SAHRA Webcam on Mt. Bigelow updated every 5 minutes
Among the ecosystems present in the semi-arid environment of the southwestern US, Sky Island Forest is unique and it has a unique relationship to the sparse surface-water resources available in the region. This ecosystem exists only at the top of mountains because it is only here that, as a long-term average, precipitation input exceeds evapotranspiration to the extent that forest vegetation can survive. Sky Island Forests, therefore, command potentially significant source areas for the water (some originally falling as snow) that ultimately leaves topographically high ground to recharge aquifers in the plains below by mountain-front recharge. Quantifying and understanding water, energy and related
carbon cycling and budgets of this
sustainable source of water, is of direct
relevance to the mission of SAHRA.

Mount Bigelow Eddy Correlation Tower

The SAHRA Mount Bigelow project aims to provide an empirically based understanding of the hydro-micrometeorological dynamics of a sky island sub-alpine forest in the southwestern U.S.

The fundamental science issues in

question are:

  • the characteristics of the surface-atmosphere exchanges of water, energy and carbon.

  • the partitioning of winter snow and
    rain between evapotranspiration/ sublimation, deep drainage and the near-surface environmental water resource that sustains the forest.


In order to achieve our objective, a network of three below canopy hydro-micrometeorological stations 10 m tall, and one above canopy 30 m tall high resolution eddy correlation tower, were deployed within a predominantly douglas fir/pine second growth forest. This network will operate for a minimum of two years and ideally for the next seven years, in order to capture strong inter-annual climate variability, as well as to leverage on the GEWEX-CEOP related activities as their semi-arid sky island reference site for the larger basin modeling activities. The Mount Bigelow project is the first study to document, analyze, and model the water, energy, and (related) carbon exchanges of the Sky Island Forest ecosystem. The observations have year-round value. Data gathered in winter aids understanding of how water resources are replenished by winter snow and rain. Data collected in spring aids understanding of the partitioning of water between deep drainage and the near-surface environmental water resource that sustains the forest; while data gathered in the summer and fall aids understanding of the evolution of the environmental water resource as it is depleted by evapotranspiration but replenished by monsoon storms.

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