REGIONAL STREAMFLOW REGIMES AND HYDROCLIMATOLOGY OF THE UNITED-STATES

The dominant regions of interannual streamflow variability in the Unit ed States are defined, and their seasonality and persistence character istics identified, using an orthogonally rotated principal components analysis (RPCA) of a climatically sensitive network of 559 stream gage s for the period 1941-1988. This classification of streamflow regimes is comprehensive and unique in that separate analyses of the streamflo w record, for each month of the year, are carried out to detail the mo nth-to-month changes in the dominant streamflow patterns. Streamflow v ariations, or anomalies, in the Upper Mississippi, South Atlantic/Gulf , Far West, Ohio Valley, Northeast, and Eastern/Mid-Atlantic regions, as well as a pattern of opposing streamflow anomalies in the West, are observed in all seasons of the year. Anomalies in the Southern Plains and New England regions are observed in autumn, winter, and spring; t hose in the Rocky Mountains and Middle Mississippi regions occur in la te spring and summer.