DOCSLIB.ORG

Continental-Scale Isotope Hydrology Scott Aj Sechko

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Continental-Scale Isotope Hydrology Scott Aj Sechko University of New Mexico UNM Digital Repository Earth and Planetary Sciences ETDs Electronic Theses and Dissertations 12-1-2014 Continental-scale isotope hydrology Scott aJ sechko Follow this and additional works at: https://digitalrepository.unm.edu/eps_etds Recommended Citation Jasechko, Scott. C" ontinental-scale isotope hydrology." (2014). https://digitalrepository.unm.edu/eps_etds/40 This Dissertation is brought to you for free and open access by the Electronic Theses and Dissertations at UNM Digital Repository. It has been accepted for inclusion in Earth and Planetary Sciences ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Scott Jasechko Candidate Earth and Planetary Sciences Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: Dr. Zachary D. Sharp , Co-chairperson Dr. Peter J. Fawcett , Co-chairperson Dr. Joseph Galewsky Dr. Juske Horita CONTINENTAL-SCALE ISOTOPE HYDROLOGY by SCOTT ALLAN JASECHKO B.Sc., University of Victoria, 2009 M.Sc. University of Waterloo, 2011 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Earth and Planetary Sciences The University of New Mexico Albuquerque, New Mexico December, 2014 DEDICATION To Jennifer, Gordon, Glenn and Edith – for your love and your encouragement. iii ACKNOWLEDGMENTS I am grateful to Zachary Sharp, Peter Fawcett and Joseph Galewsky for supporting, challenging and guiding me throughout my Ph.D. education. I am thankful for my friends and mentors who continue to grant me the joy of belonging in a community. iv CONTINENTAL-SCALE ISOTOPE HYDROLOGY By Scott Jasechko B.Sc., Physical Geography and Earth and Ocean Sciences, University of Victoria, 2009 M.Sc., Earth and Environmental Sciences, University of Waterloo, 2011 Ph.D., Earth and Planetary Sciences, University of New Mexico, 2014 ABSTRACT Providing sustainable sources of fresh water for a growing population of 7 billion people is one of the grand challenges of the 21st century. This dissertation outlines several applications of isotope hydrology to address four previously unknown questions involving surface- and ground-water resources at regional- to continental-spatial scales over contemporary- to millennial-temporal scales. The four chapters in this dissertation investigate (1) the rate of plant transpiration, (2) the seasonality of groundwater recharge, (3) the climate of the last ice age, and (4) the chemistry of Ugandan waters. (1) Chapter one presents a new global compilation of lake water isotopic data, river isotopic data, stand-level transpiration rates, and water use efficiency measurements, and analyzes the newly synthesized data to show that plant transpiration is the largest water flux from Earth’s continents, exceeding both physical evaporation and continental runoff. (2) Chapter two presents a new global synthesis of rain, snow and groundwater isotopic compositions, and analyzes the paired v precipitation-groundwater dataset to show that the percentage of precipitation that recharges aquifers is at a maximum during the winter (extra-tropics) and wet (tropics) seasons. (3) Chapter three presents a new global compilation of groundwater radiocarbon, tritium, and stable O and H isotopic data, and maps the isotopic shift of meteoric waters since the last ice age. The analysis shows that the majority (~90%) of precipitation during the last ice age had lower 18O/16O and 2H/1H ratios than the modern day, except in some exclusively coastal locations. We also show that current isotope-enabled general circulation models capture some, but not all, spatial variability in ice-age-to-late-Holocene 18O/16O and 2H/1H shifts, providing a new calibration tool that can be used to improve our understanding of glacial climate dynamics. (4) Chapter four presents isotopic and chemical analyses of Ugandan lake, river, rain, and ground water collected during a field expedition led in July of 2013. Analysis of this new dataset reveals new estimates of lake water balances across Uganda. vi TABLE OF CONTENTS DEDICATION .................................................................................................................................................. iii ACKNOWLEDGMENTS ............................................................................................................................... iv ABSTRACT .......................................................................................................................................................... v TABLE OF CONTENTS ............................................................................................................................... vii PREFACE............................................................................................................................................................. 1 CHAPTER 1 — GLOBAL PLANT TRANSPIRATION FLUXES ........................................................ 9 1.1 Abstract ...................................................................................................................................................... 9 1.2 Introduction ............................................................................................................................................... 9 1.3 Dataset and methods .............................................................................................................................. 32 1.4 Results ....................................................................................................................................................... 54 1.5 Discussion ................................................................................................................................................ 61 1.6 References ................................................................................................................................................ 63 CHAPTER 2 — THE SEASONALITY OF GLOBAL GROUNDWATER RECHARGE ............ 83 2.1 Abstract .................................................................................................................................................... 83 2.2 Introduction ............................................................................................................................................. 83 2.3 Dataset and methods .............................................................................................................................. 