Niger discharge from radar altimetry: bridging gaps between gauge and altimetry time series

Schröder, Stefan; Springer, Anne; Kusche, Jürgen; Uebbing, Bernd; Fenoglio-Marc, Luciana; Diekkrüger, Bernd; Poméon, Thomas

doi:10.5194/hess-23-4113-2019

Cited by 10 publications

(6 citation statements)

References 49 publications

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“…Michailovsky and Bauer-Gottwein ( 2014 ) used ENVIronment SATellite (ENVISAT)-derived water level variations along the Zambezi River and obtained a root-mean-square error (RMSE) of 32–72 cm with respect to in situ gauge data. Evaluations have also been reported over the Congo (Becker et al 2014 ; Paris et al 2022 ), the Nile (Eldardiry and Hossain 2019 ), the Niger (Schröder et al 2019 ) and the Ogooué river basins (Bogning et al 2018 ), with relative error and uncertainties in the same range as for other basins worldwide (Frappart et al 2006 ; Da Silva et al 2010 ; Papa et al 2012b ). Normandin et al ( 2018 ), focusing over the Niger River, is probably the most comprehensive evaluation of the performance of altimetry missions over Africa, assessing seven satellite missions (i.e., European Remote Sensing Satellite-2 (ERS-2), ENVISAT, Satellite with Argos and ALtika (SARAL), Jason-1, Jason-2, Jason-3 and Sentinel-3A), against in situ records at 19 gauging stations in the Inner Niger Delta (IND) from 1995 to 2017.…”

Section: Observing Surface Waters From Space In Africamentioning

confidence: 94%

Water Resources in Africa under Global Change: Monitoring Surface Waters from Space

et al. 2022

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The African continent hosts some of the largest freshwater systems worldwide, characterized by a large distribution and variability of surface waters that play a key role in the water, energy and carbon cycles and are of major importance to the global climate and water resources. Freshwater availability in Africa has now become of major concern under the combined effect of climate change, environmental alterations and anthropogenic pressure. However, the hydrology of the African river basins remains one of the least studied worldwide and a better monitoring and understanding of the hydrological processes across the continent become fundamental. Earth Observation, that offers a cost-effective means for monitoring the terrestrial water cycle, plays a major role in supporting surface hydrology investigations. Remote sensing advances are therefore a game changer to develop comprehensive observing systems to monitor Africa’s land water and manage its water resources. Here, we review the achievements of more than three decades of advances using remote sensing to study surface waters in Africa, highlighting the current benefits and difficulties. We show how the availability of a large number of sensors and observations, coupled with models, offers new possibilities to monitor a continent with scarce gauged stations. In the context of upcoming satellite missions dedicated to surface hydrology, such as the Surface Water and Ocean Topography (SWOT), we discuss future opportunities and how the use of remote sensing could benefit scientific and societal applications, such as water resource management, flood risk prevention and environment monitoring under current global change. Article Highlights The hydrology of African surface water is of global importance, yet it remains poorly monitored and understood Comprehensive review of remote sensing and modeling advances to monitor Africa’s surface water and water resources Future opportunities with upcoming satellite missions and to translate scientific advances into societal applications

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Section: Observing Surface Waters From Space In Africamentioning

confidence: 94%

Water Resources in Africa under Global Change: Monitoring Surface Waters from Space

et al. 2022

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“…Twenty-one discharge stations have missing values and incomplete records. This was due to the earlier discussed observed decrease in rainfall and discharge observation stations in west Africa Schröder et al 2019). The problem of missing data often hinders precise forecast of extreme events and sustainable policy interventions.…”

Section: Discussionmentioning

confidence: 99%

“…The Niger basin is ascribed with poorly documented historical hydrological data. There has been decrease in the amount of reliable rainfall stations since 1980 Oyerinde et al 2015) and discharge stations since 2000 (Schröder et al 2019). These has been identified to be due to underfunding of data collection agencies, lack of technical capacity and commitment, inaccessibility to remote gauge stations due to logistical and security challenges and equipment malfunction (Ekeu-Wei et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…These has been identified to be due to underfunding of data collection agencies, lack of technical capacity and commitment, inaccessibility to remote gauge stations due to logistical and security challenges and equipment malfunction (Ekeu-Wei et al 2018). Radar altimetry measurements was found to aid in improving observed discharge data but generating reliable altimetry-discharge rating curves is still unresolved (Schröder et al 2019). Temporal resolution of radar altimetry measurements due to satellite passing time also create challenges when there is consecutively gapped hydrological record (Ekeu-Wei et al 2018).…”

