Montana Bureau of Mines and Geology Kevin Chandler Jon Reiten. AWRA October 6 th,2011

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1 Montana Bureau of Mines and Geology Kevin Chandler Jon Reiten AWRA October 6 th,2011

2 Funding for this modeling effort came from the RRG project Modeling Aquifer Response to Urban Sprawl, West Billings Area, Montana Sponsored by the Yellowstone Conservation District

3 Changes in The West Billings Area There was a 23% loss of irrigated lands between 1966 and 1999 (Olson and Reiten,2002) GWIC Wells in T1S R25E, West Billings Area Number of Recorded Wells

Goals for Modeling the West Billings Aquifers Models will be

2009. Transient flow models will be used to model changes in

4 Goals for Modeling the West Billings Aquifers Models will be used to represent steady state aquifer conditions in 2000 and in Transient flow models will be used to model changes in aquifer conditions with changes in land use recharge between and Transient flow models will be used to predict possible aquifer conditions resulting from future land use changes.

5 Modeled Area Billings N Laurel Billings Base Map, Montana NRIS

6 Terraces in West Billings Billings Terrace 3 Laurel Terrace 2 Terrace 1 From Olson and Reiten, 2002

7 Model Locations The three aquifer terraces, (Qa1,Qa2,and Qa3 (Gosling and Parshley, 1973; Lopez, 2000)) were split into two model areas. The Northern model includes the area from Big Ditch to BBWC, terrace 3, Qa3. The Southern model includes the area from BBWC to the Yellowstone River, terraces 1 and 2, Qa1 and Qa2.

8 Northern Model Boundary Grand Ave Central Billings Shilo Dr Neibauer 48th 64th 56th 80th 24th Laurel Airport Rd

9 Southern Model Boundary Hesper Neibauer 56th Shilo Dr 24th Danford 72nd

10 Well Used for Stratigraphy Modeling

11 Northern Model MODFLOW Grid Grand Ave Central Hesper 80th 24th

12 MODFLOW Grid Cell size 200 ft X 200 ft 43,506 active cells Surface area 20.8 mi² Vertical Magnification 20X

Aquifer Properties The hydraulic conductivity of the

ft/day range based on aquifer test results( Olson and

The hydraulic conductivity values in layer 2 of the

adjusted in the calibration process to values ranging

Specific yield values were initially set at 0.

13 Aquifer Properties The hydraulic conductivity of the terrace gravel aquifer was found to be in the ft/day range based on aquifer test results( Olson and Reiten, 2002). The hydraulic conductivity values in layer 2 of the model were varied using coverage polygons and were adjusted in the calibration process to values ranging from 50 to 200 ft/day. Specific yield values were initially set at 0.15 and were varied from to 0.10 during calibration to reflect the semi confining silty sand sediment cap which ranges from ft thick.

14 Recharge polygons for the Northern Model

15 Model calibration Model heads were calibrated using water level measurements collected monthly at 15 wells in the northern model area in and again in Surface water flow measurements on the major drains were used to calibrate drain flows from the model. Parameter estimation simulations (PEST) in GMS 7.0 were used during initial steady state model calibration. Hydrograph matching was used in transient model calibration.

16 Hydrograph Matching for Transient Model Calibration

17 Calibration to Surface Water Flows

18 Calibration to Surface Water Flows

19 June June Jan This is an animation of a 32 month transient simulation with current land use conditions.

20 June June Jan This is an animation of the head differences between a transient simulation with field irrigation on and a simulation were recharge on fields is reduced to precipitation only. The ditches and canals remain on an provide recharge.

21 June June Jan This is an animation of the head differences between a transient simulation of current conditions and a simulation with all irrigation turned off including all ditches and canals.

23 Model Applications Model simulations were run to predict the impact of flood water retention ponds on aquifer conditions as part of the West Billings flood prevention study. Model simulations were used in the site selection for a community water supply well for Yellowstone Boys and Girls Ranch which was needed to replace their contaminated well.

24 Sharptail Floodwater Retention Pond Changes to Aquifer Heads

25 Yellowstone Boys and Girls Ranch Feedlot

26 Questions?

27 References Olson, J. L., & Reiten, J. C. (2002). Hydrogeology of the West Billings Area: Impacts of Land use Changes on Water Resources. Montana Tech, Montana Bureau of Mines and Geology. Butte Montana: MBMG. Anderson, M. P., & Woessner, W. W. (1992). Applied Groundwater Modeling, Simulation of Flow and Advective Transport. San Diego, California: Academic Press, Inc. Weight, W. D., & Sonderegger, J. L. (2001). Manual Of Applied Field Hydrology. New York: McGraw hill.

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