Addressing Nitrate in California’s Drinking Water Technical Report 6: Drinking Water Treatment for Nitrate

University of California, Davis (UC Davis) | July 2nd, 2012

The purpose of the first three sections of this document is to provide a detailed guide to the current state of nitrate treatment alternatives that can be used as a refe

The purpose of the first three sections of this document is to provide a detailed guide to the current state of nitrate treatment alternatives that can be used as a reference tool for the drinking water community. The remainder of this document focuses on nitrate treatment of drinking water in California and specifically in the Tulare Lake Basin and the Salinas Valley.

Addressing Nitrate in California’s Drinking Water Technical Report 7: Alternative Water Supply Options for Nitrate Contamination

University of California, Davis (UC Davis) | July 2nd, 2012

The Tulare Lake Basin and Salinas Valley were chosen as pilot study areas because communities in these regions are faced with the need to manage high nitrate loads from

The Tulare Lake Basin and Salinas Valley were chosen as pilot study areas because communities in these regions are faced with the need to manage high nitrate loads from agricultural lands and dairies, have a high risk of exposure to nitrate contamination in groundwater, and often cannot afford treatment or alternative water supply options. These factors combine to make the Tulare Lake Basin and Salinas Valley highly susceptible to health effects from nitrate in drinking water. There are 371 active community public water systems (CPWS) and 30 state small water systems (SSWS) in the study area (281 and 120 in the Tulare Lake Basin and Salinas Valley, respectively). These systems supply water to about 2.4 million people. An estimated additional 245,490 people in these regions get their drinking water from an estimated 74,400 private domestic wells (self-supplied households or local small water systems with fewer than five connections) that are unregulated and largely unmonitored.

Addressing Nitrate in California’s Drinking Water Technical Report 8: Regulatory and Funding Options for Nitrate Groundwater Contamination

University of California, Davis (UC Davis) | July 2nd, 2012

In the long-term, many regulatory options could reduce nitrate contamination from nonpoint sources, but some are preferable to others in terms of abatement costs; monito

In the long-term, many regulatory options could reduce nitrate contamination from nonpoint sources, but some are preferable to others in terms of abatement costs; monitoring and enforcement costs; information requirements; and the ability to raise revenue. Overall, regulation of fertilizer is easier to design, administer, and enforce than regulation of diffuse nitrate leachate discharges to groundwater. Market-based regulatory approaches (of fertilizer application or of nitrate leachate) often can achieve a water quality target at a lower cost than prescriptive standards. However, no regulatory option is without its drawbacks: e.g., regulation of fertilizer may not achieve the drinking water quality objective at all drinking water systems. Despite the existence of funding programs for safe drinking water, additional funding sources are needed. A fertilizer fee is a promising funding source that also creates incentives for dischargers to use fertilizer and water more efficiently. Farmers are currently exempt from a sales tax on fertilizer (if applied to land used for food or for feed for food animals) (CA State Board of Equalization 2004), so if this fee were set at a sales tax rate of 7.5% on the cost of nitrogen, it has the potential to raise an estimated $28 million annually, 12 nearly enough to provide alternative water supplies to the highly susceptible populations in the study area.

Addressing Nitrate in California’s Drinking Water with a Focus on Tulare Lake Basin and Salinas Valley Groundwater

University of California, Davis (UC Davis) | March 1st, 2012

In 2008, Senate Bill SBX2 1 (Perata) was signed into law (Water Code Section 83002.5), requiring the State Water Resources Control Board (State Water Board), in consultat

