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.