Search Results (3)

In Cameroon, the environmental profile is increasingly marked by anarchic urbanisation, which is strongly illustrated by the discharge of waste into the aquatic environment, leading to pollution. Indeed, the tributaries of the Mfoundi and Mefou river basins have nowadays become dumping grounds and receptacles for all kinds of waste, leading to the degradation of water quality and a reduction in biodiversity. This study aims to evaluate the effect of anthropogenic pressure on the biodiversity of benthic macroinvertebrates in three rivers of the Mfoundi basin (Ebogo, Abiergue, and Ako’o). For this purpose, some physicochemical parameters were measured according to standard methods, and benthic macroinvertebrates were collected according to the multihabitat approach. To this end, the physicochemical analyses revealed that the waters of these different streams are slightly basic and poorly oxygenated, with a saturation rate of 9.725 ± 11.74% and significant organic pollution. Biologically, a total of 5793 benthic macroinvertebrates divided into three phyla, eight orders, and more than thirty families were collected, with a population dominated by the order of insects and a low level of diversity dominated by pollutant organisms such as the Chironomidae, Lumbriculidae, and Physidae, which are saprobionts and saprophilous organisms. A redundancy analysis indicated that the main groups of benthic macroinvertebrates obtained were related to the gradients of the physicochemical parameters measured. The Shannon–Weaver diversity and Piélou equitability indexes showed the low diversity of the organisms within the different courses and their low equipartition, mainly due to the saprobiont and saprophilous groups that dominate the population. The exogenous inputs due to the increase in the population of the city of Yaoundé, which dumps its waste into the waterways, have major repercussions on the quality of the water and the population that abounds in this environment, particularly the benthic macroinvertebrates, which are an important link in the monitoring of water quality. Full article

Land surface temperature (LST) estimation at the river sub-basin level is crucial for developing land use planning at the basin scale and beyond. The main goal of this study was to analyze LST variations in response to land use mode (LUM) changes in the Mefou River sub-basin (Southern Cameroon) using geospatial techniques. To achieve this goal, we used Landsat 7 Enhanced Thematic Mapper Plus (2000 and 2010) and Landsat 8 Operational Land Imager (OLI)/Thermal Infrared Sensor (TIRS) data for 2020. We also used air surface temperature data from the Climatic Research Unit (CRU) to validate the LST. Our results reveal that between 2000 and 2020, the Mefou watershed recorded significant changes in LUMs, which were mainly manifested by an increase in impervious areas (IAs) (buildings and roads (+10%); bare soils and farmlands (+204.9%)) and forest reduction (−31.2). This decrease in the forest was also reflected by a reduction in NDVI values, the maximum of which went from 0.47 in 2000 to 0.39 in 2020. Contrary to the forest area and the NDVI values, the LSTs of the investigated basin increased over the period studied. There is a strong negative correlation between LST and NDVI. In general, high LSTs correspond to low NDVI values. For the years 2000, 2010 and 2020, the links between these two variables are materialized by respective correlation coefficients of −0.66, −0.74 and −0.85. This study could contribute to understanding the impact of LUM changes on the local climate, and could further provide assistance to policymakers in regard to land use planning and climate change mitigation strategies. Full article

Climate change, variability and anthropogenic forcings such as land use change are the main forcings of river discharge variability. However, an understanding of their simultaneous impacts on river discharge remains limited in some parts of the world. To shed light on this issue, the objective of this article is to investigate the effects of rainfall variability and land use change on river discharge in the Nyong basin (at Olama and Mbalmayo gauging stations) and some of its sub-basins (So’o and Mefou) over the long period 1950–2018. To achieve this goal, hydro-meteorological data of the Nyong basin and sub-basins were analyzed using the Pettitt test. Likewise, land use changes in the basin and sub-basins were also analyzed using supervised classifications of Landsat satellite images of the basins at different periods (1973, 2000 and 2018). On the annual scale, rainfall has decreased statistically over the studied basins. In the large basins (Olama and Mbalmayo), this decrease in rainfall is synchronous with that of discharges, while it is concomitant with an increase in the Mefou (small basin). After the ruptures within time series identified in the annual modules, the extreme discharges (maximum and minimum) decreased in Olama; in Mbalmayo, the maximum discharges remained stable while the minimum discharges decreased. On the other hand, the maximum and minimum discharges have significantly increased in the Mefou. The stability of maximum discharges at Mbalmayo and the increase in extremes on the Mefou in a context where the precipitation that generates the discharge has decreased can be attributed to land use change. These changes are essentially marked by an increase in impervious areas and a reduction in forest cover. On the seasonal scale, the impact of precipitation in the dry season is visible on the flows of the rainy seasons that follow them on the large basins (Olama and Mbalmayo). Between the decades 1970–1990 and 2000–2010, there was respectively a significant increase, then a decrease in summer precipitation, which impacted the autumn discharges in the same direction. Conversely, between the same intervals, there was a significant decrease, then a slight increase in winter precipitation. The impact of winter precipitation on the spring discharge is more visible during the first period only (1970–1990). During the second period, winter precipitation seems to have more of an impact on the runoff for the same season. In the Mefou sub-basin, the precipitation plays an essentially amplifying role in the increase in discharge in the seasons during which they occur. Those having experienced an increase, or a maintenance of precipitation (summer and spring) recorded the most significant increases in discharges. These results could be useful for long-term planning on the demand and use of water, as well as flood management in the basins Full article