Irrigation Department

Development Region II

CHOTIARI RESERVOIR
LEFT BANK OUTFALL DRAIN (LBOD)
SHAHEED BENAZIR BHUTTO SWEET WATER

CHOTIARI RESERVOIR PROJECT

INTRODUCTION : The Chotiari Reservoir is a strategically located off-canal storage reservoir situated approximately 20 miles east of Sanghar, within the graticule of N260 5' - 260 16' E 690-0 to 690 11'. It comprises several natural depressions or lakes, primarily Makhi and Baqar, enclosed by the Larkana-Naushehro Feroze Canal (LNC) and Thar Desert sand dunes. The reservoir's construction was commissioned in 2003 to increase the storage capacity of these lakes and enhance irrigation supplies to the Lower Nara Canal (LNC) command area. This introduction provides an overview of the geographical location and purpose of the Chotiari Reservoir.

Objective : The primary objective of the Chotiari Reservoir is to augment irrigation supplies to the land improved by the construction of the drainage system under the Left Bank Outfall Drain (LBOD) Stage-1 project. The reservoir acts as an off-canal storage facility, with its inflows controlled by the availability of excess water at the Sukkur Barrage and Jamrao head. By increasing the storage capacity of the lakes and storing water in the Chotiari Reservoir, the objective is to provide a reliable water source for the Lower Nara Canal, benefiting the Jamrao System.

Role : The reservoir plays a vital role in the water management system by receiving water from the Ranto Canal and the Aujo Escape, which are off-takes from the Jamrao Head and Makhi Complex respectively. With a significant embankment stretching 35.5 miles, the Chotiari Reservoir has one of the world's longest reservoir embankments. It stores 0.71 million acre-feet (MAF) of water, covering an area of 78 square miles at the Normal Pool Level of 87.5 feet. The Live Storage of the reservoir is 0.62 MAF. The LBOD-1 project further increased the storage capacity to 0.71 MAF to benefit the Jamrao System indirectly by feeding the Lower Nara Canal through the enhanced storage of the Chotiari Reservoir, as a direct transfer to the Jamrao system was not feasible.

In summary, the Chotiari Reservoir serves as a crucial off-canal storage facility, strategically located to provide irrigation supplies to the Lower Nara Canal command area and support the drainage system under the LBOD Stage-1 project. It plays a significant role in water management and aims to enhance water storage capacity to benefit the Jamrao System indirectly through the Upper Nara Canal.

RESERVOIR TECHNICAL & OPERATION OVERVIEW

  • With reference to Operation of Chotiari Reservoir, Project Components are divided into two parts, viz;

    • Sukkur Barrage Head Works
    • Ranto Canal Inlet Structure (Ex-Jamrao head)
    • Makhi Weir (New)

    • Dam Embankments
    • Ranto Canal Baffle Chute
    • Chotiari Outlet Structure
    • Feeder Outlet for feeding Excluded Lakes
    • Akanwari Pumping Station
    • Drainage Outlets between Southern Embankments and RLNC
  • Indent specifying gate opening of SKB Canals is governed by the information of river flows/storages volumes available in the Indus basin and is operated by SE KIC whereas, identification of excess water to be diverted to the Chotiari Reservoir via Ranto and Aujo escape canals exceeding Nara canal command, lies with Director NCAWB.
  • Primarily, the Chotiari Reservoir was constructed to augment irrigation supplies of Jamrao and LNC command areas of NCAWB.
  • Proposed diversion of 200 Cfs for Thar Coal, advocates revised operation rules for the Chotiari Reservoir to ensure shared distribution.

  • The Reservoir area mainly consists of LIB alluvial deposits of fine to medium sands, silts and clay deposits over a basement of Tertiary rocks known to be 600 ft. deep.
  • The sands met within the area are micaceous, fine to medium sand occasionally interbedded locally with varying thickness of clay and silt.
  • The large quantities of relatively coarser Thar Sand carried in earlier times when rivers flowed further to the East.
  • Deposits of uniformly graded dune sands are encountered particularly in the southeastern and eastern parts of the Reservoir.
  • One channel of the river passed through the site and the area was regularly flooded.
  • The northern periphery is entirely formed of the sand dunes varying in width from place to place.

