For official use only Doc.

WRD 16(15951)P
July 2020

BUREAU OF INDIAN STANDARDS

Draft Indian Standard

Surveillance and Performance Monitoring of Hydraulic Structures -

Guidelines

(Not to be reproduced without the Permission of BIS or used as a STANDARD)

Last date for receipt of comments is : 13/ 08/ 2020

FOREWORD
(Formal clauses will be added later)

Surveillance of dams during their construction, reservoir filling, and operation is an essential
activity in a dam safety program. The level of surveillance should be appropriate to the
individual dam considering its type, foundation, design, construction, operational context,
consequences of failure, inherent condition, historical performance, characteristic behaviour
and potential failure modes. Surveillance plays a critical role in ensuring safety of existing
dams, whose failure can result in unacceptable loss of life and economic losses.

The objective of surveillance is to monitor dam and foundation performance, compare

performance with expected behaviors, and ensure that the characteristic behaviors are well
understood for a range of loading conditions.It should provide a baseline of performance
information against which future changes in performance can be assessed. It should provide
accurate and consistent data throughout the life of a dam and also be robust and auditable. It
should be emphasized that any time the reservoir goes above its previous historical
maximum; the surveillance program should reinitiate the first filling protocol.

A robust surveillance process is the Owner’s ‘front line of defense’ for the safe operation of
their dams and reservoirs. Surveillance provides the cornerstone for effective management of
dam safety and operational risks and includes visual inspections, instrument monitoring
(including deformation surveys), data review and evaluation, and reporting on the safety of
the dam.

For the preparation of this standard, references have been drawn from ICOLD Bulletins, and
United States Army Corps of Engineers (USACE ) documents.
 BUREAU OF INDIAN STANDARDS
Draft Indian Standard

Surveillance and Performance Monitoring of Hydraulic Structures -

Guidelines

1. SCOPE

The standard covers the general guidelines on surveillance and performance monitoring
of hydraulic structures.

2. TYPES OF INSPECTIONS

2.1 An overview of the various types of inspections is given below:

Four different types of dam safety inspections are carried out for all dams:
1. Informal inspections
2. Scheduled inspections (Pre & Post monsoon inspections & other scheduled inspections)
3. Special (unscheduled) inspections
4. Comprehensive evaluation inspections

2.1.1 Informal Inspections

An informal inspection is a continuing effort by on-site personnel (dam owners/operators and
maintenance personnel) performed during their normal dutiesincluding everyday operating
conditions. Informal inspections envisage surveillance of the dam periodically and are critical
to the proper operation and maintenance of the dam. It targets specific aspects of dam and/ or
foundation performance but should include the entire locale in the event there is an unusual
response elsewhere. They consist of frequent observations of the general appearance and
functioning of the dam and appurtenant structures.

Normally the dam owners, operators, maintenance crews, or other staff who are posted at
dam site will make informal inspections. These people are the “first line of defense” in
assuring safe dam conditions, and it is their responsibility to be familiar with all aspects of
the dam. Their vigilance in inspection/surveillance of the dam, checking the operating
equipment, and noting changes in conditions may prevent serious mishaps or even dam
failures.

Informal inspections are important and should be performed at every available opportunity.
These inspections may only cover one or two dam components as the occasion presents itself,
or they may cover the entire dam and its appurtenant structures. The informal inspections are
not as detailed as comprehensive evaluation, scheduled, and special inspections and will only
require that a formal report is submitted to the dam owner’s project files if a condition is
detected that might endanger the dam.
However, intensive inspection is required when there is a confirmed dam safety deficiency or
a developing dam safety threat. It is often round the clock, with experienced personal.

2.1.2 Scheduled Inspections

Scheduled inspections shall consist of Pre-monsoon & Post-monsoon inspection and any
other inspections carried out by the State Dam Safety Organization/any Expert panels
constituted by the dam owner.

These inspections are performed to gather information on the current condition of the dam
and its appurtenant works. This information is then used to establish needed repairs and
repair schedules, and to assess the safety and operational adequacy of the dam. Scheduled
inspections are also performed to evaluate previous repairs.

The purpose of scheduled inspections is to keep the dam and its appurtenant structures in
good operating condition and to maintain a safe structure. As such, these inspections and
timely maintenance will minimize the long-term costs and will extend the life of the dam.
Scheduled inspections are performed more frequently than comprehensive evaluation
inspections to detect at an early stage any developments that may be detrimental to the dam.
These inspections involve assessing operational capability as well as structural stability and
detection of any problems and to correct them before the conditions worsen. The field
examinations should be made by the personnel assigned responsibility for monitoring the
safety of the dam. If the dam or appurtenant works have instrumentation, the individual
responsible for monitoring should analyze measurements as they are received and include an
evaluation of that data. Dam Inspection Report or an inspection brief should be prepared
following the field visit (Dam Inspection Report is recommended).

