Bossey Bangou, 24th of July 10.10 am: the Sirba peak reaches a record height of 714 cm, 1533 m3/s.
The Red Alert threshold is set at 709 cm, and the hydrometer is placed just above this threshold. In the last days, it tirelessly measured the height of the river level, allowing to give alerts for the villages downriver.
This hydrometer is the cornerstone of the Local Flood Early Warning System of Sirba, called SLAPIS (Système Locale d’Alerte Precoce Contre les Inondations de la Sirba). It was installed in 2018 by the ANADIA project, a collaboration between the Polytechnic of Turin, Istituto di Bioeconomia of Consiglio Nazionale Delle Ricerche (IBE-CNR) and the National Meteorological Directorate of Niger. The hydrometer measurements feed the hydraulic propagation models used by SLAPIS.
No meteorological/hydrological forecasting model could foresee this incredible flood wave that, since Sunday 19 July 2020, raised great concern among the authorities and populations, not only of Sirba but also in Niamey, the capital of Niger, a hundred kilometres downstream of the confluence between Sirba and the Niger River. This exceptional flow of Sirba raised the water level of the Niger river to such an extent that the first warning threshold for the city is expected to be exceeded this morning.
When the flood started, SLAPIS technicians and operators, even putting their safety at risk, have been continuously measured the levels of Sirba and sent updated observations to keep the population informed on the alerts and the evolving situation.
In all likelihood, the next hours will be highly convulsed, and we will know then if the flood peak will pass or if the rains, expected in the next 72h will bring a further rise of the water level in Bossey Bangou. In the latter case, the SLAPIS hydrometer will have to be dismantled and protected. The observer can continue to send the measurements manually up to a level of 800cm, but if it exceeds the 800cm threshold there will be only the lifejacket.