  • Located west to north of the Reservoir (RD 0+0 to RD 65+408 of Reservoir Embankment), approximately 12 miles long.
  • The Zero point of the bund in the north is at RD 72 of Ranto Canal.
  • It encircles deh Akanwari such that RD 65+408 of the Reservoir embankment i.e. the end of Northern bund rejoins the LNC at RD 107+750.

  • This section (RD 65+408 to RD 109+028 of Reservoir Embankment) which is approx. 08 miles long is aligned adjacent to and on the reservoir side of the Non-Inspection Path of the LNC (from 106 to RD 152, as existed before it’s realignment).
  • The foundation for most of the alignment is clayey sandy silts or clayey silts.

This section (RD 109+028 to RD 160+309 of Reservoir Embankment) is approx. 10 miles long, was constructed on the foot prints of the LNC, (as it existed before its realignment, from RD 152 to RD 203).

  • The dykes, as many as 14 in number, are aligned along dunes lying east to south west at the south east limits of the reservoir.
  • This alignment of the dykes, starting RD 160+309 traverses 27+251 RDs, with total length of the embankment for about 16+473 RDs (3.12 miles long)
  • Height of the dykes varying from about 2.0 ft. to about 25 ft.
VIEW ON MAP

Dam Embankment Features:

Crest width provided was 20 ft. which subsequently reduced to 16 ft. on recommendation of the Chotiari Panel of Experts and the Dam specialist of the World Bank.

Freeboard provided is 9 ft. above the normal pool level to accommodate the following combinations found to be worst on various trials;
Mean Annual Max. Wave 05 ft.
Ranto stretched flow (7800 Cfs) for 6 days 02 ft.
100-y return 30 days rainfall + Ops failure 02 ft.
Controlling Design Levels therefore are;
Top of Embankment RL 96.5 ft.
Normal Res. Level RL 87.5 ft. and
Max. Drawdown Level RL 69 ft.

  • The emergency conditions due to which excess discharge has to be passed through Ranto Canal to Chotiari Reservoir include;
    • failure of Regulation at Sukkur Barrage
    • failure of Operations at Jamrao Head and;
    • breaches in LNC or Jamrao Canal system till its rehabilitation
  • If the Ranto Canal Conveys only up to its design discharge of 6500 Cfs, the provided freeboard can stand operation failure of 14 days
  • The calculation of days of Operation Failure that can be tolerated due to the extra freeboard of 2 + 2 ft. is based on the following figures of the reservoir capacities;
    At Normal Pool Level of 87.5 ft. 0.71 MAF
    At Elevation of 89.5 ft. 0.80 MAF
    At Elevation of 91.5 ft. 0.89 MAF
  • Direct precipitation over the Reservoir of 1 in 100 yrs. at the same time, will result in 9” encroachment in the freeboard which can be tolerated.

  • Upstream slope of the embankment with riprap in place varies from 2.5:1 from crest elevation to NPL, an to 3:1 from NPL to toe of the embankment.
  • Downstream slope is of the order of 2.5:1.

  • Upstream slope protection comprises 9”, 12”, and 18” riprap underlain by 6” thick layer of gravel, all placed over geo-synthetic textile, Terram 3000 or equivalent.
  • At water bodies of South Eastern Dykes the riprap is placed on the other side also i.e. on the side of excluded lakes but below RL 80 ft and up to RL 66 ft. i.e. below the dead storage level, as on the Chotiari Reservoir.

Downstream slope protection comprises 9” thick stone pitching.

  • Excess availability of water at Sukkur Barrage and then onward at the Jamrao Weir, which varies from Year to Year therefore, the water allocation to Lower Nara Canal would vary from time to time. Also, releases would need to be adjusted from time to time
  • Therefore, operation rules prescribed, always considered as general guide.
  • Supply to the LNC is planned to be dual, regular supply to the max. of 2600 Cfs through Jamrao headworks/Makhi Weir and seasonal supply to the max. of about 2600 Cfs from Chotiari Reservoir. But mix of those should not exceed 4000 Cfs i.e. the safe passing of LNC.

