An integrated, landscape based approach to model the formation and hydrological functioning of wetlands in semiarid headwater catchments of the Umzimvubu River, South Africa [Elektronische Ressource] / vorgelegt von Jörg Helmschrot

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• Publié par: friedrich-schiller-universitat_jena
• Publié le: 01 janvier 2006
• Nombre de lectures: 32
• Langue: English
• Poids de l'ouvrage: 23 Mo

Extrait

An integrated, landscape-based approach to model
the formation and hydrological functioning of wetlands
in headwater catchments of the Umzimvubu River,
South Africa








Dissertation

zur Erlangung des akademischen Grades doctor rerum naturalium
(Dr. rer. nat.)















vorgelegt dem Rat der Chemisch-Geowissenschaftlichen Fakultät
der Friedrich-Schiller-Universität Jena

von Dipl.-Geogr. Jörg Helmschrot
geboren am 28. Oktober 1969 in Gera




































Gutachter:

1. Prof. Dr. W.-A. Flügel (Friedrich-Schiller-Universität Jena)
2. Prof. Dr. R. Mäusbacher (Friedrich-Schiller-Universität Jena)
3. Prof. Dr. V. Hochschild (Eberhard-Karls-Universität Tübingen)

Tag der öffentlichen Verteidigung: 1. November 2006 I
ACKNOWLEDGEMENTS
This dissertation would not have been written without the encouragement and a tremendous
amount of support of a large number of people.
First of all, I would like to thank my supervisors Prof. Dr. Wolfgang-Albert Flügel and Prof.
Dr. Roland Mäusbacher, who supported and guided me with their valuable motivation, criti-
cism and fruitful discussions during the time of research for this dissertation.
Acknowledgements are also given to Dr. Simon Lorentz (University of KwaZulu-Natal, South
Africa) for his great scientific help as well as continuous assistance and logistical support in the
field during the past nine years. Prof. Roland Schulze and Prof. Heinz Beckedahl (SBEEH
Pietermaritzburg, South Africa) are acknowledged for their scientific contributions and discus-
sions. Without the remarkable willingness of Peter Gardiner (Mondi Forests Ltd.) to logisti-
cally support these studies, the field work would never have been done as continuously and
successfully as it was over years. In addition, I thank Dr. Peter Dye (CSIR, South Africa) for
his valuable contributions to the plant growth modeling.
I respectfully acknowledge Prof. George Leavesley, Steven Markstrom and Roland Viger from
the USGS (Denver, USA) for their great support in order to get the PRMS model running as
well as to modify and improve the model for specific project needs.
I really appreciate my colleagues at the Department of Geography for their continuous help
and discussions to enrich this dissertation. I’m extremely thankful to Dr. Martin ‘Leo’ Herold
and Dr. Martin Klenke (who moved to Hannover) for their continuing friendship and help
during the last years. I also would like to thank Christin Hilbich for an impressive field cam-
paign and her commitment and stimulating discussions aiming to develop the landscape
model. Special thanks are given to Dr. Ulrike Bende-Michl, Roman Gerlach and Antje Gude
for their valuable comments to improve this dissertation. Thank you to our system administra-
tor Rainer ‘Hoffi’ Hoffmann for keeping the systems running and our secretary Anita Martin
who managed the administrative necessities. Acknowledgements are also given to Dr. Gerhard
Daut, Dr. Heike Schneider, Dr. Peter Krause, Dr. Maurizio Santoro and Dr. Jussi Baade for
their help and inspiring discussions which certainly improved this thesis. In addition, I would
like to acknowledge the tremendous work which was done by my student assistants Helen
Dahlke, Hannes Müller Schmied, Annemarie Ebert, Dorothee Kemnitz, Sophie Biskop, Kla-
rissa Kornhaß, Frank Bäse, and Jens Napierkowski.
I’m really thankful to Andrew ‘Wagga Boy Krausey’ Krause (Australia), Dr. Christopher
Woltemade (USA) and Rob Farrell (USA) who reviewed parts of the text and enriched this
thesis with their valuable comments and edits.
Finally, I would like to appreciate the patience, help, and tolerance of my family, my girlfriend
Ines and my friends who saw me a little less frequently, since I have spent so much time in
South Africa, my office or at conferences elsewhere, but unfortunately not with them.
This PhD study has been carried out as part of the research project “Integriertes Land-
schaftsmodell für Feuchtgebiete” (“Integrated landscape model of wetlands”) which was
funded by the German Research Association (DFG).


