Irrigation Terminologies Flashcards
volume of water stored in reservoir between the minimum water level and normal water level
active storage
any barrier constructed to store water
dam
volume below the intake structure; sediment volume based on 25 years of accumulation in the reservoir
dead storage
dam component which prevents migration of small particles and screen off fine materials that flow with seepage water and prevent piping
filter drain
dam composed of a single kind of embankment material exclusive for slope protection
homogeneous embankment
spillway which is not excavated such as natural draw, saddle or drainage way
natural spillway
maximum elevation the water surface which can be attained by the dam or reservoir without flow in the spillway
normal storage elevation
part of the system that impounds the runoff
reservoir
line with no filter arrangements where seepage occurs
seepage line
phreatic line
channel which releases surplus or flood water which cannot be contained in the active storage space of the reservoir
spillway
total capacity at normal water surface elevation
storage capacity
vertical distance measured from the top of the dam down to the bedrock
structural height
side of the embankment wetted by the impounded water
upstream face
vertical distance from lowest point of the ground line to the dam crest
dam height
geological formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rocks such as limestone or dolomite
Karst topography
area which contributes runoff or drains water into the reservoir
watershed
privilege granted by the government to use and appropriate water
water right
reservoir where the upper reaches of the basin is shielded by high mountain barriers
well-protected reservoir
dam consisting a central impervious core flanked between zones of more pervious materials
zoned embankment
field that is level in all directions, encompassed by
basin
type of surface irrigation where water is applied to the basin through a gap in the perimeter dike or adjacent ditch; water is retained until it infiltrates into the soil or the excess is drained off
basin irrigation
method of irrigation which makes use of parallel border strips where the water flows down the slope at a nearly uniform depth
border irrigation
area of land bounded by two border ridges or dikes that guide the irrigation stream from the inlet point of application to the ends of the strip
border strip
small channel along one part of a field that is used for distributing water in surface irrigation
head ditch
supply ditch
application of water by gravity flow to the surface of the field. Either the entire field is flooded (basin irrigation) or the water is fed into small channels (furrows) or strips of land (borders)
surface irrigation system
actual height of the embankment after settlement
designed height
height of the embankment to be attained during construction
finished height
additional height of the dam provided as a safety factor to prevent overtopping by wave action or other causes
freeboard
slope of the upstream face of the embankment
inside slope
slope at the downstream face of the embankment
outside slope
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 100mm-200mm/month and total annual rainfall above 1500 mm.
unimodal rainfall pattern
numerical value on the uniformity of application for agricultural irrigation systems
distribution uniformity
time required to cover an area with one application of water
irrigation period
method of applying irrigation water similar to natural rainfall where water is distributed through a system of pipes by pumping and then sprayed into the air through sprinklers so that it breaks up into small water drops which fall to the ground
sprinkler irrigation
distance between two sprinkler heads along the lateral
sprinkler spacing
diameter of the circular area wetted by the sprinkler when operating at a given pressure and no wind
wetted diameter
applicator used in drip, subsurface, or bubbler irrigation designed to disspate pressure and to discharge a small uniform flow or trickle of water at a constant rate that does not vary significantly because of minor differences in pressure
emitters
spacing between emitters or emission points along a lateral line
emitter spacing
spacing between irrigation laterals
lateral spacing
deep percolation of water beyond the root zone of plants, resulting in loss of salts or nutrients
leaching
portion of the pipe network between the mainline and the laterals
manifold
measure of the variability of discharge of a random sample of a given make, model and size of emitter, as provided by the manufacturer and before any field operations or aging has taken place determined through a discharge test of a sample of 50 emitters under a set pressure at 200 0C
manufacturer’s coefficient of variation
drip emitter spacing which is 80% of the wetted diameter estimated from field tests
optimal emitter spacing
width of the strip that would be wetted by a row of emitters spaced at their optimal spacing along a single lateral line
wetted widths
areas open for public entry such as golf courses, public and private parks, playgrounds, schoolyards and playing fields, residential landscapes and industrial park landscapes
access areas
