Water storage is a term used within agriculture to define locations where water is stored for later use. These range from natural water stores, such as groundwater aquifers, soil water and natural wetlands to small artificial ponds, tanks and reservoirs behind major dams.

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. There are two broad types of aquifers: confined and unconfined. An unconfined aquifer is where the surface is not restricted by impervious rocks, so the water table is at atmospheric pressure. In a confined aquifer, the upper surface of water is overlain by a layer of impervious rock, so the groundwater is stored under pressure.

Soil moisture is the water held between soil particles in the root zone of plants, generally in the top 200 cm of soil. Water storage in the soil profile is extremely important for agriculture, especially in locations that rely on rainfall for cultivating plants. For example, in Africa rain-fed agriculture accounts for 95% of farmed land.

Water is a chemical substance with the chemical formula H₂O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state (water vapor or steam). Water also exists in a liquid crystal state near hydrophilic surfaces. Under nomenclature used to name chemical compounds, dihydrogen monoxide is the scientific name for water, though it is almost never used.

Water covers 70.9% of the Earth's surface, and is vital for all known forms of life. On Earth, 96.5% of the planet's water is found in oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation. Only 2.5% of the Earth's water is freshwater, and 98.8% of that water is in ice and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products.

Storage may refer to: