Why do I need to harvest rainwater?

Hi,

I read elsewhere that it's very important in permaculture and just makes good sense to harvest rainwater which I agree with. However, water is fairly plentiful where I live and we have plenty of underground water for a well. My brother has convinced me that harvesting rainwater won't provide enough water, and we should just go with the well.

What do you all think? Thanks.

I think it depends on several factors.

It isn't just your annual rainfall, but how much you get during the growing season.
AND, how well your soil retains that water.

In many areas, there just isn't enough rainfall during the growing season to irrigate crops.
Wells are certainly nice, but can they provide the needed water every year?
Climate changes may alter rainfall in future years. Will there be enough?

A 1,600 square foot roof will collect 1,000 gallons of water for each inch of rain.
Many of us get most of our rain before the growing season begins. If we can collect/store it, we will have free water to use during the dry months when our crops are growing.

Where I am looking at property, I cannot afford to just watch the rain running down the highway in March/April.
If I cannot capture it, I will risk drying out my well in Aug/Sept.

It is a free resource that many of us cannot just let run away.

Rainwater is the primary source for water. You can stop the flow use it in your house and then return it to the land/plant for it to recharge other ppl well water. If everyone just take from the "fossil water" then you are creating potential water problems, it is also possible that you could pollute the well/underground water. It is just better to prevent potential problem rather than possible being a part of the problem.

And it is totally possible to minimize the amount of water that you use. There are alot of low flow water fixtures and it is also possible to reuse some of that water (grey water) you could also do without a water lawn/yard.

@Jeremy

Harvesting water isn't just about replacing your well or having a giant tank somewhere. Often it's more about where the water goes.

If you decide that installing a tank isn't for you, running your roof water into a few barrels can make a big difference with your irrigation, running water directly into your swales/pond/garden can be beneficial as well and if the system is designed with reuse and recycling of water in mind that same drop of roof runoff can work for you in several ways on the way through your property.

The question I would pose to you is why AREN'T you finding a use for the free water that falls from the sky in abundance. Even if the only take away was that you didn't put wear on your pump and kWh on your electric bill it's hard to beat.

I have a similar thought sometimes because we live in a very wet place - nearly 2 meters of annual rainfall, and we don't really have a dry season. We have mains water draw from the reservoir literally across the road, which is also fed from the river that forms one of our boundaries (which in turn comes from a spring not far away). In living memory the reservoir level has never dropped to a concerning level. However even here we did have to water for a 3 week period in the summer - a highly unusual 3 weeks with no rain, but nevertheless there I was every night watering the garden - thankfully the potatoes were heavily mulched and only needed to be watered one time.
At the moment I do not have plans to harvest rainwater from the house roof because there simply isn't a need, and in any case I would have no way to store it. I am installing guttering and water butts on the sheds and small greenhouse, partly to aid drainage in those areas and partly because then when I do have to water I have that resource ready to go, just where it is most needed.
If the worst happens and we can't rely on mains water any more we are fortunate enough to just have the river, but if that was not the case I might consider rainwater harvesting from the roof - however the sheer expense of creating storage (either massive tanks or digging huge ponds) means it's not in our plans unless things change drastically.

Last week it rained for the first time in about 2 months. My inadequate rain barrel system had been empty for some time. In about 1 hour one of my 55 gallon rain barrels was full. My other two filled up by the end of the rain. I don't have any catchment on the south side of my house. My house is 1100 square feet. It wasn't a heavy rain. I'm absolutely certain that with more catchment I could weather any drought this area has to offer with no municipal water.

Even if you can't catch enough rain to get you through a season, with enough catchment it will put a serious dent in your water needs.

As mentioned above, pumps require energy (from where?) and maintenance. They are an expense, as are rain barrels, gutters, etc.

Also, having a second large store of water besides your well adds redundancy and resiliency. What happens if the pump fails? Perhaps you have a manual pump. What happens if hydrofracking contaminates your water table?

At the present moment, for any design it may be a better use of resources to focus time and money on other things, such as energy efficiency in the home or getting trees established. Ecological triage, if you will.

Ponds make great rainwater catchment and can serve multiple functions (irrigation, fish, aquatic veggies, beauty, microclimate creation, habitat for beneficials, etc.).

I'd say it's wise to collect rainwater to keep the foundations and walls of your house dry.

Also, by definition, roofs are high and you already have stored kinetic energy which can be used to distribute the water where you want it using gravity.

