Niagara
Power Project FERC No. 2216
NIAGARA
RIVER WATER LEVEL AND FLOW FLUCTUATIONS STUDY FINAL REPORT
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Prepared for: New York Power
Authority
Prepared by: URS Corporation;
Gomez and Sullivan Enigeers, P.C.; and E/PRO
Engineering & Environmental Consulting, LLC
August 2005
___________________________________________________
Copyright © 2005
New York Power Authority
ABBREVIATIONS
Agencies
CHS Canadian
Hydrographic Service
EC Environment Canada
FERC Federal
Energy Regulatory Commission
IJC International
Joint Commission
INBC International
Niagara Board of Control
NOAA National
Oceanic and Atmospheric Administration
NRCC Niagara River Control Center
NYISO New York Independent
System Operator
USACE United
States Army Corps of Engineers
USGS United
States Geological Survey
Units of Measure
cfs cubic feet per second
E.S.T. Eastern
Standard Time
E.D.S.T. Eastern
Daylight Savings Time
El. elevation
fps feet
per second
IGLD 1985 International
Great Lakes Datum 1985
mph miles
per hour
MW megawatt, or one million watts
NGVD National
Geodetic Vertical Datum
USLSD U.S. Lake
Survey Datum 1935
Miscellaneous
ADCP Acoustic
Doppler Current Profiler
LPGP Lewiston Pump Generating
Plant
NYPA New York Power Authority
OPG Ontario Power Generation
EXECUTIVE SUMMARY
In preparation for relicensing of the Niagara Power Project (the Project) an
engineering analysis was performed for the New York Power Authority (NYPA) to determine:
1) the magnitude, frequency and spatial extent of water level and flow
fluctuations in the Niagara River and 2) the magnitude and frequency of water
level fluctuations in Lewiston Reservoir associated with power generation at
the Project.
It was known at the
investigation’s outset that water level fluctuations in both the upper and
lower Niagara River (i.e., the portions of the river above Niagara Falls and below it, respectively) are
caused by a number of factors. Natural
factors include flow surges from Lake Erie, wind, ice conditions, and regional
and long-term precipitation patterns that affect lake levels, while manmade
factors include regulation of Niagara
Falls flows for scenic purposes, operation of power
plants on the Canadian side of the river, and operation of the Niagara Power
Project. The influence of these factors
on water levels is interrelated and dynamic.
Because the water level in the Niagara River
at any location at any time is a complex function of natural and manmade factors,
distinguishing the exact amount of water level fluctuation attributable to each
factor is difficult. Therefore, for many
of the analyses, the reported water level fluctuations in the Niagara
River include the influences from all the factors. One exception was the effects of storm and
wind induced water level fluctuations that were differentiated through a
combination of gauge data analysis and empirical calculation of surface wave
height and wind setup.
The Niagara River Water
Diversion Treaty of 1950 specifies that flow over Niagara Falls be at least 100,000 cfs during tourist-season (April 1 to October 31) daylight
hours and at least 50,000 cfs at all other
times. The purpose of regulation of
water levels in the Chippawa-Grass Island Pool is to
ensure the availability of sufficient flows to satisfy these treaty
requirements while providing for power production and maintenance of water
levels in the pool within the specifications of a 1993 Directive of the
International Niagara Board of Control.
The Directive requires
that the International Niagara Control Structure be operated to ensure an
operational long-term average pool level of El. 562.75 feet (IGLD 1985 El.
561.55 feet) (Figure EX-1).
It also establishes certain tolerances for the pool’s water level as
measured at the Material Dock gauge, permitting up to 1.5 feet fluctuation
between daily maximum and minimum water levels.
This daily allowable fluctuation must occur within a normal 3-foot range
between El. 561.24 and El. 564.22 feet (IGLD 1985 El. 560.04 to 563.02
feet). Under extreme conditions (e.g.,
high flow, low flow, ice), the allowable range of Chippawa-Grass
Island Pool water level fluctuation is extended to 4 feet between El. 560.75
and El. 564.75 (IGLD 1985 El. 559.55 to 563.55 feet).
The analysis was done
using hourly water level and flow data from 15 permanent water level gauges and
3 flow gauges in the upper and lower Niagara River during the years 1991
through 2002, hourly water level data from four temporary gauges in the lower
Niagara River below the Project discharge during 2001 and 2002, and six
temporary gauges in the Buckhorn Marsh area of Grand Island during 2002.
