FE 537. Catchment Scale. (Isotope Hydrology Primer Aside) Oregon State University

Transcription

1 Catchment Scale (Isotope Hydrology Primer Aside)

2 FE 537 Primer History Last 5 years: For IAEA in South Africa and China CSIRO Catchment Modeling School, Melbourne Dept. of Civil Engineering, U. Western Australia Dept,. of Physical Geography and Quaternary Studies, Stockholm University Dept. of Civil and Env. Engineering, Stuttgart University

3 Acknowledgements Carol Kendall, USGS Menlo Park Don Siegel, Syracuse University IAEA Isotope Hydrology Section

4 Tracing the hydrologic cycle Rainfall and where it goes Lake water and its evaporation, inflows and outflows Water residence time, transit time, water age Composition of streamflow New ways to calibrate and test hydrologic models A very different data source to help structure, test and calibrate models A way to figure out where trees (and other vegetation) get their water Hooper (2001)

5 Potential usefulness to local problems Determining components of flow to the Swedish Rivers Quantifying success in Land rehabilitation Lake/reservoir evaporation

6 A Useful Quote... The role of isotopes is like the role of the aliens in the famous sci-fi movie The Invasion of the Body Snatchers.. Isotopes and trace elements have pervaded the entire discipline (geochemistry) and they are us now! K. Turekian,, Editor Geochimica et Cosmochimica Acta.the same could now be said for Hydrology!

7 A recent GEOREF Search by Agarwaal (2002 HP) : : 650 papers using isotope tracers over 6500 papers using isotope tracers in groundwater studies alone

8 References - Textbooks Clark, I. and Fritz, P Environmental Isotopes in Hydrogeology. Lewis Publisher (w/ web-link) Kendall, C. and McDonnell, J.J. (eds.), Isotope Tracers in Catchment Hydrology. Elsevier (w/ web-link) Ferronsky,, V. I. And Polyakov,, V. A., Environmental Isotopes in the Hydrosphere. Wiley & Sons. Mazor,, E., Applied Chemical and Isotopic Groundwater Hydrology. Open University Press

9 The classic Rodhe, A., The origin of streamwater traced by oxygen-18. Ph.D. thesis, Uppsala Univ., Dept Phys. Geogr., Div. Hydrol., Report Series A 41, 290 p. + Appendix 73 p.

10 Isotope Tracers in Catchment Hydrology Isotope tracers have been among the most useful tools for understanding: -Groundwater-surface water interactions -Streamflow generation -Flowpath dynamics Kendall, C. and J. McDonnell eds (1998). Isotope Tracers in Catchment Hydrology, Elsevier Science Publishers, 817p

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12 References - Internet USGS Isotope Interest Group Home Page ( wwwcamnl.wr.usgs.gov/isoig/) /) ISOGEOCHEM Web Page with an E Discussion List in Stable Isotope Geochemistry ( ochem.html) IAEA web page and online teaching materials

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14 Head of IAEA Isotope Hydrology See Summer 2005 Science Times article in NYT by Pradeep and his IAEA group

15 Isotopes in Hydrology Environmental Isotopes STABLE RADIOACTIVE 2 H/H 18 O/ 16 O 13 C/ 12 C Cosmogenic Primordial Fallout Products Daughter Products

16 The Isotopes of General Hydrologic Interest in Hydrology Oxygen-18 and Oxygen-16 Hydrogen-2 (Deuterium) and H-1H Tritium (H-3) (From Don Siegel, SU)

17 Isotope hydrology T Kendall (2001)

18 Isotope biogeochemistry T Kendall (2001)

19 Applications of Isotopes as Tracers: 1. Tracers of the water itself (D, O, T) = Isotope Hydrology 2. Tracers of solutes or reactions (C, N, S) = Isotope Biogeochemistry This usage is NOT universal, but is very useful (conceptually) Kendall (2001)

20 Isotopes of water = history of water

21 Fundamentals Isotopes are atoms of the same element that have different numbers of neutrons. 18 O and 2 H are constituent part of natural water molecules they are the water molecule Applied naturally during precipitation events Conservative at ambient temperatures Only mixing can alter concentration Kendall (2001)

22 Isotopes are atoms of the same element that have FE 537 different numbers of neutrons. 16 O 17 O 18 O 14 N 15 N 12 C 13 C 14 C 10 B 11 B number of protons Z 9 Be 10 Be 6 Li 7 Li 3 He 4 He 1 H 2 H 3 H n number of neutrons N C. Kendall, USGS

