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Groundwater Assessment and Monitoring in the Northeastern Part of Nigeria Using Microwave Remote Sensing
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Resumo(s)
As the human population continues to grow, the availability of surface water for convenient use is
becoming increasingly scarce (Yu Fang et al., 2019). The negative effects of climate change such as
drought has also been a major contributor to unavailability of surface water resources in certain
regions (Brandon et al., 2017). Due to these reasons and more, natural reserves such as groundwater
has become a primary and the most extensively used source of water (Brandon et al., 2017). The
primary source of groundwater is gotten from precipitation, with a significant amount of precipitation
in the presence of porous soils and with the help of gravity it infiltrates itself into the earth to form
Groundwater, this in turn forms aquifers which can and has been harnessed over and over again
through the construction of wells and boreholes and has been used for various purposes, including
drinking, agriculture, and other human activities for centuries. Groundwater is also a key component
of the water cycle; despite its invisibility it plays a crucial role in the ecosystem and the flow of
various water bodies. Monitoring and investigating its variations and availability is therefore crucial
for sustainability. Traditional methods such as geophysical and geo-electrical techniques have been
utilized to detect, monitor and investigate groundwater resource for decades and have no doubt shown
remarkable results, but these methods are not without limitations, they are expensive, timeconsuming, and in some cases limited in spatial coverage, therefore optimization is necessary for
progressiveness. New and more effective microwave-based techniques have been developed and
realized in recent times, they have shown to be promising in handling complex hydrological
investigations and observations, one of such technique is the Interferometric Synthetic Aperture
Radar (InSAR), which utilizes Sentinel-1 satellite images to assess land surface deformation. This
technique allows for mappings and investigations of groundwater variability over time in a particular
region by studying the subsidence or uplift pattern which could be associated with groundwater
recharge or depletion (Teije et al., 2018). Another important instrument for water management is the
Gravity Recovery and Climate Experiment (GRACE) mission. GRACE measures global spatial mass
changes caused by gravitational anomalies by using microwave k-band ranging sensor,
accelerometers, and global positioning system receivers. GRACE is particularly important for water
management as water has mass and its volume varies over time, because of this GRACE can identify
and measure its variations. It is also the only satellite that can analyse Terrestrial Water Storage
(TWS), which comprises of all the water storages on earth. Another technique worthy of mention is
the Standardised Precipitation Evapotranspiration Index (SPEI), this index makes use of hydroclimatological parameters to estimate and investigate drought conditions in regions where it is
integrated. Drought could occur due to seasonal and annual variabilities of precipitation and or
temperatures which in turn can be as a result of climate change. Sentinel-1 and GRACE complement
each other and have varying sensitivity to aquifer system change. This project employed data from
both satellites to monitor and evaluate groundwater variability in the north eastern region of Nigeria.
Also, due to unavailability of in-situ data for validations and results comparisons, I considered the
hydro-climatology of this region and investigated the drought situation over the specified years to
strengthen my findings.
Descrição
Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Geospatial Technologies