Just received this from friend and OSU colleague Sean Fleming.
Solander KC, Bennett KE, Fleming SW, Gutzler DS, Hopkins EM, Middleton RS. 2018. Interactions between climate change and complex topography drive observed streamflow changes in the Colorado River Basin. Journal of Hydrometeorology, 19: 1637-1650. https://doi.org/10.1175/JHM-D-18-0012.1
Download SolanderEtAl_Journal_Hydrometeorology_2018
Abstract
The Colorado River basin (CRB) is one of the most important watersheds for energy, water, and food security in the United States. CRB water supports 15% of U.S. food production, more than 50 GW of electricity capacity, and one of the fastest growing populations in the United States. Energy–water–food nexus impacts from climate change are projected to increase in the CRB. These include a higher incidence of extreme events, widespread snow-to-rain regime shifts, and a higher frequency and magnitude of climate-driven disturbances. Here, we empirically show how the historical annual streamflow maximum and hydrograph centroid timing relate to temperature, precipitation, and snow. In addition, we show how these hydroclimatic relationships vary with elevation and how the elevation dependence has changed over this historical observational record. We find temperature and precipitation have a relatively weak relation (|r| < 0.3) to interannual variations in streamflow timing and extremes at low elevations (<1500 m), but a relatively strong relation (|r| > 0.5) at high elevations (>2300 m) where more snow occurs in the CRB. The threshold elevation where this relationship is strongest (|r| > 0.5) is moving uphill at a rate of up to 4.8 m yr−1 (p = 0.11) and 6.1 m yr−1 (p = 0.01) for temperature and precipitation, respectively. Based on these findings, we hypothesize where warming and precipitation-related streamflow changes are likely to be most severe using a watershed-scale vulnerability map to prioritize areas for further research and to inform energy, water, and food resource management in the CRB.
Cutting to the chase....
Conclusion
We empirically quantified key climatic drivers of annual Qmax and annual CT, the dependence of these hydroclimatic relationships with elevation, and linear trend rates in the elevation dependence relationships over the past 60 years in the CRB. Our results indicate a threshold elevation of 2300 m, above which correlations between temperature, precipitation, and streamflow were generally strong (jr2j . 0.50). Given that this elevation threshold aligns with the locations where snow plays an important role in streamflow, we conclude that changes in snow and snowmelt from warming are largely driving the variability in annual Qmax and annual CT. The mean elevations at which Qmax and CT exhibit a strong sensitivity to April–May temperature variability are increasing by up to 4.8 and 2.2 m yr−1, respectively, suggesting that warming-induced changes in snowmelt or phase shifts in snow are changing the relationship between climate and streamflow within the CRB.
Based on our findings and because warming trends are expected to continue, more severe changes in streamflow are anticipated in the future, particularly for CRB watersheds above the critical elevation threshold of 2300 m or those immediately downgradient. These regions are highlighted for the CRB in a vulnerability map that depicts watersheds where water resources are likely to be most vulnerable to changes in annual Qmax and annual CT. Such an analysis is useful for targeted management improvements to address energy, water, and food supply concerns. Simulating these changes within hydrology and climate models coupled to energy, water, and food supply or flood models will be necessary to pinpoint how these resources and critical infrastructure will be affected and to mitigate potentially associated economic or environmental losses using new river management and planning protocols.
May we live in interesting times (apologies to the Chinese).
Enjoy!
“The great thing in this world is not so much where you stand, as in what direction you are moving.”
- Oliver Wendell Holmes
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