Acre-foot – The volume of water that will cover a one-acre [43, 560 square feet] area to a depth of one foot; one acre-foot equals 1233 cubic meters (325,000 gallons) of water.
Active Storage – That portion of the live storage capacity in which water will normally be stored or withdrawn for beneficial purposes, in compliance with operating agreements or restrictions.
Annexes A and B – Appendices to the Columbia River Treaty. Annex A deals with the principles of operation and Annex B with the determination of downstream power benefits. Annexes A and B are an integral part of the Treaty. (Treaty Article I)
Annual Firm Energy Capability – Annual FELCC: the firm energy load that the Pacific Northwest coordinated system is able to supply in a year from the firm resources of the coordinated system after deducting the required energy reserve and forced outage reserve.
Assured Annual Flood Control – Under the CRT Canada agrees to provide assured annual water storage for flood control purposes at the three CRT reservoirs for 60 years. The annual Assured Annual Flood Control provision expires automatically in 2024.
Assured Operating Plan – One of the two reservoir system operating plans prepared each year to implement the Columbia River Treaty. The Assured Operating Plan is prepared six years in advance of the actual year of operation and defines the rule curves and other operating parameters to guide the operation of the system in a manner that realizes the benefits anticipated by the Treaty. This series of annual operating plans assures both Entities of the manner of operation of Canadian storage in advance for the next five years. The AOP establishes the generation potential of both systems, prescribes operating criteria and procedures to ensure that the potential will be realized, and serves as the basis for the Detailed Operating Plan in the actual year of operation. The downstream power benefits studies are conducted in conjunction with the AOP. (Treaty Article XIV-2h and Annex A Paragraph 9, Protocol VII)
Assured Refill Curve – The Assured Refill Curve indicates the end-of-month storage content required to ensure refill of the reservoir while releasing power discharge requirement outflows. The ARC is based on 1931 historical volume of inflow during the refill period. The year 1931 represents the second lowest historical January through July volume inflow for the Columbia River for the period 1928 to 1958 measured near The Dalles, Oregon.
Average Annual Energy or Average Annual Generation – The average yearly energy production of a hydroelectric project or system as determined from a long-term streamflow record. For purposes of Treaty downstream power benefit determinations, the average output of hydroelectric projects is based on regulation studies using the 30 years of historical streamflows experienced during the period 1928–58, as modified by appropriate irrigation depletions. (Protocol Section VIII)
Average Annual Usable Energy – That portion of the average annual energy production of the United States base system that is usable as defined by Annex B to the Treaty – specifically, firm energy, plus thermal displacement energy, plus up to 40 per cent of remaining energy. This is one of the two components of the downstream power benefits. (Annex B Paragraph 3)
Average Annual Usable Secondary Energy – A hydro system’s average annual generation less its firm energy capability. This is one of the three parameters used in Step I to evaluate generation optimality.
Average Critical Period Load Factor – The average of the monthly load factors during the critical streamflow period. (Treaty Article I)
Average Megawatt – A unit of average energy output over a specified time period (total energy in megawatt-hours divided by the number of hours in the time period). Used in the Pacific Northwest for comparing a plant or system’s energy output (average power output) to its capacity.
Base System (or U.S. Base System) – The plants, works, and facilities listed in the table in Annex B of the Treaty, as enlarged from time to time by the installation of additional generating facilities, together with any projects that may be constructed on the mainstem Columbia River in the United States. The table in Annex B is in essence the 1961 Columbia River hydropower system. (Treaty Article I and Annex B)
B.C. Hydro System – The transmission facilities located within the Province of British Columbia and owned by B.C. Hydro. (Entity Agreement for Delivery and Disposition of the Canadian Entitlement, page 3)
Called Upon – Storage the U.S. can call upon beginning in the year 2024 for flood control. See also On-Call.
Canadian Entitlement – Under the Columbia River Treaty, Canada’s 50-per cent share of the increase in usable energy and capacity downstream [“Downstream Power Benefits”] from and based on the filling of the three reservoirs at Duncan, Keenleyside, and Mica storage dams in Canada and the reservoir behind Libby Dam in Montana.
Canadian Entitlement Capacity – Dependable hydroelectric capacity forming part of the Canadian Entitlement, expressed in megawatts. (Entity Agreement for Delivery and Disposition of the Canadian Entitlement, page 4, and Canadian Entitlement Capacity Reduction Agreement, page 3)
Canadian Entitlement Energy – Average usable hydroelectric energy forming part of the Canadian Entitlement, expressed in megawatts. (Entity Agreement for Delivery and Disposition of the Canadian Entitlement, page 4)
Canadian Entity – The agency that implements the Columbia River Treaty for Canada. The Canadian Entity for the purposes of the Treaty’s Article XIV is B.C. Hydro, which is a Crown Corporation of British Columbia. For the purpose of disposing of the Canadian Entitlement to downstream power benefits directly in the United States, the Canadian Entity is the government of British Columbia.
