Decade-Scale Precipitation Variations

1. USDA-ARS-GRL Decade-Scale Precipitation Variations in the Great Plains Jurgen Garbrecht USAD - ARS Grazinglands Research Laboratory El Reno, Oklahoma

2. USDA-ARS-GRL ? Why study precipitation Primary climatic driver of agriculture and water resources. Water is limited and limiting resource. Climatic system driven by global-scale phenomena and subject to variations.

3. USDA-ARS-GRL Precipitation varies at different scales: Daily Monthly Annual Decade Century Longer

4. USDA-ARS-GRL - Regional character of d-s P variations. - Impact on stream flow. - Seasonal aspects of d-s P variations.

5. USDA-ARS-GRL Decade-Long Precipitation Variations

6. USDA-ARS-GRL

7. USDA-ARS-GRL 0 500 km C A N A D A Great Lakes R o c k y M i s s i s s i p p i M o u n t a i n s R i v e r M E X I C O Gulf of Mexico

8. C A N A D A 1 2 4 3 5 6 a 9 7 b a Atlantic Ocean Pacific Ocean b 8 Gulf of Mexico MEXICO Increased precipitation in 1990-1999 Increased precipitation in 1980-1999 No increased precipitation at the end of the 20th century

9. USDA-ARS-GRL 6 OK, TX, AR, LA 11-yr MA of Annual Precipitation Standardized AP

10. USDA-ARS-GRL 5 KS, NE, MO, IO 11-yr MA of Annual Precipitation Standardized AP

11. USDA-ARS-GRL SD, MN 4 11-yr MA of Annual Precipitation Standardized AP

12. USDA-ARS-GRL 80% 80 Climate Division 5 Oklahoma 1895-1979 1980-1999 60 Probability of Occurrence 40 33% 33% 33% 20 12% 8% 0 Dry Year Average Year Wet Year

13. USDA-ARS-GRL Impact of the Decade-Scale Increase in Precipitation on Stream Flow

14. C A N A D A 1 2 4 3 5 6 a 9 7 b a Atlantic Ocean Pacific Ocean b 8 Gulf of Mexico MEXICO Increased precipitation in 1990-1999 Increased precipitation in 1980-1999 No increased precipitation at the end of the 20th century

15. USDA-ARS-GRL SD NE WY Elkhorn Big Blue IA Little Blue KS Neosho MO CO Walnut Verdigris OK Climate Division River Basin State line

16. USDA-ARS-GRL R2 of precipitation versus streamflow Drainage area [sq. mi.] Period of record River name 1929-99 6900 0.48 Elkhorn, NE 1933-99 4447 0.59 Big Blue, NE 1930-99 2350 0.64 Little Blue, NE 1922-99 4905 0.78 Neosho, KS 1922-99 1880 0.64 Walnut, KS 1921-99 2982 0.77 Verdigris, KS

17. USDA-ARS-GRL Mean annual precipitation Increase % 1980- 1999 [in] prior- 1980 [in] River name  P 26.7 11 Elkhorn, NE 24.0 30.4 27.8 Big Blue, NE 9 7 29.6 27.6 Little Blue, NE 37.8 9 34.6 Neosho, KS 39.9 36.2 Walnut, KS 10 37.2 40.1 Verdigris, KS 8

18. USDA-ARS-GRL Mean annual streamflow Increase % 1980- 1999 [cfs] prior- 1980 [cfs] River name Q 2046 Elkhorn, NE 1098 86 Big Blue, NE 1095 787 39 428 369 16 Little Blue, NE Neosho, KS 3494 2560 36 Walnut, KS 1081 801 35 2283 Verdigris, KS 1685 35

19. USDA-ARS-GRL Climate Divisions in Oklahoma Tulsa OKC N Little Washita River Experimental Watershed Glover Watershed

20. USDA-ARS-GRL Chickasha Great Plains Experiment Station Anadarko USGS stream gage River ARS rain gage Little National Weather Service rain gage Washita OKLAHOMA N 10 Km (6.2 mi.) Marlow Situation Map Little Washita River Experimental Watershed

21. USDA-ARS-GRL 11-yr moving average of annual runoff and precipitation depth 155 935 Runoff 130 Precipitation 885 105 835 80 785 Runoff [mm] Precipitation [mm] 55 735 30 685 Little Washita River Watershed, OK 5 635 1950 1960 1970 1980 1990 2000 Year

22. USDA-ARS-GRL 11-yr moving average of annual runoff versus precipitation depth 150 125 100 75 Runoff [mm] 50 Little Washita River Watershed, OK 25 0 650 700 750 800 850 900 950 Precipitation [mm]

23. USDA-ARS-GRL 11-yr MA of Annual Retention vs Precipitation Depth Little Washita River Watershed, OK Runoff Retention

24. USDA-ARS-GRL Climate Divisions in Oklahoma Tulsa OKC N Little Washita River Experimental Watershed Glover Watershed

25. USDA-ARS-GRL 11-yr moving average of annual runoff and precipitation depth 700 1400 Runoff Precipitation 600 1300 500 1200 Runoff [mm] Precipitation [mm] 400 1100 Glover Watershed, OK 300 1000 1960 1970 1980 1990 2000 Year

26. USDA-ARS-GRL 11-yr MA of Annual Precip-Runoff Glover Watershed, OK

27. USDA-ARS-GRL Glover Watershed, OK Runoff Retention

28. USDA-ARS-GRL Seasonal pattern of decade-scale precipitation variations Case application using divisional precipitation data in southwestern Oklahoma

29. USDA-ARS-GRL 11-Year MA of Annual Precipitation Southeastern Oklahoma Annual Precip [mm] Year

30. USDA-ARS-GRL 11-Year MA of Seasonal Precipitation Southeastern Oklahoma JAS JFM OND AMJ Annual Departure from mean % Year

31. USDA-ARS-GRL Conclusions At the end of the 20th century, the majority of the Great Plains was under the influence of the longest and strongest decade-scale precipitation increase of the entire century.

32. USDA-ARS-GRL Conclusions Streamflow runoff from watersheds in the Nebraska, Kansas and Oklahoma responded very sensitively to the decade-scale precipitation increase.

33. USDA-ARS-GRL Conclusions Due to the disproportionate increase of streamflow during the decade-scale precipitation increase, crop and forage production only benefited from a portion of the precipitation increase.

34. USDA-ARS-GRL Conclusions The strong fall and winter increase in precipitation associated with the decade-scale variations favors fall and winter crops.

35. USDA-ARS-GRL Conclusions The decade-scale precipitation increase has helped meet the water needs of a growing economy and society. However, the increased demand for water has made the economy and society more vulnerable to decade-scale variations in precipitation.