Clowhom Lake Water Use Plan Clowhom Lake Littoral Zone Productivity Study
CLOW-WUP- Littoral Year 1 Study Period: May 31, 2006 - January 31, 2007
D.J. Bates Resource Management Department Sechelt Indian Band PO Box 740 Sechelt, BC V0N 1Y1
February 26, 2007
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Executive Summary The Clowhom Lake littoral zone monitoring study was developed and initiated in 2006 to assess and track changes in littoral zone productivity through time. Recently, the use of littoral zone productivity expressed as an effective littoral zone (ELZ) performance measure is being developed for other BC Hydro reservoirs (Stave) and at each location validation of the methodology is required. This ELZ is based on periphyton accrual and a measure of biomass change over time. As result the ELZ requires permanent sampling locations that are fixed in location and sampled repeatedly over growing seasons. The use of the ELZ as a measure of reservoir productivity resulted from the water use planning process and is intended to help address the following management questions: 1. How accurate is the ELZ model and performance measures in predicting change in littoral zone productivity as a function of reservoir operation? 2. Are there changes in the model parameters that could improve the predictive capability of the model that could be used in future water use planning processes? In order to study ELZ, permanent sampling sites were selected in Clowhom Lake and are fixed with three sample arrays and periphyton sampling substrata. The arrays include 2 horizontal systems and one vertical. The horizontal arrays are located in the upper and lower basin and include 11 sample substrata plates per array that are constructed from 20 cm x 15 cm pieces of plexiglass. The plates are suspended on the bottom from anchors at horizontal intervals that provide plates spacing of 2-metres vertically. This spacing ensures periphyton samples are collected from the high reservoir level to a maximum depth of 22 metres encompassing the operational range and most productive photosynthetic zone. The third array is a vertical and open water array located in the upper basin. This array provides substrata plates oriented vertically from the surface every 2 metres to a depth of 22 metres. The vertical array provides static depth placement moving up and down with the change in reservoir levels. All plates are sampled every 6 weeks throughout the sampling season. The designed array systems originally proposed required modification prior to installation to ensure easy of operation from the surface. Changes and weather prevented early installation of the systems resulting final installation in November 2006. The systems were left in place over the winter and in late December one array sustained damage from a series of storms that moved through the Clowhom Valley. This has resulted in a further delay in 2007 sampling. Changes in the design have begun and sample substrata should be prepared and collecting periphyton in early March, 2007.
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Table of Contents Executive Summary ............................................................................................................ 2 Table of Contents................................................................................................................ 3 List of Figures ..................................................................................................................... 3 1.0 Introduction............................................................................................................. 5 2.0 Study Area .............................................................................................................. 5 3.0 Methods................................................................................................................... 8 3.1 Sampling Arrays ................................................................................................. 8 3.2 Periphyton Growth Substrata and Sampling....................................................... 8 3.3 Environmental Data .......................................................................................... 12 4.0 Results/Discussion ................................................................................................ 14
List of Figures Figure 1: Location of the Clowhom Lake wetland complex in relation to Sechelt, B.C. The complex is at the head of the lake and is accessible by road............................... 6 Figure 2: Locations of the periphyton sample arrays in Clowhom Lake, Salmon Inlet, BC. The arrays are located in both the upper and lower reservoir basin. .......................... 7 Figure 3: Schematic of the horizontal array in plan view (not to scale). The anchors with the periphyton substrata are located in the centre of the array. The design is intended to ensure the plates remain in the same location for each sample and that they can be brought to the surface by a crew in a boat. ................................................................. 9 Figure 4: The horizontal array design. The large buoys (A) are anchored to a 200-lb weight and kept the lines taught. The periphyton plates are located in a line or transect perpendicular to the shore between the 2 anchor buoys and the outside lines are anchored perpendicular to shore (B)................................................................... 10 Figure 5: Schematic showing the periphyton plate and “harness”. The plate floats upright with foam along the top edge. It is weighted with a 2-lb cannonball and slides down a guy line to the anchor base set on the lake bottom. When retrieving the plate the rope on the right side of the harness (in drawing) is released and used to pull the plate up the guy line. Once sampled, the plate is allowed to slide back down the guy line to the anchor and the rope is re-attached on the line between the large buoy and shore.......................................................................................................................... 11 Figure 6: Periphyton substrata plates used on the horizontal arrays. In the top photo the anchor is shown along with the guy line (steel wire and rope for pulling to the surface. In the bottom photo the 2 lb weight used to drop the plate back to the anchor is visible. ................................................................................................................... 12