Canadian Re-operation – Five studies are generally performed to complete the AOP and DDPB studies. Once the three U.S. optimum studies are complete, the next stage in the process is to complete the “Canadian Re-operation”. This stage involves developing project-specific operating criteria for Canadian storage projects that optimize generation in both countries.
Canadian Treaty Storage – The 15.5 Maf of storage provided by Canada under Article II of the Treaty at the Mica Creek, Arrow Lakes, and Duncan Lake projects. Also called Treaty Storage. (Treaty Article I)
Canadian System – The Canadian projects included in the AOP and DOP studies. In the most recent AOPs, the Canadian System has been defined as Duncan, Arrow (Keenleyside), Mica, Revelstoke, Kootenay Canal, Corra Lynn, Upper Bonnington, Lower Bonnington, South Slocan, Brilliant, Seven Mile, and Waneta.
Capability – The maximum load that a generator, turbine, power plant, transmission circuit, or power system can supply under specified conditions for a given time interval without exceeding approved limits.
Capacity – The load for which a generator, transmission circuit, power plant, or system is rated. May be used synonymously with capability.
Capacity Credit – The dependable hydroelectric capacity to be credited to Canadian storage in accordance with Annex B of the Treaty and paragraphs IX and X of the Protocol to the Treaty. (Entity Agreement for Delivery and Disposition of the Canadian Entitlement, page 4, and Canadian Entitlement Capacity Reduction Agreement, page 3)
Capacity Credit Limit – The Treaty specifies that the dependable hydroelectric capacity benefit shall not exceed the difference between the capability of the base system without Canadian storage and the maximum feasible capability of the base system with Canadian storage to supply firm load during the critical streamflow periods.
Columbia River Treaty – The 1961 Treaty, ratified in 1964, between the United States and Canada relating to cooperative development of the water resources of the Columbia River Basin, and Annexes A and B to that Treaty.
Coordinated Hydro Load –[also Residual Hydro Load] The treatment within the PNWA of all hydro-served loads and portions of load of a service control area proportionate to that area’s hydro generation as though it were all a single load of a single control area; the total load minus all resources that are not coordinated hydro.
Coordinated System – Contractually, the system of hydroelectric projects located on the U.S. portion of the Columbia River and major tributaries that are operated together on a coordinated basis under the terms of the Pacific Northwest Coordination Agreement. The term is sometimes used in a more general sense to include also those projects that are operated by utilities not participating in the Coordination Agreement.
Critical Period – The historical streamflow period when the water available from reservoir releases plus the natural streamflow is capable of producing the least amount of hydroelectric power in meeting system load requirements. Normally the critical period begins with the initial release of stored water from full reservoir conditions and ends with the reservoirs empty. (Treaty Article I) Also defined as the streamflow sequence during the historical record when water available from storage operated optimally to maximize power within all non-power constraints is capable of producing the least amount of FELCC shaped the same as the hydro firm load (i.e., uniform surplus/deficit).
Critical Period System Regulation Study – The regulation that develops critical rule curves for each reservoir and determines the length of the critical period and the firm energy load carrying capability of the system.
Critical Rule Curves – Critical rule curves, developed for each reservoir by the Critical Period System Regulation Study, are the end-of-month storage contents attained by the storage reservoirs. A critical rule curve provides a monthly guide to reservoir storage drafts and fills to provide an optimum power operation to meet system FELCC during periods of low inflows. In multiple-year critical periods, there will be a critical rule curve for each corresponding year of the critical period.
Dependable Capacity – For purposes of Treaty computations, dependable hydroelectric capacity to be credited to Canadian storage is defined as (a) the difference in the average rates of generation during the critical period with and without Canadian storage, divided by (b) the average of the monthly load factors during the critical period of the Pacific Northwest area, as determined from the Step I study. (Annex B Paragraph 2)
Dependable Peaking Capability – The reliably expected maximum output of a generating plant or plants during a specified peak-load period.
Detailed Operating Plan – The Detailed Operating Plan is similar to the Assured Operating Plan except that it is prepared immediately prior to each operating year. The DOP is developed from the AOP for that year and reflects the latest load, resource, flood control, and other pertinent data as mutually agreed to by the Entities. The Detailed Operating Plan serves as a guide and provides criteria for actual operation of the Canadian storage during the immediately ensuing operating year. (Treaty Article XIV-2(k))
Determination of Downstream Power Benefits – The calculation of downstream power benefits, both energy and capacity, in the United States resulting from Canadian Treaty Storage. This calculation is made annually in conjunction with the Assured Operating Plan.
Determination of Thermal Displacement Market – Calculation of the portion of generation in Columbia Basin from U.S. Step I thermal plants that can potentially be displaced with hydroelectric secondary energy minus System Sales, with System Sales being uniformly distributed over all months in the year. This computation is required by the Columbia River Treaty.
