Thursday, March 28, 2013

Sustainable Groundwater in Virginia

USGS groundwater monitoring well Prince William County, VA

It’s almost spring here on the edge of rural Virginia and time to think about the water supply. Last year was a dry summer over much of the continental United States and groundwater levels in Virginia were negatively impacted. The snow, sleet, and rain we’ve had in the past two months have soaked the ground ending the drought conditions lingering from last year. If your water like mine is supplied by a well, you need to be aware of the factors that impact your water supply and practice household water conservation in times of drought or low supply to live within your annual water resources. There are dry years and wet years and water availability will vary, though it is not always obvious. The groundwater aquifer you tap for water is not seen and has no supply gauge, but still you have to be aware of your water budget and live within it, something that transplants from the suburbs and city are not always aware of. No water supply is unlimited and a well is limited by the aquifer and age and condition of the well and you need to be aware of your water use. 

The good news for us in Virginia is that according the U.S. Drought Monitor, Virginia is no longer in drought conditions, but the U. S. Geological Survey, USGS, is still showing 20% of the groundwater monitoring wells in Virginia at below average water levels for this time of year. A deluge of heavy rains could change that in a hurry since the soil in our region is no longer dry.  I feel quite lucky that the monitoring well up the road from my house is showing a higher than average water level for the 39 years of monitoring data the USGS has. Nonetheless, unless my neighbors and I use the groundwater sustainably, we could all run out of water during the dog days of summer.
This low spot off Logmill Road took 36 hours to soak in after the last rain.

The water level in a groundwater well usually fluctuates naturally during the year. Groundwater levels tend to be highest in the spring in response to winter snowmelt and spring rainfall when the groundwater is recharged. Groundwater levels begin to fall in May and typically continue to decline during summer as plants and trees use the available shallow groundwater to grow and streams draw water to supplement their flow. Natural groundwater levels usually reach their lowest point in late September or October when fall rains begin to recharge the groundwater again.

The natural fluctuations of groundwater levels are most pronounced in shallow wells that are most susceptible to drought. Older wells in areas near springs and rivers tend also to be shallow, because they were installed before modern equipment in the shallow first aquifer that is immediately impacted in drought. Most modern wells are drilled wells that penetrate about 100-400 feet into the bedrock.  However, deeper wells may be impacted by an extended drought and take longer to recover. In addition, water production in a well tends to decrease over time because sediment builds up in a well. To provide a reliable supply of water, a drilled well must intersect bedrock fractures containing ground water and the natural occurring sediment, minerals and slime producing bacteria can clog those fractures over time. Without a geological event like an earthquake, groundwater changes tend to happen slowly as water use grows with increased population or irrigation and recharge is impacted by adding paved roads, driveways, houses and other impervious surfaces diminishing the water supply over time.

Groundwater and surface water are interconnected, yet the law in Virginia and most of the east coast treats surface water rights differently from groundwater rights. The rights to surface water in Virginia, as well as inmost Eastern states, are allocated based on the riparian doctrine. This rule gives an owner of land bordering on water the right to use that water so long as the use does not unreasonably affect the water available to other riparian land owners. Rights to groundwater, on the other hand, are governed by the American Rule. This permits an unlimited use of groundwater beneath one’s land so long as it is not wasteful and is used in a manner consistent with the use of the land lying above the water even if your water use impairs your neighbor’s well. This potentially leaves groundwater in the eastern states subject to unsustainable use and as our water resource are needed to serve more and more people we need to develop sustainable methods of managing groundwater and the rights to the water.    

Monday, March 25, 2013

Dividing Up the Groundwater in Nevada


In the arid west water has value. Once granted, water rights in Nevada have the standing of both real and personal property and can be conveyed as with the real property or specifically excluded in the deed. Water rights can be purchased or sold as personal property and change the water's point of diversion, manner of use and place of use. Within the Las Vegas Valley,  there are speculators who buy and sell older water rights that are permanent, which means whomever buys them is generally free to pump them from most anywhere else in the Las Vegas Valley.  Unlike the east, where water groundwater belongs to the overlying land and surface water is allocated based on the riparian doctrine that gives an owner of land bordering on water the right to use that water, in Nevada water rights are granted by the State Engineer.  

All water within the boundaries of the state of Nevada,whether above or beneath the surface of the ground, belongs to the public and is subject to appropriation for beneficial use to remote parties. Nevada’s first water law passed in 1866 was based on a system of first users have the first rights to water. The Office of the State Engineer was created by the Nevada Legislature in 1903 to manage the surface waters of the state. It was not until the passage of the Nevada General Water Law Act of 1913 that the State Engineer was granted jurisdiction over wells tapping artesian water or water in definable underground aquifers. The 1939 Nevada Underground Water Act granted the State Engineer jurisdiction over all groundwater in the state.

