Environmental Measurement Techniques

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Questions and Answers

What is effective rainfall in the context of certain procedures?

Rainfall excess when subsurface runoff is excluded (correct)

Total rainfall minus subsurface runoff

Rainfall that does not reach the soil

Rainfall that contributes to evaporation

Which branch of hydrology is primarily concerned with engineering applications?

Theoretical hydrology

Engineering hydrology (correct)

Agricultural hydrology

Meteorological hydrology

What is an ephemeral stream?

A stream that responds only to precipitation (correct)

A stream that flows only when groundwater levels are high

A stream that flows all year round

A stream that is permanently dry

What does the envelope curve represent in hydrology?

The boundary within which data points are contained Signup and view all the answers

What is the purpose of an evaporimeter?

Measuring water evaporated into the atmosphere Signup and view all the answers

Which description best fits extreme rainfall?

The statistical upper limit of precipitation for a duration Signup and view all the answers

What is meant by the term 'evapotranspiration'?

Water lost through evaporation and plant transpiration Signup and view all the answers

What defines an experimental basin in hydrology?

A basin modified to study hydrological cycle effects Signup and view all the answers

What is meant by a recession in hydrology?

A period of decreasing discharge after reaching a peak. Signup and view all the answers

Which term describes the long-term average interval of time within which a certain event will occur, such as a flood peak discharge?

Recurrence interval Signup and view all the answers

What does a rating curve (or rating table) represent?

The relationship between stage and discharge at a hydrometric station. Signup and view all the answers

In hydrology, what is a representative basin used for?

Conducting hydrological studies under constant conditions. Signup and view all the answers

How is the peak rate of storm runoff estimated using the rational method?

By multiplying the catchment area with peak rainfall and a runoff coefficient. Signup and view all the answers

What describes the concept of remote sensing in hydrology?

Measurement or acquisition of information using recording devices not in contact with the phenomenon. Signup and view all the answers

Which term refers to the mathematical representation of the behavior of a hydrological system due to specified input?

Response function Signup and view all the answers

What is reservoir routing primarily used for?

To compute the movement and change of shape of a flood wave. Signup and view all the answers

What does the term 'actual evapotranspiration' refer to?

Sum of water evaporated from soil and plants at natural moisture levels Signup and view all the answers

What is the significance of the 'annual maximum series' in hydrology?

It provides a series of values of the highest annual discharge peaks Signup and view all the answers

Which of the following best describes 'advection'?

Transfer of air-mass properties through atmospheric velocity fields Signup and view all the answers

What does 'annual storage capacity' refer to?

Total volume of water that can be stored to manage seasonal variations Signup and view all the answers

In hydrology, what is indicated by the 'antecedent precipitation index'?

Weighted sum of past daily precipitation amounts as a soil moisture indicator Signup and view all the answers

What is 'annual runoff' specifically referring to?

Volume of water that flows out of a drainage area during a year Signup and view all the answers

How is the 'active basin area' defined?

Region of a basin that contributes to the runoff excluding undrained parts Signup and view all the answers

What does the term 'annual series' refer to in hydrology?

A hydrological series representing characteristics across multiple years Signup and view all the answers

What does skewness indicate in a frequency or probability distribution?

The degree of asymmetry of the distribution Signup and view all the answers

What is the purpose of a staff gauge in a water body?

To indicate the level of the water surface Signup and view all the answers

Which term describes the relationship between stage and discharge at a river cross section?

Stage-discharge relation Signup and view all the answers

What does the standard error of estimate measure?

The variance of the observed values about a regression line Signup and view all the answers

What is a standard project flood?

The expected discharge from severe meteorological and hydrological conditions Signup and view all the answers

What characterizes a stationary process in statistics?

Mean and variance are independent of time Signup and view all the answers

How is a standardized variate achieved?

By subtracting the mean and dividing by the standard deviation Signup and view all the answers

What is the standard deviation commonly used to measure?

The dispersion of a frequency distribution Signup and view all the answers

What is the purpose of continuous or frequent standardized measurement in environmental surveillance?

For warning and control Signup and view all the answers

What does the multi-annual mean represent?

The arithmetic mean of occurrences over several years Signup and view all the answers

Which method involves measuring discharge from a boat while traversing the stream?

Moving boat method Signup and view all the answers

What is the primary focus of multiple regression analysis?