Discharge – Volume of water released from or through a project at a given time, usually expressed in cubic feet per second.
Downstream Power Benefit – The difference in the average annual usable energy and dependable capacity capable of being generated in the United States with and without the use of Canadian Treaty storage. (Treaty Article VII and Annex B)
Drawdown – The distance that the water surface of a reservoir is lowered from a given elevation as the result of the withdrawal of water due to discharge requirements exceeding inflows. This term is also used to refer to the maximum drawdown for power operation, from normal full pool to minimum power pool. Although drawdown is usually expressed in feet of elevation, it is sometimes expressed in terms of millions of acre-feet of storage withdrawn.
Drawdown Period (Evacuation Period) – That portion of the annual reservoir operation cycle when reservoirs are drafted to provide space for flood control and to maximize energy production; on the Columbia River system, this period typically extends from September 1 through April 15. PNCA defines the drawdown period more specifically in terms of energy in storage (PNCA Section 2k).
End-of-Month Contents – Volume of storage contained in a reservoir at the end of a given month, usually expressed in millions of acre-feet.
Energy Content Curve – As defined by the PNCA, the ECC is a guide to the use of storage water from each reservoir in the coordinated system that is used to define certain rights, entitlements, obligations, and limitations. ECCs are designed to provide sufficient storage at all times so that the coordinated system will be able to generate its firm energy load carrying capability under a recurrence of any historical streamflow sequence. As a practical matter, the ECC defines the level of drawdown below which no secondary energy loads will be carried. The ECC (sometimes called the Base Energy Content Curve) defines the reservoir levels that must be maintained to ensure that reservoirs will refill under 1931 (the third worst) water conditions. It is the higher of two curves – the Critical Rule Curve and the Assured Refill Curve – and its upper limit is the Flood Control Rule Curve.
Energy Entitlement – One-half of the difference between the Step II usable energy and the Step III usable energy (downstream benefits).
Entities – The entities designated by Canada and the United States under Article XIV of the Treaty to formulate and carry out the operating arrangements necessary to implement the Treaty. (Treaty Articles I and XIV) See United States Entity and Canadian Entity.
Firm Energy – Electric energy that is considered to have assured availability to the customer to meet all or any agreed-upon portion of the customer’s firm load requirements.
Firm Energy Load Carrying Capability – As defined in the PNCA, FELCC is the firm energy load that the Pacific Northwest coordinated system is able to supply in any period from the firm resources of the coordinated system after deducting the required energy reserve and forced outage reserve. Also called Firm Energy Capability.
Firm Hydro Energy – The firm energy capability of the hydro system, based on certain specified probability considerations. Firm hydro energy is determined for Treaty studies using the 1928-1958 historical water sequence and calculating the maximum amount of energy load that can be served in the worst water sequence and utilizing all available storage.
Firm Load – That part of the system load that must be met with firm power.
Firm Load Carrying Capability – The maximum amount of annual firm energy (shaped load) that the system can continuously support while drafting the active storage of the system from full to empty under the most adverse sequence of streamflows occurring within the adopted historical record (the Critical Period); collectively, Firm Energy Load Carrying Capability and Firm Peak Load Carrying Capability.
Firm Power – Power that is considered to have assured availability to the customer to meet all or any agreed-upon portion of a customer’s load requirements. It is firm energy supported by sufficient capacity to fit the load pattern. The availability of firm power is based on the same probability considerations as is firm energy.
Flex operation – Canada’s operation of individual projects for maximum Canadian benefits, so long as the flow at the border is the same as that specified in the operating plan.
Flood Control Curve – 1) Mandated and coordinated by the Corps of Engineers, a graph or table representation showing the reservoir drawdown necessary to control floods; 2) Specification of flood control storage space maintained to meet local and system flood control requirements, then used as an input to HYDSIM as monthly storage upper limits.
Flood Control Operating Plan – An operating plan that prescribes criteria and procedures by which the Mica, Duncan, Arrow, and Libby reservoirs are to be operated to achieve the flood control objectives of the Treaty. The Flood Control Operating Plan is prepared by the Entities and consists of flood control storage reservation diagrams and associated criteria for each of the reservoirs. (Annex A Paragraph 5 and FCOP Section 1-2)
Flood Control Refill Curves – Curves used to provide a 95 per cent confidence level of refill. Flood Control Refill Curves help guide the refill of reservoirs during the spring refill period and ensure that the flood control regulation does not adversely affect refill insofar as possible. The refill curves define the upper reservoir elevation at any point during the refill period.
Flood Control Refill Period – Commences 10 days prior to the date the unregulated mean daily discharge is forecast to first exceed the controlled flow objective at the Dalles Dam. The end of the Flood Control Refill Period will be when no further flood potential exists at any of the damage areas.
