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Estimates of Ground-Water Recharge in Minnesota

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Title: Estimates of Ground-Water Recharge in Minnesota


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 MethodTheory
6
Rorabaugh MethodComputation
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 CharacteristicsFinal
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 rechargepermeability 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 Regression
used decadal average going back through 1940.
inches
14
Evapotran-spiration (ET)
Shown is average ET. 1961-1990 Regression used
decadal average of growing degree days.
15
Regression Equation
Decadal averages for recharge and precipitation
were usedreduces 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 ?h
?h
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 gt
3.5 m
Bemidji
21
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
Unsaturated Zone Water 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
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 ?h 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-flux plane
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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