SOIL AND WATER RESOURCE CONSERVATION ENGINEERING Flashcards
Implies utilization without wastes
Conservation
Continuous high level of crop production while improving environment quality
Conservation
True or False. Soil and water conservation is based on full integration of engineering, atmospheric, plant and soil science. It requires knowledge of the soil -plant-water interactions, particularly conserving the soil physical, chemical and engineering characteristics.
True
One major cause of water pollution
Soil erosion
It is said that agriculture contributes to 60-80% of total water use . 40% of irrigation water was not available to crops. Give the causes of this water loss
Conveyance, seepage, percolation, evaporation, transpiration
Enumerate some physical means of retaining raifall in soil and reducing evapotranspiration
Level terracing, reservoirs, contouring, pitting, water harvesting techniques, modified tillage, crop management techniques
Total land area of Philippines
30 M ha
Agricultural land in the Philippines is about 42%. What is its value in terms of ha
12.57 M ha
PD 1067 is also known as
Water Code of the Philippines
Located below 50 m above mean sea level
Shallow well areas
Located above 50 m above mean sea level
Deep well areas
Geologic features lying at a depth more than 20 meters below the ground
Aquifers
Areas with insufficient data to be classified as either shallow or deep well areas because of varying depth
Difficult areas
Average growing rate of Philippine population
2.3 %
On 1990, how much of the total land area of the country was affected by soil erosion?
45%
Annual average nutrient loss in terms of fertilizer requirement. In tons, how much N, P, K were lost?
194,000 tos N, 40, 000 tons P, 30,000 tons K
Issues and problems attendant to soil and water conservation and utilization.
Land and water resource degradation, allocation, data availability and reliability, support
Major sources of water
Rainwater, surface water, ground water
Movement of water on the earth’s surface and through the atmosphere
Hydrologic cycle
Water vapor in the atmosphere
Humidity
Any aqueous deposit in liquid or solid form, that develops in a saturated atmospheric environment and generally falls from clouds
Precipitation
True or false. Evaporation from ocean surface is the chief source of moisture for precipitation
True
Four primary reasons of condensation or sublimation of atmospheric moist
Adiabatic cooling, mixing of air masses of varying temperatures, radiation cooling, contact cooling
Tiny liquid water droplets. 0.1-0.55 mm diameters and usually falls less than 1 mm per hour and also appears to float
Drizzle or mist
Liquid water drops greater the 0.5 mm diameter
Rain
Defined as the amount of liquid precipitation
Rainfall
Ice coating generally clear and smooth formed on exposed surfaces by the freezing of supercooled water deposited by rain or drizzle
Glaze
Specific gravity of glaze
~0.8 to 0.9
White opaque deposit of ice granules separated by trapped air and formed by rapid freezing of supercooled water drops
Rime
Specific gravity of rime
~0.2-0.3
Composed of ice crystals, chiefly in complex, branched hexagonal form, and often agglomerated into snowflakes
Snow
The average diameter for snowflakes
~ 100 mm
Balls of ice produced in convective clouds
Hail
Transparent, globular, solid grains of ice formed by the freezing of raindrops or refreezing of melted ice crystals as it falls in a layer of sub freezing air near the surface
Sleet
It represents the saturation of air near the ground surface
Fog
A process wherein acid pollutants from the atmosphere are being deposited in dry and wet forms to the Earth’s surface
Acid Deposition
Wet deposit of acid pollutants
Acid Precipitation
Occurs when radiant energy from the sun heat water, causing water molecules to rise into the atmosphere
Evaporation
The combined evaporation of the soil surface and the plants
Evapotranspiration
Rain that falls through the vegetation without being intercepted
Through fall
The movement of water from precipitation into the soil
Infiltration
Water that doesn’t infiltrate the soil flows on the surface as
Runoff
True or falls. The Earth’s continent experience runoff because of the imbalance between precipitation and evaporation
True
Plot of discharge against time
Hydrograph
Difference between peak rainfall and peak discharge
Lag time
The height at which a flood could occur, variable from river to river
Bankfull discharge
A line in the hydrograph that shows how much water is in the river
Discharge line
Ground water runoff, normal discharge of the river or stream or channel
Base flow
Volume of water reaching the river from surface runoff
Direct runoff
Factors affecting runoff
Climate, physiographic factors
Also called the concentration curve; represents the increase in discharge due to gradual build up of storage in channel and over the catchment area
Rising limb
True or False. Fan shaped or nearly circular shaped basin/catchment has slower discharge than fern-shaped
False. The reverse is true. It is because the time of concentration of the catchment is much lower than the fern or leaf shaped.
