Meeting of the Waters

A Comparison of Suspended Sediment and Discharge of the Illecillewaet River and Asulkan Brook

Geography 477: Field Studies in Physical Geography, Fall 2009

By Hayley Linton and Karilynn DeWolff

Instructor: Dr. James Gardner Department of Geography University of Victoria, BC

Table of Contents

List of Figures ...... 3 List of Tables ...... 3 Acknowledgements ...... 4 Introduction ...... 5 Purpose and Objectives ...... 5 Research Context and Significance ...... 6 Description of Study Area ...... 6 Physical Geography of Glacier National Park and Surrounding Region ...... 6 Illecillewaet and Asulkan Drainage Basins ...... 10 Sampling Site Descriptions ...... 12 Methodology ...... 15 Field Methodology ...... 15 Laboratory Methodology ...... 16 Data and Results ...... 18 Discussion ...... 23 Comparison of Sediment Load during Clear Weather and Storm Weather ...... 23 Differences/Similarities in Suspended Sediment Load of Illecillewaet River and Asulkan Brook...... 25 Differences in Suspended Sediment Load throughout the Day ...... 26 Analysis of Discharge of Illecillewaet River and Asulkan Brook ...... 27 Limitations of Experiment/Recommendations for Further Research ...... 28 Conclusion ...... 30 References ...... 32

List of Figures

Figure 1 - Map of British Columbia with red star showing study location, retrieved from http://www.gonorthwest.com/ BC/British-Columbia-Map.htm ...... 6 Figure 2 - Illecillewaet drainage basin showing sources of meltwater and sediment ...... 11 Figure 3 - Sources of sediment and meltwater for Asulkan drainage basin ...... 12 Figure 4 - Aerial view of study area ...... 13 Figure 5 - Side profile, aerial diagram and photograph of Illecillewaet sampling site ...... 14 Figure 6 - Side profile, aerial diagram and photograph of Asulkan sampling site ...... 15 Figure 7 - Example of depth measurement using Stadia rod ...... 166 Figure 8 - Photo showing use of flow velocity meter ...... 16 Figure 9 - Graph comparing diurnal variation in suspended sediment load of Asulkan Brook between a clear day and storm day ...... 21 Figure 10 - Graph comparing diurnal variation in suspended sediment load of Illecillewaet River between a clear day and storm day ...... 22 Figure 11 - Graph comparing diurnal discharge of Asulkan and Illecillewaet Rivers on the storm day ...... 22 Figure 12 - Hjulstrom curve ...... 24 Figure 13 - The Meeting of the Waters, early afternoon on Sept. 17th. Asulkan Brook on right, Illecillewaet River on left...... 25 Figure 14 – Distances from glacier to Meeting of the Waters, Illecillewaet measured in yellow and Asulkan measured in red, both distances measured using Google Earth ...... 25 Figure 15 - Illecillewaet River during low discharge and high discharge periods. Black arrows point to the same rock in both pictures for reference...... 27

List of Tables

Table 1 - Average of ten filter papers before and after dried in an oven, difference in mass and average loss ...... 18 Table 2 - Sediment data of Illecillewaet River on clear day (Sep. 16) and storm day (Sep. 17) 19 Table 3 - Sediment data of Asulkan Brook on clear day (Sep. 16) and storm day (Sep. 17) ...... 19 Table 4 - Discharge variation throughout the day and comparison between clear and storm days for Illecillewaet River ...... 20 Table 5 - Discharge variation throughout the day and comparison between clear and storm days for Asulkan Brook...... 20

Acknowledgements

We would like to express sincere thanks to Dr. James Gardner and Dr. Daniel Smith for organizing and facilitating this field school. It was an amazing opportunity and the experience has greatly added to our skills and knowledge already gained in the classroom. A thank you to

Jodi Axelson, our T.A., as well; her help and insights to our project were invaluable. We would also like to thank the graduate students that came on the trip; they all helped us in many ways.

And another special thank you to Dr. James Gardner for allowing us use of his photographs in this report.

Introduction

Around the globe, glaciers show an overall reduction in ice extent, mainly due to climate change (Barry, 2006). One of several outputs of glacial melting is meltwater, which influences the discharge of streams that flow from glaciers; as intensity of solar radiation and temperature fluctuate during the day, the amount of meltwater originating from glaciers changes. In addition, precipitation adds to stream discharge and depending on storm intensity such events can suppress the dramatic discharge variation (low discharge in morning and high discharge in the afternoon) that is apparent on clear days. As stream discharge increases, the stream‟s competence, which is determined by the maximum size of sediment a stream can entrain, also increases; however, this process is supply limited, so if unconsolidated sediment is unavailable, a stream will not be able to erode and transport any grains.