23 Stable Isotopes 2 H and 18 O 18 O Relative amounts in earth s s hydrosphere: 18 O = 0.2%, 2 H = 0.015% 18 O and 2 H content of water changes only through fractionation associated with phase exchange processes (except for saline waters) Conservative behavior - once isotopes become part of water molecule, they change only through mixing Name 16 O Electrons 8 8 Protons 8 8 Neutrons 8 10 Abundance 99.76% 0.20% C. Kendall, USGS

24 Parts Per Mil Nomenclature Delta Isotope = (i.e. δ in o / oo ) Ratio sample - Ratio standard Ratio standard x 1000 in other words A DELTA O-18 = -10 o / oo means there is 10 parts per thousand less O-18 in the sample than in the standard, standard "mean" oceanic water (SMOW) Note ratio is 18 O/ 16 O (or 2 H/ 1 H for deuterium) (From Don Siegel, SU)

25 Fractionation Fractionation Some atoms of elements can have different weights. light heavy Fractionation sorting the light from the "heavy" versions of the elements. (From Don Siegel, SU)

26 Fractionation Effects Associated with Phase Changes of H 2 O Evaporation vapor that forms is lighter than surrounding water Condensation liquid that forms is heavier than surrounding vapor So, precipitation selectively removes 18 O and 2 H from the vapor phase

27 In other words University of Arizona

28 Fractionation in δ 18 O and δd during the hydrologic cycle

29 Commonly Used Terms: heavy vs. light isotopes the heavy isotope is the one with more neutrons; it is also generally the less abundant isotope. enriched vs. depleted remember to state what isotope is in short supply: does enriched sulfate mean that: the sulfate is enriched in heavy sulfur OR the sulfate is enriched in light sulfur? positive vs. negative / 00 is more positive than 20 0 / 00

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31 Fractionation Effects on 18 O and 2 H Equilibrium fractionation vapor pressure of water containing light isotopes > water containing heavy isotopes, therefore vapor is enriched in light isotopes E.g. at 100% humidity when the air is still and the system is almost chemically closed Kinetic fractionation rapid phase changes increase fractionation because light isotopes diffuse more rapidly than heavy ones E.g. this is more typical in hydrological systems where the system is out of chemical equilibrium (<100% humidity) or the products become slightly separated from the reactants (i.e. th resultant vapor is blown downwind).

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33 Example of a Rainfall Event: Fractionation in δ 18 O during the hydrologic cycle FE 537 Kendall (2001)

34 Fractionation Effects Associated with Phase Changes of H 2 O -- summary Evaporation vapor that forms is lighter than surrounding water Condensation liquid that forms is heavier than surrounding vapor So, precipitation selectively removes 18 O and 2 H from the vapor phase

35 Fractionation in the hydrological cycle

36 Some Effects Amount Effect: The more rainfall, the more depleted the rain Apparent Temperature Effect: Approximately 0.5%0 for every C C for oxygen Evaporation: As rain falls through dry air, it may evaporate, resulting in heavier rain Kendall (2001)

37 Some Effects Altitude effect: On the windward (not lee) side of a mountain the rain gets lighter with increasing altitude GRADIENTS O: to 0.5%0/100 meters D: -1.5 to 4%0/100 meters 18 O: Continental Effect: Delta values decrease inland Kendall (2001)

38 Geography and Seasonality of 18 O and 2 H Content of Precipitation Precipitation becomes lighter as air mass moves inland Precipitation becomes lighter with increasing elevation orographic effect Precipitation becomes lighter towards the poles and is lighter in winter than summer

39 Altitude Effect Source: IAEA

40 Amount effect Source: IAEA

41 Temperature Effect Source: IAEA

42 Continental effect

43 Continental Effect -8 Mean δo18 of the Columbia Watershed vs distanz from the West Coast Errorbars = 2x Stdev O18-11 Mean δo Distanz from the West Coast [km] Starke, McDonnell and Kendall, in prep

44 Elevation Effect Mean δ O18 of Columbia Watershed vs elevation Errorbars = 2x Stdev mean δ O elevation [m] Starke, McDonnell and Kendall, in prep

45 Air Temperature Effect 20 Athens Air Temp. (C) 0-20 Vienna Northern Sweden Delta O (after Don Siegel, SU)

46 Latitudinal Controls Northern Hemisphere IAEA

47 Latitudinal Controls Southern Hemisphere

48 Temperature Effects IAEA

49 Latitudinal Effect 0.00 Lower Warmer Latitude δ 18 O ( o / oo ) Waco, Texas Chicago, Illinois Barrow, Alaska Winter Spring Summer Fall J F M A M J J A S O N D Higher, Colder Latitude Months (From Don Siegel, SU)

