2008

Save Our Snow: Predicting Ski Conditions And Mountain Hydrology For The Years 2030 And 2100, Rocky Mountains

Anonymous — Thu, 23 Aug 2018 17:03:07 +0000

Save Our Snow: Predicting Ski Conditions And Mountain Hydrology For The Years 2030 And 2100, Rocky Mountains Anonymous (not verified) Thu, 08/23/2018 - 11:03 Mark W Williams

Williams, Mark W ¹

¹ CU-Boulder

Mountains, like the polar regions, are likely to experience the effects of global warming before lowland sites. Seasonally snow-covered areas are like canaries in a coal mine; early warning systems that climate change is occurring. Small increases in air temperature can cause snowfall to change to rainfall. A reduction in snowfall will decrease water availability, cause ski areas to shut down, and potentially push alpine tundra off the tops of mountains as treeline rushes uphill. Mountains make their own weather. Predicting future climate in mountain areas is very difficult. Here I downscale GCM output as climate drivers to predict snowfall for Aspen Ski Mountain and surrounding areas in the years 2030 and 2100. Ski conditions and hydrological responses for those years are shown and discussed.

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INVITED KEYNOTE PRESENTATION - Two Talks In One: Hydromorphology – The Human/Hydrologic Footprint And A Methodology For A National Water Census

Anonymous — Thu, 23 Aug 2018 17:02:24 +0000

INVITED KEYNOTE PRESENTATION - Two Talks In One: Hydromorphology – The Human/Hydrologic Footprint And A Methodology For A National Water Census Anonymous (not verified) Thu, 08/23/2018 - 11:02 Richard M Vogel

Vogel, Richard M ¹

¹ Tufts University, Department of Civil and Environmental Engineering

A general introduction to the new field of ‘hydromorphology’ will be given. Hydromorphology is to hydrology, as geomorphology is to geology. Hydromorphology deals with the evolution and structure of systems. There are very few water systems which are not subjected to anthropogenic influences such as land use, water use and climate change. Hydromorphology deals with the challenges of sorting out the impacts of these various anthropogenic influences on the hydrologic cycle.

Water availability for both human and ecosystem needs is projected to be a critical national and global challenge in the 21st century. Water availability for human and ecosystem needs is confounded by agricultural irrigation, land use modifications, climate change and the depletion and pollution which results from human withdrawals and return flows from rivers as well as aquifer depletion. New challenges have been issued for a regular and systematic assessment of water resources at national and global scales. In the United States, Congress asked the U.S. Geological Survey to outline an approach for a national assessment of water availability and use, and the White House Office of Science and Technology Policy has recently called for a “national water census”. Interestingly, the last national water census was performed over 35 years ago and in the interim an explosion in computer technology, spatially distributed database management systems and anthropogenic change leads one to ask numerous questions relating to how such a national water census should proceed. A generalized approach to performing a national water census based primarily on readily available climatic, hydrologic, land-use, water-use and other demographic data will be described. The approach will be applied to a number of regions within the U.S. over a wide range of spatial and temporal scales. The approach involves a number of innovations including: the development of new indicators of water stress, definition of water management units, choice of the correct spatial and temporal scale for assessing water stress and the management of green and blue water sources.

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Spatial Variations In Sediment Transport Intensity And Their Effects On Benthic Organisms In A Mountain River, CO.