Flood Control Rule Curve – Flood Control Rule Curves, also called Upper Rule Curves or Mandatory Rule Curves, specify the amount of flood control storage space that must be maintained to meet local and system flood control requirements. These curves define the maximum reservoir elevation that must not be exceeded except during flood regulation. Flood Control Rule Curves are made up of two components: a fixed component guides drawdown during the fall to ensure that minimum flood control requirements can be met, and a variable component during winter and spring is based on forecast runoff. For Treaty projects, the Flood Control Rule Curves are based on the Flood Control Storage Diagram/Reservation Curves.
Flood Control Storage (Treaty) – A total of 15.5 Maf of storage is available in the three Canadian Treaty reservoirs for control of floods. Of this total, 8.45 Maf of storage is classified as Primary Storage and is available on a year-to-year basis. The remaining 7 Maf is classified as On-Call storage and is available only for control of large floods. (Treaty Articles V and VI and FCOP Section III)
Flow – Streamflow; the rate at which water passes a given point in a stream, usually expressed in cubic feet per second.
Reservoir Elevation – The water surface elevation immediately above a dam or hydroelectric plant intake structure.
Forecast Mode – A study mode that assumes limited foreknowledge of basin hydrology.
Freshet – A substantial rise in streamflow caused by rain or snowmelt. In the Columbia River system, the freshet normally refers to the snowmelt runoff occurring in the late spring and early summer.
Generation – The act or process of producing electric energy from other forms of energy; also the amount of electric energy so produced.
Gigawatt – One million kilowatts.
Head – The measure of potential energy due to the difference in water surface elevation between two points. In hydropower regulation studies, head is the difference in elevation between the forebay elevation and the tailwater.
Headwater Projects – Reservoirs located on upper tributaries of the Columbia River. They generally have large storage capabilities relative to their inflow and are operated to provide flood control and power benefits at downstream hydro plants. They cannot be operated on a day-to-day basis for flood control of the lower Columbia due to the relatively long time it takes for a change in outflow at these reservoirs to have a significant effect upon streamflow in the lower Columbia River. Headwater Projects are those classified as Category I reservoirs in the Flood Control Operating Plan. (FCOP Section 2-4)
Hydro Independents – The hydroelectric projects of the region that are not regulated in reservoir simulation models of the coordinated Columbia River system. The output of these projects is accounted for by reducing system loads rather than simulating the operation of the projects. These projects are small and have little or no hydraulic effect on the operation of the coordinated system. Hydro independents modeled in HYDSIM include the Federal Williamette projects, Yakima projects, and projects upstream of Brownlee.
Hydroregulation Studies – Studies that simulate operation of the reservoir system.
Hydraulic Capacity – The maximum flow that a hydroelectric plant can utilize for power generation.
HYDSIM – is the hydro regulation model that is used in AOP studies. It simulates the month-to-month operation of the Pacific Northwest hydropower system in accordance with operating criteria and constraints based on the Columbia River Treaty. HYDSIM is used to determine the hydro system generation and resulting project outflows, ending storage contents, and so on under varying inputs of inflows, power loads, operating procedures and constraints, and physical plant data. HYDSIM is a deterministic model that uses rule curves and flow/storage constraints to achieve operating objectives, especially for power, flood control, fish flows and spill, and recreation.
Independent Power Producer – A non-utility producer of electricity that operates one or more generation plants under the 1978 Public Utility Regulatory Policies Act (PURPA). Many independent power producers are cogenerators who produce power for their own use and sell the extra power to their local utilities.
Initial Control Flow – The annual flow target at The Dalles. The ICF is fundamentally a water balance calculated using the available system storage volume on April 30 and the forecasted seasonal runoff volume. The resultant volume is then converted to a flow rate and labeled the ICF. The simplistic interpretation of this ICF is that all unregulated flow above the ICF during the runoff season at the Dalles Dam can be stored, thereby refilling reservoirs. The ICF is thus the trigger to initiate system refill. The ICF is used to ensure that the projects refill while minimizing the peak runoff at The Dalles. The procedure for determining the ICF is presented in the Treaty FCOP.
Installed Capacity – Same as nameplate capacity unless otherwise specified.
International Joint Commission – The IJC was created under the Boundary Waters Treaty of 1909 between the United States and Canada to render decisions on the use of boundary waters, investigate important problems arising along the common frontiers not necessarily connected with waterways, and make recommendations on any question referred to it by either government. Differences arising under the Treaty that the Entities and PEB cannot resolve may be referred by either country to the IJC for decision. (Treaty Article XVI, and Annual Report Section II)
Intertie – Transmission circuit used to tie or interconnect two load areas or two utility systems.
Irrigation Depletions – Adjustments to streamflow data to account for projected irrigation withdrawals.
Kilowatt – The electrical unit of power that equals 1,000 Watts or 1.341 horsepower.
Kilowatt-hour – The basic unit of electrical energy. It equals one kilowatt of power applied for one hour.
