Friday, April 15, 2011

All The Trends Are Right, But...

I've just updated a suite of data sets I have been keeping for about 30 years on GMD things - like water appropriated, decline rates, new water rights filed, etc.  While most of the trends are just the way we'd like to see them, the bottom line is that they are not steep enough to make a lot of difference.  I guess the good news is the problems are not getting any worse.  For all these charts, keep in mind that the district was formed in 1976, hired staff in early 1977 and got it's initial management program approved in 1978.

New Water Rights Filed:  This graph shows how quickly we got the excessive trend of new water rights under control.  What you don't see on this graph is that since about 1990 most of the new water rights were very small appropriations compared to before that time, so while we may have approved 4 new rights in 2009 for instance, the total quantity of new appropriations (water) those rights represent is quite small - especially when compared to 4 water rights that were approved in say, 1980.  You also don't see how many water rights are being removed from the system. There is a net reduction in appropriated water rights regardless of the new rights coming on line of late as we'll see below.

Appropriated vs. Pumped Acrefeet:  The fact that appropriated acrefeet are trending downward is good but it is not a steep trend.  Appropriated acrefeet are lost by certifications, abandoned/forfeited water rights or voluntary reductions/closures.  The annually pumped water is highly climate dependent and does bounce around a bit, but the longer term trend is positive (lowering) as well.

Irrigated Acres, Inseason Rainfall, Pumped Acrefeet:  Again, we see the in season rainfall trend line (blue) essentially level while the pumped water trend line (green) trending slightly downward.  This graph also shows the high correlation between in season rainfall and water pumped.  Unfortunately, the cumulative decline line (bottom line) is not reflecting all of the positive trends, albeit slow ones, which we had hoped it would.  It seems to be stuck on its inexorable downward trend.

Several things could be at work here.  Maybe all the trends are in fact short term trends and/or are not really real enough (significant enough) to affect the bottom line.  Maybe there is a lag time and we'll start seeing the positive effects of all these good trends in the near future.  Maybe the aquifer parameters are changing with depth more significantly than the reduced water use is slowing the decline rate.  It is also possible our observation well measurements aren't what they should be - I've covered that  in an earlier post.  And finally, maybe the reductions of pumping have been solely the result of water use efficiency improvements, and the consumptive water use (which is the only cause of changes in aquifer storage) has actually not changed at all.  And just maybe it's all of these things happening simultaneously.  One thing is clear - the decline problem is far more complex than most realize, and really understanding it starts with being able to measure it way better than we can now.

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