2.1.2.1 Scheduled inspections should include the following four components as a minimum:
a) Review of past inspection reports, monitoring data, photographs, maintenance records,
or other pertinent data as may be required;
b) Visual inspection of the dam and its appurtenant works;
c) Preparation of a report or inspection brief, with relevant documentation and
photographs.
d) Education and training if someone other than the owner is performing the inspection.

2.1.3 Special (Unscheduled) Inspections

Special inspections may need to be performed to resolve specific concerns or conditions at
the site on an unscheduled basis. Special inspections are not regularly scheduled activities,
but are usually made before or immediately after the dam or appurtenant works have been
subjected to unusual events or conditions, such as an unusually high flood or a significant
earthquake.
Japan Water Agency (JWA) has developed an excellent system of carrying outinspections
after an earthquake event. For details refer “Inspection Manual for Dam Field Engineers after
Seismic Events, Ichari Dam, Uttarakhand (CDSO_MAN_DS_01_v1.0), January 2018” The
threshold acceleration adopted by them for carrying out inspection is when the acceleration
recorded at dam foundation exceeds 25 gals (25 cm/sec2). It is proposed to adopt their system
in our guidelines. The system envisage a quick check within 1 hour after the earthquake
event, next i.e. first check within 3 hours and a second check within 24 hrs.

2.1.3.1 The quick check will envisage:

a) Confirming the seismic intensity at the dam site.

b) Sending initial report regarding an assessment of a possible dam failure.
c) Finding out urgent rescue needs.

2.1.3.2 The first inspection will envisage:

a) Visual inspection by competent and trained personnel is the most effective means of
dam surveillance. Visual observations of leakage/ seepage, deformations, cracking in
dam, slope failure, collapse of any component, functioning of gates and electrical
devices, hill slopes (upstream and downstream of the dam), roads etc.
b) It is very important that the developed checklist of each dam should not be so
prescriptive that the inspector is not encouraged to look at other areas and features
that may have a bearing on dam safety and this principle should be emphasized in the
inspector’s training. Photographs of general and specific features, from repeatable
locations provide an effective long term record of inspection observations.
Video recording of features or unusual events can also be particularly valuable.
c) Confirming any subsequent action to be taken.

2.1.3.3 The second inspection will envisage:

a) Quantitatively measuring leakage, deformation and other monitoring items.

b) Verifying function of facilities by actual movement.

2.1.3.4 Further the following activities are also recommended to minimize the adverse
impacts of an earthquake
a) Regular field drills at dam site to make the site officials aware of their roles and
responsibilities during and after an earthquake event and thereby to upgrade the
earthquake response system
b) Securing communication lines by having a redundancy in the system by way of
availability of different types of telecommunication systems (viz. mobile phone,
wireless, satellites, telephone etc.) at dam site.
c) Securing adequate fuel for at least 3 days (viz. petrol, diesel) for the emergency power
generators and other essential supplies like food, water, fire wood etc.
d) Installation of seismometers in a dam and development of a data sharing system.

2.1.4 Comprehensive Evaluation Inspections

2.1.4.1 General
For comprehensive dam safety evaluation for each dam an independent panel of experts
known as Dam Safety Review Panel (DSRP) needs to be constituted for determining the
condition of the dam and appurtenant works. The panel would undertake evaluation of each
dam once in 10 years or on occurrence of any extreme hydrological or seismic event or any
unusual condition of the dam or in the reservoir rim. The terms of reference of the
comprehensive dam safety evaluation shall include but not be limited to;
a) General assessment of hydrologic and hydraulic conditions, review of design flood,
flood routing for revised design flood and mitigation measures.
b) Review and analysis of available data of dam design including seismic safety,
construction, operation maintenance and performance of dam structure and
appurtenant works.
c) Evaluation of procedures for operation, maintenance and inspection of dam and to
suggest improvements / modifications.
d) Evaluation of any possible hazardous threat to the dam structure such as dam
abutment slope stability failure or slope failures along the reservoir periphery.
e) The surveillance process can be thought of as a ‘quality chain’ – a multi-linked chain
where each step in the process form sacritical link remarks.

The quality chain starts with the personnel undertaking surveillance activities in the
field, continues with regular review of the information by appropriate technical specialists,
and is completed with feedback to the field personnel (relative to the nature of continued
surveillance) and reporting to the owner on the safety of the dam and the need for specific
responses or required actions.

