ponderosa pine forest densities. A literature review indicated that these forest structural changes could have resulted in lower water inputs to flow. In the 2nd half of the century, warmer temperatures and dense forest conditions did not lead to flow declines. Instead, warmer temperatures led to earlier timing of peak spring flows of almost 2 weeks and a 10-31% increase in climate-adjusted flows, perhaps due to more winter rainfall. These results suggest that forest change had effects on flow well before anthropogenic warming and that large-scale restoration projects hold some promise of recovering seasonal flows.