In 2008, Senate Bill SBX2 1 (Perata) was signed into law (Water Code Section 83002.5), requiring the State Water Resources Control Board (State Water Board), in consultation with other agencies, to prepare a Report to the Legislature to “improve understanding of the causes of [nitrate] groundwater contamination, identify potential remediation solutions and funding sources to recover costs expended by the State to clean up or treat groundwater, and ensure the provision of safe drinking water to all communities.” The University of California prepared this Report under contract with the State Water Board as it prepares its Report to the Legislature.  This executive summary focuses on major findings and promising actions. Details can be found in the Main Report and eight accompanying Technical Reports. Technical Report 1: Project and Technical Report Outline (Version July 2012) Technical Report 2: Nitrogen Sources and Loading to Groundwater (Version July 2012) Appendix, Technical Report 2: Appendix Figures to Technical Report 2 (Version July 2012) - 84 MB (large file) Technical Report 3: Nitrogen Source Reduction to Protect Groundwater Quality (Version July 2012) Technical Report 4: Groundwater Nitrate Occurrence (Version July 2012) Technical Report 5: Groundwater Remediation and Management for Nitrate (Version July 2012) Technical Report 6: Drinking Water Treatment for Nitrate (Version July 2012) Technical Report 7: Alternative Water Supply Options for Nitrate Contamination (Version July 2012) Technical Report 8: Regulatory and Funding Options for Nitrate Groundwater Contamination U.C. Davis Groundwater Nitrate Project links and updates

Agrichemicals in surface water and birth defects in the United States

Acta Paediatrica (Wiley) | March 6th, 2009

Objectives: To investigate if live births conceived in months when surface water agrichemicals are highest are at greater risk for birth defects. Methods: Monthly conc

Objectives: To investigate if live births conceived in months when surface water agrichemicals are highest are at greater risk for birth defects. Methods: Monthly concentrations during 1996–2002 of nitrates, atrazine and other pesticides were calculated using United States Geological Survey's National Water Quality Assessment data. Monthly United States birth defect rates were calculated for live births from 1996 to 2002 using United States Centers for Disease Control and Prevention natality data sets. Birth defect rates by month of last menstrual period (LMP) were then compared to pesticide/nitrate means using logistical regression models. Results: Mean concentrations of agrichemicals were highest in April–July. Total birth defects, and eleven of 22 birth defect subcategories, were more likely to occur in live births with LMPs between April and July. A significant association was found between the season of elevated agrichemicals and birth defects. Conclusion: Elevated concentrations of agrichemicals in surface water in April–July coincided with higher risk of birth defects in live births with LMPs April–July. While a causal link between agrichemicals and birth defects cannot be proven from this study an association might provide clues to common factors shared by both variables.

Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?

University of California Giannini Foundation of Agricultural Economics | May 14th, 2015

In the midst of its fourth year of drought, California now faces an estimated reduction in surface-water availability of 8.8 million acre-feet (maf) out of 29 maf in agri

In the midst of its fourth year of drought, California now faces an estimated reduction in surface-water availability of 8.8 million acre-feet (maf) out of 29 maf in agricultural applied water statewide. However, groundwater, the buffer water supply during drought, is replacing about 6.2 maf of surface water via additional pumping. This increased groundwater pumping is in addition to the 1.5 maf of annual average groundwater overdraft in the Central Valley. The net reduction of 2.6 maf in the total supply in 2015 may result in about 564,000 acres fallowed statewide, or about 120,000 more acres than last year's fallowing estimates.

Agricultural Land Stewardship (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

This resource management strategy focuses primarily on private land in agriculture including cultivated land and rangeland. Agricultural land in California comprises abou

This resource management strategy focuses primarily on private land in agriculture including cultivated land and rangeland. Agricultural land in California comprises about 31.6 million acres (California Department of Conservation, Division of Land Resource Protection, Farmland Mapping and Monitoring Program 2008). About 12.4 million of these acres are cultivated, while the remaining 19.2 million acres are rangeland (California Department of Forestry and Fire Protection 2010). Agricultural systems in California are varied in the way resources are used, ranging from intensive conventional agriculture (irrigated crop cultivation) to more extensive systems such as livestock grazing, each with a different relationship to natural resources. They also affect and are affected by surface hydrology and groundwater recharge in different ways. Stewardship of this land requires constant balancing among natural constraints, market forces, and ever-changing social expectations. Institutions and policies have been developed in response to these challenges. Public investment in water infrastructure (reservoirs, canals, drains, levees, dykes) has been in the forefront of these. This resource management strategy report focuses on agricultural land stewardship (ALS) strategies that can be incorporated into relevant adaptive management of agricultural land at different levels, including landscape, regional and project.

