LO CO o \ DIVERSITY - Rainfall in MEXICO Romulo Escobar Ex-Chief of the Depart- ment of Agriculture and Forestry Mexican national Commission Universal Exposition, St. Louis, J904 >. Rainfall in MEXICO Romwlo Escobar Ex-Chief of the Depart- ment of Agriculture and Forestry Mexican national Commission Universal Exposition, St. Louis, J904 The Whitc-Erans- f enfold Company In Buffalo, New York RAINFALL IN MEXICO HEN one has the opportunity of hear- ing the general opinion of Mexican farmers relative to the system of our rainfall, the uniformity of such opinion is somewhat astonishing, inasmuch as they all claim an unfavorable change, more and more noticeable every year, in said system, not only because of the terrible decrease of the annual preci- pitation, but also of the retardation and growing irregularity of the rainy season. It will not be necessary to travel extensively over the Republic to be convinced that the above mentioned belief is as general over the frontier states as it is in those of the southern portions of the country. I have been fully convinced of the generality of such belief by means of certain interrogatories relating to the groups I have under my charge as member of the Mexican Commission to the Saint Louis World's Fair, as one of the questions put in said interrogatories, relating to the local difficulties hampering the progress of agriculture, has been answered from all parts of the Republic, stating that one of the principal difficulties is the scarcity and irregularity of rainfall, which is more and more marked every year. And this opinion prevails not only in the Republic ; an agent of the Department of Agricul- ture of the United States predicted for us, a few RAINFALL IN MEXICO years ago, a complete ruin on account of the de- crease of our rainfall, and, Doctor Moises S. Bertoni, Director of the School of Agriculture, at Asuncion, Paraguay, in speaking of rainfall in Mexico, he states that he has been able to discover a decrease, similar to the one we have suffered, over the basin of the Paraguay River, and he affirms that the same thing has happened in Argentine, Brazil, and in general, all over Latin America. As the conclusions I may arrive at in the course of this study might be influenced, contrary to my desire, by the prejudices I may have before going into the matter, I must confess that I have never been of the opinion that the decrease of our rainfall has been so remarkable and general as it is claimed, because, in the absence of data secured by pluviometric observations, which would be the only reliable foundation we could find, I have been un- able to observe so marked a change as is generally admitted. I have noticed very brusque changes indeed, series of years of real drouth, but the same have never been permanent. I have seen that many lakes situated along the sides of the various railway lines I have been over during many years, such as the lakes Encinillas and Patos, a short distance from the line of the Mexican Central Railway, built in 1 88 1 , have for many years occupied a greatly reduced surface, and that the last mentioned lake has in some instances disappeared completely ; but at other RAINFALL IN MEXICO times I have seen both lakes with as much water as they ever had since the first time I saw them. Lake Patos, for instance, only a few years ago, reached a maximum capacity never before recorded even by the oldest inhabitants of the adjacent dis- tricts. I have been unable to notice any visible change in many of the streams I have known from childhood; I have heard, however, of rivers which have entirely disappeared, but on the other hand, I have seen new ones come into existence, and when- ever the former occurrence has happened, the same has been the result of the felling of forests located in the upper hydrographical slopes, or because a current of extraordinary force has swept away from creeks and ravines their alluvial deposits, thus diminishing their means to arrest the flow of rain water, which in former times used to settle in their basins, and facilitating the drainage of the same. The belief that the railways have been instru- mental in bringing about the decrease of rainfall, not because of the forests destroyed on their ac- count, but due to the strange relations attributed to them, probably because their construction coincided with a period of decrease in our annual precipita- tion, has always appeared to me as unfounded, and the only reason why I mention it is because of its universality, though I consider the same unworthy of comment The belief which attributes such marked changes to the felling of forests does not appeal to RAINFALL IN MEXICO me as unreasonable, but I do think that its influ- ence has been somewhat exaggerated, since I have heard such complaints not only in places where forests have been destroyed, but also in settlements far away from any line of communication that could cause an extensive felling of the forests, and because I have noticed that said changes are claimed in communities whose dominating winds during the rainy season do not come from the quadrant where the forests have been felled, and, even admitting that the above influence could be of a more local character than what would be proper to believe, it has been demonstrated that the effect claimed is caused by an extensive felling of the forests in the direction towards which the dominating winds will blow. The opinion of the Baron of Humboldt and of the wise Agriculturist Boussignault, the distinguished travelers who visited and studied our country, can- not be disputed, as it is an established fact that the extensive destruction of the forests brings about the most lamentable results, especially so in regard to the life of spring waters in the lowlands, but I do believe that the above opinion has been accepted with increased significence as a basis to prove the decrease of our rainfall. I am of the opinion, besides, that the question of rainfall, like many others, has been made the subject of superstition. Persons of superstitious in- clinations always remember the times when their RAINFALL IN MEXICO omens have turned into reality, but they forget the many instances when they have erred. Such is the case with us, we keep fresh in our memory the years of heavier rains we have seen from childhood and in speaking of them in times of drouth we will surely come to the conclusion that our supply of rainfall has decreased. Ever since I have been able to remember, I have heard people complain of the want of rain and often have heard the statement : "This is the worst drouth we have ever experienced." On the other hand, I have never heard any comment at all in normal or good years ; it seems as if the latter, being considered exceptional, does not de- serve any mention. As persons of an advanced age unanimously confirm this fact, I have been led to believe that the change in our system of rainfall would ap- pear more marked if a long period of time would be subjected to comparison, instead of considering only the last third part of the nineteenth century. The opening of new waterworks, canals, etc., are a more frequent cause than in the past for the exhaustion of rivers and rivulets ; they hamper the facilities for irrigating the lower lands, and people who notice the decrease in the volume of water of a river, which never may have been known to become dry, or those who experience the loss of crops where they have been abundant in the past, without know- ing or even considering the direct cause of such phenomena, are prone to declare that never before RAINFALL IN MEXICO have they seen such scarcity of water, and thus, the above mentioned idea assumes the proportions of a general belief. I have gone as far as to imagine that said belief might in some way effect the question of laborers for agricultural purposes. Il is a known fact that laborers are getting to be more and more scarce every day in the farming industries, not only on account of the reconcentration of the rural popu- lation in the cities and towns, but also on account of an increase of the other classes of work, develop- ing even in the farming districts. There are many at present which have been completely abandoned, owing to the fact that many enterprises of a paying character in the past would be a dead loss at pres- ent ; and because the construction of new railway lines, modern factories and the operation of new mines, take a large number of laborers away from agricultural pursuits. Farmers who generally culti- vate an extensive system of lands, are at present unable to secure the number of laborers they could find in former times, they, however, insist upon planting the same area of land and even clear new plots, which they are incapable of treating as often and cultivating under the laborious rules of agricul- ture practiced fifteen or twenty years ago. More- over, experience has demonstrated beyond doubt that cultivation means economy of water, that a deep preparation of the soil before planting or the treat- ing of a field after irrigation or rain have taken RAINFALL IN MEXICO place, enables the soil to absorb a greater amount of water and to