Purpose and Objectives

There were four objectives of this research project, focusing on the suspended sediment load and discharge of two glacial streams: Illecillewaet River and Asulkan Brook. (1) To determine the change in suspended sediment over the course of the day for both streams. (2) To determine differences in suspended sediment load between sunny, clear weather and cloudy, rainy weather. (3) To determine differences in suspended sediment load between both glacial streams over the course of the day and between the clear and storm days. (4) To determine the differences in discharge between the two streams over the course of the day.

Research Context and Significance

The type of research completed in this project can be used for many applications.

Determining suspended sediment load from both glacial streams could be useful in predicting sediment origin, as well as calculating sediment contributions from both glacial streams to downstream areas. Tracking the stream discharge over the course of the day can also aid in stream planning. The data could be useful for deciding on distances between walking paths and the stream bank as well as bridge height above the water to prevent path flooding and bridge washouts. Discharge data would also be useful in other areas in water resources applications, such as determining power output from a hydroelectric dam. The discharge data for glacial streams is directly related to the amount of glacial melt, so it would be a useful factor in determining glacial mass balance.

Description of Study Area

Physical Geography of Glacier National Park and Surrounding Region

The location of this project was Glacier

National Park in British Columbia, Canada, shown in

Figure 1. Glacier National Park is located within the

Selkirk Mountains, a part of the Columbia Mountain

Range. The Selkirk Mountains are over 480 km long and roughly 650 km inland from the Pacific coast

(Wheeler and Parker, 1912). The terrain of the

Selkirk Mountains, in and around the Rogers Pass Figure 1 – Map of British Columbia with red star showing study location, retrieved area, ranges in elevation from 900m to 3000 m above from http://www.gonorthwest.com/ BC/British-Columbia-Map.htm 6 sea level and includes many sharp peaks and steep, narrow valleys (Slaymaker and McPherson,

1972). The area is densely forested and contains many snowfields and glaciers; approximately

12% of Glacier National Park‟s 500 square miles is glaciated (Downs, 1980).

The immediate study area gets a large amount of precipitation each year due to its location. The park lies at a climatological divide, where two major weather systems meet

(Wheeler and Parker, 1912). The climate is characterized by cold winters and warm summers with hot days (Loukas et al. 2002). The Pacific weather systems (which are very moist and mild) travel inland and combine with the Continental weather systems (which are very dry and cold) to create the massive amounts of precipitation and sustained cold weather of the area (Downs,

1980). Both the Illecillewaet and Asulkan glaciers are more than 500 km inland from the Pacific coast and thus are influenced by maritime air masses as the weather systems move eastward

(Loukas et al., 2002). The Rogers Pass area receives about 1.3 m of rain each year, with 0.8m of it falling in the form of snow (Slaymaker and McPherson, 1972). Due to the large amount of annual precipitation and steep narrow valleys, glaciers are very common in the Selkirk

Mountains (Slaymaker and McPherson, 1972).

The runoff from mountain glaciers follows the seasonal variation in temperature and is dominated by precipitation storage in the cold seasons and ice melt in the warmer seasons

(Knight and Kaser, 2006). During the warmer seasons, a period of significant ice loss will occur; this causes glacial retreat and an increase in meltwater runoff (Knight and Kaser, 2006). Surface melting is the most significant source of glacial meltwater and is generally supplemented by the runoff from melting snow along the valley walls (Hambrey, 1994). The process of surface melting is caused primarily by solar radiation but it is also caused by precipitation in the form of rainfall (Hambrey, 1994).

Sources of stream discharge can be separated into two categories: direct runoff which includes overland flow, interflow and storm flow, and base flow which solely includes groundwater flow (Ritter et al., 2002). The base flow of a river is the only source of water contributing to stream flow during dry times and both direct runoff and base flow contribute to stream flow during storm events. On a storm hydrograph, the peak stream flow usually occurs after precipitation ends and the lag time is defined as the time between the centre of mass of precipitation and the centre of mass of direct runoff (Ritter et al., 2002).

The shape of a storm hydrograph largely depends on the drainage basin area, channel density, basin morphometry or geometry, soil and land use (Ritter et al., 2002). A rapid rising limb leading up to peak discharge can cause more erosion than a gradual rising limb (Konrad et al., 2005). Impervious surfaces can lead to greater rates of direct runoff than surfaces with higher infiltration rates (Shuster et al., 2008). During the recession stage, predominantly characterized by throughflow and groundwater flow, streams usually flows at a slower rate

(gradual) and are rich in dissolved nutrients (Butturini et al., 2005).

Tree canopy in the Illecillewaet catchment represents 90% of the land cover of the drainage basin from 1000 m to 1790 m (Loukas et al. 2002). Tree species such as Engelmann spruce, alpine fir and lodge pole pine are predominate in the higher elevations of the alpine tundra. Outcrops of rock begin covering more land surfaces with increased elevation (40-50% between 1915 m and 2250 m). At highest elevations, land cover is represented by vegetation

(17%), rock and water surfaces (50%) and with glaciers and icefields (33%) covering the rest

(Loukas et al., 2002).

