=169. Run-off of Croton Watershed.=—The total area of the Croton watershed, from which New York City draws its supply, i.e., the area up-stream from the new Croton Dam, is 360.4 square miles, of which 16.1 square miles, or 4.47 per cent, of its total area is water surface. Mr. John R. Freeman found in the investigations covered by his report to the comptroller of the city of New York in 1900 that the average annual rainfall on that area for the thirty-two years beginning 1868 and ending 1899 was 48.07 inches, and that the average run-off for the same period was 47.7 per cent of the total average rainfall, equivalent to a depth of 22.93 inches. [Illustration: Aqueducts near Jerome Park Reservoir, New York City.] Table IX gives the main elements of the rainfall and run-off for the Croton watershed during the thirty-two year period, for the averages just given. TABLE IX. RAINFALL ON CROTON WATERSHED IN TOTAL INCHES—1868-1898. NATURAL FLOW OF CROTON RIVER AT OLD CROTON DAM, IN EQUIVALENT INCHES. PERCENTAGE OF RUN-OFF TO RAINFALL FOR EACH YEAR. -----------+---------+---------+----------- Year. | Total | Total | |Rainfall.| Run-off.| Per Cent. -----------+---------+---------+----------- 1868 | 50.33 | 33.33 | 66.22 1869 | 48.36 | 23.61 | 48.82 1870 | 44.63 | 19.20 | 43.02 1871 | 48.94 | 19.46 | 39.76 1872 | 40.74 | 16.92 | 41.53 1873 | 43.87 | 25.02 | 57.03 1874 | 42.37 | 25.10 | 59.24 1875 | 43.66 | 24.77 | 56.73 1876 | 40.68 | 21.09 | 51.84 1877 | 48.23 | 20.22 | 41.92 1878 | 55.70 | 27.17 | 48.78 1879 | 47.04 | 19.65 | 41.77 1880 | 36.92 | 12.63 | 34.21 1881 | 46.69 | 19.25 | 41.23 1882 | 52.35 | 24.28 | 46.38 1883 | 42.70 | 13.33 | 31.22 1884 | 51.28 | 24.08 | 46.96 1885 | 43.67 | 17.71 | 40.55 1886 | 47.74 | 20.10 | 42.10 1887 | 57.29 | 26.61 | 46.45 1888 | 60.69 | 35.27 | 58.12 1889 | 55.70 | 31.39 | 56.36 1890 | 54.05 | 25.95 | 48.01 1891 | 47.20 | 23.48 | 49.75 1892 | 44.28 | 17.68 | 39.93 1893 | 54.87 | 29.05 | 52.94 1894 | 47.33 | 20.56 | 43.44 1895 | 40.58 | 15.95 | 39.31 1896 | 45.85 | 23.26 | 50.73 1897 | 53.12 | 25.59 | 48.17 1898 | 57.40 | 29.72 | 51.77 1899 | 44.67 | 22.28 | 49.88 Average for| 48.07 | 22.93 | 47.70 32 years. | | | -----------+---------+---------+-----------