A couple of observations...
Blue Stripe poly is measured as an outside diameter, you were wise to use 32mm because the most commonly used 25mm Blue Stripe variant is closer to 21mm internal diameter. The 32mm is actually closer to 25mm than the 25mm is!
The cheaper Green Stripe Poly is measured as an internal diameter but the fittings are dearer. Life is sometimes unfair.
The 25mm LDPE has an internal diameter of 25.4mm. It isn't pressure rated but the Holman 25mm LDPE did have a rating of 400 kPa.
LEAVES: You can cut an oversized round piece of shade cloth and sit it in the tank's top meshed inlet. To clean the shade cloth, you simply remove and shake.
There are also commercial mesh covers with handles available, they are a good product.
https://rainharvesting.com.au/products/ ... ance-tray/
I do not recommend the hard covers...water needs to breathe.
Your tanks however are high and while I have never tried it, I suppose a round piece of moderately domed shade cloth or mesh attached to a 'ring' that fitted down the top inlet's outside wall could be fitted over the top meshed inlet. Another 3D project perhaps?
TANK BASE: I really regret not mentioning 'chasing' the tanks in the soil on a compacted sand base before you did the trenching. I also add some cement to the sand first.
COST: $8,000 all up is a bargain for everything you have. Once the trees are planted, you will have a backyard Garden Of Eden.
BOM radar: I look at this every day. One thing that I have learned is that it is often best to water the lawns and garden immediately after light rain. A fall of <3-4mm does little more than wet the top layer of soil but if it is after a dry spell, the additional manual watering will work wonders.
SPRINKLERS: I heard a while ago that sprinklers that water a square pattern are now available but I have never seen them advertised. Have you heard of them?