  • The inflow to the reservoir is designed to be 6500 Cfs through Ranto Canal.
  • Contribution of Aujo Escape to the reservoir operation of Chotiari is yet to be accounted.
  • The gross storage capacity of the Reservoir was raised from 0.21 MAF to 0.71 MAF under the Project by raising the NPL from 75.0 to 87.5 ft.
  • Dead Storage below the minimum drawdown level of 69 ft. being 0.09 MAF, the live storage comes to 0.62 MAF.
  • Dam Crest is at RL 96.5 ft., with controlled inflows, provides for operational failure and direct precipitation over the Reservoir when it is at NPL.
  • There is no site around the Reservoir for disposal of excess water during emergencies. to protect LNC system until the flow from Sukkur can be reduced, it will be necessary to route excess flows through Chotiari Reservoir, temporarily storing water in the freeboard zone, when unavoidable
  • Chotiari Outlet structure in addition to controlling releases into the LNC, is also designed to act as a spillway.
  • The excess water when the reservoir is at or below the retention level of 87.5 ft. can be passed safely to the LNC to the extent of 4000 Cfs which is its carrying capacity when releases from Jamrao head are stopped.
  • In case the LNC is running at its normal designed discharge of 2600 Cfs, it can safely pass only about 1400 Cfs.
  • At the NPL, with gates fully open, as much as 7816 Cfs can be released down to LNC, thus risking breaches in the LNC, as soon as the discharge exceeds 4000 Cfs.
  • A weir with its crest at RL 87.5 ft. has been provided above the gates of the Outlet Structure allowing uncontrolled flow over it.
  • With 2 ft. excess inflow absorption i.e. with pool level of 89.5 ft. excess that can be released through the structure with gates fully open is 9358 Cfs. With gates closed, it can pass about 1500 Cfs.
  • With pool level at 91.5 ft. when designed wave-freeboard will still be there the weir with gates closed can pass 2852 Cfs which can be safely accommodated by LNC, even with additional discharge of 1148 Cfs released through Jamrao Canal.
  • The design as above allows 6 days time for operations above the reservoir to be put in order and about 8 days with the risk of breaches in the LNC. Beyond this, the Reservoir itself will be in danger.
  • Any of the above two situations appear to be a remote probability, unprecedented in the history of operations of Irrigation Dept.
  • Despite, immediate reduction in flow in whole Nara system is not possible it takes about 04 days for water to pass from Sukkur to Chotiari.

The Ranto Canal, which operates under the supervision of the Head Jamrao operators and is administratively controlled by the Director NCAWB, features a set of inlet works to regulate its operation. The inlet works are designed to accommodate a flow rate of 6,500 Cfs . The alignment of the Ranto Canal follows that of the pre-existing Ranto Escape. Starting from an inlet regulator at Jamrao head, the bed level of the canal varies from RL 95.0 below the inlet regulator to RL 87.5, which corresponds to the Normal Pool Level of the Chotiari Reservoir. At the end of the canal, a baffled chute is in place to control the discharge of water into the Chotiari Reservoir. The inlet works play a crucial role in managing the flow of water from the Ranto Canal into the reservoir, ensuring efficient water supply and regulation.
VIEW ON IMAGE

Structure is designed as an uncontrolled weir to operate under wide range of downstream water levels, from dry downstream to Normal Reservoir Level.It is reinforced concrete construction, located 23 km from head and at the start of Northern bund.
VIEW ON IMAGE

The Chotiari Reservoir Outlet Structure is situated at RD 156+813 on the Southern Embankment, specifically RD 199+805 of the Larkana-Naushehro Feroze Canal (LNC). The outlet structure is designed to discharge a maximum flow rate of 2,600 cubic feet per second (Cfs) into the LNC and is controlled by ten vertical undershot gates. The gates' sill is located at RL 64.5 ft., which is below the minimum drawdown level of 69 ft. At the normal pool level of 87.5 ft., with the gates fully open, the structure has the capacity to discharge 7,816 Cfs.

Apart from controlling releases into the LNC, the outlet structure also serves as a spillway. It includes an uncontrolled weir located above the gates, with its crest at RL 87.5 ft., corresponding to the normal pool level. When the reservoir reaches the surcharge reservoir level of 89.5 ft., combined with the gates fully open, the structure can discharge 9,358 Cfs. During the months of July and August, when the reservoir is expected to be full, the gates will remain closed, and the reservoir level will be safe up to an elevation of 91.5 ft. With the gates fully open under this condition, the structure can pass a combined discharge of 11,720 Cfs.

