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Previously: Tick Borne Disease

Long Distance Hikers and Water Borne Disease

Introduction
There are a number of water borne diseases of interest to US long distance hikers. Most of these diseases cause diarrhea. When more than 3 loose watery stools are produced per day, and hikers are also losing water from heat and exertion, dehydration is a severe, even deadly, threat. Other symptoms may include reduced appetite, nausea, vomiting, fever, malaise, and abdominal bloating and cramping. Most cases resolve with rest and rehydration. Long distance hiking is tough enough without this. Avoid it and you'll have a much nicer hike.

Poor Hygiene
Water borne diseases can also be transmitted in food, sexually, and by poor hygiene. Many people are infected and don't have symptoms, either because they are immune or because the disease is still incubating. Let's say they defecate and while wiping a tiny bit of feces stays on their hand. The necessary amount is less than you can see or smell. Let's say there is no water around so they can't wash up. Later they make some food, and some of the germs get in it. If you share some of the food, you're infected. If you shake their hand, and later wipe your mouth, you're infected. This is called the fecal to oral route. It's totally revolting. To avoid it, we can wash up after defecating, before cooking / eating, and a few more times a day when we cross streams, etcetera. If we observe that other hikers have poor hygiene, we can avoid hanging out with them and wash up after contact.

Treatment Methods
Ultraviolet devices inactivate nucleic acid, leaving the microorganism whole but unable to reproduce. Boiling and chemicals destroy the structure of the microorganism. Chemicals can also interfere with metabolism, biosynthesis, and growth. Filters remove organisms and solids from water, so long as they are not smaller than the pore size.

Germ Colonies
Because long distance hikers use their water bottles, dishes, filters, etcetera, several times a day for months, they never dry out. It is possible for films of germs to build up in filter elements, inside bottles, in grooves or scratches in dishes, and etcetera. These germ colonies can then reinfect water after it has been treated. An occasional extra thorough washing of all dishes is recommended. Hikers can inspect their bottles for discolored patches or bad smells, and can replace them in towns. If you use juice powders or other sugars in your bottles, they are especially prone to germ colonies. This is a good reason to use inexpensive soft drink bottles for water storage: you can replace your bottles every few weeks for a dollar or two. Filter hoses can also be visually inspected. It's more difficult to know whether a significant population of germs is growing in your filter cartridge. Filters, too, need to be replaced periodically. Filters should be drained and dried before storage so colonies don't form in the damp environment.

Germ Free?
We can never escape all germs. All of the treatment methods discussed reduce the numbers of, but do not eliminate, germs. We hope that if we reduce the germs sufficiently, our immune systems will do their part and keep us healthy.

Viral Diseases
Viruses are small enough that many filters cannot separate them from water.

Hepatitis A
Hepatitis A incubates 7- 42 days, typically about 28, before symptoms appear. Symptoms include fatigue, fever, nausea, appetite loss, jaundice (yellowing of skin or whites of the eyes), dark amber urine, diarrhea, and clay colored feces.

Sufferers should rest, avoid eating fats and drinking alcohol.

Total liver failure is rare, and most people recover without treatment. 10-15% of people have a relapse of symptoms within 6 month of the original event.

An infection confers lifelong immunity. But in Europe and North America, many people have never been exposed and are susceptible. Vaccines are available.

Polyomavirus
JC virus infects the respiratory system, kidneys, or brain.

BK virus causes a mild respiratory infection.

Merkel cell polyomavirus causes Merkel skin cancer.

Most infections produce few or no symptoms and confer immunity to future infections.

Bacterial Diseases

Campylobacteriosis
Symptoms, occurring 1-2 days after infection, include fever (40°C, 104°F), diarrhea, cramps and abdominal pain, and last 2-10 days. Campylobacteriosis usually resolves itself with rest and extra fluids.

Cholera
Cholera is not common in the US because of the availability of potable water and the proper treatment of sewage. It is a much greater concern in international travel. After 12 hours to 5 days, vomiting and diarrhea start. So much fluid is eliminated from both ends that it is fairly clear. 3-5 gallons per day can be lost. This puts you at severe danger of dehydration. Dehydration at this level can cause death. Fluids and electrolytes must be replaced, and antibiotics can be used.