volume of water stored in reservoir between the minimum water level and normal water level
active storage
rate of evapotranspiration equal to or smaller than predicted crop evapotranpiration as affected by the level of available soil water, salinity, field size or other causes
actual crop evapotranspiration
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
overgrowths of algae in water producing dangerous toxins in fresh or marine water
algal bloom
ratio of the average depth of irrigation water infiltrated and stored in the root zone to the average depth of irrigation water applied
application efficiency
geologic formation which contains water and transmits it at a rate sufficient to be economically developed for pumping artificially developed well
aquifer
cross-sectional area of the flow which is measured perpendicular to the direction of flow
area
field that is level in all directions, encompassed by a dike to prevent runoff, and provides an undirected flow of water onto the field
basin
type of surface irrigation where water is applied to the basin through a gap in the perimeter dike or adjacent ditch; water is retained until it infiltrates into the soil or the excess is drained off
basin irrigation
maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil
bearing capacity
method of irrigation which makes use of parallel border strips where the water flows down the slope at a nearly uniform depth
border irrigation
area of land bounded by two border ridges or dikes that guide the irrigation stream from the inlet point of application to the ends of the strip
border strip
inclination or elevation drop per unit length of the channel bottom
channel bed slope
groundwater that is confined by relatively impermeable layer
confined aquifer
introduction of substances not found in the natural composition of water that make the water less desirable or unfit for intended use
contamination
ratio between water received at the inlet for a block of fields to that released at the project’s headwork
conveyance efficiency
loss of water from a channel during transport due to seepage and percolation
conveyance loss
record of formation stratification of an aquifer showing the depth, thickness, degree of
consolidation and other aquifer physical characteristics
well log
accounting of water inflows, such as irrigation and rainfall, and outflows, such as evaporation, seepage and percolation
water balance
waste in liquid state containing pollutants
wastewater
any material either solid, liquid, semi-solid, contained gas or other forms resulting from industrial, commercial, mining, or agricultural operations, or from community and household activities that is devoid of usage and discarded
waste
canals that are cut through the soil, in which the soil excavated from the bed are used to form the embankment
unlined channels
unlined canal
occurs when flow has a constant water area, depth, discharge, and average velocity through a reach of channel
uniform flow
ratio of the particle size at 60% pasing to that at 10% passing
uniformity coefficient
aquifer which has water table serving as upper surface of the zone of saturation
unconfined aquifer
width of the channel cross-section at the free surface
top width
slope of the water surface profile plus the velocity head in open channels
slope of the energy grade line
slope of the free water surface
slope of the hydraulic grade line
ratio of the horizontal to vertical dimension of the channel wall
side slope
distance from the perimeter of the irrigation area to the community or area of concern that is sensitive to contamination
setback distance
occurrence or frequency of earthquakes in a region
seismicity
tube or shaft vertically set into the ground at a depth that is usually less than 15 m for the purpose of bringing groundwater into the soil surface whose pumps are set above the water level
shallow tubewell
conveys canal water under roads or railroads
road crossing
taking wastewater from one industry or process, treating it and then using it in another process or industry such as for irrigation, as liquid fertilizer and for aquaculture
re-use
moisture left in the soil before the initial irrigation water delivery which describes the extent of water depletion from the soil when the water supply has been cut-off
restricted areas
areas with limited entry such as freeway landscape, highway medians and other similar areas
residual moisture content
rate of evapotranspiration from a reference surface which is a hypothetical reference crop with an assumed crop height of 0.2 m, a fixed surface resistance of 70 s/m and an albedo of 0.23
reference crop evapotranspiration
area capable of being irrigated, principally as regards to availability of water, suitable soils, and topography of land
potential irrigable area
sealed section formed between earth embankments where combined seepage and percolation will be measured
pond
any substance, whether solid, liquid, gaseous or radioactive, which directly or indirectly alters the quality of any segment of the receiving water body or land resource so as to affect or tend to affect adversely any beneficial use thereof, or is hazardous or potentially hazardous to health, or imparts objectionable odor, temperature change or physical, chemical or biological change to any segment of the water body or land, or is in excess of the allowable limits or concentrations or quality standards specified in contravention of the condition, limitation or restriction prescribed in these guidelines
