4. Data Analysis
In order to determine whether the construction of E.B Campbell Dam on the Saskatchewan River has affected the geomorphology of the delta, analysis was done on the datasets provided by Dr. Tim Jardine.
Following are the data sets that were used to perform data interpretation and analysis:
a) Daily mean discharge values (m3/sec), turbidity recorded at 15 minute intervals from 1st of June to 19th of July, and spot measurements of Total Suspended Solids (TSS, mg/L) at DS4 (Big Eddy Camp) in the year 2014.
b) Daily mean discharge values (m3/sec), turbidity recorded at 15 minute intervals from 10th of June to 1st of November at DS4 (Big Eddy Camp) in the year 2017.
c) Daily mean discharge values (m3/sec) and spot measurements of TSS (mg/L) at three sites (DS1, DS2, DS3) downstream of the E.B Campbell Dam in the ice free season of year 2014.
d) Daily mean discharge values (m3/sec) and spot measurements of TSS (mg/L) at one site upstream of the E.B Campbell Dam in the year 2014.
4.1 Daily Profiles at Big Eddy Camp – 2014 and 2017
Seasonal daily profiles for year 2014 and 2017 were generated from monitored daily mean discharge and mean estimated TSS. TSS was estimated from monitored turbidity using following formula from Alberta Transportation’s turbidity specification:
(1) TSS (mg/L) = 3.1642 X Turbidity (FNU)
Load was calculated from:
(2) Load (mg/s) = Mean Discharge (m3/s) x TSS (mg/L*1000)
Figure 3: Plot of Load v/S Time for the Big Eddy Camp for the year 2014
Figure 4: Plot of Load v/S Time for the Big Eddy Camp for the year 2017
The seasonal daily profile peaked in early June and early July for both the years. The reason for unstable seasonal load in 2014 and 2017 could be due to the fluctuating river flow generated by the dam. Apart from this, it is interesting to note that the mean load for 2017 is decreasing during the year’s ice free season whereas for the year 2014, the mean load is steadily increasing. However, the difference in trend could be because of shorter period of record in 2014 as compared to the period of record in 2017.
4.2 Dam Downstream v/s Dam Upstream 2014
The data were not available for the whole year of 2014 but only a short seasonal period. From this data, daily mass in tonnes per day was calculated using the following formula:
(3) Daily mass (tonnes/day) = Discharge X TSS X 3600 (seconds/hour) X 24 (hours/day)
In order to analyze if the sediment concentration has changed due to dam construction, the 2014 dam downstream seasonal load was compared with the 1988 dam downstream seasonal load using sites DS1, DS2, and DS3. The 1988 seasonal load data extracted from the study by Ashmore and Day (1988) and seasonal load of year 2014 was calculated by assuming that most of the sediment transport happens in the ice-free season, which was further assumed to last from May until November (7 months or 210 days). Therefore, the total mass was multiplied by 210 and then divided by the number of days of measurement to get a total seasonal load for year 2014.
Table 1: Downstream Calculation for year 2014 | Site | Location | Date | Discharge (m3/sec) | TSS (mg/L) | Mean Load(g/s) | Daily Mass (tonnes per day | |:—-:|:———————:|:———:|:—————————–:|:———-:|:—————-:|:————————–:| | DS1 | Below EB Campbell Dam | 22-Jul-14 | 296 | 4 | 1228 | 106 | | DS1 | Below EB Campbell Dam | 22-Aug-14 | 408 | 4 | 1636 | 141 | | DS1 | Below EB Campbell Dam | 20-Sep-14 | 236 | 4 | 871 | 75 | | DS2 | Below EB Campbell Dam | 30-May-14 | 1630 | 17 | 27873 | 2408 | | DS2 | Below EB Campbell Dam | 20-Jun-14 | 1280 | 5 | 5914 | 511 | | DS2 | Below EB Campbell Dam | 20-Jul-14 | 781 | 10 | 7459 | 644 | | DS2 | Below EB Campbell Dam | 20-Aug-14 | 461 | 5 | 2102 | 182 | | DS2 | Below EB Campbell Dam | 20-Sep-14 | 236 | 3 | 715 | 62 | | DS3 | Below EB Campbell Dam | 1-Jun-14 | 1660 | 8 | 12550 | 1084 | | DS3 | Below EB Campbell Dam | 23-Jun-14 | 1560 | 4 | 5647 | 488 | | DS3 | Below EB Campbell Dam | 20-Jun-14 | 781 | 7 | 5420 | 468 | | DS3 | Below EB Campbell Dam | 20-Aug-14 | 461 | 13 | 5901 | 510 | | DS3 | Below EB Campbell Dam | 20-Sep-14 | 236 | 1 | 210 | 18 | | | | | | | Total Daily Mass | 6698 tons per day | | | | | | | Seasonal Load | 108202 tons |