In the event that the reservoir rises to an elevation of 94.5 ft., which is just 2 ft. below the embankment crest, the structure is capable of discharging 16,184 Cfs. However, under normal circumstances, except in emergencies, the release from the reservoir to the LNC will not exceed 2,600 Cfs. It is important to note that water should not typically be released from the Chotiari Reservoir when the water level is at or below its dead storage level of 69 ft. If water still needs to be released to the LNC, the gates should be kept open until it stops at RL 64.5 ft., which is the sill of the outlet. The outlet structure plays a critical role in managing the water flow from the reservoir and ensures controlled discharge into the LNC while maintaining the reservoir's safety and operational efficiency.

VIEW ON IMAGE - VIEW ON CHART

Feeder outlet structure located at RD 177+434 on the South Easter Dykes. It is provided to let water in the Excluded Lakes at an estimated average rate of about 30 Cfs or max. rate of about 40 Cfs.However, the outlet is capable of discharging 98 Cfs of water with max. head of 6.5 ft.The sill of the sluice is placed at RL 78 ft. It is operated when Chotiari Reservoir level is higher than that of the excluded lakes. Such that the level of Excluded lakes does not exceed RL 75.The structure is constructed as square conduit of 3.5X3.5 ft. provided with vertical lift gate combined with stop logs.
VIEW ON IMAGE

RCC pipe inlets, 12” dia., are provided in RLNC to drain the seepage and rainfall excess water trapped between Southern embankment and the RLNC.

PS is provided at RD 38+316 of the Northern bund to pump back the reservoir/canal seepage, surface drainage of Akanwari deh and storm drainage water to the reservoir.The PS is provided with 7 number – 20 Cfs electrically driven pumps.
VIEW ON MAP

Seepage Control Measures provided depend on the height of embankment, the type of foundation materials and conditions of downstream toe.
  • Toe Drain constructed as buried drain under the edge of embankment with fine/coarse filters and geotextile (Terram 1000 or equivalent) between earth and the perforated pipe is provided throughout except that no toe drain has been provided in case of Western Embankment which is integrated with NIP of the LNC. Perforated pipes 6” to 12” internal diameter placed in the toe drain lead seepage water to the collector drain.
  • Horizontal Drainage Blanket comprising fine and coarse filters enveloped in geotextile (Terram 1000 or equivalent), is provided where the embankment height exceeds 17 ft. except that no horizontal drain is provided in Western Embankment.
  • Chimney Drain, 24” thick, constructed with locally available dune sand is provided only in reaches where the height of embankment exceeds 20 ft. and the embankment and foundations consists of silty or clayey material.
  • Seepage water in case of Western Embankmen is directly disposed of into the LNC, and in the case of Southern Embankment it gets trapped into waste land between the Reservoir embankment and the LNC and is led through RCC pipes into the Canal.
  • Northern Bund seepage water is collected through the collector drains leading to the sumps constructed at Akanwari Pump Station at RD 38+316 from where it is pumped back into the reservoir.
  • South Eastern Dykes water collected through the collector drains is disposed of at the natural drainage lines into the Excluded Lakes.

  • Instruments have been installed in the Northern Bund, Western Embankment, Southern Embankment and South-Eastern Dykes to monitor the behavior of these embankments including their foundation.
  • No instrument are installed at the structures including the baffle chute, the outlet-cum-spillway and the feeder outlet.
  • The system provides measurement of pore water pressures, seepage flows and settlement.
  • The instruments include PVC tip standpipe piezometer, surface markers and weir in the collector drains.

Layout of Instrument Sections
  • All the instruments used are simplest ones, locally manufactured.Instruments were installed in Chotiari Reservoir Embankments after the construction of the embankments which commenced in September 1994 and was completed in December 2002.In all 05 Fully Instrumented piezometer Section (FIS) are chosen, covering the Northern Bund, The Western Embankment, the Southern Embankment and the South-Eastern Dykes.
  • Piezometers: Each FIS includes 05 Standpipes, two with their tips in embankment foundation, two with tips in the embankment body and one just above the blanket drain. One piezometer, in addition, is installed 5 ft. downstream of the toe of the embankment.However, in case of Western Embankment, number of piezometers in section has been reduced to three.A Standpipe piezometer placed in 6” dia. borehole consists of a porous tip sealed off to isolate it from pore pressures at elevations other than that of the tip. The Water surface can be detected using a dip-meter probe.
  • Surface Markers are installed for the purpose of measuring settlement in the reaches of the embankment where the embankment height exceeds 15 ft.Surface marker are simple concrete block with galvanized metallic plate fixed with a bolt at the center (surveying point) is embedded in the block at the top surface.
  • Seepage Measurement can be made at various location where discharge pipes are taken out of the toe drain. Southern Embankment and South-Eastern Dykes, V-notch flumes are provided at these locations for the purpose of measurement of flows in these embankments.
VIEW ON LOCATION