Agricultural Land Use in California

Public Policy Institute of California (PPIC) | June 25th, 2024

Agricultural Losses from Salinity in California’s Sacramento-San Joaquin Delta

University of California, Davis (UC Davis) | April 5th, 2014

Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California

Sea level rise, large-scale flooding, and new conveyance arrangements for water exports may increase future water salinity for local agricultural production in California’s Sacramento–San Joaquin Delta. Increasing salinity in crop root zones often decreases crop yields and crop revenues. Salinity effects are nonlinear and vary with crop choice and other factors including drainage and residence time of irrigation water. Here, we explore changes in agricultural production in the Delta under various combinations of water management, large-scale flooding, and future sea level rise. Water management alternatives include through-Delta water exports (current conditions), dual conveyance (through-Delta and a 6,700 Mm3 yr?1 [or 7500 cfs] capacity peripheral canal or tunnel) and the flooding of five western islands with and without peripheral exports. We employ results from previous hydrodynamic simulations of likely changes in salinity for irrigation water at points in the Delta. We connect these irrigation water salinity values into a detailed agro-economic model of Delta agriculture to estimate local crop yield and farm revenue losses. Previous hydrodynamic modeling work shows that sea level rise is likely to increase salinity from 4% to 130% in this century, depending on the increase in sea level and location. Changes in water management under dual conveyance increase salinity mostly in the western Delta, and to a lesser extent in the north, where current salinity levels are now quite low. Because locations likely to experience the largest salinity increases already have a lower-value crop mix, the worst-case losses are less than 1% of total Delta crop revenues. This result also holds for salinity increases from permanent flooding of western islands that serve as a salinity barrier. Our results suggest that salinity increases could have much smaller economic effects on Delta farming than other likely changes in the Delta such as the retirement of agricultural lands after large-scale flooding and habitat development. Integrating hydrodynamic, water salinity, and economic models can provide insights into controversial management issues.

Agricultural managed aquifer recharge (Ag-MAR)—a method for sustainable groundwater management: A review

Critical Reviews in Environmental Science and Technology (Taylor & Francis) | March 28th, 2022

More than two billion people and 40% of global agricultural production depend upon unsustainable groundwater extraction. Managed aquifer recharge (MAR), the practice of s

More than two billion people and 40% of global agricultural production depend upon unsustainable groundwater extraction. Managed aquifer recharge (MAR), the practice of strategically recharging water to replenish subsurface storage, is an important subbasin scale practice for managing groundwater more sustainably. However, it is not yet reaching its full potential to counterbalance growing global groundwater demand. Agricultural managed aquifer recharge (Ag-MAR) is an emerging method for spreading large volume flows on agricultural lands and has capacity for widespread global implementation. Yet, knowledge gaps, synergies, and tradeoffs in Ag-MAR research still exist. We identify six key system considerations when implementing Ag-MAR: water source, soil and unsaturated zone processes, impact on groundwater, crop system suitability, climate change and impact on greenhouse gas emissions, and social and economic feasibility. We describe the present distribution, need for common terminology, and benefits of Ag-MAR including groundwater storage, increased environmental flows, and domestic wells support. We then outline major gaps, namely, water quality impacts, and crop health and yield. We showcase the multidisciplinary approach needed for communication and coordination of Ag-MAR programs with stakeholders and the public and provide a framework for implementation. Finally, we outline a vision for the path to Ag-MAR implementation. Ag-MAR is an important approach for achieving groundwater sustainability. However, it is one of many necessary solutions and does not offset the need for groundwater conservation.