Table 2: Upstream Calculation for year 2014 | Site | Code | Location | Date | Discharge (m3/sec) | TSS (mg/L) | Mean Load(g/s) | Daily Mass (tonnes per day | |:——:|——|:———————:|:———:|:—————————–:|:———-:|:—————-:|:————————–:| | Wapiti | US1 | Below EB Campbell Dam | 28-May-14 | 1560 | 84 | 130759 | 11298 | | Wapiti | US1 | Below EB Campbell Dam | 18-Jun-14 | 1300 | 111 | 144092 | 12450 | | Wapiti | US1 | Below EB Campbell Dam | 16-Jul-14 | 1050 | 32 | 33285 | 2876 | | Wapiti | US1 | Below EB Campbell Dam | 22-Aug-14 | 408 | 29 | 11632 | 1005 | | Wapiti | US1 | Below EB Campbell Dam | 19-Sep-14 | 365 | 30 | 10826 | 935 | | | | | | | | Total Daily Mass | 28,563 tons per day | | | | | | | | Seasonal Load | 1,199,660 tons |
4.3 Sediment Loss for Year 2014
The sediment loss was determined by computing the difference between downstream seasonal load and upstream seasonal load. The difference is 1091485 tons which shows that that there was significant sediment loss in year 2014 due to ongoing loss of sediments in the reservoir. This further supports the claim made by many researchers that construction of dams has negative effects on downstream geomorphology (Smith et al. 2016).
4.4 Estimated V/s Monitored Readings
Data analysis was performed to check the accuracy of spot determinations by comparing them to continuously monitored readings. The data was for Big Eddy Camp and TSS and mean discharge was spot calculated by Dr. Tim Jardine for three different days in the year 2014 (Table 3). Mean load and daily mass were then calculated and compared to that of monitored readings of the same day by the sensors present in the same site (Figure 3).
Table 3: Estimated/Calculated Readings
| Site | Location | Date | Discharge (m3/sec) | TSS (mg/L) | Mean Load(g/s) | Daily Mass (tonnes per day |
|---|---|---|---|---|---|---|
| Big Eddy Camp | Sask Delta | 2-Jun-14 | 1480 | 75 | 110946 | 9586 |
| Big Eddy Camp | Sask Delta | 22-Jun-14 | 1470 | 36 | 52861 | 4567 |
| Big Eddy Camp | Sask Delta | 18-Jul-14 | 823 | 68 | 56070 | 4844 |
Table 4: Monitored Readings
| Site | Location | Date | Discharge (m3/sec) | TSS (mg/L) | Mean Load(g/s) | Daily Mass (tonnes per day |
|---|---|---|---|---|---|---|
| Big Eddy Camp | Sask Delta | 2-Jun-14 | 1481 | 22 | 32903 | 2843 |
| Big Eddy Camp | Sask Delta | 22-Jun-14 | 1460 | 13 | 19457 | 1681 |
| Big Eddy Camp | Sask Delta | 18-Jul-14 | 823 | 36 | 29953 | 2588 |
Figure 5: Comparison between monitored load and estimated load for Big Eddy Camp for three dates in 2014
There was poor agreement between monitored and estimated readings as TSS was over estimated which resulted into estimated mean load to be greater than monitored mean load (Figure 5). Also, the error was not constant for three different dates which shows that there is no specific error trend which could help in estimating future readings without monitoring.
4.5 1988 and 2014 Sediment Change
To analyse the multi-decadal change in sediment concentration in the downstream of the dam, 1988 dam downstream seasonal load was compared to 2014 dam downstream data. Ashmore and Day (1988) calculated the seasonal load as 0.092 * 106 tons and seasonal load at the downstream of the E.B. Campbell Dam in 2014 was 0.108 * 106 tons. The difference in estimated seasonal load between 2014 and 1988 was (0.108 - 0.092) *106 tonnes = 16,000 tonnes.
This difference can be interpreted that even though 16000 tons seems like a large number, 108000 tons is not really different than 92000 tons, considering how much error there is in day-day measurements, flow conditions, etc. A difference of 16000 tons is small compared with the upstream and downstream seasonal load, which is more than 1 million tons (Table 2).
Keeping these numbers in perspective, it can be said that a similar estimation for load can be achieved with a small sample size as compared to a much larger dataset done 30 years ago and it also suggests that overall sediment load downstream of EB Campbell Dam has not changed much over time.