Wetlands are poorly documented features of many landscapes, and there is often little understanding of the geomorphological controls on their origin, development and characteristics. This paper addresses the apparent paradox of wetlands in drylands, focusing particularly on the geomorphology and sedimentology of wetlands in southern Africa. Drylands are characterized by high (but variable) levels of aridity, reflecting low ratios between precipitation and potential evapotranspiration, so wetlands can only exist where there are locally positive surface water balances for all or part of the year. Most moderate to large wetlands in drylands are thus maintained by river inflows that combine with other factors that serve to impede drainage or reduce infiltration, including faulting, rock outcrops, swelling soils, and ponding by tributary or aeolian sediments. Together with variations in sediment supply, vegetation communities, and levels of animal activity, this promotes a diverse range of wetlands that span a continuum from permanently inundated, to seasonally inundated, to ephemerally inundated. In detail, every wetland has a unique range of geomorphological and sedimentological characteristics but, at a general level, the dryland setting can be shown to impart some distinctive features. By comparison with humid region (tropical and temperate) wetlands, we propose that many wetlands in drylands are characterized by: 1) more frequent and/or longer periods of desiccation; 2) channels that commonly decrease in size and even disappear downstream; 3) higher levels of chemical sedimentation; 4) more frequent fires that reduce the potential for thick organic accumulations and promote aeolian activity; and 5) longer timescales of development that may extend far back into the Pleistocene. Additional studies of wetlands in different drylands may reveal other distinctive characteristics. Correct identification of the factors giving rise to wetlands, and improved understanding of the geomorphological and sedimentological processes governing their development, is vital for the design of sustainable management guidelines for these diverse yet fragile habitats.
Adams, G. D.1988: Wetlands of the prairies of Canada. In National Wetlands Working Group and Canada Committee on Ecological Land Classification, Wetlands of Canada, Ottawa : Canadian Government Publications and Polyscience Publications Series 24, 157-198.
2.
Adamson, D. , Williams, M. A. J. and Baxter, J. T.1987: Complex Late Quaternary alluvial history in the Nile, Murray-Darling, and Ganges basins: three river systems presently linked to the Southern Oscillation. In Gardiner, V. , editor, International geomorphology 1986: Part II, Chichester: Wiley , 875-887.
3.
Allan, D. G. , Seaman, M. T. and Kaletja, B.1995: The endorheic pans of South Africa. In Cowan, G. I. , editor, Wetlands of South Africa, South African Wetlands Conservation Programme Series, Pretoria: Department of Environmental Affairs and Tourism , 75-101.
4.
Allanson, B. R. , Hart, R. C. , O’Keefe, J. H. and Robarts, R. D.1990: Inland waters of southern Africa: an ecological perspective. Monographiae Biologicae 64. The Hague: Kluwer .
5.
Ashley, G. M. , Goman, M. F. , Hover, V. C. , Owen, R. B. , Renaut, R. W. and Muasya, A. M.2002: Artesian blister wetlands, a perennial water resource in the semi-arid Rift Valley of East Africa . Wetlands22, 686-695 .
6.
Ashley, G. M. , Mworia, J. M. , Muasya, A. M. , Owen, R. B. , Driese, S. G. , Hover, V. C. , Renaut, R. W. , Goman, M. F. , Mathai, S. and Blatt, S. H.2004: Sedimentation and recent history of a freshwater wetland in a semi-arid environment: Loboi Swamp, Kenya, East Africa . Sedimentology51, 1301-1321 .
7.
Ashmore, P. and Church, M.2001: The impact of climate change on rivers and river processes in Canada. Geological Survey of Canada, Bulletin 555. Ottawa: Natural Resources Canada .
8.
Begg, G.1986: The wetlands of Natal (Part 1): an overview of their extent, role and present status. Natal Town and Regional Planning Report 68. Pietermaritzburg: The Natal Town and Regional Planning Commission .
9.
Breen, C. M. and Begg, G. W.1989: Conservation status of southern Africa wetlands. In Huntley, B. J. , editor, Biotic diversity in southern Africa: concepts and conservation, Cape Town: Oxford University Press , 254-264.
10.
Burkett, V. and Kusler, J.2000: Climate change: potential impacts and interactions in wetlands of the United States . Journal of the American Water Resources Association36, 313-320 .
11.
Butzer, K. W.1988: Sedimentological interpretation of the Florisbad spring deposits, South Africa . Palaeoecology of Africa19, 181-189 .
12.
Cowan, G. I. , editor 1995a: Wetlands of South Africa. South African Wetlands Conservation Programme Series. Pretoria: Department of Environmental Affairs and Tourism .
13.
Cowan, G. I.1995b: Wetland regions of South Africa. In Cowan, G. I. , editor, Wetlands of South Africa, South African Wetlands Conservation Programme Series, Pretoria: Department of Environmental Affairs and Tourism , 21-31.
14.
Cowan, G. I. and van Riet, W.1998: A directory of South African wetlands. Pretoria: Department of Environmental Affairs and Tourism .
15.
Cowardin, L. M. , Carter, V. , Golet, F. C. and LaRoe, E. T.1979: Classification of wetlands and deepwater habitats of the United States. Report FWS/OBS-79/31. Washington, DC: US Fish and Wildlife Service .
16.
de Bruiyn, H.1971: Pans in the western Orange Free State . Annals of the Geological Survey of South Africa9, 121-124 .
17.
Dugan, P. J. , editor 1993: Wetlands in danger. London: Mitchell Beazley and IUCN (World Conservation Union) .
18.
Dunagan, S. P. and Turner, C. E.2004: Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA . Sedimentary Geology167, 269-296 .
19.
du Toit, A. L.1933: Crustal movement as a factor in the geographical evolution of South Africa . South African Geographical Journal16, 3-20 .
20.
Ellery, W. N. and McCarthy, T. S.1994: Principles for the sustainable utilization of the Okavango Delta ecosystem, Botswana . Biological Conservation70, 159-168 .
21.
Ellery, W. N. , Ellery, K. , McCarthy, T. S. , Cairncross, B. and Oelofse, R.1989: A peat fire in the Okavango Delta, Botswana, and its importance as an ecosystem process . African Journal of Ecology27, 7-21 .
22.
Ellery, W. N. , Ellery, K. , Rogers, K. H. and McCarthy, T. S.1995: The role of Cyperus papyrus L. in channel blockage and abandonment in the northeastern Okavango Delta, Botswana . African Journal of Ecology33, 25-49 .
23.
Epstein, C. M.2002: Application of Rosgen analysis to the New Jersey Pine Barrens . Journal of the American Water Resources Association38, 69-78 .
24.
Eugster, H. P. and Jones, B. F.1979: Behavior of major solutes - closed-basin brine evolution . American Journal of Science279, 609-631 .
25.
Finlayson, C. M. and van der Valk, A. G.1995a: Wetland classification and inventory: a summary . Vegetatio118, 185-192 .
26.
Finlayson, C. M. and van der Valk, A. G.1995b: Classification and inventory of the world’s wetlands . Vegetatio118-118 .
27.
Goudie, A. S. and Thomas, D. S. G.1985: Pans in southern Africa with particular reference to South Africa and Zimbabwe . Zeitschrift für Geomorphologie29, 1-19 .
28.
Goudie, A. S. and Thomas, D. S. G.1986: Lunette dunes in southern Africa . Journal of Arid Environments10, 1-12 .
29.
Goudie, A. S. and Wells, G. L.1995: The nature, distribution and formation of pans in arid zones . Earth-Science Reviews38, 1-69 .
30.
Gradziński, R. , Baryla, J. , Doktor, M. , Gmur, D. , Gradziński, M. , Kedzior, A. , Paszkowski, M. , Soja, R. , Zieliński, T. and Żurek, S.2003: Vegetation-controlled modern anastomosing system of the upper Narew River (NE Poland) and its sediments . Sedimentary Geology157, 253-276 .