Glaciers are categorized according to morphology (size and environment of formation), thermal properties (temperate or polar) and flow dynamics (active, passive or dead). Both the

Illecillewaet and Asulkan Glaciers are temperate valley glaciers with meltwater streams flowing 8 down into the valley below. Temperate glaciers are those whose ice is at or near the pressure- melting point throughout the ice mass, while the ice of polar glaciers is significantly below this point (Ritter et al., 2002). Thus, temperate glaciers like the Illecillewaet and Asulkan have a higher overall risk of ablation due to loss of mass from meltwater. The observations from the

Vaux family (Vaux and Vaux, 1899) suggest the Illecillewaet and Asulkan glaciers have advanced and retreated over time; therefore both glaciers would therefore be classified as either active or passive glaciers with high or low rates of ice movement from the accumulation to ablation zone.

Glaciers erode bedrock at the base and sides of valleys into which they flow. This can have a large impact on the amount and characteristics of the sediment carried within the glacier ice and its meltwater. Proglacial sediment transport has been used as an indication of the mechanisms of basal sediment evacuation (Gurnell et al., 1992). Glaciers erode underlying bedrock by two main processes: abrasion and quarrying. Abrasion is dependent on the amount of sediment carried along the base of the ice, the characteristic of the underlying bedrock and the weight of the ice compressing the abrading sediment against the bedrock (Ritter et al., 2002). As an example, the Glacière d‟Argentiere in France abrades at a rate of 36 mm per year when the ice is 100m thick and flowing at 250 m per year (Boulton & Hindmarsh, 1987). In contrast, quarrying depends largely on the underlying bedrock, and fractures on the surface (caused by pressure-release, crushing and freeze-thaw conditions) must exist for quarrying to occur (Ritter et al., 2002).

Bedrock underlying the ice will contribute to the sediment load of meltwater, and rock throughout a drainage basin will also add sediment to rivers. Exposed rock is susceptible to physical, chemical and biological weathering processes. Due to weathering, rock fragments are fractured into various sizes. Water enters a river system by direct precipitation, surface runoff, 9 interflow and groundwater flow (Ritter et al., 2002). Depending on a stream‟s competence, rivers can erode, transport and deposit sediment throughout any part of a river.

Illecillewaet and Asulkan Drainage Basins

The monitoring of glacial retreat and advance of the Illecillewaet Glacier has stretched over a century because of the glacier‟s easy accessibility. From 1887 to 1912, the Vaux family surveyed the terminus using photography, noticing the glacier‟s retreat during this time; the terminus retreated 1000 m from 1887 to 1962, advanced 100 m between 1962 and 1984 and now continues to retreat (Loukas et al. 2002). Terminal moraines left from the retreating Illecillewaet

Glacier have been estimated to have formed prior to the 1800s, but many have been destroyed or reworked by avalanches and stream erosion (McCarthy, 2003).

The Illecillewaet River (when combined with the Asulkan Brook) is a tributary of the

Columbia River, eventually draining into the Upper Arrow Lake reservoir. The length of the

Illecillewaet River, from the glacier snout to where the stream combines with the Asulkan Brook, is approximately 3.17 km (measured using Google Earth).

Figure 2 – Sources of meltwater and sediment in the Illecillewaet drainage basin. There are several of the possible sources of sediment and water that would contribute to the Illecillewaet River (Figure 2). Meltwater originates at the Illecillewaet Glacier as well as the

Little Glacier, and from many small tributary rivers that flow down the mountainsides into the

Illecillewaet River. Groundwater contributes significantly to runoff in the autumn and winter, while snowmelt provides most of the flow in spring, and glacier runoff during the summer

(Loukas et al. 2002). The sources of water that combine to create the Illecillewaet River flow through areas of unconsolidated sediment, till, loose rock and forested areas that all have the potential to provide sediment that could be entrained in the stream flow. Unlike the

Illecillewaet Glacier, the Asulkan Glacier has received little documentation and research regarding glacial mass balance, mainly due to its inaccessibility. However, photos of the

Asulkan Glacier‟s drainage basin provide some insight to what the stream‟s sources of sediment and water could be, these are shown in Figure 3 (next page). Water sources for the stream

11 include meltwater from the Asulkan Glacier, along with small tributary streams and several waterfalls that drain the mountains on both sides of the valley. There is a large amount of unconsolidated sediment at the base of the glacier as well as an abundance of small sediments that line the valley floor where the stream flows for most of its length. These are likely the primary sources of sediment for the Asulkan Brook.

Figure 3 – Sources of sediment and meltwater in Asulkan drainage basin.

