Estimates of Ground-Water Estimates of Ground-Water Recharge in MinnesotaRecharge in Minnesota

Dave Lorenz and Geoffrey DelinUSGS Water Science Center of Minnesota

Research supported by the USGS, Office of Ground Waterand DNR Waters

Study ObjectivesStudy 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.

Estimation Methods UsedEstimation Methods UsedMultiple 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

Regional Regression Recharge Regional Regression Recharge MethodMethod

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

Rorabaugh Method—TheoryRorabaugh Method—Theory

Rorabaugh Method—ComputationRorabaugh Method—ComputationL

OG

AR

ITH

M O

F S

TR

EA

MF

LO

W

PEAK 1

PEAK 2

RECESSION RATE = K

TIM

E O

F P

EA

K 1

BE

GIN

OF

GW

RE

CE

SS

ION

TIM

E O

F P

EA

K 2

Stream Gaging Station SelectionStream 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

Stream Stream Gaging Gaging Stations Stations Used in Used in RORA RORA

Baseflow Baseflow Recharge Recharge AnalysesAnalyses

Landscape CharacteristicsLandscape 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.

Landscape Characteristics—Final 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.

Specific Yield Specific Yield

Specific Yield 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.

Shown is average precip. 1971-2000

Regression used decadal average going back through 1940.

PrecipitationPrecipitation

inches

Shown is average ET. 1961-1990

Regression used decadal average of growing degree days.

Evapotran-Evapotran-spiration (ET)spiration (ET)

Regression EquationRegression EquationDecadal 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.

Average Average Recharge Recharge through through soils in soils in

MinnesotaMinnesota1971-20001971-2000

Water-Table Water-Table Fluctuation (WTF) Fluctuation (WTF)

MethodMethod

Data from 38 wells equipped with Data from 38 wells equipped with data loggers at five different sitesdata loggers at five different sites

Temporal variability in rechargeTemporal variability in recharge

Water-Table Fluctuation MethodWater-Table Fluctuation Method

Δh

Recharge = SY Δh

Multiple WTF Multiple WTF Methods UtilizedMethods Utilized

Graphical method

RISE program (Rutledge, 2003)

Master Recession Curve

Correlation Between Graphical Correlation Between Graphical WTF Recharge and UZ WTF Recharge and UZ

ThicknessThickness2003 data 2003 data from 23 from 23 wells at 3 wells at 3 different different sitessites

0

10

20

30

40

50

60

70

0246810

Unsaturated zone thickness, meters

Rec

har

ge,

cm

/yr

Williams Lake

Glacial Ridge

Anomalously high recharge for UZ

thicknesses > 3.5 m

Bemidji

Effects of Measurement Interval on Effects of Measurement Interval on WTF Recharge EstimatesWTF Recharge Estimates

1993 datalogger data from MSEA well R2 near Princeton, MN1993 datalogger data from MSEA well R2 near Princeton, MN

4

5

6

7

8

9

10

11

12

13

14

0 5 10 15 20 25 30 35

Measurement frequency, days

Est

imat

ed r

ech

arg

e, c

m/y

r

Hou

rly /

daily

No change No change in estimated in estimated recharge recharge going from going from hourly to hourly to daily daily measuremeasure

Recharge estimates based on WTF method (RISE program)

0-54 % under-0-54 % under-estimation of estimation of the recharge: the recharge: from daily to from daily to weekly weekly measurementmeasurement

Weekly

(- 23%)

18-60 % under-18-60 % under-estimation of estimation of the recharge: the recharge: from daily to from daily to monthly monthly measurementmeasurement

Mon

thly(- 48%)

Measurement interval, days

Est

imat

ed r

ech

arg

e, c

m/y

r

Unsaturated-Zone Water Unsaturated-Zone Water Balance Balance

(zero-flux plane) (zero-flux plane) MethodMethod

Bemidji, Williams Lake, andBemidji, Williams Lake, andPrinceton MSEA sitesPrinceton MSEA sites