maintain the moisture it may have for a longer period of time. There is enough truth in the above to authorize the statement that the culti- vation of the soil is equivalent to its irrigation. If the work of cultivating the soil is attended with many difficulties, if the same is effected in a defici- ent manner, the results are bound to be equal to those experienced on account of " the scarcity of water. May we not presume that the labor question, owing to the conditions mentioned, is to a certain extent responsible for the belief that our system of rainfall has enormously decreased ? Laboring under these ideas I have commenced my study, drafting diagrams showing the precipita- tion in each of the places where there is a meteoro- logical observatory, and from which I have been able to secure the data corresponding to a period of not less than six years, such being the minimum time I have adopted to consider the changes that may have occurred in their system of rainfall. For localities which have furnished me with a statement of their monthly precipitation, I have drawn annual curves to the end of discovering whether there has been any delay or increase in the irregularity of their rainfall. These diagrams have been drawn by tak- ing a line to represent the average annual precipita- tion admitted by me, in a period subsequent to 1877, and marking on said line the abscissas representing RAINFALL IN MEXICO the periods of time, the years and months, I have drawn those which appear above or below the line, as the case may be, to show the increase or decrease over or below the normal precipitation of each year. I will treat the diagram of each locality sepa- rately, and I will afterwards make an abstract or recapitulation to enable me to establish deductions of a general character, in connection with which I will endeavor to set aside my personal views in the matter, bearing only upon the results shown by the recapitulation. It is to be regretted that we have not a more extensive meteorological system, and that there are but limited observations, prior to 1877 ; but in spite of this fact, these studies must be carried forward with the idea that, though the data at our disposal are insufficient, and that we are in danger of erring in our deductions, and even though we may leave many blank spaces in our work, since it is impossible to do everything at one time, we will, however, accomplish one material advantage, /. e., the work of compilation. Many indeed have been the hardships attend- ing the work of collecting what few data I have slowly gathered, though I have been honored with the kind co-operation of some disinterested man- agers of observatories, whose names I will mention in each case and for which I feel sincerely thankful, and I trust that my present work will save this RAINFALL IN MEXICO troublesome task to those who, possessing more knowledge and better elements, may in the* future undertake a vaster study of a question which so deeply affects our country. I have no doubt that the conclusions arising from my study may be in conflict with the individual opinion of many others, since the former will refer to a matter where most people generally follow their own beliefs, it being impossible to destroy the value of the weak or strong arguments upon which they base the same ; however, I hold that no argument can logically give better support to my deductions than the proofs rendered by pluviometric records, therefore, I shall use the latter for my guidance. Moreover, the fact of the meteorological observa- tories being located in populated centers, will natu- rally show greater changes than those claimed in the rural districts, provided we admit as true that the felling of the forests has had so great influences in the matter as are attributed to it, it being proper to assume that all the observatories we have are situ- ated in the heart of districts where the destruction of the forests has been more extensive. Being convinced of the advantages gained by making a separate study of the changes of the pre- cipitation of rainfall in the different zones of the Republic, as the number of observatories are limited and the same are irregularly distributed over the nation's territory, I have preferred to study the pre- cipitation in the same order in which I made out the R A I N F A LL IN MEXICO diagrams without considering the geographical loca- tion of the observatories. When mentioning the data furnished by each observatory, I will refer, by way of information, to several other data taken principally from an article published by Engineer Guillermo B. y Puga, and from a book called " Geographical and Statistical Notes on Mexico", written by Licentiate Matias Romero, in which book I have found many interest- ing data for this study. I have also compared many of the data mentioned herein with those contained in a small but important book called " El Clima de Mexico", written by Mr. Manuel Moreno y Anda (see enclosure No. i ). RAINFALL I N MEXICO Yuma, Arizona, U. S. of A. DATA Altitude above sea level 43 m. Average annual precipitation 78 mm. Number of years recorded 28 years Annual Precipitation (C. M. O.) Puga 1878 73-!+ 1879 83.6+ 1880 18.8 1881 24.9 1882 45.2 1883 59-7 1884 148.8+ 1885 69.1- 1886 135-9+ 1887 99.1+ 1888 74-9+ 1890 1891 67.8 1892 85-1+ 1893 85.6+ 1894 74-9+ 1895 33-8- 1896 64.8 1897 106.2+ 1898 58.7- 1899 15.2 1900 21.6 1889 119.1+ Accepted average annual precipitation 71 mm. i Number of years 22 The above data, though taken from observa- tions made abroad, are similar to the ones that could be obtained in the northwestern region of the State of Sonora and northeast of lower California. The smallness of the precipitation is remark- able. In none of our observatories have we re- corded such low precipitation. From 1880 to 1883, inclusive, the curve of pre- cipitation shows a decrease below the line represent- ing the average annual precipitation. After 1894 the curve comes down again and there is only one year, that of 1897, which shows an increase over the average precipitation. RAINFALL IN MEXICO El Paso, Texas, U. S. of A. DATA Altitude above sea level i2O5 m. Puga Average annual precipitation 334 mm. " Number of years 6 " Annual Precipitation (C. M. O.) 1879 168.4 1889 180.3 1880 365.0+ 1890 1881 461.5+ 1891 56.4 1882 2IO.I + 1892 135.1 1883 328.2+ 1893 276.3+ 1884 464.8+ 1894 107.7 1885 185.7 1895 259.1 + 1886 204.7 1896 248.7 + 188 7 248.7+ I8 97 315.2 + 1888 248.7+ 1898 156.5 1889 185.4 1900 201.9 Accepted average annual precipitation 234 mm. 8 Number of years 21 Rainfall at El Paso, Texas, recorded during this period of time, serves the purposes of this study as data relating to the northern portion of the State of Chihuahua owing to the proximity of the latter state to the boundary line. From 1885 to 1894 there are only two years over the average precipitation, 1888 and 1893. From 1895 there is a series of three years over the average precipitation, and from the latter date the curve shows a decrease covering the other three years. I have been unable to secure any later data to 1900, but I am of the opinion there must be an 16 RAINFALL IN MEXICO increase, as the last two years, especially the present one, have been favorable in this respect. The mere inspection of this diagram shows a decrease in the amount of annual rainfall. RAINFALL IN MEXICO Galveston, Texas, U. S. of A. DATA Altitude above sea level 12 m. Puga Average annual precipitation 1328 mm. " Number of years 13 " Annual Precipitation (C. M. O.) 1878 1546.9+ 1889 953-0 1879 683.3 l8 9 1880 1294.6+ 1891 1054.3 1881 1353.3+ l8 9 2 629.4 1882 1465.1+ 1893 899.9 1883 790.2 1894 1032.3 1884 1526.0+ 1895 988.3 1885 1589.0+ 1896 602.2 1886 977-9 1897 742.7 1887 1103.1 1898 1066.8 1888 1526.2+ 1899 1060.7 1900 17694+ Accepted average annual precipitation 1120 mm. 6 Number of years 22 Data relative to Galveston can be compared with those of several points of our Mexican gulf zone. From 1889 to 1899 the precipitation appears below the accepted average, and during that period there might be an increase only in 1890, for which year I could not secure any data. The inspection of this diagram shows a decrease in rainfall, though at the present time the same seems to be increasing. 