Sampling Site Descriptions

The samples collected in this project are from both the Illecillewaet River, which originates at the snout of the Illecillewaet Glacier, and from the Asulkan Brook, fed by the

Asulkan Glacier. The two glacial streams merge at “The Meeting of the Waters”, about 1 km from the Illecillewaet Campground. An aerial view of the study area can be seen in Figure 4

(next page).

The Illecillewaet River sampling site (Figure 5, right

side) was approximately 75 metres upstream from where the

streams merge. The stream flow was very high along the

lower portion of the river, and the sampling site was chosen

partially for safety reasons, but also because it offered flow

areas with the least turbulence to provide the most accurate Figure 4 – Aerial view of study area. velocity measurements. The visible portions of the riverbed

were covered with large pebbles and cobbles, and no areas were covered by sand or clay. Dense

overhanging vegetation lined the river beds on both sides with a few trees fallen across the river

breadth. The south bank was predominantly cobbles, sloping gently down to meet the water

while the north bank was nearly vertical and composed mainly of fine sediment which appeared

to be undercut. The side profile (Figure 5, left side) shows the location of maximum and

measured depths, and the aerial diagram shows the locations of major rocks in the study area as

well as the locations where depth measurements and water samples were taken. The black

arrows indicate the direction of flow and the dotted line shows where the stream width was

measured.

Figure 5 – Side profile and aerial diagram (left) and photograph (right) of Illecillewaet sampling site.

The study site of the Asulkan Brook (Figure 6, left side) was approximately 75 metres (in the southeast direction) upriver from where the Illecillewaet River and Asulkan Brook meet.

Like the Illecillewaet site, this site was also chosen for safety reasons and because of less turbulent flow.

The most drastic difference from the Illecillewaet site was the presence of fine sediment.

When the water level was low, portions of the riverbed revealed this muddy layer. Vegetation was also dense along both banks with overhanging branches. Large boulders were settled in various places throughout the river, but due to the sediment laden water, any rocks or cobbles on the river bed were difficult to distinguish.

In Figure 6 (next page, right side), the side profile depicts the horizontal view of the stream where maximum depth and measured depth were recorded, and the aerial diagram shows

14 the location of major rocks in the study area and where depth measurements and water samples were taken. The black arrows indicate the direction of flow and the dotted line shows where the stream width was measured.

Figure 6 – Photograph (left) and side profile and aerial diagram (right) of Asulkan sampling site.

Methodology

Field Methodology

The first day in the field, September 16th, 2009, consisted of collecting water samples and depth measurements from both the Illecillewaet River and Asulkan Brook once per hour. The water samples were collected using 500 mL containers, which were labelled and duct taped shut to prevent leakage. The Asulkan Brook samples were taken every hour on the half hour, and the

Illecillewaet River samples were taken every hour on the hour; allowing time to collect the samples and move between stations. Depth measurements were collected using a four metre

Stadia rod (Figure 7, next page).

Each depth measurement was recorded to the nearest centimetre,

since this is the greatest level of precision the stadia rod would

allow. The width of both streams was also measured at the

beginning and at the end of the day using a measuring tape. A

maximum stream depth was estimated at both sampling locations

at the start of the day; this measurement was not measured using

the stadia rod because it was deemed too dangerous to enter the

Figure 7 – Example of depth stream due to the depth and rapid flow of the water. measurement using Stadia th rod. The second day of data collection, September 17 , 2009, also involved collection of water samples and depth measurements every hour for both streams,

according to the same protocol as the first day of data collection. Data regarding flow velocity

was also collected using a pygmy metre (Figure 8).

The digital display of the pygmy metre displayed flow

velocity in metres per second (m/s), and updated the

reading every four seconds. Three flow velocities

were recorded for each measurement and then

averaged, since the velocity of flow fluctuated slightly

each time the display updated. Figure 8 – Example of velocity measurement using pymgy metre. Laboratory Methodology

The fundamentals of the following sediment analysis were adapted from Haritashya et al.

(2006) because the article offered the best representation of our data and our study purpose.

First, thirty empty filter papers were labelled with the stream name, date and time sample

was collected. The filter paper used was Whatman folded grade no. 2V with a mesh size of 8.0

μm (0.008 mm). This size was chosen because it was available to us, but only retained grains larger than fine silt (Lewis & McConchie, 1994). Furthermore, the filter paper was a folded variety rather than flat and so allowed the lowest possibility of sediment being dislodged or blown off the filter paper during handling.

