I want the notes of Ground Water Hydrology of Visvesvaraya Technological University VTU so can you please provide me?

Water Well Installation.
• Wells can be augured, drilled, driven or jetted.
• Augured wells are of limited depth and can only be used in unconsolidated materials.
• Driven wells can be in harder materials but limited depth
• Jetted wells in unconsolidated materials.
• Drilled wells can very deep and drilled in hard rock can be air rotary or reverse rotary using a drilling mud.

Factors affecting choice of drilling method:
• Choice depends on aquifer material and depth, also available money.
• Jetted & augered are cheapest methods work only in shallow unconsolidated materials.
• Driven is next cheapest, works in shallow consolidated.
• Drilled works in more difficult conditions.
Variations on drilled wells.
• Drilled wells use a rotary bit but the variations involve how cuttings are removed.
• Can be air rotary or a mud system.
• In a mud system a slurry of water and bentonite is used.
• Method is also common one in oil and gas industry, where deeper wells are norm.

Depth of wells:
• Most groundwater is obtained from wells less than 500 feet deep and almost all wells are less than 2,000 feet deep.
• Exceptions: arid and semiarid areas with large up-lift.

Well logs
• As the well is being drilled a geologist should note the texture and other characteristics of each layer and prepare a well log.
• This is frequently required to be filed along with other information to a State Engineer or water development board.

Geophysical methods:
• Also, various geophysical techniques can be used to get further information. These include:
• Neutron log: (looks for hydrogen) can be fooled by clay.
• electric (resistively) log: wet soil is more conductive than dry soil.
• Measure both water content and porosity. Each is fallible so both are combined.
• Well loggers: the lonesome cowboys of the well business.

Well tests:
• Once a well is installed and developed it is typically tested.
• Hydro-geologists spend a lot of their time in the field performing well tests.
• The basic tests are pump tests.
• There are also slug tests

Pump Tests:
• A graph of time pumping rate and time versus draw-down are developed to estimate safe yield of the well. A monitoring well (or more than one) can be a very useful part of this.

Give me a slug of that:
• A slug test Can also be performed to estimate hydraulic properties of the formation.
• A known quantity of water is pumped into the well and the rise and fall in water levels are recorded.

Water Well Development:
• Once a well has been drilled and casing set the well must be developed.
• This is accomplished by pumping the well to remove silt and sediment inside the casing then using a surge block or compressed air hose to push sediment out of the slotted screen and into the gravel pack.

Water quality testing:
• Water quality should be determined after the pump test is complete.
• Some characteristics can be determined in the field some require laboratory analysis.

Field parameters:
• Temperature,
• Conductivity.
• pH.
• Dissolved oxygen
• Also taste and odor.
Lab parameters:
• TDS,
• Hardness,
• Alkalinity,
• pH.
• D.O.,
• General minerals: Na, Cl, Mg, Fe, Ca, Mn,
• HCO3, H2CO3, SO4, SO2.

Advanced lab analysis:
• required if contamination is suspected or for public water supply wells:
• Many other tests can be conducted for trace elements, anthropogenic contaminants, radioactivity and pathogenic organisms. These are expensive and generally unnecessary.

Water Well Operation:
• Once installed water levels must be monitored to avoid too much draw-down. Or reduced yield.
• Water cannot be pumped continuously, so storage tanks are needed.
• Also flow must be adjusted to required water delivery rate and pressure.
• The more demand varies, the larger the tanks needed.

Ongoing well operation requires::
• Water may need to be analyzed at least quarterly for water quality.
• Water may need treatment after it is pumped out of the ground this includes:
• Aeration, chlorination, softening, RO, and other treatment.

Water Well Maintenance
• If water has too much air in it may be cascading.
• Over aeration can promote growth of iron and manganese oxidizing bacteria that form a slime that gunks up a well. Chlorination is needed,
• Well components may need to be oiled and cleaned periodically. Bearings and impellers wear out.

