Contribution of Irrigation Seepage to Groundwater-Surface Water Interactions on the Eastern Snake River Plain

Transcription

1 Contribution of Irrigation Seepage to Groundwater-Surface Water Interactions on the Eastern Snake River Plain Rob Van Kirk, HSU Department of Mathematics BSU Geosciences Department, November 30, 2011

2 Collaborators and funders Current USDA-funded Project Brian Apple, Humboldt State University Dr. J. Mark Baker, Humboldt State University Dr. Yvonne Everett, Humboldt State University Dr. Brad Finney, Humboldt State University Lora Liegel, Humboldt State University Kimberly Peterson, Humboldt State University Dr. Steve Steinberg, Humboldt State University Dale Swenson, Fremont-Madison Irrigation District Kim Ragotzkie, Henry s Fork Foundation Amy Verbeten, Friends of the Teton River Other Collaborators Kevin Boggs, University of Idaho Dr. Gary Johnson, University of Idaho Funders National Science Foundation U.S. Department of Agriculture

3 Outline Study areas and hierarchy of nested spatial scales 1. Teton Valley tributary basin (400 km 2 ) 2. Henry s Fork upper part of Plain (8,000 km 2 ) 3. Upper Snake R. entire aquifer (93,000 km 2 ) Hydrogeology of Snake River Plain Statement of problem Research approach Results Ecological consequences Conclusions and recommendations

4 Eastern Snake River Plain and Study Basins

5 N 50 miles Beartooth Plateau Centennial Mts. Yellowstone Lake Great Salt Lake Bear Lake

6 N 50 miles Plate Motion 1 in/year Hot Spot

7 N 50 miles Uplift Zone Hot Spot Bow Wave Uplift Zone

8 Elevation (feet) Precipitation (inches) Elevation-precipitation relationship across the hotspot. N 50 miles 12,000 10,000 8,000 Old Faithful Hayden Valley Beartooth Plateau Elevation Precipitation ,000 4,000 Snake R Plain Lamar Valley Billings , Distance (miles) 0

9 N 50 miles Headwaters of a Continent Yellowstone Snake Bear

10 Upper Snake River Water System Drainage area: 35,800 mi 2 (93,130 km 2 ) Irrigated area: 2.4 M acres (9750 km 2 ) 9 major storage reservoirs; capacity 4 M a-f (5 x 10 9 m 3 )

11 Eastern Snake Plain Aquifer (ESPA) Boggs et al., 2010, J. Am. Water Res. Assoc. Water budget and water rights accounting close below Thousand Springs.

12 Water Table Height (ft) Problem 1: Decline in Groundwater Levels /1/ /1/ /1/ /1/ /1/ /1/2001 Groundwater level in a monitoring well on the ESPA.

13 Discharge - Cubic Meter per Second Problem 2: Decline in Aquifer Discharge Water Year Thousand Springs Discharge

14 Research Approach Model flow through linked surface-ground system, including: Diversions from streams into canal system Seepage from canals Seepage from stream channels Seepage due to irrigation application in excess of crop ET Surface return from irrigation system Returns to surface system from aquifers Analyze changes in irrigation practices Estimate water budgets Conduct analyses at multiple spatial scales: Small tributary basins(teton Valley) Intermediate-scale watershed (Henry s Fork) Entire system (Upper Snake River/Eastern Snake Plain Aquifer)

15 Henry s Fork Watershed Mean ann. precip.: 28.2 inches Min. elevation: 4,820 ft. Max. elevation: 11,400 ft. Canal-irrigated area: 250,000 ac. Canal length: 475 miles Annual water supply: 2.5 M a-f Annual diversion: 1.2 M a-f

16 Surface lithology of Henry s Fork Precambrian Paleozoic and Mesozoic sedimentary Cenozoic silicic volcanics from Yellowstone hotspot explosive eruptions Quaternary basalts Quaternary alluvium and glacial drift Source: Bayrd 2006 M.S. Thesis, Idaho State University

17 Field work to measure canal and stream channel loss rates and geometry for model parameterization.

18 Changes in Irrigation Practices Flood irrigation Sprinkler irrigation

19 Conversion from flood to sprinkler But, almost all conveyance still occurs in unlined canals.

20 Annual Volume (acre-feet) Groundwater pumping began in 1950s 350, , , , , ,000 50, Year Annual volume of groundwater pumped by A&B Irrigation District But, GW pumping does not occur in all locations.