Dysentery
Dysentery is diarrhea with blood, and sometimes puss. Often, it feels as though defecation was incomplete. There are several pathogens, including bacteria, viruses, amoebas, and parasites. Consequently, symptoms and treatments vary. Dysentery is not common on US long distance hikes.

Escherichia coli
E. coli is common in the lower intestines of warm blooded animals, including humans. Most strains are harmless, and benefit hosts by producing Vitamin K₂ and by preventing harmful bacteria from flourishing.

Some serotypes cause diarrhea, intestinal discomfort and urinary tract infections. More rarely, strains can cause blood in urine, can infect blood, and can cause pneumonia.

E. coli is rod shaped, about 2μm long and ¼-1μm in diameter.

Leptospirosis
Leptospirosis can be caught from water contaminated by the urine of an infected animal. Routes of infection include drinking and contact with eyes, mucous membranes, or unhealed wounds.

Leptospirosis has two phases of symptoms. After 4-14 days, fevers, chills, muscle aches, vomiting and headaches occur. This first phase resolves, leaving no symptoms.

Later, the second phase causes meningitis, liver and kidney failure, and jaundice or yellowish skin.

Antibiotic treatment is available.

Swimmers Ear
Swimmers Ear is caused by various bacteria and fungi. Therefore, symptoms and treatments vary. Swelling, earwax, puss, and dead skin can block the ear canal, leading to great pain and hearing loss.

The pathogens enter the outside of the ear from contaminated water. Infection is more likely if the skin of the ear canal has been scratched or damaged by cleaning with cotton swabs or other probes.

Prevention is by avoiding swimming or washing in contaminated water, and by not cleaning the ear with swabs, etcetera.

Treatment is by ear drops containing acids or drying agents, rinsing out discharge, and, depending on the pathogen, medications.

Salmonellosis and Typhoid fever
Salmonellosis symptoms develop after 12-72 hours. Symptoms include diarrhea, fever, vomiting, and abdominal cramps, and last 4-7 days. Most cases resolve without treatment, but severe dehydration can require hospitalization. In some cases, the bacteria crosses from the digestive tract to infect the blood, causing typhoid fever (different than typhus), which can cause death without antibiotic treatment.

Protozoal Diseases

Amoebiasis or Entamoebiasis
The amoeba Entamoeba histolytica can enter the digestive tract and live for years without causing symptoms. Symptoms range from mild diarrhea to dysentery with blood and mucus in feces. If the amoebas enter the bloodstream, they can enter the liver and cause abscesses. Amoebicides are available for treatment.

Cryptosporidiosis
Cryptosporidium can complete its lifecycle within the digestive tract of a single host. In addition to humans, several animals are hosts.

Cryptosporidium cysts may survive in 4°C water up to 18 months. Repeated freeze - thaw cycles progressively kill the cysts.

Cyst Stage
It produces oocysts which are excreted with feces. These cysts are hardy enough to survive in dry conditions and in water sources. The cysts are resistant to many disinfectants, including low concentrations of chlorine. Higher concentrations of chlorine dioxide and ozone kill the cysts. Ultraviolet light kills the cysts at fairly low doses. Boiling water and submicron filtration are also effective. When cysts are consumed with food or water, they excyst in the small intestine infect the intestinal epithelial tissue. Oocysts are spherical or ovoid and 5-6μm in diameter. 2-10 cysts can start an infection.

Cryptosporidiosis incubates for about a week before symptoms start. It causes severe diarrhea, flu like symptoms, loss of appetite, bloating, gas, and nausea. Treatment includes replacing fluids and electrolytes.

Cyclosporiasis
Cyclospora cayetanensis enters the gut, incubates for about a week in the mucosa, and then causes severe watery diarrhea, bloating, fever, stomach cramps, and muscle aches.

