Regional Water Sources Overview
The purpose of this section is to provide you with information that will help you be aware of the basic water issues affecting the cities of El Paso, Las Cruces and Ciudad Juárez. Additional and more precise information is available by contacting the city utilities, planning or public information departments.
The City of El Paso is located in the far western corner of Texas. Back in the 1800's, the city relied on surface water from the Rio Grande. Those were the years when quantity was plentiful and quality was the only concern. El Paso began a rapid switch of its water supply to groundwater after assessing problems arising from flood damages, large quantities of mud in the river, and with the first well drilled in 1892. During the first half of the century, the city relied totally on groundwater. By 1976, the city realized that the Hueco Bolson was a finite source of groundwater, thus, the city started obtaining surface water rights to use once again, Rio Grande water.
The more than 580,000 residents of El Paso, over 62,000 in Las Cruces and almost one million in Ciudad Juárez constitute a regional population of about 1.8 million. The population in the three cities has been steadily increasing and with it the demand for additional water supply capability. Ciudad Juárez and the city of Las Cruces rely entirely upon groundwater to meet their water supplies. Las Cruces draws water from 31 wells located in the Mesilla and the Jornada del Muerto Bolsons. El Paso's water sources include surface water from the Rio Grande and underground water from the Hueco and the Mesilla Bolsons. Ciudad Juárez draws water from the Hueco Bolson exclusively.
The El Paso Water Utilities provides water to customers within the city limits and, is a wholesale supplier to Westway, Fort Bliss and the Lower Valley Water District. Las Cruces supplies water to city customers, New Mexico State University and the town of Mesilla.
There is a large variability in the water consumption during the year. Typically, maximum consumption occurs in June or July and minimum consumption occurs in December or January. The highest production demand occurs during the summer season, when area temperatures are hot, air conditioners are running constantly and irrigation needs are high. During the growing season, April to October, El Paso uses both surface and ground water to meet its demands. For the other months, only ground water sources are utilized as water from the Rio Grande is unavailable.
The Hueco Bolson is the principal aquifer for the El Paso-Juárez area and occupies the majority of El Paso county, extending from the Franklin mountains on the west to the Hueco mountains on the east. The Hueco Bolson extends northward into New Mexico and southward into Mexico. El Paso currently depends on groundwater from the Hueco Bolson for about 40 percent of its water needs. Ciudad Juárez, which has roughly double the population of El Paso, depends 100 percent on water from the Hueco Bolson to meet its demand.
El Paso's Water Resource Management Plan, prepared in 1990, estimates that by the year 2025 the Hueco Bolson will be depleted of all fresh water that can be economically retrieved. However, the Hueco Bolson contains an untapped layer of brackish water (water which has a greater amount of salt than allowed by Federal and State drinking water standards). This condition makes desalination an attractive but costly option to increase water supply quantities for the city. El Paso has 74 operational wells in the Hueco Bolson with a total capacity of 200 Million Gallons per Day (MGD). In 1995, these wells pumped 38.7 percent of El Paso's total water demand.
The Mesilla Bolson is located primarily in New Mexico with small portions in Mexico and Texas. The northern boundary of the Mesilla Bolson is the Robledo and Doña Ana mountains, and much of the southern boundary is in Mexico. The western boundary is formed by the West Potrillo and the East Potrillo mountains, while the eastern boundary is the Organ, Franklin, and Juárez mountains.
The main hydrologic feature of the Mesilla Bolson is the Rio Grande, entering the basin through the Selden Canyon and running through the Mesilla valley and exiting at the El Paso narrows. The Rio Grande and the irrigation system fed by the Rio Grande are considered the main source of recharge to the Mesilla Bolson. Water levels in the aquifer remain relatively constant with fluctuations being primarily in response to flows in the Rio Grande and irrigation canals and drains.
El Paso has 31 wells that pump water from the Mesilla Bolson with a capacity of 38.6 Million Gallons per Day (MGD). However, because of system distribution constraints, not all that water is used. The Mesilla Bolson provided 18.2 percent of El Paso's water supply in 1995. The city of Las Cruces has been pumping water from the Mesilla Bolson for about the last 50 years. In 1993, it extracted an average of 16.7 MGD.