Finding the relationship between a dependent variable and multiple independent variables Signup and view all the answers

How is multi-annual storage capacity defined?

Volume of water stored over more than one year to manage variations Signup and view all the answers

What type of flow is referred to as 'natural flow'?

Flow in a stream under natural conditions Signup and view all the answers

Which of the following accurately describes the normal hydrological value?

It is the mean over a consensus period that aligns with longer averages Signup and view all the answers

Which statement best describes multiple correlation?

It assesses the interdependence of at least two variables Signup and view all the answers

Study Notes

Surveillance

Involves frequent standardized measurement and observation of the environment
Used for warning and control

Moving Boat Method

Measures discharge from a boat by traversing the stream along the measuring section
Continuously measures velocity, depth, and distance travelled

Multi-annual Mean

Arithmetic mean of data occurrences over multiple years
Calculated for a specific date or period within the year
Example: Multi-annual mean monthly discharge for April

Multi-annual Storage

Volume of water that can be stored in a reservoir to cope with variations in inflow and demand over multiple years
Synonymous with multi-annual storage capacity

Multiple Correlation

Synonymous with multiple regression
Interdependence of more than two variables

Multiple Correlation Coefficient

First product-moment correlation between the actual values of the "dependent" variate in multiple regression and the values given by the regression equation
Synonymous with correlation coefficient and covariance

Multiple Regression

Regression of a "dependent" variate on more than one "independent" variate
Synonymous with multiple correlation

Muskingum Method

Approximate hydrological method of flood routing
Based on the equation of continuity for a reach and a storage equation expressing the linear dependence of the water volume in the reach on the weighted inflow and outflow discharges

Natural Flow

Flow in a stream under natural conditions

Normal Distribution

Mathematically defined, symmetrical, bell-shaped, continuous probability distribution
Traditionally assumed to represent random errors
Synonymous with Gaussian distribution

Normal Hydrological Value

Mean value of a hydrological characteristic taken over a period selected by consensus
Mean over any longer period does not significantly differ

Accumulative Precipitation Gauge

Precipitation gauge used at stations visited only at long-spaced time intervals

Active Basin Area

Basin area excluding undrained parts

Actual Evaporation

Quantity of water evaporated from an open water surface or from the ground

Actual Evapotranspiration

Sum of the quantities of water evaporated from the soil and the plants when the ground is at its natural moisture content

Advection

Process of transfer of air-mass properties by the velocity field of the atmosphere

Altitude

Vertical distance of a level, a point or an object from mean sea-level

Annual Exceedence Series

Series of values of independent events, such as floods, occurring above a base value
Number of values in the series equals the number of years of the record

Annual Flood

Highest peak discharge in a water year
Flood that has been equalled or exceeded once each year on average

Annual Flow

Total volume of water that flows during a year
Usually refers to the outflow of a drainage area or river basin

Annual Maximum Series

Extreme-value series with largest annual values

Annual Minimum Series

Extreme-value series with smallest annual values

Annual Runoff

Total volume of water that flows during a year
Usually refers to the outflow of a drainage area or river basin

Annual Series

Hydrological series with terms representing some characteristic or element for each of a series of years

Annual Storage

Volume of water that can be stored in a reservoir to cope, partly or completely, with seasonal variations in inflow and demand

Annual Storage Capacity

Volume of water that can be stored in a reservoir to cope, partly or completely, with seasonal variations in inflow and demand

Antecedent Precipitation Index

Weighted summation of past daily precipitation amounts, used as an index of soil moisture

Elevation

Vertical distance of a level, a point or an object considered as a point, measured from mean sea-level

Empirical Flood Formula

Formula expressing peak discharge as a function of catchment area and other factors

Engineering Hydrology

Branch of applied hydrology dealing with hydrological information intended for engineering applications (planning, design, operation, and maintenance)
Example: Design and operation of engineering measures and structures

Envelope Curve

Smooth curve representing the boundary within which all or most of the known data points are contained

Enveloping Curve

Smooth curve representing the boundary within which all or most of the known data points are contained

Ephemeral Stream

Stream which flows only in direct response to precipitation or the flow of an intermittent spring

Estuary

Generally broad portion of a stream near its outlet

Evaporation

Emission of water vapour by a free surface at a temperature below the boiling point
Amount of water evaporated

