2014

Nile Hydrology And Ethiopian Dams, Great Ethiopian Renaissance Dam As A Case Study

Anonymous — Mon, 13 Aug 2018 19:31:18 +0000

Nile Hydrology And Ethiopian Dams, Great Ethiopian Renaissance Dam As A Case Study Anonymous (not verified) Mon, 08/13/2018 - 13:31 Seleshi Yilma

Yilma, Seleshi ¹

¹ Ethiopian Institute of Water Resources, Addis Ababa Univesrity

Ethiopia’s contribution to the Nile River is about 85% of average annual flow of 84 Billion m3 at the High Aswan Dam. Ideal water storage gorges are located in Ethiopia which can generate clean energy and lead to significant flood regulation and overall long-term water saving due to reduced evaporation for all riparian countries. Great Ethiopian Renaissance Dam (GERD) with gross storage capacity of 74 BCM (and year to year varying live storage of 25 BCM) generates clean energy of 15,860 GWh/year benefiting to all riparian countries This paper presents key highlights of the Great Ethiopian Renaissance Hydropower Dam and impacts of GERD to Ethiopia, Sudan and Egypt and for the regions as a whole in the light of Climate Change scenarios based on various river basin simulations studies conducted in the Nile basin.

AAU,2013, Eastern Nile System Modeling. Draft Research Report, EIWR Addis Ababa University.
SUTCLIFFE, J.V. and PARKS, Y.P., 1999, Hydrology of the Nile. Wallingford: International Association of Hydrological Sciences.
ENTRO, 2012, Eastern Nile Planning Model, by Kevin Wheeler P.E. and Steve Setzer P.E.
ENTRO,2012, Eastern Nile System Modelling. Development of the Eastern Nile Water Simulation Model, Main Report Draft, Deltares.
World Bank, 2008, Opportunities for Cooperative Water Resources Development on the Eastern Nile: Risks and Rewards; An Independent Report of the Scoping Study, Team to the Eastern Nile Council of Ministers.

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Using Hydrochemistry Data To Constrain The Role Of Snow And Ice Meltwater In The Hydrology Of Langtang Valley, Nepal

Anonymous — Mon, 13 Aug 2018 19:29:24 +0000

Using Hydrochemistry Data To Constrain The Role Of Snow And Ice Meltwater In The Hydrology Of Langtang Valley, Nepal Anonymous (not verified) Mon, 08/13/2018 - 13:29 Alāna M. Wilson

Wilson, Alana M. ¹ ; Williams, Mark W. ² ; Racoviteanu, Adina ³ ; Pellicciotti, Francesca ⁴ ; Juszak, Inge ⁵ ; Kayastha, Rijan B. ⁶

¹ Department of Geography and Institute of Arctic and Alpine Research, �鶹��Ƶ
² Department of Geography and Institute of Arctic and Alpine Research, �鶹��Ƶ
³ Laboratoire de Glaciologie et Géophysique de l’Environnement (LGGE), France
⁴ Swiss Federal Institute of Technology (ETH) Zürich, Switzerland
⁵ University of Zürich (UZH), Switzerland
⁶ Kathmandu University, Nepal

Mountains play an invaluable role in regulating hydrologic resources that downstream communities depend on. As our climate changes, it is essential to evaluate the vulnerability of the high-elevation water cycle. An improved understanding of where the water in our rivers comes from is required before we can anticipate changes and devise adaptation measures. In the context of climate change, hydrograph separation methods may provide ways to determine how much streamflow comes from snow and glacier melt versus groundwater and direct precipitation in poorly sampled glacierized catchments in the Himalaya. Understanding hydrograph separation in high-elevation catchments provides insight into how the timing and volume of discharge may change over time.

This work , part of the USAID funded Contribution to High Asia Runoff from Ice and Snow (CHARIS) project, uses geochemical and isotopic data from surface water and precipitation samples collected in the Langtang Valley of Nepal to estimate contributions of meltwater to discharge. Results presented include a comparison of chemistry data from unique end member sources that contribute to streamflow. Additionally a suite of multiple-component (3+) End Member Mixing Analyses (EMMA) using the hydrochemistry data were conducted to test the plausibility of results. Variability in results depending on input suggests that the accuracy of different mixing model methods must be more closely examined before confidently comparing them to results from other types of models. We thus provide an evaluation of different hydrochemistry approaches to hydrograph separation in the Langtang River Basin.

