2017

Streamflow Simulations Under Future Climate Scenarios In The Boulder Creek Watershed, Colorado

Anonymous — Fri, 03 Aug 2018 17:02:52 +0000

Streamflow Simulations Under Future Climate Scenarios In The Boulder Creek Watershed, Colorado Anonymous (not verified) Fri, 08/03/2018 - 11:02 Qinghuan Zhang

Zhang, Qinghuan ¹ ; Williams, Mark ² ; Livneh, Ben ³

¹ University of Colorado Boulder
² University of Colorado Boulder
³ University of Colorado Boulder

Mountainous areas have complex geological features and climatic variability, which limit our ability to simulate and predict hydrologic processes in these areas, especially under the context of a changing climate. Hydrologic models can improve our understanding of land surface water and energy budgets in these regions. In this study, a distributed physically-based hydrologic model is applied to the Boulder Creek Watershed, USA to study streamflow conditions under climatic scenario RCP 8.5. Most studies focus on a broad scale, whereas we apply the hydrologic model at two spatial resolutions to the regional watershed by using multiple objective functions to adjust the model. Model parameters were first identified at 1/8th and 1/16th degree spatial resolutions using historical streamflow data. Climatic forcing data using two statistical downscaling methods from eighteen CMIP5 GCMs are applied to the study area. It shows that the multivariate adaptive constructed analogues (MACA) is more proper than the bias-corrected and statistical disaggregation (BCSD) method in the study area. The two methods show that daily minimum and maximum temperature will increase from all the models, while daily precipitation may increase or decrease depending on different models. Using the MACA dataset, average annual precipitation will change by -1.2%~4.5%. Daily maximum temperature will increase by 1~5.7 °C. Daily minimum temperature will increase by 1.7~6.1 ºC, compared to baseline values. Using the BCSD dataset, average annual precipitation will change by -3.7%~5.3%. Daily maximum temperature will increase 1.4~6.5 ºC, while daily minimum temperature will increase 1.5~6 ºC. Average annual streamflow will decrease by 16%~33% using the MACA dataset, and decrease by 14.6% using the BCSD dataset. Understanding streamflow conditions under future climate scenarios is helpful for water resources management.

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Increased Stream Temperature In Response To Extreme Precipitation Events

Anonymous — Fri, 03 Aug 2018 17:01:38 +0000

Increased Stream Temperature In Response To Extreme Precipitation Events Anonymous (not verified) Fri, 08/03/2018 - 11:01 Colleen E Wilson

Wilson, Colleen E ¹ ; Gooseff, Michael N ²

¹ INSTAAR
² INSTAAR

Aquatic ecosystem temperature regulation is essential to the survival of riverine fish species restricted to limited water temperature ranges. Dissolved oxygen levels, similarly necessary to fish health, are decreased by rising temperatures, as warmer waters can hold less oxygen than colder waters. Climate change projections forecast increased precipitation intensities, a trend that has already been observed in the past decade. Though extreme events are becoming more common, the stream temperature response to high-intensity rainfall is not yet completely understood. Precipitation and stream temperature records from gages in the Upper Midwestern United States were analyzed to determine whether there exists a positive relationship between high-intensity rainfall and stream temperature response. This region was chosen for its already observed trends in increasing precipitation intensity, and rural gages were used in order to minimize the effect of impervious surfaces on runoff amounts and temperature. Days with recorded precipitation were divided by an intensity threshold and classified as either high-intensity or low-intensity days. While the effects of rain events on temperature are variable, increases in stream temperature in response to high-intensity rainfall were observed. For some basins, daily maximum rates of stream temperature increase were, on average, greater for higher intensity events. Similarly, the average daily stream temperature range was higher in streams on days of high-intensity precipitation, compared to days of low-intensity events. Understanding the effect of increasing precipitation intensity in conjunction with rising air temperatures will provide insight into the future of aquatic ecosystems and their adaptation to climate change.

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Using Ground Penetrating Radar To Assess The Variability Of Snow Water Equivalent And Melt In A Mixed Canopy Forest, Northern Colorado

Anonymous — Fri, 03 Aug 2018 17:00:17 +0000

Using Ground Penetrating Radar To Assess The Variability Of Snow Water Equivalent And Melt In A Mixed Canopy Forest, Northern Colorado Anonymous (not verified) Fri, 08/03/2018 - 11:00 Ryan Webb