KSFD – thousand second-foot-days; a unit of reservoir volume equal to 86,400,000 ft3, or ~1989 Kaf, and equivalent to a flow of 1000 ft3/second for one day.
Libby Coordination Agreement – The Columbia River Treaty Entity Agreement Coordinating the Operation of the Libby Project With the Operation of Hydroelectric Plants on the Kootenay River and Elsewhere in Canada, signed in the year 2000.
Load – The amount of electric energy delivered or required at any specified point or points on a system.
Load Factor – The ratio of the average load over a designated period to the peak load occurring in that period.
Load Shape/Pattern – The characteristic variation in the magnitude of the power load with respect to time, such as a daily, weekly, or annual period.
Local Flood Control – Small basin or sub-basin measures taken to control flooding within a relatively limited area, usually without consequences for a larger-area flood control regime.
Long-Term Planning Studies – Hydro regulation studies that simulate longer-term system conditions; usually in a six-year AOP horizon.
Transmission Losses – The general term applied to energy (kilowatthours) and power (kilowatts) lost when operating an electric system, occurring mainly as energy turns to waste heat in electrical conductors and apparatus. System losses consist of transmission, transformation, and distribution losses and unaccounted-for energy losses between sources of supply and points of delivery.
Maximum Outflows – Maximum discharge levels that have been established either for flood control or to ensure that as much of the project discharge as possible is used for power generation.
Megawatt – One thousand kilowatts.
Megawatt-hour – One thousand kilowatt-hours.
Mica/Arrow Balancing – The operation of Mica to specific Project Operating Criteria, together with compensating changes to Arrow’s operation (in the event that Mica’s operation results in more or less than Mica’s share of draft, compensating changes will be made from Arrow to the extent possible).
Minimum Outflows – Minimum discharge levels that must be maintained either for power or for non-power river uses such as fish and wildlife, navigation, or irrigation; in some cases minimum generation requirements establish minimum discharge levels.
Minimum Pool – The minimum forebay water surface elevation within the reservoir’s normal operating range.
Modified Flows/Streamflows – Observed or historical flows that have been adjusted to a common level of development by correcting for the effects of irrigation and other diversion demands, return flows, and changes in storage of upstream reservoirs and lakes that are not included in the reservoir simulation model. Modified flows are used for all Treaty regulation studies.
Modified Regulation – The Modified Regulation fine-tunes the Preliminary Regulation to ensure that the hydro system is used to its fullest potential. Part of this process includes determining interchange energy obligations and shifting and shaping FELCC. (PNCA Sections 6c and 6d)
Monthly Load Factor – The ratio of the average load over a month to the peak load occurring in that month.
NGVD – National Geodetic Vertical Datum; a measure of land elevation essentially the same as Mean Sea Level (MSL); a fixed surface reference established by the U.S. Coast and Geodetic Survey in 1929 as the datum to which relief features and elevation data are referenced.
Non-firm Energy – Same as Secondary Energy.
Non-Power Operating Requirements – Operating requirements at hydroelectric projects that pertain to navigation, flood control, recreation, irrigation, fish and wildlife mitigation, and other non-power uses of the river.
Non-Treaty Storage – Reservoir storage in Canadian reservoirs on the Columbia River in excess of that which is regulated under the Treaty.
Non-Triggered Years – Years for which Called Upon was not triggered based on forecast flow volume.
Observed Mode – A mode of conducting a study in which perfect foreknowledge of the basin hydrology is assumed.
Operating Criteria – All the rule curves of all kinds, APOC, Mica operating limits, draft limits, maximum and minimum flows that apply to and guide reservoir operations.
Operating Limits – Operating rules that set limits on the operation of projects for hydropower. Examples are flood control rule curves, minimum discharge requirements for fisheries and navigation, and maximum and minimum reservoir elevations/content.
Operating Procedures – Specific steps or tasks that should be taken by one or more specific operating positions to achieve specific operating goal(s). OR Documents that identify specific steps or tasks that should be taken by one or more specific operating positions to achieve specific operating goal(s). The steps in an operating procedure should be followed in the order in which they are presented, and should be performed by the position(s) identified; a document that lists the specific steps for a system operator to take in removing a specific transmission line from service is an example of an operating procedure.
Operating Rule Curve – The Operating Rule Curve for each reservoir is a synthesis of other curves, as follows:
Aug 1 – Dec 31: ORC = Higher of CRC1 and ARC Jan 1 – Jul 31: ORC = Lower of VRC and Higher of CRC1 and ARC Jan 1 – Apr 15: ORC is limited to no lower than ORCLL At all times: ORC is limited to no higher than the URCThe Operating Rule Curve allows, but limits, reservoir operation for the purpose of producing secondary energy. Reservoirs are drafted below Operating Rule Curves only if required to maintain the FELCC of the system.
