A Century of Precipitation Trends in the Mississippi Delta Region and Implications for Agroecosystem Management

Transcription

1 A Century of Precipitation Trends in the Mississippi Delta Region and Implications for Agroecosystem Management LINDSEY YASARER, RESEARCH HYDROLOGIST WATER QUALITY AND ECOLOGY RESEARCH UNIT USDA-ARS NATIONAL SEDIMENTATION LABORATORY APRIL 12, 2017 MISSISSIPPI WATER RESOURCES CONFERENCE

2 WHAT IS NORMAL? 100-Year 24 Hour Rainfall (inches)

3 REGIONAL PERSPECTIVE: EXTREME PRECIPITATION IN THE SOUTHEAST 100-Year 24 Hour Rainfall (inches) MS Delta: 8 10 inches Occurrence of 1-day, 1 in 5-year extreme precipitation event; based on daily COOP data from long term stations in NCDC-GHCN data set, only including stations with less than 10% missing data; ; trend is statistically significant From: Scenarios for Climate Assessment and Adaptation (

4 WHAT DO OBSERVATIONS TELL US ABOUT CHANGES IN EXTREME PRECIPITATION? Trends in the Southeast Percent increases in amount of precipitation falling in very heavy events (1%; ); National Climate Assessment Percent change in amount of precipitation falling in very heavy events compared to averages (1%; ); National Climate Assessment

5 WHAT ARE THE HISTORICAL AND PROJECTED CLIMATE TRENDS FOR THE MISSISSIPPI DELTA? EXPLORATORY ANALYSIS OF TRENDS IN HISTORICAL AND PROJECTED: ANNUAL RAINFALL TOTALS CASE STUDY: WATERSHED SIMULATION RESULTS WITH PROJECTED CLIMATE IMPLICATIONS FOR AGROECOYSTEMS MONTHLY RAINFALL TOTALS RAINFALL INTENSITY Photo by John Montfort Jones: flatoutdelta.com

6 LONG-TERM PRECIPITATION TRENDS IN MS DELTA NORTHERN DELTA 11MM/DECADE TREND FROM MEAN: 1325MM KENDALL S TAU: 0.097, P=0.11 SOUTHERN DELTA 14MM/DECADE TREND FROM MEAN: 1340MM KENDALL S TAU: 0.14, P=0.02 Data from NOAA Climate Division Database Figures from Climate at a Glance:

7 RAINFALL VARIABILITY INDEX RVI = RVI > 1 = Very wet 0.5 < RVI < 1 = Wet -0.5 < RVI < 0.5 = Normal -1 < RVI < -0.5 = Dry RVI < -1 = Very Dry Data from NOAA Climate Division Database:

8 TRENDS IN MONTHLY RAINFALL: CD 1: UPPER DELTA Kendall's Tau P-value January February March April May June July August September October November December CD 4: LOWER DELTA Kendall's Tau P-value January February March April May June July August September October November December Data from NOAA Climate Division Database:

9 DATA USED TO PROVIDE SPATIAL PERSPECTIVE ON PRECIPITATION TRENDS DATA SOURCE PROJECTED CLIMATE Data from the U.S. Climate Resilience Toolkit provided by NOAA - Observed data based on GHCN-daily stations and PRISM - Projected data from CMIP5 Bias-corrected Constructed Analogs method (BCCA) Global Climate Models Vuuren et al The Representative concentration pathways: an overview. Climatic Change 109:5-31.

10 TRENDS IN MEAN DAILY PRECIPITATION: HISTORICAL AND PROJECTED

11 TRENDS IN OCTOBER MEAN DAILY PRECIPITATION HISTORICAL PROJECTED Images from: climate-explorer2

12 TRENDS IN DAYS WITH PRECIPITATION > 1IN (25.4MM) INDICATOR OF INCREASING INTENSITY

13 DAYS WITH PRECIPITATION > 1IN (25.4MM) HISTORICAL PROJECTED Images from: /climate-explorer2

14 IMPLICATIONS FOR AGROECOSYSTEM MANAGEMENT INCREASING FALL PRECIPITATION: MORE DIFFICULT TO HARVEST CROPS MORE RUNOFF WHEN FIELDS ARE NOT PROTECTED INCREASING INTENSITY: FASTER AND LARGER QUANTITIES OF SURFACE RUNOFF LARGER SEDIMENT TRANSPORT CAPACITY STREAMBANK EROSION FLASHIER SYSTEMS MORE FLOODING DITCH AND BIOLOGICAL TREATMENT SYSTEMS ARE LESS ABLE TO PROCESS NUTRIENTS LIKELY LESS SOIL MOISTURE HIGHER RAINFALL EROSIVITY

15 CASE STUDY: BEASLEY LAKE WATERSHED Article in Press: Yasarer, L.M.W., R. Bingner, J. Garbrecht, M. Locke, R. Lizotte, H. Momm, and P. Busteed. Climate change impacts on runoff, sediment, and nutrient loads in an agricultural watershed in the Lower Mississippi River Basin. Applied Engineering in Agriculture In press.

