Nitrate Contamination in California Groundwater: An Integrated Approach to Basin Assessment and Resource Protection

Abstract

Esser et al. (2002) Nitrate Contamination in California GroundwaterPage 5 of 62 Executive Summary BACKGROUNDNitrate contamination of California drinking water supplies is pervasive-about 10% of California public drinking water supply wells produce water that exceeds the regulatory drinking water limit, and a much larger fraction produce water which approaches the limit. As the population of California increases by 50% over the next 20 years, water resources will be in critically short supply. If the State can develop acceptable methods to prevent nitrate contamination of susceptible groundwaters and to remediate contaminated groundwaters, then the volume of available "new" water will be a critical benefit to California's continuing growth and prosperity.Nitrate is commonly viewed as an intractable problem for three reasons. First, nitrate contamination is ubiquitous in both surface and groundwater -a substantial number of California public and especially private groundwater wells have nitrate levels that exceed or approach regulatory limits for drinking water, and a significant fraction of surface water supplies have nitrate concentrations that would preclude their use for groundwater recharge if draft DHS regulations were adopted.  Second, the activities that contribute anthropogenic nitrate to groundwater -animal operations, crop fertilization, wastewater treatment discharge, septic systems -are ongoing and essential to the industry and commerce of the State of California.  Finally, nitrate is expensive to remove from drinking water supplies, especially in public and private systems that rely on untreated groundwater and do not have the necessary water treatment infrastructure. These factors combine to make nitrate the number-one contaminant threat to California's drinking water supply and at the same time may represent an opportunity to make important strides in providing sufficient water to meet California's future growth. A working group at LLNL has surveyed the current approach to characterizing and managing groundwater nitrate contamination in California, and has identified specific opportunities for developing better characterization methods. SPECIFIC RECOMMENDATIONS FOR GROUNDWATER NITRATE MANAGEMENT Conduct a Groundwater Basin Assessment of Nitrate Inventories and ImpactsThe ultimate goal of the Groundwater Quality Monitoring Act of 2001 (AB599) is the implementation of a comprehensive monitoring program to allow groundwater basin assessment. Assessment is a broad term still being defined by the AB599 Interagency Task Force and Advisory Board, but encompasses assessing susceptibility of groundwater to contamination, characterizing current water quality in a basin, and predicting future water quality under different conditions. To meet these goals, basin assessment must consider the current inventory of nitrate in basin soils and waters, current and past source loading, groundwater recharge and transport, An LLNL Water Initiative White Paper (LLNL-TR-466420)Page 6 of 62 and nitrogen cycling in the so...

Effect of Groundwater Age and Recharge Source on Nitrate Concentrations in Domestic Wells in the San Joaquin Valley

“…Two-thirds of the San Joaquin Valley (SJV) is used for agricultural production with an annual gross value of more than $25 billion from more than 250 different crops. − The SJV is also home to three-quarters of California’s dairy herd. In California, as in other areas in the world of intensive agriculture, the wide-spread, long-term application of fertilizers and manure is identified as the main cause of nitrate (NO 3 ) contamination of groundwater. , The fraction of applied N that leaches into groundwater as nitrates ranges from ∼5 to 50%, depending on local conditions. − In the SJV, as much as 88 kg N/ha/year may leach into groundwater in areas where fertilizers are applied. , Increasing trends in nitrate levels in SJV groundwater during the 1950s and 1960s and from the 1970s to 1980s correlated with an increase in fertilizer and manure use and an increase in the dairy herd size in confined animal feeding operations. , Among the nine hydrogeologic provinces in California, the SJV was found to have the largest area affected by high groundwater nitrate. , …”

Seasonal changes in nutrient content and concentrations in a mature deciduous tree species: Studies in almond (Prunus dulcis (Mill.) D. A. Webb)

“…leaching of nitrogen to ground water (Weinbaum et al, 1992) with nitrate levels in ground water now exceeding the maximum contamination level of 45 ppm in many parts of the world (Nightingale, 1972;Burow et al, 1998;Esser et al, 2002;Neilsen and Neilsen, 2002;Burow et al, 2008;Mangiafico et al, 2009;Clarisse et al, 2010;Viers et al, 2012). In annual crops understanding of crop nutrient demand and the application of fertilizers at rates and times consistent with crop demand has been central to the improvement of nitrogen use efficiency and the reduction in leaching potential (Di and Cameron, 2002;Meisinger and Delgado, 2002;Li et al, 2007;Gheysari et al, 2009;Fessehazion et al, 2011).…”

Public Goods and Externalities: Agri-environmental Policy Measures in the United States

“…The dead zone at the mouth of the Mississippi River in the Gulf of Mexico is in large part a consequence of nutrients and sediments from agricultural production in the humid and fertile central region of the United States (State-EPA, 2009). Human health risk from contamination of drinking water by nitrates and pesticides entering ground water supplies is a significant concern in some regions (Esser et al, 2002, Nolan et al, 1998. Endocrine-disrupters in water from pharmaceuticals used in animal enterprises are an emerging concern for impacts on the safety of drinking water for humans, and impacts on aquatic species (USEPA 2013a).…”