Now, with almost the entire surface water allocated (and possible over allocated in the recent drought) towns on behalf of local industry and future growth are attempting to lock up water rights and the wealth that goes with it. The town of West Wendover, Nevada on behalf of itself and Wendover, Utah has filed permits to obtain 650 million gallons of water each year from the Pilot Valley groundwater basin after having a previous request for an increase in their allocation from their current groundwater supply denied by the State Engineer. A 1971 federal groundwater study determined that the Pilot Valley groundwater basin could provide 1.5 billion gallons of water annually. This data is old and was produced at a time before groundwater was as well understood as it is today. Even today groundwater sustainability is still not fully understood. In addition, there are droughts, climate changes; water draws from surface water changes the recharge rate of the groundwater and residents of Pilot Valley claim that the prolonged drought has lowered groundwater levels in their wells. If true, this brings into question what the sustainable level of consumption is for this groundwater basin.  

The U.S. Geological Survey did not begin quantitative analysis of the major groundwater systems of the United States until 1978 and since that time there has been tremendous evolution in the understanding of and ability to model groundwater systems. Older attempts to model groundwater systems neglected relevant hydraulic and geological processes as well as representing inappropriate processes and using mathematical simplifications and did not even include a connection to surface water. Clearly, new studies need to be performed before significant water rights are granted. The State Engineer has the authority to require a hydrological, environmental or any other study necessary prior to final determination of an application for water rights.
from SNWA web site

This is not a one-off application for water rights. Throughout the portions of the arid west that allocate groundwater rights communities have been attempting to secure more groundwater rights for their communities and none has been as active as  Las Vegas and the Southern Nevada  Water Authority, SNWA. In light of ongoing drought conditions in the Colorado River Basin and continued population growth, the SNWA continues to seek groundwater rights to an additional 44 billion gallons of non-Colorado River resources groundwater that it can pipe to the city. The State Engineers approval of the applications has been challenged and will be heard in the Nevada Supreme Court. The average Las Vegas house and family uses about 450 gallons of water a day which translates to about 163,000 a year, but the SNWA is engaged in a major water conservation and reuse program to reduce the household use by 199 gallons per day. As SNWA points out for the west to survive, they will have to use significantly less water per person in the future.  The state of Nevada has updated their drought response plan for the first time in a decade as the Colorado River system is facing the worst drought on record. The water level of Lake Mead, the reservoir for Las Vegas has dropped more than 100 feet since January 2000.

Thursday, March 21, 2013

Fix a Leak to Conserve Water




The U.S. Environmental Protection Agency (EPA) has named this week the Annual Fix a Leak Week. For those homes on ”City” water and sewer, a quick check of the status of your plumbing fixtures and checking your water usage indicated on your water bill could save thousands of gallons of water a year. Look for changes or increases in water use as well as calculating your absolute use. If your household uses more water than is typical, you might have a hidden leak, or you could be wasteful in your water use. Find out which. According to the EPA, one out of every 10 homes has a leak that is wasting at least 90 gallons of water per day.

The EPA’s WaterSense program is designed to encourage Americans to check and replace leaky plumbing fixtures and be thoughtful in their water use. This comes at a time when many urban water systems in the United States are nearing or at the limits of their water supply. Even in generally water rich areas there are limits to the availability of water and United States has begun to address the availability of water by recycling wastewater. In the United States municipal wastewater represents a significant potential source of reclaimed water, an estimated 32 billion gallons of water a day is treated in wastewater treatment plants throughout the country. Before recycling wastewater, we should eliminate water waste in our communities.

If like me, you are on well water, you do not have a water bill to track your water use, but you need to be aware of the factors that impact your water supply and regularly practice household water conservation to live within your water resources. Your well is not unlimited and you need to be aware of your water use because wells often have weather and seasonal supply limitations. In addition, the life of a septic system is directly related to the amount of water that flows through your system. All of us need to become aware of how much water we use and where that water is coming from and eliminate the egregious waste of water leaks.

·        Check toilets for silent leaks by putting a few drops of food coloring in the tank at the back and, if after 10 minutes, color shows up in the bowl before flushing, it may be time to replace the flapper.
·        Check outdoor hoses for damage from winter frost and tighten connections at the water source.
·        For in-ground sprinkler systems, a professional (certified through a WaterSense-labeled program) can inspect sprinkler heads and pipes for signs of leakage and help homeowners maintain an efficient system and healthy lawn. (Though you might want to reconsider a lawn that needs regular watering.)
·        Check additional plumbing and outdoor fixtures for leaks. They may just need a quick twist, cleaning or pipe tape. Check all faucets for slow drips.

