What Is A Nuclear Reaction?

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Photovoltaic Cells, Solar Power, and LEDs

Most of the world’s energy can go back to our sun. Every day we are heated by its electromagnetic rays, and plants use the sun’s energy to make sugars and ultimately proteins and other good things to eat. Fossil fuels were also once made from these plant and other organisms that relied on the sun’s energy millions of years ago. Today, humans can convert the sun’s energy directly into electricity, through solar thermal and solar photovoltaic systems.

SOLAR THERMAL OR PHOTOVOLTAIC?

Solar panels, also called solar thermal, convert sunlight to heat and then heat to electricity. Photovoltaic cells, or solar cells, convert sunlight directly into electric current by way of carefully-engineered semiconductor materials.

Though solar photovoltaics are more efficient converters of sunlight, they are also more expensive.

As of May 2011, the world’s largest solar power plant is a concentrating solar thermal power plant in the Mohave desert in California. Solar Energy Generating Systems has a capacity of 310 megawatts and uses parabola-shaped reflective troughs to concentrate electromagnetic radiation.

The world’s largest solar photovoltaic plant is probably the Sarnia Solar Project in Ontario, Canada. It has a capacity of roughly 80 megawatts.

HOW SOLAR THERMAL WORKS

Sunlight heats a design element (water, air, chemical fluids), and that thermal energy is transmitted for other applications, such as heating water, heating space, or generating electricity. In solar thermal power plants, sunlight heats a specialized fluid, which in turn heats water into steam, which can run turbines and produce electricity.

Solar thermal power plants use concentrators that bounce the sunlight off elliptical mirrors to a central tube, in which the specialized fluid lies.

HOW PHOTOVOLTAICS WORK

Photovoltaic cells are made of specialized diodes. Electrons (natural components of atoms) in the photovoltaic cells absorb light, which excites them to a state where they can be conducted as electrical current. This difference in energy, between the valence band (the state of a normal electron staying around its home atom) to the conduction band (electron free to move between atoms) is called the band gap.

Solar photovoltaic farm in Indonesia. Photo by Chandra Marsono.

Well-engineered photovoltaics have a band gap that coincides with the energies of as broad a spectrum of light as possible, to convert the maximum amount of the sunlight into electricity.

As sunlight energy pops electrons into the conduction band and away from their home atoms, an electric field is produced. The negatively-charged electrons separate from the positively-charged “holes” they leave behind, so that when electrons are freed into the conduction band, they move as electric current in the electric field, electricity.

PHOTOVOLTAICS ARE MADE OF SPECIALIZED MATERIALS

An ever-expanding variety of semiconductor materials can be used to make solar cells; universities and companies worldwide are researching these options, from special bio-plastics to semiconductor nanocrystals. Nonetheless, the photovoltaic cells available today require precise manufacturing conditions and are therefore far more expensive to produce than solar panels.

Silicon has to be processed under clean room conditions — carefully regulated atmospheres — to remove impurities and prevent introducing contaminants, both of which can change the band gap. Thin film-based photovoltaics require special production methods, like chemical vapor deposition. Semiconductor processing also uses strong acids and often dangerous chemicals for etching.

Today, commercially-sold cells are made from purified silicon or other crystalline semiconductors like cadmium telluride or copper indium gallium selenide.

WHERE DO WE GET THE STARTING MATERIALS?

Silicon is plentiful in the Earth’s crust. Cadmium is a readily available but highly toxic heavy metal, as is arsenic, another chemical used in some cells. As tellurium demand is only recently rising in response to solar demand, it’s unknown what the global supply is for this unusual element but it may be quite abundant. Photovoltaics are a lively area of research, and the future production and environmental costs of starter materials, production, and pollution are difficult to predict.

California, Massachusetts, Ohio, and Michigan produced the most photovoltaics in 2009. However, that year, 58 percent of photovoltaics were imports, primarily from Asian countries like China, Japan, and the Philippines.