Giardiasis
Giardiasis is a parasitic disease caused by the flagellate protozoans Giardia lamblia , G. intestinalis and G. duodenalis. The Giardia organism inhabits the digestive tract of humans, beavers, dogs, cats, horses, cattle, and birds. It is zoonotic, or communicable between humans and animals. It is communicable via drinking water, and fecal-oral routes. Cysts die by desiccation, heating, and continued exposure to feces. Repeated freeze thaw cycles kill Giardia, but they sometimes survive one freeze cycle. Cysts can remain viable for a month in 15–20°C lakes, and 3 months in 10°C streams. Prevention is by water treatment and washing hands before eating, cooking, etcetera.

About 200 million people worldwide are infected, making it a common cause of gastroenteritis. Just one cyst gives a 2% chance of sickness. Symptoms may include loss of appetite, diarrhea, hematuria (blood in urine), loose or watery stool, stomach cramps, upset stomach, vomiting, bloating, and sulphurous flatulence and burping. One to two weeks after infection, symptoms start. Symptoms may wane and reappear cyclically. Most people are asymptomatic; only about a third of infected people exhibit symptoms. Untreated, symptoms may last for six weeks or longer. Antibiotic treatment is available. Giardiasis may cause temporary or permanent lactose intolerance.

Parasites
Although some tapeworms do live in the United States, most of the parasites in the table threaten travelers to tropical countries. Although hikers should be careful around animals and scat, US wilderness waters are relatively safe.

Water Treatment Methods

Ultraviolet Germicidal Irradiation
Introduction
Exposing germs to Short Wave Ultraviolet Light (UV-C) causes changes to their DNA and RNA, thereby disrupting the life processes coded in the nucleic acids, including the ability to reproduce. The earth's atmosphere absorbs most of this wavelength of light: If it didn't, all life forms would have to deal with the toxic effects of UV-C. Steripen® makes several portable UV sterilizers suitable for use by hikers.

Advantage over Chemical Treatment
One advantage of UV water treatment is that no chemicals are added to the water. People who only occasionally use water treatment chemicals are probably not harmed by them. But I often drink 4 or more quarts per day for months at a time. I'd rather not continuously drink something that is designed to kill life forms. Another advantage over chemical treatment is that UV sterilization is independent of temperature (chemicals don't work as well when cold) and PH (Chemicals are designed for neutral water, and hikers just don't know the PH of their source).

Advantage over Filters
Even with regular cleaning, water filters eventually permanently clog. For a long distance hiker, this clog may occur far from any store selling replacement filters or cartridges. This may cause a major interruption in a long distance hike. UV sterilizers have the advantage that the batteries can be replaced or recharged even in very small towns.

A Problem with some UV Sterilizers
There is only one brand of UV water sterilizers suitable for hikers. Some of their devices use two electrodes adjacent to the UV light source to ensure that the light tube is submerged in water while it is illuminated. If it were not immersed, the UV light would do the same damage to the hiker that it is supposed to do to the germs. This safety check is sometimes too rigorous, and will keep the light off even when immersed in water. This renders the device completely useless. While hiking the CDT, I noticed that this problem occurred when there were fossils in the local bedrock. And the device would not sterilize any water for days, perhaps more than a week, while I passed through these types of lands. Perhaps in these ancient seafloors, there is just enough salt to fool the electrical sensor. The water tastes fine, so the salt level is fairly low. So a big disadvantage of UV sterilization is that this device type is unreliable. Other models use an optical rather than electrical sensor. I've never tried them, but they may work better.

Keep Tube Clean
Users of UV devices should keep the light source clean, so that light is not partially blocked by a film of dirt over the element. Also, if the water is turbid, or contains visible dirt, that dirt blocks some of the UV light, and the hiker should consider longer treatment times. Prefiltering through a coffee filter or piece of fabric may reduce the amount of visible dirt it the water, allowing UV treatment to work better.

Dangers of UV
The UV-C produced by handheld water sterilizers can produce sunburn and skin cancer in people. It can cause severe damage to the retina and cornea, causing temporary or permanent vision impairment. It causes damage to some plastics.

