Tag: Water Quality

GAMA: Groundwater Ambient Monitoring and Assessment Program

The State Water Board GAMA Program and the U.S. Geological Survey have created tools to help users understand groundwater quality in California. A range of online tools allow users to access data through web maps and data querying tools.

Management Considerations for Protecting Groundwater Quality Under Agricultural Managed Aquifer Recharge

Unsustainable groundwater use in California – due in large part to historical over-pumping of aquifer systems, growing reliance on groundwater to meet irrigation and urban water demands, and increasing frequency of drought – affects all water users and threatens agricultural viability into the future, but has disproportionately impacted disadvantaged communities and jeopardizes their access to safe, clean and affordable water. To secure the availability of groundwater for all uses, the state enacted the Sustainable Groundwater Management Act (SGMA) in 2014. Groundwater Sustainability Agencies (GSAs) were charged with developing Groundwater Sustainability Plans (GSPs) to avoid undesirable effects of ongoing groundwater depletion. To meet these goals, many GSPs include managed aquifer recharge (MAR) as one of several key tools to improve groundwater sustainability.

Agricultural Managed Aquifer Recharge (AgMAR) is the act of intentionally flooding fallow, dormant, or active cropland when excess surface water is available. AgMAR has the potential to be a cost-effective and high impact form of MAR due to the large acreage of cropland throughout California. As more farmers adopt AgMAR, there is greater urgency to understand the potential water quality risks and benefits associated with recharge. While pesticides and geogenic contaminants such as arsenic pose additional water quality concerns in MAR projects, this paper focuses specifically on water quality considerations for nitrate and salts related to AgMAR activities.

Nitrate contamination of groundwater is expected to worsen into the future. However, a combination of improved nutrient management and carefully implemented AgMAR projects could improve groundwater quality faster than under business as usual. Improvements in nitrogen management practices should be prioritized to reduce current and future nitrogen (N) loading to groundwater. Furthermore, relatively clean (nitrate free) recharge water (e.g. high magnitude flood flows) should be used during AgMAR events in order to dilute incoming and existing nitrate in groundwater. AgMAR programs should prioritize sites that can recharge in longer-duration single-flooding events, such as sandier sites, to capitalize on the dilution effect and reduce biologically mediated mineralization of organic N (the conversion of organic N to nitrate).

AgMAR alone will not lead to substantive improvement in groundwater quality with respect to nitrate without concomitant improvements in current agronomic nitrogen management and sufficient water for dilution. The development of transparent and easy-to-use tools that estimate the amount of residual nitrate at the end of a growing season, the amount of water needed to dilute nitrate under AgMAR, and time of travel to groundwater will help in the successful implementation of recharge projects to avoid negative water quality externalities. Current nitrogen loading maps and locations of drinking water supply wells can be used by GSAs to get a sense of regional nitrogen loading to groundwater and help in planning and prioritizing efforts on sites to target for AgMAR.

Protecting Groundwater Quality While Replenishing Aquifers

This document represents a first step towards management guidance for on-farm recharge planners and practitioners to maximize benefits to water quality and to manage risks under AgMAR. This document is also intended to be used as a resource for communities so they can more fully participate in the GSA decision-making process.

The intent of this management brief is to build understanding of how drinking water could be affected by AgMAR and identify management considerations that can be used to design AgMAR projects that are mindful of water quality. These considerations are neither prescriptive nor meant to cover the full scope of considerations needed to implement a successful recharge project or program (i.e., analysis of soil and crop suitability, hydrogeology, water rights and availability, and conveyance infrastructure, among other topics).

Protegiendo la Calidad del Agua Subterranea Mientras se Reponen los Acuiferos

Este documento representa un primer paso hacia la guía de manejo para los administradores y profesionales de la recarga a nivel parcela para maximizar los beneficios para la calidad del agua y manejar los riesgos bajo Ag-MAR. Este documento también está destinado a ser utilizado como un recurso para que las comunidades puedan participar más plenamente en el proceso de toma de decisiones de la GSA.

La intención de este informe de manejo es desarrollar la comprensión de cómo Ag-MAR podría afectar el agua potable e identificar las consideraciones de manejo que se pueden utilizar para diseñar proyectos Ag-MAR que tengan en cuenta la calidad del agua. Estas consideraciones no son prescriptivas ni pretenden cubrir el alcance completo de las consideraciones necesarias para implementar un proyecto o programa de recarga exitosa (es decir, análisis de cultivos adecuados de suelos y cultivos, hidrogeología, derechos y disponibilidad de agua e infraestructura de flujo, entre otros temas).