Site Description
The Wasatch Environmental Observatory (WEO) integrates existing fixed and mobile field-based research infrastructure in central Utah, USA (40° 34’ N, 111° 53’ W). This distributed observational network supports research and training in multiple disciplines. The WEO is managed by the University of Utah and supported by two full-time, highly skilled technicians. The unique geography of the region allows the WEO to span gradients from relatively unimpacted mountain environments to century-old urban landscapes, all of which are facing major challenges related to global changes and a growing human population. The integration of a city-center within the study area provides benefits to the WEO, such as the ability to affix scientific instrumentation to mass transit; work with community partners to construct experimental, yet operational green infrastructure facilities; and augment WEO infrastructure with instrumentation managed by state and federal agencies.
WEO is named for the Central Wasatch Mountains, east of Salt Lake City, Utah, USA (Fig. 1A). The Wasatch Range represents the western edge of the Rocky Mountain physiographic province with the Jordan (Salt Lake) River Basin marking the eastern boundary of the Basin and Range province. The Wasatch fault bounds the range to the west and is responsible for over 2200m of relief between the mountain peaks (>3500m) and the valley floor (~1300m). The mountain block is lithologically and structurally complex with rocks ranging from Precambrian quartzites and shales to Tertiary igneous intrusions (Bryant 1990). The Jordan River Basin is bordered by mountains in all directions but the northwest, resulting in a geography that promotes atmospheric inversions in summer and winter months (Lin et al., 2018). Roughly 44% of the 2,085 km2 Jordan River catchment area is urban, with a human population of 1.1 million living in Salt Lake County that is expected to reach 1.7 million by 2065 (Perlich et al., 2017). The mainstem Jordan River receives inputs from Utah Lake at the southern extent of the basin and flows north to the Great Salt Lake. Seven major tributaries drain the Central Wasatch Mountains and discharge to the river after passing through several municipalities (Fig. 1B). Each sub-catchment thus represents varying degrees of a wildland to urban land use gradient. For example, Red Butte Canyon includes a U.S. Forest Service Research Natural Area (RNA) in its headwaters (Ehleringer et al., 1992), while high altitude areas of Big and Little Cottonwood canyons are home to multiple ski resorts.
The region has a cold, semi-arid climate with strong lapse rates in mean annual temperature (MAT) and precipitation (MAP) at the sub-catchment scale. MAT within the Central Wasatch (1300 – 3500 m) ranges from 3.5 – 6.8 °C, while MAP varies between 700 – 1300 mm. In Red Butte Creek (1300 – 2510 m), MAT is 6.8 °C and MAP is 850 mm (Gelderloos, 2018).
In Little Cottonwood Creek (1600 – 3500 m), which includes the intensively studied alpine Albion Basin, MAT is 3.5 °C, while MAP is 1300 mm. Most precipitation falls as winter snow with spring melt (April – July) providing both surface water runoff and regional groundwater recharge (Hely et al., 1971; Manning & Solomon, 2004; Bardsley, et al. 2013; Gabor et al., 2017). Numerous water diversions from tributaries and the mainstem river combined with inputs of effluent from several water reclamation facilities and canal return flows add hydrologic complexity to the system (Follstad Shah et al., 2019). The fourth-order Jordan River is on the state of Utah’s 303(d) list of impaired water bodies (U.S. Code 1313(d)(1)(A) in many of its segments due to highly regulated river flows and excessive loading of organic matter and nutrients (Follstad Shah et al., 2019).
WEO instrumentation combined with long-term climate and stream discharge data provide evidence of rapid climatic and hydrologic change in the Jordan River Basin. Mean annual air temperature in each sub-catchment has increased by approximately 1.5 °C since 1980 (Fig. 2) (Wolf, 2020; Jamison, 2020). Downscaled climate models suggest that more precipitation will fall as rain rather than snow in the future and the snow line will shift upslope by 250 m (Scalzitti et al., 2016). These changes will create flashier hydrographs within Jordan Basin tributaries, historically characterized as snowmelt dominated. Reduced flows to the Great Salt Lake, induced by shifting climate and water extraction, have already exposed more lake sediment, lending to dust storms that substantially accelerate snow melt (Skiles et al., 2018) and exacerbate air pollution in a region prone to high concentrations of fine particulate matter and the formation of photochemical smog (Lin et al., 2018; Fig. 3).
In short, hydrologic process research opportunities abound in the region given its unique geography, rapidly growing human population that puts pressure on water resources, hydrologic change resulting from the climate crisis, and clear linkages between the hydrologic cycle and air quality. We now summarize some of the major avenues of research supported by the WEO and provide greater detail about the infrastructure supporting these efforts.