Jena, July 2006 Jörg Helmschrot
II









III
ABSTRACT

An integrated, landscape-based approach to model the formation and hydrological
functioning of wetlands in semiarid headwater catchments of the Umzimvubu River,
South Africa

JÖRG HELMSCHROT

Wetlands are very important elements of the landscape in almost every environment. Address-
ing the continued loss of wetland area worldwide, wetlands are recognized as highly vulnerable
with regard to natural and anthropogenic system changes. Consequently, the research of their
natural and socio-economical functions, importance for the water and nutrient cycles and their
role as wildlife habitats received increasing scientific and public awareness in the past decades.
The landscape of the semi-arid Eastern Cape Province, South Africa, is characterized by the
occurrence of different types of palustrine wetlands. Intensive afforestation in the headwaters
of the Umzimvubu catchment since 1989 has changed downstream wetland characteristics,
but little attention was given to evaluate and quantify these impacts. Addressing this research
deficit, the main objectives of this dissertation are the development of an integrated, land-
scape-based research approach to improve the understanding of the formation, functioning
and dynamics of wetlands and the prognostic modeling and assessment of afforestation im-
pacts on these wetland systems.
The conceptual and methodological approach of this dissertation is based on three individual
aspects: i) observation and data mining; ii) integrated system analysis; and iii) system modeling
and assessment integrating empirical field studies, laboratory analysis, GIS and remote sensing
techniques, system analysis and process-oriented, plant growth and hydrological modeling,
This integrated research approach provides information regarding a generalized understanding
of dominant environmental processes at wetland and catchment scale and the impact of affor-
estation on wetland and basin hydrology.
By means of this effort three main wetland types, being different in terms of landscape posi-
tion, extent and size of the tributary catchment, soils, vegetation composition and hydrological
dynamics, could be identified. The hydrodynamics of plateau and slope wetlands are mainly
controlled by recharge mechanisms, while larger valley bottom wetlands are driven by inter-
linked ground-/surface water dynamics, discharge/recharge processes and direct rainfall input.
Coupling plant growth and hydrological modeling, it was found that wetland dynamics and
their landscape functions will be influenced by afforestation in terms of altered re-
charge/discharge mechanisms; reduced base flows addressed to increased interception losses
and reduced water retention capability as a result of net loss of wetland area. In addition, such
changes will affect environmental functions and biodiversity due to habitat loss and altera-
tions. Integrating the results and information of the present study, an integrated landscape
model was developed aiming to characterize wetland formation and emphasizing impacts of
human activities on past and recent wetland and landscape dynamics.

Keywords: wetlands, landscape model, hydrological modeling, afforestation, South Africa
IV
V
KURZFASSUNG

Ein integrierter, landschafts-basierter Ansatz zur Modellierung der Entstehung
und Dynamik von Feuchtgebieten in den semiariden Quelleinzugsgebieten des
Umzimvubu, Südafrika

A. EINLEITUNG UND MOTIVATION
Feuchtgebiete sind Ökosysteme, die weltweit verbreitet sind und ca. 6 % der Erdober-
fläche bedecken (GORE, 1983; MITSCH & GOSSELINK, 2000). Natürliche oder natur-
nahe Feuchtgebiete sind in der Regel im Übergangsbereich von terrestrischen und a-
quatischen Ökosystemen zu finden. Sie treten daher entweder als Küsten- bzw.
küstennahe Feuchtgebiete (z.B. Mangrovenwälder, Lagunen oder Marschen) oder In-
landsfeuchtgebiete (z.B. Moore, Feuchtwiesen, Auen oder Flachwasserseen) in Er-
scheinung. Künstlich angelegte Feuchtgebiete hingegen werden z.B. durch Reisfelder,
Fischaufzuchtteiche oder Abwasserkläranlagen repräsentiert. Die Landschaftsfunktio-
nen von Feuchtgebieten und deren Bedeutung für den Naturhaushalt werden in der
Literatur ausführlich diskutiert (z.B. CARTER et al., 1979; LUGO et al., 1990; MITSCH &
GOSSELINK, 2000; SUCCOW & JOOSTEN, 2001).
In Südafrika wird palustrinen Feuchtgebieten (Inlandsfeuchtgebieten), insbesondere in
den semi-ariden Regionen entlang der „Großen Randstufe“, eine zentrale Bedeutung
im reg