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| how much do we lose to evaporation? http://byap.backyardmagazines.com/forum/viewtopic.php?f=1&t=3330 |
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| Author: | timmy [ Apr 25th, '08, 09:06 ] |
| Post subject: | how much do we lose to evaporation? |
AP is great at conserving water, but the previous thread about building AP's in 3rd world countries got me thinking if there is anyway to make it even more water efficent. I imagine our common method of flodding a gravel bed has an evaporation penalty to it since the greater surface area also means more evaporation. but the question is, how much and can we improve on it? note: i'm only thinking on large scales such as 10,000L + since in a small system the water loss is going to be tiny no matter what |
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| Author: | TCLynx [ Apr 25th, '08, 09:13 ] |
| Post subject: | Re: how much do we lose to evaporation? |
I expect there are ways to improve on it but when things are hot and dry, the plants are going to transpire much of the water anyway. Most of the things that might be most tempting to try are going to reduce aeration and most methods of aeration also mean more evaporation too. |
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| Author: | RupertofOZ [ Apr 25th, '08, 11:49 ] |
| Post subject: | Re: how much do we lose to evaporation? |
Think most people have figured around 10% per week?? at the height of summer Timmy.... But it varies, depending on amount of plant cover in the growbeds, number of growbeds.... whether or not under shadecloth, greenhousetanks/sumps covered etc..... |
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| Author: | Angie [ Apr 25th, '08, 12:09 ] |
| Post subject: | Re: how much do we lose to evaporation? |
The only thing I can think of to recover this lost evaporation without putting the plants in too humid a condition to live is what was suggested in a vertical farm and that is basically refridgerated cooling lines with water traps underneath. Think of an ice cold soda can sweating on a hot summer day. |
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| Author: | Chappo [ Apr 25th, '08, 14:29 ] |
| Post subject: | Re: how much do we lose to evaporation? |
I'm guessing a mesh / shade cover would help catch some of the "steam" and send to back to the bed. |
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| Author: | timmy [ Apr 25th, '08, 16:39 ] |
| Post subject: | Re: how much do we lose to evaporation? |
I think a meaningful way would be to reduce the temperature on the gravel of the growbed. this will also help protct your plants from wilting in high heat. maybe just lay shade cloth over the top of the bed and see if it effects your water levels after 2 weeks? |
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| Author: | Chappo [ Apr 25th, '08, 16:46 ] |
| Post subject: | Re: how much do we lose to evaporation? |
timmy ,, that's what I meant ,, not only would it shade the gravel thus reducing heat ,, and "steam" would tend to collect on the shade-cloth and drip back down. Intertesting theory ,, anyone tried this? |
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| Author: | RupertofOZ [ Apr 25th, '08, 16:54 ] |
| Post subject: | Re: how much do we lose to evaporation? |
IMHO.... other than the times when the growbeds may be empty or partially planted... the water loss isn't actually mainly from evaporation..... In a fully planted, thriving system.... most of it's from the plants "transpiration"..... covering the growbed in this situation probably wont help.... Guess you could cover all the growbeds/tank(s) and maybe try and collect the humidty condensation..... But can you afford a greenhouse 
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| Author: | earthbound [ Apr 25th, '08, 20:02 ] |
| Post subject: | Re: how much do we lose to evaporation? |
Covering the fish tank with floating rafts should cut down some evaporation. Heres interesting evaporation info for Australia (sorry rest of the world  ) http://www.bom.gov.au/climate/averages/ ... tion.shtml
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| Author: | synaptoman [ Apr 25th, '08, 23:58 ] |
| Post subject: | Re: how much do we lose to evaporation? |
I'm losing about 10% a week. |
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| Author: | Chappo [ Apr 26th, '08, 00:32 ] |
| Post subject: | Re: how much do we lose to evaporation? |
10% seems excessive ,, I'll look back at your system before saying anything........ |
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| Author: | RupertofOZ [ Apr 26th, '08, 00:35 ] |
| Post subject: | Re: how much do we lose to evaporation? |
10% is consistent Chappo.... there's an old thread here where the same question was asked.... And people consistently reported the same figure ... or close to it..... winter may be less, less plants may actually be less Like I said.... IMHO.... most of it's due to transpiration not evaporation... |
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| Author: | DanDMan [ Apr 26th, '08, 01:35 ] |
| Post subject: | Re: how much do we lose to evaporation? |
A lot of how much water you loose depends on weather and how much you plants transpire to stay cool and regulate. 6 large banana pepper plants could suck up 30 gallons of water from a nearly sealed DWC system on a very hot day. |
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| Author: | Chappo [ Apr 26th, '08, 02:51 ] |
| Post subject: | Re: how much do we lose to evaporation? |
I'm learning again , and thanks to this forum. My loses on pond aquaculture only work out at 3% , give or take a bit. I suspect , but am probably 100% wrong , that plant transpiration only accounts for a lesser percentage. That gravel I guess , has a huge surface area even at thye top few inches and would give up a lot of water. Probably wrong , but worth thinking about. |
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| Author: | Food&Fish [ Apr 26th, '08, 05:47 ] |
| Post subject: | Re: how much do we lose to evaporation? |
I try to keep my water at least 1 1/2 in below the surface of the beds and depending on the plant load and weather conditions the amount of top up water is different |
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