Status of climate and water resources at Tumacácori National Historical Park: Water year 2017

Filippone, Colleen; Gwilliam, Evan; Palacios, Laura; Raymond, Kara

Climate and hydrology are major drivers of ecosystems. They dramatically shape ecosys-tem structure and function, particularly in arid and semi-arid ecosystems. Understanding changes in climate, groundwater, streamflow, and water quality is central to assessing the condition of park biota and key cultural resources. This report combines data collected on climate, groundwater, and surface water at Tumacácori National Historical Park to provide an integrated look at climate and water conditions during water year 2017 (October 2016–September 2017). Overall annual precipitation was 126% of normal. A wet winter and strong monsoon season made up for below normal rainfall in the early fall and early spring. Temperatures at Tumacá-cori NHP tended to be warmer than normal and there were substantially fewer extremely cold days. The reconnaissance drought index indicated that the regional drought that began in 2000 continued through WY2017. The three monitored wells at Tumacácori NHP indicated that mean groundwater levels in WY2017 were higher than the mean of the data record for each well (0.18–0.48 ft). Water lev-els in both the shallow and deep aquifer wells dropped in response to dry spring conditions, and then quickly increased with monsoon precipitation and flow events. However, seasonal variability was more dramatic in the shallow aquifer. Streamflow data for this report were recorded at USGS gauge 09481740, on the Santa Cruz River at Tubac, Arizona. Streamflow on the Santa Cruz River through the park was below av-erage in WY2017. In fact, discharge in the Santa Cruz was slightly above the 25th percentile for a majority of the water year. Spring and early summer discharge was below normal, with dry-ing/no flow events likely occurring during the end of June and early July. The WY2017 mon-soon was generally above average, providing average flow into the fall. Peak flow occurred on July 23, followed by a flow event of nearly the same magnitude on August 1. This gauge is located five kilometers downstream from the index sampling site in Tumacácori NHP. Water samples were collected from the Santa Cruz River at the Santa Gertrudis index site. Of 85 individual analyses associated with Arizona surface-water criteria, there was one exceedance (for E. coli); that is, 99% of samples were compliant with state standards. Relative to macro-invertebrates, the Arizona Index of Biological Integrity value has been at or below impaired status since WY2012 (although there is not an established index threshold for effluent-dom-inated streams in Arizona). Given the circumstances, the stability of diversity and abundance of mayflies (Ephemeroptera) and caddisflies (Trichoptera)—and low abundance of indicators of poor water quality, such as midge larvae (Chironomidae)—indicated that the habitat and water quality at the index reach were generally positive. Three taxa of fish were collected dur-ing collaborative sampling at the Santa Gertrudis index reach: longfin dace (Agosia chryogas-ter), Gila topminnow (Poeciliopsis occidentalis), and western mosquitofish (Gambusia affinis). This was the second documentation of the federally endangered Gila topminnow in the index reach since 2002. The continued presence of longfin dace and an increase in Gila topminnow are positive indicators of the animals’ response to improved water quality and habitat features on this reach.

Status of climate and water resources at Tumacácori National Historical Park: Water year 2017

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