Anonymous — Thu, 23 Aug 2018 17:01:28 +0000

Spatial Variations In Sediment Transport Intensity And Their Effects On Benthic Organisms In A Mountain River, CO. Anonymous (not verified) Thu, 08/23/2018 - 11:01 Caitlin Segura

Segura, Catalina ¹ ; Pitlick, John ²

¹ University of Colorado
² University of Colorado

The spatial variability of sediment transport intensity at the reach scale is controlled both by the available shear stress, τ, and the grain size distribution of the channel bed. This variability creates patches in the bed with different disturbance regimes that in turn influence the spatial and temporal variability of benthic communities. Two-dimensional flow modeling was used to compute τ for several discharge levels in three reaches of the Williams Fork River, CO. The distributions of τ were evaluated and used, with detailed measurements of grain size distribution of the bed, to investigate the spatial variability of channel bed disturbance and to compute sediment transport intensity. The relationship between transport intensity and periphyton recovery was investigated by comparing the rate of Chl a accrual over time during two years with contrasting disturbance intensity (2004 and 2005), and by looking at the relationship between the spatial variation of disturbance intensity and benthic Chl a during the summer season of 2007.

It was found that, even though mean τ values for a given flow size are highly variable among sites, the properties of the normalized distributions of shear stress are similar across sites (Fig. 1). Analysis of sediment transport intensity indicated that most of the bedload in the study sites is composed by intermediate grain sizes (16-45mm) carried through places in the bed that experience the highest range of shear stress. In addition, transport intensity influences the post-flood accrual pattern of periphyton in years of both low and high peak flows, the accrual of periphyton is faster when the preceding peak flow is smaller, and the accrual rate of periphyton is not uniform, with locations at higher disturbance characterized by slower accrual than locations at lower disturbance (Fig. 2).

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Changes In Turbulent-Stress Profiles In Response To Increasing Bed Roughness: Implications For Sediment Transport In High Gradient Streams

Anonymous — Thu, 23 Aug 2018 17:00:36 +0000

Changes In Turbulent-Stress Profiles In Response To Increasing Bed Roughness: Implications For Sediment Transport In High Gradient Streams Anonymous (not verified) Thu, 08/23/2018 - 11:00 John Pitlick

Pitlick, John ¹ ; , GEOG 5100 students ² ; Nelson, Jonathan ³

¹ University of Colorado
² University of Colorado
³ US Geological Survey

The bed roughness in headwater streams is generally large in comparison to the flow depths required to initiate bed load transport The roughness produced by cobbles and gravels distorts the vertical structure of the flow, to the point where a logarithmic velocity profile may no longer be present. The resulting changes in flow structure make it difficult to estimate near-bed shear stresses for the purposes of defining bed load transport thresholds. In this talk I will present results from a laboratory experiment in which a group of us (students and instructors in GEOG 5100, listed below) varied the concentration of large roughness elements in a 25-cm wide flume, and measured the changes in flow structure using a two-dimensional laser doppler velocimeter (LDV). The measurements show very clearly that, as the concentration of roughness elements increases, there is a noticeable upward shift in the near-bed Reynolds stresses, such that the stress available for transporting the bed sediment is greatly reduced. The experiments shed light on results from a previous study (Mueller et al., 2005) in which we showed that the thresholds for bed load transport in natural gravel-bed channels increase systematically with increasing channel gradient and relative roughness.

Participants: Nate Bradley, Anthony LaGreca, Nora Matell, Scott McCoy, Erich Mueller, Jonathan Nelson, John Pitlick, Catalina Segura

References: Mueller, E. R., J. Pitlick, and J.M. Nelson, 2005, Variation in the reference Shields stress for bed load transport in gravel-bed streams and rivers, Water Resources Research, v. 41, W04006, doi:10.1029/2004WR003692

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Hydrologic Responses Of An Alpine Wetland To Changes In Climate, Front Range, Colorado

Anonymous — Thu, 23 Aug 2018 16:59:54 +0000

Hydrologic Responses Of An Alpine Wetland To Changes In Climate, Front Range, Colorado Anonymous (not verified) Thu, 08/23/2018 - 10:59 Sshley Nielson

Nielson, Ashley ¹ ; Williams, Mark ² ; Caine, Nel ³

¹ INSTAAR,Niwot Ridge LTER,Department of Geography
² INSTAAR,Niwot Ridge LTER,Department of Geography
³ INSTAAR,Niwot Ridge LTER,Department of Geography

Alpine wetlands have been suggested to be among the most sensitive types of wetlands to changes in climate. Yet, little is known about the hydrology of alpine wetlands and how hydrologic processes respond to changes in climate. Here we report on the results of monitoring and tracer studies from May to October from 2003-2007 from a 2-ha wetland in Green Lakes Valley collected as part of the Niwot Ridge LTER program.