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The National Ecological Observatory Network: An Update On Construction Progress And Introduction To The STReams Experimental Observatory Network (STREON)

Anonymous — Mon, 13 Aug 2018 19:28:26 +0000

The National Ecological Observatory Network: An Update On Construction Progress And Introduction To The STReams Experimental Observatory Network (STREON) Anonymous (not verified) Mon, 08/13/2018 - 13:28 Ryan Utz

Utz, Ryan ¹

¹ NEON, Inc.

The National Ecological Observatory Network (NEON) is a major research facility funded by the National Science Foundation to enable continental-scale ecological research. NEON will collect hundreds of standardized, quality-controlled data products in sites spanning North America, from the Arctic to Puerto Rico. All data generated by NEON will be entirely open-access. Sensor arrays associated with NEON atmospheric towers, soil pits, and aquatic sites will produce terabytes of integrated hydrologic data per year. Several sites in the NEON network have come online and begun generating data since the construction phase began, including one site in the Colorado plains. NEON also intends to serve as a platform for continental-scale ecological experimentation, and the first among such efforts to be implemented is STREON, the STReams Experimental Observatory Network. STREON will involve two experimental treatments in ten wadable NEON stream sites: 1) the probable limiting nutrient (nitrogen or phosphorus) will be enriched by five times ambient concentrations and 2) large-bodied consumers such as fish or crayfish will be excluded from patches of benthic habitat to determine how their presence structures ecological processes such as primary production and respiration. All 200+ data products collected in NEON aquatic sites will be collected in the control and nutrient-enriched reaches of STREON sites. Additionally, benthic metabolism, biological assemblages, and stable isotopes will be measured in sediment baskets incubated in closed, recirculating chambers. STREON equipment may be used by external researchers when not needed for routine operations.

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Drier Soils In A Warming World? Examining The Relationship Between Soil-Water Stress And Snow Persistence In The Mountain West

Anonymous — Mon, 13 Aug 2018 19:27:32 +0000

Drier Soils In A Warming World? Examining The Relationship Between Soil-Water Stress And Snow Persistence In The Mountain West Anonymous (not verified) Mon, 08/13/2018 - 13:27 Brooke E Stamper

Stamper, Brooke E ¹ ; Harpold, Adrian ² ; Molotch, Noah ³

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

The Western U.S. is heavily reliant on snowmelt for water used by humans and ecosystem services. Regional warming is expected to reduce snowpacks and cause faster and earlier snowmelts. The ecological and hydrological consequences of these changes to snowmelt are not well understood due to the large variability in soil properties, snowmelt timing, and post-snowmelt rainfall. In this study we employ a dataset utilizing stations where co-existing measurements of snowpack, precipitation, soil moisture, and soil properties exist to ask: “When and where do smaller and/or earlier snowmelts lead to increased soil water stress?” Precipitation and soil moisture information was gathered from 48 stations that were part of Natural Resources Conservation Center (NRCS) snow telemetry (SNOTEL) and the Soil Climate Analysis Network (SCAN). In addition, the National Cooperative Soil Survey (NCSS) was used to estimate soil properties at multiple soil horizons. In order to quantify soil-water stress in the top 20 cm, the number of growing-season days below wilting point was analyzed at soil horizons of 5cm, 10cm, and 20cm depth. Precipitation was summed for the winter and post-snowmelt season as well as, maximum annual snow water equivalent, and day of snow disappearance. Focusing in the Northwest U.S., preliminary results found that the timing of snow disappearance was a stronger predictor of the duration of water stress (defined as soil moisture below wilting point) than annual or seasonal precipitation. Surprisingly, we see little direct control of post-snowmelt rainfall on reducing growing-season water stress. This does not bode well for continued changes to earlier snowmelt and larger more intense summer rainfall in much of the Western U.S. It is important to understand soil water availability under a warming climate in order to manage and mitigate the impacts on water resources for both humans and ecosystems.

