Effects of Hydroclimatic Variability on the Spatial Dynamics of Ponds (Simenti, Kountadala and Oudassi) of the Gambia River Basin in the Niokolo Koba National Park (Senegal)

Abstract

With climate change, West African watercourses have undergone profound changes with large runoff deficits, faster dryings and very severe low flows. These modifications have led to a sharp decrease in water resources and a drying up of some water bodies. This article evaluated the effects of hydroclimatic variability on the spatial dynamics of a few ponds (Simenti, Kountadala and Oudassi) in the Gambia Basin in the Niokolo Koba National Park, NKNP, (Senegal). Data from five sets of images are used for pond trend mapping (Landsat, Google Earth and Sentinel). The hydroclimatic data used in this study include precipitation, temperature, evaporation, and discharge data from the Gambia Basin subjected to trend (Mann-Kendall) and rupture (Pettitt) tests. The results show that the trend is positive and significant for temperatures and evaporation and negative and significant for precipitation at a 95% confidence level. The surface area of the ponds, from 40.3 ha in 1975, increased sharply to 79.3 ha in 1988, then rose slightly in 1999 with 80.2 ha and in 2010 with 83.4 ha before to shrink sharply from 67.8 ha in 2019 due to rainfall deficit and the expansion of aquatic vegetation. Recommendations were made on how to improve the problem. Faced with the scarcity and drying up of water in these ponds of Niokolo Koba Park, water transfer operations such as those noted with the Simenti pond to save animals, remain fundamental according to some conservatives. Contribution/Originality: This study contributes to the exist literature by evaluating the effects of hydroclimatic variability on the spatial dynamics of a few ponds (Simenti, Kountadala and Oudassi) in the Gambia Basin in the Niokolo Koba National Park, NKNP, (Senegal). 1. INTRODUCTION Lakes and ponds are major repositories of biodiversity and provide multiple ecosystem services (Politi et al., 2012). These are vital resources for aquatic wildlife and human needs. Any change in their environmental quality and water renewal rate has far-reaching ecological and societal consequences (Vincent, 2009). Lakes and ponds are widely recognized as key indicators of environmental change. They exhibit remarkable variability over time in their morphometric, physical, chemical and biological characteristics (Omondi et al., 2014). These variations are mainly driven by climate change and human activities in their watershed. Ponds are strongly influenced by regional and global climate change in the short and long term (Nzoiwu et al., 2017). Their water level varies according to the precipitation / evaporation ratio, the groundwater inflow, the water abstraction rate and other factors. Therefore,