The Past, Present and Future of Prairie Droughts and Their Impacts

Transcription

1 The Past, Present and Future of Prairie Droughts and Their Impacts Peter Leavitt, Gemai Chen, Jim Rusak, Sybille Wunsam University of Regina Brian Cumming Queen s University

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3 Sustainable Agriculture in Western Canada: Planning for Droughts Using the Past Agriculture & Agri-food Canada Manitoba Hydro Alberta Agric. Financial Services MB Crop Insurance Corp. Alberta Agriculture and Food Prairie Farm Rehab. Admin Canadian Wheat Board Sask Agriculture and Food Canadian Wildlife Service Sask Crop Insurance Corp. Ducks Unlimited (IWWR) Sask Environment Environment Canada (AES) Sask Grazing & Pasture Tech. Geological Survey of Canada Sask Research Council Heritage Parks Canada Sask Water Corp. Canadian Plains Res. Centre Sask Wetlands Corp. NSERC Canada

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10 = optimum = tolerance

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12 30 Humboldt Lake, SK 25 Salinity (g/l) Year (AD)

13 Objectives 1. Quantify the relationship climate, agriculture and past lake chemistry. 2. Measure the occurrence of past severe droughts and floods over 2000 years and determine if cycles are present. 3. Quantify the risk of climatic extremes in the next 30 years. 4. Compare risks along landscape gradients. 5. Evaluate effects on aquatic resources.

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17 Flax Aug_Evap Sept_PDI 12month_SPI Ppte departure r 2 =

18 Yield (bu/ac) r = , P< Flax salinity Year (AD) salinity (g/l)

19 Objectives 1. Quantify the relationship climate, agriculture and past lake chemistry. 2. Measure the occurrence of past severe droughts and floods over 2000 years and determine if cycles are present. 3. Quantify the risk of climatic extremes in the next 30 years. 4. Compare risks along landscape gradients. 5. Evaluate effects on aquatic resources.

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22 35 Chauvin Lake, AB 30 Salinity (g/l) Year (AD)

23 35 Chauvin Lake, AB 30 Salinity (g/l) Year (AD)

24 20 Chauvin Lake, AB Detrended Salinity (g/l) Year (AD)

25 20 Chauvin Lake, AB Detrended Salinity (g/l) drought Year (AD)

26 20 Chauvin Lake, AB Detrended Salinity (g/l) Inter-arrival time Year (AD)

27 Weibull Model f(x;α,β) = (β/α)(x/α) β-1 exp{-(x/α) β }, 0 < x,0 < α,0 < β. α β = scale parameter = shape parameter x = inter-arrival time Maximum likelihood parameter fit

28 Conditional Probability Analysis P(X < y X > y 0 ) = exp{-(y 0 /αˆ) βˆ} - exp{-(y/αˆ) βˆ} exp{-(y 0 /αˆ) βˆ} - no droughts since 1988

29 0.7 Chauvin Lake Droughts 0.6 Probability Year

30 Probability xCO 2? Chauvin Lake Droughts Year

31 Detrended Salinity (g/l) Chauvin Lake, AB 5 added droughts Year (AD)

32 Chauvin Lake Warming Impacts +5 droughts = 1% Probability X Year

33 Probability Chauvin Lake Droughts worst-case $2000 billion Year

34 20 Chauvin Lake, AB Detrended Salinity (g/l) Year (AD)

35 Chauvin Lake Droughts Power Period (years)

36 Chauvin Lake Drought Statistics Mean inter-arrival time Std deviation Mode Maximum Minimum Number of droughts Duration Std deviation Mode Maximum Minimum Period 60.5 yr None yr yr, 295 yr P< 0.001

37 Objectives 1. Quantify the relationship climate, agriculture and past lake chemistry. 2. Measure the occurrence of past severe droughts and floods over 2000 years and determine if cycles are present. 3. Quantify the risk of climatic extremes in the next 30 years. 4. Compare risks along landscape gradients. 5. Evaluate effects on aquatic resources.

