Comparison of Point Measurements within SFWMD and NARR-A values

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.

9
(No Transcript)
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/m2
  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
1301.01 1350.57 1351.65 1148.02
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?