Question
My mother has a garden/yard irrigation system that my father set up years ago. Source water is from a small stream/beaver dam. The system includes a 1.5 HP centrifugal pump wired for 115 volt power. Distance from the pump to the electrical box is about 25 feet. The orignal pump was a Wayne Pump, which I replaced with a Myers pump(QP15)when the Wayne pump quit two years ago. There is about 15 feet of 2-inch suction line w/ a 2-inch foot valve on the intake end. The pump in mounted on a small platform at the edge of the stream and is about 4 feet above the stream surface; the stream is about 3 feet deep at the foot valve. The discharge side of the pump is into a 1.5-inch PVC line that goes uphill into the garden. The 1.5-inch PVC line length is about 35 feet from pump to garden. Total static head from foot valve to garden is about 10-12 feet. At the end of the 1.5-inch discharge line in the garden there is a brass manifold (Orbit SunMate Pro)that spreads the flow into four 3/4-inch hose nozzles that connect to four 5/8 inch garden hoses. The garden hoses are used to irrigate the garden and yard and are usually attached to four pulsating sprinkler heads on 24 or 36-inch risers. The hose lengths vary from 20 feet to 300 feet depending on where in the yard or garden the irrigation water is needed. The garden/yard have a slow rise to them as you go further and further from the discharge manifold; at the extremities of the yard the static head could be 25-30 feet from the foot valve in the stream. In winter the pump must be drained. Sometimes in spring high water the pump has to be removed quickly to keep it from being submerged. I would like to optimize this system to get better water pressure at the extremities of the system, and to maximize gpm for irrigation. I am not sure where to start. Larger pump? Larger manifold? Lower pump closer to water surface? Add a booster pump? Also,I am wondering if Banjo-type couplings can be used on suction and discharge lines at the pump for quick removal? Are these type couplings sufficiently air tight? Thank you for considering my questions.

Answer
Great information, thank you.
From the stream to the Orbit hose connection, everything is fine. The hose connection is the first problem. It is made to operate from a house water supply at much lower flows. It probably burns-up 10-15 PSI with the configuration you have. Next problem is a long length of hose. 5/8" garden hose probably uses 5 PSI per 50' of run and that doesn't count kinks, turns etc.  
I suggest replacing the manifold with a system of ball valves and hose connections. Next would be look into 3/4" or 1" hose for your long runs. Even going part way with a 1" hose then to the 5/8" would help.
The banjo (Cam-lock) type fitting are fine for the suction and discharge. Just make sure the sealing surfaces and the gasket are clean when you put them together.

Matt