Properties of Water

Water Composition and Properties

• Water is composed of hydrogen and oxygen and exists in gaseous, liquid, and solid states.
• It is the most important molecule for life, used by every known living organism.
• Water's properties make it essential for life: • It moves easily through living organisms as a liquid at room temperature. • It is the universal solvent, dissolving most other substances. • It exists naturally in all three phases (solid, liquid, and gas), allowing for easy transportation around the Earth.

Water Cycle (Hydrologic Cycle)

• Water moves through the atmosphere and Earth due to energy from the sun and gravity.
• The water cycle involves: • Evaporation: water changes from liquid to gas or vapor. • Transpiration: water moves through plants and evaporates from aerial parts. • Evapotranspiration: loss of water from soil through evaporation and transpiration. • Precipitation: release of water from clouds in forms like rain, snow, or hail. • Infiltration: water enters the soil from the ground surface. • Percolation: slow movement of water through soil pores or permeable rock. • Runoff: water flows over the land surface. • Interflow: subsurface runoff, the rapid flow of water toward stream channels.

Transformation of Water

• Water undergoes phase transformations: • Liquid to gas (evaporation/evapotranspiration) • Gas to liquid (condensation, e.g., cloud formation) • Gas to solid (deposition, e.g., snow formation) • Solid to liquid (snowmelt)

Groundwater

• Groundwater is water that infiltrates the ground's surface and fills pores and fractures underground.
• Aquifers are sponge-like formations of rock and sand that contain groundwater.
• The water table is the uppermost border of the aquifer.
• Water enters aquifers through recharge zones.
• Confined aquifers are trapped between impermeable rock or clay layers.
• Wells that enter unconfined aquifers are called water table or groundwater wells.
• Wells that enter confined aquifers are called artesian wells.

Surface Waters

• Streams and rivers are fed by runoff from surrounding areas and areas where groundwater flows to the surface.
• Lakes and ponds are standing bodies of surface water fed by rivers, streams, and runoff from precipitation.
• Watersheds are defined as the land area that drains to a point of concern, with drainage due to gravity.
• Watershed boundaries are defined by topographical ridges.

Water Usage

• Residential water use includes all indoor and outdoor uses of drinking quality water at single-family homes.
• Water stress occurs when demand exceeds supply, often in naturally arid ecosystems, heavily populated countries, and areas with intensive agriculture.
• Overconsumption happens when water is consumed faster than it is replenished.
• Groundwater depletion is primarily caused by sustained groundwater pumping.
• Excessive groundwater consumption can lead to: • A cone of depression around a groundwater well. • Saltwater intrusion into freshwater aquifers. • Subsidence, a compression and sinking of the zone of saturation.

Solutions to Water Depletion

• Addressing water stress requires reducing demand or increasing supply through sustainable solutions.