According to the US Geological Survey total domestic water use in homes totaled 29,400,000,000 gallons per day in 2005, and the “average” US citizen uses 98 gallons a day of water for domestic use, which includes, bathing and bathrooms, laundry, cooking, drinking and outdoor use. Outdoor watering in the drier climates causes domestic per capita water use to increase in the driest and hottest climates. In Nevada, average domestic water use was reported to be 190 gallons/day per person, while in Maine they used on average 54 gallons/ per day. In Maryland average domestic water use was reported to be 109 gallons/day per person while here in Virginia the average water usage was 75 gallons/day per person. Pennsylvania to the north uses an average of 57 gallons/day per person. The US Geological Survey who collected and compiled all this data and the estimates imbedded in them offers no explanation for the differences in domestic water use.  While I believe there are differences in water usage, I do not know the causes of the variation beyond the weather, but the age of the water fixtures can contribute to the differences.

There are tremendous differences in water consumption of appliances and fixtures based on their age and design. For example we all know about low-flush toilets which use 1.6 gallons per flush versus 5 gallons per flush for the older toilets. According to the 2001 Handbook of Water Use and Conservation by A. Vickers and published by WaterPlow Press in Amherst, MA the average person flushes the toilet 5.1 times a day. Before the advent of low flush toilets, flushing was the largest use of water for each person. If you have new toilets and are home all day, your daily water use for flushing would be 8.2 gallons versus 25.5 gallons for an older toilet.

The typical American uses the most water for flushing, showering, washing hands and brushing teeth, and laundry. Buying water efficient appliances and fixtures, maintaining the fixtures and repairing any leaks can significantly reduce our water use. For bathing and brushing teeth low flow faucets and showerheads and behavior modification (not running the water while you brush your teeth or shorter showers can save about a third of the water typically used for personal hygiene, reducing the typical 28 gallons a day to 19 gallons a day. Laundry is the second largest use of water after toilets. The typical American does 0.37 loads of laundry per person per day. A top loading washing machine uses 43-51 gallons per load while a full size front load machine uses 27 gallons per load and some machines have low volume cycles for small loads that use less. Replacing a top load washing machine with a front load machine saves 6-9 gallons of water per person per day or 24 gallons per load of laundry. A standard dishwasher uses 7-14 gallons per load while a water efficient dishwasher uses 4.5 gallons per load. Eliminating the watering of our ornamental gardens would significantly reduce water use especially in the most arid parts of the country where there is the most pressure on water supply. By replacing appliances and fixtures with water efficient fixtures and eliminating outdoor use of water the typical American could reduce their water use to about 38 gallons per person per day without significantly changing their lives. That is a significant water savings that will become more important as water resources in the United States become stretched to their limits.

Monday, March 18, 2013

Hydrogen Sulfide-the Rotten Egg Smell in Well Water


Hydrogen Sulfide gas (H2S) gives water that awful “rotten egg” taste and smell and can be a fairly common occurrence in parts of the country, like Prince William County, Virginia where the groundwater is naturally high in sulfate. This problem can be solved, but let’s back up and start at the beginning. You have to first have sulfate present to have hydrogen sulfide. The EPA guidance for sulfate is 250 ppm for taste, but may be unnoticeable at higher levels, but excessive levels may have a laxative effect. Hydrogen sulfide naturally occurs in shale, sandstone, and near coal or oil fields, but can also be created by sulfur reducing bacteria “eating” the sulfate. According to the EPA, sulfur-reducing bacteria pose no known health risks. Sulfur-reducing bacteria live in oxygen-deficient environments such as deep wells, plumbing systems, water softeners, and water heaters. Often these bacteria flourish in plumbing systems. Sulfate reduction can occur over a wide range of pH, pressure, temperature, and salinity conditions and produce the rotten egg smell and the blackening of water and sediment by the formation of iron sulfide if iron is also present in the groundwater or plumbing system.  

