Indiana University-Purdue University Indianapolis (IUPUI) / Drylands cover 40% of the earth’s terrestrial surface supporting over 2 billion
people, the majority of whom reside in developing nations characterised by high population
growth rates. This imposes pressure on the already limited water resources and in some
dryland regions such as southern Africa, the origins and dynamics of rainfall are not well
understood. Research has also tended to focus on factors limiting (e.g., rainfall) than
sustaining productivity in drylands. However, non-rainfall water (NRW) e.g., fog and dew
can supplement and/or exceed rainfall in these environments and could potentially be
exploited as potable water resources. Much remains unknown in terms of NRW formation
mechanisms, origins, evolution, potability and potential impact of global climate change
on these NRW dependent ecosystems.
Using Namibia as a proxy for drylands and developing nations, this dissertation
applies stable isotopes of water (δ2H, δ18O, δ17O and d-excess), cokriging and trajectory
analysis methods to understand ecohydrological processes. Results suggest that locally
generated NRW may be a regular occurrence even in coastal areas such as the Namib
Desert, and that what may appear as a single fog event may consist of different fog types
co-occurring. These results are important because NRW responses to global climate change
is dependent on the source, groundwater vs. ocean, and being able to distinguish the two
will allow for more accurate modelling. I also demonstrate, that fog and dew formation are
controlled by different fractionation processes, paving the way for plant water use strategy
studies and modelling responses to global climate change. The study also suggests that
current NRW harvesting technologies could be improved and that the potability of this
water could raise some public health concerns related to trace metal and biological
contamination. At the same time, the dissertation concludes that global precipitation
isoscapes do not capture local isotope variations in Namibia, suggesting caution when
applied to drylands and developing nations. Finally, the dissertation also reports for the
first time, δ17O precipitation results for Namibia, novel isotope methods to differentiate synoptic from local droughts and suggests non-negligible moisture contributions from the
Atlantic Ocean due to a possible sub-tropical Atlantic Ocean dipole.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/18093 |
| Date | 12 1900 |
| Creators | Kaseke, Kudzai Farai |
| Contributors | Wang, Lixin, Jacinthe, Pierre Andre, Gilhooly, William P., Wilson, Jeffrey, Soderberg, Keir |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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