page 1 19 appendix 2: hydrometeorology and hydroclimatology … · 2019. 10. 21. · 1935 1940 1945...

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Appendix 2: Hydrometeorology and Hydroclimatology of Baseflow

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.

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Figure 1 - Map of Climate Divisions with Maryland highlighted

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This soil moisture data set was used to control for hydroclimatological variability when analyzing trends in streamflow.

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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

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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

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

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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

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

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1930 1940 1950 1960 1970 1980 1990 2000 2010200

300

400

500

600



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


Upward trend

Downward Trend



Significance

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

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1930 1940 1950 1960 1970 1980 1990 2000 2010300

400

500

600



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


Upward trend

Downward Trend



Significance

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

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1930 1940 1950 1960 1970 1980 1990 2000 2010200

300

400

500

600



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


Upward trend

Downward Trend



Significance

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

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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.

page 1 19 appendix 2: hydrometeorology and hydroclimatology … · 2019. 10. 21. · 1935 1940 1945...

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