_Effect of the Floods in the Santa Catarina River._--The area of the water-shed of the Santa Catarina River above Monterrey is about 1,410 sq. km. (544 sq. miles), and its area at San Geronimo, owing to its configuration, is practically the same. Its general character has already been referred to. On the night of August 10th and early on the morning of August 11th, a big flood came down the river, flowing at its maximum about 1,130 cu. m. (40,000 cu. ft.) per sec., due to the heavy rainfall (Fig. 4). This flood carried away all the temporary staging around the shafts, seriously wrecking the temporary pumping station, as well as destroying the 30-cm. cast-iron pipe, notwithstanding the fact that it had been encased in a block of concrete 3 m. wide and 1-1/2 m. thick right across the river; but no damage was done to the infiltration gallery or to the shafts in the river channel. The effect of the flood on this pipe is shown by Fig. 2, Plate XXXI. [Illustration: PLATE XXXI, FIG. 2.--PROFILE SKETCH, LOOKING UP STREAM ON LINE OF 24-INCH MAIN SUPPLY PIPE.] Following this flood, which had caused the loss of 14 lives in the city, 3 miles below San Geronimo, there was practically no rain for 13 days. Then, on August 25th the second heavy precipitation began and continued until August 29th, the details being shown on Fig. 4. This precipitation, therefore, fell on a water-shed which was completely saturated, as it had already absorbed a large proportion of the 13.38 in. of rain which fell during August 10th and 11th; and at every point along the river, prior to August 25th, springs were issuing forth, and there had been very little evaporation during the intervening dry spell. The writer has calculated that at Monterrey this flood reached the enormous quantity of 6,650 cu. m. (235,000 cu. ft.) per sec., a rate equal to 432 cu. ft. per sec. per sq. mile of water-shed.[6] The effect of this flood was to demolish completely about 1,200 "sillar" houses (without taking into consideration the numerous wooden houses) at Monterrey, and to cause a fearful loss of life, variously estimated between 3,000 and 5,000 persons; the lower figure the writer believes is approximately correct. At San Geronimo the original pumping station was carried away entirely, leaving practically no trace whatever. [6] The writer, in a brief article contributed to _Engineering News_ soon after the flood (September 23d, 1909), gave this figure as 271,500, or approximately equal to a run-off of 500 cu. ft. per sec. per sq. mile; but, from a later and more complete study of the conditions for many miles above Monterrey, he believes the above quantity to be approximately correct.