Hydrogen Sulfide gas (H2S) with its characteristic “rotten egg” taste and smell can actually be detected as an off smell at 0.5 parts per million (ppm) by most people. At less than 1 ppm, hydrogen sulfide will give water a musty odor. At 1 to 2 ppm, it will have an odor similar to rotten eggs. Levels encountered in private wells are usually less than 10 ppm, because high levels of gas will not remain in solution in the water. Though toxic and potentially lethal at 800 parts per million after 5 minutes of exposure, the Occupation Safety and Health Administration, OSHA, OSHA has established 10 ppm (20 times the concentration that you can smell it at) as the safe limit. Hydrogen sulfide is heavier than air and can accumulate in pits and basements and can potentially create a health and explosive hazard (though the smell might kill you first). Hydrogen sulfide can be corrosive to metals such as iron, steel, copper, and brass, and it can cause yellow or black stains on kitchen and bathroom fixtures, but the big problem is the smell, the water is undrinkable and unusable with that smell. Some water treatment systems can actually create the problem within the plumbing system, and some water treatment companies that specialize in selling water softener systems for all problems may think that the problem is unsolvable, but that is not true. Most hydrogen sulfide problems can be solved if the correct solution is implemented. So if you smell Hydrogen sulfide in your well water you need to figure out what is going on to correctly identify a solution.

 Hydrogen sulfide can end up in your tap water by four different routes. (1) It can occur naturally in groundwater especially in oil rich shale and coal seams. (2) It can be produced within the well or plumbing systems by sulfur reducing bacteria (bacteria that essentially eat sulfate in areas that have a high natural level of sulfate in the rocks. It is only guessed at how the bacteria enter the well or plumbing system and how associated these bacteria are to the iron and manganese eating bacteria, but these anaerobic bacteria occur naturally in decaying plant material and soil and many areas in the nation have high natural levels of sulfate in the groundwater. (3) Hydrogen sulfide can form in hot water heater by either supplying a pleasant environment for the sulfate reducing bacteria to thrive or the energy for the magnesium rod intended to prevent corrosion of the heating tank to react with the sulfate naturally occurring in the water.  (4) Finally, there are instances where the hydrogen sulfide gas is due to contamination of the well with septic waste.

Because hydrogen sulfate is so easily smelled by the typical human being, just this one time, most (but not all) of the testing will be done by smell. You need to be systematic and frequently step outside the home so that you do not grow accustomed to the smell. First thing is to determine if the smell is coming from the plumbing system or the well system. You will need to smell the water coming out of the hot water faucet and cold water faucet. This is best done at a sink that has a so called widespread or centerset two handled faucet to ensure there is no mixing. Now run the hot water and smell. Note whether there is a hydrogen sulfide smell from that tap. Is the smell constant or does it diminish after the water has run a while, or is the smell variable. Now do the same for the cold water tap. After you finish this go outside and run the hoses and determine if there is hydrogen sulfide smell to that water and whether it diminishes or stays constant. Repeat the process to make sure that you get the same results.

If the smell is only from the hot water faucet and not from the cold water or the hoses, then the problem is in the hot water heater. It is either sulfate reacting with the magnesium anode rod, or sulfur reducing bacteria (flourishing) in the hot water tank.  Unless you are very familiar with operations and maintenance of hot water heaters, you should call a plumber. There is no standard test for sulfur reducing bacteria, so it is difficult to differentiate between a bacteria problem and something that might be solely sulfate reacting with the magnesium. You need to treat the hot water tank for both situations so it is a good idea to chlorine shock the hot water heater to kill the bacteria then flush it. But first start by raising the temperature in the hot water heater to 160 degrees Fahrenheit for three hours. This will generally kill the sulfur reducing bacteria. At this point you might want to flush the hot water heater a couple of times and let it heat back up and see if the problem is gone. This probably won’t last, if iron bacteria are being introduced from the well, but keeping your hot water heater at 160 degrees will constantly kill the bacteria. If you do not want to keep your hot water heater set so high, then move on to disinfecting the hot water heater and replacing the anode rod.

Either turn off the hot water heater if it is electric or put it on pilot if it is gas and drain off a few gallons of water after you close the cold-water inlet valve. Make sure that you have drained off a gallon or so and pour a half gallon of household bleach (5.25% hypochlorite) into the tank. Use either the temperature and pressure valve, anode rod opening, or hot water outlet pipe opening to pour the chlorine into the hot water heater. Let the chlorine sit in the tank for at least two hours. Then open the cold-water inlet valve, drain the hot water heater and turn the heat back up. If the problem is sulfate reacting with the magnesium anode (corrosion protection rod), it can be replaced with an aluminum rod that is not as reactive as the magnesium and may still serve to protect the metal components of the tank from corrosion. Most hot water tanks take a standard size anode rod and there are aluminum replacements available from several manufacturers. Generally, you should check the condition of the anode rod when you pour the bleach into the tank. Be aware that some high end tanks have two anode rods and replacing just one with aluminum will not solve the problem because the remaining magnesium rod will continue to react with the sulfate.  

