Friday, April 15, 2011
All The Trends Are Right, But...
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.