- Runoff
Precipitation that reaches the surface of the Earth but does not infiltrate the soil is called runoff. Runoff can also come from melted snow and ice.
When there is a lot of precipitation, soils become saturated with water. Additional rainfall can no longer enter it. Runoff will eventually drain into creeks, streams, and rivers, adding a large amount of water to the flow. Surface water always travels towards the lowest point possible, usually the oceans. Along the way some water evaporates, percolates into the ground, or is used for agricultural, residential, or industrial purposes.
- And evapotranspiration.
Evapotranspiration is water evaporating from the ground and transpiration by plants. Evapotranspiration is also the way water vapour re-enters the atmosphere.
Evaporation occurs when radiant energy from the sun heats water, causing the water molecules to become so active that some of them rise into the atmosphere as vapour.
Explanation 1
Together, these five processes - , , , , and - make up the Hydrologic Cycle. Water vapour condenses to form clouds, which result in precipitation when the conditions are suitable. Precipitation falls to the surface and infiltrates the soil or flows to the ocean as runoff. Surface water (e.g., lakes, streams, oceans, etc.), evaporates, returning moisture to the atmosphere, while plants return water to the atmosphere by transpiration.
Explanation 2
Heat from the sun makes water evaporate from the oceans, rivers and lakes forming water vapour.
As the water vapour rises it cools and starts to condense and become water again. This forms clouds.
As the clouds get cooler the water droplets become bigger and bigger. Eventually they fall as rain, snow, sleet, or hail.
The water then runs back into the oceans, rivers and lakes and the cycle repeats!
Water is the lifeblood of industry. It is used as a raw material, a coolant, a solvent, a transport agent, and as a source of energy. A regular sized family car coming off the assembly line, for example, will have used at least 120 000 litres of water – 80 000 to produce its tonne of steel and 40 000 more for the actual fabrication process. Many thousands more litres of water are involved in the manufacture of its plastic, glass, fabric components. Manufacturing accounted for 14% of water withdrawals in 1996. Paper and allied products, primary metals, and chemicals were the three main industrial users.
Fertilisers that are leached from the soil or washed from the crop or soil in runoff may enter local surface or groundwater bodies, with the possibility of reaching surface water-bodies such as rivers, lakes, lagoons, estuaries and coastal marine environments.
Increased pesticide use, if indiscriminate, can have severe impacts on water supplies by way of drainage channels, runoff to surface water-bodies, or leaching to ground-waters.
Factors that bring about the eutrophication process are nutrient enrichment with phosphorous and nitrogen; a carbon source of carbon dioxide; favourable temperatures; and non-turbid water. If the three latter conditions are favourable nutrient concentrations of 0.3 parts per million nitrogen and 10 parts per billion phosphorous will bring about eutrophication.
Eutrophication also degrades the aesthetic qualities of surface water bodies by inducing excessive algal scum and growth of aquatic weeds, as well as undesirable colour, taste and odour.
Potential environmental impacts associated with the termination of agrochemical use include polluted surface and ground waters
Mitigation measures to minimise impacts associated with post operation of agrochemical projects will depend on the purposes for which the land is to be used. Potential measures include proper disposal of unused agrochemicals, containers and equipment used for application. In addition contaminated areas (particularly water bodies) may need to be fenced off and warning signs erected or, preferably, remedial action taken.
Soil and water quality should be regularly monitored; the frequency of which will depend on the purpose for which the land is to be used.
What is meant by the term water hardness and how do we measure it?
The hardness of water depends on the amount of calcium and magnesium salts contained. The greatest part of the hard water is built by hydrogen carbonates.
You measure the water hardness in "DEUTSCHEN HÄRTEGRADEN" (°dH)
· Water: 0 -7 °dH > is soft water
· Water: 8 -15 °dH > is middle-hard water
· Water: more than 15°dH > is hard water
Temporary hardness can simply be removed by boiling the water.
Permanent hardness can be removed by adding sodium carbonate.
Hard water contains dissolved compounds which are good for health. It often provides calcium to strengthen bones, and there is evidence of people who live in hard water areas as they have reduced risk of heart disease. Using hard water can increase cost as more soap is needed.
Some hard water decomposes when it is boiled.
Ca(HCO3)2 à CaCO3 + H2O + CO2
This is the reverse of the reaction which forms the hard water in the first place.
Water will dissolve a little bit of most things, but the polar nature of the water molecule results in water molecules orienting themselves around charged particles making ions and polar molecules the most soluble. This is why it is used as a solvent.