Runoff - Wells

controls structures in canals or streams

Weirs

the following is not a direct stream flow determination technique

slope-area method

composed of surface runoff, prompt interflow and channel precipitation

direct runoff

Denotes as delayed groundwater flow reaching a stream. Also called as groundwater

Base flow

has flows in the stream during wet season due to contribution of groundwater

Intermittent stream

A stream that contains water at all times except during extreme drought

Perennial Stream

A stream channel that carries water only during and immediately after periods of rainfall or snowmelts.

ephemeral stream

Does not have any base flow contribution.

ephemeral stream

basin having low drainage density give smaller peaks in flood hydrograph

for a given storm, assuming other factors remain constant

a unit of hydrograph has one unit of

direct runoff

on a flood hydrograph to obtain the magnitude of effective rainfall

base flow

also known as phreatic water

groundwater

a rise in a liquid above the level of zero pressure due to net upward force produced by the attraction of the water molecules to solid surface.

capillary rise

a water bearing geologic formation or stratum capable of transmitting water through its pores at rate sufficient for economic extraction extraction by wells.

Aquifer

A geologic formation, which can absorb water but cannot transmit significant amounts. Clay formations are an example

Aquiclude

A geologic formation of rather impervious nature, which transmit water at water at a slow rate compared to an aquifer (insufficient for pumpung from wells). e.g sandy clay

Aquitard

A geologic formation with no interconnected pores and hence absorb nor transmit water. these are formations made of massive compact rocks without any fractures.

Aquifuge

geological formation arranged in decreasing economic considerations

aquifer, aquiclude, aquitard, aquifuge

well drilled into an artesian aquifer and water rises above the ground like a spring

free flowing well

measures the water being capacity of geologic formation n=Vv/Vt

porosity

Percentage volume of water of an aquifer, which will not drain by gravity

Specific retention

volume of water expressed as a percentage of the total volume of the saturated aquifer that will drain to pumping or drainage. it is ratio of the volume of water that, after saturation, can be drained by gravity to its own volume.

Specific yield

The volume of water that can be extracted by force of gravity from a unit volume of aquifer material.

Specific yield

It is the volume of water that an aquifer releases from or takes into storage per unit surface area of aquifer per unit change in the component of head normal to that surface

Storage coefficient

A stream that provides water to the water table

influent

Other term for tributary

affluent

When the water table intersects the stream channel, water from water table moves toward the stream

Effluent streams

Surface joining the static water levels in several wells penetrating a confined aquifer

Piezometric surface

re expected in areas where elevation of the piezometric head line is above the elevation of the ground surface

Flowing artesian wells

Above atmospheric pressure

Water present in artesian aquifer is usually

Actual velocity of flow and discharge velocity

Term used in groundwater hydrology are not synonymous

Is valid porous media flow if the Reynolds number is less than unity. This Reynolds number is defined as discharge velocity x average grain size and divided by μ

Dacry’s law

The flow capacity of an aquifer per unit width under unit hydraulic gradient and is equal to the product of permeability times the saturated thickness of the aquifer.

transmissibility

When there is an increase in the atmospheric pressure, the water level in a well penetrating a confined aquifer

Decreases

is the discharge per unit drawdown at the well

Specific capacity of a well

Maximum head of shallow wells

6 m

The recommended standard method for the definition and computation of the reference evapotranspiration

FAO Penman Monteith

it is the average interval of time within the magnitude of given event will be equalled or exceeded at least on the average.

Return period

The greatest distance at which an observer can see and identify prominent objects.

Horizontal visibility

Term synonymous to return period

Recurrence interval

A line that connects points of equal elevation above a reference level, most often sea level.

Contour

portion of the precipitation that makes way towards stream channels, lakes, oceans as surface or subsurface flow

runoff

Provides the relationship between stage and discharge

Rating curve

Height of water level in a stream

stage

Graph of runoff vs time.

Hydrograph

was made of overland flow, interflow and baseflow.

Hydrograph

In a watershed

Larger watershed produces larger runoff than smaller watershed.

it is time from the beginning of the rising limb to the occurrence of the peak discharge.

Time of peak

it is the time required for the water to travel from the most hydraulically remote point in the basin to the basin outlet

Time of concentration

it is the time between the center of the mass of the effective rainfall hyetograph and the center of mass of the direct runoff hydrograph.

Lag time

it is the duration of the direct runoff hydrograph

Time base

Excess rainfall, is the amount of rainfall that becomes the direct runoff that becomes the direct runoff of the watershed outlet.

Effective rainfall

it is the result of the total or gross rainfall after losses are deducted.

Effective rainfall

Some of the losses includes infiltration and absorb by the soil and rainfall stored in depressions

Effective rainfall

a chart or function describing the temporal distribution of precipitation during a storm event, at a point, or over an area.

hyetograph

the flow unaffected by works of man

Virgin flow

is a plot of the stream discharge against the percentage of times the flow is equalled or exceeded.

Flow duration curve

Study demand line drawn from a ridge in the curve did not interest the mass curve again. This represents that the demand cannot be met by the inflow as the reservoir will not refill

Flow mass curve

A demand line drawn tangent to the lowest point in a valley of the curve does not intersect the mass curve at an earlier time period, it represents that the reservoir will not be full at the start of the dry period.

Flow mass curve

Is an integral curve of the hydrograph.

Flow mass curve

is a hydrograph of infinitely small duration and of unit rainfall excess.

Instantaneous unit hydrograph

to estimate the magnitude with a return period of T years, the following data pertaining to annual flood series is sufficient mean, standard deviation and coefficient of skew of log discharge data.

The log-pearson type III method

a flood with a recurrence interval of 2.33 years

Annual flood

an extreme large but physically possible flood in the region

Probable maximum flood

smaller than probable maximum flood in the region

Standard project flood

Use equation of continuity only

Hydrologic flood-routing methods

both the equation of motion and equation of continuity

Hydraulic methods

for unsteady open-channel flow are continuity and momentum equation

St Venant equations

Reach during the passage of a flood wave is function of outflow only.

The prism storage in a river

A flood through a reach the point of intersection of inflow and outflow hydrographs coincides with the peak of outflow hydrograph when the inflow is into a reservoir with an uncontrolled outlet.

In routing

Is a hydrologic channel-routing method.

Muskingum method of flood routing

Is one in which the storage varies linearly with the outflow rate

Linear reservoir

is a line on the basin map connecting points equal time of travel of the surface runoff to the catchment outlet.

Isochrone

An aquifer confined at the bottom but not a the top is called

Unconfined aquifer

Are expected in areas where the elevation of the piezometric head line is above the elevation of the ground surface

Flowing artesian wells

Water present is usually above the atmospheric pressure

Artesian aquifers

Are not synonymous actual velocity of flow and discharge velocity

Groundwater hydrology

Unit of intrinsic permeability

Cm^2

The dimensions of the coefficient of transmissibility T

L^2/T

Dimensions of the storage coefficient S

dimensionless

is storage coefficient/ aquifer depth

Specific storage

Discharge per unit drawndown at the well

Specific capacity of a well

In one-dimensional flow in an unconfined aquifer between two water bodies, when there is a recharge, the water table profile

A part of an eclipse

In one-dimensional flow confined aquifer between two bodies the piezometric head is

Straight line

For one-dimensional flow without recharge in an unconfined aquifer between two water bodies the steady water table profile

A parabola

The discharge per unit drawdown at a well

Specific capacity

The specific capacity of the well in confined aquifer under equilibrium conditions and within the working limits drawdown.

Decreases the drawdown increases