18 RAINFALL I N MEXICO Zacatecas, Zacatecas, Mexico DATA Altitude above sea level Annual average precipitation Number of years considered Northern latitude Average barometric pressure Maximum temperature Minimum " Medium Prevailing direction of the clouds " " " " wind Number of years 2496 m. Puga 819 mm. " 10 " 22 46' Matias Romero 573 mm. 4 21 8' 6 i' I 3 2 ' S. E. " S. E. " " 10 " " Annual Precipitation (J. A y Bonilla and C. M. O.) 1874 900.0+ 1875 844.0+ 1876 687.0+ 1877 1878 560.0 1879 672.0+ 1880 690.0+ 1 88 1 700.0+ 1882 717.0+ 1883 825.0+ 1884 990.0+ 1885 981.0+ 1886 798.0+ 1887 978.0+ 412.0 226.0 1 888 1446.8+ 1889 562.9 1890 658.6+ 1891 1892 1893 I 63-o 1894 368.9 1895 271.8 1896 480.6 1897 784.9+ 1898 516.0 1899 409.0 1900 805.3+ 1901 45 2 -9 Accepted average annual precipitation 652 mm. o Number of years 24 R A I N F ALL IN MEXICO The diagram for Zacatecas is one of the most interesting among all those I have prepared, because in the majority of the latter years of heavy rainfall alternate with those of low precipitation, thus caus- ing the curve to go up and down within short dis- tances, while in the former diagram a constant increase is shown since 1878 to 1888, the decrease from 1885 to 1887 being insignificant. From 1889 to 1897 there is a curve beneath the average line, this latter year being, among those of the above period, the only one showing a marked increase over the normal precipitation. After 1898 the diagram continues to show sev- eral irregularities similar to those of other localities. Reference to the diagram will show a decrease in rainfall, though, like Galveston, there is an appar- ent tendency to increase. The curves for monthly precipitation I have drawn for 1894 to 1901 demonstrate a marked irregularity, the year 1895 being remarkable owing to the low precipitation during the regular rainy season. RAINFALL IN MEXICO Guadalajara, Jalisco, Mexico DATA Altitude above sea level 1 566 m. Puga Average precipitation 864 mm. " Number of years 6 " Northern latitude 20 41' M. R. Average barometric pressure 636 mm. 2 4t Maximum temperature 35 5' " Minimum " 4 5' " Medium temperature 19 7' " Average annual precipitation 86 1 mm. 9 " Number of years 7 " Annual Precipitation (M. Nito C. M. O. and Belem Hospital) As in the data secured from Guadalajara there are several differences, I have in some cases taken the averages between the data furnished by the Director of the Guadalajara Observatory and those secured from the C. M. O., relating to the latter as well as to the Betem Hospital Observatory, 1 8 7 4 900.0 1888 991.0 1875 844.0- 1889 792.0 pr. 2- 1876 687.0 1890 1076.9 " 3- 1877 830.0 1891 1087.1 " 3 1878 1083.0 1892 789.7 2- 1879 670.0 1893 728,9 2- 1880 1092.0 1894 2003.8 " 2 1881 1032.8 per 2 1895 2488.6 " 2 1882 828.0 " " 1896 1426.7 " 2 1883 719.2 - 1897 1340.7 " 3 R A I N F A L L IN MEXICO 1884 605.4 1885 "43-+ 1886 853.9 1887 1013.4 1898 1875.8 pr. 2+ 1899 J 432-3 " 2+ 1900 1901 1323.9+ Accepted average aunual precipitation 1134 mm. 5 Number of years 24 The most remarkable feature of the diagram corresponding to Guadalajara is, that prior to 1894 all years show a precipitation inferior to the normal average, with the exception of 1885, which .shows a slight increase, but after 1894 all years had more than the normal rainfall, a rather curious circum- stance, which would at least indicate an ameliora- tion in the system of rainfall in that city. The inspection of the diagram demonstrates an increase of rainfall. In the curves for monthly precipitation I have made up with data relating to years subsequent to 1889, furnished by Mr. Mariano Nieto of the State Observatory, It may be seen that the curve begins to rise in every case either in May or June, that is to say, that the rainy season begins at such time. It also shows that the rainy season is well defined. As the curve will not come down again until one of the last three months of the year, generally October, and that the month of April is one of the dryest months all through, as it only had a precipitation worthy of note, /. e., 125 mm., in 1896, the same being either nothing at all or very insignificant in all other years. RAINFALL IN MEXICO Saltillo, Coahuila, Mexico DATA Altitude above sea level 1632 m. Puga Average annual precipitation 554 mm. " Number of years 3 Northern latitude 25 25' M. R- Medium pressure 632 mm I " Maximum temperature 34 o' " Minimum 2 8' Medium 16 8' Average annual precipitation 527.3 " Number of years 4 ** Annual Precipitation (M. Kubicza, Manager of the Observatory of the College of San Juan Nepomuceno) 1885 506.5 1-894 815.5+ 1886 493.6 1895 596.0+ 1887 674.4+ 1896 713-+ 1888 639.9+ 1897 34*3-0 1889 776.0+ 1898 405.0 1890 585.6+ 1899 553-8+ 1891 3 I 3- I 9 74L5+ 1892 777-9+ J 90! 164,3 1893 37-4 Accepted average annual precipitation 553 mm. 3 Number of years 17 The only thing worthy of note that I find in Saltillo's diagram is the uniform increase of annual precipitation since 1897 until 1900, and the consid- erable decrease, which is the lowest one in the 23 RAINFALL IN MEXICO period of time registered, corresponding to 1901. On the other hand, the irregularities shown in the diagram are in proportion to the precipitation and are not so remarkable as those in other observa- tories. The inspection of the diagram does not seem to demonstrate either an increase or a decrease, although the last year shows a marked decrease of rainfall. The curves for monthly precipitation show the following features : Great irregularity between one year and the others ; the unsettled and variable character of the rainy season ; the irregularity of precipitation in the months of July and August, in which the amount of rainfall has been sometimes very heavy, and rather insignificant in other years. If a curve be drawn to represent the normal year to compare the same by superposition with that of every year,, very remarkable differences would be found in every one of the years registered. RAINFALL IN MEXICO Leon, Guanajuato, Mexico DATA Altitude above sea level 1798111. Leal Puga Average annual precipitation 728 mm. " " Number of years lo " ' Northern latitude 21 f M. R. Medium barometric pressure 617.4 Maximum temperature 36 6' Minimum " 1 i' Medium " 18 9' Prevailing direction of the clouds S. W. " winds N. N. W. Average annual precipitation 729.8 Number of years 14 Annual Precipitation and Number of Rainy Days (Mariano Leal) i8 7 8 601.5 92 1890 867.2+145+ 1879 709.2+100 1891 429.8 116 1880 825.4+119+ 1892 473.2129+ 1881 629.9127 + i893 648.5+109 1882 699-3+ ii 7 1894 552.7125+ 1883 900.9+134+ 1895 531.3 113 1884 613.1 in 1896 314.6117 1885 7 86.2+'i3+ 1897 571.7 118 normal 1886 725.9+ 97 1898 747.6+102. 1887 781 8+136+ 1899 510.3 1 08 1888 869.6+152+ 1900 560.6127+ 1889 767-5+ ! 34+ 1901 439-5 94 Accepted average annual precipitation 648 mm. 2 Average number of rainy days per annum 1 18 Number of years 24 25 R A 1 N F A L L IN MEXICO The diagram showing Leon's annual precipita- tion has the following notable features worthy of mention: First. A series of successive years above the aveiage precipitation, running from 1885 to 1890, inclusive. Second. That in years prior to 1890 the majority of years recorded are above the normal line, there being only three with a lower pre- cipitation, i. e., 1878, 1881 and 1884, while after the above mentioned year (1890) almost all have had a very limited precipitation, as there is only one year with normal precipitation, 1893, and another one with a higher precipitation, 1898. The mere inspection of this diagram demon- strates a decrease of rainfall, and the part corre- sponding to the later years is also descending, which fact does not occur with other diagrams I have studied. I believe the latter diagram can be mentioned as the one which better characterizes a period of drouth shown in the last decade of several other observatories, whose data I have studied and will mention hereinafter. In reference to the above observatory, which is one of the most important in the country, from an agricultural point of view, the data relating to the same having been furnished me by its manager, I have made up a diagram showing the number of rainy days it had since 1878, and I note that the line follows a regular course, to a certain extent, in accord with the line of precipitation in the majority RAINFALL IN MEXICO of years, although the same thing does not occur in others, such as 1881, 1893, 1894, 1896, 1898, and 1899. The curves of monthly precipitation do not appear so irregular as they do in other observa- tories, but they are, however, more irregular than those for Toluca, Mexico, and Puebla. The period of rainfall represented by those curves demonstrates but few interruptions and no delay whatever in the rainy season, as it is generally seen that the curve begins to rise in the months of May or June. In order to discover what other peculiarities or changes there may be, in the latter as well as in other diagrams, without my referring to the same, it would be necessary to make a more laborious and detailed study than the one afforded by the circum- stances and the purpose of the present work. RAINFALL IN MEXICO Toluca, Mexico DATA Altitude above sea level 2625 m. Puga Average annual pecipitation 678 mm. " Number of years 2 " Northern latitude 19 1 7' M. R, Average barometric pressure, 1896 556 mm 6 " Maximum temperature " 28 7' " Minimum " " 3 8' " Medium " 13 8' " Prevailing direction of the clouds, 1896 N. E. " winds W. and W. S. W. Annual Precipitation and Number of Rainy Days (C. M. O. & E. Schulz) As in some cases the data I have secured do not agree, 1 have noted the averages : 1883 729-9-1- 1884 563.1 1892 662.9 average of 2 131 1893 843.7 + 160+ 1894 572.8 123 1895 660.3 average of 2 154+ 1896 618.8 146 1897 549.6 123 1898 778.5 average of 2+188+ 1899 715.1 " 24-161 + 1900 733-7 +146 1901 628.2 * 143 Accepted average annual precipitation 676 mm. 6 Average number of rainy days 147^-10 years Number of years 1 2 28 RAINFALL IN MEXICO The data secured are insufficient to show, by the mere inspection of the diagram, any change in