Soil and Water Conservation Flashcards
needed in estimating runoff, planning erosion control measures, planning for irrigation and drainage, and water conservation in low rainfall regions
Precipitation
needed in designing structures and channels that will handle natural flows of water
Runoff
required in planning irrigation and drainage systems, moisture conservation practices, etc.
Infiltration, Evaporation and transpiration
caused by the rising of warmer, lighter air in colder, denser surroundings.
Convective Precipitation
results from mechanical lifting of the air mass over mountain barriers.
Orographic Precipitation
air is lifted through horizontal convergence of the inflow into a low pressure area
Non-frontal
associated with the movement of air masses from high-pressure to low-pressure regions.
Cyclonic Precipitation
lifting of warm air over cold air at the contact zone between air masses having different characteristics
Frontal
this involves the averaging arithmetically all the rainfall depths measured by the rain gages within the area.
Arithmetic mean
– location of the rain gauges are plotted on the map of the area and stations are connected by straight lines. Perpendicular bisectors are constructed on each of the connecting lines thereby forming polygons enclosing each rain gage. The average rainfall over the area is then estimated as the area weighted average for all polygons
Thiessen polygon
station locations and amounts of rainfall are plotted on a suitable map, and contours of equal precipitation (isohyets) are then drawn. The equation used is similar to that of Thiessen method except that the area, Ai, is the area under one isohyet, Pi.
Isohyetal
computer aided method wherein it averages estimated precipitation at all points of a superimposed grid.
Grid-Point Method
for rolling areas and non-uniform distribution of gages, distance factor fixed by location of gages is used for analysis using this method. It operates under the principle that the value of points close together in space are more likely to be similar than with points farther apart.
Inverse Distance Ratio Method
the number of years during which one storm of a given duration and intensity is expected to occur.
frequency or recurrence interval
one in which a definite law of certainty exists
Deterministic Process
governed by chance; time series INDEPENDENT
Probabilistic Process
governed by chance; time series DEPENDENT
Stochastic Process
data is more or less normally distributed
Normal Distribution
used when there is skewness in the data distribution
Log-Normal Distribution
considers further the skewness of the logarithmically transformed hydrologic data; preferred for flood flow frequency; log-normal distribution is a special case of this method
Pearson Type III Distribution
so far gives the best fit for most stations for 1-week, 2-week, 3-week and monthly rainfall totals of the country
Gamma Density Function
that which travels over the ground surface and through the channels to reach the basin outlet
Surface Runoff
that which infiltrates into the soil surface and moves laterally through the upper soil horizons towards streams as perched groundwater above major groundwater level
Interflow
groundwater discharge into a stream due to deep percolation of the infiltrated water into groundwater aquifers
Groundwater Runoff
that part of surface runoff that flows over the surface towards the stream channel
Overland flow
surface runoff plus interflow
Direct runoff
same as interflow
Subsurface runoff
same as groundwater runoff
Baseflow
used to determine the magnitude of floods and a valuable consideration in the design of structures
Peak Flow (qp)
used for flood forecasting and water quality studies; watershed response time
Time to Peak (tp)
total water yield from a storm for a given watershed
Runoff Volume (V)
time for surface and interflow to recede; duration of flooding
Recession Time (tr)
total of time to peak and recession time; (tb) = (tp) + (tr)
Base time (tb)
low flow, dependable flow, groundwater discharge
Base flow
a graphical representation of the instantaneous runoff rate against time. The area under it gives the runoff volume.
