AREA 2

Soil Texture

relative proportion of sand silt and clay

Sandy soil

Coarse texture soil

Loam soil

medium textured soil

Clay soil/silty clay

Fine textured: 40℅ clay, 45℅ sand or silt

Silty clay loam

similar to silty clay but it contains substantial quantity of sand

Soil structure

arrangements of soil particles

Hygroscopic water

water held tightly to the surface of the soil

Capillary water

water held by forces of surfacr tension

gravitational water

water that moves freely in response to gravity

saturation capacity

all pores of the soil are filled with water. maximum water holding capacity

Field capacity

is the moisture content after the drainage og gravitational water

Permanent wilting point

moisture content bat which plants can no longer obtain enough moisture

Moisture equivalent

amount of water retained by a sample of initially saturated soil material

Wilting range

range in soil moisture which plants undergo permanent or irreversible wilting

available water

Soil moisture between field capacity and permanent wilting point

Basin

Region drained by a larger river system. Large watershed or catchment

Watershed

Is the total land area that contributes to the flow of a particular water body and drains to a common outlet

River basin

over 1000 km sq

Large watershed

500-1000 km sq

medium watershed

100-500 kmsq

Small watershed

10-100 kmsq

micro watershed

under 10 kmsq

main stream gradient

change of elevation of the of the mainstream from the farthest point watershed outlet to the main stream length

Drainage drnsity

dissection of the basin that determines it’s response to a rainfall input

Basin shape

it affects the streamflow hydrograph and peak flow rates. Ratio of the basin area and length of the basin measured along a straight line from the outlet to the divide nearest to the head of the longest stream

Circulatory Ratio

ratio between the area of the circle having the same perimeter and the actual area of the watershed

Elongation Ratio

A is the ratio of the equivalent circle and the actual perimeter of the watershed

Relief ratio

ratio of the total basin relief (difference between highest and lowest elevation) to the maximum basin length

relative relief

ratio of the maximum watershed relief(highest elevation) to the perimeter of the basin

Stream order

is a measure of the relative size of stream or the amount of branching within a basin to describe the drainage network in a watershed

Bifurcation ratio

is a quantitative measure of drainage pattern of a watershed. Ratio of the number of streams in any order to the number of the next order. found between 2 to5 and may have a mean value of 3.5

Lower bifurcation

higher chance of flooding

Soil Erosion

is the detachment and transport of soil particles by natural or anthropogenic causes

Eroding agents

rainfall/raindrop run off wind

Rainfall Erosivity

The capacity of rainfall to cause erosion

Soil erodibility

The vulnerability or suspectibility of soil to erosion

Sheet erosion

Overland flow. removal of soil in thin layers from slowing land

Interill erosion

is splash and sheet erosion combined

Rill erosion

Is the detachment of soil by a concentrated flow of water. Intermediate stage of erosion involving smaall channels

Gully erosion

produce channels larger than rills this channel becomes to deep and wide

Soil erosion plots

Bare fallow, 9% slope 72.6 ft length

Crop rotation

use good crop rotation practices

relay cropping

Planting along countours

Stubble mulching

leaving crop residues in the field and later incorporating them into the soil

Wattling

consist of interwoven fences of brushwood or twwigs in shallow trenches/ canal and supported by pegs

Runoff storage or Detention structure

impounding structure and reservoirs that reduce velocity and modulate volume of water

Diversion channels

Construction of cit offs and detour channels

Bed load

sediment near or few inches from the stream bed and move by crawling or sliding

Suspended load or suspension

Sediment or soil particle suspended in the water body. Sediment that is in motion in a river. Transport of fine soil particles suspended in flowing water

wash load

suspended and saltation

Trap efficiency

The percentage of incoming sediment retained in the reservoir

Abrasion

The process where particles of soil mixed with running water create abrasive force

Active gullies

Gullies whose size and dimensions continue to increase over time: commonly found in plains

Attrition

Mechanical breakdown of soil particles due to collision and friction between particles in water

Gully Development stage

Four stages of gully formation, development, healing and stabilization

Development stage (Gully)

The gully stage involving headward extension and enlargement in width and depth reaching the c-horizon

Healing stage (gully)

Vegetation begins to grow in the gully and significant erosion ceases

Stabilization Stage gully

Final gully stage where slope becomes stable and erosion halts

Inactive Gullies

Gullies that have stopped enlarging, often stabilized in Rocky areas

Rill Erosion

Intermediate stage of erosion involving small channels (rills) formed by running water, removable by tillage

Water Erosion

Soil loss caused by the action of water, progressing from splash to sheet, till, gully and stream

Saltation

Transportation of medium size soil particles that bounce or hop along stream bed

Slash Erosion( Splash Erosion)

Initial stage of erosion caused by raindrop impact, detaching and splashing soil particles into the air

Streambank Erosion

Removal of soil from streambanks due to water flow, often worsened by human activity

Surface creep

Transportation of course particles by rolling or sliding aling the ground surfacr

C-horizon

A soil layer beneath the topsoil and subsoil composed of weathered parent material, less affected by biological activity

Subsoil

The layer of soul beneath the topsoil typically less fertile but more compact and resistant to erosion

Hydraulic action

Detachment of soil due to high pressure water flow that compresses air in soil voids exerting forces on particles

Hydraulic Pressure

Pressure generated by compressed air in soil voids due to fast moving water leading to soil detachment

Acid rain

Rain rhat has made acidic by pollutants in the air

Wet deposition

acids occurs when any precipitation

Dry deposition

when particles and gases stick to the ground, plants or other surfaces

Eutrophication

excessive plant growth and decay

Weather

Atmospheric conditions over a short duration

climate

Total weather condition of an area as generalized over long period of time

Meteorology

is the study of the earth’s atmosphere

Climatology

branch of meteorology that deals with state of the atmosphere averaged over a long perio of time

Dynamic meteorology

Study of winds and weather patterns

Physical meteorology

Use radar and satellite and the study of phenomenon, precipitation, pollution

Synoptic meteorology

Study of day to day weather

Insolation

Incoming solar radiation

Albedo

Fraction of the incident radiation that is reflected by an object

Solstice

the period when the sun is farthes from the earth

Equinox

Suns position makes day and night equal

macroclimate

climate that prevail over a large region of the earth’s surface

me so climate

areas upto several square miles

microclimate

over short distances, or within few feet or inches

cumulus clouds

Fair weather cluds

Stratus clouds

Low watery almost feature less clouds indefinite shapes

Cirrus clouds

are wispy White clouds of tiny ice crystals

Interflow

It refers to the lateral movement of water in the soil.

Apparent specific gravity

This refers to the ratio of the dried mass of the soil per unit

volume to the mass of water at the same volume

Soil Structure

refers to the clustering of soil particles into aggregates of

various shapes, sizes, and stability.

Soil Density

a measure of the compaction of soil. It is the ratio of the soil

mass to its volume

Bulk Density

refers to the ratio of the mass of the soil particles to its

total undisturbed volume.

Particle Density

refers to the ratio of the mass of the soil particles to its

volume.

Specific Gravity

this refers to the ratio of the density of the soil to the

density of water.

Apparent SG (ASG)

Ratio of bulk density to the density of water

Real SG (RSG)

Ratio of particle density to the density of water

Porosity

refers to the ratio of the volume of the void spaces to the total

undisturbed volume of the soil. The volume of void spaces are the spaces within

the soil that can be occupied by air or water