2.1.4.2 Details to be provided to DSRP or expert Consultants before inspection

All relevant details/data/drawings for the dam project to be inspected by the Panel of Experts
shall be provided at least 3 months in advance of the proposed visit. This will should
include:-

(a) General Information

i. Scope of project
ii. Basic data and salient features
iii. Issues related to safety of dam
iv. Details of key personnel
v. Emergency preparedness – Communications, Auxiliary Power, Downstream Warning
system & Security of site.
(b) Hydrology
i. Description of drainage basin
ii. Original inflow design flood
iii. Spillway capacity at FRL & original MWL
iv. Surface area & storage capacity of the reservoir
v. Flood routing criteria & results
(c) Geology
i. Dam site geology including geological reports
 ii. Quality and sufficiency of the geological investigations.
iii. Special problems and their treatment
iv. Reservoir competency as per geological report.
v. Slope stability issues along reservoir rim.
(d) Layout including Drawings
i. Dam
ii. Spillway
iii. Junction between Embankment & Concrete/Masonry dams
iv. River/Canal outlets
v. Instrumentation
(e) Dam and Spillway
i. Geology
ii. Special problems
iii. Foundation treatment including treatment of faults/shear zones/ weak zones,
curtain/consolidation grouting, drainage provisions, any other special treatment,
cutoff trench, diaphragm walls etc.
iv. Design criteria and result of stability analysis
v. Special studies (Finite element/Dynamic Analysis etc.)
vi. Adequacy of design – from dam safety considerations
vii. Hydraulic design of Spillway and Energy Dissipation Arrangements including past
model study reports.
viii. Instrumentation – analysis and interpretation of instrumentation data including
structural behavior reports.
ix. Pre-construction material testing reports including adequacy of field and laboratory
investigations, appropriateness of materials selected etc.
x. Post-construction testing reports, if any.
xi. Seismicity (Seismic Parameters approved by the National Committee for
Recommending Seismic Design Parameters for Dams)
f) Construction history
g) Dam incidents/failures, remedial measures /modifications undertaken
h) Reservoir Operation & Regulation Plan
i. General
ii. Reservoir filling
iii. Water releases – normal and during floods.

2.1.4.3 Field Inspection – Observations & Recommendations regarding Remedial

Measures
Each component of the project is to be inspected; evaluated and specific problems are to be
brought out. Recommendations for necessary remedial measures need to be included in the
panel’s report. Various project components to be inspected shall include but will not be
limited to:

a) Dam
i. Upstream face
ii. Downstream face
iii. Top of dam
iv. Structural behavior as observed visually and as per evaluation of instrumentation
data (any visible cracking, deflections etc.)
v. Seepage assessment
vi. Condition of natural/excavated slopes in the abutments, both on u/s and d/s of the
dam.
vii. Any specific problems/ deficiencies
(b) Spillway
i. Civil structure
ii. Energy Dissipation Arrangements (EDA)
iii. Spill channel, drop structures etc. if any.
iv. Condition of EDA and its performance
v. Spillway Gates & Hoists
vi. Downstream safe carrying capacity of river / channel.
(c) River / Canal Outlets
i. Civil structures
ii. Outlet Gates, Hoists & Controls
iii. Conduits / Outlets through Embankment dams and sluices through Masonry /
Concrete dams (Condition, problems etc.)
iv. Trash racks, if any
v. Separate energy dissipation arrangements, if any.
(d) Review of Sedimentation of the Reservoir.
Assessment of sedimentation and its effect on flood routing, operation/ life of reservoir.
(e) Flood Hydrology
i. Extent & sufficiency of data available
ii. Method used for estimating the design flood.
iii. Design flood review study.
iv. Flood routing studies with the revised flood
v. Adequacy of free board available
(f) Miscellaneous services /facilities
i. Access Roads / Bridges / Culverts
ii. Elevators
iii. Stand by power arrangements
iv. Flood forecasting arrangements, if any
v. Communication facilities (Telephone, Satellite, Wireless, Mobile etc.)
(g) Hydraulic Model studies, if any new studies carried out.
(h) Earlier reports of experts / DSRP etc., if any, as annexures.
(i) Photographs of dam project showing problem areas.

2.1.4.4 Components involved

A comprehensive evaluation inspection of a dam will typically consist of five components:

a) Project records review (i.e. study of all design / construction records/ drawings,
history of the dam’s performance, past inspection notes/reports, notes on distress
observed/ any rehabilitation measures undertaken earlier etc.).
b) Visual inspection or field examination of the dam and its appurtenant works.
c) Preparation of a detailed report of the inspection.
d) Education and training of the dam owner on the issues observed during dam
inspection, identification of potential dam failure modes & to carry out additional
field investigations & laboratory testing as required. Dam owners should be made part
of the inspection process so that they take ownership of the results and are committed
to implementing the recommended remedial measures.
e) Design studies e.g. review of design flood, checking of the adequacy of spillway
capacity, freeboard requirements, dam stability, any special study as required &
submission of the report.
A comprehensive evaluation inspection should include a Potential Failure Modes
Analysis workshop. After the team has reviewed the available material and performed
their site visit, a PFMA workshop should be convened. The workshop should have a
facilitator and the participants should be composed of a diverse group in the fields of
structural, geotechnical, geology, materials, hydrology, hydraulics, mechanical,
operations, instrumentation, and seismology. There is significant available literature on
how to conduct a PFMA workshop actually, a PFMA workshop is actually one of the
more important first steps to take to determine the safety of a dam. The PFMA will help
identify the critical findings of the Comprehensive Review and will prioritize the failure
modes.

3. PERFORMANCE MONITORING INSTRUMENTATION

A brief overview of Instrumentation is provided here.

