Keywords:coastal aquifers, Groundwater Exchange, salinity, seawater intrusion
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.
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.
Ground water management is a major issue in California. The Governor's Commission to Review California Water Rights Law, in its December 1978 report,...
Ground water management is a major issue in California. The Governor's Commission to Review California Water Rights Law, in its December 1978 report, recommends a new ground water management law for California. During the 1978 and 1979 sessions of the California Legislature, similar bills were introduced but to date the only related legislation enacted was S8 1505 (Nejed1y, 1978) which directed the Department to identify the ground water basins of the State, including those subject to critical conditions of overdraft. Basins are to be identified on the basis of geological and hydrological conditions and consideration of political boundary lines whenever practical.
The ground water basin boundaries in this report can provide a basis for ground water management, should the Legislature enact such a program.
New ground water management legislation is needed. While some local agencies are managing ground water effectively with the limited powers available to them, increased authority would permit more extensive local development and implementation of plans for management of the storage space in the underlying ground water basin, ground water extraction, and artificial recharge.
Ground water management is an institutional and a political process. The ground water basin boundaries identified in this report respond in large part to the views of agencies expressed in the workshops and public hearings.
Three hundred fifty seven ground water basins are identified in this report as shown in Bulletin 118, California's Groundwater, 1975. Thirty-seven basin boundaries differ from those in Bulletin 118 (1975). Of these, twenty-two were in accord with local agency comments, and three were selected from among conflicting local comments. Pursuant to Section 10004 of the California Water Code, this report is submitted to the Legislature and shall become part of the California Water Plan.
The United States Department of the Interior’s WaterSMART (Sustain and Manage America’s Resources for Tomorrow) Basin Study Program is a 21st Century approach...
The United States Department of the Interior’s WaterSMART (Sustain and Manage America’s Resources for Tomorrow) Basin Study Program is a 21st Century approach to help address water supply challenges. The Southeast California Regional Basin Study (Study) takes a collaborative approach to solve local water supply and regional conveyance and storage issues.
As part of this Study, the Bureau of Reclamation’s Southern California Area Office cooperated with the Borrego Water District (BWD), Coachella Valley Water District (CVWD), Imperial Irrigation District (IID) and other interested regional stakeholders to assess water supply and demand challenges in the Southeast California region.
This Study’s report is comprised of seven chapters; they are: introduction, supply, demand, alternative strategies, alternative analysis, findings, and references. Three appendices provide additional details regarding climate change modeling results, engineering design and economic analysis.
The Study focuses on a regional area encompassing the Coachella, Borrego and Imperial Valleys. The Study addresses current and future supply and demand imbalances, provides an assessment of existing infrastructure resources, and develops options and alternatives to solve identified issues and help plan for an uncertain water supply future. The local stakeholders provided substantial informational resources on historical and projected supply and demand, and existing infrastructure.
The water districts’ background information includes numerous groundwater, urban water and integrated regional planning studies, all of which were produced and/or updated between 2010 and 2012. Extensive supply and demand studies for the Colorado River Basin and California’s Central Valley – the two imported water supply sources for the Study area – also contributed data to this Study. Reclamation’s Colorado River Basin Water Supply and Demand Study (Colorado River Basin Study) (Reclamation, 2012) and the California Department of Water Resources biennial State Water Project (SWP) report (State of California, 2012 a and b) were both completed in 2012.
Reclamation’s Colorado River Basin Study included several technical analyses related to optimal water utilization, conveyance and storage alternatives relative to climate change and future water supply uncertainty. Because the Southeast California Basin Study region is dependent on both Colorado River and SWP imports, several sections of the Study reference and/or summarize both reports extensively.
Existing data was used to develop structural and non-structural options to resolve supply-demand imbalances and future uncertainty. Non-structural options included governance, and regulatory or operational changes that could facilitate stakeholder processes to better conserve water or improve the use of existing facilities to convey and store water. Non-structural options were addressed qualitatively due to the complexity of interagency negotiations that would likely be involved.
The structural options involved an appraisal level design effort to evaluate pipeline alignments to convey water supplies between the Study stakeholders. Both the structural and non-structural options were assessed in their capability to resolve regional water supply and demand relative to future climate uncertainties.
Climate change scenarios analyzed the potential impacts increasing temperatures and changes in precipitation may have on supply and demand across the Study area. The analysis addressed both local and imported supply sources. Climate change is expected to result in increasing temperatures across the Study area and in the Colorado River and SWP basins over time. As temperatures continue to increase, annual precipitation will become more variable.
Precipitation changes may affect recharge of the Study area’s local groundwater aquifers and the Colorado River and SWP snowpacks. The climate effects on imported supply have been extensively discussed in the Colorado River Basin Study and the biennial SWP report. Increasing temperatures will increase both supply and demand uncertainty.
CVWD could see an increase in SWP supply deliveries under average or greater precipitation-snowpack conditions. Dry years or extended droughts could substantially decrease SWP deliveries. However, CVWD and IID receive the majority of their supply from the Colorado River. Future climate scenarios indicate an increased potential for lower basin shortages. As senior water right holders and under the Secretary of the Interior’s Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead, IID and CVWD would not be impacted by short-term shortage issues.
The Colorado River Basin Study analysis indicates these shortage vulnerabilities could be mitigated by up to 50% through a variety of management actions and operational changes. Each Study option was assessed as an adaptive strategy to climate change. The structural options to convey and store water in the Borrego Valley groundwater basin are not viable at the present time. A non-structural option may be more cost-effective for the Study region, have the potential to meet the Study objectives, and may offset climate change uncertainty that is impacting available imported water supplies.
Further study effort could include fostering groundwater sustainability in the Borrego Valley and promoting opportunities for additional groundwater banking between IID and CVWD in the Coachella Valley, per an October 2003 agreement. Other water and related resource options generated from discussions during the course of this Study include increasing storage opportunities at Lake Henshaw Dam, implementing best practices for flood control basins, and brackish desalination. These options may all play a greater role in diversifying the region’s water supply in the future. However, additional study is required to assess these water resource options.