Fig. 4. Fluctuations in recorded waste depth during a 3-d period at a plastic-lined swine waste lagoon. Because seepage was zero, the change in depth should equal evaporation. Shown are (a) change in depth as detected by the waste level recorder (30-min averages) and the evaporation rate predicted by Eq. [3], (b) deviations between the recorded waste depth and modeled evaporation, and (c) wind speed and wind direction.