The Contribution of Irrigation Seepage to Groundwater-Surface Water Interactions on the Snake River Plain, Idaho

Transcription

1 The Contribution of Irrigation Seepage to Groundwater-Surface Water Interactions on the Snake River Plain, Idaho Rob Van Kirk, HSU Department of Mathematics HSU Geology Department Colloquium, March 21, 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 Steve Trafton, 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 Hot Spot History 17 ma 10 ma 4 ma 1 ma Graphics from digital atlas of Idaho.

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

9 In the interior West, precipitation depends on elevation.

10 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

11 N 50 miles Headwaters of a Continent Yellowstone Snake Bear

12 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

13 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 )

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

15 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.

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

17 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)

18 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: 463 miles Annual water supply: 2.5 M a-f Annual diversion: 1.2 M a-f

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

20 Changes in Irrigation Practices Flood irrigation Sprinkler irrigation

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

22 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.

23 Discharge, cfs 30-year Mean Canal Hydrograph Teton Valley Delivery > Crop ET Crop ET Canal GW Recharge Canal ET Surface Return Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep Date

24 Annual volume (acre-feet) 140, , ,000 Canal Budget by Year Teton Valley Delivery > Crop ET Crop ET Canal GW Rchg. Canal ET SurfRet 80,000 60,000 40,000 20, Year

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

26 Mean annual volume (acre-feet) 300, , , , ,000 50,000 Crop ET Application Seepage Canal Seepage Stream Seepage Channel/riparian ET Surface Flow 0 Natural Flood Actual Sprinkler Pipeline Scenario Mean water budget for modeled scenarios in Teton Valley

27 Discharge, cfs 30-year Mean Canal Hydrograph HF Delivery > Crop ET Crop ET Canal GW Recharge Canal ET Surface Return 0 1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep Date

28 Annual volume (acre-feet) Canal Budget by Year Henry s Fork 1,600,000 1,400,000 1,200,000 Delivery > Crop ET Crop ET Canal GW Rchg. Canal ET Loss Surface Return 1,000, , , , , Year

29 Annual reach gain (acre-feet) River reach gains in lower Teton and HF 600, , ,000 Teton and HF St. A to Rexburg HF Ashton to St. A 300, , , , Year

30 Water Budget for Henry s Fork Surface Diversions Surface return in basin, 65,000 Other ET + GW outflow, 327,000 GW Return in basin, 230,000 Calculated basin outflow as GW, 224,000 Calculated crop ET, 312,000 Total diversion= 1,200,000 a-f

31 Water Budget for Henry s Fork Surface Supply: a-f Calculated basin outflow as GW, 224,000 Reservoir + Canal ET, 15,000 Other ET + GW outflow, 327,000 Calculated Surface-Irrigated Crop ET, 312,000 Basin surface outflow, 1,666,000 Total surface supply = 2,544,000 a-f

32 Does this scale up to entire Upper Snake? Volume (million acre-feet) Inflow Withdrawals Surface withdrawal in Water District All other surface/ground withdrawals 1.60 Groundwater withdrawals from ESPA 1.20 TOTAL Outflow Inflow withdrawal 1.02 Irrigation return via ESPA 4.00 Other irrigation return 2.59 Subtotal (outflow at King Hill) 7.61 Irrigation consumptive use 3.71 TOTAL Change in ESPA storage = inflow - outflow Estimates based on USGS, USBR, and IDWR data

33 ESPA Annual Water Budget: Mean Volume (million acre-feet) Inflow Irrigation seepage 4.0 Tributary underflow and river seepage 2.2 Direct precipitation 0.7 TOTAL 6.9 Outflow Thousand Springs discharge 4.0 Spring discharge: Blackfoot to Neeley 1.9 Pumping 1.2 TOTAL 7.1 Change in storage = inflow - outflow -0.2 Based on Johnson et al. 1999, J. American Water Resources Assoc.

34 Prediction of Thousand Springs discharge if canal seepage was ONLY source of recharge Modeling efficiency: 75%

35 1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep Discharge (percent of annual) Ecological Consequences: hydrologic alteration 1.0% 0.8% 0.6% Natural Sprinkler Flood 0.4% 0.2% 0.0% Modeled Teton River flow: irrigation has decreased peak flow and increased base flow, best measured by maximum/minimum ratio

36 Maximum/minimum discharge ratio Maximum/minimum discharge ratio Natural Sprinkler Flood Nat Reg Flood Model Reg 19

37 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 Max/min ratio 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

38 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

39 BUT, irrigation seepage maintains

40 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. Canal system remains alargest source of aquifer recharge. Water management for all uses and values must account for groundwatersurface water interactions and treat both components equally (conjunctive management). Beware of unintended down-gradient and downstream consequences of wellintentioned water conservation measures.

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