question: If the water cycle is a closed system, why does it matter that a pound of beef takes 1800 gallons of water to produce?
comment: It's a matter of clean/potable water. The water used to produce beef must be potable, and ends up non-potable, so that puts an enormous strain on the availability of clean water in an area. Yes, it does go back into the water cycle, but it takes a long while for it to make its way back to a drinkable state.
passages: Also, the high virtual water use figures associated with meat production do not necessarily imply reduction of water use if food crops are produced, instead of livestock. For example, some grazing lands are unsuitable for food crop production, so that evapotranspirational water use would continue on land vacated by livestock, while additional water would be needed for crops to provide substituting food from lands elsewhere, and additional water would also be needed to produce substitutes for the non-food products of livestock. (In the US, Land Capability Classes V, VI and VII contain soils unsuited for cultivation, much of which is suitable for grazing. Of non-federal land in the US, about 43 percent is classed as unsuitable for cultivation.)
   However, virtual water use data, such as those shown in the table, are often unrelated to environmental impacts of water use. For example, in a high-rainfall area, if similar soil infiltration capacity is maintained across different land uses, mm of groundwater recharge and hence sustainability of water use tends to be about the same for food crop production, meat-yielding livestock production, and saddle horse production, although virtual water use per kg of food produced may be several hundred L, several thousand L, and an infinite number of L, respectively. In contrast, in some low-rainfall areas, some livestock production is more sustainable than food crop production, from a water use standpoint, despite higher virtual water use per kg of food produced. Unirrigated land in many water-short areas may support grassland ecosystems in perpetuity, and thus may be able to support well-managed production of grazing cattle or sheep with a sustainable level of water use, whereas more water-demanding food crops would be unsustainable in the long run due to inadequate surface water supplies and groundwater recharge to sustain a high level of irrigation. Such considerations are important on much rangeland in western North America and elsewhere that can support cow-calf operations, backgrounding of stocker cattle, and sheep flocks. In the US, withdrawn surface water and groundwater use for crop irrigation exceeds that for livestock by about a ratio of 60:1.
   Certain agricultural demands may increase more than others with an increasingly wealthier global population, and meat is one commodity expected to double global food demand by 2050, which directly affects the global supply of fresh water. Cows need water to drink, more if the temperature is high and humidity is low, and more if the production system the cow is in is extensive, since finding food takes more effort. Water is needed in processing of the meat, and also in the production of feed for the livestock. Manure can contaminate bodies of freshwater, and slaughterhouses, depending on how well they are managed, contribute waste such as blood, fat, hair, and other bodily contents to supplies of fresh water.
   Considerable water use is associated with meat production, mostly because of water used in production of vegetation that provides feed. There are several published estimates of water use associated with livestock and meat production, but the amount of water use assignable to such production is seldom estimated. For example, “green water” use is evapotranspirational use of soil water that has been provided directly by precipitation; and “green water” has been estimated to account for 94% of global beef cattle production's “water footprint”, and on rangeland, as much as 99.5% of the water use associated with beef production is “green water”.
   Commonly, CAFO wastewater and manure nutrients are applied to land at agronomic rates for use by forages or crops, and it is often assumed that various constituents of wastewater and manure, e.g. organic contaminants and pathogens, will be retained, inactivated or degraded on the land with application at such rates; however, additional evidence is needed to test reliability of such assumptions
   Irrigation accounts for about 37 percent of US withdrawn freshwater use, and groundwater provides about 42 percent of US irrigation water. Irrigation water applied in production of livestock feed and forage has been estimated to account for about 9 percent of withdrawn freshwater use in the United States. Groundwater depletion is a concern in some areas because of sustainability issues (and in some cases, land subsidence and/or saltwater intrusion). A particularly important North American example where depletion is occurring involves the High Plains (Ogallala) Aquifer, which underlies about 174,000 square miles in parts of eight states, and supplies 30 percent of the groundwater withdrawn for irrigation in the US. Some irrigated livestock feed production is not hydrologically sustainable in the long run because of aquifer depletion. However, rainfed agriculture, which cannot deplete its water source, produces much of the livestock feed in North America. Corn (maize) is of particular interest, accounting for about 91.8 percent of the grain fed to US livestock and poultry in 2010. About 14 percent of US corn-for grain land is irrigated, accounting for about 17 percent of US corn-for-grain production, and about 13 percent of US irrigation water use, but only about 40 percent of US corn grain is fed to US livestock and poultry. Together, these figures indicate that most production of grain used for US livestock and poultry feed does not deplete water resources and that irrigated production of grain for livestock feed accounts for a small fraction of US irrigation water use. However, where production relies on irrigation from groundwater reserves, water table monitoring is appropriate to provide timely warning if groundwater depletion occurs.
   Section::::Resources.
  
