Water Resources. Associate Prof. Ahmed Moustafa Moussa Lecture -1 Lecture 4

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1 Water Resources By Associate Prof. Ahmed Moustafa Moussa Lecture -1 Lecture 4

2 High Aswan Dam Project 1. Location The High Aswan Dam (HAD) location was determined to fit the topographical features of the chosen site. The channel dam was positioned in the narrowest part of the river between two short valleys (Khor Kundi and Shimet Gaddino) which descend towards the Nile from the east. The two side valleys were conveniently used as forebay and afterbay for the diversion works on the eastern bank (Kinawy and Shenouda, 1993) 2. Construction time The time for construction of HAD is divided into two phase the first phase from 1960 to May 1964 and the second phase from May 1964 to July Materials used in HAD construction Almost, all the materials used for the dam body were taken from borrow pits in the vicinity of the dam vicinity at a distance of not more than 10 km. Table (1) quantities of materials used for HAD construction. Material Volume in million m 3 Executed project Rock fill Dune sand Silt and clay Filters Coarse sand - Concrete and other materials Others Total

3 4. Project description The High Aswan Dam is a rockfill dam,constructed across the Nile at a distance of 7 km south of the city of Aswan. As shown in figure (1) the water is diverted into a diversion channel, at the middle of which there are six tunnels. The tunnel inlets are provided with steel gates to control the quantity of water passing through them. Each of the Tunnels bifurcates before its end, and each of the twelve branches delivers its water to a hydraulic generating unit of the power station. The diversion channel is situated on the eastern Nile bank. The spillway is located on the western side. The total length of the dam is 3600 m, of which 520- m is located between the two banks of the river, and the rest extend along both sides. The height of the dam is 111 m above the riverbed. Its width is 980 m at the bottom and l0 m at the top. The body of the dam consists of granite and sand, in the middle there is a core of Aswan puddle clay which focus the dam core to minimize water seepage. At the front. It is connected with a horizontal impervious Curtain. Since the dam bed consists of alluvial materials, it has a vertical Cut-off curtain extending below the core. With the same depth as the sedimentary layer. On the downstream side. There are two rows of vertical relief wells have been provided to drain any water leakage. The reservoir storage Capacity is 162 Bilion Cubic Meter distributed as follows: 90 BCM : lives storage capacity between level 147 m and 175 m. 31 BCM: dead storage for sediment deposition. 41 BCM: storage available for high flood waters between levels of 175 m and 182 m. The hydroelectric power station is situated at the outlets of the tunnels and consists of 12 units with a capacity of 175,000 kw each, i.e. with a total capacity of 2.1 million kw, producing 10x 10 9 kwh of power annually. Each generating unit consists of a Francis-type hydraulic turbine. Work was started on the first stage of the project in 1960 and ended in May This stage included the excavation of the diversion channel, the construction of the main tunnels, and the construction of the body of the dam up to the level of m (17.5-m above riverbed). The diversion of the Nile's course to enable the completion of the damand the power plant took place in May 1964; and the construction was completed in July 1970 (Abu Zaid, 1986). 5. HAD profile Figure (2) shows the cross section of HAD. In the channel part the lower portion of the dam differs greatly from the upper part. The lower part, 48 m. high at the upstream side and 25m. In the downstream side is composed of sandfill

4 in the central zone, fills of screened stone sluiced with sand and banquettes filled with rock muck. Sand fills in the central part and alluvial deposits in the bed under the core were consolidated by grouting. sand prisms in both sides of the central prism is compacted by vibro-flotation. These fills except the grouting represent the first stage of construction (Kinawy and Shenouda, 1993). The upper portion of the dam is located above level 114m. Houses the impervious clay core. Inside the core, three inspection galleries of Figure (2) Cross Section at High Aswan Dam reinforced concrete were constructed with portal being located on both banks. From these galleries, bore holes were drilled and grouts injected into the alluvial forming the grout curtain under the core. The galleries are both for inspection monitoring of dam behavior by control devices and can be used for regrouting the foundation if needed. On both sides of the core up to level 153m. sand prisms are located and filled hydraulically and compacted with vibro-rollers are located. Above level 153 the side surface of the core are covered from the upstream side by a layer of stone chips and a layer of sand and from the downstream side by a sand layer followed by a three layer filter. Then follows a transitional layer of rock and final side prisms of rock muck. The clay blanket adjoins the core from the upstream side. The blanket is of a complicated configuration to ensure the stability of the upstream wedge of the dam. In the downstream wedge a longitudinal drain was provided. In front of the downstream banquette a sand prism designed for the interception of the filtration from under the dam was constructed. To lower the gradient of the seeping flow, deep drainage wells were provided at