hydrograph
– assumes that all hydrographs from all small watersheds (in the US) have similar forms
– it is plotted over 100 arbitrary units of flow and 100 arbitrary units of time
Basic Hydrograph
- approximation of the basic hydrograph
- - developed mainly to simplify flood routing procedures in US
Triangular Hydrograph
- a hydrograph with a unit volume (e.g. 1cm) of direct runoff for a given storm duration
- represent the response of the basin on a given storm duration and characteristics
- - enables one to synthesize hydrographs for complex storms by superimposing the hydrographs resulting from the individual components of the storm
- represent the response of the basin on a given storm duration and characteristics
Unit Hydrograph
- prepared using data from a number of watershed to develop dimensionless unit hydrographs which are applicable to ungaged watersheds
- a dimensionless hydrograph is made from natural or unit hydrographs in which the time to peak (tp) and the peak runoff rate (qp) are considered an t/tp is plotted against q/qp
Synthetic Hydrograph
provide record of the highest stage observed at a stream
Crest Stage Gage
record the pressure required to maintain a small flow of gas from an orifice submerged in the stream
Bubbler Gage
motion of a float is recorded on a graph
Float-type Water-Stage Recorder
measures the velocity of a floating object preferably in a straight section of a stream
Float method
utilizes the equation or relation:
V = a + bN
Where: V – water velocity
a – starting velocity or velocity required to overcome mechanical friction
b – constant of proportionality
N – revolution per seconds of the meter cups / propeller
Propeller-type Meter (Current Meters)
Type of water erosion, primarily caused by raindrop
Splash / Raindrop Erosion
Type of water erosion, a thin film of soil layer detached and transported by water flowing on the land surface.
Sheet erosion
Type of water erosion, combination and splash and sheet erosion
Interrill erosion
Type of water erosion, advanced stage of rill erosion. Rills when neglected develop in size and become gullies.
Gully erosion
Type of water erosion, erosion of stream banks by flowing water
Stream bank erosion
Type of water erosion, erosion caused by wave action on the seashore
Coastal erosion
Type of water erosion, finger-like rills appear on the soil surface
Rill erosion
caused by high velocity winds moving over barren land surfaces.
Wind erosion
land slides and slips due to saturation of steep hills and slopes.
Slip erosion
replanting of forest trees species in the watershed area
Reforestation
a practical adaptation of reforestation whereby the species planted have economic value, such as mango, pili and so on.
Agroforestry
is the practice of growing different crops in alternate strips across the slope to serve as barriers for soil erosion.
Strip cropping
the process of covering the land surface with plant residues, plastic or other materials appropriate to arrest loss of moisture through evaporation
Mulching
consists of carrying out agricultural operations very nearly on the contour. It reduces the velocity of overland flow and retards soil erosion
Contour cultivation
modification of cropping system such as crop rotation and mixed cropping
Cropping systems
construction of earth embankment or ridge and channel across the slope at an acceptable grade to control the flow of runoff as well as soil particles.
Terracing
establishment of natural waterways or construction of canals and planting it with grasses to make it stable and arrest soil erosion
Grassed Waterways
constructed along the channel or waterway to control the velocity of flowing water and encourage deposition of sediments carried by water
Check dams or weirs
temporary detainment of water in farm pond and dams to mitigate the erosive capacity of water
Farm Ponds / Water Impounding Dams
a channel constructed around the slope and given a slight gradient to cause water to flow to a suitable and stable outlet.
Diversion Canal
concrete structure made of stones constructed along steep embankments to prevent landslide or gully erosion
Riprap
made of stones carefully and properly piled-up and arranged on steep embankments to protect from gully erosion or landslide
Stone wall
usually starts as small rills and gradually develops into deeper crevices
Gully erosion
is constructed across the slope above the gully. The grassed waterway intercepts the runoff coming from above the gully
Grassed waterways
can stabilize the slopes of the gully and hence reduce runoff velocities.
Vegetation
construction of series of platforms along the contours cut into the hill slope in a step like formation
- used for 25-30% slopes
- used for maximum moisture conservation
- used where land is at a premium
- conventional
- difficult to farm
Bench
- primary purpose is to remove excess water in such a way as to minimize erosion
- reduce slope length, conducts intercepted runoff water to outlet at non-erosive velocity
- outlet either surface or subsurface type
Broad-based Graded or channel type
- used for 9-24% slope
- easier to farm than conventional
- used for maximum soil and water conservation
Zingg or Conservation bench terrace
- no grade in channel
- primary purpose is moisture conservation, erosion control is secondary
- channel is normally closed at both ends to assure maximum detention
- adopted to deep, permeable soils
- more formable than bench types
- used where outlets are a problem
Broad-based, Level or ridge type
are open channels protected with suitable grasses constructed along the slope and act as outlet for terraces and graded bunds. They are also used to safely convey runoff from contour furrows, diversion channels and serve as emergency spillways in farm ponds.