Well failures:
• Casing can blow-out requiring pulling the casing and resetting it.
• Wells can sand up or screen or gravel pack can get clogged (re-develop well).
• Down hole Video now more common.
• Insects (ants particularly) can get in wells.
• If air bladder tank is used the bladder may need to be replaced.

Water system problems related to groundwater:
• Hard water will cause scale, so softening and de-scaling with salfamic acid may be needed.
• Soft water corrodes pipes so silicon may be added.

Water Well Abandonment.
• If a well is no longer needed it must be properly abandoned.
• This requires pumping cement into the well or dropping bentonite grout down it. The upper 10 feet of casing should be removed and a hole out at least 5 feet filled with cement.
• The location of the abandoned well should be recorded.
• Improper abandonment of wells (particularly oil and gas) in a huge environmental problem in Texas.

Why abandonment is important:
• Toddlers can fall into well
• Well can be a conduit for movement of contaminants in surface into aquifers (Ralph Grey Superfund site) Monitoring Well Location.

Lec.24 Groundwater Contamination

Significance of groundwater contamination
• Worldwide problem
• Major issue at superfund sites, landfills and many other locations
• Billions of dollars in costs
• Thousands of suspected cancer deaths and birth defects.


Extent of groundwater pollution:
• Over 1 million LUST sites.
• Millions of anaerobic septic systems in poorly draining soils (a major problem in Texas),
• 20,000 plus solid waste landfills, most not built in compliance with RCRA.
• 3,000 + hazardous waste sites, 1,200 on superfund list.

Sources of groundwater contamination
• Hazardous waste sites
• Landfills
• LUST
• Industrial facilities
• Non-point source
Hazardous waste sites

• Organic chemicals including cancer causing and highly toxic compounds seep into groundwater from thousands of sites.
• The number of uncontrolled hazardous waste sites is declining.

Old dumps/landfills a legacy of pollution.
• Most of the 20,000 plus dumps existing in 1976 are now closed but their legacy will continue for decades in form of groundwater pollution and wasted land.
• Example: Henderson landfill
• Can old dumps be reused: Yes for parks, golf courses and buildings.
• Example: Cave Creek County Club.

LUST:
• LUST stands for Leaking Underground Storage Tanks (also LUFT) with over 4 million tanks mostly holding fuel oil or gasoline many tanks or associated piping have leaked(estimated at 1/3). Usually LUST is first a groundwater contamination problem but due to discharge of aquifers this can get in surface water.
Industrial facilities

• Many industrial facilities have contaminated groundwater.
• Most contamination due to losses from pipes and tanks of chemicals, solvents and hydrocarbons.
• Oil refineries have the worst record.


Non-point source

• Agricultural use of pesticides can contaminate groundwater particularly in shallow sand aquifers like Long Island.
• Also nitrites derived from animal wastes is a major problem for rural wells near feedlots.



Behavior of groundwater contaminants
• Movement and dispersion
• Behavior of “conservative” contaminants
• Behavior of LNAPL’s
• Behavior of DNAPLS
• Other types of contaminants

Movement and dispersion
• Contaminants move downward under force of gravity and spread down gradient with groundwater flow.
• As contaminants are transported they are spread-out dispersed and absorb on soil materials to a greater or lesser extent.
• Some contaminants can also volatilize.

Behavior of “conservative” contaminants
• These contaminants such as chloride, nitrite or tritium (a radioactive substance) move at the same rate and in the same direction as the groundwater,

Behavior of LNAPL’s
• Light non-aqueous phase liquids like gasoline, benzene, jet fuel will float on the water table.
• The shape of the plume is a pancake.
• A dissolved phase moves into the groundwater gradually.
• Most of the gasoline is likely to be absorbed to the soil as a residual saturated phase.

Behavior of DNAPL’s
• Dense non-aqueous phase liquids such as TCE and other chlorinated solvents will sink rapidly.
• They pass through the water table and settle on aquitards.
• A portion of the plume dissolves into the water gradually.

Other types of contaminants
• Nitrites
• Pesticides
• Landfill leachate
• Heavy metals
• Radio-nuclides


Lec 25. Groundwater Contamination:
Monitoring and Remediation.

