Pizza Girl: This is even worse than when The Joker poisoned the water supply!
Construction Worker: Or when Scarecrow poisoned the water supply!
Pizza Girl: Or when Killer Croc poisoned the water supply! That's how he died, the poor fool.
Fear of drinking water is a classic paranoia, especially since in medieval times or earlier it could be quite difficult to come by a clean water supply (just imagine what it was like it the days before water filtration and the only river within miles had thousands of people throwing all their waste, including biological wastes, into it upstream) and thus a well could be the center of life for miles around. If anything happened to it or anyone tried to contaminate it, you'd never know until it was too late...
As such, super-villains or government conspiracies putting horrible stuff in the water has been the fodder of fictional plots for years. In other settings, the paranoia is not justified but might still be relevant to the plot. In stories set in modern, developed countries, this trope often employs some Artistic License. The sheer quantity of fluid in most water infrastructures would dilute most added contaminants to virtually nothing, not to mention the various micro-organisms that would absorb the initial damage in many cases, or the security measures water facility equipment has to prevent exactly this kind of tampering. Realistically, achieving this intentionally would require jumping a lot of logistical hurdles (unless one believes in homeopathy, at any rate).
- In Birdy the Mighty, this was Seichiro Hikawa's plan for the people of Tokyo, to turn them into "retro soldiers" by tainting the city's water supply with serum. See here, starting at 4:27.
- Ninja Scroll. A village well is poisoned to make it appear a plague is sweeping through the area — everyone flees leaving the bad guys free to carry out their plans without witnesses.
- In Rurouni Kenshin, Hannya forces Megumi to come with him by threatening to pour a vial of mercury into Kamiya Dojo's well.
- In Snow White with the Red Hair, Shidan manages to do this unintentionally by secretly raising beautiful glowing flowers in a cave that housed a spring in Lyrias. The flowers cause the water to become poisonous.
- A frequent plot of The Joker is to slip Joker venom into Gotham's water supply.
- Deconstructed in one Batman comic, where Bruce deduces Narcosis, the Villain of the Week, won't put his hallucinogen into the water supply, because it's too easy to shut off. Instead, he plots to put it in the milk supply.
- Supreme Power (an Alternate Company Equivalent to the DCU and especially the Justice League) was all too happy to show how terrifying this would be in the spinoff where Nighthawk (the Batman analogue) deals with an Omnicidal Maniac who has developed an always lethal poison and is trying to kill off a major city with it. It gets Deconstructed when Nighthawk points out to the man that the water reclamation plant doesn't connect directly to the reservoir and there are safeguards in place to shut it off automatically if it's contaminated.
- Often used as a plot point in the adventures of Lieutenant Blueberry: one or more characters finally come across a water source after a long trip through the desert... only to find out that the bad guys (or at any rate, someone who does not want to see them come out of the desert alive) have poisoned it by throwing in a dead animal, usually a horse.
- A Captain America arc, during Cap's "The Captain" phase, had Madam Hydra/Viper putting drugs into Washington D.C.'s water supply. What did said drugs do? Turned everyone who drank the water into half-human, half-snake hybrids.
- During the Apocalypse War arc prologue of Judge Dredd, Block Mania, Orlok introduces the Block Mania to the city via the water supply.
- The Moon Kings, a criminal gang fought by the title character in volume one of Moon Knight, plan to extort Chicago by contaminating its water tables with a psychotic/hallucinatory drug. It's noted in-story that Chicagoans actually like and trust their water supply, unlike New Yorkers.
- In Erin Brockovich, PG&E tries to cover up the fact that they were poisoning the groundwater of the town Hinkley, California with Hexavalent Chromium, which resulted in most of the town suffering from illness and cancer.
- The plot of the old action flick Never Too Young To Die involves the hero trying to stop a bad guy played by Gene Simmons from poisoning the water supply.
- Dr. Strangelove's General Jack D. Ripper had a paranoid belief that there is a Communist conspiracy involving water fluoridation which will lead to contamination of everyone's "precious bodily fluids."
- In The Tuxedo, Dietrich Banning (Ritchie Coster) is the owner of a bottled water company. By infecting a swarm of water strider insects with a strain of bacteria that causes water to dehydrate rather than rehydrate the drinker and letting them loose, he plans to render all the water in the world undrinkable except his own, thus increasing its value.