LED TECHNOLOGY: MORE THAN HEADLAMPS

Photovoltaic cells work in the opposite direction of light-emitting diodes, or LEDs. LEDs are used interchangeably with other lighting, like light bulbs. However, LED’s work in a completely different manner, far closer to the way photovoltaics work.

Click here see a bar chart comparing how much energy is used by various light sources.

LEDs absorb energy in the form of electricity, exciting electrons into the conduction band. When the electrons in the semiconductor material drop back into the valence band from the conduction band, they emit energy in the form of photons, or electromagnetic radiation.

It’s a highly efficient process because energy isn’t wasted on producing heat, which happens with standard tungsten filament bulbs. LEDs also last a much longer time as they do not have filaments to burn out, and because they are very small and several units are used to replace one large traditional lamp, they do not all burn out at once. That makes LEDs a good choice for stoplights or other safety critical applications.

 

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Thermodynamics and Thermal Energy

Thermodynamics is the study of how energy moves and changes form, usually by way of heat, as suggested by the components of its name: thermo-dynamics. Its laws and equations help to predict what could happen in various situations, based on the temperature, pressure, materials, and shape of a system.

Thermodynamics tells us how to calculate the ultimate temperature of a refrigerator or how much energy we can get out of a steam engine. Thermodynamics can also be applied to chemistry and the world on an atomic level, predicting which compounds are stable at specific temperatures and pressures. Thermodynamics explains why diamonds form naturally and spontaneously from carbon-based compounds deep inside the Earth, but they cannot form spontaneously here on the surface.

Thermodynamics relies on the idea that energy is conserved, even if it is transferred from or to a system to its surroundings through heat, changes in momentum, or other forms of energy.

 

TEMPERATURE AND HEAT

Heat and thermal energy are directly related to temperature. We can’t see individual atoms vibrating in solids, liquids, and gases, but we can feel their kinetic energies as temperature. Atoms in solids, liquids, and gases do vibrate. If they didn’t, they would be at absolute zero, a theoretical state of zero thermal energy at ­-459.67 Fahrenheit.

When there’s a difference between the temperature of the environment and a system within it, thermal energy is transferred between them as heat. Something doesn’t have heat. Instead, as an object or system gains or loses heat, it increases or decreases its thermal energy.

Adjacent objects that exhibit different temperatures will spontaneously transfer heat to try to reach the same temperature as each other, or equilibrium. However, how much energy it takes to change the temperature of an object is based on what its made of, a property called heat capacity or thermal capacity.

Water has a higher heat capacity than steel, for example. An empty pot on the stove takes almost no time to get to 212 degrees Fahrenheit, or the boiling temperature of water. A pot with some water in it will take far much longer to reach the same temperature, because water needs to absorb more energy — per weight, per degree — to gain the same number of degrees as metal. (Even though the vaporization temperature of metal is far, far higher than the water’s).

 

THERMAL ENERGY STORAGE: A SOURCE OF POWER

Thermal energy storage exploits the difference in temperature between a system and the environment. In the late 1800s, Americans used thermal energy storage by cutting blocks of lake ice during the winter and storing them underground packed in insulating wood shavings. When the summer rolled around, they retrieved that stored ice to make food cold, exploiting the difference in temperature to force thermal energy out of the food and into the ice.

Thermal energy storage can also happen in the other direction. Electricity or other forms of energy can be used to heat various materials, which are stored in insulated containers. Later, when the energy is needed, the hot materials can heat water into steam, and that steam can push turbines, which in turn produce electricity.

Solar panels use thermal energy storage. The panels absorb the heat of sunlight and store that energy so it can be transformed into electricity with turbines. There are several kinds of solar panels, but all rely on heat for energy, unlike photovoltaic cells.

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Forms of Energy: Motion, Heat, Light, Sound

What forms of energy is Raul using to move his LEGO car?

When he was a teenager in Romania, Raul Oaida became obsessed with building things: a jet-engine bike, a tiny spaceship, a LEGO car that runs on air. Why? Well, why not?