Well-head protection:
• This refers to a program of controlling landuse and remediation and survey of contamination to safeguard wells. Frequently it is combined with an aquifer vulnerability analysis.
• GIS is a useful technology
• Controlling landuse is difficult since serving as a recharge area does not generate profits for the local landowner.


How is groundwater protected:
• Most groundwater protection is indirect (clean water act (CWA), & RCRA) but Underground Injection Control Program (UIC) program provides direct protection.
• Shallow injection wells illegal.
• Dumping liquid hazardous wastes in landfills is illegal.
• LUST is controlled.

Monitoring Wells.
• Designed to provide info on status of aquifers, not to supply water.
• May or may not be capable of being pumped.
• May be designed for monitoring of contamination or yield of aquifers or sometimes for other purposes.

Monitoring Well Location:
• Locate to detect contamination.
• Typically at least one up-gradient and three down- gradient. More for non-point source.
• Provide access for monitoring personnel
• Try to monitor the potential source of contamination not con founding sources.
• Access to other properties can be a problem.
• Example: Henderson Landfill wells.


Monitoring Well Design
• Diameter usually narrow 1-4 inch
• Depth should be down to aquiclude or lower for DNAPLs.
• Screened above capillary fringe.
• Can also monitor soil gas but soil moisture requires use of a suction lysimeter.

Sampling a monitoring well:
• Usually have no pump.
Samples collected by bailer.
• Or sometimes a surface peristaltic pump system
• A “popper” or tape is used to determine depth to water (water level).


Monitoring Well Installation.
• Usually augured but can be driven for a temporary sampling event (Geoprobe).
• Drill cuttings are a solid Hazardous waste
• Pump and development water is a liquid haz waste.
• Slug tests are common to avoid generating waste.
• Cap must be locked and identify well.
• Grouting is very important.

Monitoring Well Development:
• Monitoring wells are generally not developed.
• If they become plugged compressed air is usual approach.

Monitoring Well Operation.
• A bailer is used to obtain a sample.
• Since water in formation, not in well is desired three well volumes are pumped out with an external pump or temporary submersible pump.
• Water samples should be sealed as soon as possible.

Pumped Monitoring Wells:
• Flow through testing of EC, DO, pH Temp is possible.

Other Monitoring methods:
• TLC meter is easy and standard.
• Down-hole video.

Water Level Monitoring.
• Tape
• Popper
• Pressure transducer.





Monitoring Well Maintenance.
• Monitoring wells are only used occasionally (usually every 3 months) but they can get slime like other wells so may need chlorination.


Monitoring Well Abandonment
• Since monitoring wells are in locations that may be contaminated abandonment is even more important than for other types of wells.

Groundwater remediation
• Assessment
• Modeling
• Design and installation
• Operation
• Monitoring
• Closure.

Assessment

• Assessment is an initial step includes using aerial photography, land-use history and other documents to assess type and magnitude of contamination.
• Existing wells and springs may be sampled.
• Shallow soil cores and soil gas samples may be taken.

Monitoring

• Involves installation of dedicated monitoring wells.
• Logging cores and analysis of deeper cores
• Periodic sampling of wells following pumping to assess aquifer conditions
• May also involve slug or pump tests

Modeling

• Requires data from soils, recharge, depth, aquifer transmissivity and any boundary conditions to be known.
• Type of contaminant, magnitude of release, source and duration of release.
• Model used is finite difference or finite element of stochastic.
• 3D visualization is now more common.



Design and installation
• Once extent and transport of contaminant and character of aquifer is know a remedial design can be made.
• Requires installation of treatment system and frequently wells dedicated to pumping contaminated groundwater to treatment system
• System must be monitored and modeled.

Operation

• System may need to be operated for years or decades with periodic monitoring and revision to simulation models to reflect observed changes in contaminant plume.
• Some sites can be definitively cleaned some may need to have long term monitoring following active clean-up.

Closure.

