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Estimates of Ground-Water Recharge in Minnesota

Estimates of Ground-Water Recharge in Minnesota. Research supported by the USGS, Office of Ground Water and DNR Waters. Dave Lorenz and Geoffrey Delin USGS Water Science Center of Minnesota. Study Objectives.

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Estimates of Ground-Water Recharge in Minnesota

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  1. Estimates of Ground-Water Recharge in Minnesota Research supported by the USGS, Office of Ground Water and DNR Waters Dave Lorenz and Geoffrey Delin USGS Water Science Center of Minnesota

  2. Study Objectives Quantify recharge to unconfined sand and gravel aquifers in Minnesota using multiple methods representing different time and spatial scales. Compare and contrast the results.

  3. Estimation Methods Used Multiple regression analysis relating recharge to precipitation, ET, and soils data (Regional Regression Recharge) Ground-water level fluctuation (water-table fluctuation) Unsaturated-zone water balance (zero-flux plane) Ground-water age dating

  4. Regional Regression Recharge Method Recharge based on the Rorabaugh method that estimates average recharge in a drainage basin from streamflow records.

  5. Rorabaugh Method—Theory

  6. Rorabaugh Method—Computation

  7. Stream Gaging Station Selection Criteria reviewed: length of record, common periods of record, missing data, size of watershed, (maximum of 3,000 mi2), and existence of control structures (dams or diversions). 40 stations selected based on these criteria

  8. Stream Gaging Stations Used in RORA Baseflow Recharge Analyses

  9. Landscape Characteristics Several landscape characteristics were considered originally: Soil characteristics; Percent sand, percent clay, porosity, bulk density, permeability, and specific yield. Other landscape characteristics: percent various classes of geologic deposits in basin, basin slope, stream slope, and percent lake area in basin.

  10. Landscape Characteristics—Final Decided to use specific yield (SY) as the landscape characteristic in the model: Direct measure of the capacity of the material to hold and release water under gravity. This is a linear property. That makes it possible to project back to the land surface. Highly correlated with other properties that affect recharge—permeability and hydraulic conductivity.

  11. Specific Yield

  12. Specific Yield Several methods to estimate SY were used. The method described in Rawls (1982) was used in the final regression equation. It uses percent sand, clay and organic matter. Data from STATSGO.

  13. Precipitation Shown is average precip. 1971-2000 Regressionused decadal average going back through 1940. inches

  14. Evapotran-spiration (ET) Shown is average ET. 1961-1990 Regressionused decadal average of growing degree days.

  15. Regression Equation Decadal averages for recharge and precipitation were used—reduces serial correlation between precipitation and recharge and smoothes out the variability in precipitation and recharge. Generalized least squares regression was used to account for the correlation between decadal data for each basin. Recharge = 14.25 + 67.63(SY) + 0.6459(P) - 0.02231(GDD*) GDD* is the minimum of GDD or 1350 degree days above 10 degrees celsius.

  16. Average Recharge through soils in Minnesota1971-2000

  17. Water-Table Fluctuation (WTF) Method Data from 38 wells equipped with data loggers at five different sites Temporal variability in recharge

  18. Water-Table Fluctuation Method Recharge = SY Δh Δh

  19. Multiple WTF Methods Utilized Graphical method RISE program (Rutledge, 2003) Master Recession Curve

  20. Correlation Between Graphical WTF Recharge and UZ Thickness 2003 data from 23 wells at 3 different sites Anomalously high recharge for UZ thicknesses > 3.5 m Bemidji

  21. 0-54 % under-estimation of the recharge: from daily to weekly measurement 18-60 % under-estimation of the recharge: from daily to monthly measurement No change in estimated recharge going from hourly to daily measure Hourly / daily Weekly (- 23%) (- 48%) Monthly Effects of Measurement Interval on WTF Recharge Estimates Estimated recharge, cm/yr Recharge estimates based on WTF method (RISE program) Measurement interval, days 1993 datalogger data from MSEA well R2 near Princeton, MN

  22. Unsaturated-Zone Water Balance (zero-flux plane) Method Bemidji, Williams Lake, andPrinceton MSEA sites Temporal variability in recharge

  23. UnsaturatedZoneWater Balance Method Recharge, percent of precipitation Bemidji well 981 Bemidji well 9015 MSEA well R1 MSEA well R2 Bemidji well 9014 Williams Lake site Lowland Sites Upland Sites

  24. Ground-Water Age Dating Method Average recharge, spatial variability

  25. Ground-Water Age Dating Method Recharge = vertical GW velocity x porosity Example from Princeton MSEA site using CFC data SF6 and 3H-3He techniques can also be used; min. time resolution of ~1 year BP From Delin et al. (2000)

  26. Method Comparison

  27. Shallow depth to water table results in WTF recharge rates being too large for Glacial Ridge, Des Moines River, and Williams Lake sites Similarity in recharge rates for some methods at some sites Comparison of Average Recharge Rate Computed at Each Site Of the WTF approaches, MRC estimates generally are the greatest; RISE program lowest WTF Method Pretty good agreement between regional estimates at most sites Other site-specific Methods Regional Methods Methods are scale dependent

  28. Almostthe end

  29. Statewide Analysis WTF Methods Datalogger site (36 wells total) Glacial Ridge Bemidji Williams Lake 45 wells with weekly data available from DNR database 45 wells with weekly data available from DNR database MSEA Des Moines River

  30. Graphical Method Manual method for estimating recharge. Developed in the late 1950s. Baseline recession that would have occurred in the absence of recharge projected to the time of peak in the hydrograph. The value of Δh determined manually.

  31. Graphical Calculation for WTF Method From Delin (1990)

  32. RISE Program Simple program that calculates the daily rise of water level in an observation well. The program makes no allowance for the baseline recession that would have occurred in the absence of recharge. The input data can be read right out of NWIS Web or can be created from data logger files. Rutledge (2003) electronic communication

  33. RISE Calculation for WTF Method From Delin (1990)

  34. Master Recession Curve Method First step is to define a Master Recession Curve from “typical” recessions for a well. This is accomplished by a nonlinear regression that estimates the recession rate and recession asymptote. Other methods for estimating a master recession curve have also been developed. Program calculates the daily recession of water level in an observation well and the rise from the difference between the theoretical recession and the actual water level.

  35. MRC Calculation for WTF Method From Delin (1990)

  36. Recharge Estimates - WTF Method Williams Lake examples: Precipitation and recharge in cm/yr 16% 18% 11 % 13% 9% 10% 91% 120% 101% UZ thickness: 5 m 9 m 2 m

  37. Unsaturated Zone Water Balance Zero-fluxplane Time From Delin and Herkelrath (in press)

  38. Wells Sampled for SF6GW age dating.Also used CFCs for dating Glacial Ridge Bemidji Williams Lake Perham 22 wells sampled for SF6, including 2 nests EXPLANATION MSEA SF6 sample site (18 this study) Other GW age-dating site (6) Prairie Island Rock River Des Moines River

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