Saturday, October 8, 2011

Kansas Irrigation Water Use by System

I've said from the outset that I didn't think subsurface drip irrigation systems were going to save that much water - consumptive water use anyway.  I gave the industry folks the benefit of the doubt who were arguing that at least the users would pump less water.  This I said was likely, but held firm that these systems would not significantly reduce CU in our hydrologic setting.

I now read the Kansas Water Office's latest irrigation statistics report (Kansas Irrigation Water Use 2008) and notice Table 8 - Irrigation water use by system by location.  By the way, Kansas does have an excellent annual water use reporting system that is driven by a high percentage of metered water use.  The 2008 metered wells comprised 89% of all the irrigation wells in the state.  Anyway, looking at GMD areas, the reported subsurface drip system water use in 2008 was:

GMD 1:  1.09 Acft/Ac;
GMD 2:  .55 Acft/Ac; 
GMD 3:  1.41 Acft/Ac; 
GMD 4:  1.10 Acft/Ac;
GMD 5:  .86 Acft/Ac.

These reported SDI water use quantities were higher than both the flood and pivot system values for most of the 5 GMDs in Kansas.  Only in GMD 2 were the SDI values lower than the flood and pivot system numbers, and in GMD 5 lower than only the pivot irrigated acres.  This means these reported numbers were higher for some 85% of the total 12,923 SDI acres reported irrigated in the state in 2008.  I didn't expect to see this, but it seems to clearly confirm my prediction that consumptive use has not been reduced by conversion to SDI systems. 

However, it is a small sample (12,923 acres of the total 3.03 million irrigated acres) and only a single year, so I'm not going to get too excited.  Besides, when brought up before, the SDI proponents are always quick to say that it takes a little time to learn how to use the system properly, and many users over-apply in the first year or two.  Maybe, but by the time the next Irrigation Report comes out, this possible cause of higher reported water use should no longer be available.

And my new prediction is:  Even if the next report numbers show lower SDI use in Acft/Ac than the flood and pivot acres, we'll still argue about the real benchmark - what has the consumptive water use done as a result of these conversions?