• If monitoring reveals that plume has been abated then site may be “closed” with no further action required.
• Many sites that remain “open” still can be used for other activities but access to treatment systems or monitoring wells must be maintained.

Remediation methods
• Monitoring/natural attenuation
• Pump and dispose
• Pump and treat by air stripping
• Pump and treat by aqueous carbon filtration
• Air sparging/bio-venting
• In-situ enhanced bio-remediation
• Use a 57 chevy…

Monitoring/natural attenuation
• Least costly alternative merely monitor and model plume and show that due to dispersion, absorption and bioremediation the concentration of contaminants will be diminished below action levels prior to reaching wells, springs, etc.
• Mostly limited to LUST sites in some “industry friendly” states.

Pump and dispose
• Install sufficient pumping wells to intercept plume and remove plume at source.
• Pump contaminated groundwater to surface and store and test.
• Either haul away with tanker truck
• Or dispose to sanitary sewer (requires NPDES) permit and permission.

Pump and treat by air stripping
• Send extracted water to tower where volatile components are separated.
• Volatile components may then be burned or absorbed on activated carbon.
• Limited to solvents like TCE
• Requires permits for possible air emissions.

Pump and treat by aqueous carbon filtration
• Pump contaminated water to a series of 3 or more drums that contain activated carbon.
• Drums are placed in series, flow of contaminants from 1st drum n series is tested for when contaminants seep from 1str drum it is replaced by 2nd and a clean drum added at end.
• Works well for small volumes of highly contaminated water
• Limited to gasoline, spent carbon is shipped to be recycled.

Air sparging/bio-venting
• Air is bubbled down into well or pumped into contaminated soil.
• This flushes volatile contaminant up through and out of the aquifer.
• Works for TCE near surface and for residual gasoline contamination of soil
• Creates air pollution possible explosion hazard,
• Works badly in clay soil, well in sand,

In-situ enhanced bio-remediation
• Aerated water, nutrients such as P and N and sometimes selected microorganisms are pumped into contaminated groundwater.
• Slow process, works well for jet fuel and diesel.
• Works badly for TCE, benzene.
• Works well in sandy soil, poorly in clay soils.

Use a 57 chevy…
• Pump contaminated groundwater to surface
• Separate volatile fraction pipe to a running internal combustion engine. Vapors supplement gasoline running engine, burn off and go through exhaust system of car.
• Works for recent shallow gasoline contamination.
• At refineries slurped gasoline is just sent back to be re-refined.


Lec 26 Groundwater Flow & Darcy’s Law

Heads:
• Head refers to a height above some reference level.
• Head differences are the driving force causing groundwater flow.
• Water flows from higher to lower head.

Driving Force:
• Since elevated things have more potential energy than lower ones, head relates to the gravitational potential energy which is a driving force for flow.
• In a water table aquifer, the head is the elevation of the water surface above sea level.
Heads above the rest:
• The difference between the top of the water table at one point and at another point is a head difference in a water table aquifer.
• In confined aquifers, pressure differences rather than the elevation differences are what cause head differences.

Gradients:
• The head difference divided by the distance between the measuring points (“rise over run”) is a slope called a
Gradient.
• All water tables have a slope, usually a small one.

Flow is Down Gradient:
• Groundwater will flow from an area of higher head to an area of lower head (just as surface water flows downhill).
• The steeper the slope, the faster the flow.

Hydraulic Conductivity:
• Aquifers transmit water. The speed at which water flows in an aquifer is the hydraulic conductivity.
• Since hydraulic conductivity is a velocity, its units are distance divided by time.

Units of HC:
• The most common units for HC are CM/SEC. Also M/day, Ft/Day.

Ranges for HC:
• Highly permeable formations may have HC as high as 10-2 cm/sec or several hundred feet per day while typical numbers are on the order of 10 -5 cm/sec and can be as low as 10 -10 cm/sec or less.
• The higher the HC, the faster water will flow through the formation and Caterus Paribus the more water the formation can yield to a well in a given period of pumping.

