Abstract: Two maps, compiled at 1:1 million scale, depict mean annual runoff, precipitation, and evapotranspiration in the part of the United States east of Cleveland, Ohio and north of the southern limit of glaciation. The maps are mutually consistent in that runoff equals precipitation minus evapotranspiration everywhere. The runoff map is based on records of streamflow from 503 watersheds in the United States and southernmost Canada, adjusted to 1951-80 and supplemented by records of precipitation at 483 stations. Precipitation at each station was partitioned into point estimates of runoff and evapotranspiration, which were constrained such that the evapotranspiration estimates varied smoothly across the region and decreased with increasing latitude and altitude, and the runoff estimates were consistent with measured runoff from nearby watersheds. A point estimate of runoff was allowed to equal mean runoff in a nearby watershed, or to be somewhat higher (or lower) if a compensating departure from mean watershed runoff could be inferred in distant parts of the watershed on the basis of altitude or regional trends. Then, precipitation contours were drawn to parallel runoff contours but differ from them by the magnitude of nearby estimates of evapotranspiration. These maps may slightly underrepresent mean precipitation and evapotranspiration in areas of high relief, because most precipitation stations in such areas are in valleys. Map accuracy is evaluated.
The maps and text are designed to be printed as 34x53 inch plates; they may not be legible if printed in their entirety at appreciably smaller scales. The Arc/Info coverages from which these maps were prepared are available at the Water Resources National Spatial Data Infrastructure Node: ofr96395_eva, ofr96395_pre, and ofr96395_run (evapotranspiration, precipitation, and runoff).
Descriptors: *Annual Runoff, *Areal precipitation, *Runoff, *Evapotranspiration Precipitation, Rainfall, New York, New England, Northeast