PAES Irrigation - Terms

access areas

areas open for public entry such as golf courses, public and private parks, playgrounds, schoolyards and playing fields, residential landscapes and industrial park landscapes

actual crop evapotranspiration ETa

rate of evapotranspiration equal to or smaller than predicted ETcrop as affected by the level of available soil water, salinity, field size or other causes

active storage

volume of water stored in reservoir between the minimum water level and normal water level

afflux

elevation 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

algal bloom

overgrowths of algae in water producing dangerous toxins in fresh or marine water

angle of inclination

the tilt of the PV module with respect to the horizontal plane

application efficiency Ea

ratio of the average depth of irrigation water infiltrated and stored in the root zone to the average depth of irrigation water applied

aquifer

geologic formation which contains water and transmits it at a rate sufficient to be economically developed for pumping with a well

average pressure

average sprinkler pressure of a lateral

basin

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 irrigation

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

bearing capacity

maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil

border irrigation

method of irrigation which makes use of parallel border strips where the water flows down the slope at a nearly uniform depth

border strip

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

charge controller

monitors the charging and discharging of the battery connected to the PV array

check dam

small barrier built across the direction of water flow on shallow rivers and streams intended to convey runoff during peak flow and to slow and hold surface water long enough for the water to deposit sediment it is carrying; facilitates irrigation by using the upstream bay of the dam as pump sump

confined aquifer

aquifer where groundwater is confined or overlain by a relatively impermeable layer

contamination

introduction of substances not found in the natural composition of water that make the water less desirable or unfit for intended use

controller

link between motor pump and solar generator that regulates the operation of PV array to pump and is classified into two types: inverter (directly connected to pump set) and charge controller (with batteries)

conveyance efficiency Ec

ratio between water received at the inlet for a block of fields to that released at the project’s headwork

conveyance loss

loss of water from a channel during transport due to seepage and percolation

crop coefficient kc

ratio of the actual crop evapotranspiration to its potential evapotranspiration

crop evapotranspiration

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 evaporation from the soil surface and wet leaves

cropping pattern

sequence of different crops grown in regular order on any particular field or fields

crop water requirement CWR

amount of water used in producing crops which is the sum of evapotranspiration or consumptive use plus seepage and percolation losses

critical depth

depth of water flow where the energy content is at minimum hence, no other backwater forces are involved

dam

any barrier constructed to store water

dam height

vertical distance from lowest point of the ground line to the dam crest

dead storage

volume below the intake structure computed as V = 20900 × A^0.687 where A is the drainage area, (km2), sediment volume based on 25 years of accumulation in the reservoir

designed height

actual height of the embankment after settlement

design irrigable area

maximum area which an irrigation project can serve considering the extent of arable lands and the available water supply

design pressure

pressure required to overcome the elevation difference between the water source and the sprinkler nozzle, to counteract friction losses and to provide adequate pressure at the nozzle for good water distribution

diversion dam

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

distribution uniformity

numerical value on the uniformity of application for agricultural irrigation systems

drop

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

drip irrigation

trickle irrigation involves dripping water onto the soil at very low rates (2-20 L/h) from the emitters where water is applied close to plants so that only part of the soil in which the roots grow is wetted

diversion water requirement DWR

the total quantity of water diverted from a stream, lake, or reservoir, or removed from the ground in order to irrigate a crop

effective rainfall ER

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 rooting depth

soil depth from which the bulk of the roots of the crop extracts most of the water needed for evapotranspiration

effective size

particle diameter corresponding to a 10% sieve passing

effluent

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 standard

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

elevated flume

water conveying conduit or trough which is supported on abutments by piers

emitters

applicator used in drip, subsurface, or bubbler irrigation designed to dissipate 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

emitter spacing

spacing between emitters or emission points along a lateral line

equipment crossing

provision for passing of equipment and small machinery

evapotranspiration

combination of water transpired from vegetation and evaporated from the soil, water, and plant surfaces

farm ditch

channel which conveys irrigation water from the turnout to the paddy field

farm water requirement FWR

amount of water to replenish the crop water requirement and losses less the effective rainfall