  Virtual water use for livestock production includes water used in producing feed.
   Livestock and meat production have one of the largest water footprints of the agricultural industry. Taking nearly 1,800 gallons of water to produce one pound of beef and 576 gallons for pork. For reference, it only takes about 108 gallons of water to harvest one pound of corn. Livestock production is also one of the most resource intensive agricultural outputs. This is largely due to their large feed conversion ratio. Livestock's large water consumption may also be attributed to the amount of time it takes to raise an animal to slaughter. Again, in contrast to corn, which grows to maturity in about 100 days. This adds an extra 995 days of water to grow cattle. The global "food animal" population is just over 20 billion creatures, with 7+ billion humans, this equates to about 2.85 animals per human.
   Within the agricultural sector, withdrawn water use is for irrigation and for livestock. Whereas all irrigation in the US (including loss in conveyance of irrigation water) is estimated to account for about 38 percent of US withdrawn freshwater use, the irrigation water used for production of livestock feed and forage has been estimated to account for about 9 percent, and other withdrawn freshwater use for the livestock sector (for drinking, washdown of facilities, etc.) is estimated at about 0.7 percent. Because agriculture is a major user of withdrawn water, changes in the magnitude and efficiency of its water use are important. In the US, from 1980 (when agriculture's withdrawn water use peaked) to 2010, there was a 23 percent reduction in agriculture's use of withdrawn water, while US agricultural output increased by 49 percent over that period.
   The beef and dairy industries are the most lucrative branches of the U.S. agricultural industry, however, they are also the most resource intensive. To date, beef is the most popular of the meats; the U.S. alone produced 25.8 billion pounds in 2013. In this same year, 201.2 billion pounds of milk were produced. These cattle are mostly raised in centralized animal feeding operations, or CAFOs. On average, a mature cow will consume anywhere from seven to twenty-four gallons of water a day; cows that are lactating require about twice as much water. The amount of water that cattle may drink in a day also depends upon the temperature. Cattle have a feed conversion ratio of 6:1, for every six pounds of food consumed, the animal should gain one pound. Thus, there is also a substantial "indirect" need for water in order to grow the feed for the livestock. Growing the amount of feed grains necessary for raising livestock accounts for 56 percent of the U.S water consumption. Of a 1,000 pound cow, only 430 pounds make it to the retail markets. This 18 percent loss, creates an even greater demand for cattle, being that CAFOs must make up for this lost profitable weight, by increasing the number of cows that they raise.
   The amount of manure spread onto farm land affects the concentration of nutrients in the soil, water run-off can transport nutrients such as phosphorus or nitrogen into fresh water streams. High volumes of these nutrients can disrupt the natural ecosystems causing algae blooms, etc.
  
  Other common manure issues include:
  
  BULLET::::- Strong odors associated with manure storage lagoons and ponds
  
  BULLET::::- Expensive costs associated with hauling manure
  
  BULLET::::- Increased flies and other insects at farming operation
  
  BULLET::::- Operation expansion requires additional land or higher costs for hauling manure
   Water scarcity is not necessarily a new issue, however, cattle ranchers in America have been cutting herd sizes since the 1950s in efforts to curb water and manufacturing costs. This shift has led to more efficient feeding and health methods, allowing ranchers to harvest more beef per animal. The rising popularity of these CAFOs are creating a larger demand for water, however. Grass-fed or grazing cows consume about twelve percent more water through the ingestion of live plants, than those cows who are fed dried grains.
  
  Section::::Livestock water use.:Poultry and fowl.
   Returning to the cost objective function, it cannot violate any of the operational constraints. Generally this cost is dominated by the energy cost for pumping. “The operational constraints include the standards of customer service, such us: the minimum delivered pressure, in addition to the physical constraints such us the maximum and the minimum water levels in storage tanks to prevent overtopping and emptying respectively.”
   BULLET::::- Concentrated animal feeding operations (CAFOs): The number of CAFOs, often called “factory farms,” is growing. On these farms thousands of animals are raised in a small space. The large amounts of animal wastes/manures from these farms can threaten water supplies. Strict and careful manure management is needed to prevent pathogen and nutrient problems in private wells. Salts from high levels of manures can also pollute ground water.
   California is one of the top five states in water use for livestock. Water withdrawals for livestock use in California were 101-250 million gallons per day in 2010 (0.135-0.344 km per year).
  