Temporal variability in rechargeTemporal variability in recharge

UnsaturatedUnsaturated ZoneZone Water Balance MethodWater Balance Method

Lowland Sites

0

10

20

30

40

50

60

70

Upland Upland Upland

MSEA R2 Bemidji 9014 Williams Lake

0

10

20

30

40

50

60

70

Lowland Lowland Lowland

Bemidji 981 Bemidji 9015 MSEA R1

Rec

har

ge

as a

per

cen

t o

f p

reci

pit

atio

n

Upland Sites

Bemidji well 981

Bemidji well 9015

MSEA well R1

MSEA well R2

Bemidji well 9014

Williams Lake site

Rec

har

ge,

per

cen

t o

f p

reci

pit

atio

n

Ground-Water Age Ground-Water Age Dating MethodDating Method

Average recharge, spatial variabilityAverage recharge, spatial variability

Ground-Water Age Dating MethodGround-Water Age Dating MethodD

ep

th b

elo

w w

ate

r ta

ble

, in

met

ers R1 - Low land Site

CCl F -model recharge age, in years before the sampling date

2 2

V v o = 0.7 0.2 m /yr+

R1-B

0 10 20 30 40 5012

11

10

9

8

7

6

5

4

3

2

1

0

1993, 7°C

1994, 7°C

1993, 9°C

1994, 9°C

W ater table (Z = 9.5 m)

R1-10

From Delin et al. (2000)

Example from Example from Princeton MSEA site Princeton MSEA site using CFC datausing CFC data

Recharge = Recharge = vertical GW velocity vertical GW velocity x porosityx porosity

SFSF66 and and 33H-H-33He He

techniques can techniques can also be used; min. also be used; min. time resolution of time resolution of ~1 year BP~1 year BP

Method Method ComparisonComparison

0

10

20

30

40

50

60G

laci

alR

idg

e

Des

Mo

ines

Riv

er

Wil

liam

sL

ake

Bem

idji

MS

EA

Selected USGS Research Site

Ave

rag

e g

rou

nd

-wat

er r

ech

arg

e, c

m/y

r

RISE program

Graphical

MRC

UZWB

GW age dating

RRR Method

GW flow model

35% of precipitation

Comparison of Average Recharge Comparison of Average Recharge Rate Computed at Each SiteRate Computed at Each Site

Shallow depth to Shallow depth to water table results water table results in WTF recharge in WTF recharge rates being too large rates being too large for Glacial Ridge, for Glacial Ridge, Des Moines River, Des Moines River, and Williams Lake and Williams Lake sitessites

Pretty good Pretty good agreement agreement between regional between regional estimates at most estimates at most sitessites

WTF Method

RISE program

Graphical

GW flow model

35% of precipitation

MRC

UZWB

GW age dating

RRR Method

Other site-specific Methods

Regional Methods

Similarity in Similarity in recharge rates for recharge rates for some methods at some methods at some sitessome sites

Of the WTF approaches, Of the WTF approaches, MRC estimates generally MRC estimates generally are the greatest; RISE are the greatest; RISE program lowestprogram lowest

Methods are scale dependentMethods are scale dependent

AlmostAlmostthe the endend

Statewide Statewide Analysis Analysis

WTF WTF MethodsMethods

45 wells with weekly

data available

from DNR database

45 wells with weekly

data available

from DNR database

Datalogger site (36 wells total)

Bemidji

Williams Lake

Des Moines River

MSEA

Glacial Ridge

Graphical MethodGraphical 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.

Graphical Calculation for WTF MethodGraphical Calculation for WTF Method

From Delin (1990)

RISE ProgramRISE 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

RISE Calculation for WTF MethodRISE Calculation for WTF Method

From Delin (1990)

Master Recession Curve MethodMaster 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.

MRC Calculation for WTF MethodMRC Calculation for WTF Method

From Delin (1990)

Recharge Estimates - WTF MethodRecharge Estimates - WTF Method

Williams Lake examples: Williams Lake examples: PrecipitationPrecipitation and and rechargerecharge in in cm/yrcm/yr

UZ thickness: 5 m 9 m 2 mUZ thickness: 5 m 9 m 2 m

16% 18% 11 % 13% 9% 10% 91% 120% 101%

Unsaturated Zone Water Balance Unsaturated Zone Water Balance

From Delin and Herkelrath (in press)

Time

Zero-flux plane

Wells Wells Sampled Sampled for SFfor SF66

GW age GW age dating.dating.

Also used Also used CFCs for CFCs for

datingdating

22 wells sampled for

SF6, including

2 nests

SF6 sample site (18 this study)Other GW age-dating site (6)

Bemidji

Williams Lake

Des Moines River

EXPLANATIONMSEA

Glacial Ridge

Rock River

Perham

Prairie Island