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Temperature And Velocity Profiles Inferred By Thermal Flowline Modeling For High Elevation Regions Of The Greenland Ice Sheet

Anonymous — Mon, 13 Aug 2018 19:26:34 +0000

Temperature And Velocity Profiles Inferred By Thermal Flowline Modeling For High Elevation Regions Of The Greenland Ice Sheet Anonymous (not verified) Mon, 08/13/2018 - 13:26 Aleah Sommers

Sommers, Aleah N ¹ ; Rajaram, Harihar ² ; Colgan, William T ³

¹ University of Colorado at Boulder, Department of Civil, Environmental, and Architectural Engineering
² University of Colorado at Boulder, Department of Civil, Environmental, and Architectural Engineering
³ Geological Survey of Denmark and Greenland

Rising sea level due to climate change is a significant global concern. Many coastal countries will incur dramatic costs as vital infrastructure is threatened, and small island nations are already being inundated. A large component of sea-level rise is due to the transfer of terrestrial ice from glaciers and ice sheets into the ocean. Since 1990, numerous outlet glaciers on the west coast of Greenland have displayed dramatic accelerations and frontal retreats, yielding substantial changes in ice geometry on the scale of decades or years, rather than centuries or millennia (Joughin et al. 2010). Yet other glaciers within the same geographic region have accelerated less rapidly or even decelerated over the same period (McFadden et al. 2011), and the mechanisms driving this heterogeneous response are poorly quantified.

Most recent changes in the surface mass balance and ice dynamics of the Greenland ice sheet have been restricted to elevations below 2,000m. Substantial computational efficiency can be gained by limiting numerical modeling efforts to this lower elevation periphery, where changes in ice sheet form and flow are most pronounced, rather than modeling the entire ice sheet from the main divide to the margin. Accurately modeling the lower elevations with this approach is dependent on prescribing accurate velocity and temperature profiles at the upstream boundary. The Program for Arctic Regional Climate Assessment (PARCA) provides reliable surface velocity data at 161 locations approximately circumscribing the 2,000m elevation contour of the Greenland ice sheet (Thomas et al. 2001), and the Ice2Sea project improved estimates (and constrained uncertainty) of ice thickness at the PARCA stake locations. Without corresponding velocity and temperature profiles, however, these data alone are insufficient to serve as upstream boundary conditions for lower elevation thermo-mechanical modeling.

Using a two-dimensional, enthalpy-based thermal flowline model, we generate velocity and temperature profiles across the ice sheet depth at the PARCA stake locations. While prescribing ice surface and bedrock elevation, observed surface velocities at the stake locations and the ice discharge calculated from surface mass balance serve as modeling targets. We employ an iterative procedure between mechanical and thermal calculations; ice velocities found by solving the momentum equation (via the Shallow Ice Approximation, which is valid for these high-elevation domains) inform the energy equation to solve for temperature and liquid water content, which then inform the velocity calculations, and so on until convergence.

Preliminary results suggest that observed surface velocities in some regions of Greenland can only be reproduced with a temperate bed at high elevations (in agreement with Aschwanden et al. 2012), and also indicate that model results are sensitive to other factors, such as interpolation and smoothing of ice surface elevation data.

Aschwanden, A., E. Bueler, C. Khroulev, and H. Blatter, 2012, An enthalpy formulation for glaciers and ice sheets, J. Glaciol.
Joughin, I., B. Smith, I. Howat, T. Moon, and T. Scambos, 2010, Greenland Flow Variability from Ice-Sheet-Wide Velocity Mapping. J. Glaciol.
McFadden, E.M., I.M. Howat, I. Joughin, B.E. Smith, and Y. Ahn, 2011, Changes in the dynamics of marine terminating outlet glaciers in west Greenland (2000-2009),J.Geophys. Res.
Thomas, R., B. Csatho, C. Davis, C. Kim, W. Krabill, S. Manizade, J. McConnell, and J. Sonntag, 2001, Mass balance of higher-elevation parts of the Greenland Ice Sheet, J. Geophys. Res. – Atmospheres

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The Importance Of Instantaneous Flow Structures To Total Mixing And Reaction Of Gamete Filaments In Broadcast Spawning

Anonymous — Mon, 13 Aug 2018 19:16:55 +0000

The Importance Of Instantaneous Flow Structures To Total Mixing And Reaction Of Gamete Filaments In Broadcast Spawning Anonymous (not verified) Mon, 08/13/2018 - 13:16 Farrokh Shoaei

