Why Should New Mexico Dam Owners Care about Climate Change and Extreme Events

Dagmar Llewellyn, Reclamation Albuquerque Area Office

Presentation to the New Mexico Watershed and Dam Owners Coalition, 2015 Conference

May 12, 2015

Flash Floods

The Rio Grande, 2012

Elephant Butte Reservoir

Drought

Or both…..

Global Temperatures have been Increasing

Source: Ariane Pinson, US Army Corps of Engineers

Temperature Trends in the Upper Rio Grande Basin From 1971 to 2011 in the Rio Grande Basin, average temperature

increased by 0.7 F per decade, twice the global average.⁰

Source: Ariane Pinson, US Army Corps of Engineers

Source: Richard Alley, 2000

Stationarity assumes that the statistical properties of hydrologic variables in future time periods will be similar to past time periods

“Climate change undermines a basic assumption that historically has facilitated management of water supplies, demands, and risks.”

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Exponential relationship between air temperature and water-holding capacity

At higher temperatures, small change can lead to significant increases in water demand.

Higher evaporation from open water (rivers and reservoirs)

Higher water use by plants

Lower available water supply.

Warmer air holds more moisture, leading to increased intensity of precipitation.

Exaggeration of changes in the Extremes

Snowpack conditions in 2015

4°C

Saturation Vapor Pressure = 4.2 kPa

Actual Vapor Pressure = 2 kPa

Saturation Vapor Pressure = 3.2 kPa

Vapor-Pressure Deficit = 2.2 kPa (83% increase)

Source: Park Williams, currently of Lamont-Doherty Earth Observatory

Implications for Forests (where we slow runoff, and store water as snow)

Bark-beetle outbreak corresponded with major forest

drought stressdrought

No drought

Source: Park Williams, currently of Lamont-Doherty Earth Observatory

Photo: Peter Kolb

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Burned area correlates well with forest drought stress

drought

No drought

Source: Park Williams, currently of Lamont-Doherty Earth Observatory

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Str

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Feedbacks and Cascading Impacts

Las Conchas and its aftermath

Processes depicted in General Circulation Models

Basin-mean Climate Projections:Warmer, similar precipitation

Future Climate: Basin-Distributed Snow

2020s 2050s 2070s

Projected Impacts to Flow Timing

• Decreased annual runoff throughout basin• Spring runoff occurs earlier in the year

Developed by Alex Epstein, US Dept. of Transportation Volpe Center, for Futures 2040

Summer Monsoons…?Some evidence suggests that the summer monsoons on the Rio Grande may intensify under warmer conditions.

Climate Model Projections of Forest Drought-Stress Index (FDSI) through 2100

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Most severe 50% of years during 1200s and 1500s “Megadroughts”

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Source: Park Williams, currently of Lamont-Doherty Earth Observatory

Conclusions from Park William’s Work

• Temperature increases cause increased vapor-pressure deficit, and therefore increased drought stress on trees, regardless of species or location.

• Drought stress corresponds well with area killed by bark beetles, and area burned by wildfire.

• If climate models are correct, average drought stress by the 2050s will match that of the worst years during the largest mega-droughts in at least 1000 years.

• Water available for storage decreases over time• Greater energy in the atmosphere leads to more

intense precipitation events, and higher flood risk• Temptation to store water when it is available, but

one extreme precipitation event may come on the heals of the other, so this could present a flood risk.

• Risk of greater sedimentation in reservoirs, as well as in rivers upstream.

• Risk of sedimentation as well as debris flows increases along with the increasing risk of catastrophic wildfire.

Implications for Dam Owners

Credit: Guy and Rodd

Taking action under Uncertainty involves risk…but so does taking no action.

Uncertainty

Implications for Infrastructure of larger and more intense storms

Calabacillas Case Study (Gerhardt Schoener, SSCAFCA):• “A 10 percent increase in precipitation could lead to a 25

percent increase in peak discharge; a 25 percent increase in precipitation could lead to a 75 percent increase in flow. “

• “Higher peak discharge may overwhelm existing drainage infrastructure, as well as planned facilities designed based on current standards.”

Storm flows in the Calabacillas Arroyo overtopping Southern Blvd during the flood of September 13, 2013 (Source: koat.com).

Boulder Flood Study (Institute for Social and Environmental Transition, 2014)

• All systems will fail. Plan for “Graceful Failure”

• Use redundancy to prevent failure of critical infrastructure. Make sure redundant systems have different failure points.

• Build in diversity – multiple smaller systems