Operating Rule Curve Lower Limit – The minimum month-end storage contents that provide a high probability that the system will be capable of meeting its FELCC during the period January 1 through April 30 in the event that the Variable Refill Curves permit storage to be emptied prior to the start of the freshet. The ORCLL is developed from 1936–37 water conditions, which represent the lowest January 1 through April 30 run-off volume for the system as a whole.
Operating Year – The period upon which the system’s reservoir seasonal operating cycle is based. It begins on August 1, which is when the reservoir system is generally at its highest level, and extends through July 31 of the following year.
Outflow – The total flow released from a reservoir project, including water passed through the powerhouse, spillway, regulating outlets, fish passage facilities, and navigation facilities.
Pacific Northwest Area – As defined in Section 7 of Treaty Annex A, the area comprised of Oregon, Washington, Idaho, and Montana west of the continental divide, but excluding areas served on the Treaty ratification date by the California-Oregon Power Company and the Utah Power & Light Company (now the service area of Pacific Power & Light Company and still excluded from the Pacific Northwest Area loads).
Peak Load – Literally, the maximum load in a stated period of time. Sometimes the term is used in a general sense to describe that portion of the load above the base load.
Peaking – Power plant operation to meet the variable portion of the daily load.
Peaking Capability – The maximum peak load that can be supplied by a generating unit, station, or system in a stated time period. For a hydro project, the peaking capability would be equal to the maximum plant capability only under optimum head and flow conditions; often the peaking capability may be less due to reservoir drawdown or tailwater encroachment. Also called Peaking Capacity.
Peak Reserve – Extra generating capacity available to meet unanticipated demands for power
Permanent Engineering Board – An independent board established under provisions of the Treaty to periodically review and report to the governments of Canada and the United States on operation of the Treaty projects and to investigate and report on any other matter coming within the scope of the Treaty at the request of either Canada or the United State. (Treaty Article XV)
Plant Factor – The ratio of (a) the average load on the generating plant for the period of time considered to (b) the capacity rating of the plant. Unless otherwise identified, capacity factor is computed on an annual basis.
Power Discharge Requirements – The project discharges used to compute VECCs and determined from the Refill Studies. These flows are based on FELCC needs and ensure a reasonable probability of refill under better than critical water conditions. The PDRs, which are established for the months of January through July for each year in the study period, set a limit on the amount of secondary energy that can be produced under various runoff conditions. In planning, PDRs are determined for three forecast runoff levels. When the runoff forecast becomes available in January, new PDRs are determined by interpolation.
Power Draft – Release of water from a reservoir(s) through a generator(s) for the purpose of producing electric power.
Power Refill studies – These studies develop guidelines for generation to produce secondary energy while protecting future FELCC and ensuring a high probability of refill.
Primary Storage – The 8.45 Maf of flood control storage that is available in each year in the three Canadian Treaty reservoirs for control of floods. (Treaty Article VI and FCOP Section 3-1)
Principles and Procedures (POP) – A document prepared by the Columbia River Treaty Operating Committee to serve as a guide for the preparation and use of hydroelectric operating plans for Canadian storage. It is updated periodically to incorporate changes that reflect current operating practices.
Project Operating Criteria – Constraints on operations (e.g., flow targets, minimum and maximum discharge) at a particular generating project to reflect characteristics and uses of the environment at and near the project.
Project Operating Procedures – Specific steps or tasks that should be taken by one or more specific operating positions to achieve specific operating goal(s) for one specific
Proportional Draft – A procedure for equitably distributing draft of storage among the reservoirs in the system during poor water years to ensure that FELCC will be met when reservoirs must be drafted below Energy Content Curves.
Proportional Draft Point – Points for each reservoir established to distribute proportional draft among reservoirs when low water conditions occur.
Protocol – A document accompanying an exchange of notes dated January 22, 1964 that clarifies certain particulars of the Treaty. The Protocol has the same force as the Treaty itself.
Refill Curve – A guide to operation of a reservoir that optimizes the production of usable energy consistent with an agreed probability that reservoir refill will not be jeopardized by secondary energy production. A reservoir shall not be drafted below its Refill Curve to serve any secondary energy loads, unless required by established operating procedures at the project. Two Refill Curves are developed to guide reservoir operations. The Variable Refill Curve is based on a 95 per cent refill probability, and the Assured Refill Curve is developed using the second lowest January–July volume inflow of historical streamflows (1931). In essence, the ARC provides a check on the VRC and allows a deeper draft if the VRC is found to be overly conservative.
Refill Period – That portion of the annual reservoir operation cycle when reservoirs are allowed to refill; on the Columbia River system, this period typically extends from the middle of April through the end of July. The PNCA defines the refill-hold period as that period beginning at the end of the Drawdown Period and ending at the beginning of the next subsequent Drawdown Period. (PNCA Section 2dd)
Refill Study – Refill studies develop PDRs used to compute the ARC and VRC. The studies incorporate the CRCs and FELCC developed in the Critical Period System Regulation Study. The AOP refill studies use a 30-year historical streamflow record, and the PNCA refill studies use a 50-year historical streamflow record. The Refill Studies are intended to determine if energy content curves based on the AOP or Final Regulation will permit meeting FELCC under historical streamflow conditions and will meet a refill objective of 95 per cent confidence of refill before production of secondary energy. (PNCA Section 7)
Regulated Flow – The controlled rate of flow at a given point during a specified period resulting from actual reservoir operation or a simulated reservoir operation.
