Keywords:coastal aquifers, conjunctive use, Groundwater Exchange, groundwater recharge, planning and management, water supply
A new era for California’s groundwater began in September 2014 with the passage of the Sustainable Groundwater Management Act (SGMA). SGMA established a...
A new era for California’s groundwater began in September 2014 with the passage of the Sustainable Groundwater Management Act (SGMA). SGMA established a path for the sustainable management of groundwater through the formation of locally organized groundwater sustainability agencies and locally developed groundwater sustainability plans.
The purpose of this interim update is to provide up-to-date information on groundwater basins subject to critical conditions of overdraft, groundwater basin boundaries, and basin prioritization. That information is essential to the successful implementation of SGMA, including the timely formation of groundwater sustainability agencies and the development of groundwater sustainability plans.
The primary goal of the South Coast Hydrologic Region (South Coast region) groundwater update is to expand information about region-specific groundwater conditions for...
The primary goal of the South Coast Hydrologic Region (South Coast region) groundwater update is to expand information about region-specific groundwater conditions for California Water Plan Update 2013 and to guide more informed groundwater management actions and policies.
A second goal is to steadily improve the quality of groundwater information in future California Water Plan (CWP) updates to a level that will enable regional water management groups (RWMGs) to accurately evaluate their groundwater resources and implement management strategies that can meet local and regional water resource objectives within the context of broader statewide objectives.
The final goal is to identify data gaps and groundwater management challenges that will guide prioritizing of future data collection and funding opportunities relevant to the region.
This regional groundwater update is not intended to provide a comprehensive and detailed examination of local groundwater conditions, or be a substitute for local studies and analysis. Nonetheless, where information is readily available, this update does report some aspects of the regional groundwater conditions in greater detail.
Conjunctive management or conjunctive use refers to the coordinated and planned use and management of both surface water and groundwater resources to maximize...
Conjunctive management or conjunctive use refers to the coordinated and planned use and management of both surface water and groundwater resources to maximize the availability and reliability of water supplies in a region to meet various management objectives. Surface water and groundwater resources typically differ significantly in their availability, quality, management needs, and development and use costs. Managing both resources together, rather than in isolation, allows water managers to use the advantages of both resources for maximum benefit. Conjunctive management thus involves the efficient use of both resources through the planned and managed operation of a groundwater basin and a surface water storage system combined through a coordinated conveyance infrastructure.
Water is stored in the groundwater basin that is planned to be used later by intentionally recharging the basin when excess water supply is available, for example, during years of above-average surface water supply or through the use of recycled water. The necessity and benefit of conjunctive water management are apparent when surface water and groundwater are hydraulically connected. Well-planned conjunctive management that prevents groundwater depletion by maintaining baseflow to streams and support for ecosystem services not only increases the reliability and the overall amount of water supply in a region, but also provides other benefits such as flood management, environmental water use, and water quality improvement.
This study assessed the history of oil production and pressure changes in the southern portion of the San Joaquin Basin in California’s Central...
This study assessed the history of oil production and pressure changes in the southern portion of the San Joaquin Basin in California’s Central Valley as a reverse analog for understanding the pressure response to potential geologic carbon sequestration.
Sequestration involves injecting carbon dioxide into permeable strata such as those that trap oil. This results in pressure increases in the existing fluid in the subsurface that can provide a motive force for brines at those depths to migrate into groundwater, affecting its quality. The pressure can also cause differential ground surface uplift that can affect surface water flow, particularly in engineered water conveyances such as canals.
The strata underlying the Central Valley have been assessed as having considerable capacity to store carbon dioxide, but the area also contains urban areas and extensive agriculture that rely on engineered surface water delivery systems and groundwater supplies. The Stevens Sand, Temblor Formation and Vedder Formation were identified as having the largest cumulative net production from typical geologic carbon sequestration depths.
Two oil pools were identified in each of these stratigraphic units for more detailed analysis, which included converting fluid level data to pressure at the pool scale. Data were collected that allowed an assessment of the hydraulic connectivity of each unit. The results indicated that the Vedder was hydraulically connected at the near basin scale, the Stevens was hydraulically connected at the pool scale and was disconnected between pools and the Temblor was disconnected within pools. Researchers used these results to analyze possible brine leakage driven by geologic carbon sequestration. They also reviewed over 200 articles on historic groundwater contamination. They concluded that no instance of contamination due to upward leakage of brine in the Central Valley was reported.