3.1 Various options and layouts are considered while planning instrumentation in dams and
for monitoring their performance. Where possible, when determining what instruments are
required to monitor the performance of a dam throughout its operational lifetime, Owners and
Technical Advisers should adopt a ‘simple and targeted’ instrumentation philosophy. All dam
instrumentation should have a clear purpose that is linked to one or all of the following
objectives:
a) Improving the understanding of a dam or foundation’s characteristic behavior during
normal operation, and during unusual and extreme events.

b) Providing early indication of the onset of potential failure modes for a dam.

3.2 Instrumentation can assist with the identification of the trends or conditions that are
indicative of a potential failure mode that was not identified during earlier studies. For
example, uplift measurements in gravity dams can give an idea whether the uplift pressure
are more or less than the design values. It can also provide an idea regarding the condition of
foundation drainage holes viz. whether in working condition or choked. If choked then
cleaning / re-drilling of holes will be necessary from dam stability considerations.

3.3 Dam performance monitoring instruments should be robust, durable, require little
maintenance and able to be read easily and consistently, often by non-specialist personnel.
That is, it should measure as directly as possible a parameter, condition or quantity that
supports the aforementioned dam performance monitoring objectives. The operational
lifetime of a dam is typically tens of decades, and the surveillance instrumentation should be
selected so that either it has a similar lifespan, or that components with a shorter life can be
safely maintained and/or replaced. The instrumentation data should be graphed and reviewed
in a timely manner by a qualified engineer. Threshold and Action Levels should be
established on the graphs and the appropriate responses to be taken when these levels are
exceeded. Also, the instrumentation should be linked to a Potential Failure Mode.

3.4 The overall dam instrument layout / array should be resilient and should provide for
redundancy as appropriate. Redundancy is specifically important for dams where piezometric
(or uplift) information is measured using vibrating wire instruments, or where it is gathered
and reported using telemetry or other means of electronic transmittal that can be affected by
lightning strikes or power loss. In such cases backup manual measurements of embankment
piezometers or uplift pressures in concrete dams at key locations should be provided.

3.5 Survey monuments installed to allow measurement of a dam’s deformation or settlement

(or the displacement of an appurtenant structures) are not typically considered to be
instrumentation, however they do provide the same function in that they can yield important
information relative to some potential failure modes and allow the behavior of the dam to be
monitored.

3.6 Dam performance monitoring instruments predominantly measure geotechnical,

hydrologic or structural parameters.

3.7 The need for and value of dam performance monitoring instrumentation will depend on
the requirements for the particular dam. Most instrumentation is selected during dam design
and installed during construction, and may have a primary purpose related to the monitoring
of construction-related parameters rather than those parameters required for the long- term
management of dam safety. Hence, it may be appropriate to consider additional instruments
to ensure dam performance monitoring needs are met or, where instruments are found to be
redundant, it may be appropriate to decommission instruments. Additional or different
instrumentation may also be installed when a potential dam safety deficiency is being
investigated and assessed.

3.8 Technological advances in instrumentation types and systems will occur over the life of
any dam. It is therefore likely that the original instrumentation will be augmented or replaced
by new systems over time. Where possible, a period of monitoring overlap should occur to
ensure that historical data can be correlated to information obtained from new systems.

4 KEY DAM PERFORMANCE PARAMETERS AND INSTRUMENT TYPES

4.1 Universal to all dams, the most important parameters that need to be measured
quantitatively and evaluated are:
a) Reservoir and tail-water levels.
b) Reservoir inflow and outflow levels
c) Accelerometer in high seismic areas.
d) Dam and foundation seepage and/or leakage rates.
e) Dam/abutment internal water pressures and phreatic surfaces.
f) Foundation uplifts pressures.
g) Dam deformation and displacement.
The above key parameters for embankment and concrete / masonry dams are shown
diagrammatically in Figures 1 and 2.

Fig. 1 Diagram showing parameters for embankment dams

 Fig.2 Diagram showing parameters for concrete.masonry dams

4.1.1 Reservoir Level

The Reservoir level is a fundamentally important measure of the loading on the dam and
therefore the head that the dam and its foundation are subject to and the freeboard available to
avoid overtopping. As a minimum, reservoir level should be recorded whenever visual
inspections and instrumented measurements are carried out so that the effect of the reservoir
loading with reservoir at different levels on the various engineering parameters can be studied
/evaluated.
While water level sensor instruments are commonly employed (allowing automated and
frequent monitoring), a water level staff gauge that can be read manually should be installed
in all reservoirs. Water level staff gauges are simple, effective and reliable (they do not need
a power source or have any electronic components) and where water level sensors are
installed they provide an important calibration check.
Water level staff gauges should be dimensioned to allow measurement of the fully
operational (including flood) range of reservoir levels and positioned so that they can easily
be read in all loading and weather conditions. They should also be sited to allow reading
without placing personnel at risk. Reservoir level should optimally be measured in meters
above mean sea level for ease of correlation with dam features and other measured
performance parameters such as piezometric levels and foundation uplift, seepage etc.