31.
Gumbricht, T. , McCarthy, T. S. , McCarthy, J. , Roy, D. , Frost, P. E. and Wessels, K.2002: Remote sensing to detect sub-surface peat fires and peat fire scars in the Okavango Delta, Botswana . South African Journal of Science98, 351-358 .
32.
Gumbricht, T. , McCarthy, T. S. and Merry, C. L.2001: The topography of the Okavango Delta, Botswana, and its tectonic and sedimentological implications . South African Journal of Geology104, 243-264 .
33.
Gumnior, M. and Thiemeyer, H.2003: Holocene flu-vial dynamics in the NE Nigerian savanna: some preliminary interpretations . Quaternary International111, 51-58 .
34.
Helgren, D. M.1979: Rivers of diamonds: an alluvial history of the lower Vaal basin, South Africa. Research Paper 185. Chicago: Department of Geography, University of Chicago .
35.
Hesse, P. , Ralph, T. and Yonge, D. 2005: Dryland wet-lands: the Holocene response of inland rivers in Australia . Abstract Book, Drylands: Linking Landscape Processes to Sedimentary Environments, Joint BGRG/BSRG International Conference, 2-4 February 2005, Geological Society, London, 54-54 .
36.
Higgins, S. I. , Coetzee, M. A. S. , Marneweck, G. C. and Rogers, K. H.1996: The Nyl River floodplain, South Africa, as a functional unit of the landscape: a review of current information . African Journal of Ecology34, 131-145 .
37.
Higgins, S. I. , Rogers, K. H. and Kemper, J.1997: A description of the functional vegetation pattern of a semi-arid floodplain, South Africa . Plant Ecology129, 95-101 .
38.
Hollis, G. E. , Adams, W. M. and Aminu-Kano, M. , editors, 1994: The Hadejia-Nguru wetlands: environment, economy and sustainable use of a Sahelian flood-plain wetland. Gland, Switzerland, and Cambridge: IUCN Wetlands Programme .
39.
Hughes, F. M. R.1996: Wetlands. In Adams, W. M. , Goudie, A. S. and Orme, A. R. , editors, The physical geography of Africa, Oxford: Oxford University Press , 267-286.
40.
Jacobberger, P. A.1987: Geomorphology of the upper inland Niger delta . Journal of Arid Environments13, 95-112 .
41.
Jacobberger, P. A.1988a: Drought-related changes to geomorphologic processes in central Mali . Geological Society of America Bulletin100, 351-361 .
42.
Jacobberger, P. A.1988b: Mapping abandoned river channels in Mali through directional filtering of Thematic Mapper data . Remote Sensing of the Environment26, 161-170 .
43.
Jones, L. S. and Harper, J. T.1998: Channel avulsions and related processes, and large-scale sedimentation patterns since 1875, Rio Grande, San Luis Valley, Colorado . Geological Society of America Bulletin110, 411-421 .
44.
Jurmu, M. C.2002: A morphological comparison of narrow, low-gradient streams traversing wetland environments to alluvial streams . Environmental Management30, 831-856 .
45.
Jurmu, M. C. and Andrle, R.1997: Morphology of a wetland stream . Environmental Management21, 921-941 .
46.
Knighton, A. D. and Nanson, G. C.1994: Waterholes and their significance in the anastomosing channel system of Cooper Creek, Australia . Geomorphology9, 311-324 .
47.
Knighton, A. D. and Nanson, G. C.2000: Waterhole form and process in the anastomosing channel system of Cooper Creek, Australia . Geomorphology35, 101-117 .
48.
Liutkus, C. M. and Ashley, G. M.2003: Facies model of a semiarid freshwater wetland, Olduvai Gorge, Tanzania . Journal of Sedimentary Research73, 691-705 .