Each filter paper was weighed using the Precisa XT 1200C scale with an error of ±0.01 grams. Using a 500 mL flask and large funnel that enclosed the whole filter, 500 mL of sample water was measured with a 500 mL beaker (error of ±0.5 mL) and filtered through to the flask underneath. Once filtered, the filter paper was dried in a Fisher Scientific oven at 110oC for approximately half an hour, or until dry to the touch. Using the same scale, the dried filter paper and sediment were reweighed. The mass of sediment was calculated using formula [1] below:

mass of sediment = sediment and filter paper − filter paper [1]

However, some sediment samples equalled a negative mass (ie. filter and sediment combined weighed less after filtration than before). This outcome was not possible, primarily because the filters visually contained sediment. This suggested the filter papers must have lost mass during the saturation and drying process. To account for the error of the filter paper mass, ten new filter papers were weighed, saturated, dried and weighed again. The average loss of mass of each filter paper was determined using formula [2] below:

mass lost = average mass before − average mass after [2]

This difference was added to all sediment samples for both the Illecillewaet and Asulkan so any negative sediment masses changed to positive masses, relative to the uncorrected mass.

From the data collected in the field and measured in the laboratory, variations in suspended sediment load and stream discharge could be graphed using Microsoft Excel.

Data and Results

Table 1 (below) shows the mass of ten filter papers before and after being saturated and oven dried. It also shows the individual loss of mass for each filter and the average loss for all ten. The average difference between the filter before and after being saturated and dried in the oven was a loss of 0.33 grams. Tables 2 and 3 (next page) show the analysis of data regarding suspended sediment load for both glacial streams. The dry filter weight and weight of filter and sediment (oven dried) are shown along with the corrected mass of the overall amount of suspended sediment.

Table 1 – Average of ten filter papers before and after dried in an oven, difference in mass and average loss.

Weight (± 0.01 g)

Filter Dried Filter Difference (g) Paper (g) Paper (g) 7.63 7.57 0.06 8.09 7.34 0.75 7.62 7.27 0.35 8.00 7.73 0.27 7.90 7.28 0.62 7.72 7.64 0.08 7.97 7.36 0.61 7.71 7.68 0.03 7.66 7.35 0.31 7.68 7.42 0.26 7.80 7.47 0.33 Average Loss = 0.33

Table 2 – Sediment data of Illecillewaet River on clear day (Sep. 16) and storm day (Sep. 17).

Clear day (Sep. 16) Storm day (Sep. 17) Weight (± 0.01 g) Weight (± 0.01 g)

Filter and Filter and Time Filter Sediment Corrected Filter Sediment Corrected Sediment Sediment 10:00 7.62 7.73 0.11 0.44 7.69 7.71 0.02 0.35 11:00 8.27 8.09 -0.18 0.15 8.14 8.25 0.11 0.44 12:00 7.65 7.46 -0.19 0.14 7.79 7.69 -0.10 0.23 13:00 8.18 8.05 -0.13 0.20 8.20 7.98 -0.22 0.11 14:00 7.74 7.49 -0.25 0.08 7.60 7.96 0.36 0.69 15:00 7.65 7.42 -0.23 0.10 7.67 7.74 0.07 0.40 16:00 8.21 8.12 -0.09 0.24 8.24 8.55 0.31 0.64 17:00 7.62 7.72 0.10 0.43

Table 3 – Sediment data of Asulkan Brook on clear day (Sep. 16) and storm day (Sep. 17).

Clear day (Sep. 16) Storm day (Sep. 17)

Weight (± 0.01 g) Weight (± 0.01 g)

Filter and Filter and Time Filter Sediment Corrected Filter Sediment Corrected Sediment Sediment 9:30 7.75 8.04 0.29 0.62

10:30 8.29 8.24 -0.05 0.28 7.76 8.16 0.40 0.73 11:30 7.61 7.80 0.19 0.52 7.72 8.30 0.58 0.91 12:30 7.67 7.80 0.13 0.46 7.96 8.42 0.46 0.79 13:30 7.52 8.31 0.79 1.12 7.82 9.28 1.46 1.79 14:30 8.08 8.14 0.06 0.39 7.69 9.36 1.67 2.00 15:30 7.57 7.85 0.28 0.61 7.72 8.58 0.86 1.19 16:30 7.66 7.85 0.19 0.52 8.04 8.26 0.22 0.55

The following tables (Table 4 and 5) contain depth and flow velocity data for both the

Illecillewaet River and the Asulkan Brook on September 16th and September 17th, 2009. The maximum depth was estimated once and the difference in measured depth applied to the first measurement to ascertain the maximum depth changes throughout the day. The three velocity

measurements were averaged to get one velocity measurement for that particular time of day and

then used to calculate the stream discharge.

The greatest discharge for the Illecillewaet was at 13:00 and equalled 9.56 m3/s (Table 1)

and greatest discharge for the Asulkan was at 13:30 and equalled 12.52 m3/s (Table 2).

Table 4 – Discharge variation throughout the day and comparison between clear and storm days for Illecillewaet River.

