The Skinny on Fracking

A hydraulic fracturing drilling rig creating a new well on the Niobara shale formation, one of the most intensively fracked areas in the United States.
Potential Health and Environmental Effects of Hydrofracking in the  Williston Basin, Montana
SHALE@10: A decade of fracking research: What have we learned? --  Wednesday, July 11, 2018 --
Here's How Fracking Causes Water Pollution
Water Concerns in Hydraulic Fracturing (Fracking) Bundle | AIChE
Fracking Fort Berthold Fact Sheet - Honor The Earth

I have written several articles the environment. A list of links have been provided at bottom of this article for your convenience. This article will, however address different aspects on the environment and the planet in general.

Fracking, What is it?

Fracking, also spelled fracing or fraccing, also called hydrofracking, in full hydraulic fracturing, in natural gas and petroleum production, injection of a fluid at high pressure into an underground rock formation in order to open fissures and allow trapped gas or crude oil to flow through a pipe to a wellhead at the surface. Employed in combination with improved techniques for drilling horizontally through selected rock layers, fracking has opened up vast natural gas deposits in the United States and elsewhere. At the same time, the rapid rise of the practice, frequently in regions with no history of intensive oil and gas drilling, has raised concerns over its economic and environmental consequences.

The Rise Of A New Technology

The technology of fracking has been in use since the 1940s, when liquids such as gasoline and crude oil were injected into poorly performing gas and oil wells in the central and southern United States with the aim of increasing their flow rate. Over the following decades, techniques were improved—for instance, treated water became the preferred fracturing medium, and finely graded sand or synthetic materials were adopted as a “proppant” to hold open the fractures. However, fracking did not enter its current modern phase until the 1990s, when the use of new steerable drill bit motors and electronic telemetering equipment allowed operators to direct borehole drilling and monitor the fracturing process with great precision. Shortly after, a market favourable for natural gas began to be created by high crude oil prices and by environmental regulations that discouraged the burning of oil and coal. In response to these conditions, developers began to open up so-called unconventional gas reservoirs—rock formations that previously had been left undeveloped because, under older production methods, they released the gas contained in them too slowly or in too small a quantity to be profitable.

Gas from unconventional deposits includes coal bed methane (gas located in the joints and fractures of coal seams), “tight gas” (gas locked into relatively impermeable sandstone or limestone formations), and shale gas (gas incorporated into dense microporous shales). Fracking has been used to recover all these gas types, but it has been practiced most prominently in recovering shale gas.

Horizontal Drilling

Most gas shales are found in extensive seams hundreds or thousands of metres beneath the surface. These seams can be accessed through conventional vertical drilling, but the most productive method is usually horizontal drilling. In this technique a well is begun in the traditional way, with the auguring of a pilot hole usually some 6 to 15 metres (20 to 50 feet) deep. This is lined with a steel pipe some 40 to 50 cm (16 to 20 inches) in diameter, called the conductor casing, that is cemented into place. From there the borehole is drilled straight down, passing through numerous rock layers that may include contaminable freshwater aquifers used for private wells or municipal water supply. This portion of the borehole is lined with a cemented steel pipe called the surface casing. Depending on production needs or environmental regulations, another pipe, called the intermediate casing, may be cemented inside the surface casing.

At a predetermined “kickoff point” (in some cases above the shale formation, in other cases within it), a steerable drill bit is installed, and the borehole is turned to the horizontal. From there drilling continues within the shale, sometimes for another thousand metres or more. When this lateral section of the well is drilled, the entire borehole is lined with yet another pipe called the production casing. In many operations more than one well can be drilled from a single surface site (or “pad”), or more than one lateral section can radiate from a single borehole.


Once drilling and casing are completed, the production casing down the borehole is perforated by a tool that fires a series of small, aimed explosive charges through the wall of the pipe. At the surface the drilling rig is removed, and the fracking process begins. Typically, a fleet of tanker trucks converges on the pad along with several trailer-mounted hydraulic pumpers, blenders, and chemical-storage tanks, a self-contained control vehicle or trailer packed with electronics, and other equipment.