- Although you'd figure that just people would just boil the water, which is a very common method of purification that is extremely reliable.
- Batman Begins had a variation. Scarecrow laced Gotham's water supply with his fear toxin for months, without anyone realizing it. The toxin had no effect in this form. It needed to be absorbed through the lungs to have an effect — the bad guys' ultimate plan was to use a microwave emitter to vaporize Gotham's water supply, thereby exposing the whole city.
- Signs: Bo, the little girl, would start glasses of water then find something wrong with them (such as "It has [her brother's] amoebas in it!") and stop drinking them, leaving them scattered all over the house, half-full. It turned out leaving the glasses all over was Bo being precognitive but unwilling or unable to explain it. Water was harmful to the hostile aliens, one of which had gotten into the house, and when they needed to be able to hurt it, it found itself standing in a room surrounded by partially full water glasses.
- The Norsefire party was implied to have done this in the movie version of V for Vendetta.
- the Soviet tank crew in The Beast of War is shown emptying poison canisters into a well while attacking a village. Later on one of the mujahadeen is killed when he drinks from a poisoned well.
- The Soviets' poisoning of every water source they come across ends up biting them in the butt later, as a Soviet helicopter crew unknowingly drinks from a pond the tank crew had poured cyanide into earlier and all die - before they can radio assistance for the stranded tank.
- An inverted version is mentioned in Contagion. The US government wants to know if they can distribute the cure this way, but is told that it would only dilute it beyond practical effectiveness.
- In The Crazies (2010), the culprit turns out to be a bio-weapon aboard a plane that crashed into the marshes near the town, which are used for drinking and watering crops. When the protagonist finds out about this, he demands that the mayor shut down the water supply, only for the mayor to refuse, claiming that is would devastate the town (given that it's planting season).
- Halfway through Wild Beasts, it is discovered that the animals are acting crazy because there is PCP in city's water supply.
- In Rurouni Kenshin, Kanryu's men flush Megumi out of hiding by pouring rat poison into the village well. She is able to treat everybody who drank the tainted water, but she decides to stop hiding and return to Kanryu's mansion, fearing more attacks on the people.
- In The Men Who Stare at Goats, Bill puts LSD in the water supply of a military camp sending the whole camp on a trip.
- In "The Challenge" (1970 TV movie) a Combat by Champion takes place on a Pacific island. The US combatant poisons all the water sources on the island except one in the hope of ambushing his opponent there.
- Tribesmen of Gor Fantasy Counterpart Culture to arabs/desert dwellers; an outside party causes unrest by masquerading as one of two opposing tribes and attacking the others' oases. At one point they destroy a well, which tells Tarl's best friend of the book that they aren't really tribesmen because no tribesman, no matter how evil, would destroy a well.
- Donald J. Sobol's Secret Agents Four. A criminal organization named Cobra plans to put a drug in the city of Miami's water supply. The drug causes the victim to relive the last 24 hours, rendering them helpless.
- "When the Past Went Away" by Robert Silverberg: Amnesia-inducing drugs are dumped in a city's water supply, leaving everybody in the city with no memory of who they are.
- Defied by Alastor Moody in his first appearance in Harry Potter and the Goblet of Fire: The known paranoid drinks only from his canteen, but it's a subversion as this conveniently allows an impostor to impersonate Moody by taking regular sips of Polyjuice Potion.
- In The First Virtue, part of Star Trek: Stargazer, a fanatical Cordracite poisons her city's water supply in order to escalate a conflict with another race, assuming they'll be blamed.
- In Jingo, there was a man who had poisoned the only well for twenty miles worth of desert, killing five men, seven women, thirteen children, and thirty-one camels (some of them being very valuable camels). This is the source of 71-Hour Ahmed's name. Once he had solid evidence and witness testimony, he executed the poisoner before the customary three days of Sacred Hospitality was up.
- In a Prelude to Dune prequel novel, a group of Harkonnen soldiers manage to capture a young sandworm. Just for fun, they drown it in a hidden water tank near a Fremen village as punishment for hoarding water, knowing that pure Water of Life (the result of an infant worm regurgitating water, poisonous to it) is pure poison. When Liet Kynes later finds the village, most of the villagers are dead, while the rest are delirious and close to death. He puts them out of their misery and then slaughters a whole bunch of Harkonnens.