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Figure 7: A schematic of the vertical “open” water array. The periphyton plates ate attached to a line that is tied off to the large buoy. The line runs down to the anchors through pulley and back to the surface where it is attached to smaller buoys. The plates move with changes in reservoir level. Each plate is separated by 2-metres... 13 Figure 8: The Onset light intensity logger protected in a clear waterproof box and installed in the open on the Clowhom Falls dam. The logger records data every hour and records for up to 75 days before it has to be downloaded.................................. 15
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1.0
Introduction
In 2006, the Sechelt First Nation and BC Hydro began the first year of a 20 year monitoring program to document change in littoral productivity within Clowhom Lake. The monitoring program was implemented following recommendations made during the water use planning (WUP) process. It is designed to test the validity of assumptions that reductions in reservoir productivity may be related to operations management of the facility. In order to predict changes in potential littoral productivity a model has been developed and is currently used in other BC Hydro Reservoirs. This model referred to as the effective littoral zone (ELZ) is conceptually new and requires validation before its implemented as a tool in developing operational standards on Clowhom Lake. This monitoring program addresses the validation of the ELZ model and addresses specific management questions. They are: • • How accurate is the ELZ in predicting changes in littoral zone productivity as a function of reservoir operations? Are there changes in model parameters that could improve predictive capability and reliability for future planning purposes?
The purpose of this report is to present the set-up and methods employed during the first year. The first set of samples will be collected in 2007. 2.0 Study Area
Clowhom Lake is located at the head of Salmon Inlet approximately 30 km from Sechelt BC. Access is limited to boat and aircraft. The lake or reservoir measures approximately 11-km in length and is described as the upper and lower lake which relates to the lakes configuration prior to impoundment in the 1950’s. In this study, sample locations are located in both the upper and lower basin. Three sites in total are used with one located in the lower and 2 in the upper basin (Figure 2). The sites have fixed sample arrays and are georeferenced with UTM coordinates, falling along the shoreline and large orange Scotchman buoys on the lake.
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Figure 1: Location of the Clowhom Lake wetland complex in relation to Sechelt, B.C. The complex is at the head of the lake and is accessible by road.
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Figure 2: Locations of the periphyton sample arrays in Clowhom Lake, Salmon Inlet, BC. The arrays are located in both the upper and lower reservoir basin and are shown in yellow. The green dot indicates the location of the light intensity logger.
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3.0 3.1
Methods Sampling Arrays
The sampling arrays in this study consist of a series of three fixed structures. Two of the arrays are designed in a horizontal plane and the third vertical. The horizontal arrays consist of a total of 11 sample locations and are tied into the shoreline along a transect that runs perpendicular to the shoreline (Figure 3 and 4). The sample location at each horizontal array is fixed with a concrete anchors (Figure 5 and 6) resting on the lake bottom that provide a fixed repeatable location for the periphyton growth substrate. The anchors are spaced along the lake bottom slope and are placed at various horizontal spacing but with a 2-metre vertical spacing. The total depth of the sample locations extends to a depth of 22 metres resulting in 11 sample locations from the high lake level. The third array is a vertical open water system installed near a horizontal array in the upper basin (Figure 7). This array is anchored to the bottom with the periphyton substrata fixed vertically every 2 metres again to a depth of 22-metres. This system is designed to move vertical using a series of buoys and will move vertically with the level of the reservoir ensuring the sample substrata is fully submerged throughout the range of reservoir operation. 3.2 Periphyton Growth Substrata and Sampling
The sample arrays are used to collect periphyton samples throughout the growing season. A total of 7 samples will be collected approximately every 6 weeks. The periphyton samples will be collected from artificial substrata provided by plexi-glass plates. The plates measure 20 cm x 15 cm and are either fixed with a 2 kg weight to the array (horizontal) or a vertical anchor line (Vertical open water). The surface of the plate is roughened in order for the periphyton to adhere to the plate. The plates are set in a vertical fashion and remain upright by fixing polyurethane foam floatation along the top edge. This allows the plates to move and increases the potential for exposure to sunlight (Figure 6) The sampling quadrant consists of 2 areas, one on each side of the plate measuring 50 cm2. The plates are left in the lake for 6 weeks after which they are individually brought to the surface and the quadrant areas scraping and periphyton removed. The quadrant is sampled using a stainless steel putty knife that is exactly 5 cm wide and a reference grove on the plate at the 10-cm point. The quadrate is scraped in one motion into a sample jar, labeled with array number and plate number. The sample is sealed and kept in a dark cooler for shipping to the lab.