You can see more cool stories about energy at The Adaptors website.

Like video and audio? Check out The Adaptors Podcast.

 

Energy comes in two basic forms: potential and kinetic

Potential Energy is any type of stored energy. It can be chemical, nuclear, gravitational, or mechanical.

Kinetic Energy is found in movement. An airplane flying or a meteor plummeting each have kinetic energy. Even the tiniest things have kinetic energy, like atoms vibrating when they are hot or when they transmit sound waves. Electricity is the kinetic energy of flowing electrons between atoms.

energy_forms_pie-chartEnergy can shift between forms, but it is never destroyed or created.

A car transforms the potential energy trapped in gasoline into various types of energy that help the wheels turn and get the car to move. Most of the energy is converted to thermal energy, which is an unorganized form of energy that is difficult to convert into a useful form.

Power plants transform one form of energy into a very useful form, electricity. Coal and natural gas plants use the chemical potential energy trapped in fossil fuels. Nuclear power plants change the nuclear potential energy of uranium or plutonium into electricity too. Wind turbines change the kinetic energy of air molecules in wind into electricity. Hydroelectric power plants take advantage of the gravitational potential energy of water as it falls from the top of a dam to the bottom.

These transformations are hardly perfect. An efficient fossil fuel power plant loses more than half of the energy it creates to forms other than electricity, such as heat, light, and sound.

Forms of Potential Energy

GRAVITATIONAL

Systems can increase gravitational energy as mass moves away from the center of Earth or other objects that are large enough to generate significant gravity (our sun, the planets and stars).

For example, the farther you lift an anvil away from the ground, the more potential energy it has. Lifting the anvil is called work, which is an interaction in which energy is transferred from one system (the person) to another (the anvil). The person has to do more work in order to carry the anvil higher, and the higher the anvil is carried, the more gravitational potential energy is stored in the anvil. If the anvil is dropped, that potential energy transforms to kinetic energy as the anvil moves faster and faster toward Earth.

CHEMICAL

Chemical energy is stored in the bonds between the atoms in compounds. This stored energy is transformed when bonds are broken or formed through chemical reactions. Like letters of the alphabet that can be rearranged to form new words with very different meanings, atoms move around during chemical reactions, and they form new compounds with vastly different personalities.

When we burn sugar (a compound made of the elements hydrogen, oxygen, and carbon) in our bodies, the elements are reorganized into water and carbon dioxide. These reactions both absorb and release energy, but the overall result is that we get energy from the sugar, and our bodies use that energy to do work.

Chemical reactions that produce net energy are exothermic. When wood is burned, the chemical reactions taking place are exothermic. Electromagnetic and thermal energy are released. Only some chemical reactions release energy. Endothermic reactions need energy to start and to continue, such as by adding heat or light.

NUCLEAR

Today’s nuclear power plants are fueled by fission. Uranium or plutonium atoms are broken apart, freeing lots of energy. Hydrogen atoms in the sun experience nuclear fusion, combining to form helium and subsequently releasing large amounts of energy in the form of electromagnetic radiation and thermal energy.

Nuclear energy is the stored potential of the nucleus of an atom. Most atoms are stable on Earth; they keep their identities as particular elements, like hydrogen, helium, iron, and carbon, as identified in the Periodic Table of Elements. The number of protons in the nucleus tells you which element it is. Nuclear reactions change the fundamental identity of elements by splitting up an atom’s nucleus or fusing together more than one nucleus. These changes are called fission and fusion, respectively.

ELASTIC

Elastic energy can be stored mechanically in a compressed gas or liquid, a coiled spring, or a stretched elastic band. On an atomic scale, the stored energy is a temporary strain placed on the bonds between atoms, meaning there’s no permanent change to the material. These bonds absorb energy as they are stressed, and release that energy as they relax.

