Diel vertical migration of zooplankton in a hypertrophic shallow temperate lake, Germany

Zooplankton as important links in the food web of aquatic ecosystems have been studied extensively. In current literature their diel vertical migration (DVM) is a highly discussed issue. In this investigation DVM by zooplankton is studied in a hypertrophic shallow lake in Germany. The objectives of the study were to see if DVM by zooplankton occurs in shallow lakes such as Lake Dagowsee, the possible overlap in DVM of Leptodora kindtii, an invertebrate predator, and zoopankton, and the effect of wind action on DVM. It was found out that DVM of zooplankton occurs in Lake Dagowsee despite the limited range of depth for migration, wind action can influence DVM and L. kindtii poses a complex situation in relation to DVM behaviour of zooplankton in Lake Dagowsee. Finally, further studies are suggested with regard to DVM variation between different species, size and hybrid groups of Daphnids, and identification of the light sensitive range that can cue DVM of zooplankton and L. kindtii in temperate and tropical waters. Key words/phrases: Daphnia spp., Diaphanosoma brachyurum, Eudiaptomus gracilis, Lake Dagowsee, zooplankton SINET: Ethiop. J. Sci. Vol.27(1) 2004: 33-4

Khat and alcohol use and risky sex behaviour among in-school and out-of-school youth in Ethiopia

BACKGROUND: Khat (an evergreen plant with amphetamine-like properties) and alcohol are widely consumed among the youth of Ethiopia. However, their relationship to risky sexual behaviour is not well described. This study was conducted to describe the magnitude of risky sexual behaviour (unprotected sex and early initiation of sexual activity) and its association with Khat and alcohol consumption in Ethiopian youths. METHODS: A probabilistic national sample of 20,434 in-school and out-of-school youths aged between 15 and 24 years of age was selected and interviewed regarding their sexual behavior and substance use. RESULTS: Over 20% of out-of-school youth had unprotected sex during the 12-month period prior to interview compared to 1.4% of in-school youth. Daily Khat intake was also associated with unprotected sex: adjusted OR (95% CI) = 2.26 (1.92, 2.67). There was a significant and linear association between alcohol intake and unprotected sex, with those using alcohol daily having a three fold increased odds compared to those not using it: adj. OR (95% CI) = 3.05 (2.38, 3.91). Use of substances other than Khat was not associated with unprotected sex, but was associated with initiation of sexual activity: adj. OR (95% CI) = 2.54 (1.84, 3.51). CONCLUSION: A substantial proportion of out-of-school youth engage in risky sex. The use of Khat and alcohol and other substances is significantly and independently associated with risky sexual behaviour among Ethiopian youths

Ecological changes in two Ethiopian lakes caused by contrasting human intervention

AbstractAlemaya and Hora-Kilole are small lakes found in central and southeastern parts of Ethiopia at similar altitudes. These lakes are exposed to contrasting human interventions. From Lake Alemaya water is withdrawn, while water is added to Lake Hora-Kilole because agricultural experts diverted flow from an adjacent river by constructing a weir. As a result, Lake Alemaya is continually shrinking due to uncontrolled water withdrawal for irrigation and municipal uses but Lake Hora-Kilole, now a reservoir, has increased in volume. Such uncontrolled contrasting anthropogenic intervention has caused ecological changes as observed from various limnological parameters. The problems of conserving these two tropical African lakes and the plankton contained in them are noted. Based on the present scenario, suggestions are forwarded as to what should be done with these lakes and similar situations elsewhere in the tropics

SWAT based hydrological assessment and characterization of Lake Ziway sub-watersheds, Ethiopia

Study region: Lake Ziway watershed, Ethiopia. Study focus: Lake Ziway and its watershed play a significant role in supporting the livelihoods of people in the region. However, the study region is currently under heavy human pressures mainly associated with the ever increasing of human population and the subsequent intensification of agricultural development activities. The present study therefore aims at quantifying and comparing water balance components, feeder rivers’ discharge and evapotranspiration (ET) in the study region using SWAT (Soil and Water Assessment Tool) model. Flow data from 1988 to 2000 and from 2001 to 2013 were used for model calibration and validation periods respectively. New hydrological insights for the region: Results show that infiltration, surface runoff, base flow and aquifer recharge were large in Katar sub-watershed while ET and lateral flow were large in Meki sub-watershed. However, surface and base flows showed decreasing trends in both sub-watersheds, yet Katar sub-watershed showed major contribution of water to Lake Ziway. The model estimated Lake Ziway and its watershed mean annual ETs as 1920 mm and 674 mm respectively, but plantation showed more ET than other land cover types in the watershed. If the current trends in irrigation development continue in the region, it is suspected that Katar and Meki Rivers are likely to cease to exist after seven decades, and so is then Lake Ziway to dry out

Diversity, distribution and abundance of fish species in Lake Langeno, Ethiopia

This study of diversity, distribution and abundance of fishes in Lake Langeno (also written as Langano in the literature), Ethiopia, was conducted from March 2014 through February 2016. The basis for this study was that fish species were subject to uncontrolled fishing over many years and existing data on diversity has become unreliable for management and sustainability of the sector. In order to examine the existing diversity, habitat preference and seasonal distribution, spatial and temporal data were collected from six different sampling sites by using various mesh-sizes of gillnets and long lines. Data were analyzed by Canonical Correspondence Analysis (CCA), SPSS software and also by various descriptive statistics. The results indicate that all the physico-chemical parameters did not show significant spatial, but high temporal variations. A total of seven fish species dominated by cyprinid family were identified (H′ = 1.264). Carassius carassius and Cyprinus carpio, which were not reported in previous studies, now comprise 0.64% and 6.99% of the total collected specimens, respectively. All the fish species were collected from all the sampling sites, except at the middle site where C. carassius and Garra dembecha were absent. IRI was essentially similar for all the sampling sites, but differed in the relative importance of each species with the high importance of Oreochromis niloticus. Principal component analysis (PCA) did not produce distinct habitat-associated species patterns across the sampling sites. However, temperature and depth seemed to be the key environmental factors determining fish community structure in the lake. The results showed that the composition of the fishes has undergone some changes from what was reported in the literature. Therefore, appropriate management action is required in order to sustain the resources for conservation and continued fishing practices.Keywords/phrases: Diversity, Ethiopia, Fish abundance, Fish distribution, Lake Langen