Clear day (Sep.16) Storm day (Sep. 17) Max Max Average Time Depth Depth (m) Discharge Depth Depth Velocity (m/s) velocity (24 hr) (m) measured (m3/s) (m) (m) (m/s) 10:00 0.30 0.75 0.62 1.07 1.41 1.45 1.38 1.41 7.86 11:00 0.45 0.90 0.62 1.07 0.91 0.80 0.98 0.90 4.99 12:00 0.50 0.95 0.60 1.05 1.41 1.63 1.78 1.61 8.74 13:00 0.60 1.05 0.90 1.35 1.38 1.34 1.20 1.31 9.56 14:00 0.65 1.10 0.80 1.25 1.34 1.38 1.31 1.34 8.98 15:00 0.68 1.13 0.75 1.20 1.12 1.23 1.38 1.24 7.93 16:00 0.70 1.15 0.70 1.15 1.12 1.38 1.45 1.32 7.98 17:00 0.65 1.10 1.16 0.98 1.12 1.09 6.25

Table 5 – Discharge variation throughout the day and comparison between clear and storm days for Asulkan Brook.

Clear day (Sep.16) Storm day (Sep. 17) Max Max Average Time Depth Depth (m) Discharge Depth Depth Velocity (m/s) velocity (24 hr) (m) measured (m3/s) (m) (m) (m/s) 9:30 0.85 1.50 0.87 0.89 1.02 0.93 5.94

10:30 0.45 1.10 0.90 1.55 0.94 1.05 0.94 0.98 6.52 11:30 0.52 1.17 0.95 1.60 1.12 1.16 1.2 1.16 8.05 12:30 0.60 1.25 1.05 1.70 1.38 1.27 1.32 1.32 9.88 13:30 0.70 1.35 1.30 1.95 1.31 1.41 1.56 1.43 12.52 14:30 0.83 1.48 1.20 1.85 1.05 1.02 0.98 1.02 8.39 15:30 0.78 1.43 1.15 1.80 1.2 1.12 1.2 1.17 9.37 16:30 0.75 1.40 1.00 1.65 1.16 1.3 1.34 1.27 9.12

Figures 9 and 10 show graphs of the variations in suspended sediment over the course of the day on both September 16th (clear day) and September 17th (storm day), 2009. Both graphs represent bell shaped curves with highest sediment concentration at 13:30 on the clear day and

15:30 on the storm day. There is more fluctuation (more intermittent peaks and troughs) on the clear day than the storm day.

0.80

0.70

0.60

0.50

0.40 Clear day

Sediment (g) Sediment 0.30 Storm day

0.20

0.10

0.00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 Time (24 hr)

Figure 9 – Graph comparing variation in suspended sediment load of Illecillewaet River between a clear day and storm day.

0.80

0.70

0.60

0.50

0.40 Clear day

Sediment (g) Sediment 0.30 Storm day

0.20

0.10

0.00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 Time (24 hr)

Figure 10 – Graph comparing variation in suspended sediment load of Asulkan Brook between a clear day and storm day.

14.00

12.00

10.00 /s) 3 Asulkan 8.00

Illecillewaet

6.00 Discharge (m Discharge 4.00

2.00

0.00 8:24 9:36 10:48 12:00 13:12 14:24 15:36 16:48 18:00

Time (24 hr)

Figure 11 – Storm hydrograph of Illecillewaet River and Asulkan Brook.

Figure 11 shows the variation in stream discharge over the course of the storm day, since that was the only day that velocity of flow was measured. The discharge of the Asulkan Brook was consistently higher than the Illecillewaet River, except for one sample early in the day.

Discussion

Comparison of Sediment Load during Clear Weather and Storm Weather

Analysis of suspended sediment load for both streams demonstrates that on the first day of data collection (clear, sunny weather) the amount of entrained sediment peaked sooner than on the second day (rainy, overcast). The second day of data collection had a suspended sediment peak later in the day which was also higher than the peak on the first day. On the rainy, overcast day the suspended sediment values were sometimes more than three times higher than at the same time on the first day of data collection. Maximum flow events are mainly produced by rainfall runoff, which significantly contributes to the total runoff, even during rain-on-snow events (Loukas et al., 2002). The suspended sediment peak on the second day occurred at the end of the period of rainfall for the Illecillewaet River (14:00) and slightly after the rainfall stopped for the Asulkan Brook (15:30). This could be due to the lag time between rainfall occurring and actually draining into the glacial stream. The Illecillewaet River would have a shorter time lag because it is a shorter stream than the Asulkan Brook. Any rainfall would drain from the entire valley, increasing discharge for both streams and therefore entraining more sediment. During a period of sporadic rain events, the normal meltwater curve still applies, but the times of day where rain occurs must also be taken into account since the stream discharge will be higher during or shortly after the rain, since in extremely steep watersheds with high relief, a quick runoff response time is expected (Onda et al., 2006).

Figure 12 - Hjulstrom curve showing relationships between particle size and flow velocity, retrieved from http://www.utexas.edu/depts/grg/hudson/grg338c/schedule/3_erosion_sed/ erosion_sed_images/hjulstrom_curve.jpg.

