2007

Wavelet Analysis And Filtering To Identify Principal Directions Of Permeability Anisotropy

Anonymous — Thu, 23 Aug 2018 17:22:24 +0000

Wavelet Analysis And Filtering To Identify Principal Directions Of Permeability Anisotropy Anonymous (not verified) Thu, 08/23/2018 - 11:22 Loring P Watkins

Watkins, Loring P ¹ ; Neupauer, Roseanna M ²

¹ University of babyֱ��app at Boulder
² University of babyֱ��app at Boulder

An accurate representation of permeability anisotropy is needed to accurately model the rate and direction of groundwater flow. Wavelet analysis can be used to characterize principal directions of permeability anisotropy; however, if the permeability field contains regions with different principal directions, wavelet analysis may only identify the principal direction of the primary region. We present a combined wavelet analysis and filtering method to characterize primary and secondary principal directions of permeability anisotropy.

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Cosmogenic Signatures Of Glacial Erosion And Retreat, Front Range And San Juan Mountains, babyֱ��app

Anonymous — Thu, 23 Aug 2018 17:21:48 +0000

Cosmogenic Signatures Of Glacial Erosion And Retreat, Front Range And San Juan Mountains, babyֱ��app Anonymous (not verified) Thu, 08/23/2018 - 11:21 Dylan J Ward

Ward, Dylan J ¹ ; Anderson, Robert S ² ; Briner, Jason P ³ ; Guido, Zackry S ⁴

¹ University of babyֱ��app, Dept. of Geological Sciences and INSTAAR
² University of babyֱ��app, Dept. of Geological Sciences and INSTAAR
³ State University of New York at Buffalo, Dept. of Geology
⁴ University of babyֱ��app, Dept. of Geological Sciences and INSTAAR

We use cosmogenic radionuclide (CRN) exposure ages to constrain numerical simulations of deglaciation histories in the Middle Boulder Creek drainage, babyֱ��app Front Range, and the Animas River valley, San Juan Mountains, babyֱ��app. We present 14 new ¹⁰Be exposure ages from glacially polished bedrock sampled in the Middle Boulder Creek valley. All of these ages are younger than a ~17 ka ¹⁰Be terminal moraine age reported by Schildgen and Dethier (2002). Ages appear to decrease monotonically with distance upvalley from the moraine, and the youngest ages in the uppermost valley are uniformly ~13 ka. We include 4 ¹⁰Be ages in a cross section across the mid-valley, which show a pattern of Last Glacial Maximum (LGM) ages (12-14 ka) within the glacial footprint, and older exposure ages (~40 ka) near the trim lines. A similar age trend is seen in the Animas River valley in southwestern babyֱ��app, which was occupied by a lobe of the LGM ice sheet that capped the San Juan mountains. Deglaciation began here ca. 19.4 ka, based on a ¹⁰Be depth profile in a proglacial terrace. A longitudinal transect of exposure ages from glacially polished samples indicates that terminus retreat proceeded at ~15 m/yr until complete deglaciation ca. 12.3 ka. Neither valley has obvious recessional deposits within the LGM glacial footprint. The first-order trend in each valley is a monotonic glacial retreat, but there are other possible retreat scenarios. For instance, we would like to test whether the same trend in ¹⁰Be concentrations could be generated by episodic retreat punctuated by periods of readvance. To investigate these scenarios, we modified the GC2D numerical glacier simulation (see Kessler et al., 2006) to incorporate a CRN accumulation layer. This layer can contain any starting value of CRN concentration. Production over each timestep is scaled to DEM latitude and altitude. Production is taken to be zero in areas covered by more than 10 m of ice. The CRN inventory can also decline due to glacial erosion. We incorporate a selectable erosion rule based on basal sliding or total ice velocity, ice discharge, ice power, or basal shear stress, and calculate the reduction in CRN inventory by the depth stripped in each timestep. We then simulate a glacier responding to equilibrium line altitude (ELA) changes imposed stepwise, gradually, or scaled to the GRIP δ¹⁸O record. Each scenario generates a pattern of ages in the CRN layer that can be compared with the map pattern of measured ¹⁰Be ages. Initial results show that a step-function ELA rise to its present value causes a retreat that is too rapid to explain the range of ages observed in both valleys. A steady ELA rise can replicate the monotonic age trend, while an episodic retreat with readvances results in several "domains" of similar ages within the LGM glacial footprint.