Jornada del Muerto Bolson
This bolson is located on the eastern side of Las Cruces. It is bordered on the east by the Sierra Obscura, Organ, and San Andres mountains and on the west by the Doña Ana, Caballo, and Fray Cristobal mountains.
The Rio Grande originates in southern Colorado and flows from the San Juan mountains through New Mexico. It continues southeastward as the International Boundary between United States (Texas) and Mexico. The Rio Grande has been the corner stone for the development of this regional area. Spanish explorers found Pueblo Indians using its water for irrigation of crops. The Indians had built an extensive distribution canal system making irrigation possible along the river banks. The Spaniards used the same canal system to distribute water to their settlements.
Competition for Rio Grande water has occurred since the late 1880's. In 1906, the Convention for the Equitable Division of the Waters of the Rio Grande was signed between Mexico and United States. With this agreement, United States agreed to provide Mexico 60,000 acre-feet of water during non-drought years. In 1938 the states of Colorado, New Mexico and Texas signed the Rio Grande Compact for the distribution of 790,000 acre-feet of water below Elephant Butte Reservoir.
Currently, the Rio Grande supplies about 40 percent of El Paso's water needs. In order to stretch current underground water supplies, El Paso, Las Cruces and Ciudad Juárez must work in cooperation to acquire additional water rights, obtain delivery of surface water on a year-round basis and increase water treatment capacity, along with a consumption reduction through aggressive water conservation programs. Surface water treatment plants in El Paso operate at full capacity approximately seven months of the year. During the rest of the year, surface water from the Rio Grande is unavailable or the water quality is too poor to be used for municipal water supply.
Water quality in the Hueco Bolson has been degrading over time as a result of ground water withdrawals and other human activities. The degradation is more pronounced in the valley area than the mesa area. Typical water quality concerns in the Hueco Bolson are increases in either total dissolved solids (TDS), chloride, or nitrates. Resulting from historical return flows, urban runoff, irrigation water and leaching nitrates from the desert soil.
The water quality pumped from the Mesilla Bolson improves with the depth of wells in the Canutillo wellfield. While the aquifer is showing some level of water quality deterioration, the overall quality is better than in the Hueco Bolson. Water quality in the Mesilla Bolson is a function of the distance from the river and drains, depth of wells, season and duration of the pumping. Typically water quality degrades with increasing distance from the river, decreasing distance from drains, and improves with the depth.
Water quality varies greatly during the year as a result of return flows from agricultural activities below the Caballo dam. The sulfate and TDS values are high during the non-irrigation season. They peak right after the irrigation releases start in late winter, and rapidly improve during the season. The water quality improves sufficiently to be utilized by the water treatment plants. However, near the end of the irrigation season the quality generally reaches a point where it can no longer meet Texas Natural Resource Conservation Commission (TNRCC) Drinking Water Standards. The water quality in the river remains below TNRCC standards until the next irrigation season.
The cities of El Paso, Las Cruces and Ciudad Juárez have a climate typical of the arid to semi-arid regions of southwestern United States and northern Mexico. Days are warm, and nights are cool, with low relative humidity, abundant sunshine and a yearly precipitation of about eight inches. Precipitation in this area is mainly in the form of brief but heavy thunderstorms during the monsoon season, which occurs from mid-July to mid-September. The low rainfall combined with high evaporation rates, about 100 inches per year, makes it necessary to irrigate crops and landscapes during the long annual growing season from mid-March to mid-October. Snow is rare during the winter season. Table 1 lists monthly maximum, minimum, and average temperatures; precipitation and open-pan evaporation for 1997.
Table 1. Maximum, minimum, and average; precipitation and open-pan evaporation for El Paso in 1997.
|Month (F°)||Max (F°)||Min (F°)||Avg (F°)||Precipitation (inch)||Open-Pan Evap (inch)|