adaptive kits for providing water and electrical utilities. The tactical engineer has limited options for providing a water supply; they are in order of ease of provision: drawing water from rivers or lakes, melting ice or snow, or drilling wells. Water supply and treatment is especially challenging in the cold. US Army tactical water purification systems require a winter kit operate between . Water storage may require heating. Water source exploitation may require angering through ice, if shaped charges are not available. The water distribution system can be subject to freezing and clogging from frazil ice. Where chemical treatment is used, it takes longer to dissolve in the treated water. Medicine Three types of cold injury can occur in the theater, hypothermia, trench foot, and frostbite in ascending amount of exposure to cold temperatures. Hypothermia Hypothermia occurs when the body core temperature drops below . Symptoms depend on the temperature and range from shivering and mental confusion to increased risk of the heart stopping. The treatment of mild hypothermia involves warm drinks, warm clothing and physical activity. In those with moderate hypothermia heating blankets and warmed intravenous fluids are recommended. People with moderate or severe hypothermia should be moved gently. In severe hypothermia extracorporeal membrane oxygenation (ECMO) or cardiopulmonary bypass may be useful. In those without a pulse cardiopulmonary resuscitation (CPR) is indicated along with the above measures. Rewarming is typically continued until a person's temperature is greater than . Adequate insulation from clothing is the best way to avoid hypothermia in the field. Trench foot Trench foot is a medical condition caused by prolonged exposure of the feet to damp, unsanitary, and cold conditions at temperatures as warm as for as few as 13 hours. Exposure to these environmental conditions causes deterioration and destruction of the capillaries and leads to morbidity of the surrounding flesh. Affected feet may become numb, affected by erythema (turning red) or cyanosis (turning blue) as a result of poor blood supply, and may begin emanating a decaying odour if the early stages of necrosis (tissue death) set in. As the condition worsens, feet may also begin to swell. Advanced trench foot often involves blisters and open sores, which lead to fungal infections. If left untreated, trench foot usually results in gangrene, which may require amputation. If trench foot is treated properly, complete recovery is normal, though it is marked by severe short-term pain when