Effective UV Wavelengths
UV-C is light with shorter wavelengths than can be seen by humans. Light from 100-300nm acts on thymine, one of the 4 bases from which DNA is made. A wavelength of 2,600Å (260nm) is optimal. Low pressure mercury vapor lamps produce monochromatic radiation at 2,537Å (253.7nm). Medium pressure lamps are polychromatic, or provide a wider range of wavelengths.

Effect on DNA and RNA
In DNA, where two thymine bases are adjacent, UV light may cause a covalent bond to be made between the two thymine bases. This produces thymine dimers, which destroys the ability to use the information stored in the DNA. RNA does not contain thymine, and uracil-uracil and cytosine-cytosine dimers are formed. UV causes other nucleic acid flaws at much lower frequencies.

Effect Varies with Different Germs
Although conclusions from various research projects disagree, it seems that some viruses require hundreds of times more light for deactivation than protozoan cysts such as Giardia and Cryptosporidium, which can be deactivated with 6mJ/cm².

Repair of DNA and RNA
It should be noted that the overall structure of a cell treated with UV remains intact. With the damage to the nucleic acids, reproduction and other processes which copy information from nucleic acids are disrupted. The cells are still present, but cannot function adequately to make you sick. However, cells have some means of repairing DNA and RNA. For example, when light of wavelength 330-500nm (in the visible range) is present, the photo reactivation process may repair the nucleic acids and make the germs viable once again. Repairs without light also occur. Therefore, hikers should consume their water soon after treating it, and not leave treated water out in the sun if possible.

Other UV Water Treatment Uses
Although not particularly relevant to hiker water treatment, in industrial scale water treatment, ultraviolet light at 185nm is used to produce ozone and to oxidize chemicals in water.

UV Light Tube Construction
In the units hikers use, a low pressure mercury vapor lamp produces the UV light. Both the lamp tube and a protective tube shaped like a test tube are made of quartz glass, since quartz is fairly transparent to UV light.

Boiling
Boiling can kill most germs of concern to hikers. At 70°C (158°F), most germs will be killed within 30 minutes. At 85°C (185°F) most will be killed within a few minutes. A few pathogens and their spores, usually not seen in American wilderness waters, will not be killed even at 100°C (212°F), an example is botulism Clostridium botulinum. To truly sterilize water, 118°C (244°F) must be reached, probably by use of a pressure cooker.

Filtering
Filters suitable for hiker use are available. Some remove pathogens down to .2μm, meaning they can remove some large viruses. On the other hand, rather than being ball shaped, some bacteria, such as Leptospira spp. are long skinny strands which can pass through a .2μm filter. Some filters also have an activated carbon element, which removes some chemical contaminants. Other filter elements have iodine coated beads, which kill viruses without releasing much iodine into the drinking water.

Filters themselves can grow fungi, bacteria, etcetera. In normal use, the hoses and filters ingest bacteria, algae, and other food sources for microbes. Weekend backpackers can carefully drain and dry their filters before storing them, thereby limiting the growth of germs. But for a long distance hiker, the filter and hoses are always wet, so germs can grow. Hikers should keep the filters and hoses as dry and clean as possible. Some filters incorporate silver metal particles in the filter material to kill some of these germs.

Chemical Water Treatment
Chlorine, chlorine dioxide, sodium hypochlorite (bleach), and iodine are used to kill germs in water. One concern is that while a few days of this type of treatment is probably not harmful, long distance hikers drink treated water for months at a time, increasing the risks of damage. All water treatment chemicals are more effective with warmer water temperatures. If the treated water is very cold, more chemicals should be added, or the treatment time increased. If water can be treated for a very long time, overnight for example, then less chemicals can be used. Chemical doses or treatment time should be increased for visibly dirty water or surface sources downstream of grazing areas, etcetera. Bottles of water treatment chemicals are small, lightweight, and cost much less than filters and UV sterilizers. I carry chemicals as a backup to my UV sterilizer.