Evaluation of the physical, chemical, and biological characteristics of surface water in urban settings and its applicability to SDG 6: The case of Addis Ababa, Ethiopia

In this study, an analysis of physicochemical and microbiological water quality parameters was carried out to evaluate the water quality status of the city from the two major reservoirs that supply drinking water to the city. Unlike most studies which only report on the water quality from the source or final treated water, this study assessed the water quality from the raw water source, the treatment plant as well as the treated water from taps. The analysis was conducted in accordance with the American Public Health Association's recommended procedures. Silica varied between 8.85–15.1 mg/l for Legedadie reservoir which is less than the stipulated limit of 25 mg/l and 72.2 to 111.77 mg/L for Gefersa. With the exception of turbidity, total phosphorus and dissolved oxygen which recorded mean values of 252.4 NTU, 2.76 mg/l and 5.46 mg/l respectively, nitrate, nitrite, ammonia, total soluble solids, total alkalinity, pH, electrical conductivity and temperature were discovered to be within the WHO permitted range with mean values of 0.36 mg/l, 0.11 mg/l, 0.067 mg/l, 0.01 mg/l, 53.13 mg/l, 8.14 mg/l, 148.9 μS/cm and 18.57 °C respectively. Total coliforms were found in all waters samples whilst faecal coliforms and Escherichia coli were recorded in the range 20–3000 CFU/100 mL. Ammonia, turbidity, pH and electrical conductivity were found to significantly influence microbial densities in the drinking water. Filtered and treated water sample recorded a 0 CFU/100 mL for faecal coliforms value which indicates that the water is in conformity to water quality standards. However, total coliforms in the range of 3000 to 5000 CFU/100 mL were found in all water samples indicating contamination hence treatment is recommended before drinking it. In contemporary times of increased urbanization and water pollution, this research will assist in the effort to provide safe water and sanitation for all city residents

Implications of land use/land cover dynamics on urban water quality: Case of Addis Ababa city, Ethiopia

Water resources are often at the center of urban development but, as the city expands, the environmental pressure on its water resources increases. Therefore, in this study, we looked into how various land uses and changes in land cover affect the water quality in Addis Ababa, Ethiopia. Land use and land cover change maps were generated from 1991 to 2021 at intervals of five years. On the basis of the weighted arithmetic water quality index approach, the water quality for the same years was likewise divided into five classes. The relationship between land use/land cover dynamics and water quality was then evaluated using correlations, multiple linear regressions, and principal component analysis. According to the computed water quality index, the water quality decreased from 65.34 in 1991 to 246.76 in 2021. The built-up area showed an increase of over 338%, whereas the amount of water decreased by over 61%. While barren land exhibited a negative correlation with nitrates, ammonia loadings, total alkalinity, and total hardness of the water, agriculture and built-up areas positively correlated with water quality parameters such as nutrient loading, turbidity, total alkalinity, and total hardness. A principal component analysis revealed that built up areas and changes in vegetated areas have the biggest impact on water quality. These findings suggest that land use and land cover modifications are involved in the deterioration of water quality around the city. This study will offer information that might help reduce the dangers to aquatic life in urbanized environments

The Ripple Effect of Climate Change: Assessing the Impacts on Water Quality and Hydrology in Addis Ababa City (Akaki Catchment)

This research aimed to evaluate the effects of climate change on the hydrology and water quality in the Akaki catchment, which provides water to Addis Ababa, Ethiopia. This was performed using the soil and water assessment tool (SWAT) model and an ensemble of four global climate models under two Shared Socioeconomic Pathways (SSP) emission scenarios from Coupled Model Intercomparison Project Phase 6 (CMIP6). The climate data were downscaled and bias-corrected using the CMhyd tool and calibrated and validated using the SWAT-CUP software package. Change points and patterns in annual rainfall and temperature were determined using the homogeneity test and Mann–Kendell trend test. Water quality data were obtained from Addis Ababa Water and Sewerage Authority (AAWSA), and more samples were taken and analyzed in accordance with APHA recommended procedures. The SWAT model output was then used to assess the impacts of climate change on hydrological components and water quality. Rainfall increased by 19.39 mm/year under SSP2-4.5 and 12.8 mm/year under SSP8.5. Maximum temperature increased by 0.03°C/yr for SSP2-4.5 and 0.04°C/yr for SSP5-8.5. Minimum temperature increased by 0.03°C/yr under SSP2-4.5 and 0.07°C/yr under SSP5-8.5. This warming will augment the evapotranspiration rate which in turn will have a negative impact on the freshwater availability. Streamflow will increase by 5% under SSP2-4.5 and 9.49% under SSP5-85 which may increase sporadic flooding events. Climate change is expected to contribute to the deterioration of water quality shown by 61%, 36%, 79%, 115%, and 70% increased ammonia, chlorophyll-a, nitrite, nitrate, and phosphorus loadings, respectively, from 2022. The increase in temperature results in increases in nutrient loading and a decrease in dissolved oxygen. Overall, this research demonstrated the vulnerability of the catchment to climate change. The findings of this research can offer vital knowledge to policymakers on possible strategies for the sustainable management of water