Before it was settled by European immigrants, California’s Central Valley was a vast floodplain. Every winter it would fill with shallow water from swollen rivers, and this water would slowly trickle into underground aquifers.
This seemed anathema to farming. The land, of course, had to be dry to cultivate a crop and harvest food. So for more than 100 years, farmers have built and maintained levees to keep floods away, even as they have been slowly exhausting the aquifers that those rivers fed over millennia.
That is all changing, thanks to California’s ongoing severe drought. A number of farmers are now realizing they can have their crops and some floodplain, too. J. Stacey Sullivan, policy director at the nonprofit group Sustainable Conservation, is guiding a major pilot project in partnership with the Almond Board of California and UC Davis. A variety of farmers have volunteered to flood their fields so the groundwater recharge performance can be carefully measured.
By quantifying the results on different soil types and crops, Sullivan hopes to erase the remaining skepticism about the concept and pinpoint the best conditions to recharge groundwater by flooding farms. He recently spent some time with Water Deeply to explain this promising and age-old idea.
Water Deeply: How did all this get started for you?
J. Stacey Sullivan: It started when we heard about Don Cameron, who owns Terranova Ranch in Fresno County, and started working with him. For many years he was putting floodwater on his land not necessarily because he was thinking of recharging his aquifer, but he was afraid of having his levees wash out, so he wanted to relieve pressure. The idea of using water for that purpose on his ranch came up in 2011. Originally most of Don’s neighbors thought he was crazy. He was putting floodwater on grapes, he was putting it on trees. Even when he was able to show his yields were as good or better, it still was sort of outside the norm.
Water Deeply: How is it being perceived now?
J. Stacey Sullivan: Don has been a real advocate for this. The attitude of most of his neighbors has changed significantly just based on what he has been able to demonstrate. When we started looking into this, we discovered there have been other growers who have looked at this from time to time. But there are still a lot of unanswered questions, and with the whole project we’re embarking on now, we’re hoping to answer a lot of those questions.
Water Deeply: How do you plan to do that?
J. Stacey Sullivan: Given the predictions of this being a wet year, we would take the work that was developed through Don, and take it to a wider geographical area and as wide a range of crop types we can manage.
At this point, we’ve had around 20 growers basically say, “We would like to take water on our land.” It translates into about 140 distinct sites, a wide range of crops, both permanent and row crops. And the idea is to apply floodwaters to these lands, then to closely monitor the results in terms of the amount of recharge that occurs.
One of the things that’s very encouraging is we’ve had a wide a range of geographical distribution and different types of crops that are represented. We’ve got almonds, grapes, prunes, people with row crops. We want as wide a range as we can. We get the best results from the demonstration that way.
Water Deeply: Isn’t this how the landscape used to work – rivers would naturally overflow their banks and flooding would recharge groundwater?
J. Stacey Sullivan: That’s correct. That’s why we have the underlying wealth of groundwater in the Central Valley that we do. That’s a basic hydrological function.
Water Deeply: Why did we move away from this?
J. Stacey Sullivan: The basic problem is, the received wisdom in agriculture is that this kind of flooding, particularly in cases of permanent crops, is a disaster. You’re going to develop crop diseases and rot and fungus and seriously affect your rootstock.
At one time, among every extension agent and agricultural commissioner in the state, it was the received wisdom that this was just a bad idea. Part of it was just a resistance to seeing flood flows as anything but a nuisance or a disaster. In general it just was one of these things that kind of was outside of the conceptual universe for people, I think.
Water Deeply: So, what kind of situation has this put us in now?
J. Stacey Sullivan: Through constructing levees and flood bypasses, we’ve pretty much completely severed the connections between rivers and their adjacent floodplains. Which obviously led to a significant reduction in this sort of annual cycle of flooding and recharge.
Water Deeply: What is the potential for groundwater recharge?
J. Stacey Sullivan: We definitely think it could be a very powerful tool for the new groundwater agencies in implementing the new Sustainable Groundwater Management Act. Obviously it’s not a panacea. It’s going to take a lot to get the groundwater situation back into balance.
But this is the kind of contribution we’d really like to make to that effort. One of differences in putting this on working lands is you don’t have to retire the lands in order to get the groundwater recharge benefit.
I know that in the Kings River Basin, if they were going to just use dedicated recharge basins to basically correct their overdraft of their groundwater aquifer, they would need to retire something along the lines of 20,000 acres in productive farmland. If you can get that recharge without having to shut down the farms, you’re in that much better shape.
Water Deeply: Could this also help reduce flood risk?
J. Stacey Sullivan: We know that, certainly where Don Cameron is, on the James Bypass on Kings River, when that floods, the city of Mendota floods. So, yes, there’s a flood protection benefit here as well. If you have people diverting these flows onto their lands, there is much less likelihood for communities like Mendota to flood.
Water Deeply: How much re-engineering of the flood-control system is required?
J. Stacey Sullivan: We’ve done some calculations about the amount of water that could be diverted onto farmland just using existing canal structures, and it’s fairly substantial. But there’s an additional fraction – a significant fraction – that would require new infrastructure. But it would be relatively low-tech, certainly compared to hard structures like dams. But we could get a fair ways down the road just with existing infrastructure.
Water Deeply: Would there be benefits to habitat and wildlife?
J. Stacey Sullivan: That’s a possibility. It’s still kind of early days as far as those conversations. But there may be some place where you could indeed provide those kinds of habitat benefits, either through groundwater moving back into streambeds, or creating wetland-type habitat.
That hasn’t been the primary focus we’re working on, but it’s come up in conversations with some other environmental organizations, and it’s definitely a possibility.
Water Deeply: What are the obstacles to doing more of this?
J. Stacey Sullivan: We’re very interested in determining what impact it has on water quality. You’ve got legacy nutrients in the soil, nitrates and what have you. In some circumstances, you could wind up mobilizing that stuff and it actually would decrease the water quality in the aquifer.
But if you apply a sufficient amount of water, you dilute that and you wind up with an improvement. This is something we really want to determine as clearly as we can because, certainly, the idea is not to compromise water quality.
We’re also involved in determining the water rights situation and making sure the irrigation districts have the appropriate water rights in terms of both the quantity of water and ability to divert at the right time of year.
There was a perception on the part of some people that these flood flows were somehow just free water there for the taking. The (state) water board has been very clear: It’s a diversion like any other diversion, and you need to be able to establish that you have a right to do it. So far, most of the water districts we’ve talked to have very solid rights.
Water Deeply: How is it going this winter? Have you been able to flood some farms?
J. Stacey Sullivan: Not yet. This is part of the impact of the drought. The reservoirs are so low and there’s so much room to get them up to full. But given the ongoing weird weather – these very warm patches we’ve been getting between rainy patches – we could be getting some significant early snowmelt.
We’re still very much in the groundwork phase, but we’re going as fast as we can because that water could be coming very soon. We’re really trying to think about it in terms of days and weeks rather than months.
Matt Weiser is a contributing editor at WaterDeeply.org. He can be reached at firstname.lastname@example.org.
Top image: A canal along a corn field is flooded on the outskirts of Tulare, Calif. (Gregory Bull, Associate Press)