Chlorine Water Treatment
In municipal water systems, water is filtered and monitored for germs. Hikers use much more chemical per quart of water because this careful control is not practical while hiking. Therefore, the bad taste and any health effects are amplified in chlorine based treatments for hikers.

The chlorine based Halzone tablets used during World War II were only effective for a few days after the bottle of tablets was first opened. Therefore, they are no longer available.

Sodium dichloroisocyanurate (NaDCC, C₃Cl₂N₃NaO₃) tablets largely replaced Halzone. The tablets also contain effervescent salts, typically adipic acid and sodium bicarbonate, so that the tablets quickly break down in water and release the active ingredient. Enough tablets are added to the water to reach 10 parts per million (PPM) of chlorine in clean looking water or 20 PPM in turbid water. NaDCC is not effective against Cryptosporidium. It imparts a chlorine taste to the water. NaDCC is sold as MSR Aquatabs® in the US.

Two drops of unscented Liquid Chlorine Bleach (sodium hypochlorite, NaClO) can be added to a quart or liter of clear water. After standing covered for 30-60 minutes to sterilize the water, the container can be left open to allow the chlorine to evaporate and reduce offensive tastes and health effects. I not only find the taste of bleach treated water offensive, but also find that plastic bottles that have contained bleach treated water stink badly enough that I replace them at the next town. Bottled laundry bleach is a 3-8% aqueous solution. Some of the bleach evaporates from the solution over time. When bleach kills germs by oxidation, it produces small quantities of potentially poisonous and carcinogenic chemicals like chloroform, CHCl₃.

Chlorine Bleach Tablets are more stable over time than liquid bleach.

Chlorine Dioxide, ClO₂, is sold in tablet form by Potable Aqua® and in a two part liquid form by Aquamira®. Chlorine dioxide does not release free chlorine, so it does not smell like chlorine and it does not form chlorinated molecules. It works over a wide PH range. It releases free oxygen which oxidizes vital parts of germs.

Silver ion/chlorine dioxide tablets or droplets leave less taste and smell in the water than other iodine and chlorine treatments. However, 30 minutes to 4 hours are required for treatment. A concern is that the silver may accumulate in body tissues and result in argyria - a permanent blue-grey coloring of the skin, eyes, and mucous membranes. The silver makes the treatment more expensive than other options.

Iodine Water Treatment
Iodine is effective against many water borne germs. Its effectiveness against Giardia cysts in very cold water is marginal. Warming the water above 20°C (68°F) before treatment makes iodine more effective against Giardia.

Tetraglycine hydroperiodide (C₈H₁₄N₄O₅⋅HIO₄) Iodine Tablets are sold in small glass bottles. The pills are added to water and may take a while to dissolve in cold water. Shaking the water containers helps to dissolve the iodine. After the pills dissolve, warm clear water should be disinfected in about a half hour. Cold or dirty water requires longer treatment times.

Potable Aqua® iodine tablets contain TGHP. Each tablet releases 8 milligrams of titratable iodine. 1 milligram in one liter of water is one part per million, so the recommended dose of 16 ppm is reached with 2 tablets per liter or quart. Potable Aqua® is not effective against Cryptosporidium cysts.

So long as iodine pills are stored closed in the glass bottle they came in, they should last indefinitely. However, if the bottle is left open, the iodine can sublimate out of the tablets, making them useless. The bottle should always be opened and closed tightly as quickly as possible to maintain the freshness of the pills. The iodine can pass through plastic bottles and bags, so iodine pills should not be repackaged to save weight.

Although iodine pill treated water can be consumed as is, sometimes these pills are sold as a kit with a second bottle of pills containing Vitamin C (Ascorbic Acid). After the treatment time, the vitamin C pill (white) can be added. Fairly quickly, the brown color of the water and the iodine taste dissipate as the iodine converts to an iodide. Note that if the second pill is added before the treatment time, the iodine concentration is severely reduced and the treatment is ineffective. I have found that if the second pill is added immediately before drinking, the taste is much better than if the water sits for a long time after the second pill is added. As an alternative to using the second pill, adding a drink mix containing Vitamin C would also cause the Iodine to precipitate out.