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39 Alberta Saskatchewan Salinity (g/l) Manitoba North Dakota Year (AD)

40 Probability Drought Risk Comparison AB ND MB SK Year

41 Drought Statistics Mean inter-arrival Std deviation Mode Maximum Minimum Number of events Alberta Saskatchewan Manitoba None None N. Dakota Duration Std deviation Mode Maximum Minimum Period 98, 295* 44, 103, 302* 30, , 158*

42 Objectives 1. Quantify the relationship climate, agriculture and past lake chemistry. 2. Measure the occurrence of past severe droughts and floods over 2000 years and determine if cycles are present. 3. Quantify the risk of climatic extremes in the next 30 years. 4. Compare risks along landscape gradients. 5. Evaluate effects on aquatic resources.

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44 Depth (m) Humboldt Water Level 6.7 m 4.9 m 3.2 m Year (AD)

45 Depth (m) Humboldt Water Level Year (AD)

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48 Total algae (r 2 = 0.02) algal abundance (B-carotene) salinity ( o / oo )

49 250 N 2 -fixing cyanobacteria (r 2 =0.35) algal abundance (aphanizophyll) salinity ( o / oo )

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51 salinity ( o /oo ) δ 15 N organic matter ( o / oo ) year

52 salinity ( o / oo ) δ 15 N organic matter ( o /oo)

53 dry humid 14 N 2 NO 3 N 2 Mg ++ Cl - HCO 3 - Na + SO 4 = -O 2 Cl - +O 2 Ca +

54 -20 δ 13 C organic matter ( o / oo ) salinity ( o /oo ) year

55 δ 13 C organic matter ( o / oo ) salinity ( o / oo )

56 Conclusions 1. Severe droughts are a natural feature of the Prairies. Extreme droughts (e.g., 1930s) occur every years, with 23-45% probability of occurring by Most droughts are long-lasting (5-10 year duration). 3. Extreme events have some periodicity. Droughts have 14, 22, 30 and 100 year cycles. Floods have 25, 50 and 300 year cycles. 4. Future climatic warming will increase drought likelihood. However, given variable drought frequency, risk of occurrence will change little over the next 30 years.

57 Conclusions 5. Surface water quantity and quality will diminish during severe droughts. Water will be less potable. Toxic algae may be more abundant. 6. Basic biogeochemical cycling in lakes (e.g., N) is altered during droughts. 7. Ability of lakes to sequester carbon will not be diminished unless lakes are lost.

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59 Implications 1. Strong correlation between reconstructed climate and crop production shows that risk forecasts are most relevant to the Prairie agricultural sector. 2. Common drought cycles suggest continentalscale causal mechanisms (solar, lunar, PDO). However, most variance is non-cyclic and nondirectional. Adaptation should be to high variability, not cycles th century climate was benign. Global warming may return the Prairies to past, higher drought frequency. Severe droughts of the 19 th century may be the best model for expected impacts.

60 Implications (continued) 4. Coherent prairie-wide droughts can occur (e.g., 1890s), but intensity varies with locale. Network adaptation strategies are recommended (e.g., inter-provincial crop insurance, PFRA et al). 5. Drought onset is usually rapid and may prevent effective ad hoc adaptation to prolonged events (e.g., 1930s). 6. Droughts can last decades. Adaptation should be to multi-year events.

61 Implications (continued) 7. Droughts will reduce both the quantity and quality of surface waters. Reservoirs may an ineffective adaptation strategy. 8. Despite high probabilities of future droughts (45% by 2030), risk assessments may be conservative because sites are not located in most droughtprone regions.

62 Elements of Success Combine scientific (theoretical) and practical interests. Develop projects with end-users (finance). Involve end-users in research (participate). Hold regular workshops (communicate). Iterate project goals (adapt). Involve media and public early (educate). Engage politicians and policy makers.

63 Constraints on Success Expected outcome achieved. Ability and willingness of users to adapt. Financial and political limitations to adaptation. Public support for outcome. Cost. Investigator availability. Technical issues - chronology, reproducibility, representation.