Abstract
The Ogallala Aquifer is a vital water source that has been sustaining agriculture, drinking water, and other human needs for many years. However, over the past few decades, the depletion and pollution of the Ogallala Aquifer has become a pressing concern. The Ogallala Aquifer located beneath the Great Plains region in the United States. This is one of the largest aquifers in the world. aquifer that encompasses about 174,000 square miles (450,000 square kilometers) of area underneath the Great Plains Region in the United States (McGuire, V.L., 2017).
The water-saturated thickness of the Ogallala aquifer ranges from a few feet to more than 1,000 feet. Its deepest part is 1200 ft. and is generally greater in the Northern Plains. The depth of the water below the surface of the land ranges from almost 400 feet in parts of the north to between 100 and 200 feet throughout much of the south (McGuire, V.L., 2017).
The regions overlying the Ogallala Aquifer are some of the most productive regions in the United States for ranching livestock, and growing corn, wheat, cotton, and soybeans. Agriculture in the Ogallala Aquifer Region is heavily dependent on irrigation with almost 88% of water withdrawal from the Ogallala aquifer used for crop production (Ajaz et al. 2020). After World War II, the Ogallala Aquifer was heavily exploited for agriculture using center pivot irrigation and automotive engines to extract groundwater. Most of the aquifer-sourced water used for crop irrigation is supplied by center pivot sprinklers (Ajaz et al. 2020). Agricultural activity such as irrigation and fertilizer applications have caused pollution to the ground water.
The Ogallala Aquifer supplies drinking water to millions of people to those who live within the boundaries of the High Plain region. According to the 1990 census 2.3 million people relied on the aquifer system for their drinking water needs. The Aquifer provides water for approximately 27% of the irrigated land in the United States. Over extraction of the ground water is posing severe risks to the aquifer depletion. Recent droughts have only exacerbated declines in groundwater (Zhang et al. 2019) It could take more than 6,000 years to naturally replenish the groundwater once depleted completely (James P. Dobrowolski,2021).
This mini atlas will explore the factors contributing to the depletion and pollution of the aquifer and the potential consequences of these changes. Overall, this project will shed light on the critical importance of this natural resource and the urgent need to take action to protect it.
The Ogallala Aquifer
The Ogallala aquifer is a shallow water table aquifer, and a primary geologic unit of the High Plains of the United States. The aquifer underlies parts of South Dakota, Wyoming, Nebraska, Colorado, Kansas, New Mexico, Oklahoma, and Texas. It covers approximately an area of 174,000 square miles or 450,000 square kilometers. It is the most important source of water in the central region of the country providing water for household, agriculture, industry, and livestock.
Map 1 : Ogallala Aquifer Location
Ogallala aquifer is primarily a water table (unconfined) aquifer (McGuire 2017). The Ogallala was formed over million years during the Pliocene epoch the southern Rocky Mountains were still tectonically active (Gustavson, T. C, Winkler, D. A. (1988)). Groundwater within the Ogallala generally flows from west to east at an average rate of a foot per day (Gutentag et al 1984) All recharge for the Ogalla Aquifer comes from rainwater and snowmelts. Since the High Plains are mostly dry, there isn't much recharge. Recharge depends on how much rain falls, what kind of soil is there, and what kind of plants are there. The Ogallala aquifer has a capacity of approximately three billion acre-feet, which is equivalent to a million billion gallons or 1,000,000,000,000,000 gallons. This volume of water would be sufficient to provide a 1.5 feet deep water cover for all 50 states in the United States. (earthdate.org)
An aquifer is a geologic formation that contains permeable material and is saturated with water. Confined Aquifer is confined between two layers of confining material, which could be clay or other types of impermeable rocks. An unconfined aquifer, also called a water table aquifer, is an aquifer that is not separated from the ground surface by a confining layer, and it is open to atmosphere and all surface waterinputs (USGS).
Map
Significant depletion has occurred everywhere except for the northern part of the aquifer: this is because the northern region is located in a somewhat less arid climate and is replenished much more by natural precipitation.
The High Plains are a grain-growing region of immense proportions. Farmers have been using water from the Ogallala Aquifer to irrigate their crops. Due to the growing population, the demand for grain products increased, which is why more and more fields are being cultivated. The agricultural demands for Ogallala water in the region are immense, 27% of irrigated land lies over the aquifer, it provides 30% of the Country's groundwater used for irrigation, contains40% of the nation's beef supply, and responsible for $20 million in annual food and fiber production. Every year, dozens of fiber and grain-growing products are produced.
Fertilizers employed in agricultural production is the primary source of nitrate concentration. Since the aquifer is undergoing depletion, these substances will tend to become more concentrated, as it will have a smaller volume of water to absorb the same amounts of contamination. 78% of groundwater samples contains with unsafe level of Nitrate. EPA's maximum contaminant level (MCL) for public drinking water supplies in the United States (U.S.) is 10 mg/L as nitrate-nitrogen [NO3-N].
Conclusion
The Ogallala Aquifer plays a crucial role in irrigating the Great Plains, but its excessive use is causing depletion in a much faster rate than it recharges. If the aquifer is depleted completely it could take up to six thousand years to replenish naturally. To avoid this, there is a need for agricultural innovations that can sustain crop production while saving the Ogallala Aquifer.
Overuse of the aquifer poses a significant threat to the region and those who depend on it. Climate change is further exacerbating the issue by reducing the amount of rainfall, making it more challenging to replenish the aquifer. However, farmers can employ new technologies to irrigate their crops more efficiently, thereby reducing the amount of water required.
Finding a solution to this problem requires a concerted effort from farmers, scientists, policymakers, and citizens to develop innovative techniques and promote large-scale change to prevent the Ogallala Aquifer from drying up completely. Failure to act could lead to another Dust Bowl, causing millions of people to go hungry due to a shortage of crops.