4.1.2 Seepage and/or Leakage Rate

Seepage and/or leakage rate in an embankment dam is an indicator of the performance of

impermeable (or low permeability) elements installed in the dam and foundation, and the
performance of the abutments and foundation where no impermeable elements are installed.
The objective of measuring seepage flows is generally more about the identification of
seepage trends and understanding the overall performance of the dam, rather than the
recording of absolute values. Decreasing seepage flows may need to be scrutinized just as
much as increasing seepage flows as they may indicate a change that is unacceptable.

The ability to measure rate of seepage and leakage through the embankment dam, its
foundation or abutment usually relies on directing the seepage or leakage, through
appropriate collection and drainage facilities, to a measurement point close to the dam’s toe
or at the location where the seepage or leakage emerges from the dam, foundation or
abutment.

Seepage and leakage flow is best measured volumetrically, either by measuring the time to
fill a container of known volume, or by installing a weir or flume with a theoretical (or
calibrated) rating that allows the measured head to be converted to flow rate. For the purpose
of ongoing monitoring and evaluation of a embankment dam’s performance the most
important aspect of seepage and leakage rate measurement is repeatability, rather than
absolute precision. Weirs should be sized for the anticipated flows and weir boxes should be
large enough to provide calm water surfaces behind the weir plates. In some cases baffles
may be needed to achieve this. V-notch weirs provide precision for the measurement of
seepage flows; however, for large flows, broad crested weirs or flumes will be necessary.

The observation of seepage and leakage flows via the use of weir also allows the detection of
any materials being transported by the seepage flows. The detection of turbid seepage or soil
particles in seepage flows is important as they may be an indicator that internal erosion
(backward erosion or piping or washing of the fines) is taking place within the dam, in its
abutments or in the foundation. In order to detect whether or not soil particles in a weir are
the results of internal erosion, the weir may have to be covered to protect it from windborne
material and periodically cleaned to enable the captured material to be examined and
weighed.

In case of Masonry/Concrete dams the seepage is measured in foundation gallery as well as

in inspection galleries at higher levels. Excessive seepage is an indicator of poor quality of
work, existence of low density areas, voids / segregation, poor lift joints in concrete dams etc.
Upstream pointing, grouting of dam body in masonry dams & grouting of lift joints in
concrete dams may be required is such cases.

Monitoring of any erosion or transport of material is important. As with Camera Dam in

Brazil, joint material in the foundation was eroding away causing a piping failure under the
concrete dam.
4.1.3 Internal Water Pressure and Foundation Uplift Pressure
Internal water pressure and foundation uplift pressure are measured to allow the stability of
the dam to be evaluated and to compare them with design assumptions. The absolute
measured values are therefore of prime importance; however, changes recorded over time
also need to be examined and understood. Water pressure is usually measured using a
piezometer. Internal piezo-metric pressures are most relevant to embankment dams as well as
their foundations and abutments. The measurement of internal water pressure at a number of
points in the body of the embankment dam, or in its abutments or foundation, allows the
phreatic surface (below which the materials are saturated) to be understood. Saturation of the
downstream shoulder of an embankment dam is undesirable for dam stability.

Also uplift pressure at or near the toe of embankment dams may also be relevant if a blowout
condition or potential piping condition exists.

Uplift pressures are also most relevant to concrete/masonry dams and their foundations, and
allow their stability to be evaluated.

There are a number of piezometer types including Open Standpipes (Observation

wells),Ported/Slotted Standpipes,Hydraulic, Pneumatic, Vibrating wire and Fiber Optic
piezometers. Piezometers are typically installed during the construction of a dam in its body
or foundation. This makes the replacement of certain types of piezometers difficult and
potentially risky process. Therefore the maintenance of installed piezometers to preserve their
accuracy and maximize their service lives, is very important and usually requires the input of
an appropriately skilled and competent Technical Adviser (specifically a geotechnical
Instrumentation specialist). Where such embedded piezometers malfunction, backup
piezometers that are long lasting should be considered. For retrofitting or replacement of
piezometers (e.g. for replacing failed instruments, characterization of a special feature or the
monitoring of a potential failure mode), extreme care should be taken in planning and
installing the instruments to avoid damage to the dam and its foundation. An appropriately
experienced Technical Adviser or Technical Specialist should be consulted in such cases. In
some cases the dam safety risks associated with installing a new piezometer may outweigh
the benefits of the instrument.

Foundation drainage holes in concrete dams can be used for installing piezometers, either by
measuring the depth to the water level (if the water level is below the top of the drain) or by
installing a pressure gauge over the steel pipe at the top of foundation drainage holes (if water
is flowing from the drain). An appropriately experienced Technical Adviser or Technical
Specialist should be consulted in such cases. For correct evaluations of dam performance it is
important that the locations of piezometers in the body of a dam or foundation are accurately
known (position and level), that the instruments are correctly identified, that their precision
and accuracy are regularly assessed, and that they are appropriately maintained.

