Soil Moisture, SWIM, and Pumps

Soil Moisture

• Available moisture is the difference in soil moisture content between field capacity and permanent wilting point.

Consumptive Use

• Consumptive use is the total water loss in an area through plant transpiration, soil and water surface evaporation, and plant tissue building.

Capillary Water

• Capillary water refers to water held by surface tension forces as a continuous film around soil particles.

Small Water Impounding Management (SWIM) Projects

• SWIM projects typically involve small-scale water impounding dams with a structural height not exceeding 30 meters.

Allowable Depletion of Soil Moisture

• Soil moisture allowable depletion for most crops is 50%.

Pump Selection

• Centrifugal pumps are suitable when the suction lift is 6 m.

Soil Moisture Tension

• At a tension of 1.5 atmospheres, the soil moisture content corresponds to the saturation point.

Soil Moisture

• Capillary water in smaller soil pore spaces defines soil moisture.

Interflow

• Interflow is water that penetrates the soil and flows laterally to a stream channel in the surface soil.

Runoff Coefficient

• Runoff coefficient defines the rate of surface runoff relative to the rate of rainfall to achieve equilibrium.

Piezometric Surface

• Piezometric surface is the line defined by the water level in a group of artesian wells.

Safe Yield

• Safe yield signifies the maximum water quantity guaranteed during critical periods.

Arch Dams

• Arch dams are suitable for narrow canyons.

Irrigation Methods - Sprinkling

• Sprinkling is optimal for irrigation on irregular topography and row crops.
• Sprinkling offers the best control of water supplied in irrigation.

Hydraulic Gradient

• Hydraulic gradient is the locus of the elevation to which water rises in a piezometric tube.

Overflow

• Overflow describes the sheet of water flowing over a dam or weir crest; also known as a nappe.

Super Critical Flow

• Super critical flow happens when velocity exceeds critical velocity and depth is less than critical depth.

Riparian Rights

• Riparian right is a principle recognizing a riparian owner's right to reasonable streamflow use on riparian land, as defined in English Common Law.

Groundwater for Plant Growth

• Groundwater is effective for plant growth via capillary action when within the depth from which the plants obtain their major needs.

Managing Farms with High Water Tables

• Non-application of water during the entire growing season is the best way to manage a farm with a high water table to obtain optimum yield.

Total Dynamic Head

• Total dynamic head is the sum total of head above the vapor pressure of the liquid being pumped at a given pumping temperature.

Pressure Head Variation in Sprinklers

• The recommended pressure head variation between the first and last sprinkler in a lateral is 20%.

Infiltration Rate

• Infiltration rate measures the rate at which water percolates through the soil surface.

Steady Uniform Flow

• Steady uniform flow represents the simplest form of open-channel flow computation.

Spillway

• A spillway releases surplus floodwater from a dam that cannot be held in active storage.

Trapezoidal Cross Section Design

• The most efficient trapezoidal cross section is where the width of the bottom is twice the depth.

Trickle Irrigation

• Trickle irrigation is the frequent, slow water application to a plant's specific root zone area.

Border Irrigation

• Border irrigation is a land divided into strips by small earth bonds, typically sloping away from a farm channel.

Artesian Well Free Flow

• Free flow in artesian wells occurs when the piezometric level is higher than the top of the well.

Dam Site Identification

• High population density to supply needed labor is not part of the guidelines for identifying potential dam sites.

Turgor Pressure

• Turgor pressure is the water pressure within leaf cells.

Irrigation

• Irrigation is the artificial application of water to soil for crop production.

Mulching

• Mulching minimizes the effects of raindrop erosion.

Drip/Trickle Irrigation

• Drip or trickle irrigation involves applying small amounts of water through tubing networks.

Gravitational Water

• Gravitational water moves freely and drains out of the soil.

Uplift Pressure

• Uplift pressure acts under a gravity dam, causing an overturning effect.

Penman Method

• The Penman method is the most elaborate way to compute potential evapotranspiration.

Direct and Cascade Supply

• Direct supply and cascade supply are methods to supply water in the basin.

Soil Compaction

• Compacting a soil sample increases its bulk density.

Field Capacity

• Field capacity indicates the moisture content of soil at a tension of 1/3 atmosphere.

Water Table Well

• Water table well is another term for gravity well.

Land Slope

• Land slope is the measure of ground level difference between two points in a field, expressed as a percentage or meters per 100 m horizontal distance.