pollutant
method to determine the rate of flow under laminar flow conditions through a unit cross sectional are of soil under unit hydraulic gradient
permeability test
vertical flow of water to below the root zone which is affected by soil structure, texture, bulk density, mineralogy, organic matter content, salt type and concentration
percolation
rate of water loss by evaporation from an open water surface of a pan
pan evaporation
ratio between reference evapotranspiration and water loss by evaporation from an open water surface of a pan
pan coefficient
water flow that is conveyed in such a manner that top surface is exposed to the atmosphere such as flow in canals, ditches, drainage channels, culverts, and pipes under partially full flow conditions
open channel flow
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
canals with impermeable material (usually concrete) for channel stabilization and/or reduced seepage
lined channel
lined canal
amount of water required in lowland rice production which is a function of the initial soil moisture and the physical properties of the soil
land soaking water requirement
amount of water required in lowland rice production which includes water losses through evaporation, seepage and percolation and land soaking
land preparation water requirement
closed conduit designed to convey canal water in full and under pressure running condition, to convey canal water by gravity under roadways, railways, drainage channels and local depressions
inverted siphon
inside bottom or sill of t the conduit
invert
estimation of the chance or likelihood of occurrence of a given event by determining the frequency curves of best fit to samples of hydrologic data
hydrologic frequency analysis
cross-sectional area of flow divided by the wetted perimeter
hydraulic radius
occurs when a thin sheet of incoming flow moving at high velocity strikes water of sufficient depth
hydraulic jump
profile of the free water surface
hydraulic grade line
amount of water to replenish the crop water requirement and losses less the effective rainfall
farm water requirement
channel which conveys irrigation water from the turnout to the paddy field
farm ditch
combination of water transpired from vegetation and evaporated from the soil, water, and plant surfaces
evapotranspiration
provision for passing of equipment and small machinery
equipment crossing
grade line of the water surface profile plus the velocity head in open channels
energy grade line
specific energy line
water conveying conduit or trough which is supported on abutments by piers
elevated flume
any legal restriction or limitation on quantities, rates, and/or concentrations or any combination thereof, of physical, chemical or biological parameters of effluent which a person or point source is allowed to delivery into a body of water or land
effluent standard
discharges from known sources which is passed into a body of water or land, or wastewater flowing out of a manufacturing plant, industrial plant including domestic, commercial and recreational facilities
effluent
particle diameter corresponding to a 10% sieve passing
effective size
particle diameter
soil depth from which the bulk of the roots of the crop extracts most of the water needed for evapotranspiration
effective rooting depth
amount of rainwater that falls directly on the field and is used by the crop for growth and development excluding deep percolation, surface runoff and interception
effective rainfall
in-line canal structure designed to convey canal water from a higher level to a lower level, duly dissipating the excess energy resulting from the drop in elevation
drop
the total quantity of water diverted from a stream, lake, or reservoir, or removed from the ground in order to irrigate a crop
diversion water requirement
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
maximum area which an irrigation project can serve considering the extent of arable lands and the available water supply
design irrigable area
amount of water used in producing crops which is the sum of evapotranspiration or consumptive use plus seepage and percolation losses
crop water requirements
sequence of different crops grown in regular order on any particular field or fields
cropping pattern
rate of evapotranspiration of a disease-free crop growing in a large field (one or more ha) under optimal soil conditions, including sufficient water and fertilizer and achieving full production potential of that crop under the given growing environment; includes water loss through transpiration by the vegetation, and vaporation from the soil surface and wet leaves
crop evapotranspiration
ratio of the actual crop evpotranspiration to its potential evapotranspiration
crop coefficient
depth of water flow where the energy content is at minimum hence, no other backwater forces are involved
critical depth
loss of water from a channel during transport due to seepage and percolation
conveyance loss
ratio between water received at the inlet for a block of fields to that released at the project’s headwork
conveyance efficiency
