WATER

Water is the most important liquid on the earth for life .water has many leading features.

• Have high heat capacity (4184 J / Kg K)

• Stay in liquid form in a range of temperatures

• Good solvent.

• Polar liquid.

 For living things staying hydrated is very essential. The composition of water is hydrogen and oxygen in a 2:1 ratio. Water can behave in a liquid state for a huge range of temperatures due to its high heat capacity. The triple point of water is 273.16 K. At this temperature it has all three stages liquid, solid, and gas.

75% of the earth's surface is covered by water. Of that percentage, 97% is saline water, and 3% is fresh water. Freshwater is present in many states as glaciers groundwater and surface water. 69%  present as glaciers and 1% as surface water and the rest 30%  as groundwater. Only 1.2%  of total freshwater is drinkable. 
Access to clean fresh water is one of the biggest global problems in this decade. According to the CDC reports 2 billion people don't have access to safely managed drinking water. Much of drinking water is derived from surface water. In developing countries, groundwater is often preferred because it needs fewer treatments and has a better bacteriological quality which helps to minimize water-borne diseases such as cholera. for drinking water, the world health organization  (WHO) has made guidelines for the concentration limits of dissolved items in water. The concentrations of ions can be reported in many units. mg/l, μg/l, ppm,etc.

Groundwater standards depend on eleven variables. they are,

• Temperature
• EC (Electrical Conductivity)
• pH
• The four major cations (Na⁺ ,K⁺ , Mg⁺², Ca⁺² )
• The four major anions ( Cl^- ,HCO₃^- ,SO₄^2- ,NO₃^-  )

Rivers and lakes are surface water sources. They are the most polluted sources because people tend to discard waste. For agriculture, electricity production, and daily uses such as drinking, bathing, etc surface water is used. Access to the groundwater is quite difficult due to the depth of groundwater presence. Their fore people have to dig wells and tube wells depending on the depth of water presence. Rainwater is used by people in the rainy season. Collecting rain waters to small pond tanks and preserving them to dry season is done in most of the dry season areas. Cause the is run out of water more quickly than in other areas.