Does anyone know a reasonable demand factor (gpm/acre, gpm/edu??) for estimating irrigation demand for commercial, industrial, residential, parks, etc. I have found reasonable number for water consumption by using metering data but can't relate to irrigation demands. I suppose a peaking factor is what I am looking for. Any idea or theory?
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Estimating irrigation demand
- Thread starter sualac
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Ask at the nearest agricultural university. Maybe someone there could help you.
I believe this will be depending on soiltype, plant and biotopic type, local climate (day/night temperature and humidity) and not at least how you distribute (drip type ground or spreader) and when (night/day), and of course max demand during dry periodes-
From your or your customers side it will also be an economic question: cost, operation and maintenance of equipment, capacity and cost of water.
Another possible approach: If your plants /biotope thrieves at, lets say 150 or 300 mm per square meter per month (just a figure) and you have cheap water available, you could also try to discuss if this distributed, say divided on each third night (just a figure again), is agricultural OK, and then check what this means equipmentwise.
You will also have to evaluate what selective areas have to be watered how much : native woods and plants would probably require nothing or perhaps only limited waterin during dry periodes, flowers or non-native plants more.
I believe this will be depending on soiltype, plant and biotopic type, local climate (day/night temperature and humidity) and not at least how you distribute (drip type ground or spreader) and when (night/day), and of course max demand during dry periodes-
From your or your customers side it will also be an economic question: cost, operation and maintenance of equipment, capacity and cost of water.
Another possible approach: If your plants /biotope thrieves at, lets say 150 or 300 mm per square meter per month (just a figure) and you have cheap water available, you could also try to discuss if this distributed, say divided on each third night (just a figure again), is agricultural OK, and then check what this means equipmentwise.
You will also have to evaluate what selective areas have to be watered how much : native woods and plants would probably require nothing or perhaps only limited waterin during dry periodes, flowers or non-native plants more.
- Thread starter
- #3
I understand your point but I am only doing general estimation of how much water will be used essential to pipe design. I do not know what will be planted but only the acreage of the parcel. I could assume a 1.7 gpm/acre for example but I do not have any backup sources for my decision. I hope am making sense.
I think it will depend on what type of fixture/sprinkler you use. There are a wide variety with differing areas of coverage. On the irrigation job I did for the most part I designed the whole system with a sprinkler I knew would do the job and then did a performance spec/drawing showing my caculated information. Just like a regular potable water calculation. The sprinkler manufacturer will have charts showing the radius of coverage at some given pressure. Get a hydrant test and model as such. I used EPANet.
OK. But you still have to go through the detailed planning way.
Looking into below link, you will get an idea of what area you can serve out of a 'normal' private garden system, through a normal hose(1/2").
If you assume this will be covered by 1-2 yards per second through the hose, you can establish a rough amount/area calculation.
You will still have to evaluate some of the details mentioned in my first posting,
Looking into below link, you will get an idea of what area you can serve out of a 'normal' private garden system, through a normal hose(1/2").
If you assume this will be covered by 1-2 yards per second through the hose, you can establish a rough amount/area calculation.
You will still have to evaluate some of the details mentioned in my first posting,
their design manual was recommended to me to check an upcoming project. Cursory review looks like it has good basic information.
My rule of thumb is one litre per second per hectare
In simple terms the typical crop water demand is approximately equal to the evaporation rate. (Ec =1)
Irrigation demand is (evaporation + losses) times percentage ground cover
Growing grass with an evaporation rate of 6mm/day at 80% efficiency (which is high) gives 0.9 l/sec/ha.
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