The effects of climate change and land use on basin hydrology: a review of major forcings affecting water balance

Transcription

1 Back to previous page The effects of climate change and land use on basin hydrology: a review of major forcings affecting water balance Presented by: Jon Fennell, Ph.D., P.Geol. P.Geo.

2 Overview Causes of climate change Anthropogenic influences (CO 2?) Celestial events over varying time scales Short and long-term events tele-connections & synoptic patterns Empirical evidence Effects of land cover and terrain Combined effects on regional and local scale hydrology 2

3 Causes of climate change Significant changes in forcing variables: Not a novel concept to Mother Nature Fluctuations in IRabsorbing constituents (e.g., CO 2 + other GHGs, aerosols, water vapour) Shift in planetary orbit (Milankovitch cycles) Change in solar energy balance (solar storms, length of Hale cycle; insolation) Numerous warming and cooling events over last 54 million years 3

4 Global warming & CO N. hemisphere ºC Some relationship between temperature and CO 2 (but not perfect) Temerpature anomaly (ºC) ºC trends S. hemisphere ºC CO 2 levels Oil embargo Post-war economic boom Atmospheric CO 2 (ppm) Variable temperature trends general increase since early 19s (slight difference between N & S hemispheres; related to land mass differences & ocean effects) 4

5 Long-range phenomena Good correlation between temperature and length of solar cycle (shorter cycles = higher intensity sunspot activity = more energy absorbed by oceans dissipated globally) 5

6 Long-range phenomena Milankovitch cycles 1) Variation in aspect to, and distance from, the sun 2) Results in shift in global energy balance (small but significant) 3) Long cycles compared to other smaller scale phenomenon 6 Source: S. Rutherford, 1997

7 Combined effects Four major icehouse and greenhouse periods over last 54 million year notable fluctuations between periods Ice core data indicate significant temperature variation over last 73, years apparent correlation between CO 2 & temperature but slight lag of CO 2 of 8 to 1, yrs Deviation from mean (deg ºC C) , CO2 - Vostok core Anthropogenic CO 2 Temp. based on del D - EPICA Dome C Peak of Interglacial Peak of Glaciation 6, 5, 4, 3, 2, 1, Deviation from CO2 mean (ppm) CO 2 (ppm) 7 Years (BP)

8 El Niño Southern Oscillation (ENSO) What is the ENSO? 1) Forms in waters off Ecuador & Peru El Niño causes abnormally warm sea surface temperatures (SST) over the eastern half of the equatorial Pacific (opposite for La Niña ) 2) Southern Oscillation is east-west sea level pressure (SLP) see-saw that directly affects tropical weather around the globe; strong MJO activity 6-12 months prior to peak of El Niño cycles 3) El Niño/La Niña cycles and swings of the Southern Oscillation typically occur together El Niño SST anomaly ( C deviation from mean) La Niña effects can last 6-18 months 2-7 years return period 8 dominant current

9 Pacific Decadal Oscillation (PDO) What is the PDO? 1) A long-lived ENSO-like pattern of Pacific climate pole-ward of 2 N influenced by sea-surface temperature and sea level pressure variability 2) Events persist for 2 to 3 years compared to 2 to 7 years cycles for ENSO Cool phases: & Warm phases: & 1977 to mid-9s 3) Warmer phases tend to bring warmer/drier conditions to western Canada (i.e., drought); opposite for cooler phases 4) PDO index related to relative SST: + values warming trend - values cooling trend + Phase SST anomaly ( C deviation from mean) - Phase 9 dominant current

10 Atlantic Multidecadal Oscillation (AMO) What is the AMO? 1) Long-lived Atlantic phenomenon affecting sea-surface temperature anomalies from -7ºN 2) Caused by internal variation of thermohaline circulation and meridional heat transport 3) Inverse relationship to precipitation in central and western North America; modulating effect on ENSO cycles 4) Cool phases: & Warm phases: , & 1995-present 1

11 Pacific North American Pattern (PNA) What is the PNA? Synoptic pattern 1) Characteristic positioning of continental pressure systems 2) Major influence on jet stream and resulting storm track (distributor of moisture) L H L Ridge Trough L H 3) PNA is dominant pattern affecting weather and climate of North America 4) Connected to ENSO and PDO events Polar jet-stream track 11

12 Correlations Correlation coefficients: PDO vs. MEI =.73 PDO vs. PNA =.64 Index values per. Mov. Avg. (PDO) 5 per. Mov. Avg. (ENSO) 5 per. Mov. Avg. (PNA) Reasonable correlation between all three events (but operating on different time scales fractal?) 12

13 Combined effects of short-range phenomena Drought Drought 1. -,+ -,- +,+ 2. AMO index PDO index -,- +,- +,- +,+ -, AMO PDO Source: McCabe et al., 23 Cycles of various climate phenomena can affect moisture conditions over broad areas (both additive and subtractive; +,+ phase since early 2s = drought conditions) 13

14 Some related effects 22 Lesser Slave Lake, AB 2 Cold Lake, AB 2 18 Days Days frozen Frozen Days frozen Days frozen Diefenbaker Lake, SK Ice phenology indicates shorter winters - Longer growing season - More evapotranspiration and open surface evaporation