88 2.4 Results ..................................................................................................................................................... 101 2.5 Discussion .............................................................................................................................................. 106 2.6 References .............................................................................................................................................. 121 CHAPTER 3 — THE ISOTOPIC COMPOSITION OF ICE AGE GROUNDWATERS ........... 142 3.1 Abstract .................................................................................................................................................. 142 3.2 Introduction ........................................................................................................................................... 143 3.3 Dataset and Methods............................................................................................................................ 148 3.4 Results ..................................................................................................................................................... 151 3.5 Discussion .............................................................................................................................................. 164 3.6 References .............................................................................................................................................. 188 CHAPTER 4 — THE ISOTOPE HYDROLOGY OF UGANDA ..................................................... 212 4.1 Abstract .................................................................................................................................................. 212 4.2 Introduction ........................................................................................................................................... 212 4.3 Dataset and methods ............................................................................................................................ 214 4.4 Results ..................................................................................................................................................... 217 4.5 Discussion .............................................................................................................................................. 231 4.6 References .............................................................................................................................................. 241 vii List of Figures 1-1. Schematic of fresh water fluxes ............................................................................................................... 10 1-2. Schematic of plant transpiration .............................................................................................................. 12 1-3. Water yields before and after the clearing of vegetation
Load more

Recommended publications
  • Changes of Water Clarity in Large Lakes and Reservoirs Across China
    Remote Sensing of Environment 247 (2020) 111949 Contents lists available at ScienceDirect Remote Sensing of Environment journal homepage: www.elsevier.com/locate/rse Changes of water clarity in large lakes and reservoirs across China observed T from long-term MODIS ⁎ Shenglei Wanga,b, Junsheng Lib,c, Bing Zhangb,c, , Zhongping Leed, Evangelos Spyrakose, Lian Fengf, Chong Liug, Hongli Zhaoh, Yanhong Wub, Liping Zhug, Liming Jiai, Wei Wana, Fangfang Zhangb, Qian Shenb, Andrew N. Tylere, Xianfeng Zhanga a School of Earth and Space Sciences, Peking University, Beijing, China b Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China c University of Chinese Academy of Sciences, Beijing, China d School for the Environment, University of Massachusetts Boston, Boston, MA, USA e Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, UK f State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, China g Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China h China Institute of Water Resources and Hydropower Research, Beijing, China i Environmental Monitoring Central Station of Heilongjiang Province, Harbin, China ARTICLE INFO ABSTRACT Keywords: Water clarity is a well-established first-order indicator of water quality and has been used globally bywater Secchi disk depth regulators in their monitoring and management programs. Assessments of water clarity in lakes over large Lakes and reservoirs temporal and spatial scales, however, are rare, limiting our understanding of its variability and the driven forces.
    [Show full text]
  • Using Isotopes to Constrain Water Flux and Age Estimates in Snow
    Hydrol. Earth Syst. Sci., 21, 5089–5110, 2017 https://doi.org/10.5194/hess-21-5089-2017 © Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 License. Using isotopes to constrain water flux and age estimates in snow-influenced catchments using the STARR (Spatially distributed Tracer-Aided Rainfall–Runoff) model Pertti Ala-aho1, Doerthe Tetzlaff1, James P. McNamara2, Hjalmar Laudon3, and Chris Soulsby1 1Northern Rivers Institute, School of Geosciences, University of Aberdeen, AB24 3UF, UK 2Department of Geosciences, Boise State University, Boise, ID 83725, USA 3Department of Forest, Ecology and Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden Correspondence to: Pertti Ala-aho ([email protected]) Received: 24 February 2017 – Discussion started: 9 March 2017 Revised: 28 June 2017 – Accepted: 18 August 2017 – Published: 9 October 2017 Abstract. Tracer-aided hydrological models are increasingly water age distributions, which was captured by the model. used to reveal fundamentals of runoff generation processes Our study suggested that snow sublimation fractionation pro- and water travel times in catchments. Modelling studies in- cesses can be important to include in tracer-aided modelling tegrating stable water isotopes as tracers are mostly based for catchments with seasonal snowpack, while the influence in temperate and warm climates, leaving catchments with of fractionation during snowmelt could not be unequivocally strong snow influences underrepresented in the literature. shown. Our work showed the utility of isotopes to provide Such catchments are challenging, as the isotopic tracer sig- a proof of concept for our modelling framework in snow- nals in water entering the catchments as snowmelt are typi- influenced catchments.