Kessler, M.A., Anderson, R.S., Stock, G., 2006. Modeling topographic and climatic control of east-west asymmetry in Sierra Nevada Glacier length during the Last Glacial Maximum. Journal of Geophysical Research Vol. 111(F2, F02002).
Schildgen, T., Dethier, D.P., Bierman, P., Caffee, M., 2002. Cosmogenic Age Estimates for Pinedale and Bull Lake Moraines in babyֱ��app. Unpublished manuscript.

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Characterizing And Incorporating Uncertainty In Drinking Water Quality And Treatment

Anonymous — Thu, 23 Aug 2018 17:21:05 +0000

Characterizing And Incorporating Uncertainty In Drinking Water Quality And Treatment Anonymous (not verified) Thu, 08/23/2018 - 11:21 Erin L Towler

Towler, Erin L ¹ ; Rajagopalan, Balaji ² ; Summers, Scott ³ ; Seidel, Chad ⁴

¹ University of babyֱ��app at Boulder
² University of babyֱ��app at Boulder
³ University of babyֱ��app at Boulder
⁴ Damon S. Williams

Drinking water utilities face complex decisions when balancing new and changing regulatory requirements with competing finished water quality objectives. Tools are needed to help utilities better understand treatment plant performance in light of natural influent water quality variability and regulation compliance. To this end, the natural variability of select water quality variables in the United States were characterized in terms of their spatial and temporal variability. Based on these relationships, a K-nearest neighbor (K-NN) bootstrap technique was developed to generate ensembles of influent water quality. Next, a statistical model was developed to simulate conventional water treatment using local polynomial (nonparametric) regression methods. Finally, input uncertainty was incorporated into the model to see output scenarios and the probability of exceeding a given regulation limit.

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INVITED FACULTY TALK - Global Predictions Of River Discharge And Sediment Load Under Human Influence

Anonymous — Thu, 23 Aug 2018 17:20:25 +0000

INVITED FACULTY TALK - Global Predictions Of River Discharge And Sediment Load Under Human Influence Anonymous (not verified) Thu, 08/23/2018 - 11:20 James Syvitski

Syvitski, James ¹

¹ Environmental Computation and Imaging Group, INSTAAR, University of babyֱ��app at Boulder

The UNH water balance and transport model (WBM), based on the STN-30p network, provides a fundamental structure for analyzing the water and sediment flux distribution by river basin, continent, climatic zone, and receiving ocean or sea. WBM estimates of discharge are constrained by observed hydrographic data from the Global Runoff Data Centre (GRDC) archive, covering 76 Mkm2 (72%) of the world’s actively discharging landmass. WBM discharge estimates derived from modern climatology were used to develop correction factors and then revised to account for human-induced losses of water within basins caused by inter-basin water diversions or irrigation losses to the atmosphere. The resulting composite discharge field is a mix of observed discharge and WBM simulations where observations are not available, at a 0.5° by 0.5° resolution (latitude, longitude) for monthly climatology.

Sediment flux to the coastal zone is conditioned by geomorphic and tectonic influences (basin area and relief), geography (temperature, runoff), geology (lithology, ice cover), and human activities (reservoir trapping, soil erosion). A new model, termed “BQART” in recognition of those factors, accounts for these varied influences. When applied to a database of 488 rivers, the BQART model showed no ensemble over- or under-prediction, had a bias of just 3% across six orders of magnitude in observational values, and accounted for 96% of the between-river variation in the long-term (≈30 years) sediment load or yield of these rivers. The geographical range of the 488 rivers covers 63% of the global land surface and is highly representative of global geology, climate, and sociobabyֱ��app conditions. The BQART model makes possible the quantification of the influencing factors (e.g., climate, basin area, ice cover) within individual basins, to better interpret the terrestrial signal in marine sedimentary records.

