CHALLENGES OF MANAGING THE HOT CREEK THERMAL AREA, INYO NATIONAL FOREST, CALIFORNIA

Hot Creek thermal area, located 12 km east of Mammoth Lakes, in eastern California, includes about 2 km² in a narrow gorge occupied by a snow-melt fed stream along which numerous subaerial and subaqueous thermal springs discharge water and steam. The area is managed by the Forest Service as a geologic interpretative site and is a popular tourist attraction. Recreational use at the site includes swimming, fishing, hiking, bird watching, and geologic education. Visitor usage is high and varies seasonally between approximately 50 and 300 people per day in the winter and summer respectively. Swimming is the most challenging recreational use to manage because of the large number of people who choose to use the site for boisterous group gatherings, sometimes involving alcohol. The Forest Service has developed a number of management measures that address this issue but it has been primarily focused on “crowd control”. Geologic interpretation has been supported by the Forest Service but it is a secondary activity.

The thermal springs range from small seeps to fountaining springs and azure blue pools 10m across, some at ambient boiling temperature (93^oC). The locations and discharge rates change when spring vents become sealed by mineral deposition and new springs emerge, sometimes suddenly, when the mineral seals are fractured from ground shaking during local earthquakes.

In May 2006, three subaqueous springs in and near the most popular swimming areas suddenly began fountaining, sending hot sediment laden water spouts to 2 m above the stream surface. The fountaining is randomly cyclical with a period of several minutes between eruptions. These characteristics led the Forest Service to temporarily close the area to swimming. The cause of the sudden change in spring behavior is unclear but may relate to increases in temperature in the shallow thermal aquifer supplying the springs.

The Forest Service is currently deciding what is the appropriate level of geologic monitoring for this site and how it can be completed using limited staff and funding. The goal of the Forest Service is to educate the public on the on the natural geologic phenomena, balance the needs and expectations of the different recreational user groups, while protecting there health and safety while visiting the Hot Creek Geologic Site.