CHARACTERIZING INTERSEASONAL CORE WATER QUALITY PARAMETERS IN BEDROCK POOLS AT SAGUARO NATIONAL PARK

Perennial and semi-perennial bedrock pools (locally referred to as tinajas,Spanish for “earthen jar”) are important water sources for both aquatic and terrestrial wildlife in the Sonoran Desert. During dry periods, these pools comprise most of the available surface water in Saguaro National Park. The hydrology of tinajas within the boundaries of the park’s Rincon Mountain District (located east of Tucson, Arizona) is poorly understood, and no long-term tinaja water quality studies had been completed previous to this study. Detailed water quality data was collected during the driest months of the year and the monsoon season in order to (1) investigate the mechanisms of tinaja hydrology (specifically, the mechanisms and timing of tinaja response to drought and precipitation), and (2) to understand how tinaja water quality (and the wildlife that depend on it) may be affected by climate change, aquifer depletion, wildfires and other effects of human activity in southwestern Arizona.

Tinajas in Chiminea Canyon and Loma Verde Canyon at Saguaro National Park were sampled for core parameters on a weekly basis during the driest period of the year (May – July 2014) through the beginning of the monsoon season (early July 2014). Two multi-parameter water quality sondes were deployed to record pH, temperature, specific conductance and dissolved oxygen at 15-minute intervals between May 22 and June 30, 2014 in Chiminea Canyon. Tinajas in three other drainages were monitored for changes in pH, specific conductivity, temperature, turbidity, and dissolved oxygen between May – July 2013. Samples were also collected from selected tinajas for isotopic (δ²H and δ¹⁸O) analysis, and each tinaja was photographed using an infrared camera to detect possible thermally distinct groundwater inputs in each pool. These data will be used to further the park’s understanding of water sources supplying spring-fed tinajas and potential threats to tinaja water quality.