Irrigation Demand for Water Distribution Design

[waterguy1]

I am a design engineer for a municipal water utility. We are currently expanding our service boundary to include about 600 acres of agricultural land. This land is anticipated to be developed with upscale residential communities. The upscale homes that I sampled use anywhere from 10,000 to 90,000 gal/month irrigation during peak months on 1/3 to 1/2 acre lots. I am wondering with this heavy irrigation use, could peak irrigation demand eclipse fire flow? I realize that this is different than fire flow in that the demand is spread out over the entire development, but the problem is that it will temporarily be a single feed for several years until a water tower and second supply line can be constructed in this area.

The question is.... does anyone know of any guidance for peaking factors for irrigation? I need to translate these gallons / month estimates to GPM peak flows.

 

[cvg]

I would assume that your peak hour would be anywhere from 3 - 6 times your average day depending on the length of the watering period each day. for residential and commercial, usually about a 12-hour watering period either during the day or night. for golf courses, 8-hours during the night and for golf course or developments with onsite storage (such as a lake), they can receive irrigation water at a steady rate 24-hours per day and pump out of the lake

 

[77JQX]

I work for a municipal water utility in the desert. For 1/2 acre residential lots, we'd estimate monthly summer usage at around 1.3 gpm per lot, with peak hour usage around twice that. So yeah, in our climate, a 600 acre development could see peak hour demands in excess of fire flow. But I don't think you should be using our consumption or peaking factors. Where are you located?

 

[BRIS]

Rule of thumb 1 l/sec per Ha net of green area (constant 24 hour flow), which corresponds to an evapotranspiration rate of about 8mm/day. Multiply by a peak factor for numbers of hours of operation per day, don't worry about what is growing.