Aquifers Aquifers or Bolsons are underground areas that store significant amounts of water. After rain or melted snow the water will evaporate, get used by plants, runoff onto surface areas to rivers, streams, or lakes, and percolate through the porous soil and fill in between the spaces of soil and rocks. Not all aquifers are the same; there are different soils, rocks and mineral types that make each aquifer unique. The aquifers in the El Paso area consist of very fine-grained sands and gravels. Water stored underground may be thousands of years old or only days old, it depends on the depth of the aquifer. Hueco Bolson The Hueco Bolson is the principal aquifer for the El Paso-Juarez 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. In 2002, El Paso pumped about 30 percent of its water from the Hueco Bolson. In 2001, it was 44 percent. In 2000, it was 47 percent. In an effort to meet future demands the Hueco Bolson will continue to be used as a major source of water for the El Paso Water Utilities. This bolson will produce water that is either fresh or slightly brackish, for it contains a layer of brackish water (water which has a greater amount of salt). After many years of groundwater pumping, the quality of the groundwater in selected areas of the Hueco Bolson has become more brackish. As a result of these concerns about the water availability and levels of salinity in the El Paso area, groundwater flow models are being used as a tool to predict how aquifers might respond to pumping and to better understand the complex interaction between the fresh and brackish water. The brackish water will be desalinated as part of the Fort Bliss/El Paso Water Utilities Joint Desalination Project. The project is underway as the plant is designed with the capacity of 27.5 million gallons per day and a learning center to assist in community understanding of the treatment process of drinking water and the awareness of the challenges this region faces in the Chihuahuan Desert. The plant is expected to be operational in the year 2006. Ciudad Juarez, which has roughly double the population of El Paso, depends 100 percent on water from the Hueco Bolson to meet its demands. The groundwater in Juarez is brackish and other future sources of quality water are being investigated. Mesilla Bolson 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 Dona 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 Juarez 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. Glossary Water Table The top of the underground area where every available space is filled with water (saturation). Confined Aquifer. An aquifer that is surrounded by impermeable layers that transmit water more slowly than the aquifer. This aquifer is under pressure that can also be called an artesian aquifer. Unconfined Aquifer An aquifer with no protective material above. It is vulnerable to contamination from surface activities. Permeable Layer Portion of aquifer that contains porous rock materials that allow water to penetrate freely. Impermeable Layer Portion of aquifer that contains rock material, or clay layer, that does not allow water to penetrate or pass through easily; often forms the base of unconfined aquifers and the boundaries for confined aquifers. Impermeable Layer Portion of aquifer that contains rock material, or clay layer, that does not allow water to penetrate or pass through easily. Water Movement Down gradient The direction that groundwater flows; similar to down hill for surface water flows Gravity The natural force of attraction exerted by Earth on objects or materials on its surface that tends to draw them down toward its center Injection Wells Deep wells that place water back into the aquifer. Intrusion To force a substance into another, such as seawater into a natural fresh water source. Percolate Downward movement of water through the soil layers Porous The amount of water that can be stored within the aquifer material