Happy holidays to my readers, followers, and fellow bloggers. Hope you have safe travels, good company, and a prosperous new year. I'll be back in 2010.
Chris
Monday, December 21, 2009
Holiday Greeting
Happy holidays to my readers, followers, and fellow bloggers. Hope you have safe travels, good company, and a prosperous new year. I'll be back in 2010.
Chris
Saturday, December 12, 2009
The Technical Feasibilty of Rainwater Harvesting for Domestic Water Supply
Getting back (finally) to my most recent topic I have some numbers to throw out, in order to assess whether relying on rainwater for a domestic water supply is technically feasibly in a semi-arid or arid climate. Tucson would be considered semi-arid because our average rainfall is roughly 12 inches per year (although this year we have only had about 6-7 inches, which makes us arid at this time), but we are classified as arid because of our high evapotranspiration rate.
There are many skeptics who say that rainwater cannot be relied on as a water source in places like this because rain is too unreliable. Our annual rainfall typically comes in two seasons - winter and summer. Our winter rains tend to be gentle, slow rains that might occur several times a month, amounting to about 5 inches on average during the period December to April. Our summer rains, on the other hand, are known as monsoon rains because they result from a seasonal wind shift in summer, and often come in torrents. We typically receive between 5 and 7 inches of rain in the summer and it's not uncommon for the bulk of that rain to arrive in 3 or 4 rainfall events during the months of July and August. In between those seasons we might typically go for 2 or 3 months with little or no rain.
With that type of rainfall pattern, obviously, the key elements of rainwater harvesting will be capture area and storage. If you have a sufficiently large surface area from which to capture water and sufficiently large storage to hold onto that water during long dry periods rainwater becomes a feasible water supply.
Here are a few basic calculations of available water:
10" of rain falling on 2000 sq. ft. of roof surface will yield roughly 12,500 gallons of water.
10" of rain falling on 3000 sq. ft. of roof surface will yield about 18,700 gallons of water.
12" of rain falling on 2000 sq. ft. of surface yields about 15,000 gallons, and
12" of rain falling on 3000 sq. ft. of surface yields about 22,400 gallons of water.
If you take those numbers and average them out over the course of the year you come up with a range between 34 and 61 gallons per day. Obviously you are not going to maintain a home, yard, and pool by collecting rainwater unless you have a very large surface from which to collect the water. But it's perfectly reasonable for two people to survive on 61 gallons of water per day for indoor uses such as cooking, cleaning, bathing, and drinking.
But how do you make rainwater suitable for drinking? That is the tricky part, some of which I will try to address in a post on the regulatory limitations on use of rainwater for water supply. But in a general sense, you must install a home water treatment system to make this water suitable for consumption. This ranges from selecting proper roofing material that won't leach chemicals into the water falling on it, to engineering the collection system so the first flush of water coming off the roof is bypassed (to limit the bird poop in your water supply), to a system of filters and treatment technologies that will ensure no harmful bacteria or other nasties in your water. This is the primary annual cost of this type of water supply - the energy and maintenance of the treatment system. Most of the other costs are upfront when the collection and storage are installed.
This site includes some helpful information on what is necessary for making rainwater suitable for potable uses.
Is this type of system suitable for the average homeowner? Clearly not. But there are people out there who are willing to invest the money, time, and effort to get off the grid, or off the pipes in this case, and whose lifestyle allows them to live on only the amount of water necessary for basic, indoor human needs, without all the extraneous uses of high-quality drinking water many of us find necessary for our quality of life.
More when I find the time, including the aforementioned regulatory analysis of rainwater harvesting.
There are many skeptics who say that rainwater cannot be relied on as a water source in places like this because rain is too unreliable. Our annual rainfall typically comes in two seasons - winter and summer. Our winter rains tend to be gentle, slow rains that might occur several times a month, amounting to about 5 inches on average during the period December to April. Our summer rains, on the other hand, are known as monsoon rains because they result from a seasonal wind shift in summer, and often come in torrents. We typically receive between 5 and 7 inches of rain in the summer and it's not uncommon for the bulk of that rain to arrive in 3 or 4 rainfall events during the months of July and August. In between those seasons we might typically go for 2 or 3 months with little or no rain.
