Human-Related Compounds in Water Sources in the Grand Canyon Help Identify Water Flow Pathways and Highlight Potential Water Quality Changes
Grand Canyon
Monument Springs
U.S. Geological Survey (USGS) scientists investigated the movement of human-generated chemicals, such as pharmaceuticals and per- and polyfluorinated substances (PFAS), in groundwater along the South Rim of the Grand Canyon. This research led to a better understanding of the movement of wastewater into groundwater, of complex underground flow patterns, and of chemicals present in springs near highly popular tourist areas.
Water that has been in contact with humans and chemical sources, such as cookware, adhesives, paper, and packaging, is often routed to wastewater-treatment plants where it is treated and then released back into the environment. However, man-made compounds in this water, such as pharmaceuticals and PFAS, do not occur naturally and are not fully removed in the water-treatment process. These compounds do not break down easily in the environment and have been detected in groundwater and surface waters (for example, streams, lakes, and wetlands) all over the Earth, indicating the presence of human-use compounds even in areas where people are rarely present.
Groundwater is an important resource that supports local populations and ecosystems in the primarily arid Grand Canyon region. Springs, where groundwater comes to the surface, provide an important source of water for people and wildlife throughout the region. An understanding of the sources, movement, and reappearance of groundwater also improves our understanding of the human effects on water in the Grand Canyon region and can provide information on the potential environmental effects of other activities in the area such as mining.
After being piped in from across the canyon, water used by visitors at Grand Canyon Village on the South Rim is sent to a wastewater-treatment plant. Treated wastewater is then released into the Bright Angel Wash, a drainage located on a fault, and the flow path and destination of this water as it moves into the ground was previously not well understood.
For this investigation, water samples were collected from the Bright Angel Wash and six springs along the South Rim and analyzed for nutrients, 28 different PFAS compounds, and 154 pharmaceuticals to understand the movement of wastewater after its release from the Grand Canyon Wastewater-Treatment Plant.
Results of this study provided information on the movement and presence of wastewater in groundwater and in springs around the South Rim. PFAS were detected in wastewater in the Bright Angel Wash and in two of the more remote springs sampled, and pharmaceutical compounds were detected in the wash and in one of the same spring water locations. However, no pharmaceuticals or PFAS were detected at the springs closer to visitor trails and campsites at Havasupai Gardens. Nitrate, which does occur naturally but indicates human water use when measured in high amounts, was elevated at the wash and at Monument Springs. Levels were high enough that there is a warning given by Grand Canyon National Park for back-country hikers camping at the Monument Campsite regarding elevated nitrate in Monument Creek. The presence of human-derived compounds at certain springs but not others highlights the effects of geologic structure on groundwater movement in the area. Finally, the methods demonstrated here can be used in other arid areas where treated wastewater effluent is recharged to groundwater resources to understand human effects and underground structurally controlled pathways.
The Grand Canyon is an important area that supports cultural, economic, and environmental uses. This study provides more information on the fate of treated wastewater in and around highly popular tourist areas, indicates that human-related chemicals are affecting back-country springs (Monument Spring), and clarifies our understanding of how water and chemicals move through the ground around the South Rim of the Grand Canyon. Information learned from this study can be used to better plan for environmental effects as wastewater use and other human activities increase in the area.
Funding Statement: The funding for this research was provided through the USGS Ecosystem Mission Area through the Environmental Health Program, and the USGS National Park Service Water Quality Partnership Program.
U.S. Geological Survey (USGS) scientists investigated the movement of human-generated chemicals, such as pharmaceuticals and per- and polyfluorinated substances (PFAS), in groundwater along the South Rim of the Grand Canyon. This research led to a better understanding of the movement of wastewater into groundwater, of complex underground flow patterns, and of chemicals present in springs near highly popular tourist areas.
Water that has been in contact with humans and chemical sources, such as cookware, adhesives, paper, and packaging, is often routed to wastewater-treatment plants where it is treated and then released back into the environment. However, man-made compounds in this water, such as pharmaceuticals and PFAS, do not occur naturally and are not fully removed in the water-treatment process. These compounds do not break down easily in the environment and have been detected in groundwater and surface waters (for example, streams, lakes, and wetlands) all over the Earth, indicating the presence of human-use compounds even in areas where people are rarely present.
Groundwater is an important resource that supports local populations and ecosystems in the primarily arid Grand Canyon region. Springs, where groundwater comes to the surface, provide an important source of water for people and wildlife throughout the region. An understanding of the sources, movement, and reappearance of groundwater also improves our understanding of the human effects on water in the Grand Canyon region and can provide information on the potential environmental effects of other activities in the area such as mining.
After being piped in from across the canyon, water used by visitors at Grand Canyon Village on the South Rim is sent to a wastewater-treatment plant. Treated wastewater is then released into the Bright Angel Wash, a drainage located on a fault, and the flow path and destination of this water as it moves into the ground was previously not well understood.
For this investigation, water samples were collected from the Bright Angel Wash and six springs along the South Rim and analyzed for nutrients, 28 different PFAS compounds, and 154 pharmaceuticals to understand the movement of wastewater after its release from the Grand Canyon Wastewater-Treatment Plant.
Results of this study provided information on the movement and presence of wastewater in groundwater and in springs around the South Rim. PFAS were detected in wastewater in the Bright Angel Wash and in two of the more remote springs sampled, and pharmaceutical compounds were detected in the wash and in one of the same spring water locations. However, no pharmaceuticals or PFAS were detected at the springs closer to visitor trails and campsites at Havasupai Gardens. Nitrate, which does occur naturally but indicates human water use when measured in high amounts, was elevated at the wash and at Monument Springs. Levels were high enough that there is a warning given by Grand Canyon National Park for back-country hikers camping at the Monument Campsite regarding elevated nitrate in Monument Creek. The presence of human-derived compounds at certain springs but not others highlights the effects of geologic structure on groundwater movement in the area. Finally, the methods demonstrated here can be used in other arid areas where treated wastewater effluent is recharged to groundwater resources to understand human effects and underground structurally controlled pathways.
The Grand Canyon is an important area that supports cultural, economic, and environmental uses. This study provides more information on the fate of treated wastewater in and around highly popular tourist areas, indicates that human-related chemicals are affecting back-country springs (Monument Spring), and clarifies our understanding of how water and chemicals move through the ground around the South Rim of the Grand Canyon. Information learned from this study can be used to better plan for environmental effects as wastewater use and other human activities increase in the area.
Funding Statement: The funding for this research was provided through the USGS Ecosystem Mission Area through the Environmental Health Program, and the USGS National Park Service Water Quality Partnership Program.