- Done twice, for different reasons, in Stephen Fry's novel Making History. The first time, they put a water-soluble contraceptive in the well near the house where Adolf Hitler was born, thus preventing his birth. The second time, they put a dead rat in the same well, to prevent people from drinking it, because the world without Hitler turned out to be even worse.
- In Goldfinger, part of the Evil Plan to loot Fort Knox involves killing everyone in the area by poisoning the local town's water supply.
- In the Dirk Pitt Adventures book Sahara, the plot-driving ecological disaster is caused by the Corrupt Corporate Executive's improper disposal of nuclear waste that subsequently leaked into the water supply. At the end of the film, he gets subjected to Laser-Guided Karma - Dirk and Al have him tied down out in the open sun until he sunburns, then trick him into drinking that polluted water. He dies a raving loon.
- Wet Desert: Tracking Down a Terrorist on the Colorado River: When the bomber realizes that the All-American Canal is too heavily guarded for another bombing, he forces its shutdown with a bogus threat of having poisoned the water.
- In The Appeal, this is the basis of the lawsuit that drives the plot.
- In The Wishsong of Shannara, the Mord Wraiths poison Heaven's Well, the source of the Silver River, and the entire Four Lands sickens as a result.
- On the Brimstone episode "Carrier", Stone has to stop a Poisonous Person before she can throw up in the local reservoir.
- Doctor Who:
- In the Highlander: The Series multi-parter about the Horsemen of the Apocalypse, the Big Bad planned to contaminate water supplies with a bioweapon, For the Evulz.
- In Power Rangers Zeo, the Machine Empire tried to contaminate all the Earth's water in order to kill off humanity while at the same time turning it into something they could swim in.
- Played with in an episode of Star Trek: The Next Generation where Data - who has amnesia and doesn't know about his own history or Starfleet - is accused of poisoning a well in the village he's living in, but he's really trying to cure them of radiation poisoning by putting the cure in the drinking water (resorting to subterfuge because the villagers don't trust him enough to take his cure if he offered it openly).
- The Twilight Zone (1959) episode "Black Leather Jackets". A group of aliens is sent to Earth to Kill All Humans by contaminating city water reservoirs with deadly bacteria. They are in the form of teenage human males wearing the eponymous apparel.
- In The X-Files episode "Anasazi", the shadowy organization puts LSD into Mulder's water supply, causing erratic behavior that discredits both him and the case he is currently following. And since it wasn't just Mulder's water supply, but his entire apartment building's, it also caused at least one murder there.
- In Merlin, Nimueh conjured up an Afanc and deposited it into Camelon's water supply.
- An episode of NUMB3RS involves a terrorist plot to put sarin gas into the Los Angeles water main. Not only would this kill anyone drinking the water but also anyone taking a shower, doing the dishes, or being in the vicinity of sprinklers.
- In Batman, The Joker turns the Gotham City water reservoir into strawberry jelly (That tastes like axle grease). As the Dynamic Duo works to undo this, Batman notes to Robin that the situation is affecting more than just the drinking water supply, if there was a fire while the water is in that state, the Fire Department would not be able to put it out.
- The first episode of The Professionals ("Private Madness Public Danger") had a chemical expert threatening to contaminate London's water sources with a concentrated hallucinogenic drug unless his political demands were met. He starts with a few drops in the coffee dispenser of a chemical company, a hypodermic in a beer keg at a pub, and plans to disperse a gallon of ADX in a city reservoir.
- In the "Lethal Weapon 5" episode of It's Always Sunny in Philadelphia, Dennis and Mac star as Murtagh and Riggs investigating a Native American casino's involvement in "tainted tap water".
- In season two of The Shannara Chronicles, this turns out to be the Warlock Lord's plan; putting his blood in Heaven's Well, and thereby the Silver Lake and from there the whole water table of the Four Lands, turning everyone who drinks it into zombies under his control.