The amount of fresh water used in fracking a single shale gas well varies greatly, depending on the size of the well and the amount of fracturing that has to be done to release the gas: industry and regulatory sources give figures that range from approximately 7.5 million to 20 million litres (2 million to 5 million gallons)—roughly equivalent to the water contained in three to eight Olympic-size swimming pools. Environmental groups argue that, in new areas where fracking may grow dramatically, such consumption may represent an unsustainable use of the region’s fresh water. In response, the shale gas industry insists that fracturing for shale gas consumes less water per thermal unit than is used in coal and even conventional oil production. The water is obtained from sources determined by the market and regulations—e.g., purchased from the municipal water supply, pumped from local rivers or streams, reused from previous frack jobs. Sometimes it is piped directly to the pad, and often it is stored there in steel tanks or in large, shallow ponds that have been excavated out of the ground and lined with plastic.

Using fresh water, a mixture of liquid and proppant is blended that consists of some 90 percent water, less than 10 percent sand, and 0.5–2 percent chemical additives; these latter include gelling agents, borehole-cleaning acids, corrosion-preventing stabilizers, and petroleum-based friction reducers—all combined to produce a “slickwater” judged to be right for the particular job. The precise formulas for these fracturing fluids are well-guarded company secrets, though the types of chemical compounds employed are generally known.

In a series of closely monitored operations, the fluid is pumped down the borehole and through the perforations in the production casing under great pressure, powerful enough to enlarge and prop open existing tiny fissures in the shale. Once fracturing is complete, production tubing is inserted into the well. Gas freed from the fractured rock enters the tubing and flows to the surface, where the fracking equipment is replaced by a network of valves at the wellhead called the “Christmas tree.” Fracking fluid returns along with the gas and in some cases brines from the shale formation. These liquids are diverted to the settling ponds or tanks for further treatment and disposal. A finished production site eventually may be denuded of all previous machinery and structures, leaving little more than the Christmas tree (or trees), connections to a gas pipeline, tanks for storing condensed liquids, and support and maintenance equipment. Unused settling ponds are filled in.

Environmental Concerns

Freshwater contamination

Gas wells are often drilled through or near aquifers, and complaints about polluted well water are not uncommon. One frequently expressed fear, especially in areas where fracking is new, is that the fracturing of rock underground will allow contaminated liquids and liberated shale gas to migrate upward from the shale deposit and into the water table. Industry officials insist, and most environmental officials agree, that this is extremely unlikely. A typical frack job is done at depths of 1,500 to 2,500 metres (5,000 to 8,000 feet). Between the shale deposit and the floor of an aquifer (which is normally found no more than a few hundred metres below the surface) are numerous layers of rock that would prevent the infiltration of gas and liquid—though some scientists believe there is a chance, in some geologic formations, that liberated shale gas may be able to follow existing faults and fractures upward to the water table. A more likely scenario suggested by some scientists might be the diffusion of shale gas through old, disused wells that have not been adequately cased or plugged. One frequently documented cause of local pollution is defective casing in the portion of an active gas well that passes through an aquifer, allowing production gas and liquids to pass into the water supply.

In 2010 Gasland, an American documentary film critical of fracking, created a sensation with its footage of a kitchen faucet spewing flames in Fort Lupton, Colorado. The success of the film (which was nominated for an Academy Award) inspired a number of imitation videos on the Internet. Such events might indeed be traceable to drilling, which on many occasions has disturbed previously unknown pockets of gas located close to aquifers, enabling methane gas to permeate well water in concentrations higher than normal. However, such disturbances can be created by drilling of almost any kind, whether for gas, oil, or even well water. For this reason, industry officials, while conceding that drilling procedures should be held to strict standards, nevertheless insist that explosive conditions almost certainly would not be caused directly by the hydraulic fracturing of shale deposits deep underground.

