Skip to content

Learn WaterML 2 / WaterML 2 Syntax

WaterML 2 XML syntax conforms to the WaterML 2.0 schema, which defines the names of elements and attributes, indicates whether elements are required/optional, and whether multiple elements are allowed. Because the WaterML 2.0 schema relies on other schemas that have been designed over time and by multiple entities, there is inconsistency in naming conventions (case, plural, etc.).

This page contains the following sections, which walk through important schema elements and provides context relevant to typical time series data handling. The WaterML 2.0 - Getting Started documentation is also helpful to understand the hierarchy of elements.

Root Element

XML files are a hierarchy and require as single root element as the entry point. The root element for WaterML 2.0 according to the standard is Collection. However, different implementations may provide additional data, such as the USGS, which wraps the Collection element with FeatureCollection, as discussed below.

Collection (Standard)

The WaterML 2.0 standard uses Colletion as the root element, for example (this example was created by slightly rearranging data from the USGS NWIS example in the next section). Note that the first element contains information such as the schemas used in the file.

<wml2:Collection gml:id="C.USGS.09071750" xsi:schemaLocation="http://www.opengis.net/waterml/2.0 http://schemas.opengis.net/waterml/2.0/waterml2.xsd" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:wml2="http://www.opengis.net/waterml/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:om="http://www.opengis.net/om/2.0" xmlns:sa="http://www.opengis.net/sampling/2.0" xmlns:sams="http://www.opengis.net/samplingSpatial/2.0" xmlns:swe="http://www.opengis.net/swe/2.0">
      <gml:identifier codeSpace="http://waterservices.usgs.gov/nwis/dv">USGS.09071750</gml:identifier>
      <gml:name codeSpace="http://waterservices.usgs.gov/nwis/dv">Timeseries collected at COLORADO RIVER ABOVE GLENWOOD SPRINGS, CO</gml:name>
      <wml2:metadata>
        <wml2:DocumentMetadata gml:id="doc.USGS.MP.USGS.09071750">
          <gml:metaDataProperty about="contact" xlink:href="http://waterservices.usgs.gov"/>
          <wml2:generationDate>2017-06-29T04:34:37.787-04:00</wml2:generationDate>
          <wml2:version xlink:href="http://www.opengis.net/waterml/2.0" xlink:title="WaterML 2.0"/>
        </wml2:DocumentMetadata>
      </wml2:metadata>
      <wml2:observationMember>

FeatureCollection (USGS)

USGS NWIS web services use FeatureCollection as the root element, for example:

<gml:FeatureCollection gml:id="USGS.waterservices" xsi:schemaLocation="http://www.opengis.net/waterml/2.0 http://schemas.opengis.net/waterml/2.0/waterml2.xsd" xmlns:gml="http://www.opengis.net/gml/3.2" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:wml2="http://www.opengis.net/waterml/2.0" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:om="http://www.opengis.net/om/2.0" xmlns:sa="http://www.opengis.net/sampling/2.0" xmlns:sams="http://www.opengis.net/samplingSpatial/2.0" xmlns:swe="http://www.opengis.net/swe/2.0">
  <gml:featureMember>
    <wml2:Collection gml:id="C.USGS.09070500">
      <gml:identifier codeSpace="http://waterservices.usgs.gov/nwis/dv">USGS.09070500</gml:identifier>
      <gml:name codeSpace="http://waterservices.usgs.gov/nwis/dv">Timeseries collected at COLORADO RIVER NEAR DOTSERO, CO</gml:name>

Note that the FeatureCollection provides minimal additional data in this example. Once the Collection element is encountered, the remainder of the elements follow the WaterML 2.0 standard.

More Data

TODO smalers 2017-07-15 need to transfer content from the "WaterML 2.0 Open Data Implementation Guidance Project".`