We evaluated the vulnerability of hydrologic controls by determining the relationships between outlet discharge, surface and subsurface water levels, residence time, storage, precipitation events, source waters, and flow paths of the wetland. Outlet discharge increased to 650 m3/day on June 27, consistent with snowmelt-dominated source waters. However, peak discharge occurred following a rain event, consistent with a “flashy” hydrograph. Water levels from piezometers show periods of both subsurface discharge and recharge over the season. Results from a LiBr tracer yielded a residence time of ~114 hours, suggesting a significant amount of hydrologic storage within the wetland. Seasonal δ18O values range from -18‰ to -9‰, suggesting changing source waters and flow paths. Initial mixing model results suggest that a nearby rock glacier has a higher contribution during drought. As climate warms and precipitation shifts from snow to rain, alpine wetlands will have increased flashiness and greater contributions from source waters such as rock glaciers and permafrost. Changes in climate that reduce snowfall may reduce subsurface recharge, which may cause potentially irreversible effects to the hydrology of alpine wetlands.

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Evaluating Regional Patterns In Nitrate Sources To Watersheds In National Parks Of The Rocky Mountains Using Nitrate Isotopes

Anonymous — Thu, 23 Aug 2018 16:59:11 +0000

Evaluating Regional Patterns In Nitrate Sources To Watersheds In National Parks Of The Rocky Mountains Using Nitrate Isotopes Anonymous (not verified) Thu, 08/23/2018 - 10:59 Leora Nanus

Nanus, Leora ¹ ; Williams, Mark W ² ; Campbell, Donald H ³ ; Kendall, Carol ⁴; Elliott, Emily M ⁵

¹ �鶹��Ƶ, US Geological Survey
² �鶹��Ƶ
³ US Geological Survey
⁴ US Geological Survey
⁵ University of Pittsburgh

In the Rocky Mountains, there is uncertainty in the source areas and emission types that contribute to nitrate deposition, which can adversely affect sensitive aquatic habitats of high-elevation watersheds. Regional patterns in sources of nitrate deposition were evaluated using nitrate isotopes at sites across five National Parks, including 37 lakes and 7 precipitation sites. Results indicate that nitrate(NO3) concentrations collected from lakes ranged up to 38 microequivalents per liter, d18O(NO3) values ranged from -5.7 to +21.3 permil, and d15N(NO3) values ranged from -6.6 to +4.6 permil. d18O(NO3) in precipitation ranged from +71 to +78 permil. d15N (NO3) in precipitation and lakes overlap; however, precipitation is lighter than lakes ranging from -5.5 to -2.0 permil. d15N(NO3) values are significantly related (r-squared = 0.6, p < 0.05) to wet deposition estimates of inorganic N, sulfate, and acidity, suggesting that the spatial variability of d15N(NO3) over the Rocky Mountains may be related to source areas of these solutes. Regional patterns show that NO3 concentrations and d15N(NO3) values are heaviest in lakes and precipitation from the Southern Rockies and at higher elevations, compared to lower elevations and the Northern Rockies. The correspondence of higher NO3 concentrations and higher d15N(NO3) values in precipitation with higher NO3 and higher d15N(NO3) values in lake waters, suggests that atmospheric deposition of NO3 may affect the amount of NO3 in lakes through either direct (wet deposition) or indirect processes (enhanced nitrification).