If the hydrogen sulfide smell is in both the hot water facet and the cold water faucet, but not from the hoses, then the problem is likely to be sulfur reducing bacteria in the plumbing system (after the pressure tank). Sulfur reducing bacteria just love to live in water softeners. If there is a water softener in the house, first consider removing it. Water softeners are often installed as an expensive fix for a mild iron and manganese problem. High concentrations of dissolved hydrogen sulfide can foul the resin bed of an ion exchange water softener. When a hydrogen sulfide odor occurs in treated water (softened or filtered) and no hydrogen sulfide is detected in the non-treated water (the hoses), it usually indicates the presence of some form of sulfate-reducing bacteria in the system. Water softeners provide an environment for these bacteria to grow. These “salt-loving” bacteria, that use sulfates as an energy source, may produce a black slime inside water softeners. If you have modest sulfate, but no rotten egg smell, installing a water softening system may create additional problems, especially if the system is not meticulously maintained. The first solution is to get rid of the water softener. Test your water to see how hard it actually is. If your water softener was really intended to solve an iron and/or manganese problem then it could be replaced with an oxidizing greensand filter which can be used to remove iron (with water with pH above 6.7) manganese and hydrogen sulfide. If your water is so hard that you cannot live with it, then you will have to disinfect the water softener (according to manufacturer recommendations or the instructions available from Minnesota Extension) and meticulously maintain and disinfect the water softener in the future.

If the hydrogen sulfide smell is strong when the water in either faucet is first turned on and then seems to go away after the water has run a while, then it is probably sulfur reducing bacteria in the well system or plumbing system. If the hoses do not have any hydrogen sulfide smell than the bacteria is in your plumbing system otherwise the bacteria is in the well or both the well and the plumbing system. When the hydrogen sulfide smell and taste problem is caused by the presence of sulfate and sulfur-reducing bacteria in the well or plumbing system then shock chlorination using a high dose of chlorine and sufficient contact time to kill the non-pathogenic iron, manganese and sulfur reducing bacteria which can be difficult to kill because of the associated slimy secretion. Effective treatment requires sufficient chlorine strength and time in contact with the bacteria. Though you typically use a chlorine concentration of 200 parts per million for decontamination of a well, a higher concentration is recommended for sulfur (and iron) reducing bacteria. Recommended concentrations are between 400-1,000 parts per million. Be warned that high concentrations of chlorine may affect water conditioning equipment, appliances such as dishwashers, and septic systems. You may want to check with the manufacturer of the appliances before chlorinating and be careful to drain as little as possible to the septic system. If you do not want to treat your well yourself, hire a well driller to disinfect the well. Be sure to tell them that you need about 4 times the usual amount of chlorine and do not need confirmation testing. (Typically well drillers do this for coliform bacterial contamination.) If you want to do this yourself, I like the instructions from either Minnesota or Virginia. Detailed instructions to calculate the amount of chlorine bleach to use and the steps to take to treat the well are available from either state, but Minnesota includes instructions for water softeners and other water treatment systems).Remember to use 4 times the chlorine they suggest for the initial well treatment since these are the instruction for the less persistent coliform bacteria.  

If the hydrogen sulfide smell is strong in the hoses and the hot and cold water faucets and remains fairly constant with use, then the problem is probably hydrogen sulfide gas in the groundwater.  As mentioned above, the oxidizing greensand filter can be a very effective solution for water that has both iron and manganese, or iron and hydrogen sulfide odor, or iron reducing or sulfur reducing bacteria. The pH of the water needs to be close to neutral (above 6.7-7) for a greensand filter to work, so now would be a good time to test the well water for iron, manganese, hydrogen sulfide, and coliform and E. coli bacteria. It is important to understand the quantities of hydrogen sulfide and to make sure that the well has not been contaminated with sewage waste. For higher levels of hydrogen sulfide injecting an oxidizing agent, like chlorine,before the pressure tank followed by an activated carbon filter can solve both a hydrogen sulfide problem and an iron problem. Generally, these systems should be installed by professionals and confirmation testing performed.  

Thursday, March 14, 2013

Curiosity finds the Elements Necessary for Life

Rocks in Yellowknife Bay, Mars

On March 12, 2013 NASA announced that the Curiosity rover's on-board laboratory instruments, Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments, has detected the chemical building blocks of life on Mars. NASA scientists have found sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon near an ancient stream bed in Gale Crater on Mars last month. The data indicate the Yellowknife Bay area the rover is exploring was the end of an ancient river system or an intermittently wet lake bed that could have provided chemical energy and other favorable conditions for microbes.

