Water temperature is an essential element of stream habitat condition and the continuing survival of fish species. In fact, water temperature can determine whether a species can exist within a particular watershed.

In general, fish, particularly anadromous fish (fish that spend part of their life cycle in the ocean and part in freshwater), require cooler water temperatures to survive. Accordingly, we have developed a property-wide monitoring strategy that allows us to monitor changes in water temperature during the critical summer months when the water level in streams drop and rising air temperature causes water temperatures to increase.

By placing continuously recording temperature data-loggers in the streams during the summer, collecting temperatures every half-hour for four months, we are able to track the condition of Class I (fish-bearing) and Class II (other aquatic life) streams. Interestingly, we have found that some species can survive in an area even when the water temperatures rise because of what are called thermal refugia areas. These are areas that stay cooler because of deeper water or spring feed. Protection measures of the HCP that are aimed at providing adequate shade to the stream will function over time to help keep stream temperatures from rising.