4.1.4 Deformation and Displacement

Deformation and displacement in dams can be effective performance indicators forinstability,

settlement, loss in freeboard and a number of other potential failure modes. They are also
useful to characterize the behavior of dam and foundation components. They are most
commonly observed by visual observation during routine surveillance, and measured by
traditional survey methods such as precise levelling and Electronic Distance Measurement
(EDM) of targets installed at key locations on the dam and its foundation. Visual
observations can generally only identify large or obvious deformations or movements in a
structure or abutment. Instrumented measurement and surveying are the most effective
methods for measuring and monitoring changes at specific locations and features, and
establishing movement trends or verifying visual inferences of movement. A Designer with
experience in the particular dam type should be consulted when designing a dam deformation
survey layout to ensure that the dam’s performance monitoring objectives are met. In addition
to traditional survey methods, there are a number of alternative methods and technologies
 available for the measurement of deformations and displacements. Examples include
pendulums, inclinometers, tilt meters, joint meters, Global Navigation Satellite Systems
(GNSS), continuous survey monitoring (CSM), robotic total station and laser scanning
(ground mounted or airborne).
Fundamentally, the method and/or technology adopted should be selected such that it meets
the dam performance monitoring objectives related to precision and accuracy, and can be
readily calibrated.

For accuracy in measurements deformation surveys should be conducted by specialist

surveyors with equipment and methodologies that achieve the required precision and
accuracy (within 1 to 2 mm vertically and 3 to 4 mm horizontally). A survey control network
on stable ground remote from the dam structure should be utilized to minimize survey errors
and a specialist surveyor should be consulted in designing the control network. Generally, the
size of the structure and its survey control network will influence the achievable precision
and accuracy of the deformation survey. To be reproducible and to detect changes, periodic
surveys should generally be taken at the same time of year(especially
importantforconcretearchdams). Also, when surveying methods or survey personnel change,
a close examination of the results should be carried out to establish the validity of the results
and their correlation with past surveys.

Vegetation management plays a significant part in the effectiveness of deformation

monitoring. For visual observation, clear dam and abutment faces allow the identification of
surface anomalies. For instrumented surveys, vegetation and man-made additions (e.g.
handrails or fences) may block lines of sight between survey pillars and monitoring points.

4.1.5 Other Instruments and Systems

There are a vast range of other instruments and systems also available which are used for the
monitoring of dam performance and the monitoring of hazards. Some common examples
include, but are not limited to:
a) The use of cement plaster across cracks in concrete dams on the crest or within galleries to
monitor relative movements. Two or three dimensional crack monitoring devices can also be
attached to the dam for greater accuracy. An easy crack monitor is to have inspectors at the
site mark the end of a crack with a perpendicular line and date. This provides a visual log of
the crack progression with time.
b) Dye tests for determining seepage and leakage origins/paths.
c) Turbidity meters (indicators of internal erosion).
d) Video cameras for real-time visual observations, including the internal inspection of conduits
(drains and outlet tunnels) both above and under water.
e) Thermometers for recording temperature and temperature gradients in concrete dams (for
thermal studies).
f) Trip wire systems (e.g. displacement/rupture of an active fault, or a dam itself).
g) Post-tensioned cable anchor load testing (to confirm anchor tensions).
h) Temperature sensing systems for the identification of seepage in dams or foundations (e.g.
distributed temperature sensing and resistance temperature devices). Temperature sensors can
provide valuable data on the flow time and flow source of seepage water, particularly when
complemented by other measured parameters such as piezometric pressure, seepage flow
 rate, and the temperature of the reservoir and other potential sources (such as ambient
groundwater or tail water).
i) Early warning upstream rainfall collection and catchment modelling systems for predicting
the size of incoming floods or extreme weather conditions (an important aspect for
surveillance and emergency preparedness).
j) Rainfall measurement to assist with the interpretation of seepage observations, and the
evaluation or correlation of landslide and abutment slope movements.
k) A seismic monitoring network for detecting and notifying the location and strength of
earthquakes (an important aspect for emergency response). The India Meteorological
Department (IMD) Seismic network is available
i. Strong motion seismic sensors for the measurement of ground motions. These may be helpful
where the IMD network coverage is limited and/or where measurement of ground motions at
the dam site is required. The locations for installation of strong motion recorders should be
based on the site conditions and preferred locations. In order of usefulness the preferred
location are the base of the dam to record the peak ground acceleration, the abutments to
record topographic amplification of the peak ground acceleration and the dam crest to record
the amplification of the peak ground acceleration.
Instruments and systems as indicated above may be built into or near a dam at the time of its
construction or added during the life of a dam to supplement or enhance existing
instrumented monitoring, to address a specific potential failure mode, or to investigate a
potential or confirmed dam safety deficiency.
5 VARIOUS PARAMETERS MEASURED AND THE SUGGESTED FREQUENCY OF
MEASUREMENTS

Various parameters to be measured in dams & suggested frequency of readings for specified
instruments as prescribed in other guidelines viz. Instrumentation for dam & O&M for dam
are given at Tables 1 & 2 for reference. All instruments should be read immediately after
seismic activity or historic reservoir levels.

