Guest Blogger: MJ Carnevale, City of Winter Haven Natural Resource Division and Devon Moore, City of Winter Haven environmental scientist.
It looks like our May rain dance was successful! June was a very wet month this year with the Winter Haven area receiving a whopping 10.12 inches of rainfall. This was also the 1st month in 2017 that the amount of gross rainfall significantly surpassed the recorded total evapotranspiration (ET), netting 5.83 inches.
Please find below the hydrologic update through the month of June:
Evapotranspiration, which is the loss of liquid water from the earth due to evaporation and plant use (transpiration), can cause water loss if its value is greater than that of rainfall. While the drought conditions we’ve experienced earlier this year have begun to reverse, we are still sitting at a -7.24 inches net rainfall for the year; so we still have a ways to go until we are back to normal. Figure 1 shows the 2017 monthly rainfall and ET values recorded to date. Now, let’s see how June’s precipitation compares with historic records. Figure 2 displays that the June rainfall (10.12 in.) fell well above the long-term average (7.92 in.) and just below the historic normal range (10.77 in.). Now that we are officially into the wet season, let’s hope that this trend continues in order to reverse our rainfall deficit.
So how has this significant increase in precipitation affected our lakes? Figure 3 shows the average monthly lake surface levels and how they compare to historic records. The month of June saw the first increase in lake levels so far this year. The lakes started the year off above the long-term average, however the below-average rainfall from January to May cause these levels to drop rapidly. While we did get an increase in surface levels, the lakes are currently still just below average. Again, we still need quite a bit more rain this summer to turn this drought around.
Like last month’s report, I just wanted to include current KBDI information to reinforce the impacts caused by low rainfall. KBDI or the Keetch-Byram Drought Index is used to measure the potential for fire by studying soil moisture estimates. The index is displayed in a scale of 0 – 750 with the higher values equating to drier conditions. The final KBDI score in Polk County for the month of May was 590 which indicates relatively dry conditions and a fairly high potential for wildfires. Polk County scored a 51 at the end of June! This shows that the considerable rainfall in June almost completely reversed the dry conditions we experienced in the first 5 months this year.