Stave River Water Use Plan - BC Hydro

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Stave River Water Use Plan Monitoring Terms of Reference June 13, 2005 result, the option was not explored further because the downstream habitat costs were deemed too high for what was judged to be an uncertain gain in reservoir productivity. Furthermore, the final reservoir management strategy accepted by the CC had within it constraints in downstream releases that inherently created a slightly more stable state in Stave reservoir. The CC agreed to study the consequences of the present WUP, and hence learn more about the littoral productivity response to water level stability, before exploring further the concept of imposing reservoir constraints in future WUP processes. Constraints to reservoir operations, should they be deemed necessary, will come at a high cost to many other values, including power, downstream habitat, and First Nations heritage issues. Clearly defining the relative importance of the littoral zone to over all reservoir productivity, as well as identifying the extent of recovery need to restore full productivity, will help to identify alternative solutions, whether they be operational or physical in nature, that are more cost effective. 2.0 Monitoring Program Proposal 2.1 Objective and Scope The objective of this monitor is to collect the data necessary to test the impact hypotheses outlined in Section 1.3 and hence, address the management questions presented in Section 1.2. The following aspects define the scope of the study: a) The study area will consist on Stave Lake and Hayward Lake Reservoirs. b) Data will be collected at four sites; three on Stave Lake reservoir because of potential spatial differences, and one on Hayward Lake reservoir. c) The program is to be carried out in two phases, an initial 2-3 year high intensity sampling program, and a subsequent base level sampling program. d) The monitor is to continue to the next WUP review period. e) The monitor will focus of variables associated with measures of littoral primary productivity, a parameter assumed to be a component of overall reservoir productivity. 2.2 Approach The basic study design is to compare periphyton growth at various reservoir elevations in Stave Reservoir (a highly variable system) with the pattern found in Hayward Reservoir (a relatively stable system). Growth will be measured by repeatedly sampling periphyton biomass on artificial substrate. The artificial substrata will be mounted on cinder blocks that are placed along permanently established transect lines (Figure 2, Monitor 1) where they will be spaced roughly every 2 m in depth beginning at the ‘full pool’ elevation to a depth equivalent to the light compensation depth at minimum operating elevation. Periphyton growth will be characterised by several parameters, including chlorophyll concentrations, ash-free dry weight estimates of biomass accrual, 14 C primary production, and species composition. BC Hydro Page 28
Stave River Water Use Plan Monitoring Terms of Reference June 13, 2005 Samples will be collected along three transects in Stave Reservoir, and only one transect in Hayward Reservoir. Stave Reservoir is a large system with high glacial (i.e. turbid) inflows at its upstream end. As a result, the potential exists that there may be longitudinal differences in light attenuation rates that in turn could affect the depthrelated, functional response of periphyton growth. Hayward Lake, on the other hand, is much smaller, is free of such glacial influences, and would likely experience less variability. Each transect will be considered as a single sampling unit. As a result, the comparisons between transects will only be descriptive in nature. Statistical analyses will be limited given that replicate samples will not be collected to calculate sample variance. As in the pelagic monitor, the littoral zone monitor will be carried out as a twophased program. The first phase will involve intensive data collection geared towards addressing hypotheses H01 to H011, but with particular focus on H08 to H011. Littoral sampling during this phase will done every 5 weeks from April to November and will involve all variables listed above. The 5-week interval is critical in this monitor, as it is the maximum time that artificial strata can be left in oligotrophic systems without losing periphyton growth to grazing or sloughing. As a result, the periphyton accrual data become accurate indicators of production and when calibrated to 14 C estimates of production, it can be used as a direct measure of production. One of the key outcomes of Phase 1 of the monitor will be a numerical model of seasonal littoral productivity potential based on the founding concepts of the ELZ performance measure. The likelihood of such an outcome will depend on the extent of between-reservoir differences, inter-annual variability in reservoir operations and littoral development. Also a key determinant of the outcome will be the strength of association between operations and the parameters chosen to define littoral development. The second phase of the littoral monitor will be far less data intensive and will focus primarily on annual tests of hypotheses H06, H07 and H010, though anecdotal observations concerning the other hypothesis will be documented. Phase 2 of the monitor will rely on the ELZ modelling done in Phase 1 to predict littoral area given the previous 5 weeks of operation for each reservoir, including a prediction of littoral productivity. These predictions will in turn be related to measured values of littoral primary production (from the accrual data) as a test of the littoral zone model (a test of H010). Results of these annual tests of the ELZ model will be used to refine the model if necessary and test hypotheses H06 and H07. This annual tracking of hypotheses H06 and H07 will provide important insight into the importance of littoral habitat in coastal reservoirs, as well as it’s general relationship to reservoir operations. During Phase 2, all four transects will be sampled every 5 weeks as in Phase 1. At each transect, periphyton samples will be collected at all sample stations, but only 4 samples will be retained for accrual analysis. The spacing of these samples along the transect will be such that it captures the spatial trend of maximum productivity as BC Hydro Page 29
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Stave River Water Use Plan - BC Hydro

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