River flow prediction in data scarce regions: soil moisture integrated satellite rainfall products outperform rain gauge observations in West Africa

Abstract

Satellite precipitation products have been largely improved in the recent years particularly with the launch of the global precipitation measurement (GPM) core satellite. Moreover, the development of techniques for exploiting the information provided by satellite soil moisture to complement/enhance precipitation products have improved the accuracy of accumulated rainfall estimates over land. Such satellite enhanced precipitation products, available with a short latency (< 1 day), represent an important and new source of information for river flow prediction and water resources management, particularly in developing countries in which ground observations are scarcely available and the access to such data is not always ensured. In this study, three recently developed rainfall products obtained from the integration of GPM rainfall and satellite soil moisture products have been used; namely GPM+SM2RAIN, PRISM-SMOS, and PRISM-SMAP. The prediction of observed daily river discharge at 10 basins located in Europe (4), West Africa (3) and South Africa (3) is carried out. For comparison, we have also considered three rainfall products based on: (1) GPM only, i.e., the Early Run version of the Integrated Multi-Satellite Retrievals for GPM (GPM-ER), (2) rain gauges, i.e., the Global Precipitation Climatology Centre, and (3) the latest European Centre for Medium-Range Weather Forecasts reanalysis, ERA5. Three different conceptual and lumped rainfall-runoff models are employed to obtain robust and reliable results over the 3-year data period 2015–2017. Results indicate that, particularly over scarcely gauged areas (West Africa), the integrated products outperform both ground- and reanalysis-based rainfall estimates. For all basins, the GPM+SM2RAIN product is performing the best among the short latency products with mean Kling–Gupta Efficiency (KGE) equal to 0.87, and significantly better than GPM-ER (mean KGE = 0.77). The integrated products are found to reproduce particularly well the high flows. These results highlight the strong need to disseminate such integrated satellite rainfall products for hydrological (and agricultural) applications in poorly gauged areas such as Africa and South America.

Unpacking some of the linkages between uncertainties in observational data and the simulation of different hydrological processes using the Pitman model in the data scarce Zambezi River basin.

“…However, this was rather beyond the scope of this study and should probably be conducted in areas where more ground-truth data are available than in the large sub-basins of the Zambezi River basin. Further development of these earth observation data, however, could represent an important contribution to understanding processes in data scarce areas, as demonstrated recently for the correction of precipitation reanalyses data (Brocca et al 2019), or for the validation of river flow observation data (Brocca et al, 2020).…”

Unpacking some of the linkages between uncertainties in observational data and the simulation of different hydrological processes using the Pitman model in the data scarce Zambezi River basin

“…However, this was beyond the scope of this study and should be conducted in areas where more ground-truth data are available than in the large sub-basins of the Zambezi River basin. Further investigations of this nature could contribute to understanding processes in data scarce areas, as demonstrated recently for the correction of precipitation reanalyses data (Brocca et al, 2019), or for the validation of river flow observation data (Brocca et al, 2020).…”

Evaluation of satellite precipitation products for water allocation studies in the Sio-Malaba-Malakisi River Basin of East Africa

“…In ungauged basins, studies have shown that satellite rainfall products can be used as an alternative source of meteorological data important for river basin management studies (Blöschl et al 2013;Maggioni & Massari, 2018;Belete et al 2020;Brocca et al 2020). In limited gauged basins, other studies have noted the need to corroborate the existing measurements with products derived from satellite based measurements, considering their extensive and dependable global coverage (Sooroshian et al 2000;Jiang et al 2018;Lakew et al 2020).…”