Outline. Regional Overview Mine Study Area. Transportation Corridor Study Area. Streamflow Low Flow Peak Flow Snow Small Pools.

Transcription

1 Environmental Baseline Document Surface Water Hydrology Agency Meetings, January 31 to February 3, 2012 Anchorage, Alaska Jaime Cathcart, P.Eng., Ph.D.

2 Outline 2 Regional Overview Mine Study Area Streamflow Low Flow Peak Flow Snow Small Pools Transportation Corridor Study Area Streamflow Low Flow Peak Flow

3 Regional Overview: Prior to

4 Regional Overview:

5 Regional Overview:

6 Regional Overview Prior to 2004 USGS: 2 active, 6 discontinued Cominco: 4 intermittent/discontinued USGS: 6 new (including 3 for Pebble) Pebble: 26 new (Mine Study Area) USGS: 3 new Pebble: 3 new (Transportation Corridor) 6

7 Regional Overview Summary of Active Gaging Stations: USGS: 11 stations drainage area = 20,700 sq. miles density = ~1 per 2000 sq. miles Pebble: 29 stations drainage area = 350 sq. miles density = ~1 per 12 sq. miles 7

8 Mine Study Area 8

9 Mine Study Area: 2008 (Continuous) No changes for 2009/10 9

10 Mine Study Area: 2008 (All) No changes for 2009/10 10

11 Discharge Measurement Methods Velocity Meter Salt Dilution 11

12 Discharge Measurement Methods Acoustic Doppler Current Profiler 12

13 Discharge Measurement Methods 13 Velocity Meter Salt Dilution

14 Rating Curve Development Stage (ft) Q = 80.0 (h ) Discharge (cfs) 14

15 Discharge Measurement Methods Stage (ft) Q = 80.0 (h ) = Discharge (cfs) Daily Discharge (cfs) Rating curve Pressure transducer (continuous stage record) Jul-04 Mar-05 Dec-05 Aug-06 May-07 Feb-08 Oct-08 Jul-09 Apr-10 Dec-10 Date hydrograph

16 Mine Study Area: Typical Hydrograph RAIN RAIN 16

17 Typical Hydrograph Autumn Spring Autumn Spring Autumn Spring Autumn Spring Autumn Spring Autumn Spring Autumn Daily Discharge (cfs) Jul-04 Feb-05 Sep-05 May-06 Dec-06 Jul-07 Mar-08 Oct-08 May-09 Dec-09 Aug-10 Date

18 Mine Study Area: Drainage Basins Mainstem flows 18

19 8.0 Unit Mean Monthly Discharge (cfs/sq. mile) Mine Study Area: Hydrographs South Fork Koktuli River (SK100A) North Fork Koktuli River (NK100A) Upper Talarik Creek (UT100 APC3) Iliamna MAP ~ 27 inches 1.0 South Fork Koktuli River unit MAD = 2.41 cfs/sq. mile = 32.7 inches North Fork Koktuli River unit MAD = 2.34 cfs/sq. mile = 31.8 inches Upper Talarik Creek unit MAD = 2.29 cfs/sq. mile = 31.1 inches Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

20 Mine Study Area: Drainage Basins Mainstem and tributary flows 20

21 12.0 Mine Study Area: Hydrographs 10.0 South Fork Koktuli River (SK100A) Unit Mean Monthly Discharge (cfs/sq. mile) South Fork Koktuli River Tributary (SK119A) South Fork Koktuli River unit MAD = 2.41 cfs/sq. mile = 32.7 inches South Fork Koktuli River Tributary unit MAD = 3.32 cfs/sq. mile = 45.0 inches Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

22 Mine Study Area: Drainage Basins Losing and gaining reaches gaining losing 22

23 7.0 Unit Mean Monthly Discharge (cfs/sq. mile) Mine Study Area: Hydrographs SFK (SK100F) upstream Drainage Area = sq. miles SFK (SK100C) middle Drainage Area = sq. miles SFK (SK100B) downstream Drainage Area = sq. miles 0.0 SK100F unit MAD = 2.46 cfs/sq. mile = 33.4 inches SK100C unit MAD = 1.27 cfs/sq. mile = 17.2 inches Jan Feb Mar Apr May SK100B Jun unit MAD Jul = 2.63 Aug cfs/sq. mile Sep= 35.7 inches Oct Nov Dec Month

24 Mine Study Area: Inter Basin Flow (upstream) (downstream) August 2005 July

25 Mine Study Area: Drainage Basins Effect of interbasin transfer 25

26 Mine Study Area: Hydrographs Unit Mean Monthly Discharge (cfs/sq. mile) Upper Talarik Creek Tributary (UT119A) UT119A approximate baseflow contribution from SFK Upper Talarik Creek unit Tributary MAD unit = 2.29 MAD cfs/sq. = 7.07cfs/sq. mile = 31.1 mile inches = 95.9 inches Upper Talarik Creek Tributary unit MAD = 7.07cfs/sq. mile = 95.9 inches Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

27 Mine Study Area: Hydrographs Unit Mean Monthly Discharge (cfs/sq. mile) Upper Talarik Creek Tributary (UT119A) UT119A approximate baseflow contribution from SFK Upper Talarik Creek (UT100 APC3) UT100 APC3 approximate baseflow contribution from SFK Upper Talarik Creek unit Tributary MAD unit = 2.29 MAD cfs/sq. = 7.07cfs/sq. mile = 31.1 mile inches = 95.9 inches Upper Talarik Creek Tributary unit MAD unit = 2.29 MAD cfs/sq. = 7.07cfs/sq. mile = 31.1 mile inches = 95.9 inches Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

