1. Comparison of Point Measurements within SFWMD and NARR-A values
Alicia Fogg
April 26th, 2005

2. South Florida Water Management District
200 major water control structures
70 critical
130 manually operated
27 pump stations
6 under remote control
6 million people live in the SFWMD
Encompasses 17,000mi2
1800 mi of canals and levees

3. Simple Water Balance ( (
Purpose: develop simple water balance approach to quantify change in storage
Continuity Equation over Control Volume:
qRAIN ( (
qET
Area
Control Volume
QHout
QHin

4. Data Sources for Simple Water Balance
Horizontal Data
Structure Flow– Monitored at each Structure
Vertical Data
Rainfall – Point data at Structures and NEXRAD data over entire region
ETp – no Points in region
???

5. Weather Measurements within the SFWMD
SFWMD has database containing over 22,000 time series variables
16 potential evapotranspiration (ETp) and only one evapotranspiration rate site
69 Operations and Maintenance rainfall sites operating on a real-time basis

6. Potential Evapotranspiration Stations within SFWMD
Potential Evapotranspiration dependent on
Wind Speed
Water Availability
Net radiation
Vegetation Type
Highly monitored system with over 22,000 variables contained within parameter database
16 potential evapotranspiration measurement sites recorded daily

7. ETp – Historic and Recorded

8. SFWMD recommends using ETp daily values for vertical components.
ETp is a measure of the vegetation and the atmospheric conditions – not dependent on the amount of moisture!!!
Florida is WET, but not all of the ground is inundated all the time.

10. NARR-A Monthly Data
Queried 56 points in Southern Florida for a one-year period November 2002 to October 2003.

11. NARR-A Monthly Data

12. Calculating Monthly ET
The results obtained from NARR-A in
W/m mm/day
Interpolate the Point data to Raster
Use Zonal Statistics to determine Attribute Series for area of interest

13. Interpolated Evaporation Surface
For this time period [October 2003]
Lowest ET values over Everglades
Highest ET values over the Oceans.
Fairly Consistent ET value over Land ~ 3 – 3.5 mm/day

14. Comparing Results of Point Method and Areal Estimation
Historic Values
Closest Etp Station
IDW SFWMD stations
NARR IDW
January
79.67
98.20
98.25
64.22
February
88.48
93.92
94.39
62.89
March
121.83
109.19
110.01
96.08
April
132.60
135.14
135.60
100.46
May
143.53
150.09
150.42
111.61
June
126.00
121.81
121.85
117.53
July
128.34
140.59
139.59
132.08
August
124.62
118.31
119.00
121.93
September
104.10
110.28
110.94
106.27
October
98.58
109.46
108.29
98.14
November
80.10
90.59
90.27
74.66
December
73.16
73.02
73.04
62.17
NARR-A Monthly data is ~ 15% lower than recorded ETp stations

15. Looking at the Area of Interest
Monthly Latent Heat Values for Southern Florida are lower than ETp values recorded – as should be expected.

16. Conclusions
Latent Heat evaporation values and observed ETp values show same temporal trend
NARR-A results correlate well to observed data
NARR-A 3-hr time steps have potential to be useful for estimates of evaporation

17. Thank You To.. Dr. Maidment SFWMD – M Mierhoffer, R Mireau, K Stewart
CRWR team members
Jon Goodall
Nate Johnson
Becky Teasley
Jessica Watts

18. Questions?