16 WHAT ARE THE PROJECTED CLIMATE CONDITIONS FOR BEASLEY LAKE WATERSHED ( ? CMIP5 15GCM Ensemble Data, Representative Concentration Pathway 8.5

17 WATER QUALITY LOAD DISTRIBUTIONS CHANGES IN THE MEDIAN: RUNOFF: 9.6% DECREASE (P=0.004) TSS: 12% INCREASE (P=0.03) TN: 9.6% INCREASE (P=0.17) TP: 9.2% INCREASE (P=0.04) Runoff TSS TN TP

18 HIGHER CONCENTRATIONS CAUSED BY AN INCREASE IN RAINFALL EROSIVITY HISTORICAL SIMULATED R = 7181 R is average annual total of storm erosivity values PROJECTED SIMULATED R = 7693 P=0.09

19 CAN AGRICULTURAL CONSERVATION PRACTICES REDUCE WATER QUALITY IMPACTS FROM CLIMATE CHANGE? Simulated 5 management regimes: Red: Conventional tillage Orange: Reduced tillage Yellow: No tillage Green: Double crop winter wheat and soybean Turquoise: Cover crop in winter

20 CONSERVATION PRACTICES WILL BECOME MORE CRITICAL IN A CHANGING CLIMATE Evidence in historical record for a positive, significant change in precipitation for lower Delta region, especially in the fall. Precipitation intensity may be increasing in Delta region. Projected precipitation shows no significant change overall to decreasing trend in the lower Delta. Future climate is uncertain, but rainfall intensity and erosivity is likely to increase. Conservation Practices Vulnerability to climate Case Study: Across a range of potential conditions conservation practices such as no till and cover crops reduced TSS, TN, and TP below historical levels.

21 THANKS! LINDSEY MW YASARER RESEARCH HYDROLOGIST USDA AGRICULTURAL RESEARCH SERVICE NATIONAL SEDIMENTATION LABORATORY WATER QUALITY AND ECOLOGY RESEARCH UNIT Article in Press: Yasarer, L.M.W., R. Bingner, J. Garbrecht, M. Locke, R. Lizotte, H. Momm, and P. Busteed. Climate change impacts on runoff, sediment, and nutrient loads in an agricultural watershed in the Lower Mississippi River Basin. Applied Engineering in Agriculture In press.

22 EXTRA SLIDES

23 WATERSHED LAYOUT AND RUNOFF SIMULATION Conditions: 2008 land-use and management; all cropland is soybean Yuan et al. 2008

24 HOW DOES PROJECTED CLIMATE AFFECT WATER QUALITY LOADS FROM AN AGRICULTURAL WATERSHED IN THE DELTA? METHODS: ANNAGNPS COMPONENTS: SCS CURVE NUMBER DAILY RUNOFF RUSLE GENERATES DAILY SHEET AND RILL EROSION TOPAGNPS GENERATES CELL AND STREAM NETWORK

25 WHAT ARE THE PROJECTED CLIMATE CONDITIONS FOR BEASLEY LAKE WATERSHED? P<0.001 P<0.001 P=0.65

26 RUNOFF DECREASED, BUT NUTRIENT LOADS INCREASED?

27 TRENDS IN RAINFALL INTENSITY SIMPLE DAILY INTENSITY INDEX: RATIO OF ANNUAL TOTAL PRECIPITATION TO THE NUMBER OF WET DAYS (> 1MM)

28 HISTORICAL AND PROJECTED CLIMATE CLIMATE DIVISION DATA PROJECTED DATA FROM THE CMIP5 DATASET Annual Precipitation [mm] Annual Average Maxium Temperature (C) Beasley Lake CD Projected Minimum 32 Projected Maximum Average of 15 GCMs Beasley Lake CD Projected Minimum Projected Maximum Average of 15 GCMs