    [Show full text]
  • Environmental Isotope Hydrology Environmental Isotope Hydrology Is a Relatively New Field of Investigation Based on Isotopic Variations Observed in Natural Waters
    Environmental Isotope Hydrology Environmental isotope hydrology is a relatively new field of investigation based on isotopic variations observed in natural waters. These isotopic characteristics have been established over a broad space and time scale. They cannot be controlled by man, but can be observed and interpreted to gain valuable regional information on the origin, turnover and transit time of water in the system which often cannot be obtained by other techniques. The cost of such investigations is usually relatively small in comparison with the cost of classical hydrological studies. The main environmental isotopes of hydrological interest are the stable isotopes deuterium (hydrogen-2), carbon-13, oxygen-18, and the radioactive isotopes tritium (hydrogen-3) and carbon-14. Isotopes of hydrogen and oxygen are ideal geochemical tracers of water because their concentrations are usually not subject to change by interaction with the aquifer material. On the other hand, carbon compounds in groundwater may interact with the aquifer material, complicating the interpretation of carbon-14 data. A few other environmental isotopes such as 32Si and 2381//234 U have been proposed recently for hydrological purposes but their use has been quite limited until now and they will not be discussed here. Stable Isotopes of Hydrogen and Oxygen in the Hydrological Cycle The variations of the isotopic ratios D/H and 18O/16O in water samples are expressed in terms of per mille deviation (6%o) from the isotope ratios of mean ocean water, which constitutes the reference standard SMOW: 5%o= (^ RSMOW The isotope ratio, R, is measured using a special mass spectrometer.
    [Show full text]
  • Subpixel Mapping of Surface Water in the Tibetan Plateau with MODIS Data
    remote sensing Article Subpixel Mapping of Surface Water in the Tibetan Plateau with MODIS Data Chenzhou Liu 1,* , Jiancheng Shi 2 , Xiuying Liu 1, Zhaoyong Shi 1 and Ji Zhu 3 1 Agricultural College, Henan University of Science and Technology, Luoyang 471003, China; [email protected] (X.L.); [email protected] (Z.S.) 2 State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China; [email protected] 3 College of Land Resources and Urban and Rural Planning, Hebei GEO University, Shijiazhuang 050031, China; [email protected] * Correspondence: [email protected]; Tel.: +86-379-6428-2340 Received: 8 February 2020; Accepted: 1 April 2020; Published: 3 April 2020 Abstract: This article presents a comprehensive subpixel water mapping algorithm to automatically produce routinely open water fraction maps in the Tibetan Plateau (TP) with the Moderate Resolution Imaging Spectroradiometer (MODIS). A multi-index threshold endmember extraction method was applied to select the endmembers from MODIS images. To incorporate endmember variability, an endmember selection strategy, called the combined use of typical and neighboring endmembers, was adopted in multiple endmember spectral mixture analysis (MESMA), which can assure a robust subpixel water fractions estimation. The accuracy of the algorithm was assessed at both the local scale and regional scale. At the local scale, a comparison using the eight pairs of MODIS/Landsat 8 Operational Land Imager (OLI) water maps demonstrated that subpixels water fractions were well retrieved with a root mean square error (RMSE) of 7.86% and determination coefficient (R2) of 0.98.
