The Town of Patagonia Flood and Flow Committee and the Friends of Sonoita Creek (FOSC) hosted an event on Jan. 22 focusing on the conclusion of their water quality study, conducted by the Nextgen Engineering firm, based in Tucson. The report, to be released to the public in March 2020, gathered data regarding the watershed to create a baseline for water quality, critical for monitoring the health of a watershed. Nextgen Engineering studied all available reliable data on both groundwater and surface water spatially and over time. 

There has been continual presence by humans in Santa Cruz County for 12,000 years. The town of Patagonia is located within the Sonoita Creek Watershed, which is also used by ranchers, fishermen, miners and the US Forest Service. It is a wildlife corridor, because of its riparian habitat and elevation, and a tourist attraction. Along with historic ranching there has also been poor land management. All these are sources of stress for the watershed. 

In the last century, the north and south sections of the watershed have had a lot of mining activity, but there is little data from the north and eastern parts of the watershed. Currently the southern part of the watershed, that is regularly sampled by Arizona Department of Environmental Quality (ADEQ), shows that there are parts of the watershed that are impaired and have chronic or acute exceedances of pollutants as defined by the ADEQ. 

Exceedances is the term used by ADEQ when pollutants in a sample exceed the limit safe for humans. Some samples get categorized under exceedances because of a one-time measurement (acute) while others are measured over time (chronic). Other sections of the watershed are not impaired but have had chronic or acute exceedances in their samples and are categorized as “non-attaining.” There are sections of the watershed that are unimpaired. A majority of the watershed is not currently sampled or monitored by the ADEQ. 

“With the geology of this area it is not surprising to see metals in the watershed”, said Bill O’Brien, head engineer for NextGen. However, exceedances of certain metals in the historical data can be assumed to be due to mining activity, said NextGen consultant Bruce Kirkpatrick. 

It is important to consider the impact of acidity. Acidity in the surface water makes it uninhabitable for aquatic life, affecting the southern part of the watershed and specifically Adam Gulch. The groundwater in this area is naturally “hard” caused by Calcium Bicorbonate (CACO3). CACO3 affects plumbing infrastructure, plants, “may add a salty flavor to the water,” and affects the way erosion occurs, bringing naturally occurring elements into the watershed. 

Despite the exceedances in nearby streams, the study shows that the “Town of Patagonia municipal well samples have been tested for 89 different contaminants, with zero samples exceeding health standards.”

The gaps in the current data reveal that testing for groundwater is concentrated in the middle of the watershed and there is very little information about the north and south sections. There are almost no samples from springs throughout the watershed. For surface water, the data is concentrated in the southern part of the watershed.

The number of samples have also dramatically reduced in the last decade, though there is no conclusive answer to why that is the case. Nextgen suggested that we need citizen scientists to gather data for the areas of the watershed that have never been sampled and continue to sample more where there is existing data. 

The presentation concluded with recommendations that a watershed committee or council be formed to develop long-term thinking around the health and management of the watershed. 

Currently the Sonoita Creek watershed is not under active management by the state. When a watershed is designated as an active management area (AMA) it sets in motion a set of policies to protect the watershed. AMA areas in Arizona include the Santa Cruz River, which is the water source for Tucson. 

O’Brien said that the stakeholders should not wait for Phoenix to make the Sonoita Creek Watershed an AMA and to take action now to begin the process to secure protection and funding from the state.