Know : Rainwater Harvesting – Complete Info

The fresh water available in the earth is just 3%. Rain is one of the major sources of Freshwater, which we hardly consider preserving. Rainwater harvesting is a technique of collection and storage of rainwater into natural reservoirs or tanks, or the infiltration of surface water into subsurface aquifers (before it is lost as surface runoff). Even we can collect water from fog and dew! In this article we see various methods of Rain water harvesting, how to construct such harvesting facilities and many more info. 

The reasons for using rainwater harvesting systems answer three questions:

  • What: Rainwater harvesting will improve water supply, food production, and ultimately food security.
  • Who: Water insecure households or individuals in rural areas will benefit the most from rainwater harvesting systems.
  • How: Since rainwater harvesting leads to water supply which leads to food security, this will greatly contribute to income generation.
 Rainwater Harvesting TECHNOLOGIES 
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Rooftop rainwater harvesting


Rainwater harvesting icon.pngRainwater harvesting refers to structures like homes or schools, which catch rainwater and store it in underground or above-ground tanks for later use. One way to collect water is rooftop rainwater harvesting, where any suitable roof surface — tiles, metal sheets, plastics, but not grass or palm leaf — can be used to intercept the flow of rainwater in combination with gutters and downpipes (made from wood, bamboo, galvanized iron, or PVC) to provide a household with high-quality drinking water. A rooftop rainwater harvesting system might be a 500 cubic meter underground storage tank, serving a whole community, or it might be just a bucket, standing underneath a roof without a gutter. Rainwater harvesting systems have been used since antiquity, and examples abound in all the great civilizations throughout history. 

Suitable conditions

Rainwater harvesting requires at least an annual rainfall of 100-200 mm. Many places in Latin America have rainfalls of about 500 millimeters per year. It is suitable even when the roof is small. For example a 5 x 6 meters (that is to say 30 square meters) house, with 500 mm annual precipitation, receives a rainfall of 15.000 liters on its roof; this is a sufficient amount for a family formed by 5 members.

Advantages Disadvantages
– Possible in almost any climate 
– Rainwater generally meets drinking water quality standards, if system is well-designed and maintained
– Storage is needed to bridge dry periods 

For complete information on Roof top method (Click Here)

In situ rainwater harvesting


In situ icon.pngIn arid and semi-arid regions, where precipitation is low or infrequent during the dry season, it is necessary to store the maximum amount of rainwater during the wet season for use at a later time, especially for agricultural and domestic water supply. One of the methods frequently used in rainwater harvesting is the storage of rainwater in situ. Topographically low areas are ideal sites for in situ harvesting of rainfall. This technique has been used in the arid and semi-arid regions of northeastern Brazil, Argentina, and Paraguay, primarily for irrigation purposes. The in situ technology consists of making storage available in areas where the water is going to be utilized.

Generally this technology is simple and easy to use. Governmental organizations and the agricultural community generally work together to support and promote the in situ rainwater storage. Educational and information programs should be provided to inform users of the benefits of this technology, and the means of implementing rainwater harvesting while preventing soil loss.

Suitable conditions

This technology increases water supply for irrigation purposes in arid and semi-arid regions. It promotes improved management practices in the cultivation of corn, cotton, sorghum, and many other crops. It also provides additional water supply for livestock watering and domestic consumption. In situ is applicable to low topographic areas in arid or semi-arid climates.

Extensive use is found in northeastern Brazil, in the Chaco region of Paraguay, and in Argentina. It can be used to augment the water supply for crops, livestock, and domestic use. With the mechanization of agriculture, its use has diminished, but it is still recommended for regions where the volume of rainfall is small and variable. The approach used depends primarily on the availability of equipment, the nature of the agricultural and livestock practices, and the type of soil.

Advantages Disadvantages
– This technology requires minimal additional labor.

– It offers flexibility of implementation; furrows can be constructed before or after planting.

– Rainwater harvesting allows better utilization of rainwater for irrigation purposes, particularly in the case of inclined raised beds.

– Rainwater harvesting is compatible with agricultural best management practices, including crop rotation.

– It provides additional flexibility in soil utilization.

– Permeable in situ rainwater harvesting areas can be used as a method of artificially recharging groundwater aquifers.

– In situ rainwater harvesting cannot be implemented where the slope of the land is greater than 5%.

– It is difficult to implement in rocky soils.

– Areas covered with stones and/or trees need to be cleared before implementation.

– The additional costs incurred in implementing this technology could be a factor for some farmers.

