Hydraulic or Hydropower

Aquifer characterization is indispensable for active development and management of ground and surface water resources. The important characteristic of groundwater rectification is the capability to determine accurate estimation of aquifer hydraulic characteristics. It is important to deliver a common intelligences for exchange of ideas. Yet, groundwater potential study and aquifer characterization is rarely conducted in Lower Gidabo catchment. Topographically, the catchment is undulated ranging from 1170 m of low flat lands near Lake Abaya to 3200 m AMSL. In this study, groundwater prospective of the catchment was assessed in terms of aquifer characteristics with hydraulic conductivity, transmissivity and storativity. The study targeted to contribute detailed aspect of aquifer hydraulic properties and hydrogeological features in the catchment. Arc GIS 9.3 and Aquifer test programs were used for the study. Hydraulic conductivity of the aquifer ranges from 3.5*10-4 to 2.91*10-3 m/day. Likewise, the transmissivity and storativity are ranged from 1*10-3 to 1.05*10-1 m 2 /min and 8.29*10-5 to 4.11*10-3 respectively. The major aquifer units of the area are weathered and fractured basalts. These types of aquifer formation are recognized to be good groundwater formations. As per the result perceived, hydraulic properties and lithological formation of an aquifer are variable throughout the catchment.

Transboundary river basins are under increasing pressure due to population growth, agricultural and industrial developments, and climate change, as well as river pollution. Water scarcity is on the increase due to the increasing gap between water demands and supply. This will result in more tensions, disputes, conflicts, and deadlocks in negotiations over water distribution, length of time it takes to fill the eservoir, and allocation. Ethiopia is building the Grand Ethiopian Renaissance Dam (GERD) on the Blue Nile River with a hydropower capacity of 6,000 MW. The total estimated cost of the project is US$ 4.8 Billion and will be the largest dam in Africa, which is much larger than the Aswan Dam in Egypt. Regional controversies have risen over the construction of the dam between Ethiopia and the downstream countries (Sudan and Egypt). The Blue Nile River is a source of around 85% of the Nile River water. Egypt claims that GERD will reduce flow of water in the Nile River between 11 and 19 billion m3(BCM) which will affect 2 million people and will also interrupt electricity supplies 25 to 40%. The real scale of the environmental impacts of GERD, under construction upstream of the Nile River, together with the rising sea levels, due to climate change, leading to saltwater intrusion downstream, are still not clear. But for Ethiopians GERD is empowering development and contribution to their future. With the Nile, no longer Egyptian birthright, and the Nile Delta gradually disappearing into the Mediterranean sea, millions of Egypt’s people will inevitably need to look elsewhere for a livable future. The crises, therefore, necessities the adaptation of a more effective institutional arrangement, such as through Rowland-Ostrom Framework, for common pool shared water resource management and cooperative approach to address and resolve present and future problems, including on other common transboundary resources (forest, oil/gas and minerals).The need for expanding traditional integrated water resources management to better include the cultural, social and political complexity of the GERD is the key factor to reconcile the contrasting concepts of “nationalism” and “regional hydro solidarity”. Connecting Nile and Congo water system, through diverting water by digging a 600-km canal together with pumping stations and other massive infrastructure to transport water from the Congo Basin to the Nile Basin has been suggested as an alternative way of ensuring Egypt’s water security. As part of mitigation measures, Egypt needs to invest in desalinization for fresh water, water-saving drip irrigation, and come up with an Aquifer Storage Recovery (ASR) scheme, artificial recharge and scheduled water extraction, to minimize the cumulative effect of the Grand Ethiopian Renaissance Dam and seawater intrusion downstream along the Mediterranean coast.

The tunnel spillway safely discharges the flood water from high rise dam. So, there is high chance of cavitation damages induced by high-speed flow due to high head and large discharge. Different types of aerators are generally introduced to protect the surface from cavitation. In this paper, the pressure distribution, water surface profile, velocity profile and aeration cavity length in free-flow tunnel of Jingping-1 hydropower projects were studied. Two type of aerators namely deflector with offset and only offset were used for the simulation study. The simulations were done by using the realizable k-ε model and volume of fluid method. The real tunnel spillway of Jingping-1 hydropower project contained the aerators by combining the deflector with offset. The results of numerical simulations were compared with experimental result which showed that the aerator with combination of deflector and offset was more reliable than aerator with aerator only offset. There was no chance of cavitation damages inside the spillway of aerator with deflector and offset as there was stable aeration cavity without backwater. There is more chance of cavitation in high velocity and high pressure head in free-flow tunnel spillway. Artificial aerators are generally introduced to reduce cavitation which is very cost-effective and easy measures. Different researches have been done in the study of aeration phenomenon. Chanson [1] explained that when large amount of air is introduced in aeration zone along with air water interfaces of jet and strong, de-aeration occurs at the impact of bottom near nappe impact. Pfisher [2] conducted a hydraulic model test with typical chute aerators with various approach flow features including pre-aeration. The study found that the stream-wise development and the bottom air concentration were affected by pre-aeration in the downstream of the aerators. Chanson [3] studied the performance of a spillway on steep spillway with high velocities. He found that if there were not enough surface aeration or if the tolerance of surfaces finish required to avoid cavitation s were too severe (v>30 m/s), aerators should be introduced at the floor or sometimes on side wall of spillway. Ramón [4] described the most important aspect of the effect that flow aeration has in combating the damages caused by cavitation as well as the natural entry of the air into the water flow and placing of the artificial aeration devices on spillway when natural aeration is insufficient. Chanson [5] established the formula for the calculation of bottom and side cavity length in sudden enlargement and vertical drop aerator. Both experimental and simulation methods were used to study the aeration in the spillways. Shuai li et al [6] studied the diffuse flow downstream of a radial sluice and full section aerator by combining a realizable k-ε turbulent model. Shuai li et al [7] studied the aeration from bottom as well as the side in connective tunnel with high head and large discharge by model test and numerical simulation and obtained the less back water effect in aeration cavity with increasing aeration length. In this paper, the combination of the realizable k-ε model and Volume of fluid (VOF) method was applied to simulate the characteristics of aerated flow of the free-flow tunnel in Jingpin-1 Hydropower Station.

Compound channels are hydraulic sections that consist of two parts including the main channel and the floodplain. The main channel conveys the usual runoffs and the basic discharge that often flows in the river. Predicting the flow characteristics in the prismatic compound channels includes the effect of the interaction between a fast flow in the main channel and a slower one in the floodplains. This speed difference creates a shear layer at the interface between the main channel and the floodplain, which results in the exchange of the size of the movement between the main channel and the floodplains. The result is a reduction in the flow-conveyance capacity of the main channel and its increase in the floodplains, which should be considered in flow modeling. On the other hand, Flow3D software is a great software for Computational Fluid Dynamics that is used to solve complex geometry problems. The main objective of this study is to evaluate the Flow3D model in numerical simulation of behavior of hydraulic flow characteristics such as velocity distribution, shear stress distribution and in prismatic compound channels. In this study, Volume of Fluid Method (VOF) was used to simulate water surface profiles and the dimensional Buckingham π theorem was used to extract parameters without effective dimension; besides, the model’s precision was tested by an experimental analysis in a rectangular flume. The results showed that the Flow3D numerical model has high accuracy in computing the flow passing the prismatic.