question: How is the water in our water supply kept from freezing during winter?
comment: The main supply lines are underground below what is known as the frost line, below which, temperatures don't go below freezing even in the thick of winter. you can look up a map of frost lines. (additional fact: while underground, it also doesn't heat up as much as at surface level during summer. look up ground coupled heat exchangers) Depending on where you live the frost line can be 6-8ft deep for areas like Ontario, a couple feet for areas like Ohio and zero for the warmer places like Orlando (no freezing risk basically). So it depends on how cold the area gets. Once the supply comes out of the ground it's up to your home's heating, insulation and building codes.
passages: STES is also used extensively for the heating of greenhouses. ATES is the kind of storage commonly in use for this application. In summer, the greenhouse is cooled with ground water, pumped from the “cold well” in the aquifer. The water is heated in the process, and is returned to the “warm well” in the aquifer. When the greenhouse needs heat, such as to extend the growing season, water is withdrawn from the warm well, becomes chilled while serving its heating function, and is returned to the cold well. This is a very efficient system of free cooling, which uses only circulation pumps and no heat pumps.
   BULLET::::- Oxford geographer Nick Middleton's television series and accompanying book "Going to Extremes", in which he discusses his visit to this village and describes ways in which inhabitants cope with the extreme cold. Middleton describes how Oymyakon lies between two mountain ranges, trapping cold air between throughout the year. In the winter, once every two days, the village's cattle's herd bull was harnessed between the shafts of a sledge with a big water tank on it and led to the spring. The men broke the ice on the spring, let the bull drink its fill, filled the water tank from the spring, and let the bull pull the tanker sledge back into the warm. The water spring was naturally warm and so stayed liquid below the surface ice.
   Water releases from Dworshak are also timed to benefit Pacific salmon and steelhead migration in the Clearwater, Snake and Columbia Rivers. During late summer through the fall, large volumes of cold water are released through the dam's low level outlets to help cool water in downstream rivers, creating more suitable temperatures for these fish species. These environmental or "flow augmentation" releases significantly increase water levels during the late summer, with up to being released through the dam in August and in September. The temperature of the released water generally varies from .
  
  Section::::Tourism and economy.
   In some regions, for example, Great Britain or California, winter precipitation is often higher than summer precipitation and so the groundwater storage is not fully recharged in summer. Consequently, the water table is lower during the summer. This disparity between the level of the winter and summer water table is known as the "zone of intermittent saturation", wherein the water table will fluctuate in response to climatic conditions.
  
  Section::::Fluctuations.:Long-term fluctuations.
   Warmer winter temperatures cause a decrease in snowpack, which can result in diminished water resources during summer. This is especially important at mid-latitudes and in mountain regions that depend on glacial runoff to replenish their river systems and groundwater supplies, making these areas increasingly vulnerable to water shortages over time; an increase in temperature will initially result in a rapid rise in water melting from glaciers in the summer, followed by a retreat in glaciers and a decrease in the melt and consequently the water supply every year as the size of these glaciers get smaller and smaller.
   For mid-season operation the water is partially cooled by the compressor and partially by the ambient temperatures. The percentage of Free Cooling achieved mid-season is dependent on seasonal temperatures although partial Free Cooling commences when the ambient air temperature is below the process return water temperature. The water is partially cooled through the Free Cooler then flows through the chillers to achieve the required set point temperature.
  
  Section::::Seasons.:Winter operation.
   If the temperatures in an area dip below freezing in winter, the vacuum line is buried below the frost line, in ground that stays unfrozen year-round (as are conventional gravity sewers). Valves, collection pits, intake vents, and control systems need to be designed to keep functioning despite cold, snow and ice. Temperature-monitoring sensors are also standard, so problems can be noticed early.
   Freeze-thaw desalination uses freezing to remove fresh water from salt water. Salt water is sprayed during freezing conditions into a pad where an ice-pile builds up. When seasonal conditions warm, naturally desalinated melt water is recovered. This technique relies on extended periods of natural sub-freezing conditions.
  
