PAES IRRIGATION STRUCTURE Flashcards
volume of water stored in reservoir between the minimum water level and
normal water level
Active Storage
vertical distance from lowest point of the ground line to the dam crest
Dam Height
volume below the intake structure computed
Dead volume
dam component which prevents migration of small particles and screen off fine
materials that flow with seepage water and prevent piping
Filter drain
maximum elevation the water surface which can be attained by the dam or
reservoir without flow in the spillway
Normal Storage Elevation
vertical distance measured from the top of the dam down to the bedrock
Structural height
The stable slope for the upstream face is
2.75:1
The stable slope for the downstream face is
2.5:1
actual height of the embankment after settlement
Design height
height of the embankment to be attained during construction
Finished height
ratio of the storage capacity to the total earth volume required for embankment
construction which indicates the relative cost of the different types of reservoir
Storage ratio
rainfall pattern with five wet months of more than 200 mm/month, five dry
months of less than 100 mm/month, two transition months of 100mm200mm/month and total annual rainfall above 1500 m
Unimodal rainfall pattern
Suited to an area with an
undulating topography. A
dam is built across a
valley and water is
impounded on the
upstream side of the dam
Straight embankment
On slightly sloping land,
the excavated earth can
be used to impound some
water above ground level.
On higher slopes, it can be
designed so that all water
is stored above service
level
Rectangular balance equation
Water is impounded
against the slope behind a
semicircular
embankment
Semicircular embankment
The only designed suited
to flat areas. A reservoir is
constructed by excavating
the earth leaving storage
space that can be filled
with water. Water is
stored below the ground
level and pumping is
required to draw out
water
DugOut Pond
dam that relies on rock, either dumped in lifts or compacted in layers, as a major
structural element where an impervious membrane is used as the water barrier
and can be placed either within the embankment or on the upstream slope
Rockfill Dam
rise in maximum flood level from the original unobstructed flood level which
result after an obstruction to the flow such as a dam, has been introduced
afflux elevation
structure or weir provided across the river or creek to raise its water level and
divert the water into the main canal to facilitate irrigation by gravity.
diversion dam
a weir wherein the upper curve of
the ogee is made to conform to the
shape of the lower nappe of a
ventilated sheet of water falling from
a sharp-crested weir
Ogee
occurs when a thin sheet of incoming flow moving at high velocity strikes water
of sufficient depth
hydraulic jump
a weir which produces freedischarging flows and dissipates
overflowing water jet with the
impact in the downstream apron
Vertical drop
has stable and predictable hydraulic
jump
- most adoptable for rivers that have
heavy sediment loads
Glacis
a weir where the larger part of the
ponding is accomplished by the solid
obstruction or the main body of the
weir
- additional head can be achieved by
installing gates on the crest of the
weir which can be collapsed or
raised during floods
Gated
used to stabilize the river bed for
intake type diversion structures or to
gain a limited amount of diversion
head
Corewall
Methods Used for Well Characterization and Site
InvestigationPreliminary basis in determining potential for
groundwater development; consists of collection,
analysis and hydrodeologic interpretation of
existing topographic maps, aerial photographs,
geologic maps and logs
Geologic Investigations
Used to determine groundwater conditions from
photographs of the earth taken from aircraft or
satellite at various electromagnetic wavelength;
specific methods include stereoscopic
examination of black-and-white aerial
photographs and infrared imagery
Remote sensing
Uses scientific measurement of physical
properties of the earth’s crust for investigation of
mineral deposits or geological structure; findings
are interpreted in terms of rock type and
porosity, water content and water quality
Geophysical Exploration
used in unconsolidated formations with large diameters
which permit considerable water storage.
Dug well
– used in formations with very shallow water
depths
Bored Well / Augered well
used in unconsolidated formations with shallow water
tables that contain not too many rocks
Driven well
constructed by the cutting action of a downward-directed
steam of water to excavate the hole and carry the excavated materials out of the
hole
Jetted well
distance from the perimeter of the irrigation area to the community or area of
concern that is sensitive to contamination
Setback distance
allowable pollutant-loading limit per unit of time, which the wastewater
generator is permitted to discharge into any receiving body of water or land.
Loading limit
introduction of substances not found in the natural composition of water that
make the water less desirable or unfit for intended use
Contaminants
the tilt of the PV module with respect to the horizontal plane
angle of inclination
