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August 2011 Archives

The Importance of pH Control

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By Stephen Wiman

In addition to its effects on biological and chemical processes, the variability of pH affects our decisions in domestic water usage. High-pH water often tastes bitter and may be an indication of the scaling potential of the water. Low-pH water may lead to the dissolution of pipes, particularly copper pipes. The EPA classifies pH under unregulated Secondary Drinking Water Standards and recommends a range between 6.5 and 8.5 pH units.

The term "pH" refers to the potential of hydrogen. The scale measures the logarithmic concentration of hydrogen ions (H+) and hydroxyl ions (OH-), which constitute H2O. Because the scale is logarithmic, a change in pH by a factor of 10 results in a change of one unit on the pH scale - the pH scale ranges from 0 to 14 and is a measure of the acidity/basicity of water. A neutral solution, with a pH of 7.0, is achieved when the activity ofH+ and OH- is balanced. Water that has more free hydrogen ions (over 7) is acidic and water that has more free hydroxyl ions (less than 7) is basic or alkaline. Acids lower the pH of a solution and bases raise the pH.

Well water is typically high in ions (both positive cations and negative anions) such as calcium and magnesium (the "hardness" minerals), sodium, potassium, nitrate, chloride and sulfate. The presence of these ions decreases the activity of the H + ion and increases the activity of the OH- ions, causing the water to be higher pH. Well-water pH is a function of the minerals taken into solution as the water moves through rock strata. In Santa Fe, our municipal water, which is commonly a blend of sources, has a pH ranging from 7.04 to 8.21, with both the low and high ranges occurring in Buckman Well Field water (2010 Water Report, Sangre de Cristo Water Division).

The term "alkaline" should not be confused with the term "alkalinity;' which refers to the "buffering" capacity of water, or its ability to resist or "buffer" changes that would make the water more acidic. The main sources of natural alkalinity, which limits swings in pH levels, are rocks containing carbonate, bicarbonate, and hydroxide compounds. Borates, silicates, and phosphates may also contribute to alkalinity.

Conversely, granite, which is a common aquifer in the Santa Fe foothills, has few minerals that contribute to alkalinity. Areas rich in granite have generally low alkalinity and therefore poor buffering capacity. We sometimes see low pH in water produced from fractured granite aquifers.

In general, reverse osmosis (RO) water, although extremely pure, has inherently low pH. This is not because of the RO process per se, but is a function of the fact that RO water has such low total dissolved solids, or mineral ions, that it has little or no buffering capacity. The easiest way to raise the pH of RO water to a more palatable, and less corrosive, pH level above 7.0, is to pass it through a food- grade, NSF-certified calcium carbonate (calcite) media filter. If you buy bottled water, most of which is mass-produced by RO, you can bet that the pH has been adjusted upward.

Stephen Wiman has a background in earth science (Ph.D. in geology) and is the owner of Good Water Company in Santa Fe.  He can be reached at 505-471-9036 and skwiman @ goodwatercompany.com.

Related Links:

What is pH and How is it Measured
Good Water Company
Is Rainwater Really Safe?
The Drinking Water Book - How to Eliminate Harmful Toxins from Your Water

Drought? What Drought?

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For those of us paying attention to the weather in Santa Fe, a question increasingly coming up these days is when are we going to see watering restrictions? Especially since this is the driest it has been in a long time. Average precipitation for Santa Fe this time of year is normally 4.81 inches, and so far we have only received 0.67 inches, or 13.9% of average. It is worse for Albuquerque, which has seen only 0.19 inches thus far this year. Most of our state is experiencing a drought, as well as Arizona and Texas. Santa Fe has not seen this little precipitation since records have been kept. We should be extremely concerned about our water situation.


During our last severe drought in 2002, the city was within weeks of running out of water. The drought is even worse this year, yet thanks to actions taken by the city and our community, we are not now in the dire situation we were then. Our water supply is much more varied and our water use is down. 


Santa Fe no longer relies almost solely on the Santa Fe Water Shed for our drinking water. The number of city wells has increased from 2001 to today, (i.e. 5 more online today) our pumping capacity has increased, plus the Buckman Direct Diversion (BDD) came online in January of this year. Our available supply of water has increased to more than 22,000,000 gallons a day.  Although this supply is non-sustainable (i.e., we can't count on having this much water available in the wells, BDD, or the reservoirs in the future), it is still a major increase from what we were able to deliver a decade ago.


In years with typical snowfall and precipitation, we would now be using more water out of the Santa Fe Water Shed. Last year at about this time, our local reservoirs were at about 80% of capacity. This year they are at about 45%. So we are drawing down more of our reservoirs, and are pumping more out of the wells. These new supplies provide us an emergency insurance policy for the drought conditions we find ourselves in now. 

Since 2001, water conservation has also played a key role in providing us a more reliable water supply. Santa Fe's population grew 9.2% from 2000-2010, while our per person water usage dropped 28%. In 2001, we were using approximately 139 gallons per person per day, and today we are using less than 100 gallons per person per day.

But even with increased reserves and conservation, our current dry conditions are so severe that most of us are expecting the city to announce water restrictions. Our former tiered drought alert system, in use until recently applied a set of restrictions for each level of drought. Our city updated this system in 2007. Under Ordinance #1988-36, in Water Chapter 25,  the Water Division Director issues a drought alert based on the following set of conditions: 1) A general water supply shortage due to increased demand or limited supply; 2) Distribution or storage facilities of the city water system are inadequate to meet demand or minimum quality standards; 3) A disruption of the supply, storage, or distribution facilities of the city water or wastewater systems; 4) An unforeseeable disaster or water emergency such as an earthquake or other catastrophic event affecting the Santa Fe or Rio Grande river watershed, or groundwater supply, or other major disruption in the water supply or 5) A foreseeable water emergency, such as extended drought conditions (click on City Code and then Chapter 25).


Under this new plan, we have only emergency conditions: Orange and Red. Orange restricts watering to only twice a week and implements both pool filling and landscape planting restrictions. Red raises the bar and prohibits most landscape irrigation except with non-potable water (i.e., rainwater) and prohibits pool filling and car washing among other restrictions.


With our improved water supply and admirable water conservation efforts, don't expect Orange or Red restrictions to be announced anytime soon. However, a continued drought, fire in our water shed or any major unforeseeable event could drastically change our situation. The city of Santa Fe is doing their part; it is imperative we continue to conserve. It is one of the least expensive and most important actions we can take to ensure our water supply for today and future generations.


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Removing Algae for dripheads

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Algae is good for the plants, but very bad for the emitters so that is the dilemma. So it is a matter of balancing the filtering. Algae can be as small as .5 micron. The smaller stuff in algae is bacteria and beneficial to plants. A filter is recommended with every drip irrigation system because it removes sediment and other particles that are large enough to clog the emitters. Most tape and drip emitters can not handle up to anything large than this. So at least a 200 mesh filter MUST be used on any T-Tape system. There are, of course, smaller micron filters (i.e. a 200 mesh equals a 73 micron filter) that will take out much more. However, these are generally used in drinking water systems and not irrigation systems. Most irrigation filters you get will be this matter out without a problem.