Where Does Oklahoma City Water Come From?

An average of 100 million gallons of water are treated and delivered to OKC residents every day. This leads us to wonder, where does Oklahoma City water come from?

There are seven surface reservoir sources where Oklahoma City gets its water. Canton Lake, Lake Hefner, Lake Overholser, Lake Sardis, Lake Draper, McGee Creek, and Lake Atoka.

Oklahoma City is somewhat unique from other cities in that we are considered one of the largest cities in the US by land mass, spanning 620 square miles. There are two water treatment plants in OKC serving over 1.4 million residents, one at Lake Hefner in North Oklahoma City and the other at Lake Stanley Draper in South OKC. Generally, the Hefner treatment plant serves North OKC residents, and the Draper treatment plant serves South Oklahoma City. Of course, there are also many residents who rely on private well water, but for the purposes of this article, we will only discuss where Oklahoma City’s tap water comes from.

Water from the Canton reservoir located in Northwest Oklahoma, flows into the North Canadian River and empties into Overholser and Hefner reservoirs. Lake Hefner gets its water from these three surface water sources.

The Lake Stanley Draper water treatment plant is the largest in the state, with a capacity of 150 million gallons per day. A 100-mile pipeline known as the Atoka pipeline was constructed in 1962, which funnels water from southeast Oklahoma reservoirs – McGee Creek, Atoka Lake, and Sardis Lake – into Lake Draper. An additional 72” pipeline is under construction to run alongside the existing pipeline to meet future water demands. Lake Stanley Draper gets its water from these four surface water sources.

Surface water is as it sounds, water from the surface of the earth. Surface water accumulates in reservoirs along with other contaminants such as runoff from agricultural or industrial waste practices, bacteria from human and animal activity, and stormwater runoff. Essentially, surface water can contain any substance the water comes in contact with, natural or synthetic, as it makes its way from the clouds down to the reservoir. Naturally occurring minerals and also contaminants such as pesticides from lawns, radioactive material, animal waste, and chemicals like those from road deicers can end up in the water.

The two Oklahoma City water treatment plants approach disinfection slightly differently. Lake Hefner uses a combination of ozone and chloramine, rather than chlorine, to disinfect its water supply. The Hefner treatment plant has been renovating its ozone equipment and noted that during the systems downtime customers may notice a stronger odor or taste in the water. Lake Stanley Draper uses chloramines to disinfect its water.

Chloramine is a combination of chlorine and ammonia. It can provide longer-lasting disinfection than chlorine alone, allowing the water to travel greater distances. However, it is also corrosive and can leach metals from such as lead and copper from pipes during its transit. Chloramine remains in the treated water you receive from your tap and is known to affect the taste and odor of the water. Concentrations in water can be found higher the closer you are to the treatment plant. It’s possible it can also have health implications. You can read more about chloramine here.

According to the 2023 consumer confidence report, Oklahoma City meets the EPA guidelines for allowable limits of contaminants in drinking water. However, some may argue these limits set forth by the EPA are too high and outdated as more information becomes available. Additionally, PFAS are just now gaining attention from the EPA, but with regulations not going into effect several years from now. Immunocompromised individuals and those concerned with any level of contaminants in drinking water will want to consider using a reverse osmosis water filtration system.

Below we have outlined contaminants that exceed the EWG’s more stringent guidelines for acceptable levels of contaminants in water. All these contaminants are a result of using disinfectants to treat raw surface water.

Total trihalomethanes make up 4 contaminants that form as byproducts of the water treatment process. Long-term exposure to these contaminants has been linked to cancer, liver damage, kidney damage, and reproductive harm. The total trihalomethanes group includes chloroform, bromodichloromethane, dibromochloromethane, and bromoform.

While OKC’s water supply met the legal limit of 80 ppb, it exceeded EWG’s limit of .15 ppb by 356x. It also exceeded the national and state averages.

Haloacetic acids are also a result of the water treatment process using chlorine to disinfect water. They consist of a group of 9 haloacetic acids that have been linked to cancer and other health complications. Currently the EPA only requires regulation on 5 of the haloacetic acids also known as HAA5.

Oklahoma City exceeded the EWG’s suggested limit of .06 ppb for HAA9 by 635x and HAA5 of .1 ppb by 305x. OKC also tested for levels higher than national and state averages.

Trichloroacetic acid is another contaminant byproduct which occurs during the water treatment process. It has been known to be a skin irritant and, in high doses, can lead to birth defects or cancer. Oklahoma City tested higher than national and state averages and exceeded EWG’s guideline of .1 ppb by 127x.

Bromate is a byproduct of disinfection when source waters containing bromide are treated with ozone. Laboratory studies on animals show it can lead to DNA damage and cancer. The EWG suggests a limit of .1 ppb, which OKC’s municipal water supply exceeded by 22x. OKC also exceeded national and state averages for bromate.

Other contaminants in OKC’s municipal water supply that aren’t a direct result of disinfection include chromium and radium. Chromium is found naturally in the environment; however it is also a byproduct of industrial production. And radium is a radioactive element that can occur naturally or as a result of oil and gas production.

Oklahoma City utilities say they are testing for PFAS ahead of the EPA’s mandatory testing requirements, which will go into effect in 2027 as per the Safe Drinking Water Act. The National Primary Drinking Water Regulation (NPDWR) will require testing and monitoring for 6 PFAS compounds. According to OKC utilities, “Our test results for the PFAS compounds regulated in the NPDWR have been below detectable limits (<4 ppt).”

However, some experts suggest any level of PFAS contamination can be unsafe, and the testing of 6 PFAS compounds, while a great starting point, still omits the many thousands of PFAS yet to be identified. If you aren’t familiar with PFAS, you can learn more about them here.

Yes, Oklahoma City does add fluoride to its water supply. Adding fluoride to the municipal water supply remains a controversial topic. The US Centers for Disease Control as well as the American Dental Association support the use of fluoride, yet a 2024 federal court recently ruled that water fluoridation poses an “unreasonable risk” to children and that the 75-year-old advice may be outdated with a lack of supportive evidence. If fluoridated water is a concern for you and your family, a reverse osmosis system will effectively remove fluoride.

Per the EPA’s The Lead and Copper Rule (LCR), water systems are required to identify and take inventory of lead service lines/pipes and notify consumers of lead exceeding >15 ppb as of October 2024. Per the final rule, water systems must identify and replace all lead- containing service lines within 10 years, beginning in 2027. Meanwhile, the American Academy of Pediatrics recommends children should only consume water with less than < 1 ppb lead.

According to OKC utilities, “As of October 2024, approximately 173 public service lines in Oklahoma City have been identified as lead, representing only .07% of the City’s 254,000 service accounts. Efforts to identify unverified services lines is ongoing.”  Additionally, in its 2023 Consumer Confidence report, tests for lead were <1 ppb.

Oklahoma City utilities also says, “The use of lead materials in plumbing was banned in 1986 under the Federal Safe Drinking Water Act, and while no large pipes (mains) within the City’s distribution system contain lead, some public and private service lines that are made of lead, galvanized steel, or contain lead solder remain in use.”  Therefore, it is our opinion that the only sure way to know whether there is lead in your tap water is to test it, as lead may accumulate after leaving the water treatment facility.

In conclusion, yes, we believe everyone should filter their municipal water to remove disinfectants added during the treatment process along with other contaminants, which can easily be further reduced with a reverse osmosis system or whole house filter.