Section: Introductionmentioning

confidence: 99%

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Multi-variate infilling of missing daily discharge data on the Niger basin

Oyerinde

Lawin

Adeyeri

2021

Water Practice and Technology

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The Niger basin have experienced historical drought episodes and floods in recent times. Reliable hydrological modelling has been hampered by missing values in daily river discharge data. We assessed the potential of using the Multivariate Imputation by Chained Equations (MICE) to estimate both continuous and discontinuous daily missing data across different spatial scales in the Niger basin. The study was conducted on 22 discharge stations that have missing data ranging from 2% to 70%. Four efficiency metrics were used to determine the effectiveness of MICE. The Flow Duration Curves (FDC) of observed and filled data were compared to determine how MICE captured the discharge patterns. Mann-Kendall, Modified Mann-Kendall, Pettit and Sen's Slope were used to assess the complete discharge trends using the gap-filled data. Results shows that MICE near perfectly filled the missing discharge data with Nash-Sutcliffe Efficiency (NSE) range of 0.94–0.99 for the calibration (1992–1994) period. Good fits were obtained between FDC of observed and gap-filled data in all considered stations. All the catchments showed significantly increasing discharge trend since 1990s after gap filling. Consequently, the use of MICE in handling missing data challenges across spatial scales in the Niger basin was proposed.

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“…Through the requirements expressed by communities committed to water preservation, challenges of getting information in specific uncovered areas are being witnessed [5]. Significant indicators encompass water levels, water discharge and water volume changes of inland reservoirs and rivers [6][7][8][9][10][11][12]. Remote sensing, and more especially the field of altimetry, offers a privileged access to the quantification of water availability and the computation of the relative change in terms of water resources [13].…”

Section: Introductionmentioning

confidence: 99%

Challenges and Evolution of Water Level Monitoring towards a Comprehensive, World-Scale Coverage with Remote Sensing

Machefer¹,

Perpinyà-Vallès²,

Escorihuela³

et al. 2022

Preprint

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Surface water availability is a fundamental environmental variable to implement effective climate adaptation and mitigation plans, as expressed by scientific, financial and political stakeholders. Recently published requirements urge the need for homogenised access to long historical records at a global scale, together with the standardised characterisation of the accuracy of observations. While satellite altimeters offer world coverage measurements, existing initiatives and online platforms provide derived water level data. However, these are sparse, particularly in complex topographies. This study introduces a new methodology in two steps 1) teroVIR, a virtual station extractor for a more comprehensive global and automatic monitoring of water bodies, and 2) teroWAT, a multi-mission, interoperable water level processor, for handling all terrain types. L2 and L1 altimetry products are used, with state-of-the-art retracker algorithms in the methodology. The work presents a benchmark between teroVIR and current platforms in West Africa, Kazakhastan and the Arctic: teroVIR shows an unprecedented increase from 55% to 99% in spatial coverage.A large-scale validation of teroWAT results in an average of unbiased root mean square error ubRMSE of 0.638 m on average for 36 locations in West Africa. Traditional metrics (ubRMSE, median, absolute deviation, Pearson coefficient) disclose significantly better values for teroWAT when compared with existing platforms, of the order of 8 cm and 5% improved respectively in error and correlation. teroWAT shows unprecedented excellent results in the Arctic, using a L1 products based algorithm instead of L2 one, reducing the error of almost 4 m on average. To further compare teroWAT with existing methods, a new scoring option, teroSCO, is presented, measuring the quality of the validation of time series transversally and objectively across different strategies. Finally, teroVIR and teroWAT are implemented as platform-agnostic modules and used by flood forecasting and river discharge methods as relevant examples. A review of various applications for miscellaneous end-users is given, tackling the educational challenge raised by the community.

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Niger discharge from radar altimetry: bridging gaps between gauge and altimetry time series

Cited by 10 publications

References 49 publications

Water Resources in Africa under Global Change: Monitoring Surface Waters from Space

Water Resources in Africa under Global Change: Monitoring Surface Waters from Space

Multi-variate infilling of missing daily discharge data on the Niger basin

Challenges and Evolution of Water Level Monitoring towards a Comprehensive, World-Scale Coverage with Remote Sensing

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