Status of climate and water resources at Gila Cliff Dwellings National Monument: Water year 2018

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 Gila Cliff Dwellings National Monument (NM) to provide an integrated look at climate and water conditions during water year 2018 (October 2017–September 2018). Water year 2018 was hotter and drier than normal at Gila Cliff Dwellings National Monu-ment. Overall annual precipitation was 70.7% of normal, based on a 30-year record (1981–2010). In the fall and winter, all months except February received only 0–28% of normal rainfall. The park received 88% of normal precipitation in spring and summer. Mean month-ly maximum temperatures were all higher than normal–especially November, which aver-aged 10.6°F higher than normal. Mean monthly minimum temperatures were more variable. The reconnaissance drought index indicates that WY2018 returned to drier conditions after three wetter-than-average years. Two springs are monitored at the monument. Both had surface water present and flowing when visited in WY2018 and showed little sign of change or disturbance. This was the second water year of data for USGS stream gage 09430010. The U.S. Geological Survey maintains the equipment for this gage, and also collects and manages its data. The hydrograph for WY2018 was typical of the Upper Gila Basin, with peak streamflow occurring from February to early April. The largest flow event occurred in late February. Snowmelt and late winter storms made crucial contributions to the hydrologic season. The median value for the winter season (48.7 cfs) was about 60% greater than the spring median value (30.2 cfs) and more than 10 times the summer value (4.49 cfs). There were 248 discrete analyses of water samples collected from the West Fork Gila River index site in WY2018. Of these samples, 94 were associated with New Mexico surface-water criteria. There were no exceedances of New Mexico state water-quality standards noted in these samples, for a compliance rate of 100%. Macroinvertebrates were collected to provide data for compliance with the New Mexico biological standards. In WY2018, the index reach scored 50.14 on the New Mexico integrated biological index, putting it in the “fair” category. This index reach has been sampled with the same methods since WY2012. The index value has been near the upper 25th percentile each year—even after major fires in the monument watershed (2011–2012). These results show the resilience of the macroinvertebrate community, and the ability of the stream reach to recover after postfire flows of debris and ash.

Status of climate and water resources at Gila Cliff Dwellings National Monument: Water year 2018

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