Difference between revisions of "Salinas Valley Seawater Intrusion"
(→Hydrology) |
(→Stakeholders) |
||
Line 16: | Line 16: | ||
== Stakeholders == | == Stakeholders == | ||
− | The agricultural industry in the Salinas Valley is estimated to be worth $8.1 billion<ref>http://www.miis.edu/about/newsroom/stories/node/41198</ref> and depends heavily on groundwater for almost all of its water needs<ref name=SVWP2008/>. | + | The agricultural industry in the Salinas Valley is estimated to be worth $8.1 billion<ref>http://www.miis.edu/about/newsroom/stories/node/41198</ref> and depends heavily on groundwater for almost all of its water needs<ref name=SVWP2008/>. Irrigation with high-salinity water damages crop yield, crop quality, and soil health for future use of the land for agriculture.<ref>http://www.thecalifornian.com/story/news/2014/03/05/-plan-targets-seawater-intrusion/6046831/</ref> |
− | The municipalities that lie within the Salinas Valley watershed, such as [http://en.wikipedia.org/wiki/Salinas,_California Salinas], [http://en.wikipedia.org/wiki/Castroville,_CA Castroville], [http://en.wikipedia.org/wiki/Marina,_California Marina], and unincorporated area residents rely on the aquifers for drinking water and | + | The municipalities that lie within the Salinas Valley watershed, such as [http://en.wikipedia.org/wiki/Salinas,_California Salinas], [http://en.wikipedia.org/wiki/Castroville,_CA Castroville], [http://en.wikipedia.org/wiki/Marina,_California Marina], and unincorporated area residents rely on the aquifers for urban use. When water salinity rises too high, it becomes unpalatable for drinking water and poses significant health threats. <ref>http://oceanservice.noaa.gov/facts/drinksw.html</ref> |
In addition, the businesses and communities surrounding [http://en.wikipedia.org/wiki/Lake_Nacimiento Lake Nacimiento] rely on the lake for recreational use and energy production. Despite the lake's location within neighboring San Luis Obispo County, the [http://www.mcwra.co.monterey.ca.us/index.html Monterey County Water Resources Agency] (MCWRA) manages it for the purpose of aquifer recharge and mitigation of saltwater intrusion. | In addition, the businesses and communities surrounding [http://en.wikipedia.org/wiki/Lake_Nacimiento Lake Nacimiento] rely on the lake for recreational use and energy production. Despite the lake's location within neighboring San Luis Obispo County, the [http://www.mcwra.co.monterey.ca.us/index.html Monterey County Water Resources Agency] (MCWRA) manages it for the purpose of aquifer recharge and mitigation of saltwater intrusion. |
Revision as of 17:22, 3 April 2016
A watershed-related issue examined by the ENVS 560/L Watershed Systems class at CSUMB.
Contents
Summary
Seawater intrusion into the Salinas Valley groundwater aquifers has advanced since it was first measured in 1944.[2] Currently, elevated salinity levels have been recorded less than 1/2 mile from the City of Salinas[3] at the 180-Foot aquifer[4] and is beginning to encroach beyond the city limits of Castroville at the 400-Foot aquifer[5]. The extent of seawater intrusion has moved farther inland due to continuing overdraft conditions for municipal and agricultural uses.
Location
The Salinas Valley[6] basin lies within the boundaries of Monterey County, California[7]. Groundwater is extracted from the four major aquifers: Upper Valley, Forebay, East Side, and Pressure[8]. These aquifers create an interconnected groundwater system that supplies the bulk of the irrigation and municipal water usage in the Salinas Valley.
Resources at stake
Over 524 thousand acre-feet of groundwater was extracted during the 2014 water year. 91.55% went to agricultural use and 8.45% for urban use.[8] This high dependence on groundwater for the water needs in the Salinas Valley has led to critical overdraft conditions[9] that have resulted in abandonment of agricultural and urban supply wells due to rising salinity levels[10]. The concern over adverse effects from continuing overdraft of groundwater resources has led to the development of a statewide groundwater management plan[11] and new supplemental water supplies from the Salinas_Valley_Water_Project_(SVWP).
Stakeholders
The agricultural industry in the Salinas Valley is estimated to be worth $8.1 billion[12] and depends heavily on groundwater for almost all of its water needs[10]. Irrigation with high-salinity water damages crop yield, crop quality, and soil health for future use of the land for agriculture.[13]
The municipalities that lie within the Salinas Valley watershed, such as Salinas, Castroville, Marina, and unincorporated area residents rely on the aquifers for urban use. When water salinity rises too high, it becomes unpalatable for drinking water and poses significant health threats. [14]
In addition, the businesses and communities surrounding Lake Nacimiento rely on the lake for recreational use and energy production. Despite the lake's location within neighboring San Luis Obispo County, the Monterey County Water Resources Agency (MCWRA) manages it for the purpose of aquifer recharge and mitigation of saltwater intrusion.
Laws, policies, & regulations
In 1961, Nacimiento Dam was completed to supply irrigation water to the Salinas Valley agricultural community and to recharge the aquifers. Attempts to change structural and operational practices at the dam have meet severe local opposition resulting in several lawsuits[15].
A special act district, Monterey County Flood Control and Water Conservation District, was formed in 1947 for the Salinas Valley due to early concerns about seawater intrusion and flooding problems throughout the region. It later became the MCWRA in 1991, which monitors groundwater quality and levels[16] but has had little authority in regulating groundwater extraction.
