| Abstract/Description or Keywords |
A severe drought in the summer of 2003 made it clear that water shortages could compromise the aquatic habitat in Sinmax Creek. A section of Sinmax Creek went dry for portions of August and October and all of September, resulting in a fish kill in the dewatered section. Spawning habitat for Kokanee and Sockeye was limited to the three kilometers downstream of the dewatered section. Problems with operation of the weir on Johnson Lake during that time negated any ability it may have had to improve the low flow situation during the most critical time. The intent of this project was to develop strategies to reduce the impact of inadequate flow on fish habitat and to improve water management in Sinmax and Johnson Creeks. The previous operating plan for the Johnson Lake weir was developed in 1996 and prescribed only average discharges from the lake, presumably during an average runoff year. In wet or average runoff years the flows are adequate to meet existing water needs. In extremely dry years the flows cannot meet all needs. One of the primary goals of this study is to provide greater direction regarding operating the weir during drier than average years. Since 1996 an additional 8 years of streamflow data has been gathered, including a wider variation of low flows. The lessons learned during these years are incorporated into this updated operating plan. Data collected and identified during this study improves understanding of the watershed and weir operations. Lessons learned can provide improved dam operation, but the reliability of the conclusions is limited by the poor quality of data collected in past years. A lack of recent flow measurements to confirm the validity of the rating curve at the outlet of Johnson Lake, which converts the gathered water level information to flow rates, is a significant constraint to the reliable interpretation of the this key streamflow data. Changes occurred in the channel, which affected the relationship between water level and flow, but the timing and sequence of the changes cannot be know with any certainty. Draft revisions to operating plan are appropriate, subject to continued monitoring. These revisions could improve the ability to maintain streamflow connectivity during severe droughts (such as 2003) without severe restrictions on water use. Previous studies have overestimated the water availability in the watershed. Updated estimates can provide a more realistic basis for weir operation and more realistic expectations for the goals that can be achieved. The primary objective in the short term should be refining the operation of the Johnson Lake weir to best meet the existing needs. Initial discussions with irrigators and Inmet Mining show promise for cooperatively improving water management, to retain more water instream through the driest sections, and should be pursued while operating under the proposed draft operating plan. The draft operating plan should be reviewed following a 5 year trial period. If necessary, other water conservation initiatives should be pursued at that time. aquatic habitat, low flow, environmental flow needs, streamflow, reservoir, fisheries |