filter drain

dam component which prevents migration of small particles and screen off fine materials that flow with seepage water and prevent piping

finished height

height of the embankment to be attained during construction

Flume

in-line structure with a geometrically specified constriction built in an open channel such that the center line coincides with the center line of the channel in which the flow is to be measured

freeboard

additional height of the dam provided as a safety factor to prevent overtopping by wave action or other causes

furrow irrigation

method of irrigation where water runs through small parallel channels as it moves down the slope of the field

furrows

small parallel channels, made to carry water in order to irrigate the crop

gabion

stones wrapped in wire fence meshes for added stability and strength

head ditch

supply ditch small channel along one part of a field that is used for distributing water in surface irrigation

homogeneous embankment

dam composed of a single kind of embankment material exclusive for slope protection

hydraulic jump

occurs when a thin sheet of incoming flow moving at high velocity strikes water of sufficient depth

hydrologic frequency analysis

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

inside slope

slope of the upstream face of the embankment

inverter

converts direct current (DC) from PV module to alternating current (AC)

irrigation period

time required to cover an area with one application of water

Karst topography

geological formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rocks such as limestone or dolomite

land preparation water requirement LPWR

amount of water required in lowland rice production which includes water losses through evaporation, seepage and percolation and land soaking

land soaking water requirement LSR

amount of water required in lowland rice production which is a function of the initial soil moisture and the physical properties of the soil

lateral spacing

spacing between irrigation laterals

leaching

deep percolation of water beyond the root zone of plants, resulting in loss of salts or nutrients

loading limit

allowable pollutant-loading limit per unit of time, which the wastewater generator is permitted to discharge into any receiving body of water or land

manifold

portion of the pipe network between the mainline and the laterals

manufacturer’s coefficient of variation Cv

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 200C

natural spillway

spillway which is not excavated such as natural draw, saddle or drainage way

normal storage elevation

maximum elevation the water surface which can be attained by the dam or reservoir without flow in the spillway

outside slope

slope at the downstream face of the embankment

pan coefficient

ratio between reference evapotranspiration (ETo) and water loss by evaporation from an open water surface of a pan

pan evaporation

rate of water loss by evaporation from an open water surface of a pan

percolation

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

permeability test

method to determine the rate of flow under laminar flow conditions through a unit cross sectional are of soil under unit hydraulic gradient

piping

internal erosion induced by regressive erosion of particles from downstream and along the upstream line towards an outside environment

pollutant

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

pond

sealed section formed between earth embankments where combined seepage and percolation will be measured

potential irrigable area

area capable of being irrigated, principally as regards to availability of water, suitable soils, and topography of land

pumping test

pumping of water from a fully developed well at a controlled rate and observing, with respect to time, the drawdown in two or more observation wells, in order to determine the aquifer hydrologic properties

PV performance ratio

ratio of the input solar power to the PV module and the output power of the inverter/controller

ray of incidence

the angle with which a ray of sunlight strikes the surface of the PV module, measured with respect to a line perpendicular to said surface

reference crop evapotranspiration ETo

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

reservoir

part of the system that impounds the runoff or temporary water storage that adds kinetic energy to facilitate water distribution (also known as a water tank)

residual moisture content

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

re-use

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

rockfill dam

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

seepage

water escaping below or out from water conveyance facilities such as open ditches, canals, natural channels, and waterway

seepage line

phreatic line line with no filter arrangements where seepage occurs

seismicity

occurrence or frequency of earthquakes in a region

setback distance

distance from the perimeter of the irrigation area to the community or area of concern that is sensitive to contamination

shallow tubewell

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 with the use of suction lift pumps

Solar Powered Irrigation System (SPIS)

irrigation system powered by solar energy, using PV technology, which converts solar energy into electrical energy to run a DC or AC motor-based water pump. It consists of solar PV modules, pump set, electronic controls to operate the pump, the required hardware, and in some cases other items like inverters and batteries

solar irradiance

amount of solar energy received by or projected onto a surface, expressed in Watts per square meter (W/m2)

spillway

channel which releases surplus or flood water which cannot be contained in the active storage space of the reservoir

sprinkler irrigation

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