5 the outlet of the flow in the downstream. The upstream slope was protected against waves with large rock blocks of size over 5.0 m. A convential profile of the rock-fill dam with an impermeable core and a grout curtain was designed. At the foot of the downstream slope of the core a protective sand prism covered by a filter was widened at its bottom part. Similar to the channel part, the outer prusms were made of rock muck. Large volumes of rocks were excavated to clean the rock foundation for the core. Excavators removed a layer of weathered rocks and then the surface was cleaned down to sound rock. Where the surface of rock was fissured it was gunite and then grouted. A comparison between the HAD and some other dams allover the world can be reported as shown in table (2) this comparison show that HAD is the six height dam, is the bigest capacity, is the second power generation. Table (2) A comparison between HAD and some other dams Name of Country Type Height (m) Volume Capacity Power the dam MCM BCM MKW Noreek Russia Rock fill HAD Egypt Rock fill Vernas Brazil Sand-rock fill Meiboro Japan Rock fill Randalas Mexico Rock fill Malibaso Anfrneelo Mexico Rock fill keeni Canada Rock fill Benefits of the HAD So the decision is taken to build HAD to achieve two main objectives. First, is to store the high quantity of flood water to use it in the case of drought instead of spilling to the sea and being exposed to be lost through evaporation due to the high temperature degrees all over the shallow depth wide areas of waters. Second, to use the high head of water developed due to the high difference between the U.S. and D.S. water levels to generate electricity on a global scale allover Egypt (Abu El Wafa,1967) The HAD has many advantages which can be listed as follows: (1) expansion of cultivation. (2) transfer 1 million fed from seasonal to perennial irrigation. (3) Protection from high floods. (4) Generation from hydropower. (5) Improvement of navigation.

6 On the other hand it has some disadvantages which can be listed as follows: (1) Fertility problem of the cultivation lands due to storage of the sediment U.S. the HAD. (2) Shore protection problem due to the erosion of the shores by the sea. (3) Some other social impacts. Some other social impacts for the HAD are the following :- (a) Improvement of the summer rotations and guaranteed availability of irrigation water at any predetermined period for agricultural production (b) Expansion in rice cultivation; (c) Transfer of about one million feddan from seasonal to perennial irrigation; (d) Agricultural expansion in 1.2 million feddan of new land owing to increased water availability; (e) Protection from high floods as in 1964 and 1975, and from low floods and droughts as in 1972,1979,1982,1985, 1986 and 1987; - generation of hydroelectric power; and (f) Improvement of navigation, and further increase in tourism, as a result of the stability of water levels in the Nile course and navigation canals. HAD other potential benefits such as the following :- (1) Egypt has completed the Toshka floodwater storage, about 150-km south of Aswan, to divert excess floodwater to the western desert. This project would assist in cultivating some areas of land around the Toshka depression and in the New Valley in the future, when sufficient quantities of water are stored in the depression or in the groundwater aquifers. (2) The dam enabled both Egypt and Sudan to begin a comprehensive study for optimal utilization of the Nile waters to increase water resources for the benefit of both countries. From the economic point of view - : The national income will increase by this rate in 1967:- (a) Agricultural expansion and transfer of seasonal to perennial irrigation = 100 million L.E (b ) Sure irrigation and improve of drainage = 75 million L.E. (c) Improvement of navigation = 2 million L.E. (d) Flood protection = 10 million L.E. (e) Hydropower production = 48 million L.E. (f) So the total of income will be = 235 million L.E. (g) If we add also the conservation of non-agricultural land to be agricultural land this value will be = 350 million L.E. (h) The benefit per year = 47% from the cost of the project and this is a big benefit for any type of projects.