Vance Kennedy: Discouraging flood irrigation a foolish mistake

The Modesto Bee and most, if not all, of the irrigation districts’ board members appear to have accepted the idea that the public has been “ripped off” by low water charges to farmers who are using flood irrigating. I beg to differ.

In the past, a U.S. Geological Survey study of the Modesto area concluded that over half the recharge to groundwater was due to water from flood irrigation seeping past the root zone of plants and into the water table below. Because water flows easily laterally in permeable underground aquifers, the towns and cities have been able to tap into those aquifers for drinking water.

A few people want to ignore that fact completely, as did the state for years. Finally, it is now being recognized that groundwater is an indispensable source during prolonged droughts, when surface water is greatly reduced or even nonexistent.

Public officials normally react to short-term problems with short-term thinking, ignoring longer-term consequences resulting from their short-term decisions. This is happening now.

I am making certain assumptions.

▪ Global warming is a fact, and we can expect that snow in the mountains will gradually diminish into nonexistence. That means cold water for fish might not exist. Salmon in our rivers would be wiped out.

▪ Because of ocean warming, atmospheric moisture content will increase. There is already good evidence for this. With that increased moisture, when storms occur rainfall intensity may well increase. We need to see if we can benefit from that.

▪ Prolonged droughts will occur, and during them groundwater will be the only reliable source of water for everyone.

▪ Given the need for groundwater as backup, it seems obvious that every effort should be made to ensure groundwater recharge – regardless of cost.

Think of groundwater as a bank, with farmers making deposits in that bank through flood irrigation. On the other side, cities that use wells and other farmers who use drip are making withdrawals from the bank.

An excellent way to discourage farmers from recharging our groundwater supplies is to charge them more for flood irrigation. It is so easy for them to change to drip irrigation, which increases the water withdrawals from our underground bank.

In the past, farmers have been charged very little for irrigation water – a portion of which recharged the local aquifers. That is why Modesto has access to enough groundwater to last for many years of drought, even if the rivers run dry. Farmers with wells can also survive for a while.

That’s because the cheap flood irrigation of the past provided us with good drought insurance, though it was not recognized as that at the time. Society was not harmed; it simply “bought” insurance, which is now paying off. Replenishing that groundwater was a tremendous bargain.

Now, society wants to give up on insurance because of faulty short-term thinking. It is a major mistake and could cause economic disaster in the future.

Assuming global warming is true, and maintaining groundwater is critical to absolutely everyone, we should pay farmers to recharge our groundwater rather than charging them for it.

The Modesto Bee should consider this discussion and invite other hydrologists to comment. Maybe it will change the mind of its editorial board. The future of this whole society might hinge on water decisions being made now, with only short-term thinking.

This story was originally published March 19, 2015 at 5:01 PM with the headline "Vance Kennedy: Discouraging flood irrigation a foolish mistake."