Tree-Ring Extension of Precipitation in Eastern Nevada and its Implications for Drought 
Analysis

In the Great Basin of North America, ecotonal environments characterized as lower forest 
border sites are ideally suited for tree-ring reconstructions of hydroclimatic variability. 
A network of 22 chronologies, some longer than 800 years, from single-leaf pinyon (Pinus 
monophylla) tree-ring samples for eastern Nevada, in the Great Basin of North America, 
provides a record of long-term precipitation variability. The period in common among all 
tree-ring chronologies, i.e. 1650-1976, was used to reconstruct October-May total 
precipitation using the Line of Organic Correlation (LOC) method. Individual site 
reconstructions were then combined using spatio-temporal kriging to produce 327 annual maps 
on a 12x12 km grid. Greater spatial variability emerged during wet periods, whereas dry 
spells were more synchronous over the landscape. The annual mean of the 315 grid point 
estimates was used to identify wet and dry episodes. The three driest years were 1934, 1879, 
and 1782, and the three wettest years were 1914, 1868, and 1726. To estimate the likelihood 
of severe and sustained drought, multi-year events were numerically identified using their 
duration, magnitude, and peak. At the annual time scale, the most remarkable episode in the 
entire reconstruction was the early 1900s pluvial, followed by the late 1800s drought. The 
1930s ‘Dust Bowl’ drought was in 8th position, making it a remarkable hydro-climatic episode 
for at least the past few centuries. After smoothing the annual values with a 7.5-year cubic 
spline to emphasize interannual variability, the early 1900s pluvial remained the strongest 
episode, but the 1930s drought became the second strongest one. Besides showing how regional 
drought severity varies across the Great Basin, these results directly address the needs of 
water managers with respect to planning for ‘worst case’ scenarios of drought duration and 
magnitude. For instance, it is possible to analyze which geographical areas and hydrographic 
basins are more likely to be impacted during the most extreme droughts, at annual or 
multiannual timescales AND at the km-spacing used by regional climate models.