Makaske, B. , Smith, D. G. and Berendsen, H. J. A.2002: Avulsions, channel formation and floodplain sedimentation rates of the anastomosing upper Columbia River, British Columbia, Canada . Sedimentology49, 1049-1071 .
51.
Marren, P. M. , McCarthy, T. S. , Tooth, S. , Brandt, D. , Stacey, G. C. , Leong, A. and Spottiswoode, B.2006: A comparison of mud- and sand-dominated meanders in a downstream coarsening reach of the mixed bedrock-alluvial Klip River, eastern Free State, South Africa . Sedimentary Geology, 190, 213-226 .
52.
McCarthy, T. S.1993: The great inland deltas of Africa . Journal of African Earth Sciences17, 275-291 .
53.
McCarthy, T. S. and Ellery, W. N.1995: Sedimentation on the distal reaches of the Okavango fan, Botswana, and its bearing on calcrete and silcrete (ganister) formation . Journal of Sedimentary ResearchA65, 77-90 .
54.
McCarthy, T. S. and Ellery, W. N.1997: The fluvial dynamics of the Maunachira channel system, northeastern Okavango Swamps, Botswana . Water SA23, 115-126 .
55.
McCarthy, T. S. and Ellery, W. N.1998: The Okavango Delta . Transactions of the Royal Society of South Africa53, 157-182 .
56.
McCarthy, T. S. and Hancox, P. J.2000: Wetlands. In Partridge, T. C. and Maud, R. R. , editors, The Cenozoic of southern Africa, Oxford: Oxford University Press , 218-235.
57.
McCarthy, T. S. , Ellery, W. N. and Bloem, A.1998a: Some observations on the geomorphological impact of hippopotamus (Hippopotamus amphibius L.) in the Okavango Delta, Botswana . African Journal of Ecology36, 44-56 .
58.
McCarthy, T. S. , Ellery, W. N. and Dangerfield, J. M.1998b: The role of biota in the initiation and growth of islands on the floodplain of the Okavango alluvial fan, Botswana . Earth Surface Processes and Landforms23, 291-316 .
59.
McCarthy, T. S. , Ellery, W. N. and Gieske, A.1994: Possible ground water pollution by sewage effluent at camps in the Okavango Delta: suggestions for its prevention . Botswana Notes and Records26, 129-138 .
60.
McCarthy, T. S. , Ellery, W. N. and Stanistreet, I. G.1992: Avulsion mechanisms on the Okavango fan, Botswana: the control of a fluvial system by vegetation . Sedimentology39, 779-795 .
61.
McCarthy, T. S. , Ellery, W. N. and Stanistreet, I. G.1993a: Lakes of the north eastern region of the Okavango Swamps, Botswana . Zeitschrift für Geomorphologie37, 273-294 .
62.
McCarthy, T. S. , Green, R. W. and Franey, N. J.1993b: The influence of neo-tectonics on water dispersal in the northeastern regions of the Okavango swamps, Botswana . Journal of African Earth Sciences17, 23-32 .
63.
McCarthy, T. S. , Smith, N. D. , Ellery, W. N. and Gumbricht, T.2002: The Okavango Delta - semi-arid alluvial-fan sedimentation related to incipient rifting. In Renaut, R. W. and Ashley, G. M. , editors, Sedimentation in continental rifts, SEPM (Society for Sedimentary Geology) Special Publication 73, 179-193.
64.
McCarthy, T. S. , Stanistreet, I. G. , Cairncross, B. , Ellery, W. N. , Ellery, K. , Oelofse, R. and Grobicki, T. S. A.1988: Incremental aggradation on the Okavango Delta-fan, Botswana . Geomorphology1, 267-278 .
65.
McCarthy, T. S. , Tooth, S. , Brandt, D. , Marren, P. and Hancox, P. J.2004: On the origin of the Nylsvlei wetland. In Abstracts, Geosciences Africa 2004, University of the Witwatersrand , 12-16 July 2004, 435-436.