With that type of rainfall pattern, obviously, the key elements of rainwater harvesting will be capture area and storage. If you have a sufficiently large surface area from which to capture water and sufficiently large storage to hold onto that water during long dry periods rainwater becomes a feasible water supply.
Here are a few basic calculations of available water:
10" of rain falling on 2000 sq. ft. of roof surface will yield roughly 12,500 gallons of water.
10" of rain falling on 3000 sq. ft. of roof surface will yield about 18,700 gallons of water.
12" of rain falling on 2000 sq. ft. of surface yields about 15,000 gallons, and
12" of rain falling on 3000 sq. ft. of surface yields about 22,400 gallons of water.
If you take those numbers and average them out over the course of the year you come up with a range between 34 and 61 gallons per day. Obviously you are not going to maintain a home, yard, and pool by collecting rainwater unless you have a very large surface from which to collect the water. But it's perfectly reasonable for two people to survive on 61 gallons of water per day for indoor uses such as cooking, cleaning, bathing, and drinking.
But how do you make rainwater suitable for drinking? That is the tricky part, some of which I will try to address in a post on the regulatory limitations on use of rainwater for water supply. But in a general sense, you must install a home water treatment system to make this water suitable for consumption. This ranges from selecting proper roofing material that won't leach chemicals into the water falling on it, to engineering the collection system so the first flush of water coming off the roof is bypassed (to limit the bird poop in your water supply), to a system of filters and treatment technologies that will ensure no harmful bacteria or other nasties in your water. This is the primary annual cost of this type of water supply - the energy and maintenance of the treatment system. Most of the other costs are upfront when the collection and storage are installed.
This site includes some helpful information on what is necessary for making rainwater suitable for potable uses.
Is this type of system suitable for the average homeowner? Clearly not. But there are people out there who are willing to invest the money, time, and effort to get off the grid, or off the pipes in this case, and whose lifestyle allows them to live on only the amount of water necessary for basic, indoor human needs, without all the extraneous uses of high-quality drinking water many of us find necessary for our quality of life.
More when I find the time, including the aforementioned regulatory analysis of rainwater harvesting.
Sunday, November 29, 2009
Starting to think a lot about rainwater harvesting
Life has been extremely busy lately (even before holidays started rolling into the picture) and that has kept me from posting. But the ideas have been churning, just waiting for an opportunity to emerge onto these pages.
One thing I have been spending a lot of time thinking about and discussing with various people is the viability of rainwater harvesting for domestic water supply in places like Tucson. I know of people doing it so clearly it's possible. But I've been wondering what it would take to bring it more into the mainstream and maybe even be viable as a water source for a small development - not just the individual lot scale.
One person I know of who relies on such a system in the Tucson area is in a location where municipal water service is not available and drilling a private well is unreliable. So rainwater probably was their best option. They also weren't overly concerned with the cost of the system - they had resources to cover that and because of their desire to live in a remote location any option for water supply was going to be costly. I suspect this type of situation is the primary motivator for going with rainwater as a water source.
This makes me concerned that greater use of rainwater harvesting would lead to increased sprawl - as people move to locations where previously they may not have been able to build because of the lack of a water supply. But I think the reality is that the people who would choose this type of water supply are the ones who are likely to move into remote areas regardless and harvesting gives them an option for water supply that doesn't rely on a non-renewable source - such as groundwater (under most circumstances).
I'm still putting these ideas together and plan to post on this topic over the next few weeks, where I will try to outline the feasibility of rainwater as a domestic water source and the types of changes I think would be necessary (i.e. regulatory) to permit greater use of this type of system.