Combining the BQART model with a load variability (PSI) model allows for time-variations in sediment flux to be estimated for global rivers. The seasonal flux of sediment of global rivers, on a river-by-river basis under modern and pre-human conditions, is estimated. Humans have simultaneously increased the sediment transport by global rivers through soil erosion (by 2.3 ± 0.6 billion metric tons per year), yet reduced the flux of sediment reaching the world’s coasts (by 1.4 ± 0.3 billion metric tons per year) because of retention within reservoirs. African and Asian rivers carry a greatly reduced sediment load; Indonesian rivers deliver much more sediment to coastal areas.

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INVITED FACULTY TALK - Colloids, Contaminants, And Surface Chemistry: Effect Of Desorption Kinetics On The Facilitated Transport Of Cesium And Strontium By Illite Colloids

Anonymous — Thu, 23 Aug 2018 17:19:43 +0000

INVITED FACULTY TALK - Colloids, Contaminants, And Surface Chemistry: Effect Of Desorption Kinetics On The Facilitated Transport Of Cesium And Strontium By Illite Colloids Anonymous (not verified) Thu, 08/23/2018 - 11:19 Joseph N Ryan

Ryan, Joseph N ¹

¹ University of babyֱ��app, Boulder

We investigated the transport of the cations Cs+ and Sr2+ in flow-through and recirculating saturated quartz porous media in the absence and presence of illite colloids to examine the effect of cation desorption kinetics on colloid-facilitated transport. The illite colloids were equilibrated with radioactive isotopes of the cations (137Cs, 90Sr) at different ratios of colloid to cation concentrations. The colloid-cation suspensions were injected through the column at pH 7.3 and an ionic strength of 0.1 mM. In the flow-through column, the presence of colloids accelerated the transport of the cations. The time to breakthrough of the cations decreased as the ratio of colloid to cation concentrations increased. For a given colloid concentration, the breakthrough of Cs+ was more rapid than that of Sr2+. Analysis of the breakthrough data with a colloid-facilitated transport model showed that time to breakthrough decreased as cation association with the colloids increased and the rate of desorption of cations from the illite decreased. In the recirculating column, Sr2+ desorbed from the illite colloids more rapidly than Cs+. Initially, Cs+ desorbed from the colloids, but over time, the colloidal concentration of Cs+ increased. We attribute the accumulation of Cs+ on the colloids to the slow transfer of Cs+ to strong binding (“frayed edge”) sites on the illite colloids.

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INVITED FACULTY TALK - Surface-Layer Armoring And Its Effect On Sediment Transport In High-Gradient Channels

Anonymous — Thu, 23 Aug 2018 17:19:03 +0000

INVITED FACULTY TALK - Surface-Layer Armoring And Its Effect On Sediment Transport In High-Gradient Channels Anonymous (not verified) Thu, 08/23/2018 - 11:19 John Pitlick

Pitlick, John ¹ ; Mueller, Erich ² ; Segura, Catalina ³

¹ Geography Department, CU-Boulder
² Geography Department, CU-Boulder
³ Geography Department, CU-Boulder