66.
McFarlane, M. J. , Eckardt, F. D. , Ringrose, S. , Coetzee, S. H. and Kuhn, J. R.2005: Degradation of linear dunes in Northwest Ngamiland, Botswana and the implications for luminescence dating of periods of aridity . Quaternary International135, 83-90 .
67.
Middleton, N. J. and Thomas, D. S. G.1997: World atlas of desertification (second edition). London: UNEP/Edward Arnold .
68.
Midgley, D. C. , Pitman, W. V. and Middleton, B. J.1994: Surface water resources of South Africa 1990, volume II. Pretoria: Water Research Commission .
69.
Mitsch, W. J. and Gosselink, J. G.2000: Wetlands (third edition). New York: Wiley , 936-936 pp.
70.
Moore, A. E.1999: A reappraisal of epeirogenic flexure axes in southern Africa . South African Journal of Geology102, 363-376 .
71.
Moore, A. E. and Larkin, P. A.2001: Drainage evolution in south-central Africa since the breakup of Gondwana . South African Journal of Geology104, 47-68 .
72.
Morgan, C.S. 1996: The application of digital terrain models and a geographic information system in the modelling of flooding in the Nyl river floodplain. Unpublished MSc thesis, University of the Witwatersrand.
73.
Morozova, G. S. and Smith, N. D.2000: Holocene avulsion styles and sedimentation patterns of the Saskatchewan River, Cumberland Marshes, Canada . Sedimentary Geology130, 81-105 .
74.
Mulamoottil, G. , Warner, B. G. and McBean, E. A. , editors 1996: Wetlands: environmental gradients, boundaries, and buffers. New York: Lewis Publishers .
75.
Nanson, G. C. , East, T. J. and Roberts, R. G.1993: Quaternary stratigraphy, geochronology and evolution of the Magela Creek catchment in the monsoon tropics of northern Australia . Sedimentary Geology83, 277-302 .
76.
Nduru, M.2004: How wetlands will save SA’s water supply. Retrieved 15 May 2004 from Mail and Guardian Online, http://www.mg.co.za/Content/13.asp?ao%20=%2066352
77.
Noble, R. G. and Hemens, J.1978: Inland water ecosystems in South Africa - a review of research needs. South African National Scientific Programme Report 34. Pretoria: CSIR .
78.
O’Brien, P. E. and Burne, R. V.1994: The Great Cumbung Swamp - terminus of the low-gradient Lachlan River, eastern Australia . AGSO Journal of Australian Geology and Geophysics15, 223-233 .
79.
Partridge, T. C. and Scott, L.2000: Lakes and pans. In Partridge, T. C. and Maud, R. R. , editors, The Cenozoic of southern Africa, Oxford: Oxford University Press , 145-161.
80.
Rech, J. A. and Latorre, C. 2004: Climatic controls on fluvial cut- and-fill cycles in drainages with in-stream wetlands in the central Andes . Abstract H51A-1103. American Geophysical Union Fall Meeting, 13-17 December 2004, San Francisco.
81.
Rodnight, H. , Duller, G. A. T. , Tooth, S. and Wintle, A. G.2005: Optical dating of a scroll-bar sequence on the Klip River, South Africa, to derive the lateral migration rate of a meander bend . The Holocene15, 802-811 .
82.
Rodnight, H. , Duller, G. A. T. , Wintle, A. G. and Tooth, S.2006: Assessing the reproducibility and accuracy of optical dating of fluvial deposits . Quaternary Geochronology, 1, 109-120 .
83.
Rogers, A. W.1910: Verneuk Pan . Transactions of the Royal Society of South Africa2, 79-82 .
84.
Rogers, K. H.1995: Riparian wetlands. In Cowan, G. I. , editor, Wetlands of South Africa, South African Wetlands Conservation Programme Series, Pretoria: Department of Environmental Affairs and Tourism , 41-52.
85.
