Libby VARQ Flood Control Impacts on Kootenay River Dikes Hamish - - PowerPoint PPT Presentation

C R E S TO N VAL L E Y, B R I T I S H C O L U M B I A

Libby VARQ Flood Control Impacts on Kootenay River Dikes

Hamish Weatherly, Hydrologist

Creston Valley Dikes

2

3

4

Dam Construction

5

• Increased control of flooding on the Kootenay River and

Kootenay Lake was achieved through the construction of three dams

– Corra Linn Dam (at Nelson) – 1932 – Duncan Dam – 1967 – Libby Dam – 1973

• Libby Dam has had a major impact on Kootenay River

and Kootenay Lake water levels

– it regulates 70% of the flow at the US-Canada border

Porthill, Idaho

6

200 400 600 800 1000 1200 1400 1600 1800 2000

Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01 Aug-01 Sep-01 Oct-01 Nov-01 Dec-01

Average Discharge (m3/s)

pre-Libby Dam (1929-1971) post-Libby Dam (1973-2011)

Kootenay River Peak Flows

7

500 1000 1500 2000 2500 3000 3500 4000

1929 1933 1937 1941 1945 1949 1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009

Peak Annual Discharge (m3/s) Year

post-Libby Dam

Kootenay Lake

8

529 530 531 532 533 534 535

Jan-1 Feb-1 Mar-1 Apr-1 May-1 Jun-1 Jul-1 Aug-1 Sep-1 Oct-1 Nov-1 Dec-1

Average Lake Level (m)

pre-Libby Dam (1938-1971) post-Libby Dam (1973-2010)

Kootenay River

9

520 522 524 526 528 530 532 534 536 538 540 0.0 1.0 2.0 3.0 4.0 5.0 6.0

Elevation (m) Distance (km)

2-year flood level 200-year flood level ground elevation no topographic data Reclamation Farm Diking District

Libby Dam Operation

• 1973 to 1992

– Standard Flood Control regime with operation of the dam driven almost exclusively by flood control and power

• 1993 to 2002

– Standard FC continues and flood control remains a top priority. However, operations for downstream fisheries has a higher priority than power operations. Ramping rate restrictions were also adopted in the late 1990’s.

• 2003 – present

– Variable Flood Control is adopted. With this regime there are higher flood control curves for most water conditions, although flood control remains a top priority.

10

Load Following

• Prior to the late 1990’s, Libby Dam was operated with

the practice of load following

– Refers to fluctuations in dam releases that correspond to changes in power demand – Load following was typically employed during the late fall and winter

11

Load Following

12

100 200 300 400 500 600 700 800 900 1000 Jan-1 Feb-1 Mar-1 Apr-1 May-1 Jun-1 Jul-1 Aug-1 Sep-1 Oct-1 Nov-1 Dec-1

Dam Release (m3/s)

1980

Load Following - 1980

13

12.0 12.5 13.0 13.5 14.0 14.5 15.0 15.5 Jan 1989 Feb 1989 Mar 1989 Apr 1989 May 1989 Jun 1989 Jul 1989 Aug 1989 Sep 1989 Oct 1989 Nov 1989 Dec 1989 Jan 1990

Water Level (m)

nhc (1999)

• nhc was retained by Kootenay Diking Districts to

investigate bank erosion

“It is considered probable that the development of this notch is more pronounced now that the river level is controlled by Libby Dam in comparison to pre-Libby Dam, when the river level fluctuated over a wider range and the short duration releases from Libby Dam did not

• ccur. The more limited range of water levels, greater fluctuations in

flows during the winter season, and more frequent cycles of wetting and drying appears to induce a weakening of the banks resulting in toppling of soil wedges.”

14

Dike Erosion

• The US Army Corps of Engineers

(2006) have also concluded that past practices of load following contributed to the erosion of the toe slope of much

• f the levee system in the Kootenai

Valley

• Lack of riparian vegetation is also

likely a factor

• Maximum ramping rates were

therefore prescribed in the late 1990s

– implemented not only for fisheries but also to help minimize dike/levee erosion along the river

15

Prescribed Ramping Rates

16

100 200 300 400 500 600 700 800 900 1000 Jan-1 Feb-1 Mar-1 Apr-1 May-1 Jun-1 Jul-1 Aug-1 Sep-1 Oct-1 Nov-1 Dec-1

Dam Release (m3/s)

1980 2010

Load Following

17

11.5 12.5 13.5 14.5 15.5 16.5 17.5

01-Jan 01-Feb 01-Mar 01-Apr 01- May 01-Jun 01-Jul 01- Aug 01- Sep 01-Oct 01- Nov 01- Dec

Water Level (m)

2006 2008

Standard vs VARQ FC

• In December 2000, the USFWS and the National Marine

Fisheries Service (NMFS) each issued a Biological Opinion

• utlining measures to protect endangered species including

sturgeon, bull trout, salmon and steelhead

• Recommended measures included VARQ FC
• Intent of VARQ FC is to provide additional flows for

downstream fish while continuing to provide adequate downstream flood protection

18

Standard vs VARQ FC

• Dam began discharging less water during the fall/winter

period and more water during the spring/summer to benefit downstream fish.

• Standard and VARQ FC have the same storage space for

flood control when then water supply forecast is 120% of normal

• In practice, there is only a difference in the two methods when

the inflow forecast is between 80% and 120% of normal

19

Standard vs VARQ FC

20

530 531 532 533 534 535 536 537

Jan-01 Feb-01 Mar-01 Apr-01 May-01 Jun-01 Jul-01 Aug-01 Sep-01 Oct-01 Nov-01 Dec-01

Average Water Level (m)

pre-Libby Dam (1937-1971) Standard FC (1973-1992) Standardl FC (1993-2002) VARQ FC (2003-2011)

Standard vs VARQ FC

21

0.2 0.4 0.6 0.8 1 1.2 Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Average Daily Velocity (m/s)

Standard FC ( 1973-1992) pre-Libby Dam (1938-1971) VARQ FC (2003-2012) Standard FC ( 1993-2002)

Conclusion

• Implementation of VARQ FC has not had a significant impact
• n diking infrastructure adjacent to the Kootenay River
• The past practice of load following did have a significant

negative impact on diking infrastructure

• High flows in 2011 and 2012 may be contributing to

perception of impacts

– highest lake level on Kootenay Lake in 2012 in 38 years – also record June and July rainfall

22