Indicates the peak flow or the maximum amount of flow at the basin outlet
Crest segment
From point of inflection at the end of crest segment to base flow.
Falling limb
The time required for water to flow from the most remote point to the mouth of the watershed once the soil has become saturated and minor depression filled
Time of concentration
The ratio of the peak runoff rate to the rainfall intensity
Runoff coefficient
a process by which soil is removed from the Earth’s surface by exogenetic processes
such as wind or water flow, and then
transported and deposited in other
locations.
Erosion
natural erosion (soil-forming and soil eroding processes) which maintain the
soil in favorable balance.
Geological erosion
removal of surface soil takes place
at much faster rate than it can be
built up by the soil forming
processes
Accelerated erosion
Two interactive processes of erosion
Detachment and Transport
EROSION SUB-PROCESSES
Detachment by rainfall
Transport by rainfall
Detachment (scour) by runoff
(overland or channelized flow)
Transport by runoff
Factors affecting erosion by water
Climate
Soil
Vegetation
Topography
Disturbances
The greatest natural disturbances in the ecosystems
Fires
soil detachment and transport
resulting from the action of raindrop
the first stage of soil erosion by
water
Raindrop erosion or splash erosion
the removal of soil in thin layers by
raindrop impact and shallow surface
flow
its soil detaching and transporting
capabilities are small
Sheet erosion
results in loss of the finest
soil particles that contain nutrients
and organic matter in the soil
Skimming
The intermittent process of
transforming to gully erosion. Common in bare agricultural land,
overgrazed land and freshly tilled soil
where soil structure has been
loosened
Rill erosion
common in bare agricultural land,
overgrazed land and freshly tilled soil
where soil structure has been
loosened. It can be obliterated by tillage
Rill erosion
The advanced stage of rills. It is formed when the depth and
width of the rill is > 50 cm
Gully erosion
4 classes of gully
G1, G2, G3, G4
Depth, width and side slope of G3
3.0-9.0 m, 18 m, 6-12 %
Stages of Gully Development
FORMATION STAGE
DEVELOPMENT STAGE
HEALING STAGE
STABILIZATION STAGE
Processes of gully formation
Waterfall erosion
Channel erosion
Alternate freezing and melting of snow
Undercutting, landslides, mass
movements of soil
It can be used to predict soil erosion losses
,guide the selection of agricultural practices such as cropping and management
systems
, guide in determining the on-site effects of land use and crop management
changes
, and provide baseline data for conservation planning
UNIVERSAL SOIL LOSS ESTIMATION
It can be used to predict soil erosion losses
,guide the selection of agricultural practices such as cropping and management
systems
, guide in determining the on-site effects of land use and crop management
changes
provide baseline data for conservation planning
it estimates sheet erosion as the product of a series of terms for rainfall, soil, slope
gradient, slope length, crop and cover management and conservation factors this permits the extensive tabulations of individual factors, incorporating vast
amounts of research data
Universal Soil Loss Estimation
Standard agricultural plots
72.6 feet long and 6 feet wide, with 9% slope
a quantitative measure of erosion potential of rain, allows for spatial estimation of basic erosion risks in different areas.
Rainfall erosivity
The detachment and transport of soil by a concentrated flow of water and the detachment and transport of soil by a concentrated flow of water
Rill erosion
The ratio of the circumference of a circle of the same area as the basin to the basin perimeter
Circulatory ratio
A stream that flows only in direction response to precipitation
Ephemeral stream
Hydrograph with a unit volume of direct runoff for a given storm duration
Unit hydrograph
When the viscous forces are weak relative to inertial forces, the flow is
Turbulent
A channel having a steep slope
Chute
The distance between adjacent terraces
Vertical interval
What percentage of the water extracted by plant roots is transpired
95-99%
suggested that splash erosion is a function of soil and
rainfall properties
Ellison
slope-practice
equation
Musgrave equation
developed an expression for the claypan soils of
Missouri
Smith and Whitt
Precipitation associated with the movement of air masses due to a difference in barometric pressure
Cyclonic
The method of determining average areal precipitation which accounts for the effect of topography and unequal gage density
Arithmetic average and Thiessen method
An equation or method used in the estimation and representation of evapotranspiration rate
Hargreaves Equation
The rate of evapotranspiration occurring under the field conditions for the given crop, soil moisture and meteorological conditions
Actual crop evapotranspiration
Fraction of sheet and rill erosion that actually reaches has reference point of discharge
Sediment delivery ratio