Risk assessment of abandoned radioactive logging sources in oil wells in nigeria
Sources of water (RAIN) Surface SourcesGround Sources StreamsSprings LakesInfiltration Galleries...
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Transcript of Sources of water (RAIN) Surface SourcesGround Sources StreamsSprings LakesInfiltration Galleries...
Sources of water (RAIN)
Surface Sources Ground Sources
Streams Springs
Lakes Infiltration Galleries
Ponds Infiltration Wells
Rivers Wells and Tube wells
Impounded Reservoirs
Oceans
Springs
•Natural outflow of GW @ earth’s surface.
•Gravity springs : GW table rises high & water overflows
though the sides of a natural valley or depression.
•Surface springs : an impervious obstruction supporting
underground storages becomes inclined causing water table
to go up & get exposed to ground surface.
•Artesian Springs : when water flowing through some
confined aquifer is under pressure.
Artesian spring
Aquifers & Aquicludes
Non artesian or Unconfined aquifers & well
Wells
•A water well is a hole usually vertical, excavated in the
earth to bring GW to the surface.
•Open Wells / Tube Wells.
Open Wells (Dug Wells)
•Open masonry wells, 2 – 9 m dia, less than 20 m depth.
Discharge 5 L/s
•Walls built of brick or stone masonry or precast concrete ring
•To improve yield of well, 10 cm dia hole @ centre of well is
made (Shallow well/Deep Wells)
•Shallow well rests in a pervious strata.
•Deep well rests on an impervious ‘mota’ layer & draws its
supply from the pervious formation lying below ‘mota’ layer.
•A shallow well might be having more depth than a deep well
Deep wells
Infiltration Galleries (Horizontal Wells)
•Horizontal tunnels (with holes on sides) constructed of
masonry walls with roof slabs to tap GW flowing towards
rivers/lake.
•Constructed @ shallow depths (3-5m) along the banks of
river either axially along or across GW flow.•Width (1m), depth (2m) , length (10 – 100m)
•If large GW quantity exists, porous drain pipes are provided
and they are surrounded by gravel and broken stone. •Yield, 15,000 L/day / Meter length•A collecting well @ shore end of gallery serves as sump
from where water is pumped.
Section of infiltration gallery
Infiltration galleries
•They are shallow wells constructed under beds of rivers.
•Deposits of sand exist at least 3m deep in river beds. As the
water percolates down, impurities are removed. Quality of
water is better than river water.
•They are sunk in series in the bank of the river.
•They are closed @ top & open & bottom. Manholes are
provided @ top for inspection.
•They are constructed of brick basonry with open joints.•Various infiltration wells are connected by porous pipes to
sump called jack well.
Infiltration Wells
•Structures used to withdraw water from various sources.
•Lake / Reservoir / River /Canal/ Intake.
Intakes
•Submersible intake.
•A pipe laid in the bed of the lake.
•One end is in the middle of the lake & is fitted with bell –
mouth opening covered with a mesh & protected by concrete
crib.
•Water enters in the pipe through bell-mouth opening & flows
under gravity to the bank where it is collected in a sump –
well & then pumped to TP.
Lake Intakes
•A circular masonry tower (4-7m dia) constructed along bank
of the river.
•Water enters in the lower portion of the intake (i/e sump –
well) from penstocks.
•Penstocks are fitted with screens to prevent entry of floating
solids.
• No. of penstock openings are provided in intake to admit
water @ different levels.
•Opening & closing of penstock valves is done with wheels
provided @ pump – house floor.
River Intakes
• Constructed inside river @ suitable place.
•A concrete circular shell filled with water upto water level
inside the river.
•Water enters through openings provided on outer circular
shell, as well as on inside shell.
•Water is taken to the bank of the river through the
withdrawal conduit in the sump well from where it is pumped
to WTP.
a) Wet Intakes
b)Dry Intake tower
•In wet intake tower, water enters first in the outer shell then
it enters in the inner shell.
•In dry intake, water enters directly withdrawal conduit.
•An intake tower constructed on the slope of the dam.
•Intake pipes are fixed @ different level to withdraw water at
all variations of water level.
•All inlet pipes are connected to one vertical pipe inside the
intake well.
•Screens are provided @ mouth of all intake pipes to prevent
entry of floating matter.
•Water entering the vertical pipes is taken to other side of the
dam by means of an outlet pipe.
Reservoir Intake
•At the top of intake tower, sluice valves are provided to
control flow of water.
•Valve tower is connected to the top of the dam by means of
foot-bridge gang- way.
•For earthen dams, intake towers are separately constructed.
•For RCC masonry dams, intake tower is constructed inside
the dam it self.
Reservoir Intake tower
Canal Intake
•No need to provide multiple ports, as water level in canal
remains constant.
•A pipe placed in a brick masonry chamber constructed
partly in the canal bank.•On one side of chamber, opening is provided with coarse
screen for entrance of water.
•A bell mouth fitted with a hemispherical fine screen is
provided @ the mouth of the pipe.•Outlet pipe carries water to the other side of the canal bank
from where it is taken to TP.•One sluice valve operated by a wheel from top of masonry
chamber is provided to control flow of water in the pipe.
Canal intake well
Dry intake tower standing in the river or reservoir