The existence of an inverse limit of inverse system of measure spaces - a purely measurable case

The existence of an inverse limit of an inverse system of (probability) measure spaces has been investigated since the very beginning of the birth of the modern probability theory. Results from Kolmogorov [10], Bochner [2], Choksi [5], Metivier [14], Bourbaki [3] among others have paved the way of the deep understanding of the problem under consideration. All the above results, however, call for some topological concepts, or at least ones which are closely related topological ones. In this paper we investigate purely measurable inverse systems of (probability) measure spaces, and give a sucient condition for the existence of a unique inverse limit. An example for the considered purely measurable inverse systems of (probability) measure spaces is also given

Stream Centric Methods for Determining Groundwater Contributions in Karst Mountain Watersheds

Climate change influences on mountain hydrology are uncertain but likely to be mediated by variability in subsurface hydrologic residence times and flow paths. The heterogeneity of karst aquifers adds complexity in assessing the resiliency of these water sources to perturbation, suggesting a clear need to quantify contributions from and losses to these aquifers. Here we develop a stream centric method that combines mass and flow balances to quantify net and gross gains and losses at different spatial scales. We then extend these methods to differentiate between karst conduit and matrix contributions from the aquifer. In the Logan River watershed in Northern Utah we found significant amounts of the river water repeatedly gained and then lost through a 35‐km study reach. Further, the direction and amount of water exchanged varied over space, time, and discharge. Streamflow was dominated by discharge of karst conduit groundwater after spring runoff with increasing, yet still small, fractions of matrix water later in the summer. These findings were combined with geologic information, prior subsurface dye tracing, and chemical sampling to provide additional lines of evidence that repeated groundwater exchanges are likely occurring and river flows are highly dependent on karst aquifer recharge and discharge. Given the large population dependent on karst aquifers throughout the world, there is a continued need to develop simple methods, like those presented here, for determining the resiliency of karst groundwater resources

Quantifying Controls on Stormwater Quality in Red Butte Creek

Increased urbanization associated with population growth alters the amount, routing, and quality of stormwater runoff. This study quantifies how these processes interact to influence stormwater runoff from the University of Utah’s Research Park into Red Butte Creek. We focused on two adjacent stormwater outlets, Dentistry and Connor Road, which have sewersheds of 129 acres and 67 acres respectively. From October 2015 to November 2016 we sampled precipitation, stormwater runoff from rooftops, parking lots, roads, and turf grass, and stormwater culverts during 11 storm events. Precipitation depth and culvert discharge data were collected at regular intervals via iUTAH in situ sensors. During storm events the first pulse of stormwater runoff from these urban land covers has 3-30 times higher dissolved organic carbon and 2-3 times higher total dissolved nitrogen concentrations than precipitation. Surprisingly, the first pulse signature observed from runoff directly from urban land covers differs between stormwater culverts. During storm events, stormwater at the Dentistry culvert has elevated levels of solutes during the first flush that decrease over time, presumably due to solute source limitation. Consistent with a quick flushing event, event stormwater discharge at Dentistry culvert ends within 0.5-3 hours following cessation of precipitation. However, after a storm event stormwater discharge at Connor Road decreases to a baseflow rate observed even during long periods with no storm events. This causes the first flush to appear diluted and, as the storm wanes, solute concentrations increase towards concentrations measured in non-storm event. Concentration patterns in base cations suggest that stormwater runoff from Connor Road interacts with shallow subsurface water. These observations demonstrate that adjacent sewersheds with similar land use may exhibit very different hydrological and hydrochemical responses to rainfall. As a result, the amount and quality of stormwater is then affected by both urban land cover how runoff interacts with subsurface structure en route it to the stream

Persistent urban impacts on surface waterPersistent urban impacts on surface water quality via impacted groundwater in Red Butte Creek

Growing population centers along mountain watersheds put added stress on sensitive hydrologic systems and create water quality impacts downstream. We examined the mountain-to-urban transition in watersheds on Utah’s Wasatch Front to identify mechanisms by which urbanization impacts water resources. Rivers in the Wasatch flow from the mountains directly into an urban landscape, where they are subject to channelization, stormwater runoff systems, and urban inputs to water quality from sources such as road salt and fertilizer. As part of an interdisciplinary effort within the iUTAH project, multiple synoptic surveys were performed and a variety of measurements were made, including basic water chemistry along with discharge, water isotopes, and nutrients. Red Butte Creek, a stream in Salt Lake City, does not show significant urban impact to water quality until several kilometers after it enters the city where concentrations of solutes such as chloride and nitrate more than triple in a gaining reach. Groundwater springs discharging to this gaining section demonstrate urban-impacted water chemistry, suggesting that during baseflow a contaminated alluvial aquifer significantly controls stream chemistry. By combining hydrometric and hydrochemical observations we were able to estimate that these groundwater springs were 17-20% urban runoff. We were then able to predict the chemistry of urban runoff that feeds into the alluvial aquifer. Samples collected from storm culverts, roofs, and asphalt during storms had chemistry values within the range of those predicted by the mixing model. This evidence that urbanization affects the water quality of baseflow through impacted groundwater suggests that stormwater mitigation may not be sufficient for protecting urban watersheds, and quantifying these persistent groundwater mediated impacts is necessary to evaluate the success of restoration efforts. Further work involves using fluorescence analysis of dissolved organic matter chemistry and microbial genomics to identify “fingerprints” of urban impacts to water quality

Persistent Urban Influence on Surface Water Quality via Impacted Groundwater

Growing urban environments stress hydrologic systems and impact downstream water quality. We examined a third-order catchment that transitions from an undisturbed mountain environment into urban Salt Lake City, Utah. We performed synoptic surveys during a range of seasonal baseflow conditions and utilized multiple lines of evidence to identify mechanisms by which urbanization impacts water quality. Surface water chemistry did not change appreciably until several kilometers into the urban environment, where concentrations of solutes such as chloride and nitrate increase quickly in a gaining reach. Groundwater springs discharging in this gaining system demonstrate the role of contaminated baseflow from an aquifer in driving stream chemistry. Hydrometric and hydrochemical observations were used to estimate that the aquifer contains approximately 18% water sourced from the urban area. The carbon and nitrogen dynamics indicated the urban aquifer also serves as a biogeochemical reactor. The evidence of surface water–groundwater exchange on a spatial scale of kilometers and time scale of months to years suggests a need to evolve the hydrologic model of anthropogenic impacts to urban water quality to include exchange with the subsurface. This has implications on the space and time scales of water quality mitigation efforts