In high-gradient channels the sediment which is present on the bed surface (the armor layer) is typically much coarser than the sediment which moves as bed load during high-flow events. The difference in sediment sizes has lead to the notion that bed load transport in these channels is supply limited, meaning the mass transport rate of sediment is governed by the availability of the different sizes, not the flow properties. Studies we have conducted over the last 10 years challenge this assumption. We have investigated trends in bed load transport in relation to flow and channel properties at more than 100 sites on gravel-bed streams and rivers in babyֱ��app and Utah. In addition we have conducted extensive analyses of flow and transport measurements from streams in Idaho to develop new relations for bed load transport in steep streams with high relative roughness. Slopes at our study sites range from 0.0003 to 0.07; bankfull depths range from 0.2 to 5 m; and bankfull widths range from 2 to 200 m. Our results indicate that as channels get steeper and smaller toward their headwaters, the bed becomes increasingly well-armored, and the material supplied to the channel as bed load tends to be much finer than the sediment that forms the armor layer. These finer sizes would be entrained and transported quite easily were it not for the rate-limiting effects introduced by the armor layer; coarse clasts within the armor layer hinder the movement of finer grains, thus limiting their mobility in relation to the available shear stress. The transport relations we have developed indicate that the shear stress available to move sediment in gravel channels increases in proportion to the threshold shear stress, thus, even in the steepest channels, transport occurs a few days per year, resulting in appreciable sediment transport over a period of years. We propose that in undisturbed gravel-bed streams and rivers there is a tradeoff in the frequency and intensity of bed load transport such that the total load carried in small, steep cobble-bedded channels tends to balance the total load carried in large, low-gradient channels. Our results have implications for water resources management, conceptual theories of ecosystem structure, and models of landscape evolution.

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Tracing Changes In Carbon Chemistry Caused By An Extreme Mid-Summer Rain Event In A Lake-Stream System In The babyֱ��app Rocky Mountains

Anonymous — Thu, 23 Aug 2018 17:18:09 +0000

Tracing Changes In Carbon Chemistry Caused By An Extreme Mid-Summer Rain Event In A Lake-Stream System In The babyֱ��app Rocky Mountains Anonymous (not verified) Thu, 08/23/2018 - 11:18 Matthew Miller

Miller, Matthew ¹ ; McKnight, Diane ² ; Alexa, Katherine ³

¹ INSTAAR, Environmental Engineering
² INSTAAR, Environmental Engineering
³ Cornell University

We studied the impact of a sustained high elevation rain event in mid-summer on the biogeochemistry of dissolved organic material (DOM) in aquatic ecosystems in the babyֱ��app Front Range. In the Green Lakes Valley, the hydrology and the character of the DOM are defined by two distinct periods: snowmelt and baseflow. Surface water samples were collected from the outlet of a small alpine lake as well as the outlet of a larger subalpine lake from the initiation of snowmelt into the fall. From July 7-9, 2006 a continuous low intensity rain event produced approximately 9 cm of precipitation.

As a result of the storm, the fluorescence characteristics of the DOM and the percent fulvic acid contribution to the sample were reset to values similar to those observed during snowmelt at the alpine site but were relatively unaffected at the subalpine site. Similarly, the alpine system was more responsive to changes in primary productivity. These results suggest that alpine ecosystems are more sensitive to hydrologic and biological changes than subalpine ecosystems and that residence times of the lakes as well as watershed area play an important role in regulating stream chemistry.

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Storm And Diel Surface-Water Chemistry Variations In The Red River Near Questa, New Mexico

Anonymous — Thu, 23 Aug 2018 17:17:36 +0000

Storm And Diel Surface-Water Chemistry Variations In The Red River Near Questa, New Mexico Anonymous (not verified) Thu, 08/23/2018 - 11:17 R. Blaine McCleskey

