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Page 1 of 19
Appendix 2: Hydrometeorology and Hydroclimatology of Baseflow
Page 2 of 19 A time series of end of month soil moisture data was developed for each climate division in the United States from 1931 to present using a nonlinear water
balance (Huang, van den Dool and Georgarakos 1996). This data is available from the National Centers for Environmental Prediction (NCEP).
The components in this balance were precipitation, evaporation, runoff, and groundwater loss.
( )( ) ( ) ( ) ( )
dW tP t E t R t G t
dt
Where: W(t) is the soil water content at time t P(t) is the mean areal precipitation over area A And so on… Runoff, or net streamflow divergence, is composed of two components, surface runoff and baseflow.
max
( )( ) ( )
m
W tS t P t
W
( ) ( )1
B t W t
Where: Wmax is the soil’s water holding capacity in mm m is a parameter with a value >1 (typically in the range of 2-4) α is the inverse of the response time of baseflow µ is the portion of subsurface flow that becomes baseflow
Groundwater loss is also a function of these parameters, and evapotranspiration is estimated from the temperature, an estimate of radiation, and the Wmax
Huang et al. calibrated this water balance to match observed runoff values by applying search optimization algorithms to the parameters until the model’s estimates of hydrologic processes (runoff, baseflow, etc) showed the smallest deviation from real world, long term, and large scale data of these processes.
Page 3 of 19
Figure 1 - Map of Climate Divisions with Maryland highlighted
Page 4 of 19
This soil moisture data set was used to control for hydroclimatological variability when analyzing trends in streamflow.
Page 5 of 19
Figure 2 - Baseflow Timeseries and Seasonal Kendall Tau Plot for Linganore Creek at Frederick, MD
1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 19854
6
8
10
12
14
16
Calendar Year
Annual In
ches o
f B
aseflow
1935 1940 1945 1950 1955 1960 1965 1970 1975 19801935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Baseflow for Linganore Creek Frederick
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 6 of 19
Figure 3 - Timeseries and Seasonal Kendall Tau for end of month soil moisture for Climate Division 125
1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985200
300
400
500
600
700Time Series of Climate Division Soil Moisture for CD 125
Soil
Mois
ture
(m
m)
1935 1940 1945 1950 1955 1960 1965 1970 1975 19801935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for Climate Division 125
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 7 of 19 A comparison of the Kendall Tau plots for monthly baseflow and end of month soil moisture values suggests that the trends seen in baseflow for Linganore Creek
are explained almost entirely by climatological variation for Climate Division 125.
Figure 4 - "Difference Surface" comparing the difference in Z scores (computed from the probability of trend for each sub-period) between Linganore Creek's Monthly Baseflow and Climate Division 125's end of month soil moisture
1940 1950 1960 1970 19801935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
Beginning Year
Endin
g y
ear
Diff. Of SKT Z score(Monthly BF) - SKT Z score(Monthly SM) for
LinganoreFrederick and CD125
Positive Difference
Negative Difference
Z
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Page 8 of 19
Figure 5 – Shows the same “Difference Surface” as Figure 4, but with the same symbol and Z scores being represented by the color gradient
1940 1950 1960 1970 19801935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
Beginning year
Endin
g y
ear
Diff. Of SKT Z score(Monthly BF) - SKT Z score(Monthly SM) for
LinganoreFrederick and CD125
Z
-1
-0.5
0
0.5
1
1.5
Page 9 of 19 Additional Figures below for the Soil Moisture and associated trends of the other climate divisions used in this research:
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 120
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 120
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 10 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 121
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 121
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 11 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 122
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 122
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 12 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 123
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 123
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 13 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 124
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 124
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 14 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 125
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 125
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 15 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 126
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 126
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 16 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010300
400
500
600
700Monthly Soil Moisture for CD: 127
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 127
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 17 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 255
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 255
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 18 of 19
1930 1940 1950 1960 1970 1980 1990 2000 2010200
300
400
500
600
700Monthly Soil Moisture for CD: 307
CD Soil Moisture (mm)
Average for Month
1930 1940 1950 1960 1970 1980 1990 2000 20101930
1940
1950
1960
1970
1980
1990
2000
2010
Beginning Year
Endin
g Y
ear
Seasonal Kendall Tau on Monthly Soil Moisture for CD 307
Upward trend
Downward Trend
Strong Upward Trend (p<0.025)
Strong Downward Trend
Significance
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
Page 19 of 19
Huang, J., H. M. van den Dool & K. P. Georgarakos (1996) Analysis of Model-Calculated Soil Moisture over the United States (1931-1993) and Applications to Long-Range Temperature Forecasts. Journal of Climate, 9, 1350-1362.