Wastewater pollution

Drilling and fracking consume large quantities of fresh water, and they return that water in a highly polluted state. Recovered fracturing fluid, or flowback, contains not only the original additives (some of which are carcinogenic if consumed in raised quantities over time) but also salty subsurface brines as well as minerals brought up from the formation that may include toxic elements such as barium and radium. Despite myriad disposal regulations, the handling and transport of contaminated water, additives, and sludge are inevitably punctuated by mishaps and negligence. Occurrences such as leaking pipes, breached settling ponds, and even intentional and illegal discharge into rivers and streams periodically arouse the ire of residents, regulators, and anti-industry activists over the release of pollutants into waterways.

In basins in the southern United States, where oil and gas drilling have been practiced on a large scale for almost a century, recovered fracking water is routinely transported to existing disposal wells and pumped into formations deep underground. In new areas where infrastructure for underground disposal does not exist, the water is commonly brought like any other industrial wastewater to treatment plants. This raises the issue of wastewater disposal. In most cases, treated wastewater is released into surface waters while still containing contaminants at tolerable levels set by local pollution standards. Environmental activists note that many standards do not even address some of the chemicals present in fracking water. As a result, the release of even treated wastewater that included fracking fluids may be endangering life in aquatic ecosystems. Partly in response to environmental regulations, gas producers are developing various methods for treating and reusing flowback from fracking operations.

In the United States the refusal of drilling companies to disclose the formulas of their fracking fluids is a major point of contention. Local and state laws could require drillers to disclose their formulas, but at the federal level fracturing fluid is explicitly exempted from regulation under such laws as the Safe Drinking Water Act of 1974. The gas industry maintains that regulation is unnecessary, since the chemical additives in fracturing fluid are safe and are not injected anywhere near aquifers. Environmentalists, on the other hand, question the gas industry’s motives in refusing to divulge their formulas and insist that the industry will never be trusted so long as it refuses to do so.

The possibility of groundwater contamination from brine and fracturing fluid leakage through old abandoned wells is low. Produced water is managed by underground injectionmunicipal and commercial wastewater treatment and discharge, self-contained systems at well sites or fields, and recycling to fracture future wells. Typically less than half of the produced water used to fracture the formation is recovered.

Methane Leakage

Drilling and hydraulic fracturing have made the United States a major crude oil exporter as of 2019, but leakage of methane, a powerful greenhouse gas, has dramatically increased. There is considerable uncertainty about the scale of methane leakage associated with hydraulic fracturing, and even some evidence that leakage may cancel out the greenhouse gas emissions benefits of natural gas relative to other fossil fuels. For example, a report by Environmental Defense Fund (EDF) highlights this issue, focusing on the leakage rate in Pennsylvania during extensive testing and analysis was found to be approximately 10%, or over five times the reported figures. This leakage rate is considered representative of the hydraulic fracturing industry in the US generally. EDF has recently announced a satellite mission to further locate and measure methane emissions. Research indicates the U.S. oil and gas industry emits 13 million metric tons of methane annually, for a leak rate of 2.3% of all production. The Environmental Protection Agency (EPA), by contrast, estimates the fugitive emission rate at 1.4 percent. Methane is a major greenhouse gas. Its global warming potential is 84 times that of carbon dioxide on a 20-year horizon, and 25 times on a 100-year horizon.In addition to fracking’s global impact, there are harmful effects to those living near extraction sites. A host of ancillary components released at well sites can lead to health problems such as irritation of the eyes, nose, mouth and throat. Local air pollution can aggravate asthma and other respiratory conditions. Regionally, fracking-related processes release nitrogen oxides and volatile organic compounds, forming smog that can deprive workers and local residents of clean air.

Other Environmental Concerns

In addition to air and water pollution, fracking can have long-term effects on the soil and surrounding vegetation. The high salinity of wastewater spills can reduce the soil’s ability to support plant life. In addition, the injection wells used in the storage of hydraulic fracturing wastewater can cause earthquakes.

