The evaluation and quantification of the drought propagation process using satellite earth observation products.
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Date
2022
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Abstract
Droughts can be categorized in four types namely, meteorological, agricultural, hydrological and
socio-economic drought. Droughts have the potential to occur either as an isolated event, mutually
exclusive event or through the progression from one form to another. The use of drought indices
were recognized as an approach capable evaluating and monitoring the characteristics of the
different drought types. The aim of this study is to evaluate and quantify drought characteristics
as it evolves and propagates form meteorological to agricultural drought, within two climatically
different regions within South Africa, namely the uMngeni Catchment and the Breede-Overberg
Catchment. These areas generally have insufficient networks of ground-based observations to
provide continuous and long-term data. Therefore, Satellite Earth Observation (SEO) data and
Google Earth Engine (GEE) were utilized. The Standardized Precipitation Index (SPI) was
selected to quantify meteorological drought, whilst the Standardized Precipitation
Evapotranspiration Index (SPEI) and Vegetation Health Index (VHI) was chosen to assess
agricultural drought at both of the selected sites. The methodology undertaken firstly involved
validating the SEO data against in-situ data. Thereafter, historical droughts were calculated by the
SPI and SPEI indices at various timescales. Assessments were then conducted to determine the
applicability of satellite based drought index VHI on quantifying agricultural drought conditions.
The final assessment involved conducting propagation analysis between the drought indices. The
findings of this study indicated that SEO have the potential to be utilized in the collection and
monitoring of drought conditions. VHI was recognized to be scale dependent index, especially
when considering averaging values. The findings of this study further suggested that the uMngeni
region was more susceptible to the impacts associated with meteorological droughts characteristics
whilst the Breede-Overberg region was more susceptible to the impacts associated with
agricultural drought characteristics. Understanding the impacts and characteristics associated with
the drought propagation process may further provide theoretical knowledge that can be used to
facilitate more informed disaster, water and agricultural management and mitigation strategies to
be implemented. If decision makers were to only consider drought using meteorological
assessments for management decisions, the resulting strategies produced may be misleading as the
impacts of an agricultural drought event may still be persistent.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.