The stream discharge increases linearly with the amount of rainfall (Singh and Kumar,

1997). The direct relationship between rainfall and stream discharge causes an increase in erosion due to the increase in velocity. The stream flow velocity for the Illecillewaet River ranged from 0.9 to 1.6 m/s while the velocity for the Asulkan Brook ranged from 0.93 to 1.43 m/s. According to the Hjulstrom curve shown in Figure 12, the maximum sediment size that would have been suspended in flow during the time period of the experiment was approximately

0.2 mm or sand-sized particles. Though the Illecillewaet River had the highest flow velocity, it did not have the highest discharge. The Asulkan Brook had greater (estimated) depths which resulted in a larger overall discharge, which could be one of the factors leading to the Asulkan

Brook having a higher suspended sediment load.

Differences/Similarities in Suspended Sediment Load of Illecillewaet River and Asulkan Brook

The Asulkan Brook carries much more suspended sediment than the Illecillewaet

River, this can be seen in Figure 13 which shows the point at which the two streams combine. The maximum weight of suspended sediment carried in the Illecillewaet River was

0.69 grams on the storm day, while the Figure 13 - The Meeting of the Waters, early Asulkan Brook had a maximum suspended afternoon on Sept. 17th. Asulkan Brook on right, Illecillewaet River on left. sediment load of 2.00 grams. Field observations occurred at both glacier tongues, and the meltwater appeared to consist of very fine suspended sediments. However, the concentration of suspended sediments was very low and the meltwater appeared to be very clean as it exited the glacier. With little sediment originating from the glacial Figure 14 – Distances from glacier to Meeting of the Waters, Illecillewaet measured in yellow meltwater, sediment from the drainage basin and Asulkan measured in red, both distances measured using Google Earth. must be contributing to the majority of suspended sediment. The Illecillewaet River has a distance of 3.17 km from the glacier to the meeting of the two streams, but the Asulkan has 5.54 km between the glacier and where the streams meet, both distances shown in Figure 14. This difference in stream length allows the

Asulkan Brook much more opportunity to entrain sediments from the sides and bottom of the streambed. The first kilometre of the Illecillewaet River flows over primarily bedrock and large boulders, and the last 2.15 km flows over a sediment rich valley bottom where it may erode sediments from the sides and bottom of the streambed. However, the Asulkan Brook travels over the sediment filled valley bottom for 4.15 km, which allows much more opportunity for increasing the amount of suspended sediment in the flow. The previously glaciated areas directly in front of both glaciers are quite different. The Illecillewaet has a large area of scoured bedrock while the area directly in front of the Asulkan has some scoured rock, but also many loose sediments and small boulders. The glacial meltwater from the Asulkan immediately flows over unconsolidated sediments and till deposits left from the glacial retreat, and therefore has the opportunity to begin picking up sediment; the Illecillewaet does not flow over much sediment until it reaches the valley bottom. Another factor that would cause the Illecillewaet River to have less suspended sediment than the Asulkan Brook is that much of the Illecillewaet‟s water is sourced from groundwater that seeps up into the stream from below, which would dilute the concentration of suspended sediment in the river (Ritter et al., 2002). There are also many small, slow-moving tributaries that flow into the Illecillewaet River which would further dilute the concentration of suspended sediment.

Differences in Suspended Sediment Load throughout the Day

A glacier melts at different rates according to the time of day as well as different times of the year (Hasnain and Chauhan, 1993). Seasonal and daily variations in the climate affect glacial melt, which affects stream flow, and therefore suspended sediment load (Hasnain and Chauhan,

1993). This is related to the amount of received solar radiation, or insolation, which is highest during the summer months, May to September and also during midday (Haritashya et al., 2006).

On a clear, sunny day, like the first day of data collection, the sediment load is expected to increase from the beginning of the day to early or mid-afternoon then begin to decrease, forming a bell-shaped curve. This bell-shaped curve applies on rainy, cloudy days as well, though the periods of rainfall are should also be taken into account. The sediment load should increase soon after the periods of rainfall due to the lag time between the actual rainfall and the water reaching the stream. Once the rain water reaches the stream it will increase discharge, which is closely correlated with suspended sediment load (Bhutiyani, 2000).

Analysis of Discharge of Illecillewaet River and Asulkan Brook

The Illecillewaet and Asulkan Rivers both showed overall greater discharge on the storm day, due to direct precipitation and runoff. Discharge measurements were not collected on the clear day, so it is only possible to visually compare the rivers between these two days which makes it difficult to draw quantitative conclusions. In Figure 15, the water level of the

Illecillewaet River was significantly lower on the clear day than on the storm day. This observation suggests precipitation, by means of direct, and surface and subsurface runoff, has a significant contribution to increasing discharge.