The velocity of flow is dependent upon the ability of the vegetation to resist erosion. For design purposes, an average of 1.5 m/s to 2 m/s is used.
Grassed Waterways
Structures constructed along a channel to dissipate safely the energy of water by letting the water fall freely for a certain height.
Drop structures
A term adapted to measures utilizing both or in combination with the biological and engineering measures.
Vengineering
discharge is constant with respect to time
Steady Flow
if the depth changes abruptly over a comparatively short distance such as in a hydraulic jump
Rapidly Varied Flow
depth of flow is the same at every section of the prismatic channel
Uniform Flow
discharge is not constant with respect to time
Unsteady Flow
depth changes along the length of channel
Varied Flow
- if the depth changes smoothly over a distance
Gradually Varied Flow
Fr = 1
Critical Flow
fluid moves in parallel layers with no cross-currents; Re <= 2000
Laminar Flow
Fr < 1
Subcritical Flow
Fr > 1
Supercritical Flow
characterized by pulsatory cross-current velocities; Re => 4000
Turbulent Flow
special case of flow in which the discharge varies with distance along the channel
Spatially Variable Flow
is the elevation above some arbitrary zero datum of the water surface at a station along a river or stream.
River Stage
a scale set at the river/stream so that a portion of it is immersed in the water at all times to measure river stage.
Staff Gage
vulnerability or susceptibility of the soil to erosion. It is a function of both the physical properties of the soil and land management practices.
Erodibility
is the detachment and transport of soil particles from the land by water or wind action.
Soil Erosion
is soil detachment and transport resulting from the impact of water drops directly on soil particles or on thin water surfaces.
Splash / Raindrop Erosion
detachment and transport of soil by concentrated flow of water creating shallow rills or furrows.
Rill Erosion
potential ability of the rain to cause erosion. It is a function of the physical characteristics of the rainfall.
Erosivity
consists of soil removal from stream banks or soil movement in the channel.
Stream Channel Erosion
detachment and transport of soil particles by concentrated flow of water creating channels larger and deeper than rills. As differentiated with rill, channels or gullies created cannot be obliterated by normal tillage operation. Thus gully erosion is an advanced stage of rill erosion.
Gully Erosion
the depth of water in inches to be removed in a 24 hours period from the drainage area.
Drainage coefficient
structured device designed to hold a pool of water to cushion the impact and retard the flow of falling water as from an overflow weir, chute or drop.
Stilling Basin
planting different crops simultaneously in the same field at the same cropping season.
Multiple Cropping or Mixed Cropping
consist of growing alternate strip of clean cultivated and close-growing crops in the same field oriented across the slope.
Strip Cropping
(crop rotation) planting different crops, one after the other each season.
Relay Cropping
are specially shaped and stabilized channel sections which may also be used to measure flow and are generally less inclined than weirs to prevent floating debris and sediments from detention
Flume
the ratio of depth of run-off to depth of precipitation producing the run-off over a drainage area.
Run-off Coefficient
a natural body composed of mineral and organic material on the surface of the earth on which plants grow.
Soil
closed conduit usually circular, square or rectangular in cross section, used for conveying water across and under an elevated roadway, embankments, or dike.
Culvert
the relative proportion of the various size groups of individual soil grain.
Soil Texture
a structure which conveys water from a higher to a lower level, maybe inclined or vertical.
Drop Structures
an imaginary line of constant elevation on the surface of the ground.
Contour Line
the application of engineering principles to the solution of soil management problems, any method used to fully utilize and conserve soil.
Soil Conservation
constructed by cutting a shallow channel on the uphill-side and using only this soil to build the embankment.