On August 6th 2012 at 1:32 am (eastern time) the Curiosity rover, a large mobile laboratory, was set down on Mars inside the Gale Crater by NASA’s Mars Science Laboratory, MSL, beginning a two-year investigation of Mars. The rover was designed to analyze samples scooped from the soil and drilled from rocks. The record of the planet's climate and geology is essentially "written in the rocks and soil" -- in their formation, structure, and chemical composition and this Mars mission is designed to unveil some of those secrets.  After the delays in the mission at year end, it is amazing that this discovery was made so early in the mission.

Curiosity carries a radioisotope power system that generates electricity from the heat of plutonium's radioactive decay. This power source gives the mission an operating lifespan on Mars' surface of a full Martian year (687 Earth days) or more and hopefully be able to gather enough data to assess what the Martian environment was like in the past. 

The rock analyzed so far is made up of a fine-grained mudstone containing clay minerals, sulfate minerals and other chemicals. This ancient wet environment, unlike some others on Mars identified in previous Mars missions, was not harshly oxidizing, acidic or extremely salty. According to Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington these findings are evidence that Mars could have once supported a habitable environment for microbial life.

Rover Path on Mars
In addition to sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon scientists were surprised to find a mixture of oxidized, less-oxidized, and even non-oxidized chemicals, providing an energy gradient of the sort many microbes on Earth exploit to live. This partial oxidation was first hinted at when the drill cuttings were revealed to be gray rather than red. 

Monday, March 11, 2013

Global Temperatures for 11,300 Years


On Friday the Journal Science published a peer reviewed paper by Shaun A. Marcott, of the College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Jeremy D. Shakun, of the Department of Earth and Planetary Sciences, Harvard University, and Peter U. Clark and Alan C. Mix also of the College of Earth, Ocean, and Atmospheric Sciences, Oregon State University “A Reconstruction of Regional and Global Temperature forthe Past 11,300 Years.” The authors lead by post-doctoral researcher Shaun Marcott used existing data from 73 records from multiple paleoclimate archives and 22 temperature proxies to create a reconstruction of global temperatures back to the end of the last Ice Age in order to view today’s climate conditions in a larger context during the Holocene period, the time of man. The last ice age is currently believed to be the eighth ice age during the last million years.

Drs. Marcott, Shakun, Clark and Mix’s research shows that over the past 5,000 years, the Earth on average cooled about 1.3 degrees (Fahrenheit) – until the past 100 years, when it warmed about 1.3 degrees (F) bringing the average global temperature back to the previous level. The largest temperature increase changes were in the northern hemisphere, where there are more land masses and greater human populations.
Figure taken from Dr. Marcott et als paper

The scientists did not take any new samples, but used existing core samples to derive age primarily with carbon 14 dating of organic material; and tephrochronology or annual layer counting were used where appropriate. These methods are the current established and accepted scientific procedure. They recalibrated the radiocarbon data of the original studies (some of which were decades old). The basic methology for determining surface temperature in the past depends on extrapolation of information from core samples. In ice cores drawn from glaciers, oxygen isotopes are measured and can be used to infer the temperature at the time when the snow was originally deposited. The isotopic composition of the ice in each layer reflects both the temperature in the region where the water molecules originally evaporated and the temperature of the clouds in which the water vapor molecules condensed to form snowflakes. The temperature can thus be inferred from the data.  

Data sets from cores taken from the sediments at the bottoms of lakes and oceans followed the original authors’ suggested values. Sediment cores can be analyzed for oxygen isotopes, the ratio of magnesium to calcium, and the relative abundance of different microfossil types with known temperature preferences (such as insects) or with a strong temperature correlation like some algae to determine the temperature of the water. This in turn, can be related to the local surface temperature. Beyond 2,000 years there was a higher level of uncertainty in the age of the samples. To account for that uncertainty, the authors used a Monte Carlo simulation. The uncertainty between the age-control points was modeled as a random walk. For the layer-counted ice-core records, they applied a ±2% uncertainty for the Antarctic sites and a ±1% uncertainty for the Greenland site.

According to Peter Clark, “When you just look at one part of the world, the temperature history can be affected by regional climate processes like El NiƱo or monsoon variations, but when you combine the data from sites all around the world, you can average out those regional anomalies and get a clear sense
of the Earth’s global temperature history.”