    [Show full text]
  • Download Wiki Attachment.Php?Attid= 3553&Page=Cryosat%20Technical%20Notes&Download=Y (Accessed on 1 January 2018)
    water Article A Modified Empirical Retracker for Lake Level Estimation Using Cryosat-2 SARin Data Hui Xue 1,2, Jingjuan Liao 1,* and Lifei Zhao 3 1 Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China; [email protected] 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Hebei Sales Branch of PetroChina Company Limited, Shijiazhuang 050000, China; [email protected] * Correspondence: [email protected]; Tel.: +86-010-8217-8160 Received: 29 September 2018; Accepted: 2 November 2018; Published: 5 November 2018 Abstract: Satellite radar altimetry is an important technology for monitoring water levels, but issues related to waveform contamination restrict its use for rivers, narrow reservoirs, and small lakes. In this study, a novel and improved empirical retracker (ImpMWaPP) is presented that can derive stable inland lake levels from Cryosat-2 synthetic aperture radar interferometer (SARin) waveforms. The retracker can extract a robust reference level for each track to handle multi-peak waveforms. To validate the lake levels derived by ImpMWaPP, the in situ gauge data of seven lakes in the Tibetan Plateau are used. Additionally, five existing retrackers are compared to evaluate the performance of the proposed ImpMWaPP retracker. The results reveal that ImpMWaPP can efficiently process the multi-peak waveforms of the Cryosat-2 SARin mode. The root-mean-squared errors (RMSEs) obtained by ImpMWaPP for Qinghai Lake, Nam Co, Zhari Namco, Ngoring Lake, Longyangxia Reservoir, Bamco, and Dawa Co are 0.085 m, 0.093 m, 0.109 m, 0.159 m, 0.573 m, 0.087 m, and 0.122 m, respectively.
    [Show full text]
  • 17O-Excess Traces Atmospheric Nitrate in Paleo Groundwater
    Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Biogeosciences Discuss., 10, 20079–20111, 2013 Open Access www.biogeosciences-discuss.net/10/20079/2013/ Biogeosciences BGD doi:10.5194/bgd-10-20079-2013 Discussions © Author(s) 2013. CC Attribution 3.0 License. 10, 20079–20111, 2013 This discussion paper is/has been under review for the journal Biogeosciences (BG). 17O-excess traces Please refer to the corresponding final paper in BG if available. atmospheric nitrate in paleo groundwater 17 O-excess traces atmospheric nitrate in M. Dietzel et al. paleo groundwater of the Saharan desert Title Page M. Dietzel1, A. Leis2, R. Abdalla1, J. Savarino3,4, S. Morin5, M. E. Böttcher6,*, and S. Köhler1,** Abstract Introduction 1Graz University of Technology, Institute of Applied Geosciences, Rechbauerstrasse 12, 8010 Conclusions References Graz, Austria Tables Figures 2Joanneum Research, Institute of Water Resources Management, Graz, Austria 3CNRS, Institut National des Sciences de l’Univers, France 4Laboratoire de Glaciologie et de Géophysique de l’Environnement, Université Joseph J I Fourier, Grenoble, France 5Météo-France – CNRS, CNRM-GAME URA 1357, CEN, Grenoble, France J I 6 Biogeochemistry Department, Max Planck Institute for Marine Microbiology, 28359 Bremen, Back Close Germany * now at: Leibniz Institute for Baltic Sea Research, Geochemistry & Isotope Geochemistry Full Screen / Esc Group, 18119 Warnemünde, Germany ** now at: Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Printer-friendly Version Sciences, Uppsala, Sweden Interactive Discussion 20079 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Received: 3 October 2013 – Accepted: 4 December 2013 – Published: 20 December 2013 Correspondence to: M. Dietzel ([email protected]) BGD Published by Copernicus Publications on behalf of the European Geosciences Union.
    [Show full text]
  • Isotopes in Climatological Studies Environmental Isotopes Are Helping Us Understand the World's Climate by Kazimierz Rozanski and Roberto Gonfiantini
    Features Isotopes in climatological studies Environmental isotopes are helping us understand the world's climate by Kazimierz Rozanski and Roberto Gonfiantini X he fundamental motivation for the recent explosion radiation, which otherwise would escape into space. of interest in climate studies is the growing scientific Carbon dioxide and methane are the most important concern that rapidly expanding human impact on the greenhouse gases, the concentration of which in the air global ecosystem may significantly alter the world's has been increasing since the middle of last century, climate in the near future. The major source for this con- mQiniw K»nr tint nnhf Hii£» tr\ the* nmwrinn /»ftncnrnn_ cern is the observed change in the earth's atmosphere, tion of fossil fuels. (See Table 1.) probably the most vulnerable component of the entire The predictions on the onset and extent of the green- ecosphere. house effect are, however, admittedly imprecise due to Observation data clearly show that the concentration the complexity of environmental interactions, and the in air of some trace constituents such as carbon dioxide, still incomplete knowledge of global meteorological and methane, carbon monoxide, ozone, chlorofluoro-hydro- climatological mechanisms. For instance, we are still far carbons (CFCs), nitrogen and sulphur oxides, is chang- from achieving a thorough understanding of the pro- ing as a result of anthropogenic emissions. These cesses regulating the composition of the atmosphere and changes may have harmful, far-reaching consequences the feedback mechanisms that operate between the major in the near future via direct effects on the biosphere — compartments (atmosphere, hydrosphere, biosphere, including human beings—and, indirectly, via the altera- geosphere) of the global ecosystem, and determine its tion of the life-supporting conditions.
