By Andrew Lee and Oliver Royle

Definition The Water Cycle, also know as the hydrological cycle, is the journey that water takes through mainly evapotranspiration, condensation, precipitation, infiltration, percolation and runoff. The water cycle is a closed system, meaning that no water is added or taken from the cycle, although the distribution of the water changes.

Concepts Evapotranspiration is the process of evaporation and transpiration combined. Evaporation is the process in which the water turns into a gaseous state from a liquid state. Transpiration is the discharge of water vapour into the atmosphere through plants. Condensation is the process by which water changes to a liquid state from a gaseous state. Infiltration is the movement of water downward into the earth’s surface. Percolation is the descending movement of liquid through the solid or rock. Runoff is the water that flows over the surface of the land towards rivers, lakes, oceans etc. Precipitation is when the water passes through the atmosphere to the earth’s surface. E.g. rain, snow, etc.

Mind Map

Human Impacts Humans have impacted the water cycle in many ways. Population increases, rising living standards and industrial and economic growth have put a lot more stress on the environment. Some activities can change the hydrologic equation and can affect the quantity and quality of natural water resources available to current and future generations. The water used by households, industries, and farms has increased and people demand it to be clean. The amount of fresh water is limited and the easily accessible sources have been developed. As the population increases, so will our need to withdraw more water from rivers, lakes and aquifers, threatening local resources and future water supplies.

Human Impacts A larger population will not only use more water but will discharge more wastewater from domestic, agricultural, and industrial wastes. Poor irrigation practices also raise soil salinity and evaporation rates. All of these factors place far more pressure on existing water resources. Drainage of water through road drains and city sewer systems alters the rates of infiltration, evaporation, and transpiration. All of these various effects determine the amount of water in the water system and can result in negative consequences for river watersheds, lake levels, aquifers, and the environment as a whole.

Water Cycle (Human Impact)

Evaporation is when moisture is lost directly to the atmosphere from either land or ocean. The rate of this depends on temperature, wind velocity, humidity and hours of sunshine. Condensation is the process by which water changes to a liquid state from a gaseous state. The rate of condensation depends on air temperature and the rate of atmospheric cooling. Evapotranspiration is the process of evaporation and transpiration combined. Both components of this involve transpiration of water from a liquid state to a gaseous state. Transpiration is the discharge of water vapour into the atmosphere through the leaves of plants. The rate of this depends on the time of the year, type of vegetation and the length of the growing season.

Precipitation is when the water passes through the atmosphere to the earth’s surface. E.g. rain, snow, etc. This happens when large masses of moist air are cooled rapidly below dew point. When the liquid becomes too heavy for the atmosphere to support it, after a further condensation, precipitation occurs. Infiltration is the movement of water downward into the earth’s surface. The water enters the soil and passes through many different layers of the soil profile. The rate of this depends on the amount of water already in the soil. The water continues downward until a sild called its infiltration capacity, then it is transferred across as ground water. Percolation is the descending movement of liquid through the solid or rock. Runoff is the water that flows over the surface of the land towards rivers, lakes, oceans

Distributing different quality water: This technique involves using high quality water for drinking water and bathing water whilst making use of lower quality water for gardening and washing cars etc. This conserves the amount of fresh water which we could have a huge use for in the future. Water Tanks: Water tanks can be used to withhold as much water as possible. This lowers the strain on main water supplies which is good for both drought and the environment. Management Techniques

The water tank management technique is similar to the technique of distributing different quality water as they both try to lower the amount of water coming out of main water supplies such as dams. It is also very different, as water tanks are individual and it uses just fresh water. The distribution system uses unfiltered water for purposes such as gardening and does not have to be individual.

Video This video is a great example to show how humans are not conserving our precious resources. The management techniques in this video include creating filters and catchments underneath the streets of Los Angeles. The people of Los Angeles have made a great improvement in the retention of rainwater in conserving it for the future. Before the catchments were built, the city had lost an estimated 80 billion galleons of rainwater. For a city who imports 85% of its rainwater it is way too much. Efforts like this should be used all over the world. Sydney especially receives a lot of rain, however Warragamba Dam does not. If Sydney employed this technique it could help the drought effort exponentially.