Seismic activity

The injection of recovered fracking water into underground disposal wells raises another environmental concern: human-induced seismicity. All frack jobs produce vibrations that can be detected by sensitive instruments, but on occasion a larger-than-usual number of small tremors and even light earthquakes of magnitude 4.0 or higher have been recorded in some areas where shale gas is being developed. In some cases this has led to a suspension of fracturing activity. However, a more serious threat, according to geologists, is the underground disposal of huge quantities of drilling and fracking fluid, which may alter pressure balances or even lubricate existing faults in rock formations that are already liable to slip. In some areas of known fault lines, underground disposal has been banned.

The Bottom Line

Even though fracking has the potential to provide more oil and gas resources to consumers, the process of extraction has long-lasting negative impacts on the surrounding environment. Air pollution and water contamination due to the toxic chemicals used in hydraulic fracturing are the greatest concerns within fracking sites, while the need for wastewater disposal and shrinking water supplies are also pressing issues directly related to the procedure.


Environmental concerns such as those outlined above have called increasing attention to the practice of hydraulic fracturing, especially as its use has grown and moved beyond areas where oil and gas exploration has been practiced for generations. Nowhere is this more the case than in the Marcellus Shale, a vast and rich shale gas deposit lying mainly under Pennsylvania but also extending northeast into New York and southwest into Ohio and West Virginia—a region blanketed by the scenic Allegheny Mountains and home to consumer and environmental movements that were well established long before fracking entered the area in the early 2000s. Using records kept by the Pennsylvania Department of Environmental Protection, conservation organizations found that gas drillers in that state had been cited for violations of environmental regulations more than 1,600 times from January 2008 to August 2010. In July 2011 the New York Department of Environmental Conservation (DEC), citing concerns about freshwater use and wastewater disposal, issued a report recommending that horizontal drilling and high-volume hydraulic fracturing be banned anywhere within the watersheds supplying drinking water to New York City and Syracuse. The DEC also recommended that drilling not be allowed within a specified distance of any primary freshwater aquifer and that the purchase and drawing of water for drilling and fracturing be strictly regulated. In 2014 New York Gov. Andrew Cuomo announced a statewide ban on fracking, making New York the first state with proven reserves to ban the practice. North of New York, in Canada the Quebec Ministry of the Environment called for a halt to all fracking operations within the Utica Shale along the St. Lawrence River, pending further investigation of risks to the environment and the population.

In France the test drilling of shale formations in the picturesque southeast part of the country and in the densely populated north around Paris provoked such a strong reaction by environmentalist groups that the government was prompted to put the issue to a vote in parliament. In June 2011 France became the first country in the world to ban the exploration and extraction of gas and oil by hydraulic fracturing.

Meanwhile, in the United States, where the exploitation of shale gas is central to federal energy policy, the debate over fracking has threatened to become polarized between irreconcilable pro-industry and environmental camps, each armed with its own research to support its own arguments. In order to work toward a consensus based on objective, verifiable data, in 2010 Congress directed the U.S. Environmental Protection Agency (EPA) to study “any potential impacts of hydraulic fracturing on drinking water and groundwater.” The following year the EPA decided to conduct case studies of seven specific well sites around the country, from Texas to Pennsylvania to North Dakota. The final report, issued in 2016, found that the various activities in the fracking water cycle can impact drinking water resources under some circumstances. It also acknowledged that the lack of toxicity data on the chemicals added to fracking water was a significant limitation to the assessment of the severity of the impact on drinking water.


Oil and natural gas fracking, on average, uses more than 28 times the water it did 15 years ago, gulping up to 9.6 million gallons of water per well and putting farming and drinking sources at risk in arid states, especially during drought.

The natural gas produced using fracking is often considered a more climate-friendly fuel for electricity generation than coal because burning gas emits fewer greenhouse gases.