We already knew that on a global scale, Earth is warmer today than it was over much of the past 2,000 years,” Dr. Marcott said. The new study, shows that the earth average temperature is still within the high point before the “Little Ice Age,” but as can be seen on the graph below warmer than most of the past 11,300 years. This period of time, the Holocene, spans the entire period of human civilization. “The Earth’s climate is complex and responds to multiple forcings, including CO2 and solar insolation,” Marcott said. “Both of those changed very slowly over the past 11,000 years. But in the last 100 years, the increase in CO2 through increased emissions from human activities has been significant. It is the only variable that can best explain the rapid increase in global temperatures.”
taken from Dr. Marcott et al 's paper

Thursday, March 7, 2013

Sinkholes

from Sinkholes, West-Central Florida USGS

Sinkholes can vary from small shallow depressions in the earth to holes that are hundreds of feet deep and cover hundreds of acres. Some sinkholes even hold water and form natural ponds and lakes. Typically, sinkholes form so slowly that little change is seen in one's life- time, but they can form suddenly when a collapse occurs. Such a collapse can have a dramatic and devastating effect if it occurs in an urban or suburban setting as recently happened in Hillsborough County near Tampa, Florida when a sinkhole opened beneath a house swallowing a man and his bedroom. The body was never recovered and the house was demolished. Western central Florida has a long history of sinkholes and because of geology and groundwater pumping is  particularly susceptible to sinkholes. In the water well fields for St. Petersburg located in Hillsborough County and surrounding counties sinkholes have occurred in conjunction with development of each of the well fields as well a throughout the region. Sinkhole formation is highest during dry months of the year and during drought, but overall appear to be increasing in frequency according to the U.S. Geological Survey, USGS, though there might be some reporting bias to the data.   

A landscape that forms sinkholes, sinking streams, caves, and springs is called a karst landscape. A karst landscape most commonly develops on limestone, but can develop on several other types of rocks, such as dolostone (magnesium carbonate or the mineral dolomite), gypsum, and salt, which are types of evaporates rocks. Rain is naturally mildly acidic, and slowly over time the weakly acids rainwater dissolves these deposits creating fissures. The deposits are highly permeable, and surface water passes through them quickly to underlying aquifers, eating away at the limestone and evaporates bedrock. Overtime this creates the voids that become sinkholes. There are three general types of sinkholes: dissolution sinkholes—depressions in the limestone surface caused by the erosion of limestone by rain; cover-subsidence sinkholes—formed as overburden materials gradually fill below surface fissures formed by the infiltration of rain; and cover collapse sinkholes—which occur in limestone terrain with a thick overburden or mantle after the fissures forms large cavities and the cover materials collapse into the subsurface voids. This third type of sinkhole is what occurred last week near Tampa.

Hundreds of collapse sinkholes of various sizes occur throughout the country each year and start unnoticed when infiltrating water or groundwater flowing in the subsurface creates a void where soil is washed away. Eventually the void or hole grows large enough that the soil above it can no longer bridge it. The soil bridge then suddenly collapses into the void below and a sinkhole forms. Often this happens when the water level that has been exerting an upward pressure- helping to hold up the soil bridge falls. This process usually takes many years to occur in nature, but it can be aggravated by human activities. Any activity that increases the amount of water flowing into the subsurface can speed up this process. Parking lots, streets, altered drainage from construction, irrigation, leaking swimming pools and roof guttering are some things that can increase runoff; even severe weather can cause sinkholes.
The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania thought large areas of the United States are underlain by evaporates rocks (salt, gypsum, and anhydrite) and carbonates (limestone and dolomite), the rock types that are most susceptible to being dissolved away by water. Even when evaporite rocks are buried at great depths, in so called Mantled Karst terrain sinkholes can form. These sinkholes are the most sudden when the mantle give way. The western central portion of Florida is an area of Mantled Karst terrain, but most of Florida is prone to sinkhole formation because it is underlain by thick carbonate deposits and is so rich in groundwater. Development and overuse of the groundwater resources for municipal, industrial and agricultural water supplies has resulted in falling groundwater levels that play a role in sinkhole formation as well as development.

According to Ann B. Tihansky of the U.S.G.S. in Tampa and author of Sinkholes, West-Central Florida,“Induced sinkholes are generally cover-collapse type sinkholes and tend to occur abruptly. They have been forming at increasing rates during the past several decades and pose potential hazards in developed and developing areas of west-central Florida. The increasing incidence of induced sinkholes is expected to continue as our demand for groundwater and land resources increases. Regional declines of ground-water levels increase sinkhole occurrence in sinkhole-prone regions.” The sinkhole prone regions of the country can be seen below.All of Florida is karst terraine, but as can be seen below karst terrain also covers much of the Valley and Ridge Province of Virginia in the western third of the state. Small karst areas occur in the Cumberland Plateau, Piedmont and even the Coastal Plain provinces.


From USGS
If you have questions or worries about sinkholes, settling or earth movement in your yard, Florida has an excellent question and answer web site. 