As an alternative to the tablets, Iodine Crystals are sold in small glass bottles. Polar Pure® is one source. The glass bottle is topped off with water. The water in the bottle becomes saturated with iodine after a long time, or a shorter time with shaking. Depending on the temperature of the iodine solution (which affects the concentration of iodine) and the temperature of the water to be treated, a certain number of capfuls of the iodine saturated water in the glass jar is added to the quarts of water to be treated. The iodine crystals themselves and the saturated solution in the glass bottle may contain a lethal dose of iodine, so take great care when pouring off the iodine solution not to add extra saturated water, or a crystal, to the treated water. Iodine crystals should stay in their glass bottle to keep them from sublimating / evaporating away. Because the bottle is glass and contains water, you should avoid exposing it to freezing temperatures: If the water were to freeze, it could crack the bottle. Since only a tiny amount of the crystalized iodine is used for each dose, the bottle of iodine crystals lasts through many treatments. Iodine crystals have an unlimited shelf life: So long as you can see crystals in the bottle, the iodine is present and useable. If the bottle is left open, the iodine will sublimate away, and the crystals will be gone.

Quality of Water Sources
Stinky Water
Water from natural sources can have a variety of different properties that may or may not be problematic. Water may have foul smells that make it difficult to drink enough to stay hydrated. Water with rotten egg smells (hydrogen sulfide, H₂S) may also cause foul smelling flatulence the following day. Bad smells may indicate biological contamination or may be due to some chemical in the earth it flowed through. Volcanic springs often have high concentrations of hydrogen sulfide and dissolved salts. Activated charcoal filter elements reduce some smells.

Tea Colored Water
Water may contain chemicals that cause it to have a color. In the southeast, for example, many swamps contain great amounts of decaying vegetation which release tannins, which causes the water to appear brown. This water does not necessarily have dirt which can be filtered out, it's just brown like tea or cola (which are brown due to tannins). It's sometimes dark enough that if you hold your hand a inch below the surface, it appears dark red, and your hand is not visible through 2 inches of water. Though the tannic water is not greatly harmful if drunk for a few days, other sources should be sought for long term stays. In the west, some water sources are tinted green or brown.

Salty, Acidic or Basic Water
Water may contain dissolved salts or be acidic or basic (alkaline). These may cause offensive tastes and may inhibit the action of water treatment chemicals. Near such a water source, salts and other chemicals may effloresce. The sand or porous rock along the source will be very wet at the source, and dry some distance away, with a gradient of wetness in between. Close to the drier end of the gradient, cottony, typically white or yellow crystals (effloresence) forms. If you notice effloresence, you will probably be able to taste the chemical in the water. Alkali water sources are often noted on maps and in trail guides. Long ago sea beds, places with shell fossils for example, are likely to be a bit salty. Some ultraviolet water treatment devices don't work properly in these waters: See the UV section above for details.

Turbid or Cloudy Water
The water may have suspended dirt or algae, which makes it appear hazy or cloudy. This turbid water can be cleaned in a filter. However, the life of filters is calculated for clean looking water, and water so turbid you can't see clearly through it will clog the filter much faster than predicted. Water white with glacial flour is especially fast at clogging filters. UV devices may need to treat turbid water longer than clear water because some of the light is absorbed by the turbidity rather than neutralizing germs. Turbid water is likely to have more germs and chemicals, so a higher dose and more treatment time may be required with water treatment chemicals.

Visible Particles
Some water has particles or swimming bug larvea large enough that you can see the individual bits. Here, one can use a coffee filter, bandanna, or other bit of cloth to filter out these large particles or bugs. Germs are small enough that they will pass right through, but without the large contaminants, all the other treatment methods will work better.

Picking Pure Water Sources
Even water that appears crystal clear can have enough germs to cause sickness. When we treat water by whatever method, we can hope to save ourselves from most of the germs. But a small percentage always slips through. It's best to use the purest sources so that the smallest number of germs get into our guts.