On September 16, 2014, Gov. Jerry Brown signed into law a three-bill legislative package collectively known as the Sustainable Groundwater Management Act (SGMA). The SGMA mandates the formation of Groundwater Sustainability Agencies (GSA) and will significantly increase the role and responsibilities of local and state agencies to support sustainable groundwater management. As of March 2016, a draft plan has been developed for the GSA's key actions over the next several years that includes an outline for mitigating seawater intrusion.[17]
Hydrology
Along the coast of Monterey County, fresh groundwater flowing from inland aquifers to meet with seawater from the ocean. The fresh groundwater flows from the Salinas Valley towards the coast where elevation and groundwater levels are lower. Due to the higher salinity of seawater, it is denser than fresh groundwater and has a higher hydraulic head. When the fresh groundwater aquifers within the Salinas Valley have a lower hydraulic head, seawater moves inland in a wedge shape under freshwater until head levels return to equilibrium. Seawater and fresh groundwater then mix along the transition zone through dispersion and diffusion, raising salinity levels for wells that tap into these areas.
Once seawater intrusion has taken place, the effect on drinking and irrigation water quality within the aquifer is long-lasting. Wells are typically abandoned when salinity exceeds appropriate water quality standards.
Science
- The Watsonville Water Recycling Project, uses municipal recycled water in irrigation of crops near the front of the saltwater intrusion. This was the result of a large scale study to mitigate saltwater intrusion by creating a fresh water shield between the Monterey Bay Sanctuary and the 150 ft aquifer.[18]
- Irrigation efficiency studies have been, and are continuing, to help reduce agricultural impact by reducing the quantity of water being extracted.
Scientific Tools
- Modeling has been used to help understand Salinas Valleys groundwater hydrological system. A model was used in a study of this system and described by April McMillian, for her Senior Thesis at California State University , Monterey Bay[19].
- Water Resources & Information Management Engineering, Inc. (WRIME) developed and calibrated a groundwater model and applied the criteria and IGSM to the analysis of alternatives. [20]
- The three-dimensional, finite-element-based Integrated Groundwater and Surface-Water Model (IGSM) was originally developed by Dr. Young S. Yoon in 1976 at the University of California, Los Angeles. Designed to simulate confined ground water flow, IGSM later underwent major revisions and modifications including those made during application of IGSM to the Salinas Valley Groundwater Basin[21].
- The latest Water Use Summary Report [22] developed by the Monterey County Water Resources Agency is also a good tool in understanding how groundwater is utilized in the Salinas Valley.
Future research
How this system works is understood fairly well. What is missing is the knowledge of exact quantity of water being extracted. If resources were not an issue, metering all agricultural wells to measure the exact quantity of water being extracted would be a good start. This information could be linked to the crop that was irrigated to provide information on specific crop water usage. Analysis of this information would assist agencies such as the University of California Co-Operative Extension, National Resource Conservation District, California Resource Conservation District and others to focus on educational outreach to growers on how to maximize their irrigation efficiency. Remote sensing images could be also be used to aid irrigation efficiency.
...
Notes and References
- ↑ State of the Salinas River Groundwater Basin Report (Jan. 2015)
- ↑ http://www.mcwra.co.monterey.ca.us/documents/Bulletin_52-B__1946.pdf
- ↑ https://en.wikipedia.org/wiki/Salinas,_California
- ↑ http://www.mcwra.co.monterey.ca.us/seawater_intrusion_monitoring/documents/01swi180.pdf
- ↑ http://www.mcwra.co.monterey.ca.us/seawater_intrusion_monitoring/documents/01swi400.pdf
- ↑ http://en.wikipedia.org/wiki/Salinas_Valley
- ↑ https://en.wikipedia.org/wiki/Monterey_County,_California
- ↑ 8.0 8.1 http://www.mcwra.co.monterey.ca.us/groundwater_extraction_summary/documents/2014%20Summary%20Report.pdf
- ↑ http://www.water.ca.gov/groundwater/sgm/cod.cfm
- ↑ 10.0 10.1 http://www.co.monterey.ca.us/planning/gpu/2007_GPU_DEIR_Sept_2008/Text/References/Monterey_Co_WRA_SVWP_Project_2008a.pdf
- ↑ http://www.water.ca.gov/cagroundwater
- ↑ http://www.miis.edu/about/newsroom/stories/node/41198
- ↑ http://www.thecalifornian.com/story/news/2014/03/05/-plan-targets-seawater-intrusion/6046831/
- ↑ http://oceanservice.noaa.gov/facts/drinksw.html
- ↑ McMillian, April. "Water Table Elevations in the Salinas Valley, California: Animated Visualization using GIS". California State University , Monterey Bay <http://hydro.csumb.edu/Doug/html/salinas_water_table.html> Jan. 2009.
- ↑ http://www.mcwra.co.monterey.ca.us/about/documents/MCWRA%20Agency%20Act.pdf
- ↑ http://www.water.ca.gov/groundwater/sgm/pdfs/DWR_GSP_DraftStrategicPlanMarch2015.pdf
- ↑ Need source
- ↑ http://hydro.csumb.edu/Doug/html/salinas_water_table.html
- ↑ WRIME Castroville Seawater Intrusion Project
- ↑ Review of the integrated grounjwater and surface-water model (IGSM)
- ↑ http://www.mcwra.co.monterey.ca.us/Agency_data/GEMS_Reports/2007%20Summary%20Report.pdf
Uncited
Links
- Other Watershed Issues
Disclaimer
This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.
Cite error: <ref>
tags exist, but no <references/>
tag was found