– It requires impermeable soils and low topographic relief in order to be effective.

– The effectiveness of the storage area can be limited by evaporation that tends to occur between rains.

For Complete information of In situ rainwater harvesting (Click Here)

Surface water – general

Surface waterRainwater that is not captured directly, used by agriculture, or absorbed into the ground becomes surface water. Surface water harvesting includes all systems that collect and conserve surface runoff after a rainstorm or in intermittent streams, rivers, or wetlands for storage in open ponds and reservoirs. This can provide water for direct household use (treatment is generally required), irrigation, livestock, and aquaculture. Storage can also be the goal of collecting surface water, whether through open reservoirs or direct infiltration to aquifers below ground. Storing water in an aquifer conserves water better as it prevents evaporation, unlike open reservoir systems.

Climate change considerations
Cement made for water collecting structures, in a time of drought, can be made poorly due to less (or polluted) water used in the cement-making process. Higher heat from climate change will increase evaporation rates in reservoirs, or floods may damage infrastructure and increase runoff volumes. These effects and more are listed and tips are given to adapt the water system to climate change conditions.

 Various Types of Surface rainwater harvesting
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Groundwater recharge – general

Groundwater rechargeGroundwater recharge is the enhancement of natural ground water supplies using man-made conveyances such as infiltration basins, trenches, dams, or injection wells. Aquifer storage and recovery (ASR) is a specific type of groundwater recharge practiced with the purpose of both augmenting ground water resources and recovering the water in the future for various uses.

Climate change considerations

  • More storage capacity needed to overcome seasonal dry periods and to reduce floods.
  • Higher rainfall intensities may exceed infiltration capacities. Create storage, enhanced infiltration or artificial recharge. 
  • Lower rainfall results in the need for transport and storage of water from other areas. 
  • Changes in vegetation will cause changes in evapotranspiration, surface runoff, erosion and sediment transport/deposition. This requires water and soil conservation measures, like terracing.
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Fog and dew collection

Fog Harvesting

Fog collection (or fog harvesting) is an innovative, environmentally appropriate, socially beneficial and economically viable use of fog, rain and dew as sustainable water resources for people in arid regions of developing countries. Fog is composed of enormous numbers of tiny water droplets. The wind blown droplets can be collected by a plastic mesh. Typical fog harvesting in a well selected desert environment would be 5 liters of water per square meter of mesh per day.

Dew harvesting (or dew collection) is simply taking advantage of water vapor in the atmosphere to harvest clean and potable water through condensation, a passive process that allows water particles to return to the earth in a pure form. Dew harvesting has been practiced by humanity as far back as ancient times, in areas where rainfall and groundwater resources are scarce. When there is any humidity at all in the air and there is a surface that is cool enough to provoke condensation, dew will condense on that surface until the humidity is gone. Vegetation in desert regions have developed modifications that allow them to collect their own humidity from the air, for example, and through efforts of reforestation in desert regions this technology has advanced abundantly around the world.

Courtesy :

Know : Atmospheric Circulation

Atmospheric circulation is the large-scale movement of air, and the means (together with the smaller ocean circulation) by which thermal energy is distributed on the surface of the Earth.

Earth_Global_CirculationThe large-scale structure of the atmospheric circulation varies from year to year, but the basic climatological structure remains fairly constant. Individual weather systems – mid-latitude depressions, or tropical convective cells – occur “randomly”, and it is accepted that weather cannot be predicted beyond a fairly short limit: perhaps a month in theory, or (currently) about ten days in practice (see Chaos theory and Butterfly effect). Nonetheless, as the climate is the average of these systems and patterns – where and when they tend to occur again and again – it is stable over longer periods of time.

As a rule, the “cells” of Earth’s atmosphere shift polewards in warmer climates (e.g. interglacials compared toglacials), but remain largely constant even due to continental drift; they are, fundamentally, a property of the Earth’s size, rotation rate, heating and atmospheric depth, all of which change little. Tectonic uplift can significantly alter major elements of it, however – for example the jet stream -, and plate tectonics shift ocean currents. In the extremely hot climates of the Mesozoic, indications of a third desert belt at the Equator has been found; it was perhaps caused by convection. But even then, the overall latitudinal pattern of Earth’s climate was not much different from the one today.


See More Know : Weakening Trade Winds and Global Warming

Courtesy : Mr. Smajda’s Class Videos, YouTube and Wikipedia

Know : Weakening Trade Winds and Global Warming

What are the trade winds?

globalcircThe trade winds are just air movements toward the equator. They are warm, steady breezes that blow almost continuously. The Coriolis Effect makes the trade winds appear to be curving to the west, whether they are traveling to the equator from the south or north.