Data were analyzed in
various ways to produce a picture of daily fluctuation in the upper and lower
Niagara River and to establish the upstream extent of such fluctuation in the
upper Niagara River. These analyses included graphing of hourly
water levels and river-water elevation profiles (plots of water elevation
versus river mile), analysis of the timing of maximum and minimum water levels,
duration-distribution analyses of hourly water level and daily fluctuations,
extreme-events analysis, and wind analysis.
In the upper Niagara River, it was found that regulation of the Chippawa-Grass Island Pool water levels by means of the
International Control Structure and Power Entity water withdrawals has a more
pronounced effect during the tourist season rather than the non-tourist
season. The reason for this is that
during non-tourist hours, the pool is maintained at a lower water level so that
the scenic Falls flow remains close to 50,000 cfs. To compensate for water levels lower than the
long-term mean specified by the 1993 Directive, the pool elevation is higher
during tourist hours. On a typical day
during the tourist season, the water level in the upper Niagara River from the
northern tip of Grand Island downstream (the Chippawa-Grass
Island Pool) is at its maximum at 7 a.m. E.S.T.
The water level in the pool is drawn down over the course of the day as
water is diverted through the intakes for power generation. It is generally at its lowest level by 9 p.m.
E.S.T. At night, when the flow over Niagara Falls and power
generation are reduced, water is ponded in the pool.
The effect of ponding in the Chippawa-Grass
Island Pool is detectable upstream and varies with river conditions. If there is a flow surge traveling down the
river, the influence does not extend far upstream. On the other hand, for calm conditions on
Lake Erie, this influence can extend to somewhere between the Frenchman’s Creek
and the Peace Bridge gauges. Impact of water level regulation at the Chippawa-Grass Island Pool on Fort Erie water levels
(immediately upstream of the Peace
Bridge) is virtually
undetectable. Water level fluctuations
at Fort Erie appear to be wholly caused by
prevailing weather conditions, particularly wind speed and direction.
Figure
EX-2 compares the difference in daily median water level fluctuations for
the tourist and non-tourist seasons at various gauges in the upper Niagara River. The
amount of daily median water level fluctuation from all causes is highest at
the gauges in the Chippawa-Grass Island Pool (NYPA
Intake, Material Dock, LaSalle, and Slater’s Point). The amount of daily fluctuation decreases as
one proceeds upstream as the influence of regulation of water in the Chippawa-Grass Island Pool lessens. The amount of median daily water level
fluctuation is lowest at Huntley, Frenchman’s Creek, and Peace Bridge
gauges. The amount of daily fluctuation
then increases as one travels upstream towards Lake Erie
as the influence of storm surges from the lake increases.
In the lower Niagara
River downstream of Niagara Falls but upstream of the Project tailrace, the
daily median water level change during the tourist season at the Ashland Avenue
gauge (in the Maid of the Mist Pool immediately downstream of the Falls) is
approximately 11 feet, based on data collected from 1991-2002. This is due to the treaty-mandated control of
flow over Niagara Falls
for reasons of tourism, with more water (100,000 cfs)
being released during tourist season daytime and less (50,000 cfs) being released at all other times. Water level fluctuations downstream of the
Niagara Power Project are much less. The
average daily water level fluctuation during the 2002 tourist season 1.4 miles
downstream of the Robert Moses tailrace is approximately 1.5 feet. The daily fluctuations decrease in a
downstream direction. Near the mouth of
the lower Niagara River in Lake
Ontario, the average
daily fluctuation during the tourist season was 0.6 feet.
Water level fluctuation
in the Lewiston Reservoir, which ranges between 3 – 18 feet per day and as much
as 36 feet per week during tourist season, is due to Niagara Power Project
operations (the reservoir is drawn down gradually over the course of a week and
refilled on the weekend) and Niagara River
flow. Weekly drawdowns
are typically greater during the tourist season (21-36 feet) than the non-tourist
season (11-30 feet). Weekly drawdowns are also greater during low-flow periods than
high-flow periods, as more water is rescheduled to generate electricity during
peak demand periods.
