Tips on accessing sediment data

Sediment data are collected on rivers and streams throughout the nation. These data can be accessed through the USGS Samples endpoints.

USGS collects bedload sediment and suspended sediment data at thousands of monitoring locations across the country. These data are useful in understanding water quality conditions and sediment transport in rivers, lakes, and reservoirs throughout the country. We’ve heard from users that it is sometimes hard to find sediment data and fully understand the results presented. We’ve compiled some tips and suggestions to help users find the full amount of sediment data available and understand how these data are collected.

Where to Find Sediment Data

On the web

Sediment sample data are available through the Download Samples feature on WDFN. The Download Samples form allows users to access discrete sample data that are derived from manual field collection and laboratory analysis. Sediment data collection often involves sampling both the sediment itself (such as bed sediment of a specific size) and sampling the water to analyze sediment suspended in the water column.

To ensure that users are accessing all available discrete sediment data for a monitoring location, users should select the Sample Media type as both Sediment and Water. This filter will allow users to see analyses conducted both on water (such as suspended sediment) and analyses on the sediment itself. If users only want to download sediment concentration and class data, they can also refine their search to only look for observed properties in the Sediment characteristic group. These data are available on the Download Samples feature, which means they are also available via the Water Quality Portal .

Using the dataretrieval packages

Users can also access discrete sediment data directly from a programming console using dataretrieval, available in R and python versions. These packages have a set of functions that pull data via the Samples web services . Below, users will find example data pulls using dataRetrieval and dataretrieval-python. In each language, the first data pull downloads results in hydrologic unit 07090002 where the medium sampled is “Sediment”. The second data pull downloads results in hydrologic unit 07090002 where the medium sampled is “Water” and it is sampled for the characteristic “Sediment”.

R

library(dataRetrieval)

# medium is Sediment, various characteristics
sediment_07090002 <- read_USGS_samples(activityMediaName = "Sediment", hydrologicUnit = "07090002")

# medium is Water, characteristic is Sediment
water_07090002 <- read_USGS_samples(activityMediaName = "Water", characteristic = "Sediment", hydrologicUnit = "07090002")

Python

from dataretrieval import samples

# medium is Sediment, various characteristics
sediment_07090002,_ = samples.get_usgs_samples(activityMediaName="Sediment", hydrologicUnit="07090002")

# medium is Water, characteristic is Sediment
water_07090002,_ = samples.get_usgs_samples(activityMediaName="Water", characteristic="Sediment", hydrologicUnit="07090002")

Please reach out to the Computational Tools team at CompTools@usgs.gov with questions about using the dataretrieval packages to download sediment data.

Method Metadata Matter

An important consideration in analyzing sediment data is methodology. This information is available as metadata in the discrete sample data downloads. For example, the method used to collect sediment data in the field can range from a cross-sectionally representative sample to a single point or grab sample, both may have different applications and describe different components of a waterbody. The metadata associated with the collection method are available in the SampleCollectionMethod_Name column; some common methods used to collect data are equal-discharge-increment, equal-width-increment , and grab samples. In addition, the Activity_TypeCode and Activity_MediaSubdivision columns provide insight as to the nature of how a sample was collected and the environmental matrix of the sample.

Another important piece of metadata is how samples were processed in the laboratory . This information is available in the ResultAnalyticalMethod_Identifier or ResultAnalyticalMethod_Name columns. More information on these methods is available in NWIS Help , NEMI , or through several publications about the specific method.

How Sediment Data are Used

It is often useful to combine discharge (streamflow or flow) data with sediment sample data to understand sediment loads. The load values represent how much sediment by volume is being transported in a river and is typically reported as tonnage per time unit. USGS scientists commonly use discharge and sediment samples in combination to calculate daily and instantaneous sediment load values. Sediment load information may help to better understand how sediment may affect reservoir storage, shipping channels, and habitat for example. Although discharge data is sometimes available through the Download Samples feature, discharge data in WDFN are more reliably found as historical observations, daily data, or field measurements in the surface water module of WDFN. Discharge and sample data are also both available via the dataRetrieval package and via USGS water services .