system of rainfall of this locality. The line shows a decrease in the last years. The course of the line relating to rainy days is almpst always in accord with the annual precipitation. The curves relating to monthly precipitation show a relative regularity during the rainy season. RAINFALL IN MEXICO Mexico, Federal District DATA Altitude above sea level 2282 m. C. M. O. Average annual precepitation 582 mm. " Number of years 20 " Northern latitude 19 26' M. R. Medium barometric pressure 586 mm. 4 " Maximum temperature 31 6' " Minimum " i 7' Medium 15 4' Prevailing direction of the clouds S. W. " wind N. W. Number of years 15 " Annual Precipitation (C. M. O.) Era Prior to 1877 1841 451-7 1869 718-3+ 1842 541.3 r8 ;o 695.0+ 1843 659.6 1871 746.4+ 1844 549-0 1872 758-7+ 1845 677.0+ 1873 596-2 1865 1011.0+ 1874 737.! + 1866 568.1 1875 669.1 1868 692.1 + Average annual precipitation for era prior to 1877 671 mm. 3 Number of years 1 5 Era Subsequent to 1877 1877 404.0 1889 408.1 1878 892.6+ 1890 638.1 + 1879 477-2 1891 658.3 RAINFALL IN MEXICO 1880 552.2 1892 444.2 1 88 1 505.2 1893 5 68 - 6 1882 66i.o-|- 1894 331.8 1883 608.7+ 1895 559- 1 1884 468.5 1896 452.0 1885 675.8+ 1897 652.1 + 1886 531.2 1898 593.7+ 1887 812.7+ 1899 581.1 + 1888 739-9+ 19 535-9 1901 527.1 Accepted annual precipitation for pre- vious era 571 mm. I Number of years 25 Average annual precipitation calculated by all data on hand 608.7 Number of years 40 The diagram for the City of Mexico, corre- sponding to last twenty-five years, is not of the kind which clearly demonstrates a decrease in rainfall by simply glancing over the design. The rising and falling portions of the line alter- nate at short intervals. The diagram, however, shows, like others I have prepared, a period of drouth or decrease of the curve in the form of a swing, in connection with the last part of the period registered. It is remark- able to see how the line in the last four years shows an uninterrupted decrease. But the study of the numerical data I have referred to above, is more forcible, to my regret, than the material inspection of the diagram. In fact, the average for the era prior to 1877 is greater than the total average, and the former and the latter RAINFALL IN MEXICO are greater than the average for the era subsequent to 1877, an d> this being one of the localities where the largest number of data can be obtained, I feel authorized to accept the statement that rainfall has decreased at the Capitol of the Republic. The curves relating to monthly precipitation cannot be considered very irregular, but I do be- lieve that remark should be made that during all the second part of the period recorded, that is, dur- ing the last twelve or thirteen years, we have not had in the City of Mexico such heavy rainfalls as those of the months of July and August of 1878, September 1880 and 1886, and July of 1887, RAINFALL IN MEXICO Puebla, Puebla, Mexico. DATA Altitude above sea level 2167 m. Puga Average annual precipitation 1185 mm. " Number of years 10 " Northern latitude 19 03' M. R. Average barometric pressure 593 mm. 2 " Maximum temperature 31 9' " Minimum " i i' " Medium " 15 7' " Prevailing direction of the clouds E. N. E. " " " wind N. E. Average annual precipitation 926.0 " Number of years 14 " Annual Precipitation ( F. de P. Servin " State College", and G. Carrasco of the " Catholic College") As there are two observatories in Puebla fur- nishing me with data, I have decided to prepare and study two separate diagrams relative to the same city, though I did not do likewise in regard to Guadalajara, in order to have an idea of the varia- tions that may occur through observations made within short distances, and I have been really sur- prised at the differences discovered. I was well aware of the fact that different precipitation may be recorded in two separate wards of the same city, but when comparing the annual data I did not expect that such marked differences would ever appear as 33 RAINFALL I N MEXICO those shown by the data mentioned hereinafter, or as may be seen from the diagrams I have prepared. As I have noticed some differences between the data furnished me by the C. M. O. relating to the " Catholic College" at Puebla, and those pro- vided by the manager of the latter observatory, I have caused the averages to appear. State College 1878 IM7-5+ 1891 1025.3+ 1879 846.3 1892 824.2 1880 977-7+ 1893 1273.8+ 1881 912.2+ 1894 719.7 1882 930.2+ 1895 603.7 1883 974-1 + 1896 686.1 1884 673-9 1897 827.9 1885 973- 2 + 1898 938.8+ 1886 750-4 1899 787.0 1887 1193.2+ 1900 763-7 1888 984-3+ 1901 737-3 1889 790.7 1890 853-5- Accepted average annual precipitation 881 mm .8 Number of years 24 Catholic College 1877 925.7 average 1891 1002.4 average 1878 1281.9 " + 1892 983-9 1879 1016.4 " 1893 1867.5- 1880 1568.5+ 1894 757-4 1881 932.0+ 1895 644.8 1882 1205.1 average+ 1896 688.5 1883 1498.7+ 1897 973-0 1884 1105.7 1898 963-0 34 RAINFALL IN MEXICO 1885 1582.24- 1899 900.8 average 1886 902.7 1900 869.3 1887 1848.5 average-)- 1901 759-7 1888 2263.4 " -f- 1889 1070.8 1890 680.8 average Accepted average annual precipitation 1131 mm. i Number of years 25 The diagram prepared with the data furnished by the " Catholic College" is by far the most irreg- ular as compared with the one made with data from the " State College", but the following may be found in both of them : That the curve falls twice in the form of a swing during the second half of the period recorded, and that the line of the diagram continues to fall without interruption during the last four or five years. The curves relating to monthly precipitation are a great deal more irregular in the " Catholic College" than they are in the "State College", though a general agreement is observed between them. 35 RAINFALL IN MEXICO Pachuca, Hidalgo, Mexico DATA Average anuaal precipitation 242 mm. Puga Number of years 2 Altitude above sea level 2460111 M. R. Northern latitude 20 07' " Barometric pressure 574 mm - 8 Maximum temperature 27 2' Minimum " 0.6' Medium " 13 7' Prevailing direction of the clouds S. W. " wind N. E. Number of years i Annual Precipitation (A. Romero and Y. M. Cobos) 1893 475-4 1898 2952.4+ 1894 146.5 1899 2504.3+ 1895 327.2 1900 1060.4 1896 226.5 I 9 l 2006.0+ 1897 2749.0+ Accepted average annual precipitation 1383.0 Number of years 9 The diagram relating to Pachuca is the most irregular of all those I have prepared, and the dis- crepency from one year to the other, in regard to precipitation, is so great that one feels inclined to doubt the veracity of the above data, but fortunately, I sucured my information directly from the manager of the observatory at Pachuca, who was so kind as to furnish the same, and, besides, the said data agree with those provided by Mexico's Central Meteorological Observatory. 36 RAINFALL IN MEXICO The curves relating to monthly precipitation are equally irregular from one year to the other, as may be understood from the fact that the months of maximum precipitation which were recorded in each year were : 1893 . J une 177-3 1894 April 37,1 1895 October 76.6 1896 September 9.7 1897 July 716.0 1898 September 737-7 1899 June 721,2 1900 December 679.3 1901 September 870.0 The above is really surprising since it is not observed in any other part of the Republic from where meteorological data can be obtained. The above is sufficient in itself to form an opinion in regard to the astonishing irregularity of Pachuca's system of rainfall, which could perhaps be explained by being acquainted with the location of the city and the orographic development of the adjoining region, or through other causes which serve to establish the character of the climate. Even in other data I have been able to obtain there is something abnormal ; for instance, it ap- pears that the prevailing direction of the clouds in one year was towards the southwest, while the pre- vailing direction of the wind in the same year was towards the northeast, that is, in an entirely opposite direction. 