Though fracking is used to produce natural gas in less-arid regions such as Pennsylvania, many of the nation’s fracking operations occur in places where water may become scarcer in a warming world, including Texas, the Rocky Mountains and the Great Plains — regions that have been devastated by drought over the last five years.

Energy companies are using more water to frack oil and gas wells because newer technology, which allows them to find oil in more complicated geology, requires it, USGS research geologist and study co-author Mark Engle said.

The amount of water fracking uses is small compared to the water needs of farming or power plant cooling, but in areas that have little water to begin with, fracking can strain water supplies. In the addendum section I compared the use of water for Fracking Natural gas, water used in oil wells and how much is used in farming. Farming takes a lot more water than for the drilling of fossil fuels. However, more of the water is recoverable from farming. However there seems to be more contamination of both groundwater, rivers and streams than from oil and gas drilling. Because the oil and gas wells are below the fresh water aquifers. So pollution seems to be less of issue than the increased consumption of water. The problem is that we only have a finite amount of water available, each new demand for its use stretches those resources to near breaking points. Just like in my article of Co2 emissions, nature produces more CO2 than do humans, but that addition also strains what our earth can absorb. So it seems to me that salt water use should be considered for these wells. Or at the very least use it for farming. California has one of the highest uses for water for agriculture and Texas also uses a large amount of water. Both states have easy access to salt water. So they would be viable options for salt water purification. Just these 2 states use 22.1% of the water for agriculture. so the other 48 states use the other 77.9% of the water. Our biggest problem in this world is that we have enough resources, they are just poorly distributed and they are in many cases in forms that have to be converted to use. Continents like South America and Africa have incredibly long coastlines. Many of the countries in the these continents have sever water shortages. They just don’t have the resources to take advantage of all this water.

So, as far as I can ascertain, fracking is not the environmental bain that it is made out to be. Agriculture actually has a greater impact on the environment and the our fresh water. We just have to be more judicious in the use of our resources.

Resources:, ” Fracking,” By Britannica editors;, “Fracking,” By Wikipedia editors;, “What Are the Effects of Fracking on the Environment?” By Melissa Horton;, “Study: Water Use Skyrockets as Fracking Expands,” By Bobby Magill;, “How much water does U.S. fracking really use?”;, “The key ingredient in oil drilling? Water,” By Andrew Wineke;, “”agricultural Contaminants;”


Fracturing fluids

he main purposes of fracturing fluid are to extend fractures, add lubrication, change gel strength, and to carry proppant into the formation. There are two methods of transporting proppant in the fluid – high-rate and high-viscosity. High-viscosity fracturing tends to cause large dominant fractures, while high-rate (slickwater) fracturing causes small spread-out micro-fractures.

Water-soluble gelling agents (such as guar gum) increase viscosity and efficiently deliver proppant into the formation.Example of high pressure manifold combining pump flows before injection into well

Fluid is typically a slurry of water, proppant, and chemical additives. Additionally, gels, foams, and compressed gases, including nitrogencarbon dioxide and air can be injected. Typically, 90% of the fluid is water and 9.5% is sand with chemical additives accounting to about 0.5%. However, fracturing fluids have been developed using liquefied petroleum gas (LPG) and propane in which water is unnecessary.

The proppant is a granular material that prevents the created fractures from closing after the fracturing treatment. Types of proppant include silica sand, resin-coated sand, bauxite, and man-made ceramics. The choice of proppant depends on the type of permeability or grain strength needed. In some formations, where the pressure is great enough to crush grains of natural silica sand, higher-strength proppants such as bauxite or ceramics may be used. The most commonly used proppant is silica sand, though proppants of uniform size and shape, such as a ceramic proppant, are believed to be more effective. USGS map of water use from hydraulic fracturing between 2011 and 2014. One cubic meter of water is 264.172 gallons.

