I have been studying for a while for my project and generally get the ideas of flow rates, head/psi, friction losses and such. Still I would like to get some feedback before I go do my project wrongly.

I have a dirt race track that is about 6400 square feet of soft dirt (see www.outbackrc.com for pictures, etc). I water it to keep down the dust and sometimes to help with traction. I use a 225-foot (150-foot from house to track, 75-foot within the track) run of 3/4" garden hose from my house, which is on a private well. There is a very gentle slope down from the house to the race track. Let's say the pressure and flow is not as desired. It takes 15 minutes to moderately water the track. I estimate about 50 gallons is being used in this 15 minutes. To an extent, I am using more water than necessary to keep the first spots wet by the time I get to the final spot on the track -- i.e., if I could mist the track in 2 minutes, I could use less water to get through the ensuing 5-7 minute race.

There are many possible solution. Through a combination of considerations, I propose a system whereby a number co-located of 55-gallon barrels are slow-filled with water from the house. Manual filling is acceptable, but some kind of sensing switch that auto-fills (tops-off) the barrel(s) would be nice. So, QUESTION 1: What product would accomplish this topping off action, ideally not using electricity.

Now that the barrels are full, the water must be strayed out onto the track. I am guessing a final outflow of 15 gpm at 50 psi might work(the farther I can spray, the less hose length I need, as the person can just stand back and angle up)). I am rejecting the use of sprinklers because the fierce winds can cause planned patterns to be blown to somewhere else. I think I need a person/people adjusting the placement of the water by 'eye'. So I might have 1, 2, maybe 3 hose lines of say 75-feet each coming from the barrels. These could also be 3/4-inch garden hose, for example, although lighter hose is easier to handle. I could see also using only 50-foot hose of a larger diameter if it could throw water around to achieve the desired effect. A stationary water gun that could spray the entire track from a fixed position would be great, but I guess not likely. So, by looking around at what is out on the market, by seeing that an electric pump might require 11 amps of 120v though my 175-feet of 12ga extension cord (which is already in use by other users), I thought maybe a used ~5hp gas-powered pump with 2-inch inlet/discharge might be plenty good enough. QUESTION 2: is that a fair design -- ~5hp gas-powered driving 2-3 3/4-inch garden hoses through some 2-inch to multiple-garden-hose adapter.

Overall, is there a better system design? long-term low cost is good. Reducing the time to water the track is extremely desirable (going from 15 minutes to 3 minutes, for example). The track is shaped like a 1/4 of a circle with a 90-foot radius with likely water source near the circle's center, at the edge of the track.

[PS: if I put any unecessary stipulations in the design, feel free to break down the problem a little differently, such as if using an electric pump is really, really better, then go with that, etc.]