Browsing by Author "Solomon, Kassa"

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    Ground Water- Surface Water Interaction and Impact Assessment, In the Case 0f Western Ziway-Meki River Catchment
    (Addis Ababa University, 2021-07) Solomon, Kassa; Asie, Kemal (PhD)
    As the combined pumping rate of the water supply and irrigation of the towns and rural areas ,were the cause of the depletion of groundwater resources in the groundwater basin and the drying up of stream water. The goal of this research was to enhance the current understanding of the interaction of surface water-ground water and impact assessment using a numerical model. Initially, to measure the natural recharge of the aquifer and to model streamflow, the surface water hydrology of the sub basin was researched using the HEC-HMS (SMA)model. The ground flow mechanism was analyzed by using 3D numerical groundwater flow model (Processing Modflow Pro (Version 5.3.0.1)). The required model inputs were obtained from the results of field observation, secondary data and previous work carried out in the area. As calibration parameters, horizontal hydraulic conductivity from 0.1 m/day to 15 m/day and ground water recharge 64.6 mm/year, which constitute the main groundwater model parameters, were considered. The HEC-HMS(SMA) model was used to measure the recharge rate for the sub-basin in order to achieve a recharge. Model calibration was subsequently carried out using the process of trial-and-error calibration using groundwater contours formed from heads collected at 56 observation points. Therefore, the average RMSE for simulated hydraulic heads was approximately 20.65m. The calibrated model is used to assess the groundwater-surface water interactions, and groundwater system activity under various potential use scenarios. Simulated water levels in the model were more sensitive to decreases in recharge values and sensitive to decreases in hydraulic conductivity values. However, relative to recharge and hydraulic conductivity, the model is not as sensitive to decreases or increases in pumpage. According to the simulation, groundwater flows from the western escarpment to the east eventually join Lake Ziway. Lakes and rivers are significant sources of aquifer recharge. Increased pumping rate results substantial regional groundwater level decline, which leads to the drying of springs and shallow hand dug wells, according to simulations conducted under various potential future use scenarios. Finally, the model's water budget results showed that groundwater recharge comprised 81.48%, through river leakage 3.28 % and constant head was 15.24% of the total water input for the entire study region. Because of this, it can be noted that the surface water impacts to the water budget of the sub-basin.
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    Review on Price Adjustment Valuation Practices in Ethiopian Federal Road Construction Projects
    (Addis Ababa University, 2017-11) Solomon, Kassa; Solomon, Serste (PhD)
    In developing countries with deficit in infrastructure facilities, like Ethiopia, the role of road network expansion programs are fundamental. In line with this logic, Ethiopia is engaging in a number of road construction projects under regional and federal level by implementing consecutive Road Sector Development Programs (RSDP). Nevertheless, due to the fact that most road construction projects take over a year for completion on one hand and the cost of materials, equipment and labor often increase on the other; projects face an increase in contract price which leads to major problems in administration of the contract and completing the project within allocated budget. In contracts, the risk and uncertainty caused by fluctuations in cost of construction materials, labors and equipments, have been managed by providing price adjustment provisions usually by using a formula method. However, the implementation of these provisions encores different challenges regarding to determination of permissible weightings and coefficients as well as getting the price indices/price which reflects the actual market conditions. Therefore this research aims to explore and analyze the current price adjustment valuation methods in Ethiopian federal road construction projects and evaluate their capability in depicting the reality on the ground. To achieve the research aim specific objectives are set and case study method is used as research instrument. Accordingly, probing questions and themes are prepared and meticulously analyzed against the international practices evolved from literature review. The research result shows that the price adjustment practices observed on all selected cases are different on the subject of the non-adjustable portion, permissible weighting ranges as well as the source of index and prices. Based on the analysis of the cases, the establishment of permissible weighting ranges and nonadjustable factors are found to be inconsistent from the logically acceptable international practices. Besides, the question of the reliability and reputability of price indices/prices is identified as point of controversy between contracting parties.