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

2. 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. USDA-ARS-GRL

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

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

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

7. Gulf of Mexico M o u n t a i n s R o c k y Great Lakes 0500 km M i s s i s s i p p i R i v e r USDA-ARS-GRL

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

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

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

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

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

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

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

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

16. River name Drainage area [sq. mi.] Period of record Elkhorn, NE 6900 1929-99 Little Blue, NE 2350 1930-99 Big Blue, NE 4447 1933-99 Neosho, KS 4905 1922-99 Walnut, KS 1880 1922-99 Verdigris, KS 2982 1921-99 R 2 of precipitation versus streamflow 0.48 0.64 0.59 0.78 0.64 0.77 USDA-ARS-GRL

17. River name Mean annual precipitation Elkhorn, NE24.0 Little Blue, NE Big Blue, NE Neosho, KS Walnut, KS Verdigris, KS prior- 1980 [in] 1980- 1999 [in] 26.7 27.8 30.4 27.6 29.6 34.6 37.8 36.2 39.9 37.2 40.1 Increase % 11 7 9 9 10 8  P USDA-ARS-GRL

18. River name Mean annual streamflow Increase % Elkhorn, NE109886 Little Blue, NE 36916 Big Blue, NE 78739 Neosho, KS 256036 Walnut, KS 80135 Verdigris, KS168535 prior- 1980 [cfs] 1980- 1999 [cfs] 2046 428 1095 3494 1081 2283 QQ USDA-ARS-GRL

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

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

21. 11-yr moving average of annual runoff and precipitation depth Runoff [mm] Precipitation [mm] Year 19501960197019801990 2000 155 130 105 80 55 30 5 935 885 835 785 735 685 635 Runoff Precipitation USDA-ARS-GRL Little Washita River Watershed, OK

22. 150 125 100 75 50 25 0 650700750800850900950 Precipitation [mm] Runoff [mm] 11-yr moving average of annual runoff versus precipitation depth USDA-ARS-GRL Little Washita River Watershed, OK

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

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

25. Runoff [mm] Precipitation [mm] Year 1960197019801990 2000 700 600 500 400 300 1400 1300 1200 1100 1000 Runoff Precipitation 11-yr moving average of annual runoff and precipitation depth USDA-ARS-GRL Glover Watershed, OK

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

27. Retention Runoff Glover Watershed, OK

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

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

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

31. 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. USDA-ARS-GRL

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

33. 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. USDA-ARS-GRL

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

35. 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. USDA-ARS-GRL