21 Diversion (cfs) 30-year Mean Canal Hydrograph Teton Valley Application Seepage Crop ET Canal Seepage Canal/Sprinkler ET Surface Return Oct 1-Nov 1-Dec 1-Jan 1-Feb1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep Date

22 Diversion (acre-feet) Canal Budget by Year Teton Valley 160, , , ,000 Application Seepage Crop ET Canal Seepage Canal/Sprinkler ET Surface Return 80,000 60,000 40,000 20, Year

23 Diversion (cfs) 30-year Mean Canal Hydrograph HF Application Seepage Crop ET Canal Seepage Canal/Sprinkler ET Surface Return Oct 1-Nov 1-Dec 1-Jan 1-Feb1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep Date

24 Diversion (acre-feet) Canal Budget by Year Henry s Fork 1,600,000 1,400,000 1,200,000 Application Seepage Crop ET Canal Seepage Canal/Sprinkler ET Surface Return 1,000, , , , , Year

25 Net Gain (acre-feet/yr) River reach gains Henry s Fork Watershed 700, , , ,000 Lower HF & Teton HF Ashton-StA Teton Valley 300, , , ,

26 Analysis of Reach Gains in Henry s Fork Watershed Reach gains depend strongly on irrigation recharge, which depends on diversion

27 Annual aquifer recharge, acre-feet Natural Flood Actual Sprinkler Pipeline GW recharge under modeled scenarios, Teton Valley Pipeline scenario assumes 100% irrigation efficiency

28 Effect on GW elevations: Teton Valley

29 Distribution of Surface Withdrawals Does this scale up to entire Upper Snake? 100% 90% 80% 70% 60% Return via Surface Flow Evaporative Loss Crop Evapotranspiration Return via Groundwater 50% 40% 30% 20% 10% 0% Teton Valley 0.92 M a-f/yr Henry's Fork 1.2 M a-f/yr Upper Snake 8.7 M a-f/yr Water budget for surface water withdrawals

30 Distribution of Recharge Sources Does this scale up to entire Upper Snake? 100% 90% 80% 70% Direct Precipitation Stream Seepage/Tributary Underflow Irrigation Seepage 60% 50% 40% 30% 20% 10% 0% Teton Valley 0.95 M a-f/yr Henry's Fork 1.2 M a-f/yr Upper Snake 9.0 M a-f/yr Distribution of Recharge Sources to Valley Aquifers

31 Prediction of Thousand Springs discharge from irrigation seepage Modeling efficiency: 75% Boggs et al. 2010, JAWRA

32 Ecological Consequences: hydrologic alteration Modeled Teton River flow: irrigation has decreased peak flow and increased base flow

33 Ecological Consequences: hydrologic alteration Modeled Teton River flow, dimensionless hydrographs Measure GW influence by maximum/minimum ratio

34 Teton R. Maximum/minimum discharge ratio

35 1-Oct 1-Dec 1-Feb 1-Apr 1-Jun 1-Aug Discharge (percent of annual) Depth/bankfull width HF at Rexburg Warm River Trail Creek Groundwater influence and stream channel morphology Distance/bankfull width Stream channel complexity increases with hydrograph max/min ratio (Bayrd 2006) 1.2% 1.0% 0.8% 0.6% 0.4% 0.2% 0.0% HF at Rexburg Warm River Trail Creek

36 Percent cutthroat trout Max/min Ratio and Trout Species Composition Nonnative rainbow trout displace native cutthroat when max/min ratio is low. 100% 80% 60% South Fork Snake Teton River Linear (South Fork Snake) Linear (Teton River) 40% 20% 0% Maximum/minimum ratio during year of spawn

37 BUT, irrigation seepage maintains

38 Some conclusions and recommendations Irrigation patterns have driven groundwater-surface water interactions in upper Snake Basin since late 19 th century. Irrigation has transformed upper Snake hydrologic regimes from snowmeltdominated to GW-dominated. Native species and ecosystems have been replaced by nonnatives, but Ecosystem services provided by irrigation-dependent groundwater and wetlands are valued, if poorly understood and under-appreciated. Increases in irrigation efficiency have reduced GW-associated resources, including water supply for downstream users. Irrigation remains single largest source of aquifer recharge. Water management for all uses and values must account for groundwatersurface water interactions and treat both components equally Beware of unintended down-gradient and downstream consequences of wellintentioned water conservation measures.

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