Thursday, April 23, 2009

Can you say irony?

I was looking through some of the Arizona Water News postings on the Arizona Water Institute's (AWI - the same one that is being defunded by our state legislature over the summer) website recently and this piece from the Yuma Sun caught my eye because it appeared just a day before the news referred to in my post yesterday about the falling water levels in Lake Mead.

The Sun article refers to a somewhat common situation on the lower river during spring, when farmers in Imperial Valley and other places along the river must place orders for irrigation water 2-3 days in advance to give it time to come down the river to where their turnout is located. If it rains during those 2 o 3 days the farmer may decide to not take the water he ordered letting it flow down the river. From the article:
The almost .03 inches of rain was enough to cause some water users to not take the water they requested from the U.S. Bureau of Reclamation almost three days before. And that caused the river to rise about four to five feet, according to Bob Walsh, external affairs officer with the bureau.

Obviously it doesn't take much rain to alter irrigation schedules and have a big impact on river levels.
...with no place to store the excess water, it runs downstream to Yuma and into Mexico.

Las Vegas funded a project to eliminate this situation somewhat on orders from Imperial Valley. It's called the Drop 2 Reservoir, which would store water off the river, adjacent to the All-American Canal in SE California. When completed it will allow water ordered but not taken to be stored for the next call, which is supposed to save about 70,000 acre feet per year. I believe Vegas funded the project in exchange for any water saved.

I'm not sure whether water ordered but not taken is counted against a given farmers allowable water allocation in a given year - I suspect it isn't. But I'm sure there are a lot of water agencies that shudder to think that, at times, water is being released from Lake Mead that isn't used by anyone (unless farmers in Mexico are grabbing it). Do you suppose efforts will be made to tighten up management of what is currently occurring on the river if it can delay or lessen the impact of water shortages in the basin?


Delbert Grady said...

Yes, it is ironic and kind of makes you think about minor changes in deliveries (upstream) and unanticipated in-flows can cause problems on the 'tail' end of the system.

Looking on a large scale - it looks like the entire river is run like an irrigation district.

The 70000AF loss figure you quote (I believe) is attributed to the losses in the All American Canal due to seepage. However when dealing with losses in the system, both conditions (seepage and over-delivery) are probably lumped in this number.

I would also speculate to say that building Drop2 and lining the All American Canal is a good start in minimizing the losses.


Chris Brooks said...

My understanding is that the 70k ac-ft figure is just losses from water ordered but not taken. The seepage losses from the All-American canal are more on the order of 100-200k (the exact number escapes me at the moment), which is water that will go to SoCal cities in exchange for paying the cost of lining the canal.

I think an important point to consider is difference in water needs between ag and municipal uses. Fairly small investments by municipalities can free up water that is basically slop to farmers and provide enough water to supply a lot of city dwellers.

Chris Brooks said...

With the recent announcement that lining of the AA canal is complete I have seen some numbers for water savings - on the order of 70k, similar to the drop 2 savings. So I was a little off with my guess.