Over the course of four years, it has been observed that the Chotiari Reservoir has not reached its Normal Pool Level of 87.5 ft. due to limited availability of water in the river. The maximum recorded storage level was approximately 86.5 ft., resulting in a storage volume of 0.67 million acre-feet (MAF). To meet the crop water requirement of the Lower Nara Canal (LNC), the reservoir experienced a maximum drawdown to RL 75 ft. The data indicates a consistent trend in the filling and consumption of the reservoir. There is a volume of approximately 0.136 MAF between the maximum drawdown level and the dead storage level at RL 69 ft., which remains unutilized. Additionally, there is a need to accommodate the newly envisaged scheme of supplying 200 cubic feet per second (Cfs) to Thar Coal, which would require a volume of 0.145 MAF. This scenario highlights the importance of fully utilizing the storage capacity of the reservoir to meet various water demands effectively.
RESERVOIR LEVELS - RESERVOIR FILLING - ELEVATION CURVE

Chotiari Gauges & Levels

Chotiari Images & General Maps

LBOD PROJECT

Background : The Left Bank Outfall Drain (LBOD) Project, approved by the International Development Association (IDA) on December 13, 1984, received a credit of $150 million. LBOD Stage I, implemented between 1984 and 1997, aimed to address waterlogging and salinity issues in 1.27 million acres across Shaheed Benazirabad, Mirpurkhas, Sanghar, and Badin Districts. The project's key component is the Spinal drain, which connects the drainage network to the sea through a Tidal Link. The LBOD spinal drain collects excess drainage and distributes it through a weir to two branch drains, the Kadhan Pateji Outfall Drain (KPOD) and the Dhoro Puran Outfall Drain (DPOD). The system was designed to direct highly saline drainage into the KPOD and ultimately to the sea via the 26-mile long canal known as the Tidal Link.

Introduction : The LBOD Project, initiated in 1984, aimed to mitigate waterlogging and salinity issues in several districts by establishing a drainage network connected to the sea through the Spinal drain and Tidal Link. However, concerns about potential ecological impacts arose regarding the Tidal Link, leading to the construction of protective measures such as raising the northern side and building the Cholri weir. Despite these efforts, operational challenges emerged, including erosion, scouring, and the collapse of a section of the Cholri weir. In 1999, a catastrophic cyclone caused severe damage, exacerbating the deterioration of the Cholri Weir and breaching the Tidal Link embankment. As a result, the LBOD has transformed into a "new river," forming an estuary and affecting coastal areas with visible tidal fluctuations. Adapting to this evolving process requires continuous hydraulic and environmental monitoring.

Objective : The objective of the Project is to alleviate waterlogging and salinity issues in Shaheed Benazirabad, Mirpurkhas, Sanghar, and Badin Districts. The project effectively managing excess drainage through the Spinal drain, which directs high salinity drainage into the Kadhan Pateji Outfall Drain (KPOD) and ultimately to the sea via the Tidal Link. However, challenges such as ecological impacts, structural integrity, and the unpredictable transformation of the LBOD into an estuary persist.

LBOD Administrative Transformation : The LBOD Spinal drain was initially handed over to the Irrigation Department of the Government of Sindh in 1993. However, the system faced difficulties and caused damages during heavy rains in the monsoon of 1994. Consequently, the system was returned to the Water and Power Development Authority (WAPDA) in 1995. On February 1, 2002, WAPDA transferred the LBOD System back to the Irrigation Department/Sindh Irrigation and Drainage Authority (SIDA).

