Irrigation has been used for agriculture in various parts of the world for at least 4,000 years. In what is now the United States it possibly had its beginnings in West Texas or New Mexico. There is evidence of a prehistoric desert agriculture in a few West Texas localities. The Spaniards found New Mexico and Arizona Indians growing crops in an arid climate by collecting and diverting run-off water to the planted fields. Brush dams caught the flow of a dry arroyo when flushed by a thundershower and watered the thirsty plants, even though no rain fell on the field itself. Records left by Francisco Vázquez de Coronado and other Spanish explorers indicate that the Indians had developed and established irrigation systems near the sites of present-day El Paso and Pecos, supplied respectively by the Rio Grande and the Pecos River. The first Europeans to practice irrigation in Texas were the Franciscans, who between 1716 and 1744 directed the construction of acequias to supply water for domestic use and irrigation at seven missions in the San Antonio area. Parts of one rock-lined acequia madre ("mother ditch") are still in use. The first field crop known to have been grown under irrigation in what is now called Texas was corn, which was cultivated successfully by both Indians and missionaries. In the Gulf Coast area and in the lower Rio Grande valley, salinity and high water tables have been favorable to citrus fruits, vegetables, and cotton. Grain, cotton, alfalfa, and pasture grasses are the principal crops under irrigation in the western sections of the state and on the High Plains.
Large-scale irrigation began in Texas with the construction of canals in the vicinity of Del Rio in 1868. In the 1870s development began on the Pecos River, in the lower Rio Grande valley, and in the Fort Stockton area. Modern projects began along the Coastal Plain and in the El Paso valley during the 1890s and on the High Plains in 1920. In 1913 the Texas legislature passed the first major irrigation act, which called for the establishment of the Board of Water Engineers to regulate water appropriations. A series of dry seasons (1916–18) aroused renewed interest in irrigation from storage reservoirs, and a constitutional amendment was adopted providing for the formation of water-conservation districts by landowners. Whereas the previous irrigation projects had been largely private ventures, most of the new ones were formed under the district act, and most of the former private projects were taken over by public agencies and operated as a nonprofit service to the land. The use of irrigation continued to increase throughout the first half of the twentieth century. In 1948, of the nearly 30,000,000 agricultural acres in the state, 2,884,700 acres was under irrigation. Irrigated land accounted for about 10 percent of the state's harvested acreage. Irrigation was practiced on 29,779 farms; sprinkler or overhead systems were used on more than 850. In some areas irrigation was absolutely necessary for successful agriculture. In others, rainfall was normally sufficient to sustain plant growth, but production was greatly increased by supplemental irrigation.
The major irrigation systems of the state depend upon two water sources: surface streams and underground water. The main regions that use streams are the lower Rio Grande valley, the Colorado River basin, and the Pecos River basin. Most of the water in these areas is considered good for irrigation, although the sodium content is slightly higher in the waters of the more western streams. The High Plains, the El Paso valley (also partly supplied by the Rio Grande), the Winter Garden district, and the Gulf Coast area mainly use underground water. According to the state Board of Water Engineers, the number of wells in these areas increased from 600 in 1936 to 4,300 in 1949, and the number of acres increased from 80,000 in 1936 to 550,000 in 1949. The irrigation acreage supplied by groundwater pumped from wells was said to have expanded more rapidly in Texas than in any other area in the United States. Methods of irrigation established in various sections of the state depended upon the crops to be grown and the available water supply. In the rice belt the common method used was border flooding or pans. In the Valley the basin flooding method was used for citrus fruit and the furrow or row method was used for vegetables and field crops. The row method was followed also for cotton and grain crops in other sections of the state.
Irrigated land in Texas increased to 3,131,534 acres by 1950. The growth was largely a result of the rapid development of irrigation on the High Plains, which was supplied exclusively with high-quality groundwater from the underlying Ogallala sands. Irrigation of the region continued to grow spectacularly—more rapidly than any development elsewhere—to 5,894,686 acres by 1974. The High Plains was one of the largest irrigated areas in the United States and represented 65 percent of all Texas irrigation. The amount of irrigated cropland harvested increased from 10 percent in 1948 to about 25 percent during the mid-1960s, to 72 percent in 1973. In 1974 there were 8.5 million acres in Texas under irrigation. Of that total, 22 percent (more than 1,800,000 acres) was irrigated by sprinkler systems and the rest was watered by surface systems that channeled water in borders, rows, and field levees. The field levees were used mainly for rice. Many irrigation systems employed efficient pipelines or lined ditches to prevent water loss. Drip irrigation generated some interest, especially for tree crops, and was used on 4,500 acres; thereafter the method became standard for many kinds of orchard. Eighty percent of the total irrigated acreage came from water pumped from wells. Important groundwater-supplied irrigated areas included the Winter Garden Region and adjacent lands below the Balcones Escarpment, the Trans-Pecos farms of Reeves, Pecos, and Ward counties, the Marfa, Van Horn, and Dell City vicinities, and part of the Gulf Coast, as well as several north central Texas localities (where, especially during the 1960s, there was an increased use of sprinkler systems for peanut growing). Major areas supplied with surface water were the lower Rio Grande valley, portions of the Gulf Coast rice-growing area, the El Paso valley area, and alluvial lands along the lower Brazos River and other Texas rivers and tributaries. An increasing acreage in small tracts was being irrigated from small upstream impoundments.
Water availability will determine how much of the arable land in Texas is irrigated in the future. Throughout the second half of the twentieth century aquifers were being depleted faster than they could be recharged. A comprehensive Texas water plan was developed in the 1960s, and an amended one published in the 1980s offered an analysis and prediction of Texas water needs to the year 2030. Conservation practices that can help guarantee future irrigation include optimum use of soil moisture through monitoring and use of mulches, the planting of less water-intensive crops, use of the sprinkler, drip, and trickle methods, and the use of evaporation suppressants on the soil surface. In 1991 the total irrigated acres in the state had decreased to six million. The southern High Plains still accounted for the largest portion—68 percent. Of the total irrigated acres in Texas, 34 percent was watered by sprinkler irrigation. Seventy percent of all irrigation was from wells. The use of drip irrigation had increased somewhat, to 55,000 acres. Irrigated cropland produced 30 percent of the state's total harvested acreage, which accounted for 50 to 60 percent of the value of all crops produced. The decline in irrigated acreage was attributed to decreasing groundwater supplies and higher fuel prices.
See also AGRICULTURE, ARTESIAN WELLS, DRAINAGE DISTRICTS, IRRIGATION DISTRICTS, SURFACE WATER, UNDERGROUND WATER, WATER AGENCIES AND PROGRAMS, WATER CONTROL AND IMPROVEMENT DISTRICTS, WATER IMPROVEMENT DISTRICTS, and WATER LAW.