DInSAR-based monitoring of land subsidence related to groundwater over-exploitation: example from developing urban center of Nairobi, Kenya | Suivi par DInSAR de la subsidence du sol liée à la surexploitation des eaux souterraines : exemple du centre urbain en expansion de Nairobi, Kenya Monitoreo basado en DInSAR de la subsidencia del terreno relacionada con la sobreexplotación de las aguas subterráneas: ejemplo del centro urbano en desarrollo de Nairobi, Kenia 基于 DInSAR 的与地下水过量开采相关的地面沉降监测:以肯尼亚内罗毕正发展的城市为例 Monitoramento baseado no DInSAR da subsidência de terreno relacionada com a superexploração das águas subterrâneas: exemplo do centro urbano em desenvolvimento de Nairóbi, Quênia
2021
Sahadevan, Dinesh Kumar | Pandey, Anand Kumar
Over-exploitation of groundwater in many evolving urban settings causes ground subsidence and permanent loss of aquifer storage capacity. DInSAR (differential interferometric synthetic aperture radar) time series data from 2016 to 2019 were used to monitor and model the surface deformation around Nairobi, Kenya, where the water demand has exceeded the supply without capacity augmentation for over two decades. The aquifer system constitutes hard rock to semiconfined ash beds in volcanic terrain. The Small Baseline DInSAR technique identified the spatial pattern of subsidence and magnitude (line-of-sight (LOS) velocity), which exceeds 41 mm/year in the semiconfined aquifer towards the western-central part of Nairobi. The spatial distribution of subsidence is consistent with the groundwater level drop and probable compaction modeled using aquifer characteristics for 1950–2015. The Global Navigation Satellite System (GNSS) data at a station from 2007 to 2018 indicate a cumulative 4-cm subsidence which is comparable to ~2.5-cm LOS subsidence from the present study for 2016–2019. The correlation with other hydrological data suggests the aquifer is experiencing inelastic subsidence due to unsustainable groundwater extraction, putting a massive strain on Nairobi’s aquifer system. The present DInSAR based study establishes its effectiveness in the monitoring of groundwater over-exploitation-based subsidence and associated hazard to the aquifer in emerging urban centers.
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