Eye On Modesto

Thoughts and observations about Modesto and Stanislaus County

Archive for the tag “Groundwater”

Board of Supervisors Meeting 10/29/13

Water drop

Water drop (Photo credit: @Doug88888)

Vance Kennedy

There has been widespread discussion of groundwater problems in the foothills.  The question seems to be “what to do about it”?  Major damage to some smaller property owners is occurring right now and that can be a complete loss of value of home and property, simply because adjacent large plantings of almonds are taking their groundwater.  An estimate of that property loss would be highly appropriate in your investigation.  Legal costs to defend these small properties are simply too expensive to individuals and are prolonged.

You have the police power to stop abuses.  Please use that power as soon as possible.  An immediate moratorium, like that in San Louis Obispo County would be very appropriate…but then what?

A rapid estimate of the problem could be made with existing knowledge by county employees, hydrologists and farmers, using present orchard records and detailed data on approved wells, plus planned almond planting and wells.  That would be a guide.

Rainfall in the low foothills is on the order of 12 inches per year.  Half may reach the water table.  Minimum irrigation needs of almond trees is estimated at 30 inches per year.  Thus, at least 2 feet of water is needed, in addition to rain.  That must come from groundwater, since there is no other source.  Because the pore space in rocks holding available water is roughly 15% (plus or minus 5%), every foot of pumped groundwater should drop the water perhaps 8 feet.  That equals 16 feet per year.  If the water table drops significantly less than that, it means that groundwater is flowing laterally underground to the well from ones’ neighbors and depleting the overall groundwater supply.  That would not be surprising, since lateral movement of groundwater is well known to be much easier than vertical movement.

There is a legal term known as “prescriptive rights”, whereby, if water is taken wrongly, and no objections occur, then at some point in time the right to object is lost.  Since there is no groundwater law in California, the time for a prescriptive right is unknown, but could conceivably be quite short.  You can control that.

A rough estimate of the magnitude of the water problem in the foothills can be made in a week.  Not a year or two, if people use reasonable estimates, as described.  There is certainly enough understanding of the problem by employees of the local irrigation districts to make valid estimates of the problem.  I cannot overstate the need to act now on requiring environmental impacts on properties adjacent to wells.  Also, grand-fathering in of continuing harmful practices absolutely must be avoided.

While I am up here, I would like to put in a plug once again for an influential county/city committee to look at the truly long term needs by our local society for food and water.  Some members of this area seem determined to make the central valley another silicon valley.  that would truly be a local and national disaster.  I believe the average local citizen is concerned but does not know how to register that concern with the decision makers.  A prominent committee could help

WATER EXPORT RULES

I would like to put in a plea that you folks approve the proposed rules on export of groundwater today.  I understand from highly reliable sources that this sort of problem was recognized at least 10 years ago and ignored.  If it had been addressed then we would probably not have the present problems.  There is a phrase to “kick the can down the road” that has been applicable in the past.  Please do not do it in this case.  If there are major unexpected problems with the rules, there is no reason why they cannot be changed in the future.

The county does need a water expert on its staff, who has legal advice available.  Neither the city or county has a lawyer knowledgeable in water precedents….I have asked.  given the tremendous importance of water at present, and even more so in the future, it is imperative that the county have such advice readily available, the sooner the better.

Rumor has it that 40% of natural river flow will be kept for the fish in the future.  Meanwhile, the state requires major increases in housing by the city.  It seems obvious that truly great water challenges lie ahead and that does not even consider potