PART I. BASIC PRINCIPLES

Chapter 1: Fundamentals of Small Catchment Hydrology...................... 1
J.M. Buttle

1.1 Introduction to Small Catchments...................................... 1
1.2 The Catchment Water Balance........................................... 1
1.2.1 General components of the water balance............................. 1
1.2.2 Precipitation, interception, net precipitation...................... 2
1.2.3 Snowmelt........................................................... 10
1.2.4 Infiltration and soil water storage................................ 11
1.2.5 Evaporation and evapotranspiration................................. 19
1.2.6 Storage in lakes, wetlands and stream channels..................... 24
1.2.7 Runoff outputs via streamflow...................................... 26
1.2.8 Mechanisms of stormflow generation................................. 27
1.2.9 Groundwater flow................................................... 32
1.3 Questions of Spatial and Temporal Scale in Catchment Hydrology....... 33
1.4 Use of Isotopes in Catchment Research................................ 35
1.4.1 Evaporation, evapotranspiration, interception...................... 36
1.4.2 Pore-water mixing (the mobile-immobile water issue)................ 37
1.4.3 Soil and groundwater recharge rates................................ 38
1.4.4 Soil water, groundwater and surface water residence times.......... 39
1.4.5 Storm runoff components............................................ 40
1.4.6 Water sources versus water flowpaths............................... 41
1.4.7 Sources of solutes................................................. 42
1.5 New Research Directions.............................................. 42
1.6 Summary.............................................................. 43
References

Chapter 2: Fundamentals of Isotope Geochemistry.......................... 51
C. Kendall and E.A. Caldwell

2.1 Introduction......................................................... 51
2.2 Fundamentals of Isotope Geochemistry................................. 53
2.2.1 Definitions........................................................ 53
2.2.2 Terminology........................................................ 55
2.2.3 Standards.......................................................... 56
2.3 Stable Isotope Fractionation......................................... 57
2.3.1 Properties of isotopic molecules................................... 57
2.3.2 Fractionation accompanying chemical reactions and phase changes.... 57
2.3.3 The Rayleigh equations............................................. 61
2.3.4 Isotopic fractionation in open and closed systems.................. 61
2.3.5 Biological fractionations.......................................... 70
2.4 Sample Collection, Analysis, and Quality Assurance................... 72
2.4.1 Sampling guidelines................................................ 72
2.4.2 Analytical methods and instrumentation............................. 75
2.4.3 Quality assurance of contract laboratories......................... 77
2.5 Applications of Isotope Tracers in Catchment Hydrology............... 78
2.5.1 Water isotope hydrology............................................ 79
2.5.2 Solute isotope biogeochemistry..................................... 79
2.5.3 Mixing............................................................. 80
2.5.4 Isotopically labeled materials..................................... 82
2.5.5 Stable isotopes in geochemical modeling............................ 82
2.5.6 Use of a multi-isotope approach for the determination of flowpaths. 83
2.6 Summary ............................................................. 84
References
 

PART II. PROCESSES AFFECTING ISOTOPIC COMPOSITIONS

Chapter 3: Isotopic Variations in Precipitation.......................... 87
N.L. Ingraham

3.1 Introduction......................................................... 87
3.1.1 Global hydrologic cycle............................................ 88
3.2 Natural Fractionation of Isotopes in Precipitation................... 91
3.2.1 Co-variance of hydrogen and oxygen isotopes in precipitation....... 91
3.3 Systematics of Isotope Variations in Precipitation................... 94
3.3.1 System fractionation............................................... 94
3.3.2 Unique types of precipitation...................................... 96
3.3.3 Observed effects................................................... 100
3.3.4 Temporal variation in precipitation................................ 103
3.3.5 Geographic variation in precipitation in convective systems........ 104
3.3.6 Continental effect in precipitation................................ 104
3.3.7 Dependence of rain on ambient temperature.......................... 106
3.3.8 Exchange with atmospheric vapor.................................... 106
3.3.9 Evaporation on the canopy.......................................... 108
3.4 Mesoscale Circulation and Storm Trajectories......................... 108
3.5 Tritium.............................................................. 110
3.5.1 Origin............................................................. 110
3.5.2 Recent elevated levels and decline................................. 111
3.5.3 Observed terrestrial and marine distributions...................... 112
3.5.4 Uses of tritium in catchment basin research........................ 112
3.6 Implications for Catchment Basin Research............................ 113
3.6.1 Scale issues....................................................... 113
3.6.2 Sample collection.................................................. 113
3.7 Summary.............................................................. 115
References

Chapter 4: Isotopic Fractionation in Snow Cover.......................... 119
L.W. Cooper

4.1 Introduction......................................................... 119
4.2 Isotopic Changes to a Snowpack....................................... 120
4.2.1 Changes during snow accumulation................................... 120
4.2.2 Changes during snowmelt............................................ 123
4.2.3 Isotopic water balance and evaporation............................. 128
4.2.4 Catchment scale and runoff considerations.......................... 129
4.3 Future Directions for Research....................................... 131
References

Chapter 5: Isotopic Exchange in Soil Water............................... 137
C.J. Barnes and J.V. Turner

5.1 Introduction......................................................... 137
5.1.1 General discussion of isotopes..................................... 137
5.1.2 Analytical considerations.......................................... 138
5.1.3 Soil-water extraction techniques................................... 139
5.2 Processes Leading to Soil Water Concentration Variations:
Meteorological Inputs.................................................... 139
5.3 Processes Leading to Soil Water Concentration Variations: Evaporation 141
5.3.1 Introduction....................................................... 141
5.3.2 Saturated soils.................................................... 142
5.3.3 Unsaturated soils.................................................. 147
5.3.4 Unsteady evaporation............................................... 150
5.3.5 Temperature effects................................................ 155
5.3.6 Oxygen-18/deuterium relationship................................... 158
5.3.7 Further modifications due to salinity and transpiration............ 161
5.4 New Research Directions.............................................. 161
5.5 Summary.............................................................. 162
References

Chapter 6: Plants, Isotopes and Water Use: a Catchment-Scale Perspective. 165
T.E. Dawson and J.R. Ehleringer

6.1 Introduction......................................................... 165
6.1.1 Plants and catchment-level processes............................... 165
6.1.2 Working premise concerning plants, isotopes and water use.......... 166
6.2 Water Uptake and Water Transport in Plants........................... 167
6.2.1 Background......................................................... 167
6.2.2 Measurements of water uptake and transport by plants............... 169
6.3 Stomatal Regulation of Water Movement in the Soil-Plant-Atmosphere
Continuum................................................................ 173
6.3.1 Water movement and the regulatory role of plants: leaf-level....... 173
6.3.2 Water movement and the regulatory role of plants: stand-level...... 175
6.4 Water Sources and Water Use by Plants: Case Studies Using Stable Isotopes................................................................. 177
6.4.1 Riparian forest communities........................................ 178
6.4.2 Arid and semi-arid plant communities............................... 179
6.4.3 Temperate forest communities....................................... 180
6.4.4 Coastal plant communities.......................................... 186
6.5 Current Issues Involving Plants and Catchment-Scale Hydrologic Processes................................................................ 188
6.5.1 Invasive plants and site water balance............................. 188
6.5.2 Stream diversions and riparian manipulations....................... 189
6.5.3 Deforestation, reforestation and desertification................... 190
6.6 Long-term Record of Water Use by Plants.............................. 192
6.7 Merging the Study of Stable Isotopes in Water with Studies of Water
Uptake and Water Use in Plants and the Hydrology of Catchments........... 194
References

Chapter 7: Isotopes in Groundwater Hydrology............................. 203
R. Gonfiantini, K. Fröhlich, L. Araguas-Araguas and K. Rozanski

7.1 Introduction......................................................... 203
7.2 Isotopic Variations in Waters Recharging the Aquifers................ 204
7.2.1 The isotopic composition of precipitation.......................... 204
7.2.2 The isotopic composition of surface waters......................... 206
7.3 Isotopic Effects in the Unsaturated Zone............................. 207
7.3.1 Mechanisms of infiltration......................................... 207
7.3.2 Water movement in the unsaturated zone............................. 207
7.3.3 Dissolution processes.............................................. 209
7.4 Shallow Aquifers..................................................... 211
7.4.1 Recharge by precipitation.......................................... 211
7.4.2 Recharge from surface waters....................................... 214
7.4.3 Hydrodynamical models of shallow groundwater systems based on
isotopic data............................................................ 217
7.5 Deep Groundwater..................................................... 225
7.5.1 Groundwater movement in confined aquifers.......................... 225
7.5.2 Groundwater age.................................................... 225
7.5.3 Interconnections between aquifers.................................. 233
7.5.4 Geothermal groundwaters............................................ 234
7.6 Groundwater Studies in Catchments.................................... 234
7.6.1 Present situation and case study examples.......................... 234
7.6.2 Research trends and needs.......................................... 238
References

Chapter 8: Lithogenic and Cosmogenic Tracers in Catchment Hydrology...... 247
G.J. Nimz

8.1 Introduction......................................................... 247
8.2 Processes that Affect Lithogenic and Cosmogenic Isotopic Compositions
in Hydrologic Systems.................................................... 248
8.2.1 Lithogenic and cosmogenic solutes used in hydrologic analysis...... 248
8.2.2 Origin of lithogenic nuclides in natural waters: mineral reactions. 248
8.2.3 Origin of lithogenic nuclides in natural waters: trace element exchange................................................................. 249
8.2.4 Origin of isotopic variations: radiogenic nuclides................. 251
8.2.5 Origin of isotopic variations: the mineral weathering sequence..... 253
8.2.6 Origin of isotopic variations: uranium isotopes and alpha recoil... 255
8.2.7 Origin of isotopic variations: cosmogenic nuclides................. 257
8.2.8 Origin of isotopic variations: fission products.................... 258
8.2.9 Hydrologic application of cosmogenic nuclides...................... 259
8.3 The Application of Lithogenic and Cosmogenic Nuclides to Catchment
Hydrology................................................................ 262
8.3.1 Input: precipitation, dry deposition, and throughfall.............. 263
8.3.2 The shallow system: hydrograph separation, weathering, and
arid-region infiltration................................................. 266
8.3.3 Evaporation/transpiration.......................................... 272
8.3.4 The deep system: groundwater flow.................................. 272
8.3.5 System (basin) closure: mixing of water masses..................... 274
8.3.6 Streamflow: mass balance within the catchment...................... 276
8.3.7 Lithogenic and cosmogenic nuclides: summary........................ 276
8.4 New Directions in Lithogenic and Cosmogenic Nuclides................. 277
8.4.1 The other geologic giant: neodymium................................ 277
8.4.2 Lithogenic elements with fractionating isotopes.................... 278
8.4.3 New directions in catchment hydrology for cosmogenic nuclides...... 280
8.5 Lithogenic and Cosmogenic Tracers in Catchment Hydrology: Concluding Remarks.................................................................. 281
References

Chapter 9: Dissolved Gases in Subsurface Hydrology....................... 291
D.K. Solomon, P.G. Cook and W.E. Sanford

9.1 Introduction......................................................... 291
9.2 Occurrence and Transport of Dissolved Gases.......................... 291
9.3 Shallow Groundwater Dating........................................... 294
9.3.1 3H/3He............................................................. 297
9.3.2 Chlorofluorocarbons................................................ 299
9.3.3 85Kr............................................................... 302
9.3.4 Radiogenic 4He..................................................... 303
9.3.5 Field examples of groundwater dating............................... 305
9.4 Groundwater Surface-Water Interactions............................... 308
9.4.1 4He................................................................ 308
9.4.2 222Rn.............................................................. 309
9.5 Injected Dissolved Gas Tracers....................................... 309
9.5.1 Field example: noble gas tracer experiment......................... 311
9.6 Future Directions.................................................... 313
References
 

PART III. CASE STUDIES IN ISOTOPE HYDROLOGY

Chapter 10: Oxygen and Hydrogen Isotopes in Rainfall-Runoff Studies...... 319
D.P. Genereux and R.P. Hooper

10.1 Introduction........................................................ 319
10.2 Hydrograph Separation............................................... 320
10.2.1 Terminology....................................................... 320
10.2.2 Requirements and assumptions in hydrograph separation............. 321
10.2.3 Findings and examples............................................. 321
10.2.4 Scale dependence of ƒpe values.................................... 330
10.2.5 Intra-component variability in tracer concentrations.............. 332
10.2.6 Recommendations for field studies................................. 338
10.3 New Directions...................................................... 339
10.3.1 Subsurface mixing and residence time.............................. 339
10.3.2 Use of isotopes in model calibration.............................. 341
10.4 Conclusions......................................................... 343
References

Chapter 11: High Rainfall, Response-Dominated Catchments: A Comparative
Study of Experiments in Tropical Northeast Queensland with Temperate New Zealand.................................................................. 347
M. Bonell, C.J. Barnes, C.R. Grant, A. Howard and J. Burns