  A different freeze-thaw method, not weather dependent and invented by Alexander Zarchin, freezes seawater in a vacuum. Under vacuum conditions the ice, desalinated, is melted and diverted for collection and the salt is collected.
  
  Section::::Methods.:Electrodialysis membrane.
   Many water balance factors depend on the level of the water table, which again depends on some of the water-balance factors. Due to these mutual influences there can be non-linear changes throughout the season. Therefore, the computer program performs daily calculations. For this purpose, the seasonal water-balance factors given with the inpu] are reduced automatically to daily values. The calculated seasonal water-balance factors, as given in the output, are obtained by summations of the daily calculated values. Groundwater levels and soil salinity (the state variables) at the end of the season are found by accumulating the daily changes of water and salt storage.
   BULLET::::- Large-scale thermal storage with water. Large scale STES water storage tanks can be built above ground, insulated, and then covered with soil.
  
  BULLET::::- Horizontal heat exchangers. For small installations, a heat exchanger of corrugated plastic pipe can be shallow-buried in a trench to create a STES.
  
  BULLET::::- Earth-bermed buildings. Stores heat passively in surrounding soil.
  
  BULLET::::- Salt hydrate technology This technology achieves significantly higher storage densities that water-based heat storage. See Thermal energy storage: Salt hydrate technology
  
  Section::::Conferences and organizations.
   Section::::Control.:Mechanical control.
  
  These methods include stabilizing freeze without restricting water flow, such as implementing weirs and ice booms, installing water jets to break up any accumulation that might occur, and using manual labour to rake away the accumulation. This final method is often not preferred because of high labour costs, cold, wet and late night working conditions. Back flushing is another technology that uses the idea of cancelling out the differential pressure caused by the frazil ice accumulation. This technology creates a high pressure on the downstream side of objects to reverse the differential pressure.
  
  Section::::Control.:Thermal control.
   By 400 BC, Persian engineers had mastered the technique of using yakhchāls to create ice in the winter and store it in the summer in the desert. In most yakhchāls, the ice is created by itself during the cold seasons of the year; the water is channeled from the qanat (Iranian aqueduct) to the yakhchāl and it freezes upon resting inside the structure. Usually a wall is also made along an east-west direction close to the yakhchāl and the water is channeled from the north side of the wall so that the shadow of the wall keeps the water cool to make it freeze more quickly. In some yakhchāls, ice is also brought in from nearby mountains for storage or to seed the icing process.
   "Throughout the West, much of the water needed for agriculture, public supplies, and other uses comes from mountain snowpack, which melts in spring and summer and runs off into rivers and fills reservoirs. Over the past 50 years, snow has been melting earlier in the year, and more late-winter precipitation has been falling as rain instead of snow. Thus, water drains from the mountains earlier in the year. In many cases, dams capture the meltwater and retain it for use later in the year. But upstream of these dams, less water is available during droughts for ecosystems, fish, water-based recreation, and landowners who draw water directly from a flowing river".
   The total quantity of water available at any given time is an important consideration. Some human water users have an intermittent need for water. For example, many farms require large quantities of water in the spring, and no water at all in the winter. To supply such a farm with water, a surface water system may require a large storage capacity to collect water throughout the year and release it in a short period of time. Other users have a continuous need for water, such as a power plant that requires water for cooling. To supply such a power plant with water, a surface water system only needs enough storage capacity to fill in when average stream flow is below the power plant's need.
   Section::::Strategies for water features.
  
