USDA-ARS: USDA HWQ2: Discharge and Water Quality Data Collection on Small Watersheds
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Official Method Name
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Practical Guidance for Discharge and Water Quality Data Collection on Small Watersheds |
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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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Sampling/Preparation |
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Method Source
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Citation
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Brief Method Summary
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The objective of this manuscript is to present practical guidance for collection of discharge and water quality constituent data at the field and small watershed scale. The guidelines included are meant to increase the likelihood of project success, specifically accurate characterization of water quality within project resource constraints. Although many considerations are involved in establishing a successful sampling project, the following recommendations are generally applicable to field and small watershed studies: (1) consider wet-weather access, travel time, equipment costs, and sample collection method in the selection of sampling site numbers and locations; (2) commit adequate resources for equipment maintenance and repair; (3) assemble a well-trained, on-call field staff able to make frequent site visits; (4) establish reliable stage-discharge relationships for accurate discharge measurement; (5) use periodic manual grab sample collection with adequate frequency to characterize baseflow water quality; (6) use flow-interval or time-interval storm sampling with adequate frequency to characterize storm water quality; and (7) use composite sampling to manage sample numbers without substantial increases in uncertainty. |
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Scope and Application
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This manuscript provides guidance for collection of discharge and water quality constituent data at the field and small watershed scale and establishes a practical, scientific basis for sampling project design. Methods for both discharge and water quality are described because of the direct linkage between flow and constituent transport. The well-established methods of discharge measurement and manual water quality sampling are described only briefly because comprehensive guidance is readily available from other sources. In contrast, practical guidance on allocation of data collection resources and on the advantages and disadvantages of automated and alternative sampling procedures is not currently available. These topics are discussed in detail and presented in the context of achieving accurate characterization of water quality within project resource constraints. |
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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 influence of changing scale is discussed with this method, but in general, its application at larger scales can introduce substantial uncertainty. |
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Quality Control Requirements
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This method presents advantages/disadvantages for many data collection alternatives. A detailed description for these methods is beyond the scope of this manuscipt; however, each of the alternative methods has a recommended protocol that should followed to limit the uncertainty of collected data. |
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Sample Handling
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Maximum Holding Time
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Relative Cost
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Greater than $400 |
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Sample Preparation Methods
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