Hydroregulation Study – A study of simulated operation of a reservoir system.
Renewable Portfolio Standards – Policy of various states, including Oregon, Washington, Montana, and California, that requires electricity providers to obtain a minimum per centage of their power from renewable energy resources by a certain date.
Reoperation – The review and recalculation of the U.S. Optimum Long-Term Study by Canada to produce optimal benefits of power and flood control for both nations.
Reserves – Generating capability that must be provided by a power system in excess of that required to meet forecasted peak loads. This “extra” generation is required to meet unanticipated demands for power or to generate power in the event of loss of generation resulting from scheduled or unscheduled outages of regularly used generating capacity.
Residual Hydro Load – The net result of PNWA loads, thermal installations, and other resources; a residual load for the coordinated hydropower system to meet.
Resources – Means of producing or saving energy that can be used to meet demand for energy (loads).
Return Flow – The portion of a water diversion demand that is returned to the stream system and is available for use downstream.
Rule Curves – Rule curves specify the end of month storage content for the reservoirs. In doing so, they delineate a schedule of reservoir drafts and fills that are designed to utilize storage and natural flow in such a manner as to produce the optimum amount of FELCC, usable secondary energy, and reservoir refill probability under any pattern of streamflow. Flood control rule curves also provide guidance to ensure adequate flood control on the Columbia River and its tributaries. The rule curves are derived from system-wide power regulation studies and hydrologic analyses of flood control needs in the basin designed specifically to develop and test the criteria.
Run-of-River Plant – A hydroelectric plant that depends for generation chiefly on the flow of a stream as it occurs, as opposed to a storage project that has sufficient storage capacity to carry water from one season to another. Some run-of-river projects have a limited storage capacity (pondage) that permits them to regulate streamflow on a daily or weekly basis.
Secondary Energy – All hydroelectric energy generated in excess of the firm energy capability. This additional generation results from streamflows greater than those in the critical period studies that determine the hydro firm energy capability.
Shaped Load – Energy demand whose variance over time has been revised mathematically to dispose of surplus energy and balance loads and resources.
Short-Term Market – Purchases and sales of firm and non-firm power ranging from the next hour, for an hour, up to five years.
Spill – Water passed over a spillway without going through turbines to produce electricity. Spill can be forced, when there is no storage capability and flows exceed turbine capacity; can be due to lack of market; or can be planned. An example of planned spill is when water is spilled to enhance juvenile fish passage.
Standard Flood Control – Standard Flood Control is used in all Treaty regulation studies including the AOP, DOP, and TSR and is defined in the Columbia River Treaty Flood Control Operating Plan. See also VarQ, Libby variable outflow flood control.
Step I/II/III Studies – Thirty-year system regulation studies made annually to determine the increase in dependable hydroelectric capacity and the increase in average annual hydroelectric energy resulting from operation of the Treaty projects. These studies are a part of the process to develop the AOP and the downstream power benefits. These studies are prepared each year for the sixth succeeding year in accordance with Treaty Annex B. (Annex B Paragraph 7)
Step I Study – The Step I system, defined in Annex B, includes the planned total US hydro and thermal system, including projected and existing resources used to meet Step I loads, with 15.5 Maf of Canadian Treaty storage. The Step I loads are the Pacific Northwest Area loads, including Grand Coulee pumping, adjusted for power flows into and out of the Pacific Northwest in accordance with the 1988 Entity agreements. The thermal installations, hydroplant data, and operating procedures, to the extent they apply to the respective critical periods, are carried over from Step I to the Step II and III studies. The Step I studies also determine the operating criteria for Treaty projects to be used in the DOP unless otherwise agreed by the Entities.
Step II and III Studies – The Step II system is the Base system as defined in Annex B(essentially the 1961 hydro system) with the addition of 15.5 Maf of Treaty storage. The Step III hydro system is the Base system only and does not include Treaty storage. The thermal installations, hydro plant data, and operating procedures, to the extent they apply to the respective critical periods, are carried over from Step I to the Step II and III studies. Step II and III loads are shaped to the PNWA load shape, including Grand Coulee pumping. The downstream power benefits are calculated from the results of system capability studies for the Step II and III systems.
Storage – Space in a reservoir that is usable for impounding water. The Treaty deals only with storage regulation for flood control and hydroelectric power generation, but many of the reservoirs in the system are regulated for other purposes as well. (Treaty Article I)
Storage Content – Volume of water in a reservoir at any particular point in time.