The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth’s atmosphere, in the lower section of the troposphere near the Earth’s equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Historically, the trade winds have been used by captains of sailing ships to cross the world’s oceans for centuries, and enabled European empire expansion into the Americas and trade routes to become established across the Atlantic and Pacific oceans.

In meteorology, the trade winds act as the steering flow for tropical storms that form over the Atlantic, Pacific, and southern Indian Oceans and make landfall in North America, Southeast Asia, and Madagascar and eastern Africa, respectively. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean Sea, as well as portions of southeastern North America. Shallow cumulus clouds are seen within trade wind regimes, and are capped from becoming taller by a trade wind inversion, which is caused by descending air aloft from within the subtropical ridge. The weaker the trade winds become, the more rainfall can be expected within neighboring landmasses.

Understand Atmospheric Circulation better from the basics here

windpatThe trade winds in the Pacific Ocean are weakened as a result of global warming, according to a new study that indicates changes to the region’s biology are possible.

Using a combination of real-world observations and computer modeling, researchers conclude that a vast loop of circulating wind over the Pacific Ocean, known as the Walker circulation, has weakened by about 3.5 percent since the mid-1800s. The trade winds are the portion of the Walker circulation that blow across the ocean surface.

The researchers predict another 10 percent decrease by the end of the 21st century. 

The effect, attributed at least in part to human-induced climate change, could disrupt food chains and reduce the biological productivity of the Pacific Ocean, scientists said.

Humans to blame

The researchers used records of sea-level atmospheric pressure readings from as far back as the mid-1800s to reconstruct the wind intensity of the Walker circulation over the past 150 years. A computer climate model replicated the effect seen in the historical record.

Some of the computer simulations included the effects of human greenhouse gas emissions; others included only natural factors known to affect climate such as volcanic eruptions and solar variations.

“We were able to ask ‘What if humans hadn’t done anything? Or what if volcanoes erupted? Or if the sun hadn’t varied?'” Vecchi said. “Our only way to account for the observed changes is through the impact of human activity, and principally from greenhouse gases from fossil fuel burning.”

The earth’s average temperature has risen by about 1 degree Fahrenheit over the past century and many scientists believe greenhouse gases and carbon dioxide emissions from human activities are to blame.

“This is evidence supporting global warming and also evidence of our ability to make reasonable predictions of at least the large scale changes that we should expect from global warming,” Vecchi told LiveScience.

By extrapolating their data and combining it with results from other models, the researchers predict the Walker circulation could slow by an additional 10 percent by 2100.

Driving force

The trade winds blow from the east at an angle towards the equator and have been used by sailors for centuries seeking to sail west. Christopher Columbus relied on the Atlantic’s trade winds to carry him to North America. The winds get their name from their reliability: To say that a “wind blows trade” is to say that it blows on track.

The overall Walker circulation is powered by warm, rising air in the west Pacific Ocean and sinking cool air in the eastern Pacific.

This looping conveyer belt of winds has far-reaching effects on climate around the globe. It steers ocean currents and nourishes marine life across the equatorial Pacific and off the coast of South America by driving the upwelling of nutrient-rich cold water from the ocean depths to the surface.

The Walker circulation is also primarily responsible for transporting water vapor that evaporates from the ocean surface west, towards Indonesia; there, the moisture rises up into the atmosphere, condenses, and falls back to Earth as rain.

The effects of global warming

Several theories on the effects of global warming predict a weakening of the Walker circulation. Scientists think it works like this:

To remain energetically balanced, the rate at which the atmosphere absorbs water vapor must be balanced by the rate of rainfall. But as temperatures rise and more water evaporates from the ocean, water vapor in the lower atmosphere increases rapidly. Because of various physical processes, however, the rate of rainfall does not increase as fast.

Since the atmosphere is absorbing moisture faster than it can dump it, and because wind is the major transporter of moisture into the atmosphere, air circulation must slow down if the energy balance is to be maintained.

A drop in winds could reduce the strength of both surface and subsurface ocean currents and dampen cold water upwelling at the equator.

“This could have important effects on ocean ecosystems,” Vecchi said. “The ocean currents driven by the trade winds supply vital nutrients to near-surface ocean ecosystems across the equatorial Pacific, which is a major fishing region.”