11.1 Introduction........................................................ 347
11.2 Previous Studies in High Rainfall, Response - Dominated Catchments.. 348
11.2.1 The Maimai catchments............................................. 348
11.2.2 Linkages between the Maimai and Babinda studies................... 349
11.3 Physical Background................................................. 349
11.4 Experimental Methods................................................ 353
11.4.1 Precipitation..................................................... 353
11.4.2 Streamflow........................................................ 353
11.4.3 Hillslope instrumentation......................................... 354
11.5 Results: Event of February 16, 1991................................. 355
11.5.1 Antecedent catchment storage and rainfall-runoff of sample storm.. 355
11.5.2 Matric and hydraulic potential changes on sample slope transects.. 360
11.5.3 Hydrograph analysis............................................... 366
11.6 Stream Hydrograph Analysis and Isotopic Response.................... 368
11.6.1 Event analysis - general considerations........................... 368
11.6.2 Soil and groundwater isotopic changes............................. 370
11.7 How High Rainfall Catchments Work................................... 379
11.7.1 The Babinda model................................................. 379
11.7.2 The secondary store issue......................................... 382
11.7.3 New water dominance at Babinda vs old water dominance at Maimai... 383
11.8 Future Research Directions.......................................... 385
References

Chapter 12: Snowmelt-Dominated Systems................................... 391
A. Rodhe

12.1 Introduction........................................................ 391
12.1.1 Basic hydrological processes...................................... 392
12.1.2 Global geographical distribution.................................. 397
12.1.3 Isotopic characteristics of snowmelt.............................. 397
12.2 Hydrograph Separation Studies....................................... 399
12.2.1 Historical studies................................................ 399
12.2.2 Recent studies with more complete characterization................ 401
12.3 Vertical Unsaturated Flow........................................... 418
12.3.1 Estimates of groundwater recharge and particle velocity........... 419
12.3.2 Piston flow versus macropore flow................................. 420
12.3.3 Transit times and flow pattern from lysimeter studies............. 422
12.3.4 Flow pattern in two and three dimensions.......................... 426
12.3.5 Implications for catchment flow studies........................... 429
12.4 Conclusions and Future Research Directions.......................... 429
References

Chapter 13: Arid Catchments.............................................. 435
N.L. Ingraham, E.A. Caldwell and B.Th. Verhagen

13.1 Introduction........................................................ 435
13.2 The Use of Isotopes in Arid Catchment Studies....................... 437
13.2.1 Precipitation..................................................... 437
13.2.2 Lakes............................................................. 440
13.2.3 Rivers............................................................ 441
13.2.4 Rivers displaying isotopic enrichment............................. 443
13.2.5 Rivers without isotopic enrichment................................ 446
13.2.6 Soil water........................................................ 446
13.2.7 Infiltration and recharge in arid regions......................... 447
13.2.8 Groundwater....................................................... 451
13.2.9 The ‘d' value in arid groundwater................................. 452
13.3 Sampling............................................................ 453
13.3.1 Precipitation..................................................... 454
13.3.2 Surface water..................................................... 454
13.3.3 Soil water........................................................ 455
13.4 Non-Traditional Techniques.......................................... 455
13.4.1 Strontium......................................................... 456
13.4.2 ³He/Tritium....................................................... 457
13.4.3 Chlorine-36....................................................... 458
13.4.4 Noble Gases....................................................... 459
13.4.5 Chlorofluorocarbons............................................... 460
13.5 Future Directions................................................... 460
References

Chapter 14: Groundwater and Surface-Water Interactions in Riparian and
Lake-Dominated Systems................................................... 467
J.F. Walker and D.P. Krabbenhoft

14.1 Introduction........................................................ 467
14.1.1 Importance of lake-dominated systems.............................. 467
14.1.2 Dominant hydrological processes................................... 467
14.2 Previous Studies in Lake Systems.................................... 469
14.3 Estimating Groundwater Exchange with Lakes.......................... 470
14.3.1 Stable-isotope mass-balance method................................ 471
14.3.2 Index-lake method................................................. 474
14.4 Wisconsin WEBB Case Study........................................... 478
14.4.1 Study area........................................................ 478
14.4.2 Study design...................................................... 480
14.4.3 Isotopic flow-system progression.................................. 482
14.4.4 Isotopic complexity............................................... 484
14.5 Concluding Remarks.................................................. 486
References

