Analysis of 2001-2002 Power Supply Outlook

read full document >

The ongoing drought has focused concerns about the adequacy of the region's power supply for the coming summer, fall and winter. Operational strategies for the Columbia/Snake river hydropower system are a key component of managing through this year with the objectives of:

  • Satisfying electricity demand through this spring and summer;
  • Achieving reasonable summer flows for salmon migration;
  • Not significantly worsening fall and winter reliability and the ability to meet Biological Opinion (BiOp) reservoir target elevations in 2002; and
  • Limiting the impacts of wholesale power purchase costs on the region's economy and the financial condition of the region's utilities.

To assess the options available to the region, the Council has analyzed several alternatives for the operation of the power system over the coming year. The analysis was done in two stages. The first focused on this spring and summer for two water scenarios -- 1977 water and 1944 water. These years bracket the current runoff volume forecast for 2001. For each of these water years, several operating strategies were evaluated. They include: running the hydropower system to the Biological Opinion constraints for spill and flows; maintaining spill while drafting the system deeper to meet loads; and three strategies that involve significant reductions in spill combined with limited use of deeper drafts, with the objective of achieving BiOp reservoir elevations by the end of August. The analysis looked at such metrics as the amount of curtailment that could be experienced, the cost of purchased power to address any curtailment, end-of-August reservoir elevations, and spring and summer flows.

The second stage of the analysis focused on the operation of the system through the fall and winter with the starting elevation of the reservoirs in September being the primary variable. This analysis was done probabilistically with uncertainty about fall and winter water conditions, temperatures and forced outages of thermal units. The analysis looked at the probability and magnitude of load loss during the winter period and April 2002 reservoir elevations.

The conclusions drawn from this analysis are:

  1. Operating the hydropower system to the BiOp targets for spill and flows would lead to either significant curtailments and/or very large purchased power costs this summer.
  2. Operations this spring and summer that leave reservoirs at the end of August at elevations significantly below BiOp elevations expose the region to significantly increased probability of power supply inadequacy next winter. In addition, such operations would result in a significant probability that April 2002 reservoir elevations will be well below BiOp elevations, thereby reducing spring flows for salmon.
  3. The only alternatives we see that both avoid curtailments and/or large purchased power costs this summer AND return reservoirs to BiOp elevations by the end of August involve substantial reduction in spill and limited drafting of reservoirs beyond BiOp elevations. Reductions in spill can be restored by purchases, reductions in load and additional generation. Alternatives that significantly reduce spill have the additional advantage of reducing market prices this summer and bringing additional income into the region in the form of dollars, returned energy next fall and winter, or both.
  4. Decisions need to be made now, but they can be revisited periodically as the spring and summer unfold. The spill season begins in April. By that time, we will have relatively little additional information about how the rest of the spring and summer are going to unfold. From the power supply standpoint, a prudent approach would be to significantly reduce spring spill. If conditions improve through the spring, it may be possible to restore some spill. If, instead, we were to opt to maintain spill or reduce it only slightly in the spring and if conditions do not improve, that spill energy would be lost to the system and would necessitate more stringent and potentially very expensive measures later on.

The potential for power supply problems this summer and next winter and the probable high cost of power call for continued and increased attention to implementing load reduction, conservation and new generation.