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Characterizing Drought Behavior using Unsupervised Machine Learning for Improved Understanding of Future Drought in the Colorado River Basin
  • Carl James Talsma,
  • Katrina E. Bennett,
  • Velimir V Vesselinov
Carl James Talsma
Los Alamos National Lab
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Katrina E. Bennett
Los Alamos National Lab

Corresponding Author:[email protected]

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Velimir V Vesselinov
Los Alamos National Laboratory (DOE)
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Abstract

Drought is a pressing issue for the Colorado River Basin (CRB) due to the social and economic value of water resources in the region and the significant uncertainty of future drought under climate change. Here, we use climate simulations from various Earth System Models (ESMs) to force the Variable Infiltration Capacity (VIC) hydrologic model and project multiple drought indicators for the sub-watersheds within the CRB. We apply an unsupervised machine learning (ML) based on Non-Negative Matrix Factorization using K-means clustering (NMFk) to synthesize the simulated historical, future, and change in drought indicators within the sub-watersheds. The unsupervised ML approach can identify sub-watersheds where key changes to drought indicator behavior occur, including shifts in snowpack, snowmelt timing, precipitation, and evapotranspiration. While changes in future precipitation vary across ESMs, the results indicate that the Upper CRB will experience increasing evaporative demand and surface-water scarcity, with some locations experiencing a shift from a radiation-limited to a water-limited evaporation regime in the summer. Large shifts in peak streamflow are observed in snowmelt-dominant sub-watersheds, with complete disappearance of the snowmelt signal for some sub-watersheds. Overall, results indicate a concerning increase in drought risk. The work demonstrates the utility of the NMFk algorithm to efficiently identify behavioral changes of drought indicators across space and time. Our unsupervised ML approach can be applied to other spatiotemporal data to process and understand vast arrays of data associated with climate impacts analysis of hydrologic change, assisting planners to rapidly assess potential risks associated with extreme events.