  Section::::Uses of water.:Urban/residential.
   Many forms of energy production through fossil fuels are highly polluting in addition to being water intensive, especially extraction from tar sands and shale and extraction through hydraulic fracturing. Further, return flows from power plants to rivers are warmer than the water that was taken in and/or are highly polluted and can consequently compromise other downstream usage, including ecosystems. Conversely, energy is needed for extracting, transporting, distributing and treating water. Energy intensity for accessing a cubic meter of water varies: logically, accessing local surface water requires far less energy than pumping groundwater, reclaiming wastewater or desalinating seawater. Irrigation is more energy intensive than rain-fed agriculture, and drip irrigation is more intensive yet since the water must be pressurized.
   Section::::Livestock water use.:Cattle.
   The livestock sector may be the largest source of water pollution (due to animal wastes, fertilizers, pesticides), and it contributes to emergence of antibiotic resistance. It accounts for over 8% of global human water use. It is by far the biggest cause of land use, as it accounts for nearly 40% of the global land surface. It is a significant driver of biodiversity loss, as it causes deforestation, ocean dead zones, land degradation, pollution, and overfishing.
   Since 2005 increased dairy farming rates of grazing animals have outstripped riparian planting and the ability of some Regional councils to manage and mitigate impacts on the quality of water., and there is some evidence of urea use leading to nitrogen levels in waterways. Horticulture, arable farming and plantation forestry generally have less effect than dairy farming.
   BULLET::::- Rai + Isu + Lca + Ugw = Eva + Era + Osu + Dtr + Dgw, where the linkage factors "Inf", "Per" and "Cap" have disappeared.
  
  Combining all four water balances in steady state gives the overall water balance :
  
  BULLET::::- Rai + Isu + Lca + Iaq = Eva + Era + Osu + Dtr + Wel + Oaq, where the linkage factors "Inf", "Per", "Cap", "Ugw" and "Dgw" have disappeared.
  
  Section::::Specific water balances.:Water table outside transition zone.
   Despite this 3/4th of the 32 pounds (14.52 kg) of feed cattle consume each day will be corn. Cattle weighing 1000 lbs. will drink an average of 41 L a day, and approximately 82 L in hot weather. They need a constant supply of good quality feed and potable water according to the 5 Freedoms of Animal Welfare.
   Manure management is an increasing issue among CAFO livestock operators. Large CAFO operations help sustain the food industry with its production of food sources. The more food produced the more manure that is produced. Manure is often stored and spread onto adjacent farmland since it is rich in nutrients and is a good fertilizer. Since the livestock industry is so important, manure management practices need to be developed to protect the environment – increased government regulations have been put into place.
   According to a report published by the Water Footprint organization in 2010, a single kilogram of beef requires of water; however, the authors also make clear that this is a global average and circumstantial factors determine the amount of water used in beef production.
  
  Section::::Effects on human civilization.:Human uses.:Medical use.
  
  Water for injection is on the World Health Organization's list of essential medicines.
  
  Section::::Distribution in nature.
  
  Section::::Distribution in nature.:In the universe.
   North America has approximately 10 million dairy cows and 76 million hogs. The dairy and hog industries in North America continue to consolidate into larger CAFO operations resulting in an increase in herd size and a decrease in the number of operations. Certain areas of North America are concentrated with dairy and hog operations. For example, California produces the most milk in North America; whereas Iowa is the top hog producer.
  
  Section::::The LWR Manure Treatment System.
   Federal projects can overrule this state system, and this is true for the Colorado-Big Thompson Project (CBT). The CBT Dam is a Bureau of Reclamation irrigation project where a water market has developed, and is based on a proportional rights system. This market has been in operation since the early 1960s, and has well-developed infrastructure to move water within the area of service. There are market prices, brokers, short term rentals and permanent leases of water in this system, and trades within the agricultural sector and between the agricultural and municipal and industrial sectors.
  
presuppositions: Using 1,800 gallons of water to produce a pound of beef has no negative effects. The 1800 galls of water used to produce a pound of beef gets recirculated into more usable water.
corrections: Using so much water to make a pound of beef reduces the amount of clean water available. The 1800 galls of water used to produce a pound of beef goes from a clean state into a non-potable state.
raw_presuppositions: Using 1,800 gallons of water to produce a pound of beef has no negative effects. The 1800 galls of water used to produce a pound of beef gets recirculated into more usable water.
raw_corrections: Using so much water to make a pound of beef reduces the amount of clean water available. The 1800 galls of water used to produce a pound of beef goes from a clean state into a non-potable state.