Many of the instruments in Tables should be read daily during initial filling or anytime the
reservoir goes above the historic maximum; weekly is too infrequent. First filling is a critical
timeframe for a dam. Also, the dam should have continual visual monitoring during initial
filling or any time the reservoir goes above the historic maximum. A Potential Failure Mode
workshop can help establish the need for certain instruments and the reading frequency. As a
minimum, instrument readings at a concrete dam should include reservoir levels, dam
deflections, seepage through the dam, and uplift pressures under the dam. It is suggested that
some instruments be read weekly for the first year and some monthly to develop a detailed
plot of data. Then the frequency of readings can be reduced as indicated in the Table.
Preferably, instruments should be read at the same time of the dam and the same day of the
month.

6 DAM PERFORMANCE EVALUATION

Experienced Engineers should be assigned the job of establishing performance expectations
and to evaluate dam performance appropriate to the consequences of failure and the
complexity of the dam being evaluated. In some situations, Technical Specialists may be
required (e.g. complex foundation and/or dam behavior, complex structural or geotechnical
analysis, high or extreme consequences of failure, or the management of a dam safety
deficiency).The evaluation of visual observations and instrumented data with respect to a
dam’s safe performance is an essential part of a dam safety programme.

Performance evaluation should be undertaken following the completion of each routine

surveillance inspection in a timeframe that reflects the dam condition and performance.
Besides during normal operations of dam, this exercise needs to be carried out after unusual
events like high flood or earthquake as also indicated in the Guidelines for Safety Inspection
of Dams & Guidelines for preparing O&M Manuals for Dams.

The completion of an effective evaluation requires an understanding of the dam’s behavior

under all loading conditions, and the use of evaluation techniques that can predict the
expected behavior of the dam, based on the available information of the dam (e.g. design,
construction, operation and maintenance records, rehabilitation records, and records of
unusual events and incidents) and then compare it with the actual surveillance records.
Importantly, the evaluation must consider the dam’s ‘performance as a whole’ in the context
of the dam setting, design philosophy, construction features, condition, historical
performance and potential failure modes. Judgments should not be made based solely on
isolated observations or instrument readings. Instead, the wider dam and foundation context
should be considered, with conclusions drawn and supported by bringing together a range of
relevant performance parameters and other information relevant to the safety of the dam.For
this purpose structural behavior reports need to be prepared based on the instrument data
collected. These reports can be examined by the designers.

While reviewing the safety of existing dams it is desirable to include the following aspects in
the structural behavior reports:
a) Comments on the actual structure behavior based on: an understanding of the dam’s
characteristic behavior – how the dam and its foundation should typically behave under
various loading conditions, comparison of the actual parameters measured with the
design assumptions/parameters.
b) The potential failure modes of the dam, key performance indicators and condition of the
dam. Potential failure modes are an extremely important concept for engineers, owners,
and maintenance personnel.
c) Established two alert thresholds (acceptable performance limits) for key performance
indicators coupled with action items. For instance, a reservoir level that starts a
preparedness level, beginning actions, and then possible evacuations. Other terms for this
is the Ready, Set, Go levels. Also, every Every concrete dam should have “safe” water
levels determined for the key reservoir levels that indicate the dam is within criteria,
starts developing tension at the heel, and starts overturning.
 Table -1: Parameters to be monitored at Dams Hydraulic Structure
(Clause 5)

Crack and joint

Uplift and pore
Structure Type

Water quality
Seepage flows

measurement

measurement

measurement

measurement
Temperature

Stress-strain
Water levels
observation
Movements
Feature

pressure

Seismic
Visual
Upstream slope ✓ ✓ ✓ ✓ ─ ─ ─ ─ ✓ ─
Downstream slope ✓ ✓ ✓ ─ ✓ ✓ ✓ ✓ ✓ ─
Embankment Dams

Abutments ✓ ✓ ✓ ─ ✓ ✓ ✓ ─ ✓ ─
Crest (Dam Top) ✓ ✓ ✓ ─ ─ ─ ─ ✓ ✓ ─
Internal drainage ✓ ✓ ✓
─ ─ ─ ✓ ─ ─ ─
system
D/s Toe Drains ✓ ✓ ✓
✓ ─ ─ ─ ─ ─ ─
Relief Drain
U/s Riprap and D/s ✓
─ ─ ─ ─ ─ ─ ─ ─ ─
slope protection
Upstream slope ✓ ✓ ─ ✓ ─ ─ ✓ ✓ ✓ ✓
Concrete and Masonry Dams

