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MINUTES International Osoyoos Lake Board of Control Public Meeting Oroville-Osoyoos Port of Entry Tuesday October 26, 2004 Attendance
Agenda
* * * * * * * * * * * * * * * * * * * * * Appendix 1Review of 2003/2004 Hydrologic Conditions A Report to the International Osoyoos Lake Board of Control In the southern interior of British Columbia the 12 month period ending September 30, 2003 was unusually dry. Between October 2002 and September 2003 Okanagan Lake inflow were only 24% of normal. Similar trends were observed throughout the region and by October 2003 water levels were typically at or near historic lows for that time of year. In 2003 fall snow accumulation in the Okanagan and Similkameen watersheds were delayed due to warmer than normal temperatures during the month of October. By contrast November was cooler and wetter than normal, resulting in above normal accumulations for the month. Although December was some what drier than normal, January 1 snowpack indices for both the Okanagan and Similkameen were near normal. Throughout the last quarter of 2003 stream flows in the region remained low. Despite releases from Okanagan Lake being kept to near the minimums specified in the operating plan during 2003, the level of the lake was approximately 0.45 metres below target at year end. Temperatures and precipitation during January were near normal. February was quite dry with precipitation in both the Okanagan and Similkameen approximately one third of normal. March temperatures were well above normal and precipitation somewhat below normal resulting in lower accumulations. This resulted in April 1 snow water indices for the Okanagan and Similkameen basins which were 89% and 81 % of normal respectively. Throughout the first quarter of 2004 Okanagan Lake levels were the lowest recorded for this period since records began in 1921. On April 1 the level of Osoyoos Lake was 910.79 feet. Given the lower than normal snowpacks, dry antecedent conditions in the watershed and low lake level Okanagan Lake was not forecast to reach its full pool level of 1123.8 feet in 2004. Condition 8 of the International Joint Commission “Order of Approval”, dated 9 December 1982, provides the criteria for determining whether or not a drought should be declared for Osoyoos Lake for the operational period April 1 to October 31. Criterion 8 (a) is based on the volume of flow in Similkameen River at Nighthawk and Criteria 8 (b) & (c) are based on the inflow volume and maximum level of Okanagan Lake. The drought criteria, 2004 April 1 forecasts and 2004 observed values are presented in Table 1. Table 1:
* Level reached June 27 as calculated using datum correction factor of 340.224 metres, GSC. (With historic correction factor of 340.297 metres the maximum elevation would have been 1123.0 metres.) Based on Criteria 8 (a) and (c) a Drought was declared for the operation of Osoyoos Lake, which allowed the lake to be raised to a maximum of 913.0 feet. The level of the lake was subsequently raised above 911.5 feet into the range of 912.5 to 912.8 feet. On July 2 the drought declaration was rescinded based on a revised Similkameen volume forecast and the observed Okanagan Lake level. Following the rescindment the Osoyoos Lake lake was drawn down and returned to its normal operating range (< 911.5 feet) prior to July 23 as provided for in the notice of rescindment. Lake levels were maintained within the normal operating range for the remainder of the summer. Summer flows in both the Okanagan and Similkameen Rivers were typically lower than normal but higher than flows during summer 2003. In late August and the first part of September the region received greater than normal amounts of precipitation. This additional precipitation allowed Okanagan Lake to return to its target seasonal operating range for the first time since early 2003. Stream flows throughout the region also returned to seasonal norms. |
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