Shoaei, Farrokh ¹ ; Soltys, Michael A. ² ; Crimaldi, John P. ³

¹ �鶹��Ƶ
² �鶹��Ƶ
³ �鶹��Ƶ

One of the most common methods of reproduction in the sea is broadcast spawning, wherein marine invertebrates release eggs and sperm into the ambient flow and fertilization occurs externally. Gamete coalescence at large scales is dominated by fluid stirring, and may be influenced by the presence of flow obstructions (e.g., coral heads, bed topography). The effect of the turbulent wake behind a round obstacle on the second-order reaction between two initially distant scalars has been investigated by series of planar laser-induced fluorescence experiments. The scalars are released continuously, and are separated from each other by a lateral distance that initially impedes the reaction. The direct effect of the wake on mixing enhancement is determined by comparing segregation parameter for cases with and without the cylinder obstruction. A decomposition of the total reaction into mean and instantaneous contributions reveals that as turbulence bring filaments together mean processes underestimate fertilization as filaments coalesce in concentrations orders of magnitudes above the mean concentrations. This study shows that the presence of an obstacle in spawning regions may substantially raise the contribution of instantaneous processes up to 65%.

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Combining Remotely-Sensed Snow Water Equivalent With In-Situ Measurements To Produce A Real-Time SWE Product

Anonymous — Mon, 13 Aug 2018 19:15:05 +0000

Combining Remotely-Sensed Snow Water Equivalent With In-Situ Measurements To Produce A Real-Time SWE Product Anonymous (not verified) Mon, 08/13/2018 - 13:15 Dominik Schneider

Schneider, Dominik ¹ ; Molotch, Noah P. ²

¹ INSTAAR
² INSTAAR

Snowmelt is the primary water source in the Western United States and mountainous regions globally. Forecasts of streamflow and water supply rely heavily on snow measurements from sparse observation networks that may not provide adequate information during abnormal climatic conditions. To address this issue we developed a real-time spatially distributed snow water equivalent (SWE) product for the Upper Colorado River Basin that merges previous years SWE patterns derived from a reconstruction model, with interpolations of real-time situ measurements. The approach uses a multiple linear regression to model SWE in which physiography and reconstructed SWE are treated as independent variables and observed SNOTEL SWE the dependent variable. Using a drop-1 approach, the years 2000 - 2011 (Mar 1, Apr 1, and May 1) consistently find reconstructed SWE to be a significant predictor and the explained variability of the model is improved between 0.1 and 0.5 (mean= 0.23) compared to a model just based on physiographics. Independent validation in the Front Range, CO produces mean absolute errors (MAE) between 0.13 and 0.18 m, with significant improvements between 0.03 and 0.09 m over both reconstructed SWE and physiographic SWE (p<0.05). Geostatistical interpolation techniques (IDW, kriging) are used to blend the regression residuals onto the regression surface to incorporate regional effects within the modeling domain. However, MAE is only marginally reduced (~0.01) with blending. Improved analysis of past SWE distribution can provide valuable information for modeling efforts to predict, e.g. hydrologic impacts due to climate change and disturbances. Future validation is planned in additional locations within the modeling domain and a real-time product is in development that uses this ensemble of past patterns of SWE to estimate SWE in the current water year.

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Fate And Transport Of Hydraulic Fracturing Fluid Organic Compounds

Anonymous — Mon, 13 Aug 2018 19:13:58 +0000

Fate And Transport Of Hydraulic Fracturing Fluid Organic Compounds Anonymous (not verified) Mon, 08/13/2018 - 13:13 Joe Ryan

Ryan, Joe ¹

¹ University of Colorado, Boulder

Abstract to be added later

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An Isotopic Perspective On Water And Carbon Sources In Complex Geochemical Settings Of The Appalachians

Anonymous — Mon, 13 Aug 2018 19:13:02 +0000

An Isotopic Perspective On Water And Carbon Sources In Complex Geochemical Settings Of The Appalachians Anonymous (not verified) Mon, 08/13/2018 - 13:13 Andrea L. Sack

Sack, Andrea L. ¹

¹ Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO; Geology and Geography, West Virginia University, Morgantown, WV

Understanding sources of water and carbon are important for tracking recharge sources as well as assessing any changes in water quality associated with shale gas drilling and/or coal mining in the Appalachian region of the United States. Environmental stable isotopes have become an increasingly useful tool for determining sources and cycling of water, carbon, nutrients and other trace elements. The variations in water-rock interactions, recharge sources, recharge pathways, and age can impart unique isotopic signatures to different water sources. The main objectives of this study were to use stable isotopes of water (d18O H2O and d2H H2O) and DIC (d13C DIC) to delineate sources of water and carbon in natural springs, coal mine discharges and brines co-produced during Marcellus Shale gas drilling in Appalachia. Preliminary data indicates that stable isotopes can be used in conjunction with routine geochemistry to understand sources of carbon and water at each site.

