Vegetation and Hydrologic Response to Climate in the Great Basin

Abstract:

Ongoing drought in the Great Basin is a likely portent of future conditions with questions asked on water resource and ecosystem sustainability given increased temperatures and reduced winter snowpack. Research highlights the combined use of integrated models and remote sensing products to explore inter-annual climate variability and its impact on the relationship between vegetation vigor and hydrologic response in semi-arid landscapes. Hydrologic response to the current drought is shown to be similar to a moderate, decadal drought observed during 1952-1961; with moderate droughts expected to increase in frequency over the next century and move hydrologic conditions closer to the equivalent of the most severe drought observed in the 20^th century. Vegetation water use in groundwater dependent ecosystems is explored in the context of soil moisture and depth to groundwater, as well as type and water use efficiency of upland vegetation. A case study illustrates that hydrologic sensitivity of meadow groundwater levels to upland woody-plant encroachment depends on precipitation falling out of phase with potential evapotranspiration; and weathered/fractured bedrock having the capacity to store water to sustain deep rooted plant transpiration during seasonally dry periods. Results suggest the meadow groundwater levels operate on a threshold response to precipitation greater than 400 mm per year and are highly responsive to small changes in upland vegetation and climate. Use of remote sensing in conjunction with integrated hydrologic models provides insight on the complex interplay between climate, vegetation, and hydrology.