Figure EX-1
Regulation
of the Chippawa-Grass Island Pool Water Levels as Specified by the INBC 1993
Directive
Figure EX-2
Comparison
of Daily Median Water Level Fluctuations for the Period 1991-2002
1.0 INTRODUCTION
The New York Power
Authority (NYPA) is engaged in the relicensing of the
Niagara Power Project in Lewiston, Niagara County, New
York. The
present operating license of the plant expires in August 2007. In preparation for the relicensing
of the Niagara Power Project, NYPA is assembling information related to the
ecological, engineering, recreational, cultural, and socioeconomic aspects of
the Project. As part of this effort,
Gomez and Sullivan conducted an engineering analysis of surface water and flow
fluctuations in the Niagara River. The investigation area for this work includes
the Niagara River from its head at Lake Erie to its mouth at Lake Ontario
and Lewiston Reservoir.
All elevations in this
report are referenced to U.S. Lake Survey Datum 1935 (USLSD). Values for other pertinent datums are listed in parentheses.
The 1,880-MW (firm
power output) Niagara Power Project is one of the largest non-federal
hydroelectric facilities in North America. The Project was licensed to the Power
Authority of the State of New York
(now the New York Power Authority) in 1957.
Construction of the Project began in 1958, and electricity was first
produced in 1961.
The Project has several
components, shown in Figure 1.1-1. Twin intakes are located approximately 2.6
miles above Niagara Falls. Water entering these intakes is routed around
the Falls via two large underground conduits to a forebay,
lying on an east-west axis about 4 miles downstream of the Falls. The forebay is located on the east bank of the Niagara River. At
the west end of the forebay, between the forebay itself and the river, is the Robert Moses Niagara
Power Plant, NYPA’s main generating plant at Niagara. This
plant has 13 turbines that generate electricity from water stored in the forebay. Head is
approximately 300 feet. At the east end
of the forebay is the Lewiston Pump Generating
Plant. Under non-peak-usage conditions
(i.e., at night and on weekends), water is pumped from the forebay
via the plant’s 12 pumps/generators into the Lewiston Reservoir, which lies
east of the plant. During peak usage
conditions (i.e., daytime Monday through Friday), the pumps are reversed for
use as generators, and water is allowed to flow back through the plant,
producing electricity. The forebay, therefore, serves as headwater for the Robert
Moses plant and tailwater for the Lewiston
Plant. South of the forebay
is a switchyard, which serves as the electrical interface between the Project
and the interface between the Project and the interstate transmission grid
operated by the New York Independent System Operator.
There are two
regulatory constraints on flow and water level fluctuations - the Niagara River
Water Diversion Treaty of 1950 and the 1993 Directive of the International
Niagara Board of Control (INBC). For
purposes of generating electricity from the Niagara River,
two seasons are recognized: tourist
season and non-tourist season. The
tourist season (April – October) coincides with the months in which tourist
hours are in effect. By international
treaty, at least 100,000 cfs must be allowed to flow
over Niagara Falls during tourist hours (April 1 - September 15, 8:00 a.m. –
10:00 p.m. E.D.S.T. and September 16 – October 31, 8:00 a.m. – 8:00 p.m.), and
at least 50,000 cfs at all other times. Canada
and the United States
are entitled by treaty to produce hydroelectric power with the remainder.
Pursuant to the
requirements of the 1993 Directive of the INBC, water level fluctuations in the
Chippawa-Grass Island Pool (in the upper Niagara
River, i.e., above Niagara Falls) are limited
to 1.5 feet per day. The daily
fluctuation is allowed within a 3-foot range for normal conditions (Figure 1.1-2). For extreme conditions (i.e., high flow, low
flow, ice, etc.), the allowable range of Chippawa-Grass
Island Pool water levels is extended to 4 feet and the 1.5 foot daily
fluctuation tolerance can be waived.
Water level
fluctuations in both the upper and lower Niagara River
are caused by a number of factors other than operation of the Niagara Power Project. These include wind, natural flow and ice
conditions, regional and long-term precipitation patterns that affect lake
levels, control of Niagara Falls flow for scenic
purposes, operation of power plants on the Canadian side of the river, and the
backwater effect
from Lake Ontario.
Water level fluctuations in the upper Niagara River
from all causes are normally less than 1.5 feet per day.
Daily water level
fluctuations in the lower Niagara River from all causes are typically around
10-12 feet per day during tourist season at the Ashland Avenue gauge, downstream of Niagara Falls. Fluctuations decrease to the 1.2-2.0 foot
range at temporary gauge SG-01A (in place during 2002), 1.4 miles downstream of
the tailrace.
