Mangla Dam

Mangla Dam Project was actually conceived in 1950's as a multipurpose project to be constructed at a place called Mangla on river Jhelum located about 30 km upstream of Jhelum city (120 km from Capital Islamabad). The initial investigation and its feasibility studies were completed in 1958. Later on the project was included in the Indus Basin Project. Mangla Dam is the 12th largest dam in the world. It was constructed in 1967 across the River Jhelum, about 60 miles southeast of the federal capital, Islamabad. The main structures of the dam include 4 embankment dams, 2 spillways, 5 power-cum-irrigation tunnels and a power station. The main dam is 10,300 feet long and 454 feet high (above core trench) with a reservoir of 97.7 square miles. Since its first impounding in 1967, sedimentation to the extent of 1.13 MAF has occurred, and the present gross storage capacity has reduced to 4.75 MAF from the actual design of 5.88 MAF. The live capacity has reduced to 4.58 MAF from 5.34 MAF. This implies a reduction of 19.22 % in the capacity of the dam. The construction of Mangla Dam was started in 1962 and completed in 1967.

PURPOSE OF THE PROJECT
Mangla Dam is a multipurpose project primarily meant for affecting part replacement of water supplies of three eastern rivers from Jhelum River. Besides, it is designed to conserve and control flood water of river Jhelum through significant reduction in flood peaks and volumes at downstream by incidental use of the available storage space. The other by products are power generation to meet the power demand of the country, fish culture to provide protein rich diet, tourism to provide healthy recreation facilities to the people and navigation.

PROJECT COMPONENTS
The project consists of two dams (Main Dam & Jari Dam), two dykes to contain reservoir, two spillways for outflow regulations, intake structures with five tunnels, a powerhouse and a tailrace canal.

POWER HOUSE
Power House has been constructed at the toe of intake embankment at the ground surface elevation of 865 ft. SPD. The water to powerhouse is supplied through five steel lined tunnels of 30/26 ft. diameter. Each tunnel is designed to feed two generating units. The powerhouse tailrace discharges into New Bong Canal, which has a length of 25,000 ft. with discharge capacity of about 49,000 cusecs, and terminates at an automatic gate control headwork at about 12 km downstream located near old Bong Escape Headwork. Power Station was completed in four stages. The initial phase comprising of four units of 100 MW each was completed in 1967~1969. The first extension of Units 5~6 (2 x 100 MW) was completed in 1974 while second extension comprising of Units 7~8 (2 x 100 MW) was completed in 1981. The project attained its maximum capacity of 1000 MW with the final extension of Units 9~10 (2 x 100 MW) in 1993/94. During the high reservoir level period, Mangla is able to generate 1150 MW against the rated capacity of 1000 MW due to permissible overloading of 15% whereas the capacity reduces to about 500 MW in the lean flow period (winter season) due to low reservoir level.

KEY FACTS

Dam Type:	Earth fill
Height:	380 ft. (above riverbed
Length:	10,300 feet
Lake Area:	97.7 sq. miles
Catchments Area:	12,870 Sq miles
Gross Storage Capacity:	5.88 MAF
Live Storage Capacity:	5.34 MAF
Main Spillway Capacity:	1.01 million cusecs
Water Source	Jhelum River
Year of Completion:	1967
Hydropower Generation:	1,000 MW from 10 units of 100 MW each

HISTORIC DEVELOPMENT
In April 1948, India diverted the flow of the Ravi, Sutlej and Beas rivers, and an act, which threatened irrigated cultivation in Pakistan. That same year, in an effort to mitigate the consequences of possible interference by India with the supplies of the canals feeding from those rivers, Pakistan embarked on a program of link canal construction to enable the transfer of water between rivers.
Until 1967, the entire irrigation system of Pakistan was fully dependent on unregulated flows of the Indus and its major tributaries. The agricultural yield was very low for a number of reasons, the most important being a lack of water during critical growing periods. This problem stemmed from the seasonal variations in the river flow and the absence of storage reservoirs to conserve the vast amounts of surplus water during periods of high river discharge.
Mangla Dam was the first development project undertaken to reduce the shortcoming and strengthen the irrigation system.

THE MANGLA DAM PROJECT
The project was designed primarily to increase the amount of water that could be used for irrigation from the flow of the River Jhelum and its tributaries. Its secondary function was to generate electrical power from the irrigation releases at the artificial head of the reservoir. The project was not designed as a flood control structure, although some benefit in this respect also arises from its use for irrigation and water supply.

MAIN ELEMENTS OF MANGLA DAM
The Mangla Dam components include a reservoir, main embankment, intake embankment, main spillway, emergency spillway, intake structures, 5 tunnels and a power station. Besides the main dam, a dyke called Sukian - 17,000 feet in length and a small dam called Jari Dam to block the Jari Nala - about 11 miles beyond the new Mirpur town had to be constructed.
There was a total of 120 x 106 yds3 of excavation for the reservoir whereas the total fill amounted to 142 x 106 yds3 and concrete to 1.96 x 106 yds3 respectively. The main embankment is earth fill with clay as the core material. Gravel and A-type sandstone are applied on the shoulders. The maximum height of embankment above the core trench is 454 feet and the length is 8,400 feet. The intake embankment is earth fill type with B-type sandstone as the core material. Gravel is applied on the shoulders. The maximum height of intake embankment above the core trench is 262 feet and the length is 1,900 feet.