37 RAINFALL IN MEXICO Colima, Colima, Mexico DATA Altitude above sea level 507 m. Puga Medium annual precipitation IO 53 mm - " Number of years 12 " Northern latitude 19 n' M. R. Barometric pressure 718 mm. 3 " Maximum temperature 37 2' ** Minimum M 9 4' Medium " 24 8' Prevailing direction of the clouds S. W. " " " wind S. W. Number of years i Annual Precipitation (F. Castrejon. Observatory of the Coliraa Seminary and C. M. O.) 1877 755-4 1892 892.6 1878 1416.5+ 1896 749.4 1879 1049.9+ 1897 898.7 1880 960.4 1898 1038.8+ 1891 1223.0+ 1899 1207.0+ 1901 859.1 Accepted average annual precipitation 1004 mm. 6 Number of years x , As there are many years missing in this series, it is impossible to point out any special feature of the diagram. RAINFALL IN MEXICO Mazatlan, Sinaloa, Mexico DATA Altitude above sea level 76 m. Puga Average annual precipitation 798 mm, " Number of years 20 " Northern latitude 24 n' M. R. Average barometric pressure 759 mm. 3 " Maximum temperature 34 i' " Minimum " 10 3' " Medium " 25 2' Prevailing direction of the clouds N. W. " wind N. W. Average annual precipitation S 1 9- 2 " Number of years 4 ** Annual Precipitation and Number of Rainy Days (N. Gonzales) 1880 948,6+79 + 1891 390-967 1881 1454,2+99 + 1892 326.160 1882 425.692 + 1893 777-474 1-883 748.683 -f 1894 56a2 62 1884 1122.6+102+ 1895 1088.5+75 equal 1885 1117.5+91 + 1896 594.2 70 *886 799-574 l8 97 695.367 1887 1206.4+91 + 1898 663.5 6 3 1888 676.176 + 1899 852,1+54 1*89 834,4+77 + 1900 812.6+59^- 1890 685.873 1901 948.5+71 Accepted average annual precipitattion ^05 mm. 8 Average number of rainy days 7j 39 RAINFALL IN MEXICO The diagram showing Mazatlan's annual rain- fall offers many irregularities, and the same demon- strates a decrease, followed by a rise in the curve, such as has been noticed in other cities, commenc- ing in the present case in 1887 and reaching its maximum elevation in 1895, dropping once more during the following year and again rising with slight alternate interruptions during the last five years. The curves relating to monthly precipitation show greater irregularities than those for other cities of the Republic, such as Mexico, Toluca, and Puebla, and the same are more remarkable because there are slight interruptions during the rainy season ; that is to say, that the curve rises and falls uniformly without projecting in or out. The great- est irregularities consist in the discrepancies found between the months of heaviest rains in one year and those of the other, therefore, the curve ap- pears quite high in some years and very low in others. In regard to the diagram referring to rainy days of each year, it is worthy of note that prior to 1889 there is not a single year showing a marked decrease below the normal line, as only the year 1886 has one rainy day less, while after 1899 a11 the years are inferior, with the exception of 1895, which was equal to the normal average. The appearance of the diagram shows, in a general way, that rainfall has decreased. RAINFALL IN MEXICO Monterrey, Nuevo Leon, Mexico DATA Altitude above sea level 496 m. Puga Northern latitude , 25 40' M. R, Average barometric pressure 709 mm. I " Maximum temperature 33 2' " Minimum " li 7' " Medium " 21 o' " Prevailing direction of the wind S. E. " Number of years I *' Annual Precipitation (A. Carrillo) 1865 744-0 1893 I37.0 1885 427.0 1894 489-9+ 1886 417-5 1895 549-9+ 1887 449-0 1896 628.0+ 1888 341.3 1897 581.0+ 1889 283.2 1898 488.8+ 1890 338-6 1899 969-4+ 1891 264.2 1900 795-6+ 1892 1 86.6 1901 729.7+ Accepted average annual precipitation 475 mm. I Number of years 17 The diagram showing Monterey's annual rain- fall is remarkable because of its rises and falls, which follow a continuous course during long periods of time. No sudden changes are to be noticed, such as happen with diagrams of other RAINFALL IN MEXICO observatories. Another feature worthy of mention in this diagram is that it follows a course which differs from the others generally, at least in regard to years where pluviometric registers have been secured. Prior to 1883 a ^ tne years had a precip- itation below the normal figures, but the reverse happened after the above mentioned date. As may be seen the diagram demonstrates an increase in rainfall. It is to be regretted that only seventeen years of observation can be secured from this observatory, since the latter is so important, owing to its location and on account of the features shown by the dia- gram prepared for years recorded. The curves relating to monthly precipitation are interesting because of the irregularities they indicate, owing to a period of relative drouth which always interrupts the rainy season. Mention is equally made of the low precipita- tion had during the months of heavy rains corre- sponding to the first part of the period registered. The year 1888 is worthy of note, because what little rain it had was distributed over almost all the months of the year, November having been the month of heaviest rains, with a very limited precip- itation of 27 mm. 3. RAINFALL IN MEXICO Merida, Yucatan, Mexico DATA Altitude above sea level 9 m. Puga Average annual precipitation 830 mm. " Number of years 2 " Northern latitude 20 55' M. R. Average barometric pressure 760 mm. 5 " Maximum temperature 40 5' " Minimum " 12 i' " Medium " 25 8' " Prevailing direction of the clouds E. " wind N. E. " Number of years I (1896) Annual Precipitation and Number of Rainy Days (Estatistical Bulletin from Yucatan) 1875 913.0 1896 914.7+118+ 1890 864.0 1897 875-0+ 1891 911.0+ 1898 1139.9+124+ 1892 834.0 1899 1062.5+ 78 1893 560.0 1900 943-6+ 93 1894 957-2+ 94 1901 601.7 65 1895 744.0 97+ Accepted average annual precipitation 867 mm. 3 Average number of raing days in 7 years 95 Number of years 12 RAINFALL IN MEXICO Though there are but few years recorded, the diagram shows an annual increase of rainfall similar to the one registered in other observatories during the last four to eight years, preceded by a period of years generally poor representing in the curve the descending portion already mentioned in this study. The examination of the diagram will not demon- strate either an increase or a decrease in rainfall. As regards monthly precipitation, and the num- ber of rainy days of each year, for which I have pre- pared curves corresponding to the last seven years, there is but little to be said. RAINFALL IN MEXICO Tuxpam, Veracruz, Mexico DATA Average annual precipitation 1532 mm. Puga Number of years 5 " Northern latitude 20 59' M. R. Average barometric pressure 763 mm. " Average temperature 24 5' " Prevailing direction of the clouds N. W. " " " " wind W. " Average annual precipitation 1654 mm. 3 " Number of years 2 " Annual Precipitation (C. M. O.) 1879 1 59 2 -5+ l88 5 8 93- 1881 1505.5+ 1889 1716.1+ 1883 1589.0+ 1890 1199.1 1884 1109.3 l8 9 x J 839.0+ Accepted average annual precipitation 1430.4 Number of years 8 The only thing worthy of mention at Tuxpam is that it holds the third place among the list of towns in Mexico provided with a meteorological observatory, on account of its average annual pre- cipitation. 45 RAINFALL IN MEXICO Teziutlan, Puebla, Mexico DATA Altitude above sea level 1982 meters Puga Average annual precipitation 1531 mm. " Number of years 5 " Annual Precipitation (C. M. O.) 1878 1339.2 1882 1263.2 1879 1927.2+ 1884 1240.6 1881 1884.2+ 1888 2268.2+ Accepted average annual precipitation 1653.7 Number of years 6 Considering Teziutlan 's average annual precip- itation, it holds the first place among towns from which we have data covering six or more years. RAINFALL IN MEXICO Real del Monte, Hidalgo, Mexico DATA Annual Precipitation (C. M. O.) 1889 768.2+ 1895 621.1 1890 828.04- 1896 435.0 1891 1023.0+ 1897 779-9+ 1892 853.0+ 1898 9*7-9+ 1893 156.0 1899 689.0 1894 565-7 1900 955-0+ Accepted average annual precipitation 749 mm. 2 Number of years 12 The rise and fall of the curve is well defined in the diagram for Real del Monte, said curve com- mencing in 1891 and ending in 1898, and of which fact I have made several mentions in the course of this study, in reference to other observatories. 47 RAINFALL IN MEXICO Tacubaya, D. F. DATA Altitude above sea level 2323 m. Puga Average annual precipitation 683 mm. " Number of years 10 " Northern latitude 19 12' M. R. Average barometric pressure 583 mm. 6 " Maximum temperature 28 6' " Minimum " o 8' " Medium " 15 5' " Prevailing direction of the wind N. W. " Average annual precipitation 668 mm. i Number of years 9 Annual Precipitation ( M. Moreno y Anda ) 1884 492.6 1892 485.7 1885 679.6+ 1893 726.8+ 1886 582.9 1894 388.5 1887 846.5+ 1895 627.8 1888 632.2 1896 440.3 1889 713-2+ 1897 665.4+ 1890 792.5+ 1898 681.1 + 1891 883.0+ 1899 626.8 1900 668.8+ Accepted average annual precipitation 643 mm. i Number of years 17 The diagram relative to rainfall at Tacubaya demonstrates a decrease at first sight during the period registered, and as it is natural to suppose, 48 RAINFALL IN MEXICO it is quite similar to that of the City of Mexico, owing to the proximity of both observatories. We fail to discover between the two diagrams mentioned such marked differences as shown between diagrams prepared with the data secured from the " Catholic " and the " State Colleges " at Puebla. 