Guidebooks, Maps, & Water Reports
Guidebooks, maps, and water reports often mention water sources that are unattractive because they are unreliable, salty, turbid, or whatever. Hikers who are attentive to navigation and read ahead may be able to carry enough water to bypass unattractive sources. Please take notes and contribute to water reports.

Upstream Pollution Sources
Maps also provide clues to help detect contaminated streams. In a mining area, an upstream private land parcel in a largely public land area is likely to be a mining claim. If you cross heavily used dirt roads to the parcel, or the map shows high grade roads to the parcel, active mining is likely, as is runoff from the mine tailings and roads. In a grazing area, an upstream private parcel may be a ranch. It's easier to keep an eye on the livestock when they're nearer to the ranch, so grazing is likely. Any upstream meadow or valley is likely to be leased for grazing. And livestock like to hang out near water, to they're likely to defecate and urinate in and near the stream. At any upstream town or campground, swimming, dirty dishwater, and sewage are likely to contaminate a stream. So examining what's upstream of your creek crossing can give many clues as to the quality of the water.

Abnormal Algae Growth and Silting
In open streams, excessive algae growth, or orange, red or brown algae, can indicate contamination. Abnormal silting may indicate a road or tailing pile upstream is eroding. Comparing the stream's smell, turbidity, particulate load, etcetera, with other local streams may indicate a problem.

Trash by a Stream
Any trash near a stream is an indication that people who are clueless or don't care have visited. These are the same types who might take a dump near a stream. Certainly, any toilet paper near a stream is a huge negative.

Lakes and Ponds on Streams
Lakes and ponds can be guaged by the same methods, but they accumulate silt and particulate matter. This makes them harder to guage, and less attractive as sources. Where still water has easily disturbed silt or algae below and floating oils or particles on the surface, the cleanest water can be taken from intermediate depths by careful adjustment of the floats on your filter intake hose or by closing your water bottle as you plunge it through the surface and opening and filling it at the cleanest water level.

Earthen Livestock Ponds / Tanks
Earthen livestock tanks / ponds often have filthy water, with cattle urinating and defecating in the water, and churning up the mud as they walk in the water. But the water can be surprisingly clean when cattle have been off the range for a while. Paying close attention to where grazing is occurring, and walking out and looking at all the ponds, may lead you to some fairly clean sources. There are often far more ponds than books or maps mention. To find them, look for berms, areas where cattle have trampled away the vegetation, or greener than normal vegetation. Ponds are often built around seeps, so they may hold water even when the area seems dry and few others have water.

After Heavy Rains
After rain and flooding, surface water sources may have more turbidity, visible particles, and germs because water flowed over the surface of the dirt rather than leaching through it. So it may have touched scat piles and flowed into the water source. Or a scat pile may have been washed into the stream. Watch your water sources after rains.

Windmills & Solar Wells
In grazing areas, windmills and solar panels in the middle of nowhere are likely to indicate a water well. Often, cattle drink from the tanks, so they may not be very clean. But if the windmill or solar pump is operating, you may be able to fill your bottle from the clean stream coming from the well. Usually, I trust well water to drink without treatment. You may have to wait for a wind gust or for the sun to come out from behind the clouds for the well to work, but the clean water may be worth the wait. Especially when cattle are standing staring at you, please load up your water and leave so the cattle will get back to eating. Hikers need to keep good relations with ranchers if we are to be welcome at their water sources.

Springs
If springs are near the trail, I like to trace them to their source. If I can see the water flowing from the earth, it appears to be clean, and there's no contamination around, I sometimes trust them to drink without treament.

Water Caches
At water caches, examine the water for any contamination. Some caches have clean, sealed, new water bottles, whereas others are filled at dubious sources. Treat the water if it seems necessary. At very old water caches, chemicals from the plastic bottles may have leached into the water, leaving a chemical taste.

Potable Water Taps
Where natural water sources are few or are dubious in quality or reliability, and there are potable water sources such as spigots, it may be wise to pack and carry a lot of water.

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