Tortuosity…
• A measure of how much torture devices hurt you…

This material is torture:
• Groundwater does not flow in a straight line; it follows a twisting tortuous path around particles.
• The property of the porous media that causes this complex path is the tortuosity.
• A clay aquitard has a higher tortuosity than a sand aquifer.

Get out of here…
• Dispersion is the process where by flow through porous media is spread out.
• Dispersion is important, since it is what causes contaminants to spread out into a plume as they are carried along with water through an aquifer.
• The larger the tortuosity the greater the dispersion.

Groundwater Flow-Nets:
• In an entire aquifer, the complex pattern of flow gets equalized and flow can be assumed to follow straight paths, perpendicular to the contours of the groundwater table elevation.

Stream-lines:
• The reason these flow lines are perpendicular to the groundwater elevation contours is that the elevation is a measure of the force (gravity) that is driving the flow.
• So if one can draw a groundwater contour map, one can determine the direction of groundwater flow.

Groundwater Flow & Topography.
• Often information to draw groundwater contours is absent.
• A single well allows a point to be drawn, two a line, three a plane, so at least four wells are needed for contours.
• However, groundwater is recharged from infiltrating soil moisture and from streams and lakes.

Implications:
• So areas with higher elevations have higher groundwater tables. Also, streams and ponds are usually in contact with the water table, at least during base flow conditions.
• So if depth to groundwater is known, topography can be used to estimate (map) groundwater contours.

Groundwater Velocity (Darcy’s Law)
• The rate at which groundwater will flow through an aquifer is the hydraulic conductivity it is estimated by use of the single most important equation in groundwater hydrology
• Fortunately Darcy’s law is a simple one.

Darcy’s Development:
• Darcy’s law was developed in the 1850's by a French engineer experimenting with flow of water through sand filled pipes (an early water purification technique).

Factors effecting Darcian velocity.
• Three factors determined the rate (velocity) of flow.
• 1) The slope of the pipe,
• 2) The diameter of the pipe,
• 3) The permeability of the sand.

More about these factors:
• In an aquifer the slope is the hydraulic gradient (slope of the water table). ).
• In an aquifer the cross-sectional area is the equivalent of the diameter in a pipe.
• In an aquifer the hydraulic conductivity is the measure of permeability.

So…
• In an aquifer flow is equal to the hydraulic conductivity times the hydraulic gradient times the cross-sectional area.

Some (ugh) Math:
• Mathematically, Darcy’s law is:
• Q = KIA
• Where Q = rate of flow
• K = Hydraulic Conductivity
• I = Slope
• A = Cross sectional area.

Units for Darcy’s law:
• If Q = cubic meters per second, then K must be in meters per second, A in square meters (I is a unitless quantity: a 1% slope would be .01).



Transmissivity:
• Hydraulic conductivity is a measure of how much flow in a small part of an aquifer.
• However, aquifers are not of uniform, they have variable HC, gradients and cross sectional area.
• A more useful measure for a real aquifer is Transmissivity.

Definition of Transmissivity:
• This is the quantity of water that a given aquifer can transmit. It is the average hydraulic conductivity times the average thickness of the aquifer.

Estimating transmissivity:
• The transmissivity of a given length of an aquifer can be measured by dividing the flow from that portion of the aquifer by the width of the aquifer times the slope (gradient of the aquifer)

Even more math (double ugh)
• Mathematically this is:
• T = Q/W*I
• Where T is Transmissivity, W is the width of the aquifer, Q is flow and I is the hydraulic gradient.

Groundwater Flow Systems:
• Groundwater systems consist of a number of components. Groundwater aquifers exist in appropriate geologic settings but rarely have sharp boundaries.

Recharge my batteries:
• There are recharge areas that are generally where porous rock, sand or soils outcrop or areas where streams and ponds and wetlands are present.

Out of there:
• There are discharge areas where springs appear, where streams are fed by exfluent flow and also the ocean.
• The other main discharge area is the well or well field.