49 RAINFALL I N MEXICO Pabellon, Aguascalientes, Mexico DATA Altitude above sea level Average annual precipitation Number of years Northern latitude Average barometric pressure Maximum temperature Minimum " Medium Prevailing direction of the clouds " " " wind Average annual precipitation Number of years S. 1924 m. Puga 506 mm. " 19 22 04' M. R 607 mm. 8 " 24 o' 12 2' " 18 2' S. E. W. S. W. 537 mm. o 10 Annual Precipitation (C. M. O.) 1877 337-4 1878 467.1 1879 434-4 1880 697.4+ 1881 602. i + 1882 444.2 1883 605.5+ 1884 262.1 1885 648.5+ 1886 539.2+ 1887 669.1 + 1888 758.9+ 1889 566.6+ 1890 344-0 Accepted average annual precipitation 5 2 9-7 Number of years 14 The above diagram shows an increase of rain- fall during the period recorded, although on a very limited scale. RAINFALL IN MEXICO Huejutla, Hidalgo, Mexico DATA Altitude above sea level 376 m. Puga Average annual precipitation 466 mm. ( ? ) " Number of years 4 Northern latitude 21 41' M. R. Average barometric pressure 765 mm. I " Maximum temperature 34 o' " Minimum " 10 o' " Medium 23 o' Number of years i Annual Precipitation (C. M. O.) 1882 1154.6 1886 1165.2 1883 1215.0 1889 2109.3+ 1884 1247.2 1890 II2I.8 1885 1093.7 1891 1383.3+ Accepted average annual precipitation 1311 mm. 2 Number of years 8 RAINFALL IN MEXICO San Luis Potosi, San Luis Potosi, Mexico DATA Altitude above sea level 1890 m. Puga Average annual precipitation 398 mm. " Number of years 10 " Northern latitude 22 09' M. R Average barometric pressure 613.4 " Maximum temperature 33 9' " Minimum " i 8' " Medium " 17 4' Prevailing direction of the clouds W. " " " " wind E. " Average annual precipitation 389 mm. o Number of years 9 Annual Precipitation ( San Luis Institute and C. M. O.) 1878 432-4+ I8 9 531-2 + 1879 380.2 av. 2+ I8 9 I 257.6 av. 2 1880 359-2+ 1892 244.5 " 2 1881 444-0+ 1893 4I4.I " 2 + 1882 347-5 I8 94 229.1 1883 404.0+ 1895 285.7- 1884 189.9 I8 9 6 249.7 av. 2 1885 484.0+ I8 97 367.8+ 1886 403-3+ 1898 383.5+ 1887 506.8+ 1899 2OO.I 1888 504.8 av. 2+ I9OO 264.0 1889 331.0" 2 Accepted average annual precipitation 357.1 mm. Number of years 23 52 RAINFALL IN MEXICO The diagram relating to rainfall at San Luis could not be classified as one of the most irregular, since it does not, like in many other cities of small precipitation, depart very much from the average line of rainfall. The examination of the diagram will show a decrease of rainfall during the latter part of the period recorded, as subsequent to 1890 all years appear below the normal line with the exception of three of them, 1893, 1897, and 1898. RAINFALL I N MEXICO Tepic, Tepic, Mexico DATA Altitude above sea level 1051 m. C. M. O. Puga Average annual precipitation 1090 mm. Number of years 7 Annual Precipitation (C. M. O.) Era Prior to 1877 1844 1270.0 1845 1066.8 1846 1524.0+ 1847 1765-3+ 1848 1727-7+ J849 I 955-8+ 1850 1892.3+ 1851 1638.3+ 1852 1447-8+ '853 1333-5+ 1854 1855 1856 1857 1858 1859 1866 1867 1868 Average annual precipitation for era prior to 1877 Number of years 1651.0+ 1231.9 774-7 609.6 952.5 1854.2+ 1498.6+ 1384-3- 1663.7+ 1433.7 mm. 19 Era Subsequent to 1877 1885 I447-8+ 1890 1409.7+ 1886 1155.7 1891 1371.6 1887 1473-2+ 1892 1231.6 1888 1676.4+ 1893 1600.2+ 1889 1244.6 1894 1181.1 Accepted average annual precipitation, era subsequent to 1877 Number of years Average annual precipitation, figured out with all data at hand Number of years 1379.1 mm. 10 1414.8 mm. 2 9 RAINFALL IN - ITY M E X Oaxaca, Oaxaca, Mexico DATA Altitude above sea level 1546 m. Average annual precipitation 715 mm. Number of years 3 Northern latitude 17 04' Average barometric pressure 636.6 mm. Maximum temperature 32 9' Minimum " 6 2' Medium " 20 6' Prevailing direction of the wind W. Annual Precipitation (C. M. O.) 1878 578.0 1879 95 l -+ 1880 617.1 1883 858.9+ 1884 S^-S 1885 550-6 1886 940.9+ 1887 1080.7+ 1888 1161.0+ 1889 729-3 1890 i8 9 i 1892 1893 1894 1895 1896 1897 714.4 1032.4+ 849-2+ 1098.1 + 663.7- 7I3-3 700.2 843-9+ 880.5+ Puga M. R. Accepted average annual precipitation 814.7 mm. Number of years 19 The diagram relating to rainfall in Oaxaca shows a fall in the curve subsequent to 1893, the same as is noticed in the diagrams for other places I have prepared, but in a general way it does not indicate a decrease in rainfall, because prior to 1886 there are similar and even greater decreases in this place, the four years of minimum precipitation re- corded appearing prior to the above mentioned date. 55 RAINFALL IN MEXICO Morelia, Michoacan, Mexico DATA Altitude above sea level 1940 m. Moreno Average annual precipitation 728 mm. " Number of years 2 " Northern latitude 19 42' M. R. Average barometric pressure 608.8 mm. " Maximum temperature 31 5' " Minimum " i 5' " Medium " 16 8' Prevailing direction of the clouds W. " " " " wind S. S. W. " Year 1896 Annual Precipitation (C. M. O.) 1882 648.8 1898 707.9+ 1894 527.64- 1899 772.6+ 1895 837.2+ 1900 626.7 1896 619.9 1901 831.1 + 1897 580.3 Accepted average annual precipitation 683.5 Number of years 9 5'' RAINFALL IN MEXICO Jalapa, Veracruz, Mexico DATA Altitude above sea level 1321 m. Moreno Average annual precipitation J 54O mm. " Number of years 2 Northern latitude 19 31' M. R, Average barometric pressure 649.3 mm> " Maximum temperature 33 5' " Minimum " 5 6' " Medium " 18 5' Prevailing direction of the wind N. " Year 1896 " Annual Precipitation (C. M. O.) 1894 917.5 1898 2156.1+ 1895 1306.0 1899 1670.7+ 1896 1779.4+ 1900 1611.1 + 1897 1193-3 Accepted average annual precipitation 1519.2 Number of years 7 By examining Jalapa's diagram an increase of rainfall will be discovered, but this indication is of a very limited value owing to the fact that only a few years have been registered. 57 RAINFALL IN MEXICO Guanajuato, Guanajuato, Mexico DATA Altitude above sea level 2060 m. Puga Average annual precipitation 859 mm. " Number of years 6 " Northern latitude 21 01' M. R. Average barometric pressure 601.3 mm. " Maximum temperature 30 7' " Minimum " i 3' " Medium " 17 6' " Average annual precipitation 964.5 mm . " Number of years 5 " Annual Precipitation (C. M. O.) 1881 893.5+ J 892 452.0 1883 945-2+ 1893 53 2 -5^ 1884 503-8 1894 546.0 1885 1070.7+ 1895 578-2 1886 756.1+ 1896 524.2 1887 987.7+ 1897 639.5 1888 789.2+ 1898 798.4+ 1889 640.5 1899 631.3+ 1890 601.1 1900 651.1 + 1891 590.2 Accepted average annual precipitation 691.1 Number of years 19 I believe that none of the diagrams I have pre- pared is more interesting than that of Guanajuato, the same being the one that shows the curve in the form ofa swing and spread out wider, as it begins 58 RAINFALL IN MEXICO to fall in 1887 and rises about 1900 ; that is to say, it covers a period of fourteen years, an incident which does not occur in any of the other diagrams. Such a long lapse of time in which the amount of rainfall begins first by decreasing and then by rising without interruption, is not shown by any of the other diagrams I have prepared. RAINFALL IN MEXICO Aguascalientes, Aguascalientes, Mexico DATA Altitude above sea level 1861 m. Puga Average annual precipitation 591 mm. " Number of years 6 " Northern latitude 21 53' " Average barometric pressure 605.1 mm. " Maximum temperature 29 5' " Minimum " 2 8' " Medium " 18 6' " Annual Precipitation (C. M. O.) 1879 418.4 1885 762.4+ 1882 675.0+ 1886 594.5+ 1883 529.6 1889 542.2 1884 474-3 Accepted average annual precipitation 57-9 Number of years 7 RAINFALL IN MEXICO Linares, Nuevo Leon, Mexico DATA Altitude above sea level 362 m. Minimum temperature in six years 9 in February, n to 14, 1899 Medium temperature in six years 22 4' Number of years 6 Annual Precipitation and Number of Rainy Days ( Martin Stecker ) 1896 79656 ^99 78949 1897 8874-60 1900 990-|-66 1898 543 5 1 !9 01 1014+53 Accepted annual precipitation 836 mm. Number of years used in calculation 6 The examination of the above diagram does not permit us to appreciate whether there has been any increase or decrease of annual rainfall at Linares, because of the limited number of years observed. Three of the years recorded appear over and three under the normal line. In the curves relating to monthly precipitation, which I have also prepared with the data kindly fur- nished me by Mr. Stecker, it appears that the pre- cipitation is heavier during two portions of the year, which fact does not happen in other localities. RAINFALL IN MEXICO The curves comprise two ascending parts, pretty well marked in the years 1896, 1897, 1899, and 1901. There are one or several months of heavy precipitation missing for 1898 in order to determine the first rise of the curve, and during 1900 the second rise was not so well characterized. RAINFALL IN MEXICO Zapotlan, Jalisco, Mexico DATA Altitude above sea level 1530 m. Moreno-Puga Northern latitude 19 36' M. R. Average barometric pressure 636.8 mm. " Maximum temperature 36 9' " Minimum " 6 o' " Medium 20 5' Prevailing direction of the clouds N. E. " wind S. E. Number of years i (1896) " Annual Precipitation (C. M. O.) ( S. Diaz) 1894 663.0 1898 1027.7 + 1895 836.3 1899 963-5+ 1896 915.9+ 1900 ioo8.i-f 1897 886.5 1901 iooi.8-f Accepted average annual precipitation 912.8 Number of years used in calculation 8 The examination of the diagram shows an increase in rainfall during the years recorded and the slight decreases that appear therein, the curve never falls to the point equal to that of the precip- itation of the previous year in each case. In the first period of four years there is only one year, 1896, that exceeds the normal line a little, the other three being below the latter. In the second period of four years the whole four had a precipitation higher than the accepted average. 