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Hydraulic Geometry Of Streams And Rivers In The Northern Rocky Mountains Of Idaho: Correlating Channel Form And Sediment Transport Dynamics

Anonymous — Thu, 23 Aug 2018 16:58:31 +0000

Hydraulic Geometry Of Streams And Rivers In The Northern Rocky Mountains Of Idaho: Correlating Channel Form And Sediment Transport Dynamics Anonymous (not verified) Thu, 08/23/2018 - 10:58 Erich R Mueller

Mueller, Erich R ¹ ; Pitlick, John ²

¹ Department of Geography, University of Colorado
² Department of Geography, University of Colorado

Channel morphology in streams and rivers is a product of the watershed scale flux of sediment and water to the channel network. As a result the scaling of channel geometry downstream through stream networks should reflect the variation in site specific sediment and water supply. Typically hydraulic geometry relations are formulated solely from measurements of water discharge, thus not explicitly addressing the role of sediment transport in dictating channel form. Here we use measurements of sediment transport for 35 streams and rivers in the northern Rocky Mountains of Idaho to explore the downstream scaling of sediment discharge with water discharge and channel width.

Bed load sediment transport data for individual sites suggest that, on average, streams and rivers in Idaho convey roughly 0.01 kg/m/s of sediment at bankfull discharge (Qb) (Figure 1). If this held uniformly, instantaneous sediment discharge at bankfull (Qs) should increase in exact proportion to width. Recent work by Parker et al. (2007) implies that Qs should be roughly proportional to Qb^0.5. Considering that width typically scales as Qb^0.5, the theoretical analysis of Parker et al. (2007) suggests that indeed the sediment discharge should approximately scale with channel width. While a clear generalization, this would imply that adjustments of channel geometry and grain size act to regulate sediment transport so as to convey, on average, the same unit transport rate (qb) everywhere.

Results from Idaho indicate that in fact unit transport rates are increasing downstream such that Qs is proportional to Qb^0.76 (Figure 2). Yet this deviation may reflect the downstream increase in the proportion of sand comprising the bed load. When considering only the non-sand fraction (>2 mm), Qs increases as Qb^0.59. This may suggest that channel width increases to convey the coarse fraction of the bed load at a relatively uniform unit transport rate, whereas sand transport may be controlled more by local supply. As a result, many streams and rivers may be resilient to morphologic change from episodic influxes of fine sediment.

Parker, G., P.R. Wilcock, C. Paola, W.E. Dietich, and J. Pitlick (2007) Physical basis for quasi-universal relations describing bankfull hydraulic geometry of single-thread gravel bed rivers, Journal of Geophysical Research, 112, F04005.

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Sources Of DOM To Alpine Surface Waters: In-Lake Vs. Watershed Production

Anonymous — Thu, 23 Aug 2018 16:57:26 +0000

Sources Of DOM To Alpine Surface Waters: In-Lake Vs. Watershed Production Anonymous (not verified) Thu, 08/23/2018 - 10:57 Matthew Miller

Miller, Matthew ¹ ; McKnight, Diane ² ; Borgnis, Evyan ³

¹ INSTAAR, University of Colorado
² INSTAAR, University of Colorado
³ University of San Francisco

The pulse of dissolved organic matter (DOM) that occurs during snowmelt in mountain catchments is associated with the flushing of DOM from soils and plant leachates. This flushing may be attenuated and/or the chemical character of the DOM may be altered by the presence of wetlands in the catchment. As summer progresses, the DOM in alpine lakes is also derived from autochthonous algal production. We studied the impact of an unusual 3-day mid-summer rainstorm on the biogeochemistry of DOM in an alpine lake in the Green Lakes Valley in the Colorado Front Range. The July 7th-9th, 2006 rain event produced 9 cm of precipitation and increased discharge from the lake 2.5 fold compared to peak snowmelt. Characterization of DOM by fluorescence spectroscopy, PARAFAC, and other methods shows that immediately following the rain event, the DOM fluorescence characteristics were reset to values similar to those observed during snowmelt. Then, in response to increased primary productivity, the DOM fluorescence indicated an increasing microbial contribution and a progressively more oxidized state of the fulvic acid quinones. Analyses of samples collected from an upstream wetland indicate that the wetland acts as a source of terrestrially derived reduced DOM throughout the season. Lake modeling results provide a quantitative measure of the relative contribution of in-lake and watershed derived DOM over the course of the growing season and attribute these sources to hydrologic and biological changes in the catchment.

