Reconstructing Flow History From Riparian Tree Rings

Science Center Objects

Aquatic Systems Branch scientists analyze rings of riparian trees relating tree growth and establishment to historical flow. We then use the tree rings to reconstruct the flow in past centuries. Flow reconstructions discover the frequency and magnitude of past droughts and floods—information that is essential for management of rivers and water supplies. We also use downscaled climate projections and watershed models to predict changes in flow and tree growth resulting from human-induced climate change. We have pioneered the use of cottonwood, a dominant riparian species, for tree ring analysis; this is a significant advance in arid regions where old trees of other species are scarce. Ongoing studies focus on rivers of the Upper Missouri Basin and the Tarim River in China.

Plains cottonwood (Populus deltoides subsp. monilifera).
Plains cottonwood (Populus deltoides subsp. monilifera). Cottonwood forests dominate river flood plains in dry regions of North America, Asia and Europe. Flood-plain cottonwoods are widely distributed and long-lived and have distinct annual rings highly correlated with river flow. Photo by USGS. Public domain.
A plains cottonwood, with increment borer used to collect a 1 cm core, and a paper straw used to transport it
A plains cottonwood, the increment borer used to collect a core 1 cm in diameter, the core, and a paper straw used to transport the core. Photo by Derek Schook. Public domain.
Photomicrograph of tree rings in a core from the flood plain of the Little Missouri River in Theodore Roosevelt National Park
Photomicrograph of tree rings in a core from the flood plain of the Little Missouri River in Theodore Roosevelt National Park, North Dakota. Ring width of this cottonwood tree was reduced by drought in 1931, 1934, 1936 and 1937. Photo by Jesse Edmondson. Public domain.
Reconstruction of log-transformed April-July Flow of the Little Missouri River near Watford City ND
Reconstruction of log-transformed April-July Flow of the Little Missouri River near Watford City ND, gage 06337000, in the North Unit of Theodore Roosevelt National Park. This reconstruction is based on cores of plains cottonwood from the North Unit and from the lower Powder River near Moorhead, MT. Blue line is measured log of discharge, red line is reconstructed log of discharge, and black line is 15-yr smoothing spline. Spline is dashed where confidence in the reconstruction is low because of small sample size. Shaded area is the number of cores in each year. From Schook et al. 2016. Public domain.

Shapefiles and Historical Aerial Photographs, Little Missouri River, 1939-2003

This dataset includes aerial imagery of the Little Missouri River in the North Unit of Theodore Roosevelt National Park, ND from 1939 to 2005, as well as shape files delineating the channel in each image. These data were analyzed in: 

Miller, J.R., and J.M. Friedman. 2009. Influence of flow variability on flood-plain formation and destruction, Little Missouri River, North Dakota. Geological Society of America Bulletin 121:752-759.

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