Head Gate

• Head gate is placed across a stream to divert water.

Small Wells

• Small wells are best suited for development using compressed air.

Mixed Flow Pumps

• Mixed flow pumps are used for low head, high discharge operations.

Apparent Specific Gravity

• Apparent specific gravity is the quotient of dry soil weight (including air space) to the weight of an equal water volume.

Field Capacity Defined

• Field capacity is the soil moisture content after gravitational water has been removed.

Readily Available Moisture

• Readily available moisture is equivalent to 75% of available moisture.

Subsurface Irrigation

• Subsurface irrigation can also be referred to as controlled seepage.

Water Rights & Appropriation Act

• Appropriation Act is the water right based on the concept of first in time, first in right.

Seepage

• Seepage is the lateral water movement in the soil.

Soil Density

• Soil density is the mass per unit volume of soil particles.

Void Ratio

• Void ratio is the ratio of pore volume to solid volume in soil.

Capillary Water

• Capillary water is held by surface tension forces and continuous films around soil particles.

Hygroscopic Water

• Hygroscopic water is held tightly to the surface of soil particles by adsorption forces.

Nappe

• A nappe is the sheet of water that overflows a weir.

Low Pressure Sprinklers

• Sprinklers that operate with 20-40 psi of pressure are low pressure sprinklers.

Transition Structures

• Transition structures are used to turn conduits of varying sizes and shapes.

Basin Flooding

• Basin flooding is a surface irrigation method where a small area is enclosed by levees.

Evapotranspiration

• Evapotranspiration refers to consumptive use by crops.

Cut Off

• Cut off refers to a natural or artificial channel that shortens a meandering stream.

Irrigation Efficiency Defined

• Irrigation efficiency evaluates water losses from the source to the point of use during irrigation.

Distance To The Bottom Of The Pipe

• Distance from the surface to the bottom of the pipe defines pipe depth in a drainage system.

High Torque Windmill Design

• High torque design characterizes multi-blade windmills.

Velocity

• Velocity measures the speed at which water flows in a channel.

Discharge Calculation

• Discharge is calculated by multiplying the cross-sectional area with the velocity of flow.

Infiltration Rate

• Infiltration rate is the time required for water to enter the soil, depending on water depth and soil type.

Infiltration Rate (Soil)

• Infiltration rate is the soil characteristic that determines the maximum rate at which water enters the soil.

Apparent Specific Gravity

• Apparent specific gravity is the ratio of bulk density to water density.

Hydraulic Radius (Hydraulics)

• Hydraulic radius is the term A/P in open channels.

Roughness Coefficient

• Roughness coefficient is necessary to design open channel and know the material in the channel bed.

Influent Stream

• Influent stream, also known as a losing stream, has a water table below the stream channel bed.

Culvert

• A culvert is a closed conduit typically used to convey water under a roadway, embankment, or dikes.

Check Contour Method

• Check contour involves building longitudinal levees parallel to the contour, connected with right-angle levees.

Gate

• A gate controls water flow to or from a pipeline.

Vent

• A vent admits air into or expels air from a pipeline.

Dam

• A dam is a barrier constructed to hold back water and raise its level.

Bifurcation

• Bifurcation is an irrigation structure that divides water into two main laterals.

Evapotranspiration Defined

• Evapotranspiration is the combined process of evaporation and transpiration from plants.

Discharge

• Discharge is the volume of water flowing each second, measured in m³/sec.

Trapez Foil Cross-Section

• For an efficient trapezoidal cross-section, the width of the bottom is twice the depth.

Irrigation Efficiency

• Irrigation efficiency is the ratio of actual production to expected production under ideal conditions.

Irrigation Frequency

• Irrigation frequency is the number of days between irrigation periods without rainfall.

Irrigation Period

• Irrigation period is the number of days allowed for irrigation in a design area during peak consumptive use.

Capillary Action

• Capillary action is surface tension causing liquids to rise or fall in small tubes.

Effective Rainfall

• Effective rainfall is the amount of rainfall in the rootzone.

Turnout Structures

• Turnout structures divide and distribute water flow in the desired direction.

Weir

• A weir is a regular notch through which irrigation stream flows, built portably or stationary.

Hydraulic Radius of Semicircle

• For the most efficient circular cross-section (semicircle), the hydraulic radius equals ¼ of its diameter.

Soil Density

• Soil density measures the mass per unit volume of a soil particle.