Malacological and Parasitological Surveys on Ethiopian Rift Valley Lakes: Implications for Control and Elimination of Snail-Borne Diseases

Schistosomiasis is one of the snail-borne diseases responsible for the second-highest burden of diseases among neglected tropical diseases. The use of mass drug administration to the populations most at risk is a backbone of the strategy to prevent and control schistosomiasis transmission. However, it offers no protection against re-infection, and humans are often re-exposed when they return to water bodies where snails release cercariae. Surveys on cercarial infection in snails could provide better insights on human disease risk. Hence, in this study, we investigated cercarial infection in snails and also determined the epidemiology of Schistosoma mansoni among fishermen at Ethiopian Rift Valley lakes. Freshwater snails were collected from the shorelines of Ethiopian Rift Valley lakes for examination of cercarial infection during 2020. Environmental data on water quality variables and physical characteristics of snail habitats were collected. Stool samples were collected from fishermen and the Kato-Katz technique was applied for the quantification of Schistosoma mansoni eggs. A malacological survey indicated that six morphologically distinguishable types of cercariae were found in snails. Infected snails with cercaria were more likely present in habitats with high five-day biological oxygen demand and low dissolved oxygen. The overall prevalence of Schistosoma mansoni infection among the fishermen at Ethiopian Rift Valley lakes was found to be 21.5%. This indicates that fishermen at Ethiopian Rift Valley lakes are one of the groups of people harboring schistosome cercariae which are potentially responsible for the transmission of schistosomiasis to lakeshore communities who have contact with lake water. Therefore, complementary medical treatment, public health interventions, environmental management and snail reduction are needed to control the transmission of schistosomiasis.

Assessment of Rising Water Levels of Rift Valley Lakes in Kenya: The Role of Meteorological Factors

The impacts of increased water levels in Kenyan lakes are a major problem that is affecting communities and their livelihoods. Upsurge in water levels of the Rift Valley Lakes is one of the recent climate extremes witnessed over Eastern Africa where the rises appear to be consistent with the occurrence of enhanced seasonal rains between 2016 and 2020. Considering that many explanations have been provided as possible causes, there is still little empirical evidences. This study aimed at assessing the link between meteorological factors and the rises in lake levels in order to see if these can explain the causes. Further using surface observations potential to predict the water levels was examined. Datasets on rainfall, temperature and water levels from four Lakes in Kenya were used to establish the changes in these variables using statistical methods. Generalized Linear Models were used to predict the water levels in the study lakes. Results indicate that rainfall and temperature as well as other climate drivers has been changing over the last recent years with increased precipitation being consistent with the observed high stands in the Rift Valley lakes. Specifically, the results of the forecasted levels indicate substantial and slight increase for lake levels in Naivasha while the Lake Baringo levels are predicted to rise sharply within the study data periods.

Physicochemical Properties and Heavy Metal Concentration in Borehole Water of Boko Haram Affected Areas of Madagali and Michika, Adamawa State, Nigeria

The impacts of increased water levels in Kenyan lakes are a major problem that is affecting communities and their livelihoods. Upsurge in water levels of the Rift Valley Lakes is one of the recent climate extremes witnessed over Eastern Africa where the rises appear to be consistent with the occurrence of enhanced seasonal rains between 2016 and 2020. Considering that many explanations have been provided as possible causes, there is still little empirical evidences. This study aimed at assessing the link between meteorological factors and the rises in lake levels in order to see if these can explain the causes. Further using surface observations potential to predict the water levels was examined. Datasets on rainfall, temperature and water levels from four Lakes in Kenya were used to establish the changes in these variables using statistical methods. Generalized Linear Models were used to predict the water levels in the study lakes. Results indicate that rainfall and temperature as well as other climate drivers has been changing over the last recent years with increased precipitation being consistent with the observed high stands in the Rift Valley lakes. Specifically, the results of the forecasted levels indicate substantial and slight increase for lake levels in Naivasha while the Lake Baringo levels are predicted to rise sharply within the study data periods.

Morphometric Variations of Nile Tilapia (Oreochromis niloticus) (Linnaeus, 1758) (Perciformes, Cichlidae) Collected from Three Rift Valley Lakes in Ethiopia

The pattern of morphometric differentiation among three populations of Tilapia (Oreochromis niloticus) sited in Koka, Ziway, and Langano lakes in the Ethiopian rift valley was examined. Morphometric differentiation was examined, compared and quantified by the use of twelve different body measurements in 391 specimens to generate baseline information for conservation and product improvement plans. The result revealed that comparisons of mean values of morphometric measurements in the three studied tilapia populations statistically significant differences (P<0.05). The Fulton’s condition factor (K) of Oreochromi niloticus samples collected from Lakes Koka, Ziway, and Langano was 1.48, 1.2, and 0.66, respectively. The Discriminant Function Analysis performed on seven variables led to a correct classification in 90.5 % of cases. Differences observed between samples in this study indicated that there is important morphometric variation between the studied tilapia populations. Plotting the two significant canonical discriminant functions separated the Lake Langano population from the other two.