Courtesy : Global Warming Weakens Trade Winds | LiveScience 

Eco-preservation : Alas! This many Environmental Issues Exist?

How many Environmental Issues are you aware of? This list will definitely exceed your known  list of issues. Just click the issue to know what it is all about. (Permalinks to wiki)

Courtesy and Source : Wikipedia

Documentary : Earth in 1000 years (31min)

This edition of COSMIC JOURNEYS explores the still unfolding story of Earth’s past and the light it sheds on the science of climate change today. While that story can tell us about the mechanisms that can shape our climate. It’s still the unique conditions of our time that will determine sea levels, ice coverage, and temperatures.

Ice, in its varied forms, covers as much as 16% of Earth’s surface, including 33% of land areas at the height of the northern winter. Glaciers, sea ice, permafrost, ice sheets and snow play an important role in Earth’s climate. They reflect energy back to space, shape ocean currents, and spawn weather patterns. 

But there are signs that Earth’s great stores of ice are beginning to melt. To find out where Earth might be headed, scientists are drilling down into the ice, and scouring ancient sea beds, for evidence of past climate change. What are they learning about the fate of our planet… a thousand years into the future and even beyond?

30,000 years ago, Earth began a relentless descent into winter. Glaciers pushed into what were temperate zones. Ice spread beyond polar seas. New layers of ice accumulated on the vast frozen plateau of Greenland. At three kilometers thick, Greenland’s ice sheet is a monumental formation built over successive ice ages and millions of years. It’s so heavy that it has pushed much of the island down below sea level. And yet, today, scientists have begun to wonder how resilient this ice sheet really is.

Average global temperatures have risen about one degree Celsius since the industrial revolution. They could go up another degree by the end of this century. If Greenland’s ice sheet were to melt, sea levels would rise by over seven meters. That would destroy or threaten the homes and livelihoods of up to a quarter of the world’s population.

With so much at stake, scientists are monitoring Earth’s frozen zones… with satellites, radar flights, and expeditions to drill deep into ice sheets. And they are reconstructing past climates, looking for clues to where Earth might now be headed… not just centuries, but thousands of years in the future.

Periods of melting and freezing, it turns out, are central events in our planet’s history.
That’s been born out by evidence ranging from geological traces of past sea levels… the distribution of fossils… chemical traces that correspond to ocean temperatures, and more. 

Going back over two billion years, earth has experienced five major glacial or ice ages. The first, called the Huronian, has been linked to the rise of photosynthesis in primitive organisms. They began to take in carbon dioxide, an important greenhouse gas. That decreased the amount of solar energy trapped by the atmosphere, sending Earth into a deep freeze. 

The second major ice age began 580 million years ago. It was so severe, it’s often referred to as “snowball earth.” The Andean-Saharan and the Karoo ice ages began 460 and 360 million years ago. Finally, there’s the Quaternary… from 2.6 million years ago to the present. Periods of cooling and warming have been spurred by a range of interlocking factors: the movement of continents, patterns of ocean circulation, volcanic events, the evolution of plants and animals.

The world as we know it was beginning to take shape in the period from 90 to 50 million years ago. The continents were moving toward their present positions. The Americas separated from Europe and Africa. India headed toward a merger with Asia. The world was getting warmer. Temperatures spiked roughly 55 million years ago, going up about 5 degrees Celsius in just a few thousand years. CO2 levels rose to about 1000 parts per million compared to 280 in pre-industrial times, and 390 today. 

But the stage was set for a major cool down. The configuration of landmasses had cut the Arctic off from the wider oceans. That allowed a layer of fresh water to settle over it, and a sea plant called Azolla to spread widely. In a year, it can soak up as much as 6 tons of CO2 per acre. Plowing into Asia, the Indian subcontinent caused the mighty Himalayan Mountains to rise up. In a process called weathering, rainfall interacting with exposed rock began to draw more CO2 from the atmosphere… washing it into the sea. Temperatures steadily dropped. 

By around 33 million years ago, South America had separated from Antarctica. Currents swirling around the continent isolated it from warm waters to the north. An ice sheet formed. In time, with temperatures and CO2 levels continuing to fall, the door was open for a more subtle climate driver. It was first described by the 19th century Serbian scientist, Milutin Milankovic. 

He saw that periodic variations in Earth’s rotational motion altered the amount of solar radiation striking the poles. In combination, every 100,000 years or so, these variations have sent earth into a period of cool temperatures and spreading ice.

Source & Courtesy : SpaceRip, Youtube