Forms of Kinetic Energy

MOTION

A moving object has kinetic energy. A basketball passed between players shows translational energy. That kinetic energy is proportional to the ball’s mass and the square of its velocity. To throw the same ball twice as fast, a player does more work and transfers four times the energy.

rotationalIf a player shoots a basketball with backspin or topspin, the basketball will also have rotational energy as it spins. Rotational energy is proportional to how many times it spins per second, as well as the ball’s mass, and the size and shape of the ball.

In shooting a basketball, players often try to add rotational energy as backspin, because it results in the greatest slowdown in speed when the basketball hits the rim or the backboard, increasing the chance that the ball stays near the basket. The opposite direction of spin, a topspin, can be used in games like tennis, because it will help speed up a ball after impact and lowers the angle it travels after the bounce.

THERMAL ENERGY AND TEMPERATURE

Thermal energy is directly related to temperature. We can’t see individual atoms vibrating, but we can feel their kinetic energies as temperature. When there’s a difference between the temperature of the environment and a system within it, thermal energy is transferred between them as heat.

tea kettleA hot cup of tea loses some of its thermal energy as heat flows from the tea to the air in the room. Over time, the tea cools to the same temperature as the room air. At the same time, the thermal energy in the room air increases due to heat transfer from the tea. However, the thermal capacitance of the room air is much larger than the tea, so the temperature of the air in the room increases by very little – so little that a person in the room wouldn’t notice it.

Heat  flows spontaneously from high temperature objects to nearby low temperature objects, until all objects reach the same temperature, called thermal equilibrium. Some materials are easier to heat up or cool down than others. The thermal capacitance, or heat capacity, of a material tells us how much energy it takes to raise that material one degree in temperature. A pound of water has greater thermal capacitance than the same amount of stainless steel, for example. In moments, an empty one pound pot on the stove heats to 212 degrees Fahrenheit (the boiling temperature of water). If you pour a pound of water into the pot, it will take much longer than the empty pot to reach the same temperature, because water needs more energy to get as hot as steel.

SOUND

Sound waves are made when stuff vibrates – like strings on an instrument or gas molecules in the air. Sound waves travel when the vibrating stuff causes stuff surrounding it to also vibrate. This happens in liquid, solid, or gaseous states. Sound cannot travel in a vacuum because a vacuum has no atoms to transmit the vibration.

Solids, liquids, and gases transmit sounds as waves, but the atoms that pass along the sound don’t travel the way photons do. The sound wave travels between atoms, like people passing along a “wave” in a sports stadium. Sounds have different frequencies and wavelengths (related to pitch) and different magnitudes (related to how loud).

Even though radio waves can transmit information about sound, they are a completely different kind of energy, called electromagnetic energy.

ELECTROMAGNETIC RADIATION

PlantElectromagnetic energy is the same as radiation or light. This type of energy can take the form of visible light, like the light from a candle or a light bulb, or invisible waves, like radio waves, microwaves, x-rays and gamma rays. Radiation — whether it’s coming from a candle or an x-ray tube — can travel in a vacuum. Sometimes physicists describe electromagnetic radiation as being composed of particles – tiny packets of energy called photons. Each photon has a characteristic frequency, wavelength, and energy, but all photons travel at the same speed, the speed of light, or nearly 1 billion feet per second.

Electromagnetic energy can be converted to the chemical energy stored in plants through photosynthesis, the process by which plants and algae use the sun’s radiation to turn carbon dioxide gas into sugar and carbohydrates.

ELECTRIC

Electric energy is to the kinetic energy of moving electrons, the negatively-charged particles in atoms. For more information about electricity, see Basics of Electricity.

 

-Anrica Deb

 

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Major sources of energy/their advantages and disadvantages

There is no easy answer to what is the best source of energy or electricity. Is the priority reliability, affordability, the economy, international human rights, limiting greenhouse gas emissions, preserving environmental resources, or human health?

