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Comparison of Point Measurements within SFWMD and NARR-A values. Alicia Fogg April 26 th , 2005. 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
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Comparison of Point Measurements within SFWMD and NARR-A values Alicia Fogg April 26th, 2005
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
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
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 ???
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
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
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.
NARR-A Monthly Data Queried 56 points in Southern Florida for a one-year period November 2002 to October 2003.
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
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
Comparing Results of Point Method and Areal Estimation NARR-A Monthly data is ~ 15% lower than recorded ETp stations
Looking at the Area of Interest Monthly Latent Heat Values for Southern Florida are lower than ETp values recorded – as should be expected.
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
Thank You To.. • Dr. Maidment • SFWMD – M Mierhoffer, R Mireau, K Stewart • CRWR team members • Jon Goodall • Nate Johnson • Becky Teasley • Jessica Watts