The fracturing fluid varies depending on fracturing type desired, and the conditions of specific wells being fractured, and water characteristics. The fluid can be gel, foam, or slickwater-based. Fluid choices are tradeoffs: more viscous fluids, such as gels, are better at keeping proppant in suspension; while less-viscous and lower-friction fluids, such as slickwater, allow fluid to be pumped at higher rates, to create fractures farther out from the wellbore. Important material properties of the fluid include viscositypH, various rheological factors, and others.

Water is mixed with sand and chemicals to create hydraulic fracturing fluid. Approximately 40,000 gallons of chemicals are used per fracturing. A typical fracture treatment uses between 3 and 12 additive chemicals. Although there may be unconventional fracturing fluids, typical chemical additives can include one or more of the following:

The most common chemical used for hydraulic fracturing in the United States in 2005–2009 was methanol, while some other most widely used chemicals were isopropyl alcohol2-butoxyethanol, and ethylene glycol.

Typical fluid types are:

For slickwater fluids the use of sweeps is common. Sweeps are temporary reductions in the proppant concentration, which help ensure that the well is not overwhelmed with proppant. As the fracturing process proceeds, viscosity-reducing agents such as oxidizers and enzyme breakers are sometimes added to the fracturing fluid to deactivate the gelling agents and encourage flowback. Such oxidizers react with and break down the gel, reducing the fluid’s viscosity and ensuring that no proppant is pulled from the formation. An enzyme acts as a catalyst for breaking down the gel. Sometimes pH modifiers are used to break down the crosslink at the end of a hydraulic fracturing job, since many require a pH buffer system to stay viscous. At the end of the job, the well is commonly flushed with water under pressure (sometimes blended with a friction reducing chemical.) Some (but not all) injected fluid is recovered. This fluid is managed by several methods, including underground injection control, treatment, discharge, recycling, and temporary storage in pits or containers. New technology is continually developing to better handle waste water and improve re-usability.

How much water does U.S. fracking really use?

Energy companies used nearly 250 billion gallons of water to extract unconventional shale gas and oil from hydraulically fractured wells in the United States between 2005 and 2014, a new Duke University study finds.

During the same period, the fracked wells generated about 210 billion gallons of wastewater.

Large though those numbers seem, the study calculates that the water used in fracking makes up less than 1 percent of total industrial water use nationwide.

While fracking an unconventional shale gas or oil well takes much more water than drilling a conventional oil or gas well, the study finds that compared to other energy extraction methods, fracking is less water-intensive in the long run.

Underground coal and uranium mining, and oil recovery enhancement extraction use between two-and-a-half to 13 times more water per unit of energy produced.

The study also found that fracked oil wells generate about half of a barrel of wastewater for each barrel of oil, while conventional oil wells on land generate more than three barrels of wastewater for each barrel of oil.

“Water use and wastewater production are two of the chief environmental concerns voiced about hydraulic fracturing,” said Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment. “Yet until now we’ve had only a fragmented and incomplete understanding of how much water is actually being used, and how much wastewater is being produced.”

Added Vengosh: “Our new study, which integrates data from multiple government and industry sources, provides the first comprehensive assessment of fracking’s total water footprint, both nationally and for each of the 10 major U.S. shale gas or tight oil basins.”

Vengosh and Ph.D. student Andrew Kondash published their peer-reviewed findings today (Sept. 15) in the journal Environmental Science & Technology Letters.

“While hydraulic fracturing consumes only a small fraction of the water used in other extraction methods, our analysis highlights the fact that it can still pose serious risks to local water supplies, especially in drought-prone regions such as the Barnett formation in Texas, where exploration and development is rapidly intensifying,” Kondash said. “Drilling a single well can require between 3 to 6 million gallons of water, and thousands of wells are fracked each year. Local water shortages could limit future production.”

Finding ways to treat and dispose of or recycle the large volume of chemical-laden flowback water and brine-laden wastewater that is produced over the lifetime of an unconventional oil or gas well also poses challenges, the researchers noted.

