Status of climate and water resources at Montezuma Castle and Tuzigoot national monuments: Water year 2018

Gwilliam, Evan; Palacios, Laura; Raymond, Kara

Climate and hydrology dramatically shape ecosystem structure and function, particularly in arid and semi-arid ecosystems. Understanding changes in climate and water resources is central to assessing the condition of park biota as well as key cultural resources. This document summarizes climate and water resource conditions for water year (WY) 2018 for Montezuma Castle and Tuzigoot national monuments, two small National Park Service units in central Arizona. Overall annual precipitation was 49% of normal for Montezuma Castle National Monument (NM) and 76% of normal for Tuzigoot NM, with extremely low rainfalls in the fall and winter months. Mean monthly maximum temperatures at both parks were above normal for all months except one at Montezuma Castle. Mean monthly minimum temperatures were more variable and there were approximately the same number of extremely cold days as normal. The reconnaissance drought index was negative for Tuzigoot NM—showing a return to drought conditions following recent wetter years—and likely negative for Montezuma Castle NM. Groundwater levels at the Montezuma Castle and Montezuma Well water-supply wells in WY2018 both declined from WY2017, by 24.20 and 8.10 feet, respectively. However, both wells had been recently pumped, so those values may not represent actual conditions. Over the monitoring record, water levels at the Castle unit have been variable with no discernible trend, while water levels at the Well unit have generally declined. In WY2018, groundwater levels in the three monitoring wells near Tuzigoot NM showed variable changes from the previous year. The Kauzlarich index well increased 1.60 feet, the Centerville USGS well decreased 0.45 feet, and the City of Cottonwood index well #1 decreased 3.70 feet. All three wells have shown relatively stable groundwater levels since 1999. Expansion Spring (Montezuma Castle NM Castle unit) and Shea Spring (Tuzigoot NM) were both classified as “undisturbed,” despite some evidence of beaver activity at Shea Spring. Sensors indicated that both springs were likely wetted throughout the sampling period. We are currently establishing the range of natural variation for water-quality results. Mean daily discharge from the Beaver Creek station was 7.13 cubic feet per second (cfs), approximately one-tenth of the mean value from WY2005 to 2008. At Wet Beaver Creek, mean daily discharge during WY2018 was 7.05 cfs, well below the gage record mean of 30.2 cfs. There was a striking lack of flow events, including from snowmelt and monsoon events. Recorded flow at the Verde River gage was either at or below the 25th percentile for most of the year. The hydrograph at this gage showed patterns similar to those at the Wet Beaver Creek gage—there was no snowmelt pulse observed this year. There were 10 exceedances of water-quality standards during WY2018: seven on Beaver Creek (one E. coli, three dissolved oxygen, and three total arsenic), one on Wet Beaver Creek (total arsenic), and two on the Verde River (one E. coli and one total lead). This was a 94% compliance rate across the three units. Macroinvertebrate index values for warmwater streams were likely attaining at all sample sites. The values for Beaver and Wet Beaver Creek were the highest recorded by SODN. This was good news after several years of either not attaining or scoring in the inconclusive category.

Status of climate and water resources at Montezuma Castle and Tuzigoot national monuments: Water year 2018

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