Irene Kightley wrote:I'd say it's wise to collect rainwater to keep the foundations and walls of your house dry.

But this assumes that unless you set up a system to collect rainwater, it will all just pour onto your walls and foundations. Is this really true? I can't really remember ever seeing a house without gutters and downpipes, even when not collecting the water. The down pipes should either go into the storm sewer system, what in the UK is called a 'soak-away', I believe it is called a dry well in the US but not sure, or have a long enough last piece that they direct water well away from the foundations of the house.

Living in Portugal as I do now, I couldn't imagine not wanting to collect rainwater.

But I do remember living in Wales, and, to be honest, it's just not a very high priority there. Finding three dry days in a row to make hay was the biggest problem I remember. Rain is never far away. And all houses I knew were built in such a way that they could cope with wet feet.

Ha, yep, that sounds familiar, the hay has definitely suffered!

I can't really remember ever seeing a house without gutters and downpipes...

S Carreg,

I'm from Scotland, so I know what you mean !

In Wales the ever-present rain is a light drizzle to a heavy rain but here in France we have lightening storms with torrential rain and driving winds and on the walls facing the on-coming wind gutters are no use because they fill up faster than they can handle. (They often break and bend in new houses.) The water splashes on to the walls and ruins the foundations. That's why many old French houses have very overlapping outward pointing roofs and the roof edges are reinforced to support the weight of the water/snow. In August we had hailstones the size of golfballs which damaged cars, roofs and even smashed out water-heating solar panels and many gutters and downpipes were completely destroyed.

It all depends where you live and the local climate.

I think if water isn't a problem, then collecting it may not be a priority, just a case of common sense. In any case it's good to have a head of water than you can run downhill without relying on a pump. We use stored water not just for gardens but for cleaning chicken feeders, buckets and all sorts of things and it's very useful not to have to rely on local services.

Irene

Irene Kightley wrote:

I can't really remember ever seeing a house without gutters and downpipes...

S Carreg,

I'm from Scotland, so I know what you mean !

In Wales the ever-present rain is a light drizzle to a heavy rain but here in France we have lightening storms with torrential rain and driving winds and on the walls facing the on-coming wind gutters are no use because they fill up faster than they can handle. (They often break and bend in new houses.) The water splashes on to the walls and ruins the foundations. That's why many old French houses have very overlapping outward pointing roofs and the roof edges are reinforced to support the weight of the water/snow. In August we had hailstones the size of golfballs which damaged cars, roofs and even smashed out water-heating solar panels and many gutters and downpipes were completely destroyed.

It all depends where you live and the local climate.

I think if water isn't a problem, then collecting it may not be a priority, just a case of common sense. In any case it's good to have a head of water than you can run downhill without relying on a pump. We use stored water not just for gardens but for cleaning chicken feeders, buckets and all sorts of things and it's very useful not to have to rely on local services.

Irene

That sounds like some extreme weather! (We get our fair share of wind here too - 60 kph for days on end is common and 100 kph *might* be called 'stormy' by the locals) It does all depend on where you live, for sure... doesn't sound like the OP is dealing with quite the same issues that you are

I live in the south of Spain, but I am from Denmark - and frankly I don't understand why people in wet areas don't collect rain water...

In Denmark all houses have rain water drains, and most people collect rainwater for watering their garden, even if the rain hardly ever stops. I you already have drains, it is simply a matter of putting a few barrels at the end, not expensive at all. Having perpetual rain means you don't need a big expensive system - because you don't need to store water for long (in arid areas we need huge cisterns to make it through the dry season). But using the water in your house before letting it into the ground is def. cheaper than paying for mains water - plus you don't have to worry about pesticide pollution (big problem in Denmark) or chlorine in you water (not a problem in Denmark yet, but a problem anywhere that uses surface water). Collecting your rainwater also means that you buffer the amount of water ending in your garden or in the sewer system, thus the need for storm sewers etc will be smaller (ie. tax money saved). Even if you don't use it in the house, you can water your animals or your greenhouse with it.

Is water in the UK rally so cheap that it's not economically feasible to save it? And why is that? Water cleaning is expensive (in Denmark you don't actually pay so much for water as you do for having it cleaned after you've used it). The rainfall in Denmark has increased immensely the last couple of years and the need for storm drains have become much much greater - this is a huge expense for the municipalities - and everybody is encouraged to build buffers on their own property (economical incentive has been discussed - I don't know if it has been introduced) - this includes drains, water storage, dry wells, grass roofs, rain water gardens etc.