Additionally, gas and water samples were collected from gas producing wells in the region from Upper Devonian sands and Middle Devonian Marcellus Shale in southwestern Pennsylvania and north-central West Virginia to asses the water quality and any hydrologic connections during Marcellus Shale drilling. Initial conclusions suggest that the oxygen and hydrogen isotope composition of water, carbon isotope composition of dissolved inorganic carbon, and carbon and hydrogen isotope compositions of methane in Upper Devonian sands and Marcellus Shale are very different compared with shallow groundwater aquifers, coal-mine waters, and stream waters of the region. Therefore, spatiotemporal stable isotope monitoring of the different sources of water before, during, and after hydraulic fracturing can be used to identify migrations of fluids and gas from deep formations that are coincident with shale gas drilling.

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Increasing ARD And Rare Earth Metal Concentrations In An Alpine Watershed

Anonymous — Mon, 13 Aug 2018 19:11:55 +0000

Increasing ARD And Rare Earth Metal Concentrations In An Alpine Watershed Anonymous (not verified) Mon, 08/13/2018 - 13:11 Garrett P Rue

Rue, Garrett P ¹ ; McKnight, Diane M ² ; Crouch, Caitlin ³

¹ INSTAAR, ENVS, University of Colordo-Boulder
² INSTAAR, ENVS, CAEE, University of Colorado-Boulder
³ Integral Consulting

The coupled environmental impact of acid rock (ARD) and acid mine drainage (AMD) is a problem facing many waterways across the Rocky Mountains and throughout the world, particularly in areas of historic mining. Here we examine the Snake River watershed, located near the former mining boomtown of Montezuma, Colorado. Over the last three decades, researchers for numerous government agencies, the Institute of Arctic and Alpine Research, and graduate students from the University of Colorado have monitored changes in Snake River water chemistry and metal contamination present in its tributary streams.

The Snake River watershed represents a unique water quality challenge because its headwaters are impacted by ARD, and downstream tributary inflows compound this with AMD. These acidic, metal-rich inflows create an acutely toxic environment for fish and most aquatic organisms. Over the last 10 years, more frequent drought conditions and earlier occurrence of peak spring snowmelt have further reduced water quality during low-flow conditions. In addition to lower flows, changes in water chemistry have been driven by increased weathering rates of exposed sulfide minerals, resulting in decreased pH. The additional acid production has caused dissolution of metals from the host rock and enrichment of the stream with these solutes, which are mobilized greater distances down the reach.

Iron is the predominant metal present in the upper Snake River, but upon mixing with pristine neutral inflows precipitates as iron oxides. Zinc, however, is less affected by this increase in pH and remains dissolved well downstream of the ARD and AMD sources. Of particular concern is that stream chemistry data has shown a four-fold increase in zinc concentrations in the last 10 years, with a transition from a steady linear increase over a previous 20-year record to that of an exponential trend. More recent study of the upper Snake River and its contributing streams led to the discovery of rare earth metals in high concentrations. For example, neodymium is present in one particular tributary in levels as high as 120 ug/L. Retesting of archived samples going back as far as the 1990s has confirmed a continued presence, proving an intriguing issue for further study. The hydrologic and biogeochemical changes observed in this watershed may have important implications for mitigation and/or remediation of mine sites.

Crouch, CM., D.M. McKnight, and A.S. Todd. 2013 Quantifying sources of increasing zinc from acid rock drainage in an alpine catchment under a changing hydrologic regime. Hydrological Processes 27(5):721-733
McKnight, D.M., B.A. Kimball, and K.E. Bencala. 1988. Iron photoreduction and oxidation in an acidic mountain stream. Science 240:637-640
Todd, A.S., A.H. Manning, P.L. Verplank, C.M. Crouch, D.M. McKnight, and R. Dunham. 2012. Climate-change-driven deterioration of water quality in a mineralized watershed.

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