Hydrology Terminology Quiz

Hydrology Terminology

• Accumulative Precipitation Gauge: Used for measuring precipitation in locations only visited periodically.
• Active Basin Area: The area of a basin excluding any portions that don't drain into it.
• Actual Evaporation: The quantity of water vaporizing from an open water surface or the ground.
• Actual Evapotranspiration: The combined amount of water evaporated from soil and transpired by plants in natural conditions.
• Advection: The horizontal transfer of air mass properties due to wind.
• Altitude: Vertical distance measured from mean sea level to a point, object, or level.
• Annual Exceedence Series: A series of values representing independent events like floods, occurring above a chosen base value. The count of values equals the number of years in the record.
• Annual Flood:
  • (1) The highest peak discharge in a single water year.
  • (2) A flood that happens, on average, once per year.
• Annual Flow: The total volume of water flowing in a year, usually referring to a drainage area or river basin's output.
• Annual Maximum Series: An extreme values series containing the highest annual values.
• Annual Minimum Series: An extreme values series containing the lowest annual values.
• Annual Runoff: The total volume of water flowing in a year, commonly referring to the outflow from a drainage area or river basin.
• Annual Series: A hydrological series where each term represents a specific characteristic or element for a given year.
• Annual Storage: The volume of water that can be held in a reservoir to adjust for seasonal variations in inflow and demand.
• Annual Storage Capacity: The maximum volume of water that can be stored in a reservoir to manage seasonal variations in inflow and demand.
• Antecedent Precipitation Index (API): A weighted sum of past daily rainfall amounts used to estimate soil moisture.
• Coefficient of Variation: A dimensionless statistical parameter representing the variability of a stochastic variable in time or space. Calculated as the ratio of the standard deviation to the mean.
• Compound Weir: A weir composed of two or more sections that might be of different types and/or dimensions.
• Conceptual Hydrological Model: A simplified mathematical representation of some or all processes within the hydrological cycle. It uses hydrological concepts expressed mathematically and linked in a time and space sequence that mimics natural processes.
• Conditional Probability: The probability of an event (E) happening given the occurrence of another event (F).
• Confidence Interval: An interval that includes the true value with a specific probability, determined by the statistics of the sample.
• Confidence Level: The probability that a confidence interval contains the true value.
• Confidence Limits: The upper and lower boundaries of a confidence interval.
• Constant-Rate Dilution Gauging: A procedure to determine flow characteristics such as velocity or discharge. A known concentration of tracer is injected at a constant rate, and the tracer's concentration is measured downstream when good mixing occurs.
• Continental Hydrology: The study of hydrological processes in continental areas, focusing on the land-based portion of the water cycle.
• Continuity Equation: An equation describing the conservation of mass in a flowing substance like water.
• Convective Precipitation: Precipitation stemming from convective motions in the atmosphere.
• Correlation: An interdependence or relationship between two measurable variables.
• Correlation Coefficient: A measure of the interdependence between two variables. The product-moment correlation coefficient is the covariance divided by the product of their standard deviations.
• Crest Gauge (Crest Gage): A device measuring the maximum water level reached.
• Cumulative Precipitation Gauge: A precipitation gauge employed at stations visited at infrequent intervals.
• Cup-Type Current Meter: A current meter with a rotating wheel fitted with cups that spins on a vertical axis.
• Current Meter: An instrument used to measure the velocity of water at a specific point.
• Median: The value that divides a continuous frequency distribution into two halves with equal frequency. For discrete data, it's the middle value in a ranked dataset when the number of data points is odd, or the average of the two central values if the number is even.
• Medium-Term (Extended) Hydrological Forecast: A forecast of a water body's future regime for a period between 2 and 10 days from the time of issuance.
• Meteorological (Weather) Radar: A system using beamed, repeated, and timed electromagnetic radiation to detect, locate, quantify, and measure the altitude of objects, as well as generating terrain images.
• Meteorology: The study of the atmosphere.

Minimum Annual Discharge/Flow

• Minimum Annual Discharge: Lowest discharge value in a stream during a hydrological year.
• Minimum Annual Flow: Lowest discharge value in a stream during a hydrological year.
• Mode: The variate that occurs most frequently in a distribution of a discrete variate. For a continuous variate, it represents the variate with the maximum probability density.
• Model: A representation of an object, process, or system in any form. In hydrology, a model is commonly a mathematical representation of a basin, water system, or a set of data.

