Observations about water usage…

I’d mentioned passing along water consumption trend data collected after we completed the landscaping project described in earlier posts from 2012 here and here. I thought it made sense to postpone the comparison until after the anomalies associated with the first year could be eliminated altogether, and that meant waiting until January of 2013. I’ve created a simple Microsoft Excel graph, (below), showing the monthly usage reported by the Rain Master irrigation controller.

First, a few words on the methodology associated with how the trend data was being collected, due largely to a change I noticed in the way the data was being reported by the controller in August 2013:

  1. From September 2012 though August 2013, the controller reported cumulative usage, not month-over-month. This meant that I needed to do some simple arithmetic to calculate the monthly usage, (in gallons), then compare it to the meter reading reported by the City of Scottsdale for a basic sanity check.
  2. Starting in September 2013, and continuing up to the present, usage has been reported month-over-month, (the calculation is done for me). I suspect this change in reporting behavior was due to a firmware update, but haven’t confirmed this was, in fact, the cause. That said, it saves me a step, so I’m grateful!
  3. There was a single month – July 2013 – that didn’t follow either reporting convention noted above, so I averaged between June and August to arrive at an approximate value, (which seemed appropriate, since the programming hadn’t changed at any point in this three month period), for the purposes of the graph shown below.
  4. The Rain Master controller receives ZIP code-specific updates every 24 hours quantifying measurable precipitation, and makes tiny adjustments to the irrigation schedule to maintain some degree of consistency in terms of the water being delivered to the plants receiving irrigation. I believe this is the primary reason for the relatively small differences in irrigation for February, March and April of 2014. However, the variance between January of 2013 and 2014 cannot be attributed to the same mechanism, especially since January of 2013 was – by far – a wetter month, (nearly 3 1/2 inches of precipitation reported in January of 2013 vs. no reported precipitation in January of 2014)! As noted earlier, I opted to resort to making an educated guess, (using averages), and manipulated the data to account for an anomaly I observed between November 2012 and January 2013.


In aggregate, the 2014 utilization trend is 3.5% greater than the 2013 utilization trend for the first six months of the year – given the extreme drought conditions we’re experiencing in the Sonoran Desert, I would have expected the variance to be greater…

July 1st update: The June 2014 utilization figure, (11,274), ended up being within a few gallons of the June 2013 figure, (11,287), which isn’t all that surprising, given the similarity between last year’s average daily temperature and this year’s average daily temperature and the similarity in terms of precipitation, (or more precisely, the lack thereof). Greater water usage during what should have been the wetter months, (January, February and March), this year and then observing a convergence between last year’s trends and this year’s trends seems to make sense. We’ve heard predictions for the holiday weekend that include showers – let’s hope!

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