Webb, Ryan ¹

¹ Institute of Arctic and Alpine Research, University of Colorado

Snow is an important environmental variable in headwater systems that controls hydrological processes such as streamflow, groundwater recharge, and evapotranspiration. These processes will be affected by both the amount of snow available for melt and the rate at which it melts. Snow water equivalent (SWE) and snowmelt are known to vary within complex subalpine terrain due to terrain and canopy influences. This study assesses this variability during the melt season using ground penetrating radar to survey multiple plots in northwestern Colorado near a snow telemetry (SNOTEL) station. The plots include south and flat aspect slopes with open, coniferous (subalpine fir, Abies lasiocarpa and engelman spruce, Picea engelmanii), and deciduous (aspen, populous tremuooides) canopy cover. Results show the high variability for both SWE and loss of SWE during spring snowmelt in 2014. The coefficient of variation for SWE tended to increase with time during snowmelt whereas loss of SWE remained similar. Correlation lengths for SWE were between two and five meters with melt having correlation lengths between two and four meters. The SNOTEL station regularly measured higher SWE values relative to the survey plots but was able to reasonably capture the overall mean loss of SWE during melt. Capturing the variability of processes during spring snowmelt determines appropriate scales of modeling and data collection for future studies. GPR methods can improve future investigations with the advantage of non-destructive sampling and the ability to estimate depth, density, and SWE beyond point-scale measurements.

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Multi-Objective Optimization Using Water Treatment Plant Simulation Model For Wildfire Conditions

Anonymous — Fri, 03 Aug 2018 16:59:11 +0000

Multi-Objective Optimization Using Water Treatment Plant Simulation Model For Wildfire Conditions Anonymous (not verified) Fri, 08/03/2018 - 10:59 James P Vernon

Vernon, James P ¹ ; Raseman, William J ² ; Kasprzyk, Joseph R ³ ; Rosario-Ortiz, Fernando ⁴ ; Hohner, Amanda K ⁵ ; Summers, R S ⁶

¹ University of Colorado Boulder
² University of Colorado Boulder
³ University of Colorado Boulder
⁴ University of Colorado Boulder
⁵ University of Colorado Boulder
⁶ University of Colorado Boulder

Forested watersheds contain high quality, high quantity source waters that approximately 180 million Americans rely on for their drinking water supply. These forested water supplies are vulnerable to water quality changes due to wildfires, which tend to increase levels of suspended sediment, nutrients, organic carbon, and heavy metals in source waters, and lead to subsequent health risks to consumers. Based on climatic changes and forest fuel buildup due to forest management practices, areas of the United States prone to wildfires may experience an increase in wildfire frequency and severity. At present, water treatment plant (WTP) managers have few tools to predict how their source water quality will be affected by a wildfire and whether their current WTP can handle these variations from normal operations. In this research, we explore how a multi-objective evolutionary algorithm (MOEA) can be used in conjunction with the USEPA Water Treatment Plant Model to suggest robust management strategies for WTPs and predict changes in finished drinking water quality due to wildfire events. To represent wildfire conditions, we use water quality data from the 2012 High Park fire in Fort Collins, CO. Based on these data, we perform simulations to determine the sensitivity of management practices produced by the MOEA to variations in wildfire conditions. In future work, the impact of other extreme events, such as flooding and drought, will also be considered.

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The Collision Of 19th Century Water Law, 20th Century Water Infrastructure And 21st Century Climate Change: Navigating The New Realities

Anonymous — Fri, 03 Aug 2018 16:57:41 +0000

The Collision Of 19th Century Water Law, 20th Century Water Infrastructure And 21st Century Climate Change: Navigating The New Realities Anonymous (not verified) Fri, 08/03/2018 - 10:57 Brad Udall

Udall, Brad ¹

¹ Colorado Water Institute – Colorado State University

Water in the Western US is governed by water law derived from the early gold miners in the mid 19th century and is controlled by massive infrastructure built in the 20th century. Population growth and a vastly different hydrologic cycle due to climate change will stress both the legal and built environments. This talk will discuss how climate change will affect the water cycle including changes we are already experiencing, the limitations of existing water law and possible modifications, and the need to manage our infrastructure in new ways.

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Improving Diatom Enumeration Methods For Use In Predictive Bioassessment Models

Anonymous — Fri, 03 Aug 2018 16:56:24 +0000

Improving Diatom Enumeration Methods For Use In Predictive Bioassessment Models Anonymous (not verified) Fri, 08/03/2018 - 10:56 Meredith A Tyree

Tyree, Meredith A ¹ ; Bishop, Ian W ² ; Spaulding, Sarah A ³

¹ Institute of Arctic and Alpine Research (INSTAAR), University of Colorado Boulder
² Institute of Arctic and Alpine Research (INSTAAR), University of Colorado Boulder
³ United States Geological Survey, University of Colorado Boulder