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It’s undeniable that today — whether we like it or not — humans worldwide are overwhelmingly dependent on fossil fuels: coal, oil, and natural gas. Everything eaten, worn, lived in, and bought is tied to availability of fossil fuels. Even if 100 percent of politicians were determined to stop using them today, society has neither the electricity grid nor the vehicular and industrial technology to sustain the current American lifestyle on non-fossil sources of energy. Yet.

When comparing sources of energy, it’s easy to forget how universal fossil fuels are. These sources continue to dominate for reasons that are difficult to measure, like political influence, advertising clout, and control over energy infrastructure. Other sources have disadvantages purely because they don’t fit in as well.

Volume brings another difficulty in comparing sources of energy. There is so much more fossil energy, and it’s been used for a long time, so we know a lot more about its hazards and benefits. More modern technologies are harder to quantify. Some are renewable but still pollute (biofuels), some are very clean except in accidents or waste disposal (nuclear). Most electricity sources (renewable or not) use steam turbines, and all the water to make steam has to come from somewhere, but how important should that factor be?



Clicking the graphic above will give an abbreviated chart comparing sources line by line, but that doesn’t provide anywhere close to the whole story.

Each of the following topics compares the major sources of energy  through a different lens. Though environmental and local issues may seem the most important to those of us who don’t own power plants or utility companies, the cost of energy drives which sources are actually in place today and which sources will see investment tomorrow.

 

 

 

 

 

 

 

 

 

 

 


Source: U.S. Energy Information Administration

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The Connections Between Greenhouse Gas Emissions and Energy

Most of the greenhouse gas emitted through human activity comes from the production of energy.

This group of gases is thought to contribute to global climate change, long-term shifts in weather partly due to the tendency of these gases to trap energy, in the form of electromagnetic radiation from the sun, that would otherwise have been reflected back out into space. For more about the relationship between the climate and greenhouse gases, go here.

Noteworthy greenhouse gases  are carbon dioxide, nitrous oxide, methane, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

Energy creation results in such a high level of greenhouse gas because the vast majority of energy we use — regardless of what country we live in — comes from burning something, usually coal, petroleum fuels, natural gas, or wood. More than 80 percent of U.S. energy in 2009 came from the combustion of fossil fuels.  Go here for more information about how combustion works.

WE’VE BURNED THINGS FOR EONS, WHY IS IT DIFFERENT NOW?

Plants and some types of microscopic organisms take carbon dioxide gas out of the air and turn it back into solid, carbon-based materials like plant fibers, using the energy of sunlight. The basis for all of our fuels, even the fossil fuels, comes from exploiting the fact that organisms convert  light energy into chemical energy, a potential energy source inside the plant or organism’s cells, whether the energy was converted in the last few decades (wood, biodiesel, ethanol) or millions of years ago (fossil fuels). Today, however, organisms don’t have the capacity to capture anywhere near as much of the greenhouse gas carbon dioxide as we produce, partly because we are burning fuels produced over millions of years.

EMISSIONS ARE A WORLDWIDE PHENOMENON

The United States produces more greenhouse gas each year per person than most other countries. However, even if we stopped producing any carbon dioxide at all, which is unlikely, the world would still keep producing 80 percent of its former output. Other regions produce just as much as we do, particularly Europe and China.

Furthermore, instead of holding steady at a particular emission rate, every year we use more energy and therefore emit more greenhouse gas. For a graph of atmospheric carbon dioxide by year, go here.

When we talk about energy-related emissions, we don’t only mean electricity. Energy involves burning oil and natural gas for heating, burning gasoline, diesel, and jet fuels for transportation. Transportation accounted for just over a third of all carbon dioxide emissions in 2009, electricity was almost 40 percent and residential, commercial, and industrial production, excluding electricity, made up roughly 26 percent.

Some greenhouse gases are thought to alter the climate more than others. Nitrous oxide is a much smaller percent of the gas mix than carbon dioxide, but for its weight it has a much stronger heat-trapping capability.

For more information go to The connection between greenhouse gases, climate change, and global warming.