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The Biogeochemistry Of A Smelly Lake: Little Gaynor Lake, Colorado

Anonymous — Thu, 23 Aug 2018 16:56:36 +0000

The Biogeochemistry Of A Smelly Lake: Little Gaynor Lake, Colorado Anonymous (not verified) Thu, 08/23/2018 - 10:56 James H McCutchan Jr.

McCutchan, Jr., James H ¹ ; Lewis, Jr., William M ² ; Blankenship, Ariann L ³ ; Oppold, Mary ⁴

¹ University of Colorado
² University of Colorado
³ University of Colorado
⁴ University of Colorado

Little Gaynor Lake is a small endorheic basin between Niwot and Longmont, Colorado. The lake supports high rates of phytoplankton production and, at times, also the production of hydrogen sulfide. Since June 2007, we have recorded hourly changes in water temperature at multiple depths near the middle of the lake. We also have sampled the lake bi-weekly for physical, chemical, and biological parameters, including profiles of temperature, specific conductance, dissolved oxygen, pH, and irradiance, analyses of solute concentrations, and analyses of chlorophyll-a and phytoplankton species composition. Since our sampling began, anoxia developed and hydrogen sulfide accumulated in the water column during periods of thermal stratification, which occurred under ice cover and for brief periods during summer. Shallow lakes are generally more productive than deep lakes and nutrient concentrations were high throughout the study, but Little Gaynor Lake supports chlorophyll concentrations that are among the highest recorded for any lake. Total Chlorophyll a in the water column approached 2000 mg/m2, which is well beyond the theoretical limit dictated by self shading. These exceptional chlorophyll values can be explained, however, by high concentrations of dissolved organic matter in Little Gaynor Lake and the potential for heterotrophic growth in Anabaenopsis elenkinii, the dominant component of the phytoplankton community.

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Source And Fate Of Thermal And Non-Thermal Solutes In The Gibbon River, Yellowstone National Park, USA

Anonymous — Thu, 23 Aug 2018 16:55:28 +0000

Source And Fate Of Thermal And Non-Thermal Solutes In The Gibbon River, Yellowstone National Park, USA Anonymous (not verified) Thu, 08/23/2018 - 10:55 R. Blaine McCleskey

McCleskey, R. Blaine ¹ ; Nordstrom, D. Kirk ² ; Ball, James W. ³

¹ U.S. Geological Survey / University of Colorado
² U.S. Geological Survey
³ U.S. Geological Survey

The Gibbon R. flows by Norris Geyser Basin, Gibbon Geyser Basin, and Chocolate Pots before it joins with the Firehole R. to form the Madison R. The purpose of this study was to quantify thermal and non-thermal chemical inputs and attenuation in the Gibbon R. Synoptic water samples and discharge measurements were obtained from the Gibbon R. and its major tributaries under low-flow conditions. The pH of the Gibbon R. ranged from 6.9 to 7.2, the specific conductance ranged from 120 to 430 μS/cm, and the discharge ranged from 1.3 to 2.5 m³/s. Tantalus Cr., the largest drainage in Norris Geyser Basin, contributes the largest single load of Al, As, B, Cl, Fe, Li, Na, SiO₂ and SO₄ to the Gibbon R. No solutes appear to be attenuated in the Gibbon R. However, Fe is oxidized but does not sorb or deposit and the dissolved Hg load decreases where the total Fe load increases suggesting Hg sorption onto iron hydroxide particles. All solute loads near Norris Geyser Basin are accounted for by inflows except Hg, whose source appears to be from a nearby wetland west of Norris Geyser Basin.

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