One thing I have been spending a lot of time thinking about and discussing with various people is the viability of rainwater harvesting for domestic water supply in places like Tucson. I know of people doing it so clearly it's possible. But I've been wondering what it would take to bring it more into the mainstream and maybe even be viable as a water source for a small development - not just the individual lot scale.
One person I know of who relies on such a system in the Tucson area is in a location where municipal water service is not available and drilling a private well is unreliable. So rainwater probably was their best option. They also weren't overly concerned with the cost of the system - they had resources to cover that and because of their desire to live in a remote location any option for water supply was going to be costly. I suspect this type of situation is the primary motivator for going with rainwater as a water source.
This makes me concerned that greater use of rainwater harvesting would lead to increased sprawl - as people move to locations where previously they may not have been able to build because of the lack of a water supply. But I think the reality is that the people who would choose this type of water supply are the ones who are likely to move into remote areas regardless and harvesting gives them an option for water supply that doesn't rely on a non-renewable source - such as groundwater (under most circumstances).
I'm still putting these ideas together and plan to post on this topic over the next few weeks, where I will try to outline the feasibility of rainwater as a domestic water source and the types of changes I think would be necessary (i.e. regulatory) to permit greater use of this type of system.
Friday, November 6, 2009
Tucson/Pima County Water Study update
Phase II of the study, designed to map out a path to a more sustainable water future for the region is just about wrapped up (I say region even though the study only incorporated the city and county governments - not any of the other local jurisdictions - because it is hoped that the policy recommendations from this study can be applied across the region as a blueprint for water sustainability). City and county staff have just issued the draft of their Phase II report on the study website. On Monday, Nov. 9, from 6 to 9 PM they will be hosting an open house to present their report to the public and take questions.
The committee (including yours truly) meanwhile continues to pound away at a separate report that is intended to provide the community perspective on what water sustainability should mean around here. Obviously there will be considerable agreement with what the staff came up with in their report - after all, they were the ones primarily responsible for educating the committee on these issues. But there are some issues the committee would like to stress more strongly than we feel the staff report does and vice versa. The challenge though is coming up with consensus on the committee. There are divergent and strongly held opinions on some issues, but I think sufficient commonality exists for us to come together and produce a strong report. The committee meets next on Thursday, Nov. 12, in the City IT building, next to the Manning House, to continue the process of drafting our report in addition to discussing the staff report (agenda should be posted soon on the study website if it isn't already). Let's hope for harmonious policy and strong coffee that evening.
The committee (including yours truly) meanwhile continues to pound away at a separate report that is intended to provide the community perspective on what water sustainability should mean around here. Obviously there will be considerable agreement with what the staff came up with in their report - after all, they were the ones primarily responsible for educating the committee on these issues. But there are some issues the committee would like to stress more strongly than we feel the staff report does and vice versa. The challenge though is coming up with consensus on the committee. There are divergent and strongly held opinions on some issues, but I think sufficient commonality exists for us to come together and produce a strong report. The committee meets next on Thursday, Nov. 12, in the City IT building, next to the Manning House, to continue the process of drafting our report in addition to discussing the staff report (agenda should be posted soon on the study website if it isn't already). Let's hope for harmonious policy and strong coffee that evening.
Friday, October 23, 2009
What could additional budget cuts do to Arizona Dept. of Water Resources (ADWR)?
Responding to reports that state tax receipts have been running $0.5 billion below projections and the ongoing fact that our state government is unwilling and/or incapable of putting together a complete state budget for the current fiscal year, our governor has asked all state agencies to present plans detailing how they might cut an additional 15% from their budgets for the remainder of this fiscal year (until the end of June 2010). The agency that manages our water supplies has submitted their plan, which they posted on their website here (pdf document).