Evaporimeter

Instrument for measuring the amount of water evaporated into the atmosphere during a given time interval

Evapotranspiration

Quantity of water transferred from the soil to the atmosphere by evaporation and plant transpiration

Expected Value

Best approximation of the true value
Usually the mean of several or many computations, estimates, or measurements

Experimental Basin

Basin where natural conditions are deliberately modified to study the effects of these modifications on the hydrological cycle

Experimental Watershed

Synonymous with experimental basin

Extreme Rainfall

Statistical (physical) upper limit of precipitation for a given duration over a particular basin

Extreme Value Distribution

Probability distribution of the largest (smallest) observation in a sample
Common distributions: FrŽchet, Gumbel and Weibull

Extreme Value Series

Hydrological series including the largest or smallest values, with each value selected from an equal time interval in the record

Rate of Flow

Volume of water flowing through a river (or channel) cross-section in unit time

Rating Curve

Curve showing the relation between stage and discharge of a stream at a hydrometic station
If digitized, it is a rating table

Rational Method

Formula estimating the peak rate of storm runoff
Product of the catchment area, a peak rate of rainfall, and a runoff coefficient

Recession

Period of decreasing discharge, as indicated by the falling limb of a hydrograph starting from the peak

Recording Rain Gauge

Instrument recording the depth of water from precipitation over time

Recurrence Interval

Long-term average interval of time or number of years within which an event will be equalled or exceeded (e.g. flood peak discharge)

Regional Analysis

Extension of the results of the analysis of point data to a region

Regression Coefficient

Coefficient of an independent variate in a regression equation
For a first degree linear regression, the slope of the regression line

Regression Curve

Diagrammatic exposition of a regression equation, generally referring to a linear regression
Synonymous with regression line

Remote Sensing

Measurement or acquisition of information on some property of an object or phenomenon by a recording device that is not in physical contact with the object under study

Representative Basin

Basin permitting the study of the hydrological cycle in a characteristic natural region by the simultaneous observation of climatic and hydrometric data
Basin where intensive hydrological studies are conducted under relatively unchanged conditions
Basin in which hydrological stations are installed to obtain measurements representing a broad area

Reservoir Routing

Technique used to compute the movement and change of shape of a flood wave moving through a river reach or a reservoir

Response Function

Mathematical representation of the behaviour of a (hydrological) system due to a specified input

Simulation

Reproduction or representation of an event or sequence of related events in a model

Skewness

Asymmetry in a frequency or probability distribution

Spillway Design Flood

Flood used for the design of a dam spillway
Maximum flood flow that could be passed without damage or serious threat to the stability of engineering structures

Staff Gauge

Graduated scale used to indicate the level of the water surface in a stream channel, reservoir, lake, etc.

Stage

Vertical distance of the water surface of a stream, lake, reservoir (or groundwater observation well) relative to a gauge datum

Stage Gauge

Graduated scale used to indicate the level of the water surface in a stream channel, reservoir, lake, etc.

Stage Hydrograph

Graph showing the variation in time of some hydrological data (stage, discharge, velocity, sediment load, etc.)
Hydrograph is mostly used for stage or discharge

Stage-Discharge Relation

Relation between stage and discharge at a river cross-section
May be expressed as a curve, table, or equation(s)

Standard Deviation

Widely used measure of dispersion of a frequency distribution or of a set of values
Positive square root of the variance

Standard Error

Positive square root of the variance of the sampling distribution of a statistic

Standard Error of Estimate

Expression for the standard deviation of the observed values about a regression line
An estimate of the variation likely to be encountered in making predictions from the regression equation

Standard Project Flood

Discharge that may be expected from the most severe combination of meteorological and hydrological conditions considered reasonably characteristic of the geographical region involved
Excludes extremely rare combinations

Standardized Variate

Value of a variate reduced to standardized form (zero mean, unit variance) by subtracting the population or sample mean and then dividing by the population or sample standard deviation.

Stationary Process

A stochastic process whose probability distribution is completely independent of time
Also referred to as stationary in the wide sense (or to the second order) if the mean and variance are independent of time

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Description

This quiz covers key concepts in environmental measurement techniques, including standardized observation methods, discharge measurement using the Moving Boat Method, and calculations of multi-annual means and storage. Additionally, it explores the relationship between multiple variables through correlation and regression. Test your understanding of these essential environmental monitoring tools!