    [Show full text]
  • Extreme Lake Level Changes on the Tibetan Plateau Associated With
    RESEARCH LETTER Extreme Lake Level Changes on the Tibetan Plateau 10.1029/2019GL081946 Associated With the 2015/2016 El Niño Key Points: Yanbin Lei1,2 , Yali Zhu3 , Bin Wang4 , Tandong Yao1,2, Kun Yang2,5 , Xiaowen Zhang1, • Dramatic lake shrinkage occurred 6 1 on the TP during the 2015/2016 El Jianqing Zhai , and Ning Ma Niño event, followed by rapid lake 1 expansion in 2016 and 2017 Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, • Considerable drought and lake Chinese Academy of Sciences, Beijing, China, 2CAS Center for Excellence in Tibetan Plateau Earth System, Beijing, shrinkage on the CTP also occurred China, 3Nansen‐Zhu International Research Centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, during historical El Niño events Beijing, China, 4Department of Meteorology and International Pacific Research center, University of Hawai‘iatMānoa, • ENSO may have dramatic impact on 5 6 the hydroclimate of the TP, Honolulu, HI, USA, Department of Earth System Science, Tsinghua University, Beijing, China, National Climate especially the CTP Center, China Meteorological Administration, Beijing, China Supporting Information: • Supporting Information S1 Abstract Although the impact of El Niño–Southern Oscillation on the Tibetan Plateau (TP) is reflected through stable isotopes of precipitation and ice cores, the hydroclimate response of TP lakes to El Niño–Southern Oscillation is seldom investigated. Here we show that significant lake water deficit Correspondence to: occurred on the central TP (CTP) due to a dramatic decrease in precipitation 2016 El Ni/2016 El Niño Y. Lei and Y. Zhu, [email protected]; event, followed by extreme lake water surplus in 2016 and 2017 over most of the TP (except the [email protected] eastern CTP).
    [Show full text]
  • CPY Document
    12. A REVIEW OF ISOTOPE APPLICATIONS IN CATCHMENT HYDROLOGY T. VITVAR, P.K. AGGARWAL Isotope Hydrology Section Division of Physical And Chemical Sciences, International Atomic Energy Agency, Vienna J. McDONNELL Oregon State University, Corvalls, Oregon, United States of America 1. Introduction Isotope methods were introduced into catchment hydrology research in the 1960s as complementar tools to conventional hydrologic methods for addressing questions of where water goes when it rains, what pathways it takes to the stream and how long water resides in the catchment (McDonnell, 20(3). Despite slow incorporation into routine research applications, the last decade has seen a rapid increase in isotope-based catchment studies. These have been mainly carried out in small well-instrented experimental catchments, on the order of 0.01 to 100 km and located typically in headwater areas (Buttle, 1998). In contrast, little has been done in terms of application and transfer of these concepts and methodologies to large (:;1 DOs to 1000s of ), less instrented basins. Much potential also waits to be realized in terms of how isotope information may be used to calibrate and test distributed rainfall-runoff models and to aid in the quantification of sustainable water resources management. In this chapter, we review the major applications of isotopes to catchment studies, and address a variety of prospective new directions in research and practice. Our discussion is based primarily on catchments in temperate to wet zones. 152 VITV AR, AGGARWAL, McDONNLL 2. Review of research 1. HISTORICAL OVERVIEW OF ISOTOPES EMPLOYED IN CATCHMENT HYDROLOGY Natural l4C was discovered in the late 1940s and natural 3H (tritium) was discovered in the early 1950s (Grosse et aI., 1951).
