Mid-Century Climate Change Impacts on Ouémé River Discharge at Bonou Outlet (Benin)

Abstract

This work focuses on impacts of climate change on Ouémé River discharge at Bonou outlet based on four global climate models (GCM) over Ouémé catchment from 1971 to 2050. Empirical quantile mapping method is used for bias correction of GCM. Furthermore, twenty-five rain gauges were selected among which are three synoptic stations. The semi-distributed model HEC-HMS (Hydrologic Modeling System from Hydrologic Engineering Center) is used to simulate runoff. As results, HEC-HMS showed ability to simulate runoff while taking into account land use and cover change. In fact, Kling–Gupta Efficiency (KGE) coefficient was 0.94 and 0.91 respectively in calibration and validation. Moreover, Ouémé River discharge is projected to decrease about 6.58 m3/s under Representative Concentration Pathways (RCP 4.5) while an insignificant increasing trend is found under RCP 8.5. Therefore, water resource management infrastructure, especially dam construction, has to be developed for water shortage prevention. In addition, it is essential to account for uncertainties when designing such sensitive infrastructure for flood management.

Terrestrial or oceanic forcing? Water level variations in coastal lagoons constrained by river inflow and ocean tides

“…This reconstructed time series shows that over the study period, the maximum river discharge was of Q riv 1100 m 3 /s in November 2019. Such high values of river flux have been obtained from models of the Ouémé watershed (Lawin et al, 2019). Unsurprisingly, there is a strong annual variability and much more water has been drained into the lagoon in the wet season of 2019 than in 2018.…”

“…Although the net river flow considerably varies from the dry to the wet season, an exact quantification remains uncertain as rivers are not regularly gauged. Previous studies report river flow variations from a few tens of m 3 /s in the dry season to 1000 m 3 /s in the wet season (Chaigneau et al, 2022;Le Barbé et al, 1993;Djihouessi and Aina, 2018;Lawin et al, 2019). This strong seasonal variation of freshwater inflow results in a complete seasonal reversal of the salinity and ecosystem of the lagoon (Lalèyè et al, 2003;Okpeitcha et al, 2022) and can lead to major floodings.…”

From seasonal flood pulse to seiche: Multi-frequency water-level fluctuations in a large shallow tropical lagoon (Nokoué Lagoon, Benin)

“…This latter region is characterized by a single rainy season, with maximum precipitation between July and October (Biao, 2017;Ahokpossi, 2018;Lawin et al, 2019, Colleuil, 1987. The maximum discharge into the lagoon between September and November is unknown (rivers ungauged in the coastal region) and varies, depending on authors, from ~400 m 3 s -1 (Le Barbé et al, 1993;Djihouessi and Aina, 2018) to more than 1000 m 3 s -1 (Lawin et al, 2019). This river discharge produces a complete desalinization of the Nokoué Lagoon and a strong increase of its volume (Texier et al, 1980;Colleuil, 1987;Djihouessi and Aina, 2018).…”

Seasonal and interannual variability of salinity in a large West-African lagoon (Nokoué Lagoon, Benin)

“…During the short rainy season of South Benin, which coincides with the rainy season in North Benin, the Ouémé and Sô rivers are in flood and discharge a large amount of fresh water into Nokoué lagoon (Gadel and Texier, 1986;Djihouessi and Aina, 2018). The maximum discharge into the lagoon between September and November is badly known (rivers not regularly gauged in the coastal region), but some studies reported maximum river fluxes varying, depending on authors, from ~400 m 3 s -1 (Le Barbé et al, 1993;Djihouessi and Aina, 2018) to more than 1000 m 3 s -1 (Lawin et al, 2019). The mean water level in the lagoon, which is of ~1.3 m in dry season (Figure 1c), increases by up to ~90 cm during river floods to reach an average value of ~2.20 m (Chaigneau et al, 2021).…”