The state of California has been battling a drought for the past four years which has emptied reservoirs, fallowed orchards and dried up thousands of domestic wells. It has also led to new groundwater regulations for the agriculture sector.
“Drought is not something that is uncommon in California; we have a drought every summer. We have drier years and wetter years; the average year doesn’t exist,” said Thomas Harter from the Watershed Science Center at the University of California – Davis.
However, the fact that 10 or 11 years out of the last 15 have been dry has resulted in a change in how the state operates its water system, Harter said to a room full of Midwest dairy producers at the Vita Plus Dairy Summit, Dec. 9-10 in Baraboo, Wisconsin.
First, conservation targets were set to reduce water usage. Agriculture made radical cuts in the amount of surface water applied and the land that was fallowed. “The cost to the agricultural economy has been 1.5 to 2 billion dollars,” he said.
Harter mentioned dairy production in California has not been affected as much because there was still groundwater for a go-to reservoir. The state’s valleys act as large bathtubs with mountain rock extending down below the soil surface and far beneath the valley, holding the water that seeps below the surface.
“Many of our dairies in the West are located over these sediment-filled bathtubs,” Harter said.
Typically, these groundwater basins are pumped down a bit in the summer and recharged with mountain snow and rain in the winter. During recent years of drought, this water source has not been replaced.
“This well has dropped by 40 feet every year these last four years,” he said.
There are consequences to pumping groundwater. If it gets below sea level, the salt water intrudes into the aquifer, and it is no longer suitable for pumping. Smaller, shallow wells have gone dry. Without water pressure, the land could subside. Already, some areas as large as 20 by 30 miles have seen 6 to 12 inches of land subsidence. Then there is the concern of water quality degradation and surface water depletion.
“California policy has come to a place we didn’t think was possible even five years ago,” Harter said. The state passed the Sustainable Groundwater Management Act of 2014, which is based upon two founding principles:
1. Groundwater should be managed such that future generations can enjoy that same resource as much as we enjoy it now.
2. The resource is managed locally so local agencies can respond to the needs of the area.
Sustainable is defined as not having “undesirable results,” he said. That means there cannot be chronic lowering of groundwater levels, a reduction of groundwater storage, seawater intrusion, degraded water quality, land subsidence or surface water depletions.
Under this new act, in the next 18 months, local groundwater sustainability agencies will be formed. Those agencies then have five years to develop a groundwater sustainability plan, which must include data collection, monitoring, modeling and assessment; supply management; demand management; and stakeholder engagement and management.
Harter said California currently does not monitor groundwater extraction, and it likely won’t have to do so unless the agencies fail to maintain their thresholds.
The new Groundwater Sustainability Agencies will have the discretionary authority to conduct studies, register and monitor wells, set well-spacing requirements, require extraction reporting, regulate extractions, implement capital projects and assess fees to cover costs. The state will have a supervisory role to make sure the local agencies are managing their water levels.
Local agencies are able to capture and reuse any water they can. Orange County built a massive wastewater recovery plant, while farmers are reusing water on a smaller scale. “A lot of wastewater on farms is recycled for irrigation water,” Harter said.
Some people are already asking how agricultural land can be used in wet years in hopes of replenishing the groundwater supply, such as using flood irrigation on an alfalfa field to let the water drain into the soil.
The recent drought has shifted the focus to water supply; however, another piece of the water discussion in California has been on water quality, particularly nitrates.
In the Central Valley, there are areas where 40 percent of the wells exceed the drinking water standards for nitrates. Nitrates can enter the ground from agriculture, wastewater, food processing waste, septic systems, etc. A study in 2005 looked at total groundwater nitrogen loading.
The places with the highest amounts of loading are the areas that receive manure and commercial fertilizers.
Looking at a chart of historic nitrogen fluxes, Harter said, “We’ve managed to not increase our use of synthetic fertilizer over the last 20 years, but there has been an exponential increase in dairy herd size and the associated manure we need to balance through the landscape.”
More than half of the nitrogen applied to agricultural land is in the form of synthetic fertilizer, while dairy manure accounts for one-third of applications. In terms of output, more than half of nitrogen leaves the field leached into the groundwater.
Regulating nitrogen in agriculture applications is a bit different than a wastewater treatment facility, for instance. “We have 10 million acres of irrigated land; everyone is next to each other, and we are leaking by design,” he said.
What is emerging is a three-pronged approach where farmers are responsible for recording nitrogen applications on a field-by-field basis, industry coalitions are interested in monitoring and extension is developing programs to show best management practices.
The agricultural landscape in California is intertwined in initiatives to not only improve groundwater quality but also its supply, all while maintaining its economic viability to continue to feed a growing population. PD
