Mulching is covering the soil - there are many things you can use. My spud beds are mulched with black ploythene sheet, which I cut slits in and planted through. All my beds are mulched with rotted horse manure, except the roots bed, which isn't at the moment. When the plants are big enough, I'll shove something between the rows, possibly straw.
Mulching helps stop the soil from drying out, but also protects it from heavy rain, and blowing away in dry, windy conditions. It can also protect the plants. On the downside it can be a great harbour for slugs! But a good home for beetles, worms and other good beasties. It's much easier to pull weeds out (it's loosed than soil), and hopefully smothers annual weed seeds before they germinate. My manure mulch will be dug in at the end of the season, and more added in autumn/winter.
On the hosepipe front, there's no choice on my site, no running water! I've got 2 350 gallon (1000 litre) IBC containers linked together and connected to the guttering on my shed and greenhouse. When they're full, I have enough pressure to run a slow hose and a gravity fed watering system in the greenhouse. I also have a generator and a pond pump, so I can fill them from the river that runds alongside the plot. I'm going to get a third IBC for the bottom end of the plot, and rig up a corrugated iron roof for my row of 5 compost bins, and collect the water falling on those. Last year I had none of this in place, so had to carry all my water in cans and buckets from my house a couple of hundred yards away :shock:
I'm only watering newly planted seeds and transplants, the new fruit trees and canes, and in the GH, My soil holds water pretty well, and I didn't water very much last year, so I'll keep with that same thing this year. My swedes, leeks and caulis were quite small, though - but it was my first season, so may just have been me being not very good at it!