“Given the high levels of contaminants these waters contain, it’s startling that the amount of wastewater being produced from hydraulic fracturing in the United States is nearly on the same level as the amount of water used to frack the wells in the first place,” Vengosh said. “Yet the quality of the water that comes out is very much different from the water the goes in.”

The key ingredient in oil drilling? Water

They say oil and water don’t mix, but when it comes to oil and gas drilling, water and oil are practically joined at the hip.

It takes millions of gallons of water to drill a well. Water is the “hydraulic” in the hydraulic fracturing process used to release oil and gas deposits. Disposing of wastewater is a costly challenge for drillers. And, at every step along the way, preventing groundwater contamination is the paramount concern for inspectors and regulators.

All of these issues are hitting like a flash flood for Colorado Springs and El Paso County. Oil and gas drillers have been expanding their exploration south in recent years from Weld County, the focus of eastern Colorado’s oil country. A recent Colorado State University study showed that drilling and hydraulically fracturing a vertical well — as Ultra’s initial exploratory wells will be — takes an average of 387,000 gallons of water. Production wells branch off the bottom of a vertical well and run laterally to access sections of oil-bearing rock up to 5,000 feet away. They take an average of 2.8 million gallons of water — 50 times what an average home in Colorado Springs uses in a year. In Greeley, where there are about 500 oil wells inside the city limits, drillers hook up to fire hydrants through a meter and pay a special use rate that nets the city a tidy profit on the sale. In 2011, the city sold 491 million gallons of water to oil companies and earned $1.6 million. Statewide, the Colorado Oil and Gas Conservation Commission projects that oil and gas drilling will use 5.25 billion gallons of water in 2012. On the one hand, that’s a huge amount of water — that average home in Colorado Springs uses 98,736 gallons a year. However, compared to other large water users in the state, it’s small potatoes. Agriculture is far and away the largest water user, accounting for roughly 4.56 trillion gallons a year, 85 percent of all water use in the state.—Breaking rocks a mile deep.

Agricultural Contaminants

About 40 percent of the land in the United States is used for agriculture, and agriculture supplies a major part of the our food, feed, and fiber needs. Agricultural chemicals move into and through every component of the hydrologic system, including air, soil, soil water, streams, wetlands, and groundwater.

Agricultural contaminants can impair the quality of surface water and groundwater. Fertilizers and pesticides don’t remain stationary on the landscape where they are applied; runoff and infiltration transport these contaminants into local streams, rives, and groundwater. Additionally, when land is converted to agricultural use, it is modified to be optimized for agricultural production. Oftentimes these modifications have unintended environmental impacts on receiving waters and their ecosystems, including changes in water quality and quantity.

Agriculture is the leading source of impairments in the Nation’s rivers and lakes. About a half million tons of pesticides, 12 million tons of nitrogen, and 4 million tons of phosphorus fertilizer are applied annually to crops in the continental United States.

Pesticides are widespread in surface water and groundwater across the United States. For example, at least one pesticide was found in about 94 percent of water samples and in more than 90 percent of fish samples taken from streams across the Nation, and in nearly 60 percent of shallow wells sampled.

Transport of excess nutrients is influenced by agricultural practices, such as methods of tillage and drainage, and the timing of application and runoff events like storms and snowmelt. Farmers may leave the soil surface undisturbed from harvest to planting (referred to as “no-till”), and may plant and maintain buffer strips around fields and streams. They may also time fertilizer and manure application to maximize uptake and avoid precipitation events. Use of drip irrigation in lieu of furrow irrigation decreases the amount of water lost to ditches or evaporation, and allows better control of the amounts of pesticides and nutrients added to irrigation water. The USGS studies the amount of nutrients transported off agricultural fields, the effects excess nutrients have on downstream receiving waters, and the effectiveness of on-farm conservations practices that try to reduce the amount of nutrient transport due to runoff.

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