63 RAINFALL IN MEXICO The curves relating to monthly precipitation, during the years recorded, show a regular condition during the rainy season, rainfall being fairly well distributed, as starting in April and continuing through May and June, the curve keeps on rising and it does not drop down until November or December of each year. RAINFALL I N MEXICO Queretaro, Queretaro, Mexico DATA Altitude above sea level Annual precipitation Number of years Northern latitude Average barometric pressure Maximum temperature Minimum " Medium " Prevailing direction of the wind Number of years 1850 m. 569 mm. 17 20 35' 613.8 mm. 33 i' 18 i' E. 3 Puga M. R. Annual Precipitation (C. M. O.) 1877 577.I + 1878 675.1 + 1879 562.9+ 1880 638.5+ 1881 665.6+ 1882 480.0 1883 577.8+ 1884 295.4 1885 631.8+ 1886 606.7+ 1887 500.0+ 1888 480.0 1889 440.9 1890 539.9+ 1891 471-1 1892 374-7 1893 641.1 + 1894 372.2 1895 252.7 1896 290.0 1897 518.6+ 1898 509.1 + 18 99 563-7+ 1900 338.2 1901 214.4 Accepted average annual precipitation 489.1 mm. Number of years used in calculation 25 RAINFALL IN MEXICO The examination of the diagram corresponding to Queretaro clearly indicates that there has been a decrease in rainfall in that city, and it shows the period of drouth appearing in other diagrams pre- pared by me, with a considerable fall of the curve, in the shape of a swing, corresponding to the last period of five years. The only complete data relating to monthly pre- cipitation that I have been able to secure are those from 1893 up to date, and from the examination of the proper curves I have drawn, it can be seen that there is no uniformity between the curves covering several years. 66 RAINFALL IN MEXIC O Hacienda del Carmen, Guemez, Tamaulipas, Mexico Annual Precipitation ( Francisco Benitez Leal, C. E.) 1897 866-f 1900 373 1898 827+ 1901 823+ 1899 535 Accepted average annual precipitation 684.8 mm. Number of years 5 Although there are only five years of observa- tion at the latter place, the proper data having been furnished to me through the kindness of Mr. Benitez Leal, I have endeavored to prepare the correspond- ing diagram, and I will take into account, in the general study I am preparing, the course of precip- itation at Guemez, feeling really thankful that I was able to secure the necessary data, as it is the only point within the State of Tamaulipas wherefrom I succeeded in getting the desired information. The diagram shows a decrease from the first year recorded until we get to the one next to the last, but an increase in the precipitation takes place immediately after such period, which places the line in the extreme almost as high as the starting point. The curves relating to monthly precipitation are very irregular, and there is not a single special fea- ture about them that would make them worthy of notice. 6 7 RAINFALL IN MEXICO I have made use of the data I was able to obtain, believing that they comprise the greater part of information that could be utilized in a study of this nature. I have prepared the diagrams of annual precipitation for each of the localities where there are meteorological observatories, and the curves relating to monthly rainfall for such points as I have succeeded in securing the necessary data, and I have made notations pointing out the peculiar- ities I have considered worthy of mention when pre- paring the former as well as the latter. I will now proceed to make a recapitulation of the latter data to the end of discovering whether they will serve to decide the following questions : first. What has been the change in the rain- fall system of the country ? Second. The change that may have occurred, has it been permanent during the last quarter of the nineteenth century, or has it been more marked at certain epochs ? Third. Has the change been general all over the country, and what may have been the cause of such change ? Fourth. What may we expect in the future ? Fifth. What can we do to remedy the evil ? See Enclosure No. 2. (A synoptical chart of pluviometric observations ). RAINFALL IN MEXICO Study of the Chart In the first column appear the names of the localities from where I have been able to secure plu- viometric reports. In the second column appear the periods of years for which I have pluviometric reports and the names of the persons who were so kind as to furnish me with them, the majority of said persons being the managers of the respective observatories. The ab- breviation, C. M. O., means that the data have been secured from the Central Meteorological Observa- tory of Mexico, which institution published some time ago a pamphlet containing some of the data in question, the same having been corrected at 'a later date. Column three shows the averages I have ac- cepted, calculated from the greatest possible number of years, subsequent to 1877, relating to amount of annual rainfall had at the corresponding localities. These figures indicate in the diagram of precip- itation the value of the horizontal line to which I have subjected the elevations of annual rainfall. Column four denotes the number of years upon which the above averages were calculated, to the end that the correctness of each may be appreciated. Columns five and six denote, respectively, the maximums and minimums of annual precipitation during the whole period recorded, and the years corresponding to each column. 69 RAINFALL IN MEXICO Column seven indicates the separation between the maximum and minimum annual precipitation. The latter difference is remarkable in regard to sev- eral observatories, and the same clearly demonstrates the irregularities of our rainfall, but I do not believe that this is an exceptional feature of our climate, as some people contend, as similar and even greater differences are recorded in other countries. My intention, in preparing columns five and six, was to study whether any relation could exis- between the succession of years of maximum and minimum precipitation, with the increase and de- crease of the average amount of rain falling annu- ally at each place ; but I have failed to discover any relation whatever, since in sixteen cases the year of heavier rainfall comes before the year of less precip" itation, and in seventeen cases the matter appears to be the other way. The difference, therefore, would not justify any deduction. In order to investigate whether there is any ten- dency in our rainfall to decrease or increase, if we had in all our observatories the pluviometric records for the same period of time, all we would have to do would be to divide such periods in two epochs, and compare the average precipitations calculated for each epoch ; but we are not in condition to do that, because only a few observatories have any registers prior to 1877 ; there are some which were in opera- tion during a certain period of years but do not exist at present ; others were established lately and con- RAINFALL IN MEXICO tinue to make pluviometric observations, and there are many which did work continually. As it has been my desire to base my conclu- sions upon the greatest possible number of years recorded, and have tried to avail myself of all of the few elements to be depended upon, what I have done is, to divide the era that has been recorded in each case in two periods, first and second, for which I have calculated separately the proper average pre- cipitation, entering the same in columns eight and nine. When the total number of years recorded is an odd number, I have not taken into consideration the precipitation of the middle year of the series, to the end of avoiding comparison between averages calcu- lated with a different number of years, although I am convinced that the results would not have been altered in none of the sixteen cases of an odd series of years. In column ten I denote by means of the marks of plus and minus whether there has been any increase or decrease in the average precipitation of each period, and the result thus obtained is, to my regret, quite eloquent, there being twenty-one minus signs against twelve plus marks. We could argue against the foundation of the above conclusion that the first and second periods, in the different cases, do not refer to the same era, that is to say, that the same years are not contained in all of the latter, because, speaking about the City RAINFALL IN MEXICO of Mexico, for instance, the first period runs from 1877 to 1888, while when referring to Linares it runs from 1886 to 1898 ; but I believe such argu- ment could be destroyed by the sole idea that the object of the comparison, condensed in column ten, is to find out only whether there has been any gen- eral tendency towards a decrease or increase of rainfall. The results of such comparison, for the era I have studied, would attain the greatest possible value if all the observatories could furnish pluviom- etric reports from 1877 to 1901, but, unfortunately, this is not so. After this consideration, the results of such comparison would be of the greatest possible value if there was an equal number of observatories, where observations had been made at the com- mencement of the period of twenty-five years, and which afterwards discontinued the same, to the num- ber of observatories established during the second period of the above mentioned era. This, also, is not the case. The majority of the observatories have been recently established, and this would give greatest weight to the argument above referred to. Now, then, what influence could such cause of error have in the results shown by column ten ? As may be seen afterwards (column twenty- three) the tendency to an increase of rainfall during the last period of five years, in relation to the pre- ceding period, is very remarkable, and for that reason the influence of such cause of error would RAINFALL IN MEXICO serve to increase the plus marks in