Each year what proportion of emissions are man-made are carefully tracked by several agencies nationally and internationally, including the National Oceanic and Atmospheric Administration, the National Weather Service, and the National Aeronautics and Space Administration.

Sources:

U.S. Geological Survey
U.S. Energy Information Administration

U.S. Environmental Protection Agency
U.S. National Oceanic and Atmospheric Administration
CIA World Fact Book
World Energy Council
National Renewable Energy Laboratory
Emissions of Greenhouse Gases in the United States 2009: Independent Statistics & Analysis. U.S. Energy Information Administration, Department of Energy. March 2011.

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The Connection Between Greenhouse Gases, Climate Change & Global Warming


 

WHAT IS THE DIFFERENCE BETWEEN CLIMATE CHANGE AND GLOBAL WARMING?

Climate change is the shift in long-term, global weather patterns due to human action; it’s not exclusive to warming or cooling.

Climate change includes any change resulting from different factors, like deforestation or an increase in greenhouse gases. Global warming is one type of climate change, and it refers to the increasing temperature of the surface of Earth. According to NASA, the term global warming gained popular use after geochemist Wallace Broecker published a 1975 paper titled Climatic Change: Are We on the Brink of a Pronounced Global Warming?

Since 1880, the average surface temperature of the Earth has increased by roughly 0.9 degrees Fahrenheit, but the rate it’s increasing is faster than that, depending on which region you live in. If you’re closer to the equator, temperatures are increasing more slowly. The fastest increase in temperatures in the United States is in Alaska, where average temperatures have been increases by more than 3 degrees Fahrenheit per century. For a graph of average global temperatures by year, see the NASA website here.

 

HOW GREENHOUSE GASES RELATE TO CLIMATE CHANGE

Greenhouse gases are those thought to contribute to the greenhouse effect, an overall warming of the Earth as atmospheric gases trap electromagnetic radiation from the sun that would otherwise have been reflected back out into space.

Noteworthy greenhouse gases are methane, nitrous oxide, carbon dioxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). These gases are thought to affect the climate directly and indirectly, even though they constitute only a small fraction of the blanket of gases that make up the atmosphere.

Currently, the composition of the atmosphere is mostly nitrogen and oxygen, with just 0.033 percent carbon dioxide and all other gases accounting for even less.

 

WHICH GASES CONTRIBUTE THE MOST?


According to 2010 models cited by NASA, 20 percent of the greenhouse effect is attributed directly to carbon dioxide and 5 percent to all other greenhouse gases. The remaining 75 percent of the greenhouse effect is thought to be due to water vapor and clouds, which are naturally-occurring. However, even though carbon dioxide and the other greenhouse gases are such a small percentage of the total gas in the atmosphere, they affect when, where and how clouds form, so greenhouse gases have some relevance when it comes to 100 percent of the greenhouse effect. Carbon dioxide is thought to modulate the overall climate, like a atmospheric thermostat.

Some greenhouse gases are produced in natural processes, like forest fires, animal manure and respiration, or volcanic eruptions. However, the majority of new greenhouse gases are produced from industrial processes and energy production.

The four largest human sources of U.S. greenhouse gases in 2009 were energy, non-fuel use of fossil fuels, natural gas production, and cement manufacture, in descending order. Non-fuel, greenhouse gas-producing applications of fuels include industrial production like asphalt, lubricants, waxes and other . Emissions related to cement manufacture happen when limestone (calcium carbonate) is reacted with silica to make clinker, the lumps ground to make cement. ( Emissions of Greenhouse Gases in the United States 2009: Independent Statistics & Analysis.)

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Petroleum, Natural Gas, and Coal

The world depends on fossil fuels for its energy, and the United States is no exception. The vast majority of U.S. energy — more than 80 percent in 2009 — comes from burning fossil fuels. (more…)

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Groundwater, the Water Cycle, and Depletion

THE WATER CYCLE AND GROUNDWATER

Water is created and destroyed in natural chemical reactions within plants and animals. However, most water sticks around. It changes phases through the water cycle; it can become polluted with salt, toxic chemicals, or pathogenic organisms. However, it generally doesn’t go away, globally speaking.

