Dendroclimatological Reconstruction of Streamflow Variability in a Small, Semi-Arid Mountain Catchment
Publication Date
12-2007
Type of Culminating Activity
Thesis
Degree Title
Master of Science in Geology
Department Filter
Geosciences
Department
Geosciences
Supervisory Committee Chair
David E. Wilkins
Abstract
Tree rings—the expression of annual cambial growth—from moisture-sensitive species can be used as non-linear biological proxies for streamflow variability as both streamflow and a tree's growth respond to or co-vary with precipitation inputs to a watershed hydrologic system. Many researchers have reconstructed streamflow using tree-rings with varying degrees of success, explaining ~ 70 to 80 percent of streamflow variability in sub-continental (> 10,000 km2) to sub-regional (260 — 10,000 km2) basins, particularly in the drought-prone areas of western North America.
The objective of this study is to reconstruct streamflow with statistical validity in the Reynolds Creek Experimental Watershed (RCEW), a 239 km2, second- or third-order stream catchment located in the snowmelt-dominated Owyhee Mountains of southwest Idaho.
Tree-ring chronologies developed from Douglas-fir (Pseudotsuga menziesii {Mirb.} Franco), subalpine fir (Abies lasiocarpa {Hook.} Nutt.), western juniper (Juniperus occidentalis Hook.), and a set of aspect-limited series were tested for significant correlations with streamflow time series for the years 1966 to 1997 and three-site-averaged precipitation time series for the years 1962 to 1996, using correlation procedures in SAS. Significant correlations found between streamflow time series and tree-ring chronologies were investigated further using different curve fits for improvement of the correlations.
Transfer functions, from significant but moderate correlations between a one-year-lagged aspect-limited standard tree-ring chronology and gaged February cumulative streamflow (r = 0.5201, p < 0.01) and between gaged water year cumulative streamflow (r = 0.4036, p < 0.05), were used to reconstruct 110 years of streamflow. Precipitation, an independent dataset that was highly correlated with cumulative water year streamflow (r = 0.956, p < 0.0001), was used for model validation and resulted in weak but statistically significant correlations (r = 0.3575, P < 0.05 for the February reconstruction and r = 0.3870, P < 0.05 for the water year reconstruction).
Validation results explain only about a third of streamflow variability: This weak explanation of variability can be attributed to many factors, including a lack of sample depth in the chronologies as mature (older than 100 years) trees were scarce, a lack of sensitivity to soil moisture in the samples, the use of precipitation (a second order approximation) as a proxy for streamflow, and the possible presence of more prevalent limiting growth factors at sampling sites, such as temperature extremes in the high elevations, and site specific, non-climatic effects from logging practices and disease and insect attacks.
The scale of the study is also believed to be a contributing factor to the lack of variability explained in the tree-ring signal. Site specific local noise in the tree-ring data is assumed to be amplified in smaller catchments such as the RCEW as a result of less spatial distribution between trees sampled and a lack of sample depth.
Recommended Citation
Lenhartzen, Valerie Joy, "Dendroclimatological Reconstruction of Streamflow Variability in a Small, Semi-Arid Mountain Catchment" (2007). Boise State University Theses and Dissertations. 401.
https://scholarworks.boisestate.edu/td/401