PART IV. CASE STUDIES IN ISOTOPE GEOCHEMISTRY

Chapter 15: Use of Stable Isotopes in Evaluating Sulfur Biogeochemistry
of Forest Ecosystems..................................................... 489
M.J. Mitchell, H.R. Krouse, B. Mayer, A.C. Stam and Y. Zhang

15.1 Introduction: Forest Ecosystem Sulfur Dynamics...................... 489
15.2 Controls on Sulfur Isotope Composition.............................. 491
15.2.1 Isotope fractionation............................................. 492
15.2.2 Atmospheric sources of sulfur..................................... 495
15.2.3 Geological sources of sulfur...................................... 495
15.2.4 Sulfur isotopes in the hydrosphere................................ 497
15.2.5 Sulfur isotopes in soil and terrestrial vegetation................ 499
15.3 Natural Abundance Studies........................................... 500
15.3.1 Hubbard Brook Experimental Forest, New Hampshire.................. 500
15.3.2 Bear Brook Watershed, Maine....................................... 502
15.3.3 Experimental Lakes Area, Ontario, Canada.......................... 505
15.3.4 Rocky Mountains, Colorado and Wyoming............................. 505
15.3.5 Black Forest, Germany............................................. 507
15.4 Applied Tracer Studies.............................................. 508
15.4.1 Hubbard Brook Experimental Forest, New Hampshire.................. 508
15.4.2 Bear Brook Watershed, Maine....................................... 510
15.4.3 West Whitecourt, Alberta, Canada.................................. 511
15.4.4 Bavaria, Germany.................................................. 512
15.4.5 Höglwald, Germany................................................. 512
15.4.6 Black Forest, Germany............................................. 513
15.4.7 Skjervatjern Catchment, Norway.................................... 514
15.4.8 Lake Gårdsjön Catchment, Sweden................................... 514
15.5 New Research Directions............................................. 514
15.6 Summary............................................................. 515
References

Chapter 16: Tracing Nitrogen Sources and Cycling in Catchments............ 519
C. Kendall

16.1 Introduction........................................................ 519
16.1.1 Fundamentals of nitrogen isotopes................................. 520
16.1.2 Methods........................................................... 520
16.2 The Nitrogen Cycle.................................................. 523
16.2.1 Isotopic fractionations........................................... 523
16.2.2 Processes affecting N isotopic compositions....................... 526
16.3 Delta 15N Values of Nitrogen Sources and Reservoirs................. 531
16.3.1 Atmospheric sources............................................... 532
16.3.2 Fertilizers....................................................... 534
16.3.3 Animal waste...................................................... 534
16.3.4 Plants............................................................ 534
16.3.5 Soils............................................................. 535
16.3.6 Groundwaters...................................................... 537
16.4 Delta 18O Values of Nitrate Sources and Reservoirs.................. 538
16.4.1 Atmospheric nitrate............................................... 539
16.4.2 Synthetic fertilizers and reagents................................ 542
16.4.3 Microbial nitrate................................................. 542
16.4.4 Other processes affecting nitrate 18O values...................... 545
16.5 Tracing Sources and Cycling of Nitrate.............................. 545
16.5.1 Mixing............................................................ 547
16.5.2 Denitrification................................................... 548
16.6 Application Studies................................................. 552
16.6.1 Agricultural and urban sources of nitrate......................... 552
16.6.2 Sources of N in acid-rain affected forested catchments............ 556
16.6.3 Nitrogen-limited systems.......................................... 560
16.6.4 Labeled-tracer studies............................................ 560
16.6.5 Food web studies.................................................. 562
16.7 New Frontiers....................................................... 563
16.7.1 Applications of the dual isotope method........................... 564
16.7.2 Tracing sources and sinks for DOM................................. 564
16.7.3 Applications of compound-specific isotope ratio mass spectrometry. 565
16.7.4 Use of isotopic techniques to assess impacts of changes in
land-management practices and landuse on water quality................... 566
16.7.5 Use of a multi-isotope or multi-tracer approach................... 568
16.7.6 Development of linked hydrologic/geochemical models............... 568
16.8 Summary............................................................. 569
References

Chapter 17: Carbon Cycling in Terrestrial Environments................... 577
Y. Wang, T.G. Huntington, L.J. Osher, L.I. Wassenaar, S.E. Trumbore,
R.G. Amundson, J.W. Harden, D.M. McKnight, S.L. Schiff, G.R. Aiken,
W.B. Lyons, R.O. Aravena and J.S. Baron