Figure 15 - Illecillewaet River during low discharge and high discharge periods. Black arrows point to the same rock in both pictures for reference.

If the discharge measurement taken from the Illecillewaet River at 11:00 was eliminated

(this measurement could have been an anomaly in the data because discharge decreased then increased significantly over a short period of time) the storm hydrograph (Figure 11) would display a gradual rising limb consisting of a change of 1.7 m3/s over two hours leading up to peak discharge of 9.56 m3/s. This gradual rising limb suggests infiltration is higher than surface runoff.

In contrast, the Asulkan Brook displayed a more rapid rising limb (a change of 6.58 m3/s over four hours) and greater overall discharge (12.52 m3/s). Therefore, the higher discharge of the Asulkan could be correlated to greater suspended sediment load due to erosion and transport abilities of the stream (Konrad et al., 2005). Given the Illecillewaet drainage basin contributes to the river largely from groundwater sources, this would suggest more infiltration occurred for the

Illecillewaet and less surface runoff (Shuster et al., 2008). The increased discharge and suspended sediment load for the Asulkan Brook could be attributed to higher surface runoff and more impervious soil than the Illecillewaet. However, this proposed notion is only representative for the time period of the measurements. If the soil of the Asulkan basin were more impervious, the Asulkan may show a more gradual, but still relatively steep, recessional limb as well, which could not be revealed on the storm hydrograph due to temporal limitations.

Limitations of Experiment/Recommendations for Further Research

The first limitation in the field was the fact that only a maximum depth in the median of the river and another depth near the bank were recorded to find discharge values. Given stream depth is variant and generally deepest in the centre, these two depth measurements created only a basic profile of the stream bed and may have not represented the most accurate depth profile and thus discharge has some amount of error. However, the river was flowing very swiftly,

28 especially on the storm day, that accurately measuring equally spaced depths along the width of the river would have been a dangerous endeavor. In addition to depth measurements, velocity measurements were only taken from one place near the bank of each river. Although velocity was collected in areas of lowest turbulence, this may be a source of error because velocity is greatest in the middle of the river and near the surface and lowest near the river banks (Ritter et al., 2002). So with both more velocity and depth measurements, discharge could be more representative of the stream environment.

A second limitation in the field was the lack of precipitation data. This data would have added to the interpretation of the storm hydrograph. It would have also provided a lag time between peak precipitation and peak discharge, further reinforcing the possibility of whether the drainage basins may have some degree of impervious soil.

There were a few limitations to the sediment analysis in the laboratory. First, the mesh size only retained particles with a diameter of 0.008 mm or greater. According to the Udden-

Wentworth grade scale, this includes all particles categorized at „fine silt‟ or larger and not „very fine silt‟ or clays (Lewis & McConchie, 1994). Second, there may be a source of error with regards to the filter paper used because empty filter papers loss mass during the process of saturation and drying. This loss of mass was identified and accounted for; however, there may still be minimal error. Perhaps testing a filter paper before analysis might have resulted in the use of a different filtering method, such as using a metal mesh variety.

Also, the time allotted for collecting the field data was limited. This type of project would benefit from long term observations in order to get a better perspective on how suspended sediment and discharge change over a longer period of time; for example, data collection throughout the ablation season would allow comparison of daily as well as seasonal sediment and discharge variations (Kumar, et al., 2002). It would also be valuable to have multiple 29 monitoring stations at various intervals up the streambeds to gather more specific information as to where the tributary water sources combine with the glacial meltwater, and further determine where the majority of suspended sediment originated. This research project would be useful as a pilot study, but for more accurate and representative data a much longer data collection period would be recommended.

Conclusion

The amount of suspended sediment in both the Illecillewaet River and Asulkan Brook varied over the course of the day. This was due to factors relating to incoming solar radiation, temperature and precipitation. These factors influence the amount of water in the streams which changes the erosion ability of the stream and results in suspended sediment variations. This suggests that suspended sediment load is closely related to stream discharge. The material underlying the stream also has an impact on the amount of suspended sediment. Cobbles and pebbles provide less sediment that can be entrained within the stream flow, small sediments are much smaller and more likely to be eroded and carried within the flow. Local weather also has an effect on the amount of suspended sediment in the streams. There is a great deal of variation in suspended sediment amounts between the clear and storm day. This suggests precipitation has a large impact on surface runoff into the valley streams.

The storm hydrograph showed discharge variations throughout the day in the form of a bell-shaped curve. However, the peak discharge for the Asulkan Brook was higher than the

Illecillewaet River, suggest physical factors in the drainage basin were contributing to this difference. Precipitation affected both rivers; however, the difference in unconsolidated

30 sediment and permeable soil of the two basins may have had an impact on the amount and rate that water flows as surface runoff and infiltrates the stream as baseflow or groundwater flow.

Overall there are a plethora of factors that result in changes in suspended sediment load and discharge of alpine glacial streams.

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