McCleskey, R. Blaine ¹ ; Verplanck, Phillip L. ² ; Nordstrom, D. Kirk ³

¹ University of babyֱ��app
² USGS
³ USGS

Mining operations and runoff from hydrothermal scars can affect the Red River water quality. Three water samples were collected at the USGS Questa gage, the first was collected 6 hours before a rainstorm that occurred on 9/17-18/02, the second close to the peak discharge about 14 hours after the rainstorm began (9/18/02), and the third during the falling limb of the hydrograph the following day (9/19/02). The discharge at the USGS Questa gaging station increased from 7 to a maximum of 90 cfs. Runoff from hydrothermally altered scars reached the Red River causing it to become acidic and highly turbid. From the first to the second sample, pH decreased from 7.8 to 4.8, alkalinity decreased from 50 to <1 mg/L, SO4 increased from 160 to 320 mg/L, dissolved Fe increased from to 0.01 to 0.60 mg/L, dissolved Al increased from 0.19 to 2.9 mg/L, and dissolved Zn increased from 0.056 to 0.61 mg/L. The total recoverable concentrations (unfiltered and acidified with HNO3) of Fe and Al increased from the first to the second sample by nearly 2 and 1 orders of magnitude, respectively; and the second sample contained mostly particulate Fe (99%) and Al (85%). When the third sample was collected, the total recoverable concentrations of Fe and Al had decreased by 7- and 4- fold from the second sample, but a much higher proportion of the Fe (44%) and Al (77%) were dissolved. The proportion of total dissolved Fe that was Fe(III) decreased from 67% to 29% from the first to the second sample and increased to 90% when the third sample was collected. The next month’s sample demonstrated that a longer time was required for total recoverable concentrations, proportions of dissolved to particulate, and proportions of Fe(III) to total Fe to decrease to pre-storm levels.

Diel samples were collected during high-flow (5/03) and low-flow (10/03) conditions. Diel sampling was conducted at 2 sites: the USGS gage and just upstream of the mill above the influence of any mining activities. At both sites during high-flow and at the gage during low-flow, concentrations of chemical constituents changed minimally. Above the Questa mine mill during low-flow, the pH increased during the day from 8.15 to 8.34 due to CO2 degassing. Dissolved Zn and Mn concentrations had a diel pattern (and only for low-flow) decreasing to a minimum in the afternoon and increasing during the night.

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Quantifying Nitrate Uptake In An Unsteady, Anabranching, Antarctic Stream

Anonymous — Thu, 23 Aug 2018 17:16:48 +0000

Quantifying Nitrate Uptake In An Unsteady, Anabranching, Antarctic Stream Anonymous (not verified) Thu, 08/23/2018 - 11:16 Joshua C Koch

Koch, Joshua C ¹ ; McKnight, Diane M ² ; Neupauer, Roseanna ³ ; Baeseman, Jennifer ⁴ ; Gooseff, Michael ⁵ ; Rajagopalan, Balaji ⁶

¹ University of babyֱ��app
² University of babyֱ��app
³ University of babyֱ��app
⁴ Kent State University
⁵ babyֱ��app School of Mines
⁶ University of babyֱ��app

In the McMurdo Dry Valleys of Antarctica, biotic uptake limits nitrogen transport in glacial meltwater streams containing abundant cyanobacterial mats. Nitrogen is delivered to lakes predominantly from streams with minimal mat growth, such as Huey Creek. We injected nitrate into Huey Creek to quantify nitrogen uptake in a mat-less stream. Tracer data is typically analyzed with a transient storage model (TSM), which accounts for changes in tracer concentration by modeling storage, lateral inflows, and biological processes. Daily flood pulses in Huey Creek lead to temporal and spatial variations in hyporheic exchange, storage, and nutrient decay, precluding use of a TSM. Instead, we use a groundwater flow model and Principle Component Analyses (PCA) to explore hydrology and biology in Huey Creek. The groundwater model identifies a second storage zone besides the hyporheic zone and suggests significant down-gradient transport of the stored water. The groundwater flow model agrees with tracer breakthrough curves, suggesting a residence time in this second storage zone of approximately 30 hours – two orders of magnitude greater than hyporheic storage measured using a TSM at low flow conditions in Huey Creek (Runkel et al. 1998). Coupled PCAs identify gaining and losing stream reaches consistent with the groundwater model, isolate biological uptake from nitrate variations caused by streamflow variability and tracer dilution, and divide uptake into a flow-induced and flow-independent fraction. Results suggest that the bacteria require approximately 15 hours to fully respond to the nitrate enrichment, and hint that the large storage zone may exert control on storage and uptake of nitrate in Huey Creek.

