Groundwater Depletion In California's Central Valley

Nasa's Gravity Recovery and Climate Experiment (GRACE) Satellite now gives us the ability to see how water both moves and is stored. This has brought attention those living within the Central Valley due to noticeable changes in our environment from our recent prolonged drought. Since we are taking more than can be recharged, what Counties will be most affected and what are the potential harms to our environment and community in the upcoming future?

This study will go over climate data to discover changes California's Central Valleys Aquifer has from the increasing population, demand for food, along with understanding how and why urban areas within the Central Valley are at risk.

Outline

1. Background
2. Analysis
3. Results
4. Conclusion

What do you think of when someone asks you about California's Central Valley? Is it the miles upon miles of Agriculture? A place consisted of endless opportunity? But what will happen to this state as we run lower and lower on our water supply.

California has done a poor job of properly managing their water control throughout the state. The state has been able to put together policies to ensure many decades a steady supply of surface water to satisfy those counties that do not have a direct source of water along with maintaining our agriculture. Now that California is in recovery from our recent drought it has left a demand for water that is more than the natural renewable supply. Meaning that since there is minimal surface water many are left with the choice to dig below and pump up the available groundwater. Though this may be a quick but costly solution, with many consequences from the extraction of groundwater. The lack of California’s groundwater resources will quickly impact agriculture, surrounding ecology, and the lives of millions of people living within the state causing many economic impacts.

Knowing the fact that California’s Central Valley is the leading agricultural area within the United States and is now quick to notice significant changes with groundwater depletion. globally in semi-arid regions with highly-variable precipitation. Roughly each year around 30-40% of California's Central Valley groundwater supply of water is used, but a great majority of it goes straight to agriculture. In recent years and especially during the years of our major drought there has been a noticeable amount of groundwater extracted for agricultural purposes that almost always surpass the natural recharge. This has already brought much attention to California's Central valley groundwater table. After California's most recent drought from 2011-2016 it has been much easier to notice the trends of depletion through agriculture and population growth.

In yellow shows the counties that consist of California's Central Valley where these counties are highly dependent on the Sacramento Valley, San Joaquin Basin and Delta, and Tulare Basin. With the recent battle for water many farmers were left to invest in wells to help keep their crop production up. By using ArcGIS and Nasa's Gravity Recovery and Climate Experiment (GRACE) Satellite we can see the harms these farmers are leaving behind.

What are some signs of Rapid depletion noticed throughout the state, and what are the potential long term effects from not properly recharging a water table?

Within the Central Valley I was able to filter percent of irrigated land and precipitation data from 1990-2011( before California's major drought) to Urban Areas and Counties that are highly dependent on agriculture growth. By selecting Urban areas that intersect from both irrigation and precipitation data over California's Aquifer we can see that 45 selected urban areas with a population average of 7 million people are at risk of Aquifer depletion.

Since this region is highly dependent on groundwater other forms of irrigation have been researched but at this point the rate of extraction is much higher than it can replenish itself. This has led to certain regions in California to deplete up to 3 feet a year, and leaving those with smaller drinking wells completely dry or contaminated. With California being ranked the leading supplier of food, losing that water table will not only put those living within the state at risk but the entire country.

Aside from the fact that California and the global population only continues to grow in size and soon our demands will be much higher that what we can supply, we are now seeing a decrease in the amount of precipitation and a increase in temperatures.

Changes in both temperature and precipitation patterns have a great affect on groundwater recharge. Aside from potential contamination and years needed for replenishment there will most likely be long term effects in regards to how long an aquifer will take to replenish itself. Considering that this is an Unconfined Aquifer meaning a great majority is located in a semiarid area will lead to more prolonged dry seasons.

What GRACE has taught us about groundwater depletion.

With the help from NASA we can see how over-pumping lowers the water table, and cause wells to dry out at a faster rate and in some cases are left to dig deeper only prolonging the total recharge. Costs to dig wells are only increasing and use more energy to pump deeper. The photo on the left shows groundwater changes over a 12 year period due to over pumping.

Since our groundwater and surface water are both linked together, this leaves many rivers and lakes to dry out or run low over time. The overuse of groundwater also can potentially lead to a collapse of water tables due to the inability to replenish itself. This also answers the question behind why we have had such high fire seasons recently with over 4,000,000 acres burned just in 2020.

From these results, we can see that California has a lot to take on in regards to Water Management. Luckily we have a foundation to work with and potential ideas such as artificial recharge, use of renewable-water, better monitoring of damaged regions to help ensure this does not continue to be an issue. With many counties claiming they are working on a more sustainable way of handling our groundwater table we are left with taking their word until policies can be put into place or might just head to a point of no return.

• Famiglietti, J. S. “Satellites Measure Recent Rates of Groundwater Depletion in California's Central Valley.” AGU Journals, John Wiley & Sons, Ltd, 5 Feb. 2011, agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL046442. 
• Worzel, Richard. “What Happens When California Runs Out of Water?” Futuresearch.com - Richard Worzel – Futurist – Speaker – Consultant, 23 June 2015, www.futuresearch.com/2015/06/23/what-happens-when-california-runs-out-of-water/. 
• Greicius, Tony. “NASA Data Show California's San Joaquin Valley Still Sinking.” NASA, NASA, 28 Feb. 2017, www.nasa.gov/feature/jpl/nasa-data-show-californias-san-joaquin-valley-still-sinking. 
• Nasa's Gravity Recovery and Climate Experiment (GRACE) Satellite imagery of California
• Calfire: Incidents
• Population information: US Census QuickFacts
• Aquifers: Map of the Principal Aquifers of the United States
• ArcGIS Groundwater project package