Abstract
The study of water resources’ dynamics and vulnerability in Rusizi national Park aimed to achieve the following objectives: (1) to identify, characterize and map water bodies, (2) to analyze and explain their periodical evolutions and (3) to analyze the spatial transformation processes affecting them. It is a contribution to the knowledge of the Park’s water resources for the development of monitoring systems and the sustainability of their functions as strategic ecosystems. It is based on the diachronic analysis of land cover from multi-date Landsat images of years 1984, 1990 and 2011 (TM), 2000 (ETM+) and 2015 (OLI-TIRS), landscape ecology tools and socio-economic and climate data. Supervised classification of images allowed the identification of 9 to 10 land cover classes including water bodies, according to years. A total number of 17 water bodies were detected from 1984 to 2015. During this period, regularly detected and dried up water bodies represent 18.2% and 54.6% respectively. The rates of water bodies’ drying up were 69.2% in 2000 and 64.2% in 2015. Water bodies are experiencing a great deterioration in number, size and stability. The Park's water coverage has decreased from 3.56% in 1984 to 2.43% in 2015. This corresponds to a decline of 31.2%. The water bodies’ stability, which was 75.70% between 1984 and 1990, represents only 42.78% between 1984 and 2015. The stability of individual water bodies is decreasing as well while low spatial connectivities are being observed between some close water bodies. The spatial transformation processes carrying these dynamics are patch enlargement, patch creation, patch attrition and patch dissection, depending on the period. Global warming, rainfall variability and farming activities like land drainage and irrigation are the most important threats to water resources.