Sunday, March 29, 2015

Ask the expert: Davis’ groundwater future is unknown

From page A1 | February 07, 2013 |

* Editor’s note: This is the third in a series of “Ask the expert” columns that will appear in the coming days, in advance of the Measure I election, regarding various technical aspects of the city’s water utility and the proposed Woodland-Davis surface water project.

The expert: Graham Fogg, UC Davis professor of hydrogeology. Fogg’s academic interests include groundwater contaminant transport, groundwater basin characterization and management, geologic/geostatistical characterization of subsurface heterogeneity for improved pollutant transport modeling and numerical modeling of groundwater flow and contaminant transport.

The question: How long can Davis survive with the current well water system and have safe, drinkable water? Can you briefly describe the problems that could arise with the city’s drinking water, in terms of supply and quality, if Davis remained on a well-only system, and when those problems might occur?

The answer: Research indicates that downward movement of contaminated groundwater is a long-term and ongoing process and the deeper groundwater quality potentially will continue to degrade in the coming decades even in the unlikely event that anthropogenic contamination at the surface is eliminated.

In other words, the current well water system, which does include a number of aged wells that need to be replaced, is sufficiently vulnerable to ongoing contamination from surrounding land uses that it would be prudent to consider alternative or supplementary sources of water.

One alternative is to construct more wells in the so-called deep aquifer, which is perhaps more protected from surface contamination because of its depth beneath still more clay and silt layers.

Unfortunately, the capacity of the deep aquifer to satisfy city water demand is unknown at this time because there is not yet enough information on the lateral extent of that aquifer and on how and at what rate it is recharged.

Even if such information becomes available, however, concentrating more groundwater pumpage in the deep aquifer will only accelerate the downward movement of contaminated groundwater toward the deep aquifer. In other words, just because the deep aquifer is deep does not mean it is invulnerable to contamination. When I arrived in Davis in 1989, the intermediate depth aquifer zones that Davis has tapped also were considered invulnerable to contamination. Twenty-four years later it is a different story.

How long can Davis survive with the current well water system? Perhaps one to three decades. Can Davis survive significantly longer if it taps into the deep aquifer? Answer: Unknown, and unlikely to be known until substantially more development of the deep aquifer occurs. The costs of different options must be weighed, but one should also weigh the different degrees of uncertainty inherent to these options.

The main problem with staying on wells likely would be significant uncertainty regarding future capacity of the aquifer system to deliver sufficient volumes of water that meet drinking water standards, both with respect to anthropogenic contaminants (e.g., nitrate and salinity from irrigation) and natural contaminants such as selenium and chrome.

Because the amount of water the aquifer can safely yield is unknown, it is also possible that development of that aquifer will lead to overdraft conditions. In the case of groundwater overdraft, the possible detrimental effects are land subsidence, higher energy costs of pumping from deeper static water levels and intrusion of deep saline groundwater that lies below the deep aquifer.



Enterprise staff

  • Recent Posts

  • Enter your email address to subscribe to this newspaper and receive notifications of new articles by email.

  • .


    Davis sewage to get new digs

    By Dave Ryan | From Page: A1

    Where do Davis recyclables go?

    By Felicia Alvarez | From Page: A1 | Gallery

    UCD faculty receive lowest pay in the system

    By Tanya Perez | From Page: A1

    Motive for murder-suicide remains a mystery

    By Lauren Keene | From Page: A1, 1 Comment | Gallery

    Human Relations Commission hosts Chávez celebration

    By Special to The Enterprise | From Page: A2

    Davis Flower Arrangers meet Wednesday

    By Enterprise staff | From Page: A6

    ‘Music as Medicine’ is radio show topic

    By Enterprise staff | From Page: A6

    Friendship the topic on radio program

    By Enterprise staff | From Page: A6



    Milt Prigee cartoon

    By Special to The Enterprise | From Page: B4

    Some ‘survey’ …

    By Letters to the Editor | From Page: B4

    These results were meaningless

    By Letters to the Editor | From Page: B4

    Survey not representative

    By Letters to the Editor | From Page: B4

    Answers on the green waste program

    By Special to The Enterprise | From Page: B4

    A phone call could have fixed this

    By Special to The Enterprise | From Page: B4

    Universities need more funding

    By Special to The Enterprise | From Page: B5

    Mayor’s corner: Looking ahead to spring

    By Dan Wolk | From Page: B5 | Gallery

    A Little Respect for Dr. Foster

    By Nicholas Kristof | From Page: B5

    Father of the bride snubbed

    By Special to The Enterprise | From Page: A8

    Which experiences count as ‘once in a lifetime’?

    By Marion Franck | From Page: A8

    After a month of no TV news, I’m feeling much better

    By Debra DeAngelo | From Page: A8

    Take a hike for your heart

    By Special to The Enterprise | From Page: A8



    Aggie softball splits doubleheader

    By Enterprise staff | From Page: B1

    Republic stun Galaxy with repeated history

    By Enterprise staff | From Page: B1

    Bad fourth quarter sinks boys lacrosse

    By Enterprise staff | From Page: B1

    Aggies’ walkoff win clinches series against Riverside

    By Enterprise staff | From Page: B1 | Gallery

    Burns scores shootout winner to lift Sharks

    By The Associated Press | From Page: B2 | Gallery

    UCD women’s tennis dominates at home

    By Enterprise staff | From Page: B10 | Gallery







    Millennials are changing our community

    By Rob White | From Page: A9

    With new owner, DAC will Get Fit

    By Wendy Weitzel | From Page: A9 | Gallery

    Grant writing for non-profits workshop set

    By Special to The Enterprise | From Page: A9





    Comics: Sunday, March 29, 2015

    By Creator | From Page: B8