The evaporation rate for water increases as follows:
- Hotter water temperature
- Colder air temperature (only a factor if there is some humidity)
- Lower humidity percentage (for same temperature; variation better described by dew point temperature)
- Higher wind (a HUGE factor)
Based on
this page for August weather in Augusta, GA, it does look like August 1-3 was lower than normal in temperature (in
this page it looks like July was pretty normal). Using data from
this week and daily detail, I can calculate the evaporation rate of the water, though the wind should be the wind at the surface of the water which with typical barriers (fences, etc.) will be lower than I show below. "Night" is early AM of the day indicated (i.e. the coldest usually around 4 AM). I assume a water temperature of 86ºF.
Date ........... Temp ...... DewPt ...... Humidity ...... Wind ...... Evap (in/day)
Jul 27 Night .. 77ºF ....... 69ºF ......... 72% .......... 0 MPH ..... 0.18"/day
Jul 27 Day .... 95ºF ....... 72ºF ......... 47% .......... 9 MPH ..... 0.72"/day
Jul 28 Night .. 82ºF ....... 73ºF ......... 74% .......... 0 MPH ..... 0.13"/day
Jul 28 Day .... 96ºF ....... 66ºF ......... 37% .......... 14 MPH ... 1.37"/day
Jul 29 Night .. 71ºF ....... 60ºF ......... 68% .......... 6 MPH ..... 0.82"/day
Jul 29 Day .... 88ºF ....... 57ºF ......... 35% .......... 7 MPH ..... 0.99"/day
Jul 30 Night .. 70ºF ....... 57ºF ......... 63% .......... 7 MPH ..... 0.99"/day
Jul 30 Day .... 91ºF ....... 58ºF ......... 33% .......... 6 MPH ..... 0.86"/day
Jul 31 Night .. 73ºF ....... 68ºF ......... 83% .......... 6 MPH ..... 0.65"/day
Jul 31 Day .... 84ºF ....... 70ºF ......... 63% .......... 9 MPH ..... 0.79"/day (rain/thunderstorm and cooler later in the afternoon)
Aug 1 Night .. 69ºF ....... 66ºF ......... 90% .......... 11 MPH .... 1.10"/day
Aug 1 Day .... 89ºF ....... 69ºF ......... 69% .......... 10 MPH .... 0.50"/day
Aug 2 Night .. 69ºF ....... 67ºF ......... 93% .......... 8 MPH ..... 0.82"/day
Aug 2 Day .... 77ºF ....... 70ºF ......... 76% .......... 7 MPH ..... 0.68"/day
Looking at the overall history in July to early August, it looks like
the average wind (day and night combined) went up from 4 MPH to 7 MPH with higher gusts as well (and not having calm nights)
and the dewpoint dropped from 69ºF to 66ºF and these two factors largely account for the increase in evaporation rates. This would go from 0.46"/day to 0.77"/day. If the wind is cut back from fences by 43% to 2.3 MPH to 4 MPH then this is 0.33"/day to 0.52"/day which might be what you have been seeing.