Go with the flow:
• Groundwater flows from recharge to discharge areas at a rate determined by Darcy’s law and in quantities determined by the transmissivity of the aquifer.

Importance:
• Estimating these flow parameters is essential to understanding the quantity of water that an aquifer can produce and the direction and speed of the flow of groundwater and contaminants.
Storage Coefficient:
• The storage coefficient is a measure of how much water can be gotten out of an aquifer.
• Specifically, it is the drop in head per unit surface area for a given quantity of water that has been pumped out.
• The more transmissive the aquifer, the less the head will fall for a given flow of water being pumped out.

Cone of Depression:
What sitting through more boring lectures on groundwater will drive you into…

Cone of Depression:
• A funnel shaped lowering of the water table produced by pumping a well faster than water can replenish the well.
• This is not undesirable, rather it is the increasing slope of the water table that draws water into the well to continue to feed the pump.

Steep & Deep:
• In a highly transmissive aquifer, the steepness cone of depression will be gentle. In an impermeable aquifer the cone of depression will be very steep.

Contours:
• Groundwater contours around a well will form concentric circles. In a uniform aquifer the circles would be perfect, but usually they are eccentric.

Super-position.
• Two (or more wells) in close proximity will
• Have cones of depression that overlap.
• The result is an additive potentiation (increase) in the total draw-down over the area.
• Thus many wells in a limited area cause over-draft.




Lec 27 Groundwater Resources Management I.

Management of well fields:
• Multiple wells are put in, because production from a single well can be limited and because distribution facilities are costly and recharge sources, aquifers, etc may have multiple locations that can have great local differences.
• The challenge is to operate the wells so as to produce the most water with the least cost.
• Large draw-down = higher costs. Why?

Whose on top?
• Determine super-position of cones of depression to determine interference of multiple wells with each other.
• Sometimes this comes up in law suits from adjacent property owners.

Well monitoring:
• Wells should be checked periodically to determine:
• Depth to groundwater,
• Water quality,
• Production rate,
• Time/draw-down.
• Down-hole video is now common.

Groundwater Laws Requiring Monitoring:
• Safe Drinking Water Act SDWA requires yearly tests for most municipal wells.
• Wells specifically for monitoring the quality or quantity of groundwater are called monitoring wells.
• Resource Conservation and Recovery Act (RCRA) requires monitoring wells at all haz-waste and solid waste disposal facilities

How groundwater is monitored:
• At least 4, sometimes several hundred wells are installed.
• Monitoring is usually quarterly.
• Monitoring for depth to water is done with tape, electric line, popper or TLC meter.
• Samples are obtained with a bailer or pump.

Well-head protection:
• This refers to a program of controlling landuse and remediation and survey of contamination to safeguard wells. Frequently it is combined with an aquifer vulnerability analysis.
• GIS is a useful technology
• Controlling landuse is difficult since serving as a recharge area does not generate profits for the local landowner.

How is groundwater protected:
• Most groundwater protection is indirect (clean water act (CWA), & RCRA) but Underground Injection Control Program (UIC) program provides direct protection.
• Shallow injection wells illegal.
• Dumping liquid hazardous wastes in landfills is illegal.
• LUST is controlled.


Case Studies: Edwards Aquifer
• CHARACTERISTICS:
• Karst topology, recharge in Edwards Plateau
• Main source of Guadalupe River (endangered species) & San Marcos springs. Crucial for San Antonio
• Vulnerable to overdraft.
• Home of Satan’s catfish and other weird, wonderful and white creatures.

Edwards Aquifer Management:
• Edwards Aquifer Conservation District.
• Saline Water line monitoring network.
• Control of pollution in recharge area (DRASTIC) analysis.
• An underground River?
• Edwards Aquifer Research Institute.
• The most hated Farmer in Texas??
• Sierra Club to the rescue??