Graded Terrace
study which deals with the relationship of the
physical environment and agricultural elements
Agrometeorology
the study of animal and plant life cycle as
affected by seasonal variations of climate
Phenology
are usually found in universities
and research institutes/stations, to collect
meteorological and biological data
Agromet stations
The pressure under a gravity dam producing an overturning effect
Foundation Pressure
The most elaborate method of computing potential Evapotranspiration
Penman
2 Methods of supplying water in the basin
Direct and cascade supply
Banawe rice terraces is a.
Bench terrace
The soil contain more or less equal amounts of sand, silt and clay?
loam soil
A vertical section to the soil mass where significant changes in the soil texture and structure with depth are observed
Soil profile
The moisture content of the soil when tension is 1/3 atmosphere
Field capacity
This refer to the additional height or depth of hydraulic structures
Free board
The rational method of determining runoff is applicable to.
Watershed with good vegetation
The other term for gravity well.
deep well
Term for solar radiation received at the earth’s surface
insolation
On the weather map, lines representing points of equal pressure is called.
isobars
It is the measure in difference in the ground level between two places in the field and referred to as percentage. It is the number of meter difference in elevation for each 100 m horizontal distance
Land slope
The name for seasonal winds (derived from Arabic mausim, a season).
monsoon winds
The type of climate prevailing in region 1 and 2.
type 1
The recommended variation in the lateral between the first and last sprinkle.
20%
A soil ph above 7.7.
alkali soil
Pipelines built on or near the ground surface to convey water across wide depressions.
Inverted siphon
Subsurface system wherein laterals join the submain on the both sides alternately.
herringbone
It is the water retained about individual soil particles by molecular action and can removed only by heating.
Hygroscopic water
The artificial application of water to the soil for the purpose of crop production.
Irrigation
Small earth embankment or dam built around each basin to hold water without leakage while it is infiltrate.
Bunds
A piece of land divided into strips by small earth bunds usually sloping uniformly away from the farm channel in the direction of water flow to irrigate similar crops and soil.
Borders
A small drain constructed at the end of each boarder to remove excess surface water .
Tail drain
A hydraulic shock occur when water flowing to pipe undergoes sudden changes in velocity.
Water hammer
The formation of cavities filled with the liquid vapor due to a local pressure drop and their collapse as soon as the vapor bubbles reach regions of high pressure .
Cavitation
A notch of regular form through which the irrigation stream is made to flow and built as either portable or stationary structure.
weir
The most stable and chief component of most soil on volumetric basis
mineral particles
Water held tightly to the surface of the soil particles by adsorption forces is called:
hygroscopic water
Two pronounced seasons: dry from November to April: wet during the rest of the year. All provinces on the Western part of the rest of the year. All provinces on the Western part of the Islands of Luzon, Mindoro, Negros and Palawan are covered
Type I Climate
No pronounced season, relatively dry from November to April and wet during the rest of the year. This type of climate covers the Western portion of the Mountain Province, Southern Quezon the Bontoc Peninsula, Masbate, Romblon, Northeast Panay, Eastern Negros, Central and Southern Cebu, part of Northern Mindanao and most of Eastern Palawan.
Type III Climate
Rainfall more or less evenly distributed throughout the year. The areas covered by Type IV climate are Batanes Province, North-eastern Luzon, Western Camarines Norte and Camarines Sur, Albay, Eastern Mindoro, Marinduque, Western Leyte, Northern Negros and most of Central, Eastern and Southern Mindanao.