column ten, because seven out of the twelve plus marks appearing in the latter column refer to registers carried during less than ten years in the two last periods of five years each, therefore, the plus would perhaps become minus marks if the observation had reference to another era. The error that might have been com- mitted in speaking of the whole era of 1877 to 1901, with the data on hand, is, therefore that of obtaining a lesser difference than the real one, between the less and plus marks, and while this may be so, the above mentioned objection is superseded and the conclusion appears well founded. In columns eleven and twelve I have marked the number of years under the normal precipitation of the whole era, as had in the first and second periods, for each observatory, and the result of the comparison corroborates the figures of column ten, since in the second periods there have been 137 years under normal conditions against 115 had in the first periods. Right afterwards I have divided the total era under consideration in five periods of five years each ; I have calculated the averages of precipita- tion in each one of them, showing the number of years taken as a basis of calculation, to the end of discovering their correctness as an average ; I have prepared a column for data prior to 1877, and the comparison between the various columns, from num- bers thirteen to twenty-five, enables us to study if 73 RAINFALL IN MEXICO the tendencies of rainfall towards increasing or decreasing have been more apparent at any given epochs. RAINFALL IN MEXICO Recapitulation First. There has been a decrease of rainfall in Mexico during the last twenty-five years. (Col- umns ten, eleven and twelve of the Chart). This statement, which, in the opinion of many persons who believed in the decrease, may appear as a fact which does not require corroboration, since it was well known, should, however, be considered by our farmers not as a source of despair, but, on the contrary, as an encouragement to improve agri- cultural systems, to prevent the reckless felling of forests, and to reduce the burden of live stock from grazing lands ; to promote all kinds of works that will cause the soil to absorb a greater amount of rain water, and to make provision for the collection of such water, as well as that from creeks and rivers. The above statement should also impress the idea upon the mind of our authorities that the latter 1 works and improvements ought to be encouraged as much as possible, it being a matter of vital necessity to do so, as any efforts made at an early date will facilitate the work and enhance its usefulness. Second. The decrease in rainfall has not been so general as has been claimed, nor even regular during the period from 1877 to 1901. Pluviometric registers, during the years recorded, show an in- crease in Zapotlan, Linares, Aguascalientes, Jalapa, Morelia, Oaxaca, Huejutla, Pabelldn, Me'rida, Mon- terrey, Pachuca, and Guadalajara. RAINFALL IN MEXICO Between the first five years (1877 to 1881) and the second five years (1882 to 1886) we dare say there was an insignificant decrease (column 1 7 : ii-8+). From the second five years (1882 to 1886) to the third five years (1887 to 1891) there occurred an increase also insignificant (column 19 : 10-13+). From the third period (1887 to 1891) to the fourth period (1892 to 1896) there was a gen- eral decrease in the rainfall (column 21 : 18-4+). From the fourth period (1892 to 1896) to the fifth and last period (1897 to 1901) there was a very remarkable general increase in our rainfall (column 23 : 4-22+). The results shown in columns twenty-one and twenty-three confirm the majority of the remarks I made while preparing the diagram of precipitation. The above mentioned decrease subsequent to 1891 and increase after 1896, is but the result of the falls in the form of a swing I remarked in making up the diagram, which falls, though failing to coincide in the same years in the different localities mentioned, do appear wtth some frequency in the latter part of many of the lines of precipitation. Third. The cause of the decrease of rainfall during the period studied must have been foreign to the action of men, because, should the cause be one of those generally claimed (development of railway system, felling of the forests) the effects would have increased and would have become more noticeable in proportion to the causes originating the same. 7 6 RAINFALL IN MEXICO We never before had as many railroads or destroyed as many forests as we have in the last five years, and, notwithstanding that, the latter period, as com- pared with the one preceding it, shows an increase of rainfall in twenty-two cases out of four where there has been a decrease. The falling of our forests may have some influ- ence in modifying our climate, and perhaps the change will be more marked in the future than it has been in the past, but it is not the principal cause of the changes claimed by public opinion. The injurious influences from the reckless fell- ing of the forests have been more instrumental in causing the disappearance of springs, especially in the mountain districts, than in the modification of our system of rainfall. The magnitude and universality of the decrease attributed to our rainfall, and the increase of its irregularity, have been exaggerated in the public mind, there being three general causes which prin- cipally affect the case : The greater facility one has to remember and appreciate exceptionally bad years than to remember and appreciate those which hap- pen to be exceptionally good ; the opening of new waterworks required by an increase of cultivation of irrigated land in preference to those depending on rainfall, and the scarcity of manual labor for agri- cultural purposes (first part of this study). The increase of rainfall in the last period of five years (column 23) is really encouraging, and it 77 RAINFALL IN MEXICO would be more so if we did not have to record the general result shown by column ten, and so stated in the first part of the recapitulation. There has been, lately, some tendency of in- crease in our rainfall, some localities have had in the last years rains which surpass the amount cal- culated as normal, but we have not sufficient data to support a general prediction. There are a few cities, as may be seen from the diagrams I have prepared, whose lines of precipita- tion rise during one, two or three years, but only to come down again during similar lapse of time. I be- lieve that in such places, considering the character of the curve, bad years are to occur after a series of two or three years of heavy precipitation, as they gener- ally alternate one another in series of short duration. There are other localities where great falls of the line precipitation occur, during a long series of years, as has been noted in the proper diagrams. In such places the continuance of a series of years slightly over the normal elevation, or any indication to drop in the curve of precipitation must be a cause of alarm, while the contrary must be received with marks of gratification and confidence. It is the widely repeated prophecy of Joseph on account of the dreams of the King of Egypt. Fifth. In order to provide for our future in this respect, whatever the same might be, we should endeavor to unite the efforts of administrative action with those of private individuals and farmers. 7 8 RAINFALL IN MEXICO Confining myself to the latter point, recom- mendation should be made in the first place to create partial pools and jetties to control the drain- age of rainfall and thus increase the absorption of the latter ; the construction of all classes of works for the purpose of collecting water should be en- couraged ; a sensible proportion between the num- ber of live stock and the surface of grazing lands should be maintained ; we should make a study of and endeavor to diffuse our useful wild plants, which are, without doubt, the ones which can better prosper under the conditions of our climate and soil ; we ought to better the elements of our natural prairies ; to build watering places for stock in the respective farms in order that the former may not have to travel long distances in search of food, destroying pastures where the soil is more or less sandy, and forming footpaths which turn in creeks and facilitate the drainage of rain water ; a sensible felling of the forests and the use of improved methods of cultivating will help to bring about an economy of water. If man has not been given the power to modify, so far, the climate, causing the increase of rainfall, he can, at least, make better use of the small quan- tity of water at his disposal and help nature imitat- ing it, to the end that rainwater may be absorbed, retained, evaporated, and utilized upon the soil instead of letting it run into the sea. UNIVERSITY OF CALIFORNIA L BERKELEY Return to desk from which borrow This book is DUE on the last date stam; MAR * 23r,eb'49Ml ft* ' LD 21-100m-9,'47(A5702sl6)476 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. ^ ' REC'D LD ^ ,,n UO LD 21-100m-6,'56 (B9311slO)476 General Library University of California Berkeley