- In the pilot episode of Blake's 7, the title character is told to not drink for three days because the Terran Administration is putting emotional suppressants in the water to keep the population docile (later when Blake leaves the Domed City he's encouraged to drink some Cool, Clear Water, but doesn't like the taste). In the final season the Federation invents a drug that stops the production of adrenaline, refining it to such an extent that it can be introduced into the water or air, enabling the easy conquest of entire planets.
- The Illuminati card-game and GURPS module has the "Fiendish Flouridators" as one of it's many conspiracies.
- Paranoia supplement Acute Paranoia, adventure "Outland-ISH". The high Programmer of ISH sector is putting a drug called ZAP! in the water supply for Infrared citizens. It tremendously increases productivity but eventually kills the drinker.
- Magic: The Gathering has Poison the Well and Tainted Well, which can mess with your opponent's lands.
- One short adventure for Ravenloft involved a pair of devils that were poisoning a town's water supply with a toxin that induced hallucinations.
- Poisoning a city's water supply was a potential espionage action in Civilization II. Succeeding reduced the city's population.
- You can do the same in Civilization IV, although instead of reducing the population directly, the city takes a huge "unhealthiness" penalty...which might just reduce the population.
- Dragon Quest VII has Krage/Grondal, whose sole source of water is a single well in the middle of town. Then it gets spiked with a poison that makes everyone believe that they're the Demon Lord/King. Considerable amounts of Stupid Evil antics ensue until your merry band is able to do anything about it.
- Early on in Final Fantasy VI, Kefka does this to the village of Doma in one of the definitive crossings of the Moral Event Horizon in console gaming.
- Micaiah of Fire Emblem: Radiant Dawn rejects this as a tactic to take out a well defended enemy base when it's suggested. Rather than point out the questionable ethics involved, she explains that people would see it as a questionable act, and start to question their motives, maybe turn against them.
- A man in the first level of Half-Life 2 tells you not to drink the bottled water in City 17 because "they put something in it to make you forget".
- Enclave President John Henry Eden in Fallout 3 attempts to convince the player to insert a container of novel Forced Evolutionary Virus into the water supply at Project Purity in an effort to achieve the Enclave's goal of killing everyone in the Capital Wasteland with the slightest degree of mutation. He says that the player character, having been born in a vault, is probably immune to the disease. He's wrong.
- One of the potential side quests in the first Diablo game involves Tristram's water supply being poisoned. When you go into the catacombs and find the spring, killing the monsters around it will turn it back to normal.
- In The Sims Medieval, Spies and Wizards can put potions in the well. Some of them are beneficial, but they can add something like Vomicious Venom, which makes people throw up, or a sleeping potion.
- One potential chain of events in The Yawhg involves a potion getting dumped into the water, leading to horrifying mutations. A seperate Event Flag deals with a leech infestation. These events can get triggered in the same game, resulting in mutant leeches.
- Just in case you thought you could get away with not taking your Joy in Wellington Wells, the water supply appears to have been laced with the medication. And, of course, you have to take a drink sometime...
- In Kult: Heretic Kingdoms, one of Alita's tasks is to go and stop some Taymurian shamans who are contaminating a river as part of their campaign against the army of Corwenth.
- In Batman: Arkham Asylum, Scarecrow threatens to flood the Gotham river with his toxins and Joker pollutes the water flow to flood it with Titan.
- A side quest in Final Fantasy XIV has someone suspect that a farmer's paddyfield is tainted with something due to the smell. You find out that a plant monster contaminated the water source, which was seeping into the fields and also likely contaminated the food being grown.
- In a Dr. Horrible's Sing-Along Blog prequel comic, the Evil League of Evil takes advantage of the city's superheroes going on vacation to try and poison the city's water supply. When Super Zero Johnny Snow thwarts them by freezing the entire water supply, they decide that's actually good enough and head back to their HQ.
- And the song "My Eyes" has Dr. Horrible contemplating whether or not to do this. "Any dolt with half a brain/Can see that humankind has gone insane/To the point where I don't know if I'll upset the status quo/If I throw poison in the water main."
- Holy Musical B@man! uses this, with a small parody of its use in Batman comics. When Sweet Tooth announces his plan to poison the water supply, several people comment about the how it's worse than the last couple times a supervillain poisoned Gotham's water supply.
