Abstract
The run-off which appears in the upper Rio Grande is almost wholly derived from the melting of snow that falls on the elevated parts of the drainage basin in Colorado and New Mexico. Statistics are presented showing the mean monthly and annual snowfall as derived from an average of 10 stations in Colorado and 12 in New Mexico for the period of years, 1909–1922. The measured discharge of the Rio Grande, near Buckman, N. Mex., as determined by the United States Geological Survey is also given for the corresponding period and for earlier years.
The average annual snowfall. is 97 inches. Assuming that the equivalent of the snow was 0.08 inch of water per inch of snow, and assuming further that there was no loss by diversion or otherwise and that but 29 per cent of the precipitation was measured as run-off, that amount of snowfall would correspond to 1,332,000 acre-feet for the area above Buckman, N. Mex. This amount corresponds very closely with the average run-off for the entire term of years but is somewhat below the average for the 13 years, 1909–1922. The uncertain factors in the above approximation are the water content of the snow, diversion, and other losses which can not easily be approximated.
