These are areas of special importance due to their ecological, aesthetic, and economic value to Arizona. If an impaired waterway is present in one of these areas, it will receive higher priority.

The information used for "Wilderness Areas" is a statewide data set that includes lands associated with the Bureau of Land Management, U.S. Forest Service, National Park Service, Fish & Wildlife Riparian Natural Conservation areas, Wilderness Study Areas, and Wilderness or Primitive areas. Wild and scenic rivers apply to the Verde River (15060203-021) and Fossil Creek (15060203-024). Note: Only Fossil Creek is impaired so it will be the only one impaired. OAW is based on Arizona Administrative Code R18-11-112.

• Type: Categorical (N, Y)
• Response: Wilderness/Oustanding Arizona Waters = Higher Index
• Source: Water Quality Database and National Wild and Scenic Rivers System Website | View >

Impaired waterways that fall within areas with higher percent low income and/or higher percent minority populations will receive higher priority.

The percentages of low-income and percentages of minority were extracted from EPA’s recovery potential tool for each of Arizona’s 12-digit HUCs and associated with WBIDs. Weighted averages using stream miles or lake acres were determined because one WBID could cross multiple 12-digit HUCs. The ‘EJ’ score was calculated by averaging the weighted averages for the percent low-income and percent minority.

• Type: Continuous. Unit = Percent
• Response: Higher ‘EJ’ = Higher Index
• Source: EPA Recovery Potential Screening (RPS) Tools | View > 

Higher priority is given to waterways that can have a direct impact on public health. This could be a waterway that is a drinking water supply or is often used for recreation. Lower priority will be given to waterways that are typically dry for most of the year and have a lower risk of directly impacting public health.

Priority uses include domestic water source (DWS) and full body contact (FBC). Uses that are ephemeral (AWE and PBC) are given lower priority.

• Type: Categorical (Ephemeral, Human Priority, Not). Not means that the use is not a human priority or ephemeral water.
• Response: Human Priority = Higher Index
• Source: Water Quality Database 

The longer a waterbody is known to be impaired, the higher the priority will be for that water.

The years impaired comes from the historic impairment spreadsheet and is the current year minus the assessment cycle a waterbody was listed.

• Type: Continuous. Unit = Years.
• Response: Higher Years Impaired = Higher Index
• Source: ADEQ Historic Impairments list

If an impaired waterbody segment falls within a smaller watershed area, that water will receive higher priority, as it is often easier to control and address pollution in a smaller area than a larger one.

Gathered from the Water Quality Database. Note that some watershed area are not present and need to be manually entered into ZWATERSHEDAREA. This metric was log transformed because of extremely high and low values.

• Type: Continuous. Unit = Square Miles.
• Response: Smaller Watershed = Higher Index
• Source: Water Quality Database

When the agency becomes aware of a pollutant source that needs to be controlled to improve water quality, that area will receive a higher priority for project development.

Known ongoing unauthorized impacts (KOUIs) are priority waters that ADEQ is working to remediate to protect human health and the environment.

• Type: Categorical (None, [KOUI] where KOUI defines specific KOUI)
• Response: KOUI = Higher Index
• Source: ADEQ List of KOUIs Related to Surface Water Protection and Improvement

If an impaired waterbody segment has only a single pollutant causing water quality issues, that water will receive a higher priority than waters that are polluted by multiple pollutants. This is because it is easier to control and address pollution of a single pollutant than it is for many pollutants.

Waterbodies can be impaired for multiple parameters.

• Type: Continuous. Unit = Count of Impaired Parameters.
• Response: Smaller # of Impairments = Higher Index
• Source: The Assessment Calculator 

Certain water pollutants in Arizona have a history of being more effectively cleaned up than others. Waters with pollutants that have a higher rate for successful improvement will receive a higher priority, as those waters can be more easily returned to a healthy state in a shorter period of time.

Which parameters are more likely to be delisted?

• Type: Continuous. Unit = Number of Delists for that Parameter.
• Response: Higher # of Delists = Higher Index
• Source: ADEQ Historic Impairments List

If a waterbody is impaired and has a pollutant discharger (such as a wastewater treatment plant) within 1 mile of the impaired area, that area will receive a higher priority. 

Permits within 1 mile of an impaired water? Focus on individual facilities in accordance with the TMDL Prioritization Rule.

• Type: Categorical (Yes, None)
• Response: Permit = Higher Index
• Source: Arizona Individual Permits for Discharging to Surface Waters | View > 

If a waterbody is “very polluted” versus only “slightly polluted”, the waterbody with less pollution will receive higher priority, as slightly polluted water can be easier and less costly to clean.

How far above the water quality standard is the result? The restoration potential tool looks at all data and determines the median result vs. the median standard. This metric was log-transformed to account for skewed data.

• Type: Continuous. Unit = None. Ratio of median result: median standard.
• Response: Lower Magnitude = Higher Index
• Source: ADEQ Restoration Potential Tool

If a waterbody is frequently identified as polluted, that waterbody will receive a lower priority to a waterbody that is only rarely shown as polluted, as slightly polluted water can be easier and less costly to clean.

From the restoration potential tool. Calculated by looking at the total number of exceedances vs. the total number of samples for the full period of record.

• Type: Continuous. Unit = Percent of Samples Exceeding Standard
• Response: Lower Exceedance Rate = Higher Index
• Source: ADEQ Restoration Potential Tool 

Sometimes a waterbody is identified as polluted, but then we are not able to return to the location for many years. If a waterbody is identified as polluted, and we have more current data to show that it is still polluted, that waterbody will receive a higher priority.

Does current data confirm that the impairment is still impaired?

• Type: Categorical (Yes, No)
• Response: Yes Confirmed = Higher Index
• Source: ADEQ Restoration Potential Tool