We have a 1000 gallon inground tank and a 500 gallon above ground tank. We collect rain water from the downspouts into the 1000 gallon tank, then pump it up the hill to the 500 gallon tank. We then gravity feed it down to the vegetable garden where it's distributed by soaker hoses. It works well for us, but it isn't enough to last through the whole dry spell we usually have in August and September. However, we have a very large garden. For flower beds or a smaller garden, I think it would be sufficient.

Our water is metered and we get one bill Oct to April and another April to Oct. So the winter bill is without garden usage of course and it is something less than 25,000 imperial gallons in 6 months. Our summertime bill is 126,000. So we use more than 100,000 gallons of water on the garden. The area we live in is in a rain shadow so during that April to October period we get virtually no rain so anything green is sprinkled. btw, my lawn was not well watered so it was alive, but barely, and I could have used much more water on the veggie garden. I have about 1/2 acre of land around the house landscaped.

...and 100,000 imperial gallons is about 120,000 U.S. gallons. A collection system to defray much of that water total would be massive.

This 120K gallons equals about 0.37 acre-feet, so if 1/2 acre was evenly watered this would equal about 9 inches of rainfall. Of course the watering was uneven, but the 9" rainfall equivalent at least brings the 120,000 gallons down to earth!

larry gene, that's another interesting number. Spread over June to September, that's 16 weeks, so about 3/4 of an inch per week which is why my lawn wasn't green. Sometimes, I think we don't live in a rainforest, we live in a desert!

120,000 gallons equals about 2,181 fifty five gallon oil drums, just to put it into perspective. Thatsa a lot of water and one heck of a lot of storage to make it work during the summer when we need it and it doesn't rain much.

I have a few rain barrels and siphon off the water to high ridges with big trees where the ground is still dry a few inches down. I try to absorb as much water as possible throughout the season, with the excess going into a series of ponds that evens out the excesses of moisture we get at times here during the winter.
I think of my trees, shrubs, mulch, and groundcovers as a thick quilt that gets as wet as it can, but drips dry.

A puddle in a landscape is as bad as a stub on a tree. Water control, and maximum usage, is of the utmost importance.

I think we live in a desert too.

King County has a permit process for rainwater collection and storage. You may want to check with them or just play ignorant. In Island County we can build up to a 5,000 gallon storage system without a permit. Maybe KC has something similar. I can't see continuing to have a good garden on Whidbey without using harvested rainwater. We're planning on one 5000 tank and four 1000 gallon tanks. Looks like we'll start with two 1000 gal tanks filled by the pig house roof. I think you can find a lot of good information on the State's Dpt of Ecology site. Tom

We got 9 inches of rain. Yesterday. It was unreal, it just poured hard the entire day.

That's an amazing amount firefighter! We got 3 1/2 inches in the last "rain event". Interestingly, I dug down in a bed covered in arborist wood chips, under a huge fir and it was still dry 10 inches down.

I lived fifteen years in the Arizona desert. Trust me, this ain't it! ;)

I have a medium-size lot, and I am going to begin saving gray water in a barrel for summer & fall watering. How can I use a rain barrel here in the PNW where it is dry in the summer and rains in the winter, & I don't have room for ponds, etc.? I read an article in our local newspaper about a local woman's garden, showing her rain barrels, but it didn't say how she used the water when she needed it---during the summer. (She also had a smallish city lot.) Any suggestions for me?

I am collecting water in two rain barrels that are standing under downspouts.
I am also collecting big plastic jars from juices and so on. When my barrel is full and i have time, i fill my collection of jars with water. In spring i use these jars to surround some plantings. It works like Wall of Water for my tomatoes, which i surround with jars and cover with row cover together with jars. Water will heat during day and release heat during night. I also put jars with water in my unheated GH for heat collection and watering.
In summer when rains are rare, i use some of my jars to collect kitchen water to carry to the garden.

But recently i was pointed that because my roof is covered with asphalt shingles, i should not use collected water in my veggie beds. Now i am trying to collect rain water for GH and houseplant watering from GH plastic roof.

Possible it's time to look for carbon downspout filters to try to catch toxins that can come from asphalt.

Any ideas about this?