Operation of the
Niagara Power Project can result in water level fluctuations in the Lewiston
Reservoir that range between 3 to 18 feet per day, and approximately 11-36 feet
per week depending on the season and river flows. Weekly drawdowns
are typically greater (21-36 feet per week) during the tourist season. Storage in the Lewiston Reservoir is used to
generate power to meet daily peak energy demands.
This investigation had
two objectives: 1) to determine the magnitude, frequency, and spatial extent of
water level and flow fluctuations in the Niagara River
associated with power generation at the Project and Canadian hydroelectric
projects and 2) to determine the magnitude and frequency of water level
fluctuations in Lewiston Reservoir associated with power generation at the
Project.
To determine the effect
of power operations on water level and flow, natural conditions such as the
changing levels of Lakes Erie and Ontario,
variable flows from Lake Erie, and the effects
of wind and ice must be considered.
1.3
Physical
Description
The Niagara River,
which flows from Lake Erie to Lake Ontario, forms a portion of the boundary between the
State of New York and the Province of Ontario. The river drains four of the five Great Lakes, a drainage area of approximately 263,700
square miles. The difference in surface
elevations between the two lakes is about 326 feet, half of this occurring at Niagara Falls.
The Niagara River, as
described in the following paragraphs, consists of two major reaches: the upper
Niagara River and the lower Niagara River. A plan view of the river showing water level
gauges and natural features is shown in Figure
1.3-1. The two reaches are separated by the
Cascades Rapids, just above Niagara
Falls, and the Falls itself.
The upper Niagara River
extends about 22 miles from Lake Erie to the Cascades Rapids, which begin 0.6
miles upstream of the Horseshoe Falls. From Lake Erie to Strawberry
Island, a distance of approximately 5
miles, the channel width is greatest at the river’s head (9,000 feet) and least
at Squaw Island,
just downstream of the Peace
Bridge (1,500 feet). Between Squaw and Strawberry Islands,
the river width is approximately 2,000 feet.
At Grand
Island, just downstream of Strawberry Island,
the river divides into the west channel, known as the Canadian or Chippawa Channel, and the east channel, known as the
American or Tonawanda Channel. The Chippawa Channel, approximately 11 miles long, varies in
width from 2,000 to 4,000 feet. The Chippawa Channel carries approximately 58% of total river
flow. The 15-mile-long Tonawanda
Channel, upstream of Tonawanda
Island, varies in width
from 1,500 to 2,000 feet. Downstream of
this island it varies in width from 1,500 to 4,000 feet. At the downstream end of Grand Island (i.e., the north end), the
channels unite to form the 3-mile-long Chippawa-Grass
Island Pool, at the lower end of which is the International Niagara Control
Structure. This linear structure, with 18
sluice gates for control of flow over Niagara
Falls, extends perpendicularly from the Canadian
shoreline to the approximate midpoint of the river. The Falls is located about 4,500 feet
downstream of the International Niagara Control Structure.
The water level in the Chippawa-Grass Island Pool is regulated in accordance with
a 1993 Directive of INBC. The Directive
requires that, to ameliorate high or low water levels in the pool, Ontario
Power Generation (OPG) and NYPA operate the International Niagara Control
Structure to ensure the maintenance of an operational long-term average pool
elevation of El. 562.75 (IGLD 1985 561.55).
The fall from Lake Erie to the Chippawa-Grass Island Pool is approximately 9 feet. Below the International Niagara Control Structure,
the river falls 50 feet through the Cascade Rapids before being divided into
two channels by Goat Island. These channels convey the flow to the brink
of the Canadian Falls on one side and the American Falls
on the other. At this point the river
drops approximately 167 feet, on the American side falling on a sizable volume
of talus, or rock debris, that has accumulated at the foot of the
precipice. (The Canadian Falls, because
of its horseshoe-shaped crest, is also known as the Horseshoe
Falls.) The treaty-mandated
minimum flow over the American and Horseshoe Falls
combined during tourist hours from April 1 through October 31 is 100,000 cfs. During
non-tourist hours, the minimum treaty-mandated flow is 50,000 cfs.
Below Niagara Falls
(i.e., in the lower Niagara River), the river runs through the narrow Niagara
Gorge seven miles from the Falls to the foot of the Niagara escarpment at
Lewiston, New York. The upper portion of
this reach, which is navigable, extends from the base of the Falls to the
Whirlpool Rapids, which are not navigable.