Analysing Trends and Spatio-Temporal Variability of Precipitation in the Main Central Rift Valley Lakes Basin, Ethiopia

This study aims to investigate trends and spatiotemporal variability of precipitation during the period of 1980-2015 in the Main Central Ethiopian Rift Valley Lakes Basin. Mann-Kendall (MK) and Sen’s Slope (SS) estimation were used to detect the trends and magnitudes respectively. The Inverse Distance Weighting method was employed for spatial interpolations. The results revealed that the rainfalls had experienced less concentrated and highly variable in the central rift floor. The trend analysis showed that out of 21 stations, 4 stations (Koshe, Bulbula, Kofole and Shashamane) in annual; six stations (Koshe, Bulbula, Tora, Wulberg, Wondogenet, and Shashamane) in spring; and only one station (Shashamane) in summer showed significantly decreasing trends with -4.5 to -15.59 mm/year range. All stations in spring rainfall revealed no positive trends. Conversely, in both annual and summer rainfall statistically significant increasing trends exhibited for Ejersalelle and Adamitulu with 6.4 to 7.94mm/year range. In monthly time scales, the significant decreasing and increasing trends were also investigated for a few stations. Increasing trends could lead to an increase in potential for water resources whereas variability and decreasing trends could boost over-exploitation of water resources. This study would be provided useful information for management of water resources in the study area.

Spatial and Temporal Variability in Suspended Sediment Yield for two tropical mountain catchments draining into the Southern Ethiopian Rift Valley.

&lt;p&gt;Complex terrain tropical mountainous catchments are typically characterized by intense rainfall events, flash floods and high erosion rates with large variability over short distances. Whilst these processes are known, little quantitative information on the spatiotemporal variability in suspended sediment yield (SY) of African tropical mountain environments is available. Here, we provide such data for two catchments in the Southern Ethiopian Rift Valley characterised by annual rainfall of 700 to 1000 mm concentrated in the rainy season from April to October. In total 6 gauging stations were installed along Elgo (298 km&amp;#178;) and Shafe (191 km&amp;#178;) rivers which have their headwaters in the Gamo Highlands (max. elevation 3500 m) and run into the rift valley lakes of Chamo (1107 m) and Abaya (1169 m), respectively. For each river, a gauging station was installed where they enter the lakes as well as at the apex of extensive alluvial fans that developed in the graben lowlands, enabling to quantify the buffering capacity of the fans. For Elgo, two extra stations in the highlands were installed to monitor downstream changes in SY. At all stations, discharge (Q) was measured at 10-min resolution using a pressure diver during in 2018-2019. Additionally, 1542 samples were taken to measure the suspended sediment concentration (SSC), and these were used to establish sediment rating curves in order to calculate total suspended SY from the continuous discharge records. Observed SSC varies between 0.04 and 111.48 g/l for discharges ranging between 0.005 and 227.20 m&amp;#179;/s, whereas annual SY varies between 1133 and 6373 t/km&amp;#178;/year. Both SSC and SY values are in line with those reported for other highland rivers in Ethiopia and in line with SY values for other tropical mountain catchments in the world. A strong temporal variability in SSC and SY is observed and can be explained mainly due to changes in hillslope sediment supply throughout the seasons. Peak sediment transport is mostly concentrated in the first two months (May to June) of the rainy seasons accounting for about 60% of the total SY of the season. At the start of the rainy season, topsoil is loose because of tillage operations that prepare the soil for cultivation. Furthermore, vegetation cover is at its lowest value. Throughout the rainy season, vegetation cover increases and hence soil erosion and sediment yield declines.&amp;#160; Comparing the SY of the various gauging stations shows that total sediment load increases in downstream direction, up to the apex of the alluvial fans. Whereas agricultural top soil erosion is most important in the upper parts of the landscape, gully erosion and river bank erosion also contribute much sediment in downstream direction. However, total suspended SY delivered to the lake-based gauging stations is 32 to 53% lower compared to the total suspended SY measured at the gauging station situated near the apex of the alluvial fans. This implies that a significant proportion of the sediment load is buffered by the fans and points to an important dis-connectivity between eroding mountains and rift valley lakes.&lt;/p&gt;