Type IV Climate
No dry season with a very pronounced maximum rainfall from November to January. The areas covered are Catanduanes, Sorsogon, the Eastern part of Albay, the Eastern and Northern Parts of Camarines Norte, a great protion of the Eastern part of Quezon, the Eatern part of Leyte and a large portion of Eastern Mindanao
Type II Climate
is the study of the earth’s atmosphere
Meteorology
is the branch of meteorology that
deals with the state of the atmosphere
averaged over a long period of time
Climatology
atmospheric condition over a short
duration, particularly the combination of
heat, moisture and wind characteristics
of the atmosphere in a day
Weather
climate that prevail over a large region of the earth’s surface
Macroclimate
areas up to several square miles (e.g. river valleys, mountain areas, watersheds and basins, shores, urban areas)
Mesoclimate
the total weather condition of an area
as generalized over a long period of
time, i.e. seasons, years, decades
Climate
incoming sunlight
Insolation
fraction of the incident radiation that is reflected by an object
Albedo
the period when the sun is farthest from the earth (δ=23.450)
Solstice
over short distances, or within few feet or inches (e.g. streets, immediate plant surroundings, garden plot)
Microclimate
sun’s position makes day and night equal (sun is directly above the observer: δ=0)
Equinox
- Stronger high and low tides
- During new and full moon (earth, moon and sun are parallel or in-line)
- Moon’s pull is supplemented or offset by sun’s gravity
Spring Tide
- Smaller high and low tides
- Moon is in the 1st and 3rd quarter (forms 900with the sun)
- Moon’s pull is stronger but the sun’s gravity lessens it.
Neap Tide
large-scale, seasonal version of the diurnal sea/land breeze that occurs along many coast, especially Arabian Sea and Indian Ocean
Monsoon
fair weather clouds that are individual, woolly, cauliflower-like masses usually moving rapidly on a strong wind.
Cumulus clouds
ow, watery, almost featureless clouds of indefinite shape * When touching the ground, it is called fog.
Stratus clouds
are wispy white clouds of tiny ice crystals * Also called ‘Mare’s tail’.
Cirrus clouds
rain clouds’
Nimbus clouds
heavy, swelling, cauliflower-like clouds that form the towering summer thunderbolts.
Cumulunimbus
Low pressure area around equator where prevailing winds are calm.
Intertropical Convergence Zone (ITCZ)
are air-mass boundaries that lie along line of low pressure
Fronts
combination of the warm and cold front, where cold air overtakes and lifts the warm front
Occluded Front
the warm air advances and the cold air retreats
Warm Front
the cold air advances and the warm air retreats
Cold Front
temporarily fixed boundary between polar and tropical air masses
Stationary Front
storm in a region of low surface pressures
Cyclone
Lowest barometric pressure (15% of the pressure outside the storm)
surrounded by a ring of towering thunderstorm
Eye of the Typhoon
most severe weather condition
30~65 km φ
eyewall
are the fastest most violent winds on earth - top speed of 110 kph near the ground and stay about 10 minutes (though a few monster tornadoes from a mile or more wide and can last for an hour or more)
Tornadoes
forms when moist, unstable air is lifted vertically into the atmosphere, resulting in condensation and the release of latent heat
Thunderstorms
When temperature rises, the expanding mercury is forced past the constriction but when the temperature falls the column of mercury remains in the tube, thus indicating the maximum temperature
Maximum Thermometer
It is basically a manometer with one end exposed to the atmosphere
It is more sensitive than aneroid barometer since it has Vernier scale on it and has already temperature, elevation and altitude corrections.
Aneroid Barometer
To provide a standardized environment in which to put or keep the temperature- and humidity-measuring instruments.
It shields the instruments against rain and direct solar radiation while allowing air to circulate freely around them.
Instrument Shelter (Thermometer Screen)
A device that measures or records the amount of sunshine at a given location.
Campbell-Stokes
Sunshine Recorder:
A type of actinometer used to measure broadband solar irradiance (short wave radiation)
Pyranometer
Used to measure intensity of direct solar radiation
Pyrheliometer
A device which uses a laser or other light source to determine the height of a cloud base.
Ceilometer
A group of instruments for simultaneous measurement and radio transmission of meteorological data: temperature, pressure, and humidity of the atmosphere. The instrument package is usually carried into the atmosphere by a balloon.
Radiosonde
comprises 8 sensors for measuring wind speed, wind direction, air temperature, RH, solar radiation, soil temp., surface wetness, and rainfall.
Automatic Weather Station
is a geologic formation or rather impervious nature which transmits water at a slow rate
compared to an aquifer.
Aquitard
a geologic formation which can absorb water but cannot transmit significant amounts
Examples are clays and shales.