Runkel R. L., D. M. McKnight, and E. D. Andrews. 1998. Analysis of transient storage subject to unsteady flow: Diel flow variations in an Antarctic stream. J. N. Am. Benthol. Soc 17: 143-154.

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The Effects Of Photobleaching On Spectroscopic Properties Of Fulvic Acids Isolated From A Tropical Wetland, The Okavango Delta, Botswana

Anonymous — Thu, 23 Aug 2018 17:16:06 +0000

The Effects Of Photobleaching On Spectroscopic Properties Of Fulvic Acids Isolated From A Tropical Wetland, The Okavango Delta, Botswana Anonymous (not verified) Thu, 08/23/2018 - 11:16 Cuong T Huynh

Huynh, Cuong T ¹ ; Mladenov, Natalie ²

¹ University of babyֱ��app at Boulder
² University of babyֱ��app at Boulder

The aquatic and terrestrial plants of the Okavango Delta are important contributors to the pool of dissolved organic matter (DOM) and have an important role in biogeochemical cycling in this large tropical wetland system (Figure 1; Mladenov et al., 2005). As the DOM flows across the length of the Delta (approximately 400 km), we hypothesize that sunlight essentially degrades the dissolved organic compounds derived from vegetation allowing it to be more readily available for uptake by microbes and other plant life. In order to evaluate the effects of ultra-violet (UV) light on the spectroscopic (fluorescence and UV-vis absorbance) properties of plant-derived DOM from this wetland, we exposed fulvic acids, isolated from the Okavango Delta, to UV light in the laboratory using a solar simulator. The two fulvic acids examined for this research study were collected from 1) a leaching Cyperus papyrus stand in the upstream Permanent Swamp of Okavango Delta (CPLFA) and 2) a channel in the Seasonal Swamp (SSFA), a seasonally-flooded hydrotone downstream that contains DOM derived from a greater variety of vegetation.

The effects of UV light on DOM are believed to result in a breakdown of the aromatic compounds in DOM, reflected in lower absorbance values. Also, previous research has shown that the fluorescence index (FI), a ratio of fluorescence intensities measured at an excitation of 370 nm (McKnight et al., 2001), generally decreases over time of irradiation by UV light (Mladenov, unpublished). During the four hours of irradiation in the experiments of this study, we did not see a decrease in the UV absorbance in either the SSFA or CPLFA samples (Table 1). However, a decrease in the FI was observed (Table 1). Figure 2 shows that the dominant peaks in three-dimensional excitations and emissions matrices (EEMs) did diminish with time of irradiation. We also used parallel factor analysis (PARAFAC; Cory and McKnight, 2005) to fit our EEMs to a model (Cory and McKnight, 2005) of thirteen components responsible for fluorescence, consisting of oxidized and reduced quinones, proteins, and unknown compounds. Model results showed that all fluorescence components decreased evenly over time and that the sum of all components was reduced by almost half after four hours of irradiation. These findings suggest that compounds responsible for fluorescence are intensely degraded by UV light, while the aromatic nature of the DOM may be less affected than previously believed. Additional measurements of dissolved organic carbon concentrations (DOC) are needed to examine UV light effects on both DOC content and specific UV absorbance. We conclude that these changes happen relatively quickly after exposure of DOM to UV light, which may have important implications for biogeochemical cycling in the Okavango Delta.

Cory, R.M. and D.M. McKnight, 2005. Fluorescence spectroscopy reveals ubiquitous presence of oxidized and reduced quinones in dissolved organic matter. Environmental Science and Technology. 39: 8142-8149.
McKnight, D. M., E. W. Boyer, P. K. Westerhoff, P. T. Doran, T. Kulbe, and D. T. Andersen, 2001. Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity. Limnology and Oceanography. 46: 38-48.
Mladenov, N., D.M. McKnight, P. Wolski, L. Ramberg, 2005. Effects of annual flooding on dissolved organic carbon dynamics within a pristine wetland, the Okavango Delta of Botswana. Wetlands. 25 (3): 622-638.

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