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Shore line
Sample anchors where plates are located
Buoys
Toward centre of Lake
Figure 3: Schematic of the horizontal array in plan view (not to scale). The anchors with the periphyton substrata are located in the centre of the array. The design is intended to ensure the plates remain in the same location for each sample and that they can be brought to the surface by a crew in a boat.
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A.
B.
Figure 4: The horizontal array design. The large buoys (A) are anchored to a 200-lb weight and kept the lines taught. The periphyton plates are located in a line or transect perpendicular to the shore between the 2 anchor buoys and the outside lines are anchored perpendicular to shore (B).
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Plate is released and pulled up the guy line shown as the left hand line in this drawing
Line is released at the surface and then used to pull plate up the guy line shown on the left in this drawing
Figure 5: Schematic showing the periphyton plate and “harness”. The plate floats upright with foam along the top edge. It is weighted with a 2-lb cannonball and slides down a guy line to the anchor base set on the lake bottom. When retrieving the plate the rope on the right side of the harness (in drawing) is released and used to pull the plate up the guy line. Once sampled, the plate is allowed to slide back down the guy line to the anchor and the rope is re-attached on the line between the large buoy and shore.
The sampled plate is then cleaned and re-installed on the array in preparation for the next sample period. Once sampling is complete the samples are packaged in the cooler with ice packs and shipped for lab analysis to a predetermined lab facility. The lab processes each sample jar and determines ash free dry weight (AFDW) in order to estimate periphyton biomass and productivity.
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Figure 6: Periphyton substrata plates used on the horizontal arrays. In the top photo the anchor is shown along with the guy line (steel wire and rope for pulling to the surface. In the bottom photo the 2 lb weight used to drop the plate back to the anchor is visible. 3.3 Environmental Data Environmental data collected for this program will be water or reservoir levels, provided by BC Hydro at the Clowhom Dam and light intensity. Light intensity data will be
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2-metre vertical separation
Figure 7: A schematic of the vertical “open” water array. The periphyton plates ate attached to a line that is tied off to the large buoy. The line runs down to the anchors through pulley and back to the surface where it is attached to smaller buoys. The plates move with changes in reservoir level. Each plate is separated by 2-metres.
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collected at the time the arrays are sampled. The light level or photosynthetic active radiation (PAR) will be collected just below the surface and then every 1-metre to a depth of 30-metres using a Li-Cor® Model LI-1400 light metre. In addition to the PAR measurements, a light intensity metre is established at the Clowhom dam to track daily solar radiation through time (Figure 8). This measurement is collected using an Onset® Light Intensity Logger set to record intensity every 1-hour for 75 day periods. 4.0 Results/Discussion
The design and installation of the periphyton sample arrays have required significant modification. Although the direct periphyton sampling process has not been altered the array design provided in the original terms of reference required some modification. As a result the arrays were not installed until November 2006. The arrays remained in the lake through December and January and were revisited in early February when the area became accessible. At that time problems were identified that continue to create problems. On the February visit to the array in the lower basin was accessible but ice on the lake in the upper basin prevented crews from accessing both the open water vertical array and the upper basin horizontal array. This set the initial start time for collecting periphyton back another 4 weeks. In addition to the problems with the ice the February visit allowed close inspection of the array in the lower basin. Severe storms moved through the Clowhom area in both December and January. The result was a significant shift and sloughing of the lower array. Damage to the system and attempts to repair the array are scheduled for March, 2007. It may become necessary to re-locate the array to a more stable area and planned drawdown of the reservoir may help in identifying a new location. Regardless of the physical problems with the arrays, all substrata that remain will be prepared and replaced for periphyton in early March 2007.
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Figure 8: The Onset light intensity logger protected in a clear waterproof box and installed in the open on the Clowhom Falls dam. The logger records data every hour and records for up to 75 days before it has to be downloaded.
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