28 Mine Study Area: Hydrographs UT119A May 2007 Q = 25 cfs. UT119A - February 2007 Q = 25 cfs. 28

29 Mine Study Area: Streamflow Summary Similar Hydrograph Patterns Bimodal spring and fall peaks Late winter low flow period Unit runoff compared to Iliamna Orographic influences Surface/Groundwater Interactions 29

30 Mine Study Area: Low Flow Characterization of late winter low flow conditions ( ) Winter measurements at gaging sites and additional low flow sites in March (26) Open water surveys 30

31 Low Flow: Open Water 31

32 Mine Study Area: Low Flow 32

33 Mine Study Area: Low Flow Assessment of low flow characteristics ( ) Step: Compared regional and site specific low flow values Used USGS regional regression equations to estimate low flow for study area gaging stations Calculated low flow values from study area gage records Compared values, which suggested that USGS equations over predict low flows 33

34 Mine Study Area: Peak Flow USGS equations over predict low flows Plot comparing measured and USGS low flow values. 34

35 Mine Study Area: Peak Flow Assessment of peak flow characteristics ( ) Step 1: Compared regional and site specific flood values Used USGS regional regression equations to estimate mean annual flood for study area gaging stations Calculated mean annual flood from study area gage records Compared values, which suggested that USGS equations under predict peak flows 35

36 Mine Study Area: Peak Flow USGS equations under predict peak flows 36

37 Mine Study Area: Peak Flow Assessment of peak flow characteristics Step 2: Developed a site specific estimation procedure Determined the ratios of extreme floods to the mean annual flood using the USGS equations. Applied these ratios to the mean annual floods from the study area gage records to estimate extreme floods for each gage site. 37

38 Mine Study Area: Snow Assessment of snow distribution and ablation patterns Data collection ( ) Snow surveys Satellite images during ablation season Lidar survey of snow surface 38 Snow Distribution Modeling Snow accumulation and water equivalent Snow distribution Snow ablation

39 Mine Study Area: Snow Survey 39

40 Mine Study Area: Snow Survey 40

41 Mine Study Area: Satellite Images Full snow cover No snow cover 41

42 Mine Study Area: Lidar Images 42

43 Mine Study Area: SWE Station Basin Area (mi. sq.) Modeled Mean Snow Water Equivalent for Basin (inches) 19 Apr 06 9 Apr 07 6 Apr 08 SK100A NK100A UT100 APC

44 Mine Study Area: Snow Depth Lidar image Figure 7.2D 14 April

45 Mine Study Area: Distribution Couple of images Figure 7.2D 22 45

46 Mine Study Area: Ablation 46

47 Mine Study Area: Snow Summary Snow depth and snow water equivalent are highly variable throughout the site and from year to year, but typically is in the order of 20 inches for the basin average. Ablation typically begins in April and the timing is generally consistent with the topography. 47

48 Mine Study Area: Pools Assessment of pool characteristics Data collection ( ) 123 pools studied Surface water and groundwater levels and chemistry sampled Pool Assessment Two types of pools: Perched precipitation pools ( puddles ) 45 Flow through pools (interact with groundwater) 78 48

49 Mine Study Area: Pools Perched pool Flow through pool 49

50 Transportation Corridor 50

51 Transportation Corridor: 2008 Streamflow 51

52 Transportation Corridor: 2010 Streamflow 52

53 Transportation Corridor: Streamflow Continuous Gages Prior to 2004 USGS: 1 active, 1 discontinued USGS: Pebble: 2 new 2 new (Newhalen River) USGS: Pebble: 0 new 3 new

54 Transportation Corridor: Streamflow Crest Gages Prior to 2004 USGS: 1 active, 1 discontinued USGS: Pebble: 0 new 13 new USGS: Pebble: 0 new 0 new

55 Transportation Corridor: Streamflow A regional assessment indicates a strong east/west runoff gradient and a change in annual hydrograph patterns, which is tied to the physiography. Hills Lowlands Mountains Ocean 55 Mine Study Area Transportation Corridor

56 Transportation Corridor: Streamflow Roadhouse Creek MAUR = 18 inches South Fork Koktuli River MAUR = 33 inches Iliamna River MAUR = 95 inches Hills Lowlands Mountains Ocean 56 Mine Study Area Transportation Corridor

57 Transportation Corridor: Gradient Regional assessment indicated a strong east/west precipitation and runoff gradient and change in annual hydrograph patterns. Mean Annual Precipitation (Inches) Pebble Mine Site (Jones and Fahl, 1994) 57

58 Ratio of Mean Monthly Discharge to Mean Annual Discharge Transportation Corridor: Streamflow South Fork Koktuli River (SK100A) Roadhouse Creek Station ( ) Iliamna River Station ( ) Regional assessment indicated a strong east/west runoff gradient and change in annual hydrograph patterns. Figure with SK100A added Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

59 Transportation Corridor: USGS Regions 59

60 Transportation Corridor: Peak/Low Flows Currently, low flow and peak flow values are estimated from USGS equations. Region 4 equations are used for the west end of the corridor and Region 3 equations are used for the east end. The values and estimation procedures will be updated as more site specific data are collected. 60

61 61 QUESTIONS?