50 Some spatial data (Kendall and Coplen, 2001)

51 summary (Kendall and Coplen, 2001)

52 Why are 18-O and D so similar? (Kendall and Coplen, 2001)

53 Global Meteoric Water Line because they are related 0 δ D = 8 δ 18 O δ D δ 18 O (From Don Siegel, SU)

54 dd = 8 d18o + 10 (Factoids)( The slope is 8 (actually, different data sets give slightly different values) because this is approximately the value produced by equilibrium Rayleigh condensation of rain at about 100% humidity. The value of 8 is also close to the ratio of the equilibrium fractionation factors for H and O isotopes at ºC. At equilibrium, the d values of the rain and the vapor both plot along the MWL, but separated by the 18O and 2H enrichment values corresponding to the temperature of the cloud base where rainout occurred. The y-intercept y value of 10 in the GMWL equation is called the deuterium excess (or d-excess, d or d parameter) value for this equation. The term only applies to the calculated y-intercept y for sets of meteoric data "fitted" to a slope of 8; typical d-excess d values range from 0 to 20 The fact that the intercept of the GMWL is 10 instead of 0 means that the GMWL does not intersect d18o = dd = 0, which is the composition of average ocean water (VSMOW). The GMWL does not intersect the composition of the ocean, the source of most of the water vapor that produces rain, because of the 10 kinetic enrichment in D of vapor evaporating from the ocean at an a average humidity of 85%.

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56 IAEA

57 IAEA Stations in GNIP IAEA

58 Globally IAEA (2001). GNIP Maps and Animations, International Atomic Energy Agency, Vienna. Accessible at

59 Global Atmospheric Circulation System Distills Water Isotopes Evaporation Even lighter water vapor Cold Light water vapor Condensation Hot equator Heavier Water Remains Solar Heat Heavier Rain Falls Raleigh Distillation (From Don Siegel, SU)

60 IAEA (2001). GNIP Maps and Animations, International Atomic Energy Agency, Vienna. Accessible at

61 IAEA (2001). GNIP Maps and Animations, International Atomic Energy Agency, Vienna. Accessible at

62 Precipitation in mid-latitude regions

63 The δd and δ 18 0 taken from the GNIP database were amount-weighted according to: δ x w n = δ n Σ P Σ i i =1 i= i 1 P i where Pi and δdi are the monthly precipitation amount (mm) and the isotopic composition ( ),( respectively, and n is the number of months.

64 Characteristics of δd and δ 18 0 of Precipitation: Consistent average compositions over time and space. Annual cycle of compositional changes heavy heavy in summer and light in winter. Large variations among storms. Often considerable variability within storms. Snow often plots along lines of higher d-exess than rain. Storms derived from different storms tracks may have consistently different meteoric water lines.

65 Database of H-H and O-IsotopesO Global Network for Isotopes in Precipitation ms/ri/gnip/gnipmain.htm

66 Now, back to the MWL IAEA

67 This knowledge can be very powerful e.g. Lake Chala in Kenya People wanted to use the Lake water for irrigation, but wanted to make sure that using lake water would have no adverse effect on the discharge of nearby springs whose waters were already being utilized. (i.e., they didn t t want to rob Peter to pay Paul )

68 Can they tap lake water without affecting spring flow? Carol Kendall, USGS

69 MWL at a single site Woods Lake USA Doug Burns, USGS

70 IAEA

71 Groundwater Isotopes Same as that for Average Precipitation 0 Groundwater Sample Average Precipitation δ D Well Mixed System--High Dispersion δ 18 O (From Don Siegel, SU)

72 Groundwater Isotopes Different than that for Average Precipitation δ D Groundwater Sample Average Precipitation Winter Recharge Summer Recharge "Plug Flow" - Low Dispersion Pleistocene Glacial Meltwater!! δ 18 O (From Don Siegel, SU)

73 Seasonal Variation in 18 O of Precipitation 18O (per mil SMOW) δ Neversink watershed, air temperature ( C) Jan-93 Jan-94 Jan-95 Jan-96 Vitvar, 2000 Vitvar, SUNY-ESF

74 What you might see in the Spring

75 Individual Rainfall Events Kendall (2001)