Rogers, K. H.1997: Freshwater wetlands. In Cowling, R. M. , Richardson, D. M. and Pierce, S. M. , editors, Vegetation of southern Africa, Cambridge: Cambridge University Press , 322-347.
86.
Scholes, R. J. and Walker, B. H.1993: An African savanna: synthesis of the Nylsvley study. Cambridge: Cambridge University Press .
87.
Schulze, R. E.1997a: South African atlas of agrohydrology and -climatology. Report TT82/96. Pretoria: Water Research Commission .
88.
Schulze, R. E.1997b: Climate. In Cowling, R. M. , Richardson, D. M. and Pierce, S. M. , editors, Vegetation of southern Africa, Cambridge: Cambridge University Press , 21-42.
89.
Scoones, I.1991: Wetlands in drylands: key resources for agricultural and pastoral production in Africa . Ambio20, 366-371 .
90.
Scott, D. A. and Jones, T. A.1995: Classification and inventory of wetlands: a global overview . Vegetatio118, 3-16 .
91.
Scott, L. , Holmgren, K. , Talma, A. S. , Woodborne, S. and Vogel, J. C.2003: Age interpretation of the Wonderkrater spring sediments and vegetation change in the Savanna Biome, Limpopo Province, South Africa . South African Journal of Science99, 484-488 .
92.
Semeniuk, C. A. and Semeniuk, V.1995: A geomorphic approach to global classification for inland wet-lands . Vegetatio118, 103-124 .
93.
Shaw, P. A. and Thomas, D. S. G.1997: Pans, playas and salt lakes. In Thomas, D. S. G. , editor, Arid zone geomorphology: process, form and change in drylands (second edition), Chichester: Wiley , 293-317.
94.
Shaw, P. A. , Bateman, M. D. , Thomas, D. S. G. and Davies, F.2003: Holocene fluctuations of Lake Ngami, Middle Kalahari: chronology and responses to climate change . Quaternary International111, 23-35 .
95.
Smith, N. D. , McCarthy, T. S. , Ellery, W. N. , Merry, C. L. and Rüther, H.1997: Avulsion and anastomosis in the panhandle region of the Okavango Fan, Botswana . Geomorphology20, 49-65 .
96.
Sedimentary Geology85, 115-133 .
97.
Tarboton, W. R.1987: The Nyl floodplain: its significance, phenology and conservation status. In Walmsley, R. D. and Botten, M. L. , editors, The ecology and conservation of wetlands in South Africa, Ecosystems Programme Occasional Report 28, Pretoria: Foundation for Research Development .
98.
Taylor, G.M. 1976: The Barwon River, New South Wales: a study of basin fill by a low gradient stream in a semi-arid climate. Unpublished PhD thesis, Australian National University.
99.
Thomas, D. S. G.1997: Arid environments: their nature and extent. In Thomas, D. S. G. , editor, Arid zone geo-morphology: process, form and change in drylands (second edition), Chichester: Wiley , 3-12.
100.
Thomas, D. S. G. and Shaw, P. A.1988: Late Cainozoic drainage evolution in the Zambezi Basin: geomorpho-logical evidence from the Kalahari rim . Journal of African Earth Sciences7, 611-618 .
101.
Thomas, D. S. G. and Shaw, P. A.1991: The Kalahari environment. Cambridge: Cambridge University Press .
102.
Thomas, D. S. G. , O’Connor, P. W. , Bateman, M. D. , Shaw, P. A. , Stokes, S. and Nash, D. J.2000: Dune activity as a record of late Quaternary aridity in the Northern Kalahari: new evidence from northern Namibia interpreted in the context of regional arid and humid chronologies . Palaeogeography, Palaeoclimatology, Palaeoecology156, 243-259 .
103.
Tooth, S.1999: Floodouts in central Australia. In Miller, A. J. and Gupta, A. , editors, Varieties of fluvial form, Chichester: Wiley , 219-247.
104.
