In 1980 the city of Tampa was selected by the U.S. Environmental 
Protection Agency (EPA) as one of 28 locations for the Nationwide Urban 
Runoff Program (NURP). This was a three-year study during which four 
homogeneous land use gauging stations were implemented: low and high 
density residential, commercial, and highway watersheds which were less 
than one square mile. Rainfall quantity and quality, and runoff quantity 
and quality were collected at the sites. By selecting homogeneous land 
uses this study contrasted the previous USGS study. 
The location and source of the previously described urban runoff 
stations are shown graphically in Figure 3. Information is available 
from 13 stations surrounding Tampa Bay. However, little or no data is 
available on watersheds tributary to Sarasota Bay, which appears to be 
an area where data collection is needed in order to more fully 
characterize urban non-point source pollutant loadings. 
As a result of the USGS and NURP data, regression equations were 
developed for selected constituents which allow the estimation of non¬ 
point source pollutants to Tampa Bay. This information may be 
transferrable to the tributaries of Sarasota Bay; however, it would be 
advantageous to have data with which to verify the validity of equations 
and develop site specific information on the Sarasota Bay area. These 
regression equations and estimates of non-point source loadings were used 
in Waste Load Allocations (WLA) studies for both Tampa and Sarasota Bays. 
Major reports which have been produced in the Tampa Bay area containing 
urban runoff data or information have been utilized in preparation of 
this paper. These reports are listed in the Literature Cited. 
RAINFALL 
The Tampa Bay area experiences a sub-tropical pattern of rainfall 
which produces unique seasonal characteristics which affect the quantity 
and quality of urban runoff. It is important to describe the rainfall 
characteristics of the Tampa Bay area in order to have an appreciation of 
this seasonality and variability in rainfall. Data which are presented 
within this section were developed as part of the NURP studies by Metcalf 
& Eddy, 1983, utilizing hourly rainfall data from Tampa International 
Airport from 1948 through 1979. During that period the variation in 
total annual rainfall was approximately 29 to 74 inches. This is a 
variation from the most dry to most wet year of approximately 45 inches. 
Variations of mean monthly rainfall ranged from approximately 1.4 inches 
in May to 8.5 inches in July, with approximately 60% of the total annual 
rainfall occurring from June through September. This summer rainy season 
produces the most significant portion of the runoff volume to the bay 
systems. The rainfall data reveal that approximately 90% of all storms 
which occur in the Tampa Bay area have 1.0 inch or less volume. 
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