An emerging trend in bioassessment is the application of models that predict species assemblages expected at sites in the absence of human impact. These observed/expected (O/E) models, however, have had limited success when applied to diatoms, perhaps because the models are not well-suited to the method traditionally used to characterize diatom communities (Cao et al. 2007). The traditional enumeration method prescribes that all valves be counted on a transect until a 600-valve count is reached. Dominance by one or two taxa is common in diatom samples and could be problematic for O/E models using this counting method, particularly because taxa that occur in less than 5% of sites are excluded from analysis (Zuellig et al. 2012). To address this problem, we analyzed the nature of diatom communities in reference sites and used our results to develop an alternative counting method that better consistently captures rare species. In our alternative method, the first 100 valves on a transect are enumerated, then the slide is scanned in non-overlapping transects for one hour, recording taxa only as presence/absence. We will next compare O/E models built on traditional counts to models built on alternative counts. If successful, our alternative method could improve measurements of stream health while expediting analyses and saving money.

Cao, Y., C. P. Hawkins, J. Olson, and M. A. Kosterman, 2007, Modeling natural environmental gradients improves the accuracy and precision of diatom-based indicators: Journal of the North American Benthological Society v. 26, p.566–585.
Zuellig, R. E., D. M. Carlisle, M. R. Meador, and M. Potapova, 2012, Variance partitioning of stream diatom, fish, and invertebrate indicators of biological condition: Freshwater Science v. 31, p.182–190.

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Temporal Signatures Of Hyporheic Exchange And Stream Metabolism In Glacial Meltwater Streams, Antarctica

Anonymous — Fri, 03 Aug 2018 16:55:07 +0000

Temporal Signatures Of Hyporheic Exchange And Stream Metabolism In Glacial Meltwater Streams, Antarctica Anonymous (not verified) Fri, 08/03/2018 - 10:55 Christa L. Torrens

Torrens, Christa L. ¹ ; Gooseff, Michael N. ²

¹ INSTAAR - University of Colorado, Boulder
² INSTAAR - University of Colorado, Boulder

Glacial meltwater streams in the McMurdo Dry Valleys [MDV], Antarctica flow 4-12 weeks per year during the austral summer. Instream algal mats provide most of the primary production; there are no vascular plants. Extensive hyporheic zones host microbial communities, which may provide significant heterotrophic respiration. During the austral summer, there is continuous daylight and potentially continuous photosynthesis. Temperature, streamflow [Q] and specific electrical conductance [EC] all vary on diel timescales. Little is known about interactions between these diel fluxes and whole-stream metabolism in MDV streams.

To examine the temporal patterns of hyporheic exchange and stream metabolism in this system, we measured water temperature, EC, Q, and instream and hyporheic dissolved oxygen [DO] on Von Guerard Stream. Von Guerard is a relatively long MDV stream with a well-developed hyporheic zone and abundant algal mats. EC is a common proxy for hyporheic exchange as meltwater is dilute, and hyporheic water has relatively high EC due to rapid weathering in the hyporheic zone. DO is a proxy for whole-stream metabolic processes: primary productivity adds DO to the system while respiration consumes it.

We expected instream DO to follow diel irradiation patterns, decreasing at “night” when the solar aspect is relatively low. We also expected instream DO and EC to be negatively correlated, as hyporheic exchange would add both dissolved solutes and less-oxygenated water to the stream. However, we found that instream DO levels remained high regardless of solar aspect or EC fluxes; this indicates consistently high primary productivity and relatively low levels of respiration, regardless of hyporheic influx. Hyporheic DO flux patterns are more complex and appear to be more strongly influenced by hyporheic exchange.

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Application Of Elementary Solutions In Groundwater Modeling

Anonymous — Fri, 03 Aug 2018 16:53:36 +0000

Application Of Elementary Solutions In Groundwater Modeling Anonymous (not verified) Fri, 08/03/2018 - 10:53 Otto D.L. Strack

Strack, Otto D.L. ¹

¹ Department of Civil, Environmental, and Geo- Engi- neering, College of Science and Technology, University of Minnesota

Groundwater flow modeling has become increasingly sophisticated as modeling tools have evolved from early computer programs that required elaborate input and produced output in terms of sheets full of numbers. Nowadays, a computer model can be constructed simply by constructing a data set, using a Graphical Information System, running it through an advanced computer program, such as MODFLOW, and combine it with an equally advanced Parameter Estimation Program, e.g., PEST. The result often is an impressive set of graphs.

Although such an approach is very powerful in the hands of an expert, there exists a danger of creating a model that looks impressive, but is unrealistic. We will attempt, in this presentation, to make a case for making use of elementary solutions to groundwater problems. Sometimes, these solutions will, by themselves, answer the question posed, but often they can help in creating an advanced model, as well as ensuring that the advanced model is likely to be realistic.

