Modeling the Hydrological Dynamic of the Breeding Water Bodies in Barkedji’s Zone

Temporary water bodies’ dynamics play an important role in the epidemiological chain-borne diseases such as Rift Valley fever as they are the main breeding habitats for mosquitoes. During the rainy season, hundreds of these temporary water bodies appear and grow in the Ferlo region (Senegal). The purpose of this research is to generate historical and future time series water levels and areas at three temporary ponds located in the environment and health observatory of Barkedji. A simple lumped hydrological model was developed for that purpose. It describes each pond watershed as three interconnected reservoirs: canopy, surface storage and soil storage and uses a linear relation to describe infiltration, percolation and baseflow (out of the soil reservoir). Given the depth of the water table in the region, percolation out of the soil surface is considered lost. Evapotraspiration was calculated using the Penman equation and withdraws water from the canopy and surface water reservoirs. Excess runoff from the soil storage is turned into runoff using a triangular unit hydrograph. The calibration was done using two years of hydrological and climatic data collected during the 2011 and 2012 rainy seasons. The calibration was successful and water level in the two ponds was simulated with a Root Mean Square Error (RMSE) of 11.2 to 15 cm. Because of the short duration of the observation, no validation could be done. Given the excellent agreement of the simulated and observed water levels during the calibration phase, the modeling exercise was considered to be successful. The developed models were used to generate historical time series of pond areas and correlate these to mosquitoes’ infestation in the region. Future time series of pond areas were also generated using downscaled outputs of three regional climate models from the AMMA ENSEMBLES experiment. The generated pond levels and areas are being used to assess the evolution of the disease in the next 40 years.

Could ERA5 Deliver Better Climate Services Than ERA-Interim over the West African Sahel Region?

Our paper assessed the improvement performance of the reanalysis(ERA5)compared to ERAI(ERA-Interim)both from the ECMWF(European Center for Medium-Range Weather Forecast)in representing the WAM(West African Monsoon)dynamic.Our aim is to evaluate the reliability of ERA5 to deliver better climate services than ERAI in the West African Sahel region.Two complementary observational databases namely the CRU(Climate Research Unit)and the GPCC(Global Precipitation Climatology Center)data are used to evaluate precipitation and temperature representation by the two reanalysis.Otherwise,the representation of some major features of the WAM system,such as the SHL(Saharan Heat Low),the AEJ/TEJ(African and Tropical Easterly Jets)was assessed using the two reanalysis data.The obtained results show a better representation of the seasonal accumulated precipitation and average temperature by ERA5 compared to ERAI with higher spatial correlation and lower bias relative to the observations.Furthermore,ERAI appears to be rainier than ERA5 but ERA5 produces more heavy rainfall days.During the period of intense monsoon,the frequency of the SHL is higher for ERAI which would favor intensification of monsoon inflow and depth.The lower SHL frequency observed in the ERA5 could explain the observed weakening intensity of AEJ which is favorable for moist conditions over the Sahel.These findings confirm the progress made by ERA5 compared to ERAI in representing the WAM dynamic and demonstrate its reliability for delivering better climate services over the West African Sahel.