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1.
The eastern Ethiopian highland is endowed with large potential of water resources in terms of rainfall, groundwater and surface
water. Yet, due to overpumping of lake water and groundwater and environmental degradation, Lakes Haromaya and Adele have
completely dried up. The environmental degradation, due to deforestation and clearing of land for farming, has increased the
rate of siltation in the lakes that dramatically decreases the lakes’ volume and surface albedo, which increased the rate
of evaporation. The impact of these factors is aggravated due to decreasing net recharge to the lake and the alluvial aquifer.
Over the last 35 years, pumping of lake water for irrigation, mainly for subsistence farming, domestic and industrial use
shows an increasing trend. Hence, the available water for drinking and industrial purposes decreased drastically. In this
research, classical Penman aerodynamic combined energy budget, Penman nomogram methods, conventional soil moisture water balance
method and Penman–Monteith model were adopted to estimate free evaporation, actual and potential evapotranspirations. The
results indicate that evaporation is the dominant factor for the loss of water and water abstraction is 316% higher than the
effective precipitation, which is 110 mm/year. Therefore, overexploitation of the available resources has played an aggravating
role for the loss of the lakes in the area. The main cause for such resource depletion is the lack of integrated water resources
management strategies. The current water shortage in the area has mainly affected urban residents of Harar, Awoday and Alemaya
towns and the surrounding villages, which depend heavily on the two lakes. To alleviate the current crises interbasin water
transfer and rainwater harvesting would be possible alternatives besides ameliorating environmental situation of the basin. 相似文献
2.
Hydrochemical characterization of complex volcanic aquifers in a continental rifted zone: the Middle Awash basin, Ethiopia 总被引：2，自引：0，他引：2
Wakgari Furi Moumtaz Razack Tamiru Alemayehu Abiye Seifu Kebede Dagnachew Legesse 《Hydrogeology Journal》2012,20(2):385-400
The Middle Awash basin is an arid region in Ethiopia where surface waters are scarce and local communities are dependent on groundwater resources for water supply. The complex hydrogeological system of this basin has been conceptualized. Multivariate statistical analysis of hydrochemical variables and water isotopes were used to study the rock?Cwater interaction, geochemical reaction processes and the hydrological link between aquifers. Groundwaters from aquifers of the high-rainfall plateau bounding the rift are slightly mineralized, as well as depleted in ??18O and ??D, and contain 3H above 0.8?TU. This suggests a low degree of rock?Cwater interaction and that groundwater is under recharge from heavy rain that falls on surrounding highlands. On the other hand, groundwaters from aquifers of the rift floor are highly mineralized and show slight enrichment in ??18O and ??D with positive oxygen shift, but contain 3H below 0.8?TU. The positive oxygen shift in rift floor groundwaters may be caused by the isotopic exchange of oxygen between groundwater and aquifer materials during rock?Cwater interaction, whereas the low 3H content could be due to the decay of tritium along relatively long flow paths. The approach utilized in this study may be applicable to understanding hydrogeochemical processes in other complex volcanic terrains. 相似文献
3.
Geo-environmental assessment and geophysical investigations were carried out over the only functional municipal solid waste disposal site of the city of Addis Ababa, Ethiopia, known locally as Koshe. The accumulated wastes from Koshe have impact on the surrounding human and physical environment since the disposal site was not designed. The study deserves emphasis because the city of Addis Ababa currently obtains a considerable portion of its domestic water supply from a well field developed not much farther from and along a groundwater flow direction in relation to the waste disposal site. It was found out that the leachates from the site contain high concentration of biological oxygen demand, chemical oxygen demand, chloride and sulphate besides high concentration of cobalt, nickel and zinc in the surrounding soils. The geophysical results have mapped weak zones and near-vertical discontinuities that could potentially be conduits for the leachate from the wastes into the deep groundwater system. Further, a zone of potential leachate migration from the landfill was identified from the electrical models; the location of this zone is consistent with the predicted direction of groundwater flow across the site. The results further suggested that the open dump site tends to cause increasing amount of pollution on the surrounding soil, surface and ground waters. Furthermore, it was observed that the Koshe waste disposal site has grown beyond its capacity and the poor management of the open dump landfill has reduced the aesthetic value of the surrounding environments. The need to change/relocate the existing waste disposal site to a more suitable and technologically appropriate site is emphasized. 相似文献
4.