Storage Project – A project with a reservoir of sufficient size to store water in the high-flow season for release in the low-flow season, thus providing a firm flow substantially greater than the minimum natural flow. A storage project may have its own power plant or may be used only for increasing generation at downstream plants.
Storage Reservation Diagram – A graph of a family of curves of Required Storage Space by month. Each curve on the SRD corresponds to a given seasonal volume – the volume of flow to pass a certain point over a period of months.
Streamline Procedures – Reference to a way to complete AOP studies by utilizing either 1) numbers and calculations from previous years or 2) agreed-upon numbers and values in place of extensive studies and modeling.
System Regulation Study – Each operating plan specifies System Operating Criteria, which are developed from a series of System Regulation Studies designed specifically to develop and test the criteria: System Regulation Studies simulate a continuous operation over 70 years (30 for Steps II/III) with the operating criteria established above and, if applicable, Mica/Arrow operating criteria that optimize generation in both countries.
System Sales – Flows of firm power out of the Pacific Northwest Area, excluding: flows of power from exchanges of firm power that neither increase nor decrease the net flow of power between the PNWA and other regions; plant sales; flow-through transfers of power from outside the PNWA to outside the PNWA; and delivery of Canadian Entitlement out of the PNWA.
Thermal Displacement Market – That portion of the generation from the U.S. Step I thermal plants that can potentially be displaced with hydro secondary energy minus System Sales, with System Sales being uniformly distributed over all months in the year. (Annex B Paragraph 3)
Transmission Interconnection (Intertie) – Transmission circuit used to tie or interconnect two load areas or two utility systems.
Treaty – The Treaty between Canada and the United States of America relating to the Cooperative Development of the Water Resources of the Columbia River Basin, including its Annexes A and B, ratified on September 16, 1964.
Treaty Obligation – All of the series of obligations, tasks, duties and responsibilities from Canada to the U.S., and the U.S. to Canada, spelled out in the Treaty.
Treaty Storage – Usually refers to the storage provided by Canada under Article II of the Treaty at the Mica Creek, Arrow Lakes, and Duncan Lake projects. All storage authorized by the Treaty, including Libby, is sometimes loosely referred to as Treaty storage.
Treaty Storage Regulation – A hydroregulation study based on the DOP operating criteria and current operating data, including streamflows, operating rule curves, and flood control rule curves. A TSR study is completed at least twice per month to compute the DOP storage obligation for Canadian storage. Loads and non-power constraints are not updated for current conditions.
U.S. Entity – One of the two parties designated to operate the Columbia River Treaty; made up of the Administrator of the Bonneville Power Administration (chairman) and the Division Engineer, North Pacific Division, U.S. Army Corps of Engineers (member).
Unregulated Flow – Observed streamflow adjusted to eliminate the effects of reservoir regulation but reflecting the effects of natural storage in lakes and river channels.
Upper Rule Curve – The month-end reservoir levels at each project during the evacuation and refill periods. Upper Rule Curves define the maximum allowable storage content of each reservoir and are determined from flood control regulations, in accordance with the Treaty FCOP. Also see Flood Control Rule Curve.
Usable Energy – All hydroelectric energy that can be used in meeting system firm and secondary loads. It is possible that there may not be a market for all of the secondary energy that could be generated in years of abundant water supply, and some of the water may have to be diverted over project spillways and the energy wasted.
U.S. Optimum Study – The U.S. AOP-like study that determines what the power output and flood control protection should be for the maximum benefit in the U.S.
Variable Refill Curve – The VRC indicates the end-of-month storage content required during the refill period to refill with 95 per cent confidence each cyclic reservoir consistent with (1) atsite volume inflow forecasts, (2) Power Discharge Requirements, and (3) upstream reservoir refill requirements.
VarQ – VarQ means variable Q, or variable flow, as it pertains to flood control limits. It is an adaptive management technique that, rather than requiring fixed and rigid releases of water as levels in a reservoir approach a fixed flood control rule curve, allows managers to retain more water during the flood control season.
Year – A 12-month period for a particular purpose.
Operating Year – The August 1 through July 31 period, used for regulation studies for both the Treaty and PNCA.
Reporting Year (Entity and PEB) – The period covered by the Annual Report of the Columbia River Treaty, Canadian and United States Entities, and the Permanent Engineering Board’s Annual Report to the Governments of The United States and Canada, specifically, October 1 through September 30. The reporting period is tied primarily to the need to report flow data, which is published by the responsible agencies on a Water Year basis. (Treaty Article XV)
Streamflow Year (Treaty) – The Water Year used in developing the streamflow data upon which Treaty regulation studies are performed: specifically, July 1 through June 30. (Protocol Section VIII)
Water Year – Established by Canadian and United States water resources agencies for purposes of uniformly reporting hydrologic records. The Water Year extends from October 1 through September 30, but the streamflows used for all reservoir regulation studies of the Columbia River system are based on the period August 1 through July 31.