The fall through this upper reach, known as the Maid of the Mist Pool,
is approximately 5 feet. In the
Whirlpool Rapids, the water surface elevation drops approximately 50 feet over
the course of a mile. At the Whirlpool—a
1,700-foot long, 1,200-foot wide, 125-foot deep basin downstream of the
rapids—the river bends nearly 90 degrees to the right. Below this point the river drops another 40
feet through the Devil’s Hole Rapids. It
emerges from the gorge at Lewiston, New York, subsequently dropping another 5 feet to Lake Ontario,
and widening to 2,000 feet. The lower
Niagara River is navigable from Lewiston to its
mouth at Lake Ontario.
Figure 1.1-1
Niagara Power Project
Features
[NIP – General Location Maps]
Figure
1.1-2
Regulation
of Chippawa-Grass Island Pool Water Levels as Specified by the INBC
1993 Directive
Note:
Elevation Datum: USLSD 1935. To convert
water levels in the upper Niagara River from
USLSD 1935 to IGLD 1985 subtract 1.2 feet
Abnormal flow conditions are considered to
exist when any four consecutive hourly mean Niagara River flows, as determined
from levels at the Fort Erie gauge, are
greater than 270,000 cfs or less than 150,000 cfs.
Text of the 1993 Directive is
located in Appendix G.
Figure 1.3-1
Niagara River Plan and Profile
[NIP – General Location
Maps]
Figure 1.3-2
Niagara River Cross-Sections
[NIP – General Location
Maps]
Figure 1.3-3
Sources
of Bathymetric Data
[NIP – General Location
Maps]
2.0
FACTORS
AFFECTING WATER LEVEL FLUCTUATION
The water level in the Niagara River at any location at any time is a complex
function of manmade and natural factors.
Water levels in the Niagara River are a function of treaty-stipulated
flows, regulation of the Chippawa-Grass Island Pool,
power generation flows, water level of Lake Erie, outflow of Lake Erie, water
level of Lake Ontario, wind, and ice.
2.1
Niagara River Water
Diversion Treaty of 1950
In 1950, the United States and Canada
signed the Niagara River Water Diversion Treaty, the purpose of which was to
increase the amount of water available for power generation while still
preserving the scenic beauty of Niagara
Falls (Treaty Between Canada and the United States of
America Concerning the Diversion of the Niagara River, Oct. 10 1950, 1 U.S.T.
694). Article IV of the treaty states:
In order to reserve
sufficient amounts of water in the Niagara River for scenic purposes, no
diversions of the water . . . shall be made for power purposes which will
reduce the flow over Niagara Falls to less than one hundred thousand cubic feet
per second each day between the hours of eight a.m. E.S.T., and ten p.m.
E.S.T., during the period of each year beginning April 1 and ending September
15, both dates inclusive, or to less than one hundred thousand cubic feet per
second each day between the hours of eight a.m. E.S.T., and eight p.m. E.S.T.,
during the period of each year beginning September 16
and ending October 31, both dates inclusive, or to less than fifty thousand
cubic feet per second at any other time; the minimum rate of fifty thousand
cubic feet per second to be increased when additional water is required for
flushing ice above the Falls or through the rapids below the Falls.
By exchange of
diplomatic notes in 1973, E.S.T. was changed to E.D.S.T. in the 1950 Treaty.
The operation of the
International Niagara Control Structure ensures sufficient flow over the Falls
to meet the requirements of the Niagara River Water Diversion Treaty of
1950.
Changes in Falls flows
between 50,000 and 100,000 cfs contribute to
fluctuating water levels in the lower Niagara River
directly downstream of the Falls as well as downstream of the Robert Moses and
Sir Adam Beck tailraces. (See Figure 2.1-1 for gauge
locations in the lower Niagara River.) At the Ashland Avenue gauge, due to changes
in the Falls scenic flow, water levels fluctuate 10-12 feet daily (Figure 2.1-2). Figure 2.1-2 shows water
levels for the period March 18 through April 14, 2001. The March dates occur during the non-tourist
season, when Falls flow is a constant 50,000 cfs, and
the April dates occur during tourist season, when Falls flow is 100,000 cfs during the day and 50,000 cfs
at night.
The water level in the Chippawa-Grass Island Pool is regulated in accordance with INBC’s 1993 Directive.
This Directive requires that, in order to ameliorate high or low water
levels in the pool, the International Niagara Control Structure be operated so
as to ensure the maintenance of an operational long-term average pool level of
El. 562.75 (El. 561.55 IGLD 1985) (Figure 1.1-2). Water level fluctuations in the Chippawa-Grass Island Pool (in the upper Niagara River)
caused by operation of the Canadian and NYPA hydroelectric plants are limited
to 1.5 feet per day within a 3-foot normal range. The normal range for water levels is El.
