1. Alabama Irrigation Initiative Environmental Meeting 10/31/2008

2. Ecological Approach Original approach was to statistically analyze volumetric withdrawals. Ecologically, the area of inundation is potentially just as important as volumetric flow Revised approach to analyze total flood plain affected by withdrawals

3. Center for Freshwater Studies Area of Interest – Sipsey River Swamp

4. Approach Historic Discharge Data USGS Rating Curves Gauge Height (elevation) Area of inundation before withdrawals (GIS Model) Synthetic Withdrawal & adjusted discharge USGS Rating Curve Adjusted gauge height (elevation) Adjusted area of inundation (GIS Model) Statistical analysis comparing inundation area before and after withdrawals

5. USGS Historic Data & Rating Curves

6. Rating Curve Rating curve based on USGS data Relates discharge (known) to gage height (needed) USGS provides table of Discharge versus Gage Height Estimated gage height in region of interest (approximately 4.5 miles downstream of Elrod station) Interpolation routine for Rating data is statistically accurate. Currently have rating data 11 & 12 (1995 – present).

7. Area of Interest – GIS Model

8. GIS Area Model

9. ArcGIS Area Data Similar to the Rating Curve table, the “Area Curve” table is used to estimate the area of inundation from a “synthetic” withdrawal. The interpolation routine for area data is accurate.

10. Statistical Analysis Method The Wilcoxon Rank- Sum test is used –The Wilcoxon rank-sum test is a nonparametric alternative to the two sample t-test –The null hypothesis is that the means of the two samples are statistically equal. –If the shift is greater than the confidence level (α). For a two-tailed test (A=B versus A≠B), confidence level is α/2

11. Statistical Analysis Spreadsheet 365 vs. 120 day analysis

12. 2001 365-day Analysis Before withdrawal in orange (burnt?) After withdrawal in blue (39.5% of discharge withdrawn) This was the highest flow day during withdrawal period (January through April)

13. 2001 120-day Analysis Before withdrawal in orange… After withdrawal in blue (16.7% of discharge withdrawn) This was the highest flow day during withdrawal period (January through April)

14. Approximate Area before/after Synthetic Withdrawal Withdrawal set at 12% of discharge. That equates to 44225 acre-ft Withdrawal period is Jan-April 1995 (Rating Curve 11)

15. YearTotal Withdrawal (acre-ft) 199544,225 199650,466 199745,025 199853,154 199947,435 200029,458 200165,731 200244,230 200355,296 200469,879 200531,039 200660,150 200735,963 200841,419 Average=48,105 Max=69,879 Min=29,458

16. Scaling Up to the AL and TN Rivers Percent WithdrawanYearTotal Acre Feet 12.00%19951,429,140 12.50%19962,059,965 13.00%19971,891,070 10.50%19982,163,854 11.00%1999937,516 8.70%2000541,633 16.65%20012,419,211 15.70%20021,138,976 12.90%20031,543,614 17.85%20041,202,672 11.30%20051,395,497 15.05%20061,239,750 19.25%2007862,494 19.90%2008960,040 Average=1,413,245 Max=2,419,211 Minimum=541,633 Percent WithdrawanYearTotal Acre Feet 12.00%19951,533,024 12.50%19962,163,887 13.00%19972,296,935 1998 1999 8.70%2000643,248 16.65%20011,347,570 15.70%20021,584,510 12.90%20031,841,181 2004 11.30%20051,344,564 2006 2007 2008 Average=1,594,365 Max=2,296,935 Minimum=643,248 Alabama River - Claiborne Tennessee River - Whitesburg

17. Perspective The minimum available water from the AL and TN rivers could irrigate ~1,000,000 acres. That is approximately ~3% of the total area of Alabama

18. Conclusions/Issues Basing withdrawals on the cyclic inundation of a floodplain attempts to take the river ecology into account The method shows that statistically insignificant fractions are available that are within the total, annual variability of the river Each river is unique and analysis may have to be modified to account for different channel/floodplain characteristics