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precipitation/evaporation rate

Mon, 04/12/2010 - 3:39am — Michaela
Hello together, I have a very simple but for me essential question. In Germany the Weather Service states precipitation and evaporation rates for example in 1 mm/day (= 1 litre/(sqm day)). The unit m/sec is very uncommon for me. That is why I want to assure myself. Is the following conversion right? 4,2 mm/day = 4,86E-08 m/sec In the CEQUAL manual values are given (branch precipitation file) like 0,001 m/sec or 0,002 m/sec, that would mean 86400 mm/day or 172800 mm/day, respectively. That's not possible. In Germany the cumulative amount of precipitation is 700-900 mm/yr. That is why I challange my conversion. Can anybody help my? With best regards from Germany Michaela
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Water Quality
Wed, 04/14/2010 - 1:11pm — chris

Hi Michaela, Yes, the units for precipitation rate is m/sec. I agree that the example in the CE-QUAL-W2 maual doesn't make sense. We will change that in the next edition. cheers, chris
Thu, 04/15/2010 - 2:13am — Michaela

Hi Chris, I'm still at a loss with the evaporation rate. The unit is the same like for precipitation. For example, the model calculates a evaporation rate of 0.785E-01 m/s for my branch. That would mean that 6782,4 m/d evaporate. So my waterbody would be exhausted within a day or better in less than one hours (deep = 33 m). Nevertheless, the water table is continuous. The inflows would rise the water table about 2,3E-09 m/s (Inflow = 450 m³/d, A = 2300000 m²). So there is no explanation for the continuous water table. Sorry, but I don't understand the calculated evaporation rate. Please help me! Thanks a lot. Michaela
Wed, 04/21/2010 - 12:41pm — chris

Hi Michaela, The units for evaporation rate in the snapshot output should be m^3/s rather than m/s Chris