Great Lakes hydrology by months, 1946-1946

Monthly estimates of precipitation on each lake, evaporation from each lake surface, and runoff into each lake from surrounding land areas are developed for the Great Lakes for calendar years 1946 through 1965. Overlake precipitation is estimated by extrapolation of the land isohyetal patterns multiplied by lake-land ratios as established from island-shore stations. Evaporation by months is calculated using the mass transfer method. An isopleth mapping technique is used to estimate the runoff. The net basin supply for a lake is equal to the total runoff plus the precipitation on the lake surface minus the evaporation from the lake surface. The monthly and annual net basin supplies for each lake are determined from the estimated values of runoff, precipitation, and evaporation and are compared with the monthly and annual net basin supplies as reported by the U.S. Army Corps of Engineers. The estimated 20 year mean annual net basin supply for all lakes is about 6 per cent less than the value reported by the U.S. Army Corps of Engineers.U.S. Department of the InteriorU.S. Geological SurveyOpe