Comments Submitted

February 6, 2022


U.S. Army Corps of Engineers (“Corps”)
U.S. Environmental Protection Agency (“EPA”)


Comments submitted to Docket ID No. EPA-HQ-OW-2021-0602 via the designated web portal Revised Definition of Waters of the United States (“WOTUS”)

These comments are submitted on behalf of the Lower San Pedro Watershed Alliance (hereinafter the “Alliance”), which is an all-volunteer landowner-based charitable conservation organization located in the last remaining natural and intact desert river ecosystem in southern Arizona. Our comments are based on first-hand observations and empirical data compiled in this rural desert watershed, and on the Clean Water Act’s stated purpose “to restore and maintain the chemical, physical, and biological integrity of the Nation's waters.”.

As the last remaining natural desert river in the region and as part of a large wildlife habitat zone that has not been significantly degraded by elements of urban and suburban landscape fragmentation, the San Pedro watershed has become the default repository for off-site mitigation of impacts caused by development that has taken place elsewhere in the state, including impacts caused by:

  • the Salt River Project, in expanding the water supply for the Phoenix area,

  • the Bureau of Reclamation, during the construction of the Central Arizona Project,

  • the land exchange that led to the sale of State lands for development and the associated establishment of the San Pedro Riparian National Conservation Area,

  • mining projects and initiatives,

  • development in the Tucson region, resulting in mitigation associated with Pima County’s federal Multi-Species Conservation Plan,

  • loss of threatened and endangered species in developed areas of Arizona, leading to critical habitat designations by the U.S. Fish & Wildlife Service in the San Pedro watershed, and

  • loss of water resources needed to support critical habitat, leading to non-governmental groups retiring groundwater withdrawals on purchased agricultural lands in the San Pedro watershed.

With this important federal mitigation role taking place in our local rural desert watershed, our comments are not what is typically considered by urban and suburban dwellers who often dominate conversations about the Clean Water Act in the halls of Congress and in the federal court system. However, if federal mitigation designations are to have any value at all in fulfilling their legal mandate to be perpetual (to effectively compensate for permanently damaging impacts), these comments must be considered seriously by the two federal oversight agencies that drafted the new WOTUS rule.

Our major comment is the following: It should be stated explicitly in the new rule under the significant nexus standard that an ephemeral tributary, either individually or in combination with similarly situated tributaries, must be included in WOTUS if this tributary or regional group of tributaries affect the chemical, physical, or biological integrity of downstream waters.

The application of the significant nexus standard to ephemeral streams will vary according to the climate, geology, groundcover, and nature of each major waterway that is fed by such tributaries in each region. In this state, the Arizona Department of Environmental Quality (“ADEQ”) plans to eliminate all ephemeral waterways from their definition of Waters of the State. Similar to the unscientific rationale of politically-minded individuals and interest groups, the state has adopted the simplistic thinking that they should only protect waterways that are “wet” for most of the year, ignoring the principles of desert hydrology where rain events can be either feast or famine.

Sediment loads in ephemeral waterways are increasing significantly during rain events due to drought, overgrazing, and wildfires. These erosion-producing conditions are expected to get worse due to climate change. ADEQ has no program to regularly monitor sediment loads during flows along the lower San Pedro River. It is common for landowners along the river to observe and measure extremely high suspended sediment loads during significant regional rain events. How can the ADEQ conclude that ephemeral tributaries pose no significant nexus to water quality in the San Pedro River if they make no effort to monitor these loads? Due to over-politicizing water policy in Arizona, it is essential that the Corps and the EPA include language in their new WOTUS definition that recognizes the enormous impact that unregulated ephemeral tributaries can have on water quality in the arid Southwest.

Sediment loads carried by major desert rivers have enormous impacts. Landowning members of the Alliance have observed sediment deposits in the floodplain of the San Pedro River that average up to four feet in depth during a single rainy season. Landowners in Aravaipa Canyon have observed suspended clay loads that sealed off portions of Aravaipa Creek from groundwater infiltration. Clay deposits are especially conducive to the growth of invasive tamarisk in our watershed, which is already causing intense wildfires along the riparian corridors. With extreme sediment loads significantly reducing water quality, reducing groundwater recharge, and transforming the San Pedro River from a wildfire barrier to a source of the hottest burning wildfires in the state, the impacts of excessive sediment deposition cannot be ignored.

In a natural river ecosystem like the San Pedro River, there is no practical option for removing massive amounts of deposited sediments. Unlike the urban and suburban portions of the Santa Cruz, Salt, and Gila Rivers where sediments can routinely be removed by County flood district personnel from river channels that have been engineered with banks of soil cement, the rural San Pedro River can only be protected from the impacts of high sediment loads through proactive and preventative measures. By abandoning regulation of major ephemeral tributaries to the San Pedro River, ADEQ has given up on such measures, choosing instead to only be accountable to urban and suburban political constituencies.

It is essential that the Corps and the EPA do not follow suit. The EPA’s own studies confirm major ephemeral waterways are in fact important contributors to the water quality of the San Pedro River. Our major ephemeral tributaries must not be subjected to the cumulative impacts of unregulated construction involving dredge-and-fill operations, deposits from mining operations, waste from feedlot operations, and sediment deposition caused by other commercial operations.

Please include explicit language in the new rule stating that ephemeral tributaries must be included in the definition of WOTUS if their inclusion meets the significant nexus standard of confirming effects on the chemical, physical, or biological integrity of downstream waters.

Respectfully submitted by the Lower San Pedro Watershed Alliance,

Peter Else, chair

P.O. Box 544, Mammoth, AZ 85618

View of PDF of these comments here.