Groundwater has been the main source of water supply for large cities and towns over the last few decades in the upper Blue
Nile River Basin, Ethiopia. However, provision is often unsuccessful because of poor well productivity, difficult drilling
conditions, poor well positioning, or sometimes due to poor water quality. The growing pressure of urban population and industrial
development is focusing unprecedented attention on the groundwater potential of the basin. The purpose of this work is to
spatially characterize the groundwater potential of the upper Blue Nile River Basin with respect to variable recharge and
geodiversity. The study shows that from the annual recharge obtained using the base flow separation method, the renewable
groundwater potential in the basin was estimated to be in the range of 1.2 and 2 billion m3/year. The aquifers in the area are divided into three categories: low to moderate productivity (≈3.5 l/s) which includes
crystalline basement rocks, acidic lava flows and domes, and very fine alluvial sediments; moderate to high productivity (≈5.5 l/s)
that includes Mesozoic sedimentary rocks (sandstone, limestone, gypsum, dolomite); and high to very high productivity (≈20 l/s)
which includes basic lava flows of the Trap series, Quaternary lava flows and alluvial sediments. 相似文献
5.
Metal contamination of the environment by placer and primary gold mining in the Adola region of southern Ethiopia 总被引：3，自引：0，他引：3
Primary and placer gold mining sites in southern Ethiopia were studied to see the contribution of mining to the accumulation of metals in different environmental media. Sediment, water and plant samples were analyzed for Al, Mn, Fe, As, Ni, Cr, Cu, Co, Pb, W, Sb, Mo, Zn and V. Water parameters (pH, Eh, TDS, anions and cations) were also measured. The sediment analyses results show that the most abundant metals are Ni (average 224.7 mg/kg), Cr (199 mg/kg), Cu (174.2 mg/kg), V (167.3 mg/kg), Zn (105.5 mg/kg), Pb (61.5 mg/kg) and As (59.7 mg/kg) in the primary gold mining sites while the placer sites show high concentration of V (average 301.2 mg/kg), Cr (260.4 mg/kg), Zn (179 mg/kg), Ni (113.4 mg/kg), Cu (46.7 mg/kg), As (32.2 mg/kg) and Co (31 mg/kg). The metals Cu, Ni, W, Cr, As and Pb in primary and Sb, W, Cr, Ni, Zn, As and Mo in placer gold mining sites have geoaccumulation indexes (I
geo) from one to four indicating considerable accumulation of these metals. Waters from both primary and placer mining sites are near neutral to alkaline. Arsenic (average 92.8 μg/l), Ni (276.6 μg/l), Pb (18.7 μg/l), Sb (10.7 μg/l), Mn (1 mg/l), Fe (8.3 mg/l) and Al (23.8 mg/l) exceeded the guideline value for drinking water. Plants show high concentration of Cr (average 174.5 mg/kg), Ni (163.5 mg/kg), Zn (96 mg/kg) and W (48 mg/kg). Zinc, W, Mo, Ni and Cr show the maximum biological absorption coefficient (BAC) ranging 0.4–1.7, 0.1–104.6, 1.1–2.6, 0.2–1.6 and 0.2–3.6, respectively, and the results suggest bioaccumulation of these elements in plants. The minerals especially sulfides in the ore aggregate are the ultimate source of the metals. The release of the metals into the environmental media is facilitated (in addition to normal geologic processes) by human activities related to gold mining. 相似文献
6.
The Vaal River Basin is an economically significant area situated in the interior of South Africa (SA), where mining, industrial, domestic and agricultural activities are very intense. The purpose of the study was to assess the influence of geology and anthropogenic activities on groundwater chemistry, and identify the predominant hydrochemical processes in the basin. Data from seventy groundwater sites were retrieved from the national database, and attention was paid to fifteen water quality parameters. Groundwater samples were clustered into seven hydrochemically distinct groups using Hierarchical Cluster Analysis (HCA), and three samples treated independently. A Piper plot revealed two major water types, Ca–Mg–HCO3 and Ca–Mg–SO4-Cl, which were linked to dissolution of the underlying geology and mine pollution. The Ca?+?Mg vs HCO3?+?SO4 plot indicated that reverse ion exchange is an active process than cation exchange in the area. Principal component analysis (PCA) was used to identify the main natural and anthropogenic processes causing variation in groundwater chemistry. Four principal components were extracted using PCA that explains 82% of the total variance in the chemical parameters. The PCA results can be categorized by four components: (1) evaporites and silicates weathering enrichment of Na, K, Cl, SO4 and F, and anthropogenic Cl; (2) dissolution of dolomite, limestone and gypsum; (3) agricultural fertilizers (4) wastewater treatment. This study reveals that both natural and anthropogenic activities are the cause of groundwater variation in the basin. 相似文献
7.
