Australian Water Information Dictionary

Water forecasts: 7-day Streamflow Forecasts

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catchment

The land area draining to a point of interest, such as a water storage or monitoring site on a watercourse.

Related:

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catchment area

The extent of land where water from precipitation drains into the water storage.

Related: catchment

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deterministic forecast

A single valued forecast derived from a unique set of known input data and a forecast model.

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ensemble forecast

A collection or distribution of many forecasts for the same period and location. They can be generated from many models or from one model with many parameter sets.

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flow

The flow of water in streams, rivers and other channels.

Synonym: streamflow

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mean absolute error

The average of absolute values of the difference between observed and simulated values for a set of simulated data.

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median

The middle number of a given sequence of numbers. When the sequence contains an even amount of numbers, the median is the mean of the two middle values.

Source: The first part of definition sourced from Macquarie Dictionary Fifth Edition, 2009, Macquarie Dictionary Publishers.

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numerical weather prediction (NWP)

A science focused on taking current observations of weather and processing these data with computer models to forecast the future state of weather.

Source: Modified from NOAA, viewed 25 July 2015.

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percentile

One of a series of threshold values that divides a set of ordered data into 100 groups with an equal number of data points in each.

For example, consider a dataset of annual rainfall totals arranged in increasing order. The 20th percentile is a value with 20% of the data below it and 80% above it. The 90th percentile is a value with 90% of the data below it and 10% above it.

Related: quantile

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precipitation

All forms in which water falls on the land surface and open water bodies as rain, sleet, snow, hail, or drizzle.

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probabilistic forecast

A probabilistic streamflow forecast shows the range of possible streamflow values and how likely it is that they will occur.

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skill score

A statistical score used to objectively assess the performance (skill) of a model. A score can be presented absolutely or formulated as a skill score.

Skill Score =(Smod - Sref) / (Sperf - Sref)

Where

Smod = Score for the model forecast

Sref = Score for a reference forecast, usually climatology

Sperf = Score for a perfect forecast, usually 0 or 1

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stream length

Longest distance along the stream from the point of consideration to the most distant headwater source.

Source: Modified from USGS, viewed 4 September 2015.

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streamflow

The flow of water in streams, rivers and other channels.

Synonym: flow

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uncertainty

A state of lack of confidence to exactly describe the current or future condition of a system when limited knowledge of that system is available.

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