Ogallala aquifer: Characteristics
• High plains of Texas, Nebraska, Eastern Colorado, Oklahoma and Kansas.
• Sole supply for many areas that are highly productive for agriculture.
• Ancient deposition.
• Variable thickness
• Slow rate of replenishment.
• Fossil water.
• Some contamination, pesticides and PANTEX

Ogallala Management:
• Protected in Nebraska Kansas and Colorado but not very well in Texas where it is most threatened
• Overdraft is concern, especially in Texas.
Robertson County a water colony?
• Long term, likely depopulation of area with loss of agriculture.
• Alternatives: conjunctive use, injection, trans-basin water projects, etc.


Santa Barbara County:
• Story of 6 aquifers:
• Santa Barbara
• Goleta
• Santa Maria
• Lompoc
• San Antonio Creek
• Cayuma Valley.

Santa Barbara:
• Small aquifer provides 30% of water for city of 100,000.
• Supplemented by rain fed reservoirs in the mountains.
• Contaminated by TCE
• Overdrafted, but protected by fault from salt water intrusion.
• During drought strange things happened:
• Well permits (bring your lawyer)

Goleta.
• 40% of water for 100,000 people.
• Separated from Santa Barbara by a low range of hills.
• Not protected from Salt Water Intrusion.
• Building moratorium 1972-1992.
• Worst municipal water in California.
• The $2 million well.
• No well permits, most existing wells for agriculture so “farmers” live in million $ mansions.

Santa Maria
• Sandy alluvial plateau, easy recharge easy contamination.
• Twitchell Dam and conjunctive use of surface water
• Contamination from oil and gas and hazardous waste dump.
• Agricultural conversion, growth center of county.

Lompoc:
• Flower seed capital of U.S.
• Salinization of groundwater
• Abundance of municipal water from agricultural conversion
• Groundwater unfit for sewage treatment plant.

San Antonio Creek Aquifer:
• Contaminated by VAFB.
• Endangered species in Barka Slough.
• Indian village sites
• Air Force vs. State and County Gov.

Cayuma Valley.
• The wells are the biggest things around.
• Thick water table aquifer.
• 400 feet of draw-down.
• No subsidence.
• Groundwater “mining”: 50,000 years of accumulation gone in 50 years.
• Bunny Love carrots gone, now emus and ostriches…no development since 1952.
• County Water agency controls permits.




Lec. 28: Groundwater Resources Management & Mismanagement.

Overdraft Examples:
• Examples:
• San Jose area, CA.
• FT. Stockton, TX.


More impacts of over-draft:
• 2) Water that formally flowed in streams and surface water features may be drawn into the aquifer and the well.
• Thus over-drafting a well can dry up not only the aquifer but streams flowing over the area underlain by the aquifer.

Salt water intrusion



Subsidence
• Subsidence is due to dewatering aquifers that contain collapsible clays.
• When the water pressure in the aquifer is reduced the pressure holding the clay layers apart is also reduced and the clays are compressed by the weight of overlying sediments.
• Subsidence of as much as 60 feet is possible.



Examples of subsidence:
• Eastern San Joaquin Valley, CA.
• Arizona.
• Brownwood and other areas along ship channel in Houston area, Jersey Village & north-west Harris County
• Venice, Italy
• Mexico City.

Las Vegas Groundwater management
• Use of both surface and groundwater
• Conservation program
• Groundwater injection program


Well fields:
• To exploit groundwater, frequently more than one well will be placed into an aquifer.

Contamination at Nellis AFB Nevada
• 900,000 gallons of jet fuel floating on water table, off-site migration of contamination, on-base wells contaminated.
• Order from State “monitor, replace contaminated wells, let natural attenuation work…”
• What is the difference between these two sites…

Henderson Landfill, Nevada
• Landfill opened in 1957, closed in 1976.
• Received mix of wastes including wastes from Basic Industries chemical complex.
• Located in stream-channel, homes built on top of waste piles.
• Seepage of toxins into stream, monitoring wells contaminated with PAH, cyanide, arsenic, DDT, BTEX, radio-nuclides etc

Contact-

Visvesvaraya Technological University, Karnataka
Jnana Sangama, VTU Main Road, Machhe
Belagavi, Karnataka 590018