USDA-ARS: USDA HWQ1: Cumulative Uncertainty in Discharge and Water Quality Data
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Official Method Name
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Determination of Uncertainty in Measured Streamflow and Water Quality Data |
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Current Revision
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Media
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WATER |
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Instrumentation
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Not Applicable |
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Method Subcategory
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Physical |
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Method Source
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Citation
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Brief Method Summary
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This method establishes a procedure to determine the cumulative probable uncertainty in measured discharge and water quality data. Within this method, the root mean square error propagation calculation is used to determine a realistic estimate of uncertainty. The sources of uncertainty analyzed and included were divided into four procedural categories (streamflow measurement, sample collection, sample preservation/storage, and laboratory analysis). It is by individual steps within these procedural categories that uncertainty is introduced into measured discharge and constituent concentration and load data. |
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Scope and Application
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To illustrate this method and provide introductory scientific estimates of uncertainty in measured discharge and water quality data, three "data quality" scenarios (best case, typical, worst case) were examined. To assist in susequent application of this method in the absence of project-specific data, selected published uncertainty data were presented in tabular form. |
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Applicable Concentration Range
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Interferences
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The influence of scale on constituent transport is well known, but categorization of various watershed scales is difficult due to the variable nature of watershed sizes, which are determined by hydroclimatic setting and the arbitrary selection of watershed outlet locations. However, with this variability in mind, the methods discussed are generally applicable for field scale (<50 ha) to small watershed scale (<10,000 ha) data collection. The uncertainty related to data collection at larger scales is not discussed. |
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Quality Control Requirements
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Sample Handling
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Maximum Holding Time
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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