In our case, I think our annual water bill is something like £200? Maybe less? There is no way I could install sufficient equipment for anything like that cost. I have water butts, but I cannot simply put them on the downpipe of my guttering - they would be full after 1-2 rainy days, and then the overflow would be splashing everywhere, on the house, on the ground. I would need to splice them into the downpipe and then also open the ground drain to install and overflow from each waterbutt so that the excess would drain away neatly into the soak-away. A lot of work, and money, and honestly it doesn't get me very much. If I wanted to use harvested rainwater for drinking, rather than just gardening, then I need to think about filtration, better storage, and the costs rise very quickly.
Don't get me wrong - I love rainwater harvesting! I think in many, many cases it is a great idea and an essential component of any plan. And I know that my current situation is quite specific. But my point is that like with so many things in permaculture, it is not a one-size-fits-all approach. In many designs, rainwater harvesting will be a big priority project, but in some areas it is of very, very low priority. If we have abundant, reliable, constant, cheap water resources, and it would be costly and time-consuming to harvest rainwater, than it really makes sense to focus on other aspects of the project first.

If the cost seems reasonable consider a few other things.

Where does the tap water come from? A reservoir, deep well, water tower? And where before that? What is in the water because they do not remove it (dissolved pharmaceuticals, pollution collected from run off, minerals leeching out of the pipes/machinery)? What is in the water because they add it "for the good of the community" (chlorine, fluoride)?

The energy involved is important too. Often the tap water bill only covers a portion of the costs. The bill feels low because a certain amount of the local taxes prop up the enterprise.

What is the true cost of this? Does your bill really cover it? Does it matter what the costs to you are if it depletes a fossil aquifer? What about destruction of local ecology?

If every gallon you save, soak into the soil, or use without turning on the tap can do so much good, while avoiding doing so much harm is there a good enough reason not to? It doesn't take complicated or expensive equipment unless you want it to really. You can spend as much as you want on the most luxurious car, but usually you could have just walked there in the first place. The same analogy applies here. Most people try to find a balance that gets them there faster than walking, so somewhere between the bicycle and the Maserati there is something that could work for you.

Ok, I feel a little like a broken record, and I don't want to get into an argument because I'm not actually in disagreement with anyone over the benefits of harvesting rainwater. I am simply trying to point that in *some* cases it makes sense to make it a very low priority, and that insisting that it is of primary and urgent importance in every project is not always helpful.

For example:

I live in an area with nearly 2 m annual rainfall and no dry season. My tap water comes from the reservoir across the road from my house. Since this was created over 100 years ago there has never been a concerning dry period. This is fed by the river that borders my land, which in turn has its source from several mountain springs, all within 1.5 miles of my house. I know that the water is entirely unpolluted - I know this because I know the entirety of the water-course and there is no industry or arable land along it, because it is checked every day at the pumping station outside my door, and because we have had it analysed by an independent lab. The only thing added to it is chlorine, which evaporates quickly if you draw it and let it stand, so we do that for watering and drinking.
It doesn't cost us much to use mains water - and in any case it's a flat rate, not metered, so unless I want to actually disconnect from the mains (which by the way would put me in violation of building regs and make it impossible to sell in the future, not to mention endanger my business - microbrewery) I'd have to continue to pay for it any way.
All the infrastructure that is in place by the country is there to deal with the rainwater - otherwise the roads would flood, etc. My harvesting rainwater (even if every single person did it in my community) would have zero effect on that.

This is why I don't feel a pressing need to harvest rainwater.

The problem we have is getting the huge amounts of water away from the house. If I were to harvest it, I would have to either invest in truly enormous storage tanks, or do a lot of digging to hook water-butt over-flows into the dry wells (soak aways), in order not to have floods and damaged walls.

This is why it seems like a low priority.

Most people will have different sorts of situations and therefore it would make a lot of sense to establish rainwater harvesting as a fairly high priority. but all projects are not the same!

Of course it isn't first priority like it is in arid zones. I wouldn't make it so if I lived in Denmark certainly. But I would much rather be drinking rain water than chlorinated surface water (which mains water is in Spain, and I don't drink it), so I would make it a priority at some point - little by little.