Construction Worker: That nutjob Sweet Tooth is gonna poison the water supply!
Pizza Girl: This is even worse than when The Joker poisoned the water supply!
Construction Worker: Or when Scarecrow poisoned the water supply!
Pizza Girl: Or when Killer Croc poisoned the water supply! That's how he died, the poor fool.
- In Darkwing Duck, "Dry Hard" The Liquidator started out as an unscrupulous bottled water magnate who was contaminating the competitor's water in order to corner the market. He fell in a vat of his own poison and became a liquid being who could control all water.
- Spider-Man and His Amazing Friends: The Green Goblin had a plot to put goblin formula in New York City's water supply, goblinizing the whole population.
- SpongeBob SquarePants: Ultimately averted when Bubble Buddy wreaks havoc on Bikini Bottom.
Tom: He poisoned our water supply, burned our crops, and delivered a plague unto our houses!Townspeople: He DID?!?Tom: No, but are we gonna sit around and wait till he does?!?
- In The Simpsons, Homer says that Shelbyville vowed to spike Springfield's water supply in revenge for Springfield burning down their city hall, but "they don't have the guts." Three guesses what happens to Marge next.
- Monster Allergy:
- In one episode, the Gorkas were planning to spike the city's water supply, turning anyone who drank from it into Andro-Gorkas. Zick was able to thwart their scheme by evaporating the tainted water.
- In another episode, this was a side effect of draining the fluids from the Healing Vat Magnacat had been in since his encounter with Bristlebeard the Pirate.
- Heroic version used in Underdog where the titular hero dropped his super energy vitamin pills in all the world's water sources in order to give humanity the strength to fight back against the Mole Men after the villains stole all the food in the world.
- In Action Man (2000), one of Dr. X's plots involved distributing an aggression-inducing formula as an energy drink. He later attempts to up the ante by dumping it in a reservoir.
- Grossology had a particularly disgusting example of this, with bonus points for being unintentional. The villainous Sloppy Joe had taken a trip to the water treatment plant where he was swimming in the water after it had been through the purification process leading several citizens, including main character Abby who prides herself on her strong stomach, to puke their guts out.
- In Freakazoid!, at one point, The Lobe dumps laxatives into the town's reservoir.
- In Medieval Europe, one of the motivations for anti-Semitic violence was that Jews were accused of poisoning the wells used by Christians. This is the ultimate origin of the name of that logical fallacy.
- Tragically (and ironically), there were a number of anti-Semitic riots and lynchings in late 12th Century Britain which ended with Jewish corpses and pieces thereof being dumped down a well, poisoning it after their deaths (most notably after the Clifford's Tower Massacre in York of 1190 AD- and the well they were dumped in supplied one of the richer Christian parts of town...)
- In a campaign in Northern Africa during World War II, the Germans were upset to find a particular branch of Salt the Earth strategy: every oasis they came to had a sign in English stating that the oasis had been poisoned by the British army. When they complained that poisoning water constitutes a war crime, the British pointed out that there was absolutely nothing forbidding putting up false signs.
- And yes, Conspiracy Theorists have accused governments of pulling this since the beginnings of government. We're not going to list them all, because if we did, we'd be here until the Whigs controlled Congress again.
- British statesman Lord Chesterfield wrote in Letters to His Son: "I cannot omit, upon this occasion, telling you that the Eastern emperors at Constantinople (who, as Christians, were obliged at least to seem to favor these expeditions), seeing the immense numbers of the 'Croisez' [crusaders], and fearing that the Western Empire might have some mind to the Eastern Empire too, if it succeeded against the Infidels, as 'l'appetit vient en mangeant'; these Eastern emperors, very honestly, poisoned the waters where the 'Croisez' were to pass, and so destroyed infinite numbers of them." (letter 51)
- It is also undoubtedly true that the Muslims had plugged (not poisoned; they expected to retake the territory eventually) the wells while retreating back to Jerusalem during the First Crusade. By the time the Crusaders took Jerusalem, they had nearly gone mad with thirst.
- In Flint, Michigan, the water supply was changed from the Great Lake to the Flint River, notorious for filth. This caused many people to suffer from lead poisoning, and caused national outrage at Governor Rick Snyder.