I am not personally aligned with any political party and am perfectly willing to criticize any politician, from any party, who advocates bad policy, resorts to fear-mongering, and otherwise panders to various vested interests, be they democrat, republican, or Bull Moose. But Arizona is currently controlled by republicans and we can only wish these were the republicans of Barry Goldwater's day. These are the kind of republicans who resolutely place ideology over common sense no matter how stubborn and stupid it makes them look (ok, there are a few moderates still in there, but they're pretty marginalized most of the time). My point is, these are the kind of people who believe the state government shouldn't be wasting tax dollars collecting basic hydrologic information. Number one - decent, god-fearing Arizona landowners don't need the government telling them how to use and manage their water. Number two - if data is so vital, there should be private sector entities that can step up and pay for it's collection. And finally - let the federal government pay to collect the data if it's really that important, just don't use that data to tell the state how to manage our water.
So what will we have to do? The report spells it out in pretty stark terms. Admittedly, the document produced by ADWR is intended to strike fear in the hearts of those who control the purse strings but with the cuts they have already endured, another 15% will absolutely cripple the ability of that agency to adequately provide management of our increasingly strained water supplies.
The plan includes eliminating the Statewide Planning Division, and reducing the Hydrology, Surface Water, and Water Management Divisions. Follow the links if you want to learn more about what those parts of ADWR do, but just as a starter those are basically all the main functions of the Department.
The Statewide Planning Division (SPD), in particular will be a huge loss. There is precious little data about water supplies and water uses in areas of the state outside of the Active Management Areas (AMA) - the rural parts of the state. The primary entity for collecting this data and helping those areas - where constraints on water supplies are often very significant because they don't have access to Colorado River water from the CAP canal - is SPD. Without them the task of developing management strategies for water supplies in those areas will fall on local entities, which have very few resources for those tasks as well as some vested interests that would prefer not to have the bad news that data might bring.
The other Divisions, which aren't being eliminated but are being cut to levels where their effectiveness will be greatly reduced, are responsible for administering surface water rights in the state, developing management plans for the AMAs, and collecting basic data to support all the other programs ADWR handles. I don't want to contend that these functions are more important than education and services for poor people (also being hammered by the current budget situation), but as someone who relies on the data and programs of ADWR for much of what I do this is grim news indeed.
I am not personally aligned with any political party and am perfectly willing to criticize any politician, from any party, who advocates bad policy, resorts to fear-mongering, and otherwise panders to various vested interests, be they democrat, republican, or Bull Moose. But Arizona is currently controlled by republicans and we can only wish these were the republicans of Barry Goldwater's day. These are the kind of republicans who resolutely place ideology over common sense no matter how stubborn and stupid it makes them look (ok, there are a few moderates still in there, but they're pretty marginalized most of the time). My point is, these are the kind of people who believe the state government shouldn't be wasting tax dollars collecting basic hydrologic information. Number one - decent, god-fearing Arizona landowners don't need the government telling them how to use and manage their water. Number two - if data is so vital, there should be private sector entities that can step up and pay for it's collection. And finally - let the federal government pay to collect the data if it's really that important, just don't use that data to tell the state how to manage our water.
So what will we have to do? The report spells it out in pretty stark terms. Admittedly, the document produced by ADWR is intended to strike fear in the hearts of those who control the purse strings but with the cuts they have already endured, another 15% will absolutely cripple the ability of that agency to adequately provide management of our increasingly strained water supplies.
The plan includes eliminating the Statewide Planning Division, and reducing the Hydrology, Surface Water, and Water Management Divisions. Follow the links if you want to learn more about what those parts of ADWR do, but just as a starter those are basically all the main functions of the Department.
The Statewide Planning Division (SPD), in particular will be a huge loss. There is precious little data about water supplies and water uses in areas of the state outside of the Active Management Areas (AMA) - the rural parts of the state. The primary entity for collecting this data and helping those areas - where constraints on water supplies are often very significant because they don't have access to Colorado River water from the CAP canal - is SPD. Without them the task of developing management strategies for water supplies in those areas will fall on local entities, which have very few resources for those tasks as well as some vested interests that would prefer not to have the bad news that data might bring.