    [Show full text]
  • Investigation of the Ice Surface Albedo in the Tibetan Plateau Lakes Based on the Field Observation and MODIS Products
    Journal of Glaciology (2018), 64(245) 506–516 doi: 10.1017/jog.2018.35 © The Author(s) 2018. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons. org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Investigation of the ice surface albedo in the Tibetan Plateau lakes based on the field observation and MODIS products ZHAOGUO LI,1 YINHUAN AO,1 SHIHUA LYU,2,3 JIAHE LANG,1,4 LIJUAN WEN,1 VICTOR STEPANENKO,5 XIANHONG MENG,1 LIN ZHAO1 1Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions, Northwest Institute of Eco- Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China 2Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China 3Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China 4University of Chinese Academy of Sciences, Beijing 100049, China 5Lomonosov Moscow State University, GSP-1, 119991, Leninskie Gory, 1, bld.4, RCC MSU, Moscow, Russia Correspondence: Shihua Lyu <[email protected]>; Zhaoguo Li <[email protected]> ABSTRACT. The Tibetan Plateau (TP) lakes are sensitive to climate change due to ice-albedo feedback, but almost no study has paid attention to the ice albedo of TP lakes and its potential impacts. Here we present a recent field experiment for observing the lake ice albedo in the TP, and evaluate the applicabil- ity of the Moderate Resolution Imaging Spectroradiometer (MODIS) products as well as ice-albedo para- meterizations.
    [Show full text]
  • Isotope Hydrology: Investigating Groundwater Contamination Environmental Isotopes Are Used to Study Serious Pollution Problems by V
    Features Isotope hydrology: Investigating groundwater contamination Environmental isotopes are used to study serious pollution problems by V. Dubinchuk, K. Frohlich, and R. Gonfiantini During the past 100 years, groundwater has become nant surface water, in fact, was believed to be the source an increasingly important source of water supply world- of infirmities. wide for domestic, agricultural, and industrial uses. The Lately, however, groundwater quality has worsened almost ubiquitous occurrence of water-bearing forma- in many regions, with sometimes serious consequences. tions, the quality of groundwater, and the development Decontaminating groundwater is an extremely slow of well-drilling techniques have all helped to bring this process, and sometimes impossible, because of the about. generally long residence time of the water in most geo- Since it is naturally protected, groundwater has been logical formations. immune from contamination for a long time. It has been Major causes of contamination are poor groundwater cleaner and more transparent than surface water. From management (often dictated by immediate social needs) the time of Hipprocrates in the 5th century B.C., stag- and the lack of regulations and control over the use and disposal of contaminants. Agricultural practices, with Messrs Dubinchuk and Frohlich are staff members in the isotope the sometimes indiscriminate and frequently excessive hydrology section of the IAEA Division of Physical and Chemical use of fertilizers, herbicides, and pesticides, are among Sciences, and Mr Gonfiantini is Head of the section. the most relevant sources of groundwater contamina- Illustration of the water cycle 24 IAEA BULLETIN, 1/1989 Features tion. For instance, levels of nitrates often traceable to fertilizer usage are increasing in shallow aquifers.
    [Show full text]
  • Rapid and Punctuated Late Holocene Recession of Siling Co, Central Tibet
    Quaternary Science Reviews 172 (2017) 15e31 Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Rapid and punctuated Late Holocene recession of Siling Co, central Tibet * Xuhua Shi a, , Eric Kirby b, Kevin P. Furlong c, Kai Meng d, Ruth Robinson e, Haijian Lu f, Erchie Wang d a Earth Observatory of Singapore, Nanyang Technological University, 639798, Singapore b College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA c Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA d Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China e Department of Earth and Environmental Sciences, University of St Andrews, St Andrews KY16 9AL, UK f Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China article info abstract Article history: Variations in the strength of the Asian monsoon during Holocene time are thought to have been asso- Received 4 June 2017 ciated with widespread changes in precipitation across much of Tibet. Local records of monsoon strength Received in revised form from cave deposits, ice cores, and lake sediments typically rely on proxy data that relate isotopic vari- 16 July 2017 ations to changes in precipitation. Lake expansion and contraction in response to changing water balance Accepted 20 July 2017 are likewise inferred from sedimentologic, isotopic and paleobiologic proxies, but relatively few direct records of changes in lake volume from preserved shorelines exist. Here we utilize relict shoreline de- posits and associated alluvial fan features around Siling Co, the largest lake in central Tibet, to reconstruct Keywords: Holocene lake level fluctuations centennial-to-millennial-scale variations in lake area and volume over the Holocene.
    [Show full text]