We will present examples of this idea. Several of these examples answered the question by themselves, and in other cases they were valuable in setting up an advanced model. Finally, we will briefly introduce an approach, called vertically integrated flow modeling, which can help in simplifying models, as well as serving as a tool for testing the complex model.

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Connecting Water Managers, Multiobjective Evolutionary Algorithms, And Multivariate Regression Trees To Support Water Utility Planning On The Front Range

Anonymous — Fri, 03 Aug 2018 16:52:44 +0000

Connecting Water Managers, Multiobjective Evolutionary Algorithms, And Multivariate Regression Trees To Support Water Utility Planning On The Front Range Anonymous (not verified) Fri, 08/03/2018 - 10:52 Rebecca Smith

Smith, Rebecca ¹ ; Kasprzyk, Joseph ²

¹ University of Colorado at Boulder
² University of Colorado at Boulder

In light of the unpredictable effects of climate change and population shifts, responsible resource management will require new types of information and strategies going forward. For water utilities, this means that water supply infrastructure systems must be expanded and/or managed for potential decreases in overall supply, increases in extremes, and a vulnerable environment. Multiobjective Evolutionary Algorithms (MOEAs) are tools that efficiently generate and evaluate planning alternatives to find a large number of portfolios that balance between water utilities’ conflicting performance objectives. Research applications have shown MOEAs to be useful for finding innovative approaches to challenging management problems. However, they have rarely been used in practice and their role in the context of real-world planning has not been fully established.

Our study bridges the gap between research applications of MOEA-assisted optimization and the needs of utilities by collaborating with six Front Range water providers to develop and evaluate results from an MOEA case study. At the second of two practitioner workshops, we engaged with water managers over structured activities and facilitated discussions to create a new understanding of how the tool can both support their current needs and expand their ability to holistically manage the built and natural systems we depend on. This presentation will focus on one result of this collaborative effort- the use of Multivariate Regression Trees (MRTs) to extract valuable information from the many optimized portfolios produced by MOEAs. MRTs can be used to, among other things, reveal subsets of management decisions (out of the many possible options) that lead to good system performance across multiple future scenarios. This type of information would provide a quantitative basis for utilities to establish “low regrets” management strategies.

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Characterizing The Role Of Hyporheic Exchange Processes In Transient Electrical Conductivity-Discharge Relationships Over Multiple Timescales

Anonymous — Fri, 03 Aug 2018 16:51:31 +0000

Characterizing The Role Of Hyporheic Exchange Processes In Transient Electrical Conductivity-Discharge Relationships Over Multiple Timescales Anonymous (not verified) Fri, 08/03/2018 - 10:51 Joel G Singley

Singley, Joel G ¹ ; Wlostowski, Adam N ² ; Bergstrom, Anna J ³ ; Sokol, Erick R ⁴ ; Torrens, Christa L ⁵ ; Jaros, Chris ⁶ ; Wilson, Colleen E ⁷ ; Gooseff, Michael N ⁸

¹ Environmental Studies Program, University of Colorado Boulder
² Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder
³ Department of Geological Sciences, University of Colorado Boulder
⁴ Institute of Arctic and Alpine Research, University of Colorado Boulder
⁵ Environmental Studies Program, University of Colorado Boulder
⁶ Institute of Arctic and Alpine Research, University of Colorado Boulder
⁷ Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder
⁸ Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder

The analysis of concentration-discharge (C-Q) relationships has often been used in an inverse modeling framework to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by catchment complexity, such as a large number of source waters and non-stationarity in their hydrochemical composition. Attempts to overcome these challenges often necessitate ignoring or lumping together potentially important runoff pathways and geochemical sources/sinks. This is especially true of the hyporheic zone because it acts as an integrator of multiple sources and typically lacks a unique hydrochemical signature. Furthermore, these complexities often limit efforts to identify catchment processes responsible for the transience of C-Q hysteresis between discrete hydrological events. To address these challenges, we leverage the hydrologic simplicity and long-term, high frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone and reveal the legacy of mixing processes occurring along the stream. We utilize a novel approach to decompose loops into sub-hysteretic EC-Q dynamics in order to identify individual mechanisms governing hysteretic patterns and transience across a wide range of timescales. From this analysis, we find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability resulting in discrete hysteretic behavior. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily, annual, and interannual timescales and contribute differently to transient hysteresis in short and long streams. The framework we utilize to analyze sub-hysteretic dynamics may be applied more broadly to constrain the processes controlling C-Q transience and aid advancements in understanding the evolution of catchment processes and structure over time.

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