The water, or hydrologic, cycle describes how water moves through the atmosphere, on the Earth’s surface, and underground.

As “surface water” in the lakes, streams, rivers and oceans warms from the sun’s electromagnetic radiation, some evaporates into the atmosphere.

This water vapor in the atmosphere condenses into rain and snow, called precipitation. The precipitation falls on the Earth, eventually feeding into streams, lakes, and oceans. Some of the water seeps into the ground and collects in underground aquifers as groundwater. About 20 percent of the U.S. water supply comes from groundwater.

Groundwater can resurface from springs or it can discharge into lakes, streams, rivers, and oceans. High pressures deep inside the Earth can force groundwater up through artesian wells, or groundwater can be pumped up or pulled up in old-fashioned buckets from wells. (“Artesian” means that there’s sufficient water pressure that the groundwater need not be pumped).

Briones Reservoir in Northern California

Humans use water from the surface sources (lakes, rivers, oceans), we collect rainwater and snowmelt, and we also use groundwater. Most of this water gets discharged back out into waterways or oceans. However, water used in homes and businesses is sent to municipal water treatment, after which it is discharged into waterways, returning to the water cycle.

 

 

GROUNDWATER AND DEPLETION

Groundwater isn’t as free-flowing as surface water. Predicting and modeling how it flows is wildly complex, factoring for what’s dissolved in the water and what materials it’s moving through, in three dimensions. What is easy to say is groundwater moves slower than surface water, and it gets recharged more slowly. Because modeling is complex, and tracking depletion involves drilling wells, it’s far more difficult to gauge groundwater depletion than water shortages on the surface.

When groundwater is depleted, it is still there, just lower down, as many as several hundred feet lower in extreme cases. However unseen it is, groundwater depletion – and the lowering of the water table – is very serious for several reasons.

Trees and plants rely on groundwater, and if they cannot reach water with their roots in regions where it doesn’t rain all year long, they can die, and with them all the life that depends upon them.

For people who rely on well-water, depletion can be equally disastrous. As the depth needed to reach the water increases, the amount of energy required to pump it out also increases. Lowering the water table can pollute the water, as saltwater zones can underly freshwater zones.

And even for those who depend on surface water, which is all of us, groundwater depletion can have its effect because ground water feeds surface water and vice-versa. Groundwater depletion can reduce the amount of water in streams and lakes, even if the effects take years to become obvious.

 

ARE WE SINKING?

An apartment building in Amsterdam, The Netherlands.

As the water table lowers from groundwater depletion, the materials within the ground dry out and the ground can actually collapse in on itself, either suddenly or slowly over time, a phenomenon called subsidence. The most dramatic incidents of subsidence are sinkholes, but most of the sinking is happening imperceptibly slowly. This sinking is why some regions of the Netherlands came to be below sea level; centuries of pumping water out of the peat-based soils shrank them, and the land — protected from flooding by the North Sea and Rhine River waters behind dikes — sunk lower and lower.

Today, subsidence from pumping of water has been recorded all over the United States, but the Santa Clara Valley in California was the first area in the country where land subsidence from human use of groundwater was recognized and the first place that organized remediation to stop the subsidence in 1969, according to a report by the U.S. Geological Survey.

While today the region is best known for its Silicon Valley technology, in the late nineteenth century, Santa Clara was full of fruit orchards irrigated with groundwater, much of it from artesian wells, meaning that the wells filled themselves with the pressure of the water created by confined aquifers. Constant reliance on this easy source of groundwater meant by 1930, wells that formerly filled themselves had to be pumped, and by 1964 one well in downtown San Jose had sunk well over 200 feet below the surface.  As water was permanently removed from the ground, the ground shrank, and by 1984, downtown San Jose had sunk quite substantially, to just 84 feet above sea level from 98 feet above sea level in 1910.

 

For more about water use and energy see here.

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