The LBOD Spinal drain was initially handed over to the Irrigation Department of the Government of Sindh in 1993. However, the system faced difficulties and caused damages during heavy rains in the monsoon of 1994. Consequently, the system was returned to the Water and Power Development Authority (WAPDA) in 1995. On February 1, 2002, WAPDA transferred the LBOD System back to the Irrigation Department/Sindh Irrigation and Drainage Authority (SIDA).

LBOD Maps

Plan Maps

  • LBOD System
  • Drainage Divisions
  • Other

Index Plan

Left Bank Outfall Drain (LBOD)

Layout Plan

LBOD / Dhoro Map

Salient Features

Index Plan

Index Plan

LBOD Project

Hyderabad

Sanghar

Drainage Division

Mirpukhas

Drainage Division

Drainage Divisions

Left Bank Outfall Drain (LBOD)

Index Plan

Left Bank Outfall Drain (LBOD)

Layout Plan

LBOD / Dhoro Map

Salient Features

LBOD / Dhoro Map

Salient Features

Other

Other

Other

Other

SHAHEED BENAZIR BHUTTO SWEET WATER PROJECT FOR THAR

Providing Water from Kot Wah of Umer Kot to Keetari Taluka Chachro via Dhalo Jo Tar, Kaplore, Viklore Tar, Budha Sandha, Vechlo Par, Ratan Jo Tar and Constructing of Underground Reservoirs

Tharparkar, a vast district spanning over 20,000 square kilometers, is located in Pakistan's southern Sindh province. As Pakistan's largest district and the 18th largest desert in the world, Tharparkar presents a juxtaposition of beauty and adversity. Behind the alarming mortality figures lies a deeper set of issues, including water scarcity, poverty, and illiteracy, which pose significant challenges to the 1.5 million people residing in this region.

Over time, the rain ponds and wells in Tharparkar become contaminated with saline and arsenic, leading to major health issues and fatal diseases in the desert region. Water, being an essential element for the survival of mankind, remains a haunting scarcity for the people of Tharparkar. Every year, at least 400 children lose their lives due to malnutrition and waterborne diseases.

In Tharparkar, the only source of fresh water is the annual rainfall, which is limited to a mere 100-500 mm per year, mostly occurring between July and September. The people of Thar rely on storing rainwater in Tarais (small reservoirs) to sustain themselves throughout the year, but this supply is often insufficient. Women in Tharparkar undertake the arduous task of traveling 4 to 5 kilometers daily to fetch water on their shoulders from wells and Tarais.

To address these pressing challenges, the BENAZIR BHUTTO SWEET WATER PROJECT FOR THAR (UMERKOT TO KEETARI) has emerged as a ray of hope. This project aims to provide sweet, fresh water to 70 major villages in Thar, covering the area from Umerkot to Keetari. The project targets the current population of 231,010 individuals and anticipates serving the future population of approximately 500,000 people drawn from the Thar Canal.

The SHAHEED BENAZIR BHUTTO SWEET WATER PROJECT FOR THAR serves as a critical step forward in safeguarding the people of Tharparkar from impending catastrophe. By ensuring access to a sustainable and reliable source of fresh water, this initiative seeks to alleviate the hardships faced by the residents, improve their health outcomes, and contribute to their overall well-being.

SHAHEED Benazir Bhutto Sweet Water Project (umerkot to Keetari)

63 Million-gallon reservoir

Pumping Station

Control Room

Hydrostatic Testing

Solar System at Zero Point

Black Steel Pipe

0.55 Million-gallon R.C.C Tank at Chachro

Children fetching sweet water from R.C.C Underground tank built

R.C.C Undergroud Tanks
Tank capacity Number of Tanks
20,000 Gallons 4
50,000 Gallons 66
60,000 Gallons 38
80,000 Gallons 21
Total 129
Main Pumping Station at Zero Station Umerkot
No. of Pumps 6 (4 operating, 02 standby)
Capacity of each pump 88 L/sec at 6250ft Head
Each Pump Horse Power 252 HP (250 KW)
Daily Water Requirement 5.85 MGD
Storage Reservoir Capacity 63 MG(50 % requirement during closure)
Booster Pumping Station at Handakar
No. of Pumps 4 (3 operating, 01 standby)
Capacity of each pump 137 L/sec at 550ft Head
Each Pump Horse Power 74 HP (250 KW)
Daily Water Requirement 2.50 MGD
Storage Reservoir Capacity 19 MG