An integrated survey program involving geological, hydrogeological and geophysical techniques has been employed to characterize the aquifer geometry, recharge and circulation dynamics of thermal springs within a shallow aquifer system in Ethiopia. The selected springs for the case study are Sodere and Gergedi, which are situated within the tectonically active Main Ethiopian Rift (MER). Geologically, the studied springs are located on Plio-Quaternary volcanic rocks. The geophysical results indicate the presence of subsurface weak zones represented by extensional tectonics and weathering zones which are responsible for thermal water circulation and facilitate recharge from the adjacent surface-water bodies. The structures inferred by the resistivity survey, both sounding and electrical tomography, present contrasts in rock resistivity response. The anomalous zones in the magnetic data are in good agreement with the zones that are revealed by geological mapping and surface manifestation of the thermal water discharge zones. The shallow aquifer of the central MER is under the influence of thermal water, which increases the groundwater temperature and mineral content. 相似文献
8.
Alemseged Tamiru Haile Tom RientjesAmbro Gieske Victor JettenMekonnen Gebremichael 《Advances in water resources》2011,34(1):26-37
Motivated by the need for rainfall prediction models in data scarce areas, we adapted a simple storage based cloud model to use routinely available thermal infrared (TIR) data. The data is obtained from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) of the Meteosat Second Generation (MSG-2) satellite. Model inputs are TIR cloud top temperatures at 15-min intervals and observations of pressure, temperature, and dew point temperatures from ground-based stations at 30-min intervals. The sensitivity of the parsimonious cloud model to its parameters is evaluated by a regional sensitivity analysis (RSA) which suggests that model performance is sensitive to few parameters. The model was calibrated and tested for four convective events that were observed during the wet season in the source basin of the Upper Blue Nile River. The difference between the simulated and the observed depth of the selected rain events varies between 0.2 and 1.8 mm with a root mean square error of smaller than 0.5 mm for each event. It is shown that the updraft velocity characteristic can provide relevant information for rainfall forecasting. The simulation results suggest the effectiveness of the model approach as evaluated by selected performance measures. The various characteristics of the rainfall events as simulated generally match to observed counter parts when ground-based and remote sensing observations are combined. 相似文献
9.
Groundwater is the major source of water and a critical resource for socioeconomic development in semi-arid environments like the Johannesburg area. Environmental isotopes are employed in this study to characterise groundwater recharge and flow mechanisms in the bedrock aquifers of Johannesburg, which is known for polluted surface water. With the exception of boreholes near the Hartbeespoort Dam, groundwater in the study area was derived from meteoric water that has undergone some degree of evaporation before recharge, possibly via diffuse mechanisms. Boreholes that tap groundwater from the Transvaal Supergroup Formation show depletion in δ18O and δ2H values. This is attributed to diffuse recharge through weathering fractures at high elevation that are undergoing deep circulation or recharge from depleted rainfall from the high-latitude moisture sources. The influence of focused recharge from the Hartbeespoort Dam was observed in the boreholes north of the dam, possibly as a result of the north–south trending fault lines and the north-dipping fractures in the bedding planes of quartzites. This is also supported by a reservoir water budget method which indicated a mean annual net flux of 2,084,131 m3 from Hartbeespoort Dam recharging groundwater per annum. Using tritium in the dam and boreholes located at 750 m and 5400 m downstream, average groundwater flow velocity was estimated as 202 m/year. An open system was observed in shale, andesite and granitic-gneiss aquifers indicating soil CO2 as a dominant source of carbon (δ13C) in groundwater. A closed system was also observed in dolomitic aquifers indicating carbonate dissolution as the predominant source of carbon. 相似文献
10.
Alemseged Tamiru Haile Ashenafi Lekasa Akawka Beza Berhanu Tom Rientjes 《水文科学杂志》2017,62(13):2139-2149
Climatic and hydrological changes will likely be intensified in the Upper Blue Nile (UBN) basin by the effects of global warming. The extent of such effects for representative concentration pathways (RCP) climate scenarios is unknown. We evaluated projected changes in rainfall and evapotranspiration and related impacts on water availability in the UBN under the RCP4.5 scenario. We used dynamically downscaled outputs from six global circulation models (GCMs) with unprecedented spatial resolution for the UBN. Systematic errors of these outputs were corrected and followed by runoff modelling by the HBV (Hydrologiska ByrånsVattenbalansavdelning) model, which was successfully validated for 17 catchments. Results show that the UBN annual rainfall amount will change by ?2.8 to 2.7% with a likely increase in annual potential evapotranspiration (in 2041–2070) for the RCP4.5 scenario. These changes are season dependent and will result in a likely decline in streamflow and an increase in soil moisture deficit in the basin. 相似文献