Tualatin Basin Drought 2001

Overview

  The calendar year 2001 proved to be very different from most previous years due to the drought. For the first time since 1977, the reservoir did not fill. Henry Hagg Lake reached a maximum of 179.14’ or 29,035 acre feet of active storage on May 24. This was just 54% of the active storage capacity. Reclamation allocated 27,041-acre feet total to water contractors. Later in the season, this was reduced a small amount to account for operational losses due to measuring gages, sedimentation and evaporation. The total allocations allowed from storage by the Bureau of Reclamation at the beginning of the season were as follows:

Tualatin Valley Irrigation District          12,832 AF

Clean Water Services                          3,479 AF

City of Forest Grove                             3,449 AF

City of Hillsboro                                    3,832 AF

City of Beaverton                                 3,066 AF

Lake Oswego Corp                                383 AF

Total               27,041 AF

 

 

 

 

 

 

 

  The drought of 2001 was a driving factor in District operations. In previous years, natural flow in the river system has met TVID demand until mid May to mid June. 2001 saw the natural supply dwindle in March and April. Because of several “strategic rain events” which came in May, the district did not have to begin drawing from storage until June 1. The average use from storage for June was only 33 cfs. This compared to an average use from storage of 27 cfs in June 2000. The season ended with only 10,702 acre feet being withdrawn from storage behind Scoggins dam, the lowest on record in 8 years.

  The following pictures show comparison views of the 2001 "drought" year and an "average" year, 2002

  Right abutment towards spillway: Notice the amount of rock showing in October 2001 vs. how little is seen when the lake is full, Spring 2002.

                               October 28, 2001                                         April 29, 2002

                                      

Community Involvement

  A number of factors contributed to the lower use including increased awareness, training and conservation, different cropping patterns including less water dependent crops, several rain events and a modified release schedule from Scoggins dam.

All water users were aware of the high potential for a water shortage prior to the irrigation season. Some irrigators planted crops such as wheat that would require less water. Others changed to grass seed. Some of these decisions to change crops were not drought related but had been made earlier to match the agricultural economic climate. Fortunately, those decisions coincided with the low water supply year.

Another factor that helped reduce District use from storage were several “strategic rain events” that occurred in the first several weeks of May. Rain arrived just as the rivers were dropping. The rainfall increased river flows and delayed the call for additional water from storage. Minor deliveries were made to TVID in March and April, primarily for frost control. Municipal and Industrial contractors began calling for releases from Hagg Lake on May 23 when the temperature reached 95 and above in the valley. TVID began their regular release schedule on June 1 and Lake Oswego Corp. started on June 28. Clean Water Services had intermittent releases beginning at the end of August and lasting until November.

District Operations

  Operations at Scoggins dam were modified during the 2001 irrigation season to respond to the Districts needs. Water orders were calculated several times daily and discharge changes were made mornings and evenings including weekends to closely match the amounts and timing of orders. Additional monitoring equipment was installed below the Pump Plant to track flows going to the lower river. Cooperation between District Irrigators the State Watermaster and District personnel was critical in determining amounts of water needed to sustain sufficient natural flow.

  The District used 10,702 acre feet of water from storage in 2001. That compares to an average annual use for the past 10 years (including 2001) of 16,894 acre feet. This reduction would not have been possible without the cooperation of District patrons and the careful management and operations by TVID staff. At the conclusion of the season, TVID still had 2,002 acre feet remaining in storage from its original reduced allocation from the Bureau of Reclamation. No District patron was ever cut short on the amount or rate of water that was needed during the irrigation season. All irrigations needs were met as needed and all water orders were furnished during the time requested. Irrigators adjusted and cooperated fully. The 2001 drought resulted in no harm or injury to TVID or its patrons.

Relief

  Relief came to the Basin beginning on October 21.  Over 2.5 inches of rain was recorded at the dam during the last 10 days of October. The rain continued during November with 12.1” (150% of normal) and December with 11.86 inches (128%). The calendar year ended with 43.0” total for 86% but the water ending September 30 totaled 27.19” or 51.9% of the normal precipitation. The fill curve of 33,000 acre feet was reached on December 18, 2001 after a low on October 27 of only 5,358 acre feet of active storage water remaining. Computed inflow to the reservoir for November and December 2001 was 37,433-acre feet.

 Security

  September 11, 2001 also impacted operations at Scoggins dam. After one week at the highest security level, Scoggins was reduced to a “Security Threat Level II.” Access to the entire Control Works area became restricted to authorized personnel only.

  During the war in Iraq the Bureau of Reclamation set the security level for Scoggins dam at Orange or threat level IV. There is one level higher than orange, which if enacted, would mean imminent danger. Once the war subsided the threat level was reduced back to yellow.

Scoggins Creek branch looking toward Scoggins Dam: There are trees showing far out to the waters edge in October 2001, they are all covered when the lake is full, April 2002    

  October 28, 2001                                              April 29, 2002