Difference between revisions of "Salinas Valley Seawater Intrusion"

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<ref>Monterey County Water Resources Agency. Quarterly Ground Water Levels. <http://www.mcwra.co.monterey.ca.us/> March 2006.</ref>
 
<ref>Monterey County Water Resources Agency. Quarterly Ground Water Levels. <http://www.mcwra.co.monterey.ca.us/> March 2006.</ref>
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<ref>http://www.salinasvalleywatercoalition.org/whoarewe.html</ref>.
  
 
== Links ==
 
== Links ==

Revision as of 16:04, 3 April 2016

A watershed-related issue examined by the ENVS 560/L Watershed Systems class at CSUMB.

Seawater intrusion into groundwater aquifers from 1944 through 2013. The 180-Foot (left) and 400-Foot (right) aquifers are the two main water supply aquifers within the Salinas River Groundwater Basin. Images from State of the Salinas River Groundwater Basin Report (Jan. 2015) [1]

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].

The municipalities that lie within the Salinas Valley watershed, such as Salinas, Castroville, Marina, and unincorporated area residents rely on the aquifers for drinking water and other urban use.

In addition, the businesses and communities surrounding Lake Nacimiento rely on the lake for recreational use and electricity generation. Despite the lake's location within neighboring San Luis Obispo County, the Monterey County Water Resources Agency manages it for the purpose of aquifer recharge and mitigation of saltwater intrusion.

Laws, policies, & regulations

Currently, groundwater resources are unregulated. The Monterey County Water Resource Agency monitors groundwater quality and levels but has little authority in regulating groundwater extraction. 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.[13]

Systems

Once saltwater intrusion begins, it is irreversible[14]. Our best hope is to stop its current progress and to modify our use of this resource so it will not continue in the future. Saltwater intrusion effects drinking and irrigation water quality, forcing some to search for alternative sources when the salinity of the water exceeds appropriate water quality standards. If salt levels are too high, the water becomes unpalatable for human consumption. Irrigation using water with high levels of salt will damage crops and soil health reducing future use of the land for agriculture.

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.[15]
  • 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[16].
  • Water Resources & Information Management Engineering, Inc. (WRIME) developed and calibrated a groundwater model and applied the criteria and IGSM to the analysis of alternatives. [17]
  • 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[18].
  • The latest Water Use Summary Report [19] 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.


Hugo A. Loaiciga and Thomas J. Pingel from the Department of Geography at the University of Santa Barbara, conducted a poster presentation addressing the assessment of seawater intrusion potential from sea level rise in coastal aquifers of California. Considering the probable impacts of global climate change which includes the threat of sea level rise, future studies will have to directly address increases in level while examining sea water intrusion into coastal aquifers. The Oxnard Plain aquifer in Ventura County and the Salinas Valley coastal aquifer (Seaside Area) in Monterey County have been studied for the threat of sea-level rise. FEFLOW and ArcGIS were used as modeling and analytical tools. The image on the left from UNEP and WMO shows sea level rise due to global warming.
alt text
The results of this study which began in September 2007 and ended in July of last year will impact future sea water intrusion studies to consider global climate change in their analysis. Click on the link to see the poster presentation File:Spatial poster presentation.pdf.






...

Notes and References

  1. ↑ State of the Salinas River Groundwater Basin Report (Jan. 2015)
  2. ↑ http://www.mcwra.co.monterey.ca.us/documents/Bulletin_52-B__1946.pdf
  3. ↑ https://en.wikipedia.org/wiki/Salinas,_California
  4. ↑ http://www.mcwra.co.monterey.ca.us/seawater_intrusion_monitoring/documents/01swi180.pdf
  5. ↑ http://www.mcwra.co.monterey.ca.us/seawater_intrusion_monitoring/documents/01swi400.pdf
  6. ↑ http://en.wikipedia.org/wiki/Salinas_Valley
  7. ↑ https://en.wikipedia.org/wiki/Monterey_County,_California
  8. ↑ 8.0 8.1 http://www.mcwra.co.monterey.ca.us/groundwater_extraction_summary/documents/2014%20Summary%20Report.pdf
  9. ↑ http://www.water.ca.gov/groundwater/sgm/cod.cfm
  10. ↑ 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
  11. ↑ http://www.water.ca.gov/cagroundwater
  12. ↑ http://www.miis.edu/about/newsroom/stories/node/41198
  13. ↑ 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.
  14. ↑ Need source
  15. ↑ Need source
  16. ↑ http://hydro.csumb.edu/Doug/html/salinas_water_table.html
  17. ↑ WRIME Castroville Seawater Intrusion Project
  18. ↑ Review of the integrated grounjwater and surface-water model (IGSM)
  19. ↑ http://www.mcwra.co.monterey.ca.us/Agency_data/GEMS_Reports/2007%20Summary%20Report.pdf


Uncited

[1]

[2] [3].

Links

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.
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