Ak. Guetter et Kp. Georgakakos, RIVER OUTFLOW OF THE CONTERMINOUS UNITED-STATES, 1939-1988, Bulletin of the American Meteorological Society, 74(10), 1993, pp. 1873-1891
A record of 50 years of daily outflows through the boundaries of the c
ontinental United States has been assembled based on observations reco
rded by U.S. Geological Survey streamflow stations. Only stations with
continuous records from 1939 through 1988 were included. These statio
ns (197 total) are near the outlets of rivers located at the vicinity
of the Canadian, Mexican, Atlantic (including the Gulf of Mexico), and
Pacific borders of the continental United States. The drainage area o
f the selected stations covers 77% of the conterminous United States,
whereas the existing network of gauging stations covers 83% of the con
terminous U.S. area. Station daily data were aggregated over the entir
e boundary of the United States and were integrated in monthly and ann
ual totals. The 50-year average annual streamflow divergence normalize
d by the aggregated drainage area is 210.2 mm yr-1, reaching a peak in
April with 27.3 mm month-1 and a minimum in September with 8.7 mm mon
th-1. The Mississippi-Missouri Basin comprises 50% of the gauged area
and dominates the absolute value of the outflow discharge. Spectral an
alysis of the monthly outflow anomalies shows an 11-year dominant cycl
e. The 1939-1988 period contains four notable droughts. Two droughts a
re partially registered in the limits of the records characterized by
the negative anomalies extending from 1939 to 1941 and by the 1987-198
8 anomalies for the late 1980s drought. The middle 1950s and early 196
0s droughts are fully included in the dataset. Periods of high outflow
s were registered in the middle 1940s, early 1970s, and early 1980s. A
nalysis of the spatial coherence of the annual anomalies shows large-s
cale features, whereas analysis of the monthly anomalies yields the fr
equency and persistence patterns of floods and droughts. An estimate o
f the climatological land-surface water budget for the continental Uni
ted States was done based on recorded precipitation, panevaporation, a
nd outflow. Eigenvector analysis of the monthly outflow residuals per
3-degrees range has been performed to identify the major modes of the
spatial correlation structure. The first eight modes explain 66% of th
e variance of the system and identify the following regions: Atlantic
seaboard, Mississippi-Missouri and Ohio River basins, Northeast, Pacif
ic Northwest, Pacific seaboard, Texas Gulf region, North-central, and
the Colorado River and Great Basin. Annual and monthly specific outflo
w aggregates were used to describe the temporal characteristics of the
coherent regions. Both time-domain and spectral analyses of the regio
nal outflow anomalies identify the dominant modes of temporal variabil
ity.