15 Some related effects 5 Chateau Lawn (Elev.= = masl) masl) 5 Sullivan Mine, BC (Elev.= 155 masl) Snow equivalent Snow water equiv. (mm) PDO + PDO Average Snow water equiv. (mm) PDO + PDO Snow water equivalent equiv. (mm) Bow River Station (Elev.= 1585 masl) Bow River Station (Elev = 1585 masl) - PDO + PDO Declining snow pack (serious issue for snowmelt dominated basins) Less supply of melt-water to streams (more reliance on later season precipitation to sustain soil moisture & stream flows)

16 Some related effects Increased infestations of destructive insects (greatest effects from mountain pine beetle after 198)

17 Some related effects 1 Forest fires.75 8 Temperature N. hemisphere temp..5 Fire frequency Temperature (deg C) Increase in frequency and size of forest fires Economic losses (merchantable timber, insurance costs) Loss of wildlife habitat; reduced aesthetics Changes to basin hydrology (hydrophobic soils & effects to runoff conditions) 17

18 Effects to hydrology Predicted Mean Flow (existing) Mean Flow (predicted) Flow m 3 /s Existing Shift in timing, magnitude and amount of flows (ramifications for reservoir storage; power generation, etc.) Decrease in average flows Spring Summer Fall Winter 18

19 Source: River Forecast Centre, BC MOE Evidence of changes in flow characteristics

20 2 1% 8% 6% 4% 2% % Flat (-5%) Rolling (5-1%) Hilly (1-3%) Role of terrain, vegetation & soil texture Combined effects of vegetative cover, terrain and soil type on runoff coefficients - strong influence on soil moisture and recharge Alpine pastures Mountain forests Meadows, pastures Coniferous Deciduous Grassland Semi-desert Woodland Pature Lawns Cultivated Runoff coefficients Evapotranspiration (as % of precip.)

21 Evidence of combined effects Forest-covered Vegetative cover reduces evaporation and runoff (less incident solar radiation and wind exposure; greater relative humidity) Cultivated Moist Less water loss via evaporation compared to cleared areas Drier 21

22 Continental effects Deforestation Irrigation Net change Source: L.J. Gordon et al., 25 (-) (+) Net change in annual water vapour flux (in mm) 22

23 Regional effects Vegetation cover affects precipitation patterns (effects of alteration to vegetative cover can be significant) 23

24 Regional effects Source: AENV, Less potential for evaporation in forest-covered areas

25 Combined effects on basin hydrology Cleared Area/Cropped Wet Forest/Bog Forest Water Land Cover 1976 Beaver River Basin, AB 25

26 Combined effects on basin hydrology Decrease in total forest cover 11% in Green Zone (forest covered) 23% in White Zone (cleared / cropped) Land Cover 22 Beaver River Basin, AB 26

27 Effects on basin hydrology Forest covered 9% reduction Cultivated 35% reduction Decrease in available surface water greater in cultivated areas versus forested area (moderating effect of vegetation evident) 27

28 Effects on temperature & precipitation PDO index Cold Lake Station, AB - PDO + PDO 5 per. Mov. Avg. (Temperature) 5 per. Mov. Avg. (PDO index) Temperature ( C) (ºC) Significant influence of short and longer-term climate events on basin inputs and outputs PDO index 28 PDO Index January 197 PDO and Precipitation 198 at Cold Lake PDO - PDO + PDO Temp. (5-yr moving avg.) PDO. (5-yr moving avg.) Precip. (5-yr moving avg.) January Cold Lake Precipitation (5-yr moving average) PDO. (5-yr moving avg.) January PDO (5-yr moving average) Precipitation (mm) Precipitation (mm) - sympathetic trend with temperature - inverse trend with precipitation - positive phase = drought conditions

29 Effects on basin water levels Water level (masl) PDO Cold Lake, AB + PDO Water level (masl) Two Hills AB, pre-1975 pre-1975 Two Hills AB, post-1975 post-1975 Lake level (masl) Mean 1954 to 1975 = m 1976 to 21 = m PDO + PDO Laurier Lake, AB Mean level Mean level PDO + PDO Effects of ENSO & PDO phases evident on large/small water bodies + aquifer levels

30 Effects on sensitive flow conditions Athabasca Basin Min. flow (m3/s) Athabasca R. below Ft. McMurray cool - PDO warm + PDO Precip. (mm) Min. flow (m3/s) Athabasca R. near Athabsca 15 cool - PDO warm + PDO Precip. (mm) Min. flow (m3/s) Athabasca R. at Hinton cool - PDO warm + PDO Precip. (mm) Precip. Flow

31 Effects on sensitive flow conditions PDO phases PDO phases PDO phases PDO + PDO Source: S. Rood et al., Cumulative % deviation of means from average annual discharge of some western North American rivers negative correlation with PDO phases

32 AOGCM results CGCM2 A21 (SRES) Annual mean ºC change: 22s CGCM2 A21 (SRES) Annual precipitation change: 22s Modelled results indicate significant increase in ºC at higher latitudes CGCM2 A21 (SRES) Annual mean ºC change: 28s CGCM2 A21 (SRES) Annual precipitation change: 28s Generally wetter conditions predicted for higher latitudes Increased frequency of droughts anticipated

33 So what does this all mean? Things are getting warmer, whether we like it or not (anthropogenic effects, natural cycles or a combination is irrelevant) Effects of climate change to basin water balances is evident. but human alterations to landscape can be additive (underscores need or water and soil conservation measures) Recognizing how and when these effects manifest themselves is critical for basin sustainability and security of water supplies (i.e., phasing of climate tele-connections) Adaptation strategies will need to be implemented to ensure healthy ecosystem and economy (IFNs, demand management, storage strategies, conjunctive use) 33

34 34 Thank you.