Runoff 1999 - Shuswap River


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Runoff Report 1999..... Shuswap River

2. Data Stations and Measurements

The Shuswap River allows the most detailed analysis in this report. A total of 4 gauges are recording stream levels between Sugar Lake and Shuswap Lake. For the Sugar Lake itself BC Hydro provides additional data about the lake's inflow and levels. This allows the tracing of the water during the runoff as well as some information about the source of the water. One more gauge in the Mabel Lake could make it almost perfect!

Table 2.1 below lists all gauges and data sources.

Location	Source	Data Provided by
Sugar Lake Inflow	Calculated	BC Hydro
Sugar Lake (Level)	Gauge	BC Hydro
Sugar Lake Outflow	Gauge	Environment Canada
Wilsey Dam	Gauge	Environment Canada
Bessette Creek	Gauge	Environment Canada
Enderby	Gauge	Environment Canada

The Sugar Lake is the water reservoir for the Peers Dam and its outflow is regulated by BC Hydro as described earlier. Therefore, the lake inflow has no relation to the lake outflow. For the runoff evaluations the Sugar Lake inflow is only secondary as long as the lake is below its free spill level. After reaching the spill level the inflow adds to the controlled outflow, discharging far more water than produced by the inflow. This can lead to a sudden and drastic flow increase of the Shuswap River with the high potential for flooding downstream. The free spill level of the Sugar Lake for 1999 varied between 600m ASL and 601.72m ASL (ASL = above sea level).

Before I get to the different sections and their contributions to the Shuswap River here some general data for the 1999 runoff.

Table 2.2: Total Water Flow for 1999 (01/01/99 to 31/10/00)

Location	Total Water Flow (m³)
Sugar Lake Inflow	1,480,844,160
Sugar Lake Outflow	1,428,883,200
Section 2 Inflow	476,919,360
Wilsey Dam	1,905,802,560
Bessette Creek Inflow	119,798,266
Other Inflow (Section 3 and 4 )	1,532,999,174
Enderby (as Shuswap Lake inflow)	3,558,600,000

This table shows a larger inflow than outflow what can be explained by the storage of water in the lake. As I will show later in more detail the lowest lake level was 594.70m ASL at April 12, 1999, the highest close to the spill level of 601.83m ASL (September 09,1999). This calculates the storage of the equivalent of 7.13m level difference.

Let me proof that with a simple calculation:

Lake area of 21.3km² (=21,300,000m²) * 7.13m level difference = 151,869,000m³

Considering the fact that the lake inflow is also calculated, the lake surface area is getting smaller with a decreased level and that the level had different periods of ups and downs, the result comes surprisingly close to the difference.

Having the lake inflow validated, the table 2.2 illustrates the importance of the lake as controlled buffer zone:

Almost 42% of the total water recorded at Enderby (Shuswap Lake inflow) came
from the area above the Sugar Lake.

Without the controlled storage of the lake this huge amount of water would have been pushed downstream in a relative short period of time. The result would have been not only massive flooding along the stream but also probably causing the flood of the century around the lake and far into the South Thompson River, not to mention the effect on Enderby.

During the runoff the Sugar Lake level was for 35 days at or slightly above the free spill level.

Over 35% of the recorded Shuswap Lake inflow is caused by the Shuswap River.

Table 2.3 shows the percentage of the flow data in table 2.2.

Location	% of Total Discharge
Sugar Lake Inflow	41.6%
Sugar Lake Outflow	40.2%
Section 2 Inflow	+13.4%
Wilsey Dam	=53.6%
Bessette Creek Inflow	+3.4%
Other Inflow (Section 3 and 4 )	+43.0%
Enderby (as Shuswap Lake inflow)	=100.0%

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