Downstream slope ✓ ✓ ✓ ─ ─ ─ ✓ ✓ ✓ ✓
Abutments ✓ ✓ ✓ ─ ✓ ✓ ─ ─ ✓ ✓
Crest (Dam Top) ✓ ✓ ✓ ─ ─ ─ ✓ ✓ ✓ ✓
Internal drainage ✓ ✓
system in Dam ─ ─ ─ ─ ─ ✓ ─ ─
Body
Foundation drains ✓ ─ ✓ ─ ✓ ─ ─ ─ ─ ─
Galleries ✓ ✓ ─ ─ ─ ─ ─ ✓ ✓ ✓
Sluices / controls ✓ ─ ─ ✓ ─ ─ ─ ─ ─ ─
Approach channel ✓ ✓ ─ ✓ ─ ─ ─ ─ ─ ─
Control structure ✓ ✓ ✓ ✓ ✓ ─ ─ ✓ ✓ ─
Stilling basin / any ✓ ✓
─ ─ ─ ─ ─ ✓ ─ ─
other EDA
Spillways

Discharge ✓ ✓
─ ✓ ─ ─ ─ ─ ─ ─
conduit/channel
Gate controls ✓ ─ ─ ─ ─ ─ ─ ─ ─ ─
Erosion protection ✓
─ ─ ─ ─ ─ ─ ─ ─ ─
on d/s of EDA
Side slopes ✓ ✓ ✓ ─ ✓ ─ ─ ─ ─ ─
Control Structure ✓ ✓ ✓ ✓ ─ ─ ─ ✓ ✓ ─
Outlets

Stilling basin / any ✓ ─ ─ ─ ─ ─ ─ ─ ─ ─

other EDA
 Crack and joint
Uplift and pore
Structure Type

Water quality
Seepage flows

measurement

measurement

measurement

measurement
Temperature

Stress-strain
Water levels
observation
Movements
Feature

pressure

Seismic
Visual
Discharge ✓ ✓ ✓ ✓
─ ─ ─ ✓ ─ ─
conduit/channel
Trash rack/debris ✓
─ ─ ─ ─ ─ ─ ─ ─ ─
controls
Reservoir surface ✓ ─ ─ ─ ─ ✓ ─ ─ ─ ─
Mechanical/ ✓
─ ─ ✓ ─ ─ ─ ─ ─
electrical systems
General Areas

Reservoir Periphery ✓ ─ ─ ─ ─ ✓ ─ ─ ─ ─
Upstream watershed ✓ ─ ─ ─ ─ ✓ ─ ─ ─ ─
Downstream ✓ ✓
─ ─ ─ ✓ ─ ─ ─ ─
channel
Emergency ✓ ─
─ ─ ─ ─ ─ ─ ─ ─
Warning System

Table 2: Suggested frequency of readings for specified instruments

 ( Clause 5)
During Period of
During Construction During Operation
Type of instrument initial
Construction Shutdow Yea Years Regula
filling
n r1 2 to 3 r
Vibrating wire W M D BiW M M
piezometers
Hydrostatic uplift W M D W BiW M
pressure pipes
Porous-tube M M D W M M
piezometers
Slotted-pipe M M D W M M
piezometers
Observation wells W M D W BiW M
Seepage W M D W M M
measurement (weirs
and flumes)
Visual seepage W W D W F M
monitoring
Resistance W M W W M M
thermometers
Thermocouples D M W W M M
Carlson strain W W W BiW M M
meters
Joint meters W W W BiW M M
Stress meters W M W BiW M M
Reinforcement W M M M M M
meters
Penstock meters W M M M M M
Deflectometers W M W W M M
Vibrating wire W M M M M M
strain gauge
Vibrating-wire total W M M M M M
pressure cell
Load cell W M W BiW M M
Pore pressure W W D W M M
meters
Foundation W W W BiW M M
deformation
 During Period of
During Construction During Operation
Type of instrument initial
Construction Shutdow Yea Years Regula
filling
n r1 2 to 3 r
meters
Flat jacks D W W BiW M M
Tape gauges W W W/BiW BiW M M
(tunnel)
Whitmore gauges, W M W W M M
Avongardcrack
meter
Wire gauges W M W/M W/M M M/Q
Abutment W M W W M M
deformation
gauges
Ames dialmeters, W M W W M M
differential
buttress gauges
Plumblines D W D W BiW M
Inclinometer W W W W BiW M
Collimation Every two M W BiW M M
days for a
month
Embankment --c -- M BiM Q SA
settlement points
Level points M Q M M/Y BM/Q BM
Multipoint W M W M M Q/SA
extensometers
Triangulation M M Q SA
Trilateration (EDM) -- -- BiW/M M Q Q/A
Reservoir slide -- -- M M M Q
monitoring
systems
Power plant -- -- M/W M M M/Q
movement
Rock movement W M W M M M
NOTE 1 -- These are suggested minimums. However, anomalies observed or unusual occurrences, such as
earthquakes or floods, will require additional readings.

NOTE 2 -- D = daily, W = weekly, BiW = bi-weekly, M = monthly, Q = quarterly, SA = semi-annually, A =

annually.

NOTE 3 -- Shutdown is that period during construction when the works remained suspended / stopped, due to any
reason.