Monday, March 4, 2013

Water, Food and Hunger-Feeding Mankind



Today, agriculture uses 11 % of the earth’s land surface about 1,527 million hectares or 3.78 billion acres for crop production. In addition, agriculture uses 70% of all the water withdrawn from aquifers, streams and lakes, but it is not really known what percentage of sustainable water use this represents. Mankind has been unable to fully quantify either groundwater use or renewable water availability.  During the past half century the world’s agricultural production has grown between 2.5 and 3 times while the cultivated land area has grown only by 12%. This feat is often called the agricultural miracle or “Green Revolution” and was accomplished by doubling the areas of land that were irrigated. Fertilization, pesticides, hybrid crops and mechanized agriculture have also contributed to rapid increases in agricultural productivity and yield.

The U.N. forecasts that world population will continue to rise and grow from 7 billion people today to more than 9 billion in 2050. The Food and Agriculture Organization of the United Nations forecasts that in order to adequately feed 9 billion people, a 70 % increase in food production that will have to take place globally by 2050. There are reported to be 923 million people who are inadequately fed today and tremendous loss due to spoilage in the global food supply (30%).  The rate of growth in agricultural food production has been slowing. In developing countries the growth rate is 1.5% half the growth rate of the past, still adequate to meet the projected food need if sustained, but the distribution of land and water resources does not match the forecasted need. According to the U.N. the available cultivated land per capita in low-income countries is less than half that of high-income countries, water resources are less abundant and the suitability that land for agriculture is generally lower.

Both irrigated and rain fed agriculture will have to respond to rising populations, but the key to food security is water and diet. According to the Food and Agriculture Organization of the United Nations doubling of current food production could be derived from already developed land and water resources, but might require a changing world diet especially in the developed world that would need to supply more food to the poorer nations by reducing the amount of animal protein in the developed nations’ diet.  Using “conventional irrigated agriculture” it takes 420 gallons of water to produce one pound of rice; 1,800 gallons of water to produce one pound of beef; and 40 gallons of water to produce a cup of coffee. The dietary shift towards animal protein as nations become richer has increased world water consumption over the past 30 years.

Some land and water resources could be diverted to crop production, but in most cases this shift could have significant negative environmental and economic impacts. Increased water scarcity, loss of biodiversity and environmental services, desertification, expected reduction in water availability and some shift in seasonal flows is forecast to result from climate change in several places. Many rivers that serve as large contiguous irrigation systems in dry areas of the earth run dry from overuse before they reach the oceans.  These, including the Colorado river, Murray-Darling (Australia), Krishna, Indo-Gangetic plains, Northern China, Central Asia, Northern Africa and Middle East are forecast to become more stressed. Groundwater-dependent irrigation systems in interior arid plains: India, China, central USA, Australia, North Africa, Middle East and others are using groundwater beyond their recharge rate. In some regions the groundwater aquifers were created a millennium ago when the earth’s climate was vastly different. In others the aquifer has simply been depleted by unsustainable use with the subsequent loss of buffer role that groundwater aquifers normally play seasonally or in drought years. The U.N. Food and Agricultural Organization already warns that agricultural water already is being allocated to other uses such as municipal supplies, environmental reserves and hydropower generation and removed from irrigation.

There are now proportionately fewer malnourished people in the world than there used to be (though the absolute number, 923 million, is extremely large). An emerging problem is food and diet quality. More calories do not mean better health. Over 87% of world’s population obtains enough calories and a growing portion of the world obtains too many calories, but many suffer nutrient deficiencies, especially in four nutrients: iron, zinc, iodine and vitamin A. In addition, there is growing evidence that over reliance on grains and processes food is having a negative impact on population health. Obesity is spreading from rich countries to less well-off places: Mexico has the second-largest share of obese people after the United States; Guatemala's obesity rate has quadrupled in 30 years yet, a large group of people in these countries suffer from nutritional deficiencies.

According to the National Institute of Health, research studies in the United States and Europe show that celiac disease is significantly more common now than it was a few generations ago. Scientists found that found that in the United States celiac disease is four times more common today than it was 50 years ago. According to Joseph Murray, M.D., professor of medicine at the Mayo Clinic in Rochester, MN, and a researcher into celiac disease the most likely factor is a change involving the quantity and quality of grain in our diets. “Consumption of wheat has increased steadily over the past 50 years, but it still is less than what it was a century ago, so the issue is not simple consumption,”; Dr. Murray noted. “It more likely involves the wheat itself, which has undergone extensive hybridization as a crop and undergoes dramatic changes during processing that involves oxidizers, new methods of yeasting, and other chemical processes. We have no idea what effect these changes may have on the immune system.” This is not a model of agriculture and diet that can hope to feed a robust species.