Surface Water Protection

eMaps | ADEQ NWPR Screening Toolkit

ADEQ eMaps displaying flow regime information are just a few of the tools in the ADEQ NWPR Screening toolkit to help ADEQ and stakeholders in assessing which waters may be jurisdictional under the Clean Water Act. Other available data, information, and analysis may be necessary to make final jurisdictional determinations related to a WOTUS.

There are three categories of flow regimes that can be assigned for Arizona waters:

  • Perennial | Surface water flowing continuously year-round
  • Intermittent | Surface water flowing continuously during certain times of the year and more than in direct response to precipitation
  • Ephemeral | Surface water flowing or pooling only in direct response to precipitation

ADEQ utilizes eMaps to display the known flow regimes for perennial, intermittent and ephemeral waters on the layer listed as Flow Regimes - Perennial Intermittent and Ephemeral Streams | View >

Flow regimes are assigned to either the entire length of the surface water or to a portion of the surface water. Some surface waters are divided into sections, also known as reaches.1 Each reach receives a Waterbody Identification Number (WBID). The WBID is then assigned a flow regime. As of November 2020, about 20 percent of surface waters in Arizona have an assigned flow regime.

ADEQ developed an algorithm that can be applied to a Geographic Information System (GIS) to analyze available credible flow related data and observations for a WBID to assign a flow regime. This algorithm applies:

  • Types of observation data where measured flow data (e.g. USGS stream gauges) and on-the-ground observations (e.g. wet-dry mapping, site visits and flow measurements by staff) receive greater weight for scoring over other indirect data (e.g. satellite imagery review, modeling)
  • Scope or extent, where data that indicate a flow regime along the entire segment receives a greater weight than for data that are related to a partial segment or point on the segment.

How GIS algorithm works | Learn More >

A WBID with insufficient data to determine the flow regime is assigned ‘Undetermined’. If there is no data for the WBID, it is assigned “null”. The eMap layer that displays this information is listed as Flow Regimes - Undetermined or NULL | View >

The eMaps also indicate where a water has been designated a Traditionally Navigable Water (TNW) by the U.S. Army Corps of Engineers (Corps).2 The eMap layer that displays TNWs in Arizona is listed as Traditionally Navigable Waters | View >

The flow regimes are updated monthly as new data is continuously gathered across the state, ADEQ becomes aware of and incorporates new sources of credible data, or additional tools are applied in assigning flow regime | Subscribe for Updates >

The flow regime information is also applied in a Screening Toolkit used by ADEQ to help the agency and permittees determine jurisdictional waters under the Clean Water Act | More Information >

Submit additional or new sources of data or provide input regarding flow regimes | Email >

To request the ADEQ GIS files for flow regime eMaps, including the data analyzed to assign flow regime, fill out an online request form through the ADEQ Records Center | Online Records Request Form >

Monthly Updates

ADEQ updates the eMap layer monthly. Updates will be listed below for the current month and previous two months.

October 2021

  • San Pedro River (AZ15050202-001): Intermittent
  • Gila River (AZ15070201-006): Intermittent

September 2021

  • No updates made

August 2021

  • No updates made