Radar altimetry of water level variability in the Inner Delta of Niger River

Goı̈ta, Kalifa; Diepkilé, Adama Telly

doi:10.1109/igarss.2012.6352422

Cited by 5 publications

(5 citation statements)

References 5 publications

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“…For water studies over land, radar altimeter derived water levels have been shown to be precise enough and are now used for systematic monitoring of large rivers, lakes, wetlands and floodplains (e.g., Birkett, 1995Birkett, , 1998Frappart et al, 2005Frappart et al, , 2012; Santos da Silva et al, 2010;Crétaux et al, 2011;Goita and Diepkile, 2012).…”

Section: Time Variations Of Altimetry-based Water Levels In the Niger Inner Deltamentioning

confidence: 99%

Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

Frappart

Fatras

Mougin

et al. 2015

Physics and Chemistry of the Earth, Parts A/B/C

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International audienceThis study presents a comprehensive comparison of radar altimetry signatures at Ka-, Ku-, C-, and S-bands using SARAL, ENVISAT and Jason-2 data over the major bioclimatic zones, soil and vegetation types encountered in West-Africa, with an emphasis on the new information at Ka-band provided by the recently launched SARAL–Altika mission. Spatio-temporal variations of the radar altimetry responses were related to changes in surface roughness, land cover and soil wetness. Analysis of time series of backscattering coefficients along the West African bioclimatic gradient shows that radar echoes at nadir incidence are well correlated to soil moisture in semi-arid savannah environments. Radar altimeters are able to detect the presence of water even under a dense canopy cover at all frequencies. But only measurements at Ka-band are able to penetrate underneath the canopy of non-inundated tropical evergreen forests

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Section: Time Variations Of Altimetry-based Water Levels In the Niger Inner Deltamentioning

confidence: 99%

Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

Frappart

Fatras

Mougin

et al. 2015

Physics and Chemistry of the Earth, Parts A/B/C

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“…Several studies already used altimetry-based water levels to better understand spatio-temporal dynamics of the flood in this region [20][21][22] and to estimate river discharges [23,24]. The IND was chosen as study area as it is densely covered with (i) in situ gauge stations whose records are available over the whole high-precision altimetry era and (ii) cross-sections between altimetry ground-tracks from different missions and rivers of various widths.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the Performances of Radar Altimetry Missions from ERS-2 to Sentinel-3A over the Inner Niger Delta

et al. 2018

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Radar altimetry provides unique information on water stages of inland hydro-systems. In this study, the performance of seven altimetry missions, among the most commonly used in land hydrology (i.e., European Remote-Sensing Satellite-2 (ERS-2), ENVIronment SATellite (ENVISAT), Satellite with Argos and ALtika (SARAL), Jason-1, Jason-2, Jason-3 and Sentinel-3A), are assessed using records from a dense in situ network composed of 19 gauge stations in the Inner Niger Delta (IND) from 1995 to 2017. Results show an overall very good agreement between altimetry-based and in situ water levels with correlation coefficient (R) greater than 0.8 in 80% of the cases and Root Mean Square Error (RMSE) lower than 0.4 m in 48% of cases. Better agreement is found for the recently launched missions such as SARAL, Jason-3 and Sentinel-3A than for former missions, indicating the advance of the use of the Ka-band for SARAL and of the Synthetic-aperture Radar (SAR) mode for Sentinel-3A. Cross-correlation analysis performed between water levels from the same altimetry mission leads to time-lags between the upstream and the downstream part of the Inner Niger Delta of around two months that can be related to the time residence of water in the drainage area.

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“…1). Its floodable area is estimated at 32 000 km 2 (Goita and Diepkile, 2012;Mahé et al, 2009;Seiler et al, 2009;Zwarts et al, 2005). The Delta presents a rather particular ecological environment by the fact that it separates two zones with very precarious climatic conditions: on the one hand, the desert Sahara dominated by sand dunes, and on the other hand, the Sahel which is characterized by recurrent droughts.…”

Section: The Inner Niger Deltamentioning

confidence: 99%

“…Locations of in-situ gauges, and VS from Sentinel-3A and B are represented using black dots, red and green triangles, respectively. Goita and Diepkile, 2012;Normandin et al, 2018). In this study, RA-based water levels defined at the cross-sections of Sentinel-3A and 3B ground-tracks and river and floodplains in the IND were compared to in-situ water stages.…”

Section: Introductionmentioning

confidence: 99%

Validation of the altimetry-based water levels from Sentinel-3A and B in the Inner Niger Delta

et al. 2021

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Abstract. The comprehension of water level fluctuations and the sustainability of the Inner Niger River Delta (IND) is a major concern for the scientific community, but also for the local population. Located in the centre of Mali, the heart of the Sahel, the delta is characterised by a floodable area of more than 32 000 km2 during the rainy season, which contributes very strongly to the vitality of local ecosystem, and is consequently classified as a Ramsar site under the international Convention for Wetlands. In addition, the Delta acts as an environmental and socio-economic development barometer for the entire sub-region. Nowadays, we can observe an increasing fragility of the delta due to climate change, desertification and human activities, and justifies the need for permanent monitoring. The present study is based on the recent successes of radar altimetry, originally designed to monitor the dynamics topography of the ocean, and now very frequently used to retrieve inland water levels, of lakes, rivers, and wetlands. Previous studies evaluated the performances of several radar altimetry missions including Low Resolution Mode (LRM) (Topex-Poseidon, Jason-1/2/3, ERS-2, ENVISAT, and SARAL, and Synthetic Aperture Radar (SAR) Sentinel-3A missions for water level retrievals over 1992–2017. More than 50 times series of water levels were build at the crossing between water bodies and Sentinel-3A and 3B over 2016–2020. Twenty-four comparisons between in-situ and altimetry-based time-series of water levels were achieved over the IND. RMSE generally lower than 0.7 m and r higher than 0.9 were obtained.

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Radar altimetry of water level variability in the Inner Delta of Niger River

Cited by 5 publications

References 5 publications

Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

Evolution of the Performances of Radar Altimetry Missions from ERS-2 to Sentinel-3A over the Inner Niger Delta

Validation of the altimetry-based water levels from Sentinel-3A and B in the Inner Niger Delta

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