Tooth, S.2002: Waterholes: wetlands in drylands? Retrieved 14 November 2005 from http://www.abdn.ac.uk/%7Egmi196/DrylandRivers/feature/features_index.php
105.
Tooth, S.2004: Floodout. In Goudie, A. S. , editor, Encyclopedia of geomorphology (volume 1), London: Routledge , 380-381.
106.
Tooth, S. and McCarthy, T. S.2004: Controls on the transition from straight to meandering channels in the wetlands of the Okavango Delta, Botswana . Earth Surface Processes and Landforms29, 1627-1649 .
107.
Tooth, S. , Brandt, D. , Hancox, P. J. and McCarthy, T. S.2004: Geological controls on alluvial river behaviour: a comparative study of three rivers on the South African Highveld . Journal of African Earth Sciences38, 79-97 .
108.
Tooth, S. , McCarthy, T. S. , Brandt, D. , Hancox, P. J. and Morris, R.2002a: Geological controls on the formation of alluvial meanders and floodplain wetlands: the example of the Klip River, eastern Free State, South Africa . Earth Surface Processes and Landforms27, 797-815 .
109.
Tooth, S. , McCarthy, T. S. , Hancox, P. J. , Brandt, D. , Buckley, K. , Nortje, E. and McQuade, S.2002b: The geomorphology of the Nyl River and floodplain in the semi-arid Northern Province, South Africa . South African Geographical Journal84, 226-237 .
110.
United Nations Environment Programme (UNEP)1992: World atlas of desertification. Sevenoaks: Edward Arnold .
111.
Unmack, P. J.2001: Fish persistence and fluvial geomorphology in central Australia . Journal of Arid Environments49, 653-669 .
112.
van der Graaff, W. J. E , Crowe, R. W. A. , Bunting, J. A. and Jackson, M. J.1977: Relict Early Cainozoic drainages in arid Western Australia . Zeitschrift für Geomorphologie21, 379-400 .
113.
van Rooyen, T. H. and Burger, R. du T.1973: Physiographic features of the central Orange River basin, with a note on pan formation . South African Geographer4, 218-227 .
114.
von der Heyden, C. J.2004: The hydrology and hydro-geology of dambos: a review . Progress in Physical Geography28, 544-564 .
115.
Wasson, R. J.1983: The Cainozoic history of the Strzelecki and Simpson dunefields (Australia), and the origin of the desert dunes . Zeitschrift für Geomorphologie Supplementband 45, 85-115 .
116.
Wellington, J. H.1938: The Kunene River and the Etosha Plain . South African Geographical Journal20, 21-33 .
117.
Wellington, J. H.1945: Notes on the drainage of the Western Free State Sandveld . South African Geographical Journal27, 73-77 .
118.
Wellington, J. H.1955: Southern Africa: a geographical study. Volume I: physical geography. Cambridge: Cambridge University Press .
119.
Williams, A. R.1979: Vegetation and stream pattern as indicators of water movement on the Magela flood-plain, Northern Territory . Australian Journal of Ecology4, 239-247 .
120.
Winter, T. C.2000: The vulnerability of wetlands to climate change: a hydrologic landscape perspective . Journal of the American Water Resources Association36, 305-311 .
121.
Woodroffe, C. D. , Mulrennan, M. E. and Chappell, J.1993: Estuarine infill and coastal progradation, southern van Diemen Gulf, northern Australia . Sedimentary Geology83, 257-275 .
122.
Zierholz, C. , Prosser, I. P. , Fogarty, P. J. and Rustomji, P.2001: In-stream wetlands and their significance for channel filling and the catchment sediment budget, Jugiong Creek, New South Wales . Geomorphology38, 221-235 .
123.
Zoltai, S. C.1988: Wetland environments and classification. In Wetlands of Canada, National Wetlands Working Group and Canada Committee on Ecological Land Classification, Ottawa: Canadian Government Publications and Polyscience Publications Inc. , 3-26.