Model Calibration and Fitting

• Model Calibration (Model Fitting): The process of adjusting a model's parameters, either based on physical considerations or mathematical optimization, to ensure the best possible agreement between observed data and the model's estimated output.
• Moment: A statistical measure representing the mean value of a variable raised to a power. It can be calculated about the origin or around a fixed value. When taken around the mean, they are called central moments.
• Monitoring (Pumping Test): The process involves pumping water out of a well at specific rates while regularly measuring piezometric levels at the pumped well and nearby observation wells. Data collected from these tests helps determine aquifer parameters around the pumped well.
• Quantile: A class of partition values of a variate that divide the total frequency of a population or sample into a given number of equal proportions. Examples include quartiles (n = 4), deciles (n = 10), etc.
• Quantitative Precipitation Forecast (QPF): A prediction of the amount of precipitation.
• Radar (-Rainfall) Equation: An equation defining the maximum range achievable by a specific radar system in terms of its design parameters and the effective target echo area.
• Rain: Liquid water precipitation, either in drops larger than 0.5 mm in diameter or smaller, dispersed drops.
• Rain Gauge (Rain Gage): An instrument to measure rainfall depth at a point.
• Rain Recorder: An instrument that measures and records rainfall depth over time.
• Rain Shadow: An area located on the leeward side of a mountain or range with significantly less rainfall than the windward side.
• Rainfall (Depth): The amount of liquid water falling from the atmosphere, expressed as a depth of water on a horizontal surface.
• Rainfall Distribution: The spatial and temporal variation of rainfall depth.
• Rainfall Excess: The portion of rainfall directly contributing to surface runoff.
• Rainfall Intensity: The rate of rainfall, expressed in units of depth per unit time.
• Rainfall Intensity Pattern: The distribution of rainfall rate over time during a storm.
• Rainfall Intensity Return Period: The average time interval (in years) between occurrences of rainfall of a specified intensity and the next rainfall of equal or greater intensity.
• Rainfall Maximization: A procedure used to determine probable maximum precipitation.
• Rain-Gauge Shield (Rain-Gage Shield): A device that protects a rain gauge from wind, snow, or other factors that could affect measurements.
• Random Error: The deviation between a computed, estimated, or measured value and the true value. The deviation behaves randomly, like a variable chosen from a probability distribution of such errors.
• Random Process: A stochastic process often referred to as a "stochastic process."

Simulation and Skewness

• Simulation: The reproduction or representation of an event or a sequence of related events in a model, for example, of a water resource system.
• Skewness: Asymmetry in a frequency or probability distribution.
• Spillway Design Flood:
  • (1) The flood used in the design calculations for a dam's spillway.
  • (2) The maximum flood flow that can be passed without causing damage or a significant risk to the stability of the engineering structure.
• Staff Gauge (Staff Gage): A graduated scale used for measuring water surface levels in a stream channel, reservoir, lake, etc.
• Stage: The vertical distance from a gauge datum to the water surface of a stream, lake, or reservoir (or groundwater observation well).
• Stage Gauge (Stage Gage): A graduated scale used for measuring water surface levels in a stream channel, reservoir, lake, etc.
• Stage Hydrograph: A graph depicting the temporal variation of hydrological data like stage, discharge, velocity, or sediment load.

Stage-Discharge Relation

• Stage-Discharge Relation: The relationship between stage and discharge at a river cross-section. It's represented as a curve, table, or equation(s).
• Standard Deviation: A commonly used measure of dispersion in a frequency distribution or a set of values. It's equal to the positive square root of the variance.
• Standard Error: The positive square root of the variance of a statistic's sampling distribution.
• Standard Error of Estimate: An expression for the standard deviation of observed values around a regression line. It estimates the likely variation in predictions based on a regression equation.
• Standard Project Flood: The discharge expected from the most severe combination of meteorological and hydrological conditions reasonably characteristic of the geographic region, excluding extremely rare combinations.
• Standardized Variate: A variable transformed into a standardized form with a mean of zero and a standard deviation of one by subtracting the population or sample mean and dividing by the population or sample standard deviation.
• Stationary Process: A stochastic process whose probability distribution is completely independent of time. It's stationary in the wide sense if its mean and variance are constant over time. The statistics of samples from a stationary process may vary due to sampling variability but not due to sample size or location within the population.