Aquiclude
is a geologic formation with no interconnected pores and hence can neither absorb nor
nor transmit water
Aquifuge
is the volume of water, expressed as a percentage of the total volume of the
saturated aquifer that will drain by gravity when the water table drops due to pumping or drainage
Specific Yield
is the percentage volume of water which will not drain by gravity. This
corresponds to the field capacity or the water holding capacity of soil.
Specific Retention
is a dimensionless or fractional quantity referring to the volume of water
given out by a unit prism of aquifer when the piezometric surface or the water table drops by unit depth
- it is the same as the volume of water taken into storage by a unit prism of the
aquifer when the piezometric surface or water table rises by unit depth.
Storage Coefficient
of a well, is the discharge per unit drawdown in the well. It is measure
of the effectiveness of the well and decreases with the increase in the pumping rate and prolonged pumping.
Specific Capacity
is the process of breaking down rocks by mechanical and chemical process into
smaller pieces
Weathering
that part of atmospheric moisture that falls on the earth surface. It is
primary input into the hydrologic cycle.
Precipitation
a light steady rain in fine drops, about 0.5 mm and intensity less than 1 mm/hr
Drizzle
is the condensed water vapor of the atmosphere falling in drops (>0.5 mm,
maximum size is 6 mm) from the clouds.
Rain
is the freezing of drizzle or rain when they come in contact with cold objects
Glaze
is the frozen rain drops which falling through air at subfreezing temperature.
Sleet
is the ice crystal resulting from sublimation; i.e., water vapor condenses to ice
Snow
refers to small lumps of ice (3.5 mm diameter formed by alternate freezing
and melting, when they are carried up and down in highly turbulent air
currents.
Hail
is moisture condensed from the atmosphere in small drops upon cool surfaces
Dew
is a feathery deposit of ice formed on the ground or on the surface of exposed
object by dew or water vapor that has frozen
Frost
is a thin cloud of varying sizes formed at the surface of the earth by condensation
of atmospheric vapor, usually interfering with visibility.
Fog
is a very thin fog.
Mist
equation that implies that at t → ∞, f = 0. This is only possible if the soil is
underlain by an impermeable layer. As such, the equation will only apply for soil underlain with
impervious layers or for small t values in soils with pervious layers.
Lewis-Kostiakov (1932, 1937)
For this equation infiltration rate is a decay type function whereby continuous infiltration and
wetting of the soil will decrease infiltration due to decrease in soil profile storage potential, in
washing of fine soil particles into soil voids and swelling of soil colloids and closing of soil cracks.
Horton Equation (1940)
This equation it is analyzed infiltration as a general phenomenon of water movement in a
porous medium.
Philip (1957)
stream with continuous flow and has considerable
contribution to the baseflow
Perennial Stream
stream with periodic or seasonal flow
Intermittent Stream
stream with flow in direct response to rainfall
Ephemeral Stream
refers to the physical characteristics, dissolved chemical constituents, and bacteriological quality of water, with reference to a specific use.
Water quality
Vegetative cover over the land surface of a catchment area.
Canopy
A zone in the soil just above the water table that remains saturated or almost saturated. The extent depends upon the size-distribution of pores.
Capillary fringe
A measure of the quantity of cations a given mass of soil can hold. It is related to clay content and type, and organic matter content.
Cation exchange capacity
describe the rate of flow of water through porous media. The rate of flow of water in porous media is proportional to, and in the direction of, the hydraulic gradient and inversely proportional to the thickness of the bed.
Darcy’s law
A universal constant used in the equation relating the rate of emission of radiant energy from the surface of a body to the emissivity of the surface and the temperature of the body.
Stefan-Boltzman constant
Instrument, consisting of a porous cup filled with water and connected to a manometer or vacuum gage, used for measuring the soil-water matric potential.
Tensiometer
The rate at which water of a prevailing density and viscosity is transmitted through a unit width of an aquifer or confining bed under a unit hydraulic gradient. It is a function of properties of the liquid, the porous media, and the thickness of the porous media.
Transmissivity