17.1 Introduction........................................................ 577
17.2 Carbon Isotopes and Terminology..................................... 578
17.3 Carbon Dynamics in Soils............................................ 580
17.3.1 14C age of soil organic matter.................................... 581
17.3.2 Use of 14C to study C turnover in soils........................... 585
17.3.3 The use of 13C to study C turnover in soils....................... 590
17.3.4 Use of carbon isotopes in understanding carbon dynamics in
peatlands................................................................ 593
17.4 Isotope Studies of Dissolved Organic Matter in Groundwater.......... 595
17.4.1 Stable carbon isotopes............................................ 598
17.4.2 Nitrogen, sulfur and hydrogen isotopes............................ 599
17.4.3 Radiocarbon in DOC................................................ 599
17.5 Isotope Study of DOC in Lacustrine Environments..................... 600
17.6 Isotope Studies and the Carbon Budget............................... 602
References

Chapter 18: Tracing of Weathering Reactions and Water Flowpaths:
A Multi-isotope Approach................................................. 611
T.D. Bullen and C. Kendall

18.1 Introduction........................................................ 611
18.1.1 Rationale for using water and solute isotopes as tracers in
catchments............................................................... 611
18.1.2 Theoretical bases of the strontium, lead and carbon isotope
systems.................................................................. 613
18.1.3 Geological/environmental factors leading to successful tracing
with olute isotopes...................................................... 618
18.2 Influences on Isotopic Composition of Sr, Pb and C in Catchment
Waters................................................................... 619
18.2.1 Lithologic controls on the isotopic composition of strontium and
lead..................................................................... 619
18.2.2 Atmospheric/anthropogenic inputs of Sr, Pb, and C................. 624
18.2.3 Effects of organic and inorganic cycling on isotopic composition
of carbon................................................................ 625
18.3 Multi-Isotope Studies at Selected Watersheds........................ 627
18.3.1 The combined use of O, H and Sr isotopes to understand
differences in chemical evolution along different flowpaths in a sandy
aquifer in northern Wisconsin............................................ 627
18.3.2 Sr, Pb and C isotopes as surrogate tracers of water movement at a
catchment nested in calc-silicate rocks, Sleepers River, Vermont......... 630
18.3.3 C and Sr isotopes as tracers of sources of carbonate alkalinity at
Catoctin Mountain, Maryland.............................................. 635
18.3.4 Synthesis: an isotopic view of a catchment........................ 638
18.4 Additional Solute Isotope Tracers: Li, B, Fe........................ 640
18.5 Summary............................................................. 643
References

Chapter 19: Erosion, Weathering, and Sedimentation....................... 647
P.R. Bierman, A. Albrecht, M.H. Bothner, E.T. Brown, T.D. Bullen,
L.B. Gray and L. Turpin

19.1 Introduction........................................................ 647
19.2 In Situ Produced Cosmogenic Nuclides................................ 648
19.2.1 Cosmogenic nuclides in exposed outcrops........................... 648
19.2.2 Cosmogenic nuclides in sediments.................................. 650
19.2.3 Case studies...................................................... 652
19.3 Atmospheric Nuclides: 210Pb......................................... 655
19.3.1 Methods........................................................... 656
19.3.2 Interpretation.................................................... 658
19.3.3 Applications...................................................... 659
19.4 Combined Approaches To Catchment Landscape Analysis:
137Cs and 210Pb.......................................................... 659
19.4.1 Lake sediments.................................................... 660
19.4.2 Soils............................................................. 661
19.4.3 Water samples..................................................... 662
19.4.4 Case studies...................................................... 662
19.5 Tracing of Sediment Sources and Identification of Erosion
Processes Using Natural and Anthropogenic Radionuclides.................. 666
19.5.1 Nuclides of importance............................................ 667
19.5.2 Case studies...................................................... 668
19.6 Sr and Weathering................................................... 670
19.6.1 Weathering and 87Sr/86Sr.......................................... 670
19.6.2 Typical 87Sr/86Sr ratios.......................................... 672
19.6.3 Sr isotopes as tracers of solute sources.......................... 672
References

Chapter 20: Applications of Uranium- and Thorium-Series Radionuclides in
Catchment Hydrology Studies.............................................. 679
T.F. Kraemer and D.P. Genereux