I agree that there are benefits to collecting rainwater to reuse before returning it to the earth, and also that there are costs, in materials and personpower, involved with collecting said rainwater. And seeing as I have a high water table and plentiful rain, rain catchment is low on the list of priorities. I would like to set up rainwater barrels and gutters (and no, my house doesn't have gutters), but I have other things on the to-do list that take precedence.

I think the original poster maybe was reacting to a misconception about what permaculture is? Permaculture, by its nature, is amorphous...it works in different ways in different places. But because some of the originators of the concept are based in Australia, there was a strong focus from them on rain barrels, on swales, and other ways to capture the precious rains. In places like the UK, and here in Maine, we often have to deal with the consequences of too much rain, in the guises of slugs and snails, fungal diseases, and rot. So, our priorities may lie elsewhere. And the answer to the original question might be, "you don't need to do anything that doesn't fit your particular situation. and you can still be doing permaculture."

Still, I can see a benefit in lowering my electric bill by watering my garden from the barrel instead of the pump, during those short periods of rainless weather we have, and also the inevitable drier years. And I like the idea of using my dishwater twice. But some of those systems take a lot of time and money to set up, so I'll put them on the backburner for now...

I think that there might be some confusion about harvesting rainwater. I we all talking about roof cacthment for drinking water to be stored and filtered and purified.
Stored in tanks, barrel to be used to water a garden some months later. Just diverted from from storm drain to excessive pollution to where-ever the storm drain empties.
Some storm drains are combined with sewer and as such they tax the sewer system or is just overflowed/dumped untreated into streams, beaches and seas.

Harvesting the rainwater in the soil/pond on property could also prevent soil erosion, recharge the water table for "bob" down the slope, purifies the water so that our seas/river can host salmon/clam/oysters etc. One could also store the water in a pond that supplies fish, ducks, and aquatic plants.

I know this is an old topic, but I keep thinking about it the more I hear about the flooding in the UK.

Another thing to consider about rainwater catchment is that, especially if it's done in conjunction with a system that moves water through landmass, it can help to deal with flooding. Not on an individual scale, obviously, and I know that in the UK all water utilities are private, but one way to curb the issue of rain water having nowhere to go but the already flooding river banks would be to build catchment systems that divert it into landmass. Unfortunately, I have no idea how that could be implemented without government involvement, and it doesn't sound like the UK government cares enough to do anything about it, but that is another aspect of catchment that doesn't necessarily get discussed.

Perry Tart : You may be interested in this old post by member Jennifer Wadsworth, who is active on this topic, also she has a Facebook page I believe. Link Below :

https://permies.com/t/29821/desert/Water-Harvesting-Certification-Tucson-AZ


I hope this is useful and timely, For the good of the Crafts ! Big AL

Harvesting rainwater is all about having the water serve multiple purposes, with less human inputs.
The rain can sustain the lifeform in the soil, which gives us nutriets for the plants and maybe even a microherd for chickens.

We will also need to water the soil less the more that garden naturally captures the water vs just letting it sheet away.
Its not only about capturing the water its also about not letting it disappear by mulching it either with green mulch or woodchip mulch.

There is no need to harvest rainwater, but many thinks its a great idea.
Infact this link from Washington State encourages it.
Water-supply/Water-recovery-solutions/Rainwater-collection

Reasons to harvest rainwater:

1. In my case, my well water has a lot of dissolved salts. Not all plants can tolerate this. Rainwater makes them happy, which means I get fed.

2. In many urban areas, wastewater disposal fees are calculated based on your metered fresh water consumption. If you water your gardens and trees with municipal water, that water does not go to a sewage treatment plant. You are paying handsomely for a service you do not use.

Our situation seems to include part of each of the reasons people have called out.  We have a well but it's shared with 7 other homes, we'd rather not be the people that run it dry for our garden.  Where we live it rains about 60" per year, but zero rain from the end of June to the middle of September so for irrigation purposes rainwater is a great solution.  We also have a building with a metal roof that can collect about 1000 gallons from a 1" rainstorm so it was kind of a perfect fit for us.

Intelligent irrigation is going to become more and more important. Your groundwater/well water might not might come from or be recharged by rainwater that you get on site. Depending on your aquifer it could be from many miles away. The water could be thousands of years old. 100% of irrigation water is not watering your crops in a conventional bed. So you wouldn't be scavenging the entire water collected, some would continue into the ground.  Utilizing the rainwater gift and not depeleting groundwater from an aquifer that may not be getting rechatged at it's former rate with current drought issues might be an intelligent route.