WSP10396 - Laserfiche WebLink

Home Browse Search

:",., ,., ~ 1 '.'. ".,,:1. GENERAL EFFECTS OF DROUGHT ON VVATER RESOURCES B43 drought, and production in the driest year was less than 25 percent of the maximum annual production, The hydroelectric plants operated by the Lower Colorado River Authority on the Guadalupe River generated 36.5 million kwh during 1949 but less than 3 million kwh in 1956, because of decreased flow in the river. Drying of some streams, lakes, and reservoirs elimi- nated the fish population, but this destruction included numerous coarse fish too. On the other hand, some large reservoirs (for example, the Buchanan Reservoir, fig. 14) held a high proportion of their capacity throughout nearly every year of the drought. Emergency activities during the drought have in- cluded various methods of water rationing, such as lawn watering at even-numbered houses today and odd-num- bered houses tomorrow, no car washing, as well as ar- rangements for hauling water or otherwise obtaining temporary supplies during the period of shortage. In some places emergency measures were necessary despite considerable progress toward development of assured water supplies for the future. For example, the city of Dallas depended for many years upon Lake Dallas, but the storage was reduced by drought so seriously as to be inadequate by 1953. The city was also allocated 188,000 acre-feet in Grapevine Reservoir, completed in July 1952, and 415,000 acre-feet in Garza-Little Elm Reservoir, completed in November 1954, but these reser- voirs did not fill during the drought. Hence, Dallas, facing a critical shortage of water in February 1954, began pumping from the Red River, which was saline enough to give Dallas the temporary and dubious dis- tinction of using water that was more highly mineral- ized than that in any other large city in the Nation, Comparison of cotton production in 1945 and 1955 illustrates the effect of drought upon the irrigation economy, although production was influenced also by acreage allotments and other factors independent of water supply. In 1945 the total State production was 1,794,000 bales from 6 million acres, or an average yield of 143 pounds per acre; about 40 percent of the total was produced in the western part of the State. The total production in 1955 was 4,039,000 bales from 6 mil- lion acres, an average of 281 pounds per acre and an in- crease of 225 percent in total production over that in 1945; about 70 percent of the total was produced in the western part of Texas, The combination of success on irrigated farms and crop failures on farms that de- pended on precipitation produced a marked trend in the agricultural economy from small dryland farms to large irrigated farms. In many instances this has meant a geographic shift, involving abandonment of small farms and development of new acreage where ample water supplies are available for irrigation. One result of this trend was a reduction from about 330,000 farms and ranches in Texas in 1950 to 290,000 in 1956. The drought encouraged conservation practices such as the use or reuse of water that onCe went to waste, Sewage-treatment plants have converted municipal waste water for use, and the sewage effiuent from San Antonio and Lubbock, for example, is used for irriga- tion, Industrial plants, by recycling cooling water, have been able to operate with less makeup water or to expand operations with no increase in intake, Increas- ing numbers of canals and ditches carrying irrigation water have been lined with concrete or replaced by underground conduits since 1945; this practice is of especial value where the water lost from the canals by seepage could not possibly be recovered frOm ground- water reservoirs. In many areas consumptive waste; of water has been reduced by eradication of such native vegetation as saltcedar' and water hyacinth. Conserva- tion is practiced by some people an the time, but there is more universal attention to it during periods of water deficiency. NEW MEXICO The drought of 1942-56 was longer and more severe in New Mexico than in any other State in the Southwest. The entire State has been recognized as a drought- disaster area. In most places even the average precip. itation is insufficient. for cultivation of crops without irrigation, but there is some dry farming, principally of wheat, in the eastern part of the State; as much as 60 percent of these crops fa'iled during the dry year 1956, The range in all parts of New Mexico deteriorated because of deficient precipitation year after year. From 1951 to 1956 the number of cattle was reduced each year owing to scarcity of forage. The seriousness of the de- pletion of the range by drought has been pointed up in a report by the Rocky Mountain Forest and Range Ex- periment Station (1956, p, 61) : "Over the 40-year period 1915 to 1954 the average ba- sal density of black grama grass (Bouteloua eriopoda), the most important forage plant on the rang", on quad- rats protected from grazing has varied greatly, Density was reduced to 0,3 percent of the surface area in 1923 as the result of the dry period start.ing in 1916. With the return of rains, density of black grama again in- creased until in 1933 it was 9.5 percent, the maximum for the period of study. As the result of the current drought, black grama has disappeared from the quad- rats. The density each year is correlated with the amount of rainfall received during the preceding 15 months * * *. Such variations in plant cover affect the livestock production. Over the 40-year period, . stocking has been virtually eliminated twice as the re- sult of drought, while in most favorable years stocking