The other Divisions, which aren't being eliminated but are being cut to levels where their effectiveness will be greatly reduced, are responsible for administering surface water rights in the state, developing management plans for the AMAs, and collecting basic data to support all the other programs ADWR handles. I don't want to contend that these functions are more important than education and services for poor people (also being hammered by the current budget situation), but as someone who relies on the data and programs of ADWR for much of what I do this is grim news indeed.
Wednesday, October 21, 2009
High Country News article on the problem of exempt wells
This is from the most recent issue of High Country News, describing the pretty much West-wide problem of exempt, or unregulated, wells - typically household wells used for domestic, livestock, and limited irrigation uses.
It's an issue that has started to come to greater prominence in a few areas (in states that recognize the connection between surface and groundwater and regulate both under the prior appropriation doctrine - sadly not the case here in Arizona).
That aside, it's a nice piece, giving a good overview of the problem and how one state - Washington - is attempting to deal with it.
It's an issue that has started to come to greater prominence in a few areas (in states that recognize the connection between surface and groundwater and regulate both under the prior appropriation doctrine - sadly not the case here in Arizona).
That aside, it's a nice piece, giving a good overview of the problem and how one state - Washington - is attempting to deal with it.
Sunday, October 18, 2009
Water Conservation in New Property Development
There was a recent article in the Wall Street Journal about the efforts of property developers along the Colorado Front Range to reduce the water impact of those properties.
I think it's fantastic that developers are embracing water conservation in a significant way, even if you consider that they really have no choice in many cases. For some areas it has become a matter of build smart or don't build at all. Or at least be happy with building something that will make a much smaller profit. But something that tends to get lost in the self-congratulatory language of these developers is that maybe the choice shouldn't be between a high-water-use development and a low-water-use development but between any development and no development.
If you're talking about a new development on untouched land I would much rather see it remain open space than see the most environmentally-conscious, low-water-use development in the world be built there. However, if you're talking about converting an existing use - farming or low-intensity development - to a new higher-intensity use, then by all means they should make every effort to limit the impact on local water supplies.
I realize it's not always so easy. When land is privately owned there are certain rights to develop land that can't just be taken away from the owner without just compensation. And often a larger-scale development offers greater opportunity to exact concessions from the developer, forcing a more limited impact on the environment than is the case when the land is divided into 36 acre ranchettes. But just because the developer is installing rainwater and gray water reuse features, and water conserving appliances doesn't make it something to be praised. After all the developer will most likely have no role in the development once built. The buyers might use just as much water as the development up the road. But for now the developer gets to be the good guy and in addition probably gets to charge a premium for homes in the development because of it's "green" features.
This stuff always warrants a closer look.
h/t to John Fleck for pointing me to the WSJ piece.
I think it's fantastic that developers are embracing water conservation in a significant way, even if you consider that they really have no choice in many cases. For some areas it has become a matter of build smart or don't build at all. Or at least be happy with building something that will make a much smaller profit. But something that tends to get lost in the self-congratulatory language of these developers is that maybe the choice shouldn't be between a high-water-use development and a low-water-use development but between any development and no development.
If you're talking about a new development on untouched land I would much rather see it remain open space than see the most environmentally-conscious, low-water-use development in the world be built there. However, if you're talking about converting an existing use - farming or low-intensity development - to a new higher-intensity use, then by all means they should make every effort to limit the impact on local water supplies.
I realize it's not always so easy. When land is privately owned there are certain rights to develop land that can't just be taken away from the owner without just compensation. And often a larger-scale development offers greater opportunity to exact concessions from the developer, forcing a more limited impact on the environment than is the case when the land is divided into 36 acre ranchettes. But just because the developer is installing rainwater and gray water reuse features, and water conserving appliances doesn't make it something to be praised. After all the developer will most likely have no role in the development once built. The buyers might use just as much water as the development up the road. But for now the developer gets to be the good guy and in addition probably gets to charge a premium for homes in the development because of it's "green" features.
This stuff always warrants a closer look.
h/t to John Fleck for pointing me to the WSJ piece.
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