  Some fountains, such as the Ontario Science Centre FUNtain Hydraulophone and the flame fountain in Nathan Philips Square, are designed to run year-round by virtue of heated water, whereas others require that the water be drained and that all apertures be covered to keep rainwater from entering the fountain and freezing inside. Fountains and other water features are often drained and sealed up so that water inside does not freeze or cause breakage of the pipes in the fountain.
   Many states in the US have experienced water shortages in the past few decades, creating a market for freshwater that could be profitable for Canada. In the south-western US, growing populations and lifestyles that consume large amounts of water have caused most of the aquifers and rivers in the region to be overused. The water in the Oglala Aquifer, which serves much of the west-central US, was used eight times faster in 2001 than the replenishment rate. Demands for this freshwater are expected to increase as the climate warms.
   Water for winter use is drawn from a mountain spring, then treated and stored in storage tanks. Because the permafrost prevents pipelines from being installed underground, residents must manually carry water from the tank. Even with a tank this size, the water supply usually runs out by March, washeteria is closed and residents must melt their drinking water from snow and ice.
   If the other renewable alternatives are too warm during the summer or too expensive, cold storage can be investigated. In large scale applications underground and snow storage are the most likely alternatives. In an underground storage the winter cold is heat exchanged from the air and loaded into the bedrock or an aquifer by one or more bore holes. In a snow storage frozen water (snow and/or ice) is saved in some kind of storage (pile, pit, cavern etc.). The cold is utilized by pumping melt water to the cooling object, directly in a district cooling system or indirect by a heat exchanger. The lukewarm melt water is then pumped back to the snow where it gets cooled and mixed with new melt water. Snow cooling works as a single cold source but can also be used for peak cooling since there is no relevant cooling limit. In Sweden there is one snow cooling plant in Sundsvall, built and owned by the county. The cooling load in Sundsvall is about 2000 kW (570 tons of refrigeration) and 1500 MWh/year.
   Water is one of the most precious and important natural assets in the Okanagan Basin. Even though the Basin is endowed with several large lakes, the supply of clean, reliable water is inherently limited by the semi-arid to arid climate, which brings minimal precipitation and high evaporation and evapotranspiration rates. In fact, according to Statistics Canada the Okanagan Basin has the lowest, per capita availability of fresh water in Canada. Water shortages have already occurred in some areas of the Basin, and are expected to occur more widely and frequently in the future.
  
  Section::::Powers.
   In 2009, a district cooling system was installed in the United Nations area of Geneva, drawing water from Lake Geneva. The system is in the process of being expanded to other areas of Geneva.
  
  Section::::Applications.:Canada.
   The significant feature of a thermosyphon is that it is passive and does not require any external power to operate. During the winter, the air is colder than the ground around the supports. The liquid ammonia at the bottom of the thermosyphon is vaporized by heat absorbed from the ground, cooling the surrounding permafrost and lowering its temperature. During the summer, the thermosyphons stop operating, since there is no liquid ammonia available at the top of the heat pipe, but the extreme cooling during the winter allows the ground to remain frozen.
   Ski resorts have a strong interest in producing snow, even when the ambient temperature is as high as 20 °C. The dimensions and power expenditure of known snow-production equipment depend on humidity and wind conditions. This snow-making equipment is based on the freezing of water droplets which are sprayed into air before they reach the ground surface, and requires an ambient temperature lower than −4 °C.
   At the end of December, thousands of homes and businesses in Northern Ireland and Wales were without water as melting snow and ice revealed many burst pipes. Northern Ireland Water said it was alternating supplies from reservoirs in order to help alleviate the crisis in which some properties had been without supplies since before Christmas.
  
  Section::::Timeline.:January 2011.
   In winter, when outdoor temperatures are low enough, the water is chilled solely by the Free Cooling coil. This allows the chillers’ compressors to stop operating, saving significant amounts of energy. The only electrical power used in winter operation is for fan operation. This can be achieved once the ambient air temperature is to below the process supply water temperature.
  
  Section::::Limitations.
   Regardless of who provides it, the chilled water (between 4° and 7°C (39-44 °F)) is pumped through an air handler, which captures the heat from the air, then disperses the air throughout the area to be cooled.
  
  Section::::Site generated.
  