561.24 (IGLD 1985 El. 560.04) to El. 564.22 (IGLD 1985 El. 563.02). The Directive also establishes adverse low
pool levels as El. 560.75 (IGLD 1985 El. 559.55) and high levels as El. 564.75
(IGLD 1985 El. 563.55) in the pool.
Regulations for water levels in the Chippawa-Grass
Island Pool within the normal 3-foot range may be suspended for unusual
conditions such as low flows, high flows, ice management (e.g., maximum level
may exceed normal high level of El. 564.22 temporarily to assist in flushing
ice over the Falls), or during emergency operations, flooding, and flow
measurements. In practice, during any
suspension of normal water level regulations, operators at the International
Niagara Control Structure notify the local INBC representatives of such a
suspension. Normal operating rules are
to be resumed within 12 hours following the last abnormal flow period or event.
OPG personnel operate
the International Niagara Control Structure, which ensures a dependable and
ample flow of water over both the American and Horseshoe
Falls and regulates the water level in the Chippawa-Grass
Island Pool for power diversions.
NYPA operates the
Niagara Power Project for the benefit of the state of New
York by retiming its entitlement of Niagara
River flow in order to generate more energy during periods of peak
demand, through judicious use of storage in the Lewiston Reservoir (see Section 2.5).
It is important to note
that NYPA’s water intakes on the upper Niagara have no control mechanisms for the diversion of
water from the Chippawa-Grass Island Pool into the
twin conduits that carry water to the Project forebay. The volume of water diverted through the
conduits by NYPA is a direct function of the difference in elevation between
the pool and forebay.
The forebay water level is controlled by NYPA
due to pumping and generation at the Lewiston Pump Generating Plant and
generation at the Robert Moses Niagara Power Plant. When Chippawa-Grass
Island Pool levels are normal, the conduit diversion capacity is 102,000 cfs. When Chippawa-Grass Island Pool levels are abnormally high, the
conduit capacity is 110,000 cfs.
If the flow that NYPA
draws from the river is sufficient to generate the exact amount of power
required using the Robert Moses units, the water system is in balance, and
Lewiston Reservoir water is not utilized.
If additional power output is required, however, as is usually the case
during the daytime peak period, it is furnished by additional generation from
reservoir water that flows first through the Lewiston Pump Generating Plant,
becoming available afterwards for flow through the Robert Moses Niagara Power
Plant. Conversely, if the conduit flow
exceeds the flow required to produce the power demanded of the Project, as is
usually the case at night or on weekends, part of the excess water is pumped
into the reservoir for future use and part is sent through the Robert Moses
Niagara Power Plant to generate the required energy for pumping. The change in flows available for power
generation between peak and non-peak demand periods contributes to fluctuations
in flow and water level in the lower Niagara River. In the lower Niagara
River downstream of the Robert Moses tailrace, daily water level
fluctuations are typically no more than 2 feet during the tourist season. Figure 2.3.1-1 shows water level
fluctuations for the randomly selected week of July 15-21, 2002, when flow from
the Robert Moses tailrace ranged between 30,560 and 97,630 cfs. Total flow in the Niagara
River downstream of the Robert Moses and Sir Adam Beck tailraces for
the week of July 15-21, 2002 varied between 133,025 and 255,794 cfs.
The design of the plant
makes possible a weekly cycle of response to demand for electricity. On weekdays, when demand for power is
highest, both the Robert Moses and Lewiston Pump Generating Plants are used for
power generation. At night and on
weekends, when demand is lower, only the Robert Moses Niagara Power Plant is
used for generation, and excess water is pumped into the reservoir to be stored
for use during the week.
The Lewiston Pump
Generating Plant and Reservoir allow NYPA to maximize the value of production
from the United States’
entitlement flows. As previously
mentioned, during the tourist season, the treaty allows more water to be
diverted from the river for power production at night. Nighttime, however, is a period of relatively
low electrical demand. So as not to lose
the benefit of water not required for immediate power production, the Lewiston
Reservoir is used to store water at night (and on weekends) for use as “fuel”
during high-demand periods. At night and
on weekends, therefore, the units at the Lewiston Pump Generating Plant are
used as pumps, to transport water from the