20.1 Introduction........................................................ 679
20.2 Review of Fundamental Concepts...................................... 680
20.2.1 Decay chains and radioactive equilibrium.......................... 680
20.2.2 Physical and chemical processes that redistribute U and Th series
radionuclides............................................................ 681
20.3 Radon Techniques in Catchment Hydrology............................. 688
20.3.1 General considerations, mixing models............................. 688
20.3.2 Mixing model without correction for volatilization................ 689
20.3.3 Mixing model with degassing correction through stagnant film model 691
20.3.4 Mixing model with degassing correction through an injected tracer. 695
20.3.5 Mixing model, with partitioning of water inflow into different
sources.................................................................. 699
20.4 Radium Isotopic Techniques in Catchment Hydrology................... 705
20.4.1 General considerations............................................ 705
20.4.2 Radium as a tracer for groundwater input to an estuary system..... 705
20.4.3 Use of ²²⁸Ra and ²²⁶Ra in quantifying groundwater input to a
stream: conservative mixing.............................................. 709
20.4.4 Use of ²²⁸Ra and ²²⁶Ra in quantifying groundwater input to a
stream: non-conservative mixing.......................................... 713
20.4.5 Use of ²²⁸Ra and ²²⁶Ra in quantifying three end-member
conservative mixing...................................................... 714
20.4.6 Using ²²⁴Ra and ²²⁸Ra to determine residence time of water in
short-residence time reservoirs.......................................... 716
20.4.7 Using radium isotopes to identify the source of water issuing
from springs............................................................. 718
20.5 New Research Directions............................................. 719
References
 

PART V. SYNTHESIS

Chapter 21: Modeling of Isotopes and Hydrogeochemical Responses in
Catchment Hydrology...................................................... 723
J.V. Turner and C.J. Barnes

21.1 Introduction........................................................ 723
21.1.1 Some definitions and terms........................................ 726
21.2 Limitations of the Mass Balance Hydrograph Separation Approach...... 727
21.2.1 Mass balance hydrograph separation models......................... 727
21.3 Estimation of Transit Times - System Response Functions of
Catchments............................................................... 732
21.3.1 System response functions......................................... 732
21.3.2 System response functions based on the IUH........................ 733
21.3.3 Application of system response functions based on the
Instantaneous Unit Hydrograph............................................ 738
21.3.4 Identifying "old" and "new" water in terms of system response
functions................................................................ 741
21.3.5 Time series approaches to system response functions............... 742
21.3.6 Kalman filtering and residence times.............................. 744
21.4 Comparisons of Models of Isotopic and Chemical Hydrograph
Separation............................................................... 751
21.5 New Research Directions............................................. 757
References

Chapter 22: Isotopes as Indicators of Environmental Change............... 761
J.B. Shanley, E. Pendall, C. Kendall, L.R. Stevens, R.L. Michel,
P.J. Phillips, R.M. Forester, D.L. Naftz, B. Liu, L. Stern, B.B. Wolfe,
C.P. Chamberlain, S.W. Leavitt, T.H.E. Heaton, B. Mayer, L.D. Cecil,
W.B. Lyons, B.G. Katz, J.L. Betancourt, D.M. McKnight, J.D. Blum,
T.W.D. Edwards, H.R. House, E. Ito, R.O. Aravena and J.F. Whelan

22.1 Introduction........................................................ 761
22.1.1 Direct and proxy records of environmental change.................. 762
22.2 Recent Environmental Change Indicators.............................. 763
22.2.1 Groundwater dating................................................ 763
22.2.2 Direct use of water isotopes to infer recent global change........ 765
22.2.3 Changes in land use deduced from tracer studies................... 766
22.2.4 Isotope tracers for tracking migratory patterns of birds.......... 768
22.2.5 Changes in atmospheric deposition................................. 771
22.3 Paleo-Climatic Indicators........................................... 776
22.3.1 Groundwater as an archive of paleo-climatic information........... 776
22.3.2 Continental glaciers.............................................. 778
22.3.3 Clay minerals, oxides, and hydroxides............................. 780
22.3.4 Pedogenic carbonates.............................................. 782
22.3.5 Paleoenvironmental reconstruction from stable isotopes in tree
rings and plant fossils.................................................. 785
22.3.6 Lacustrine environments: organics................................. 792
22.3.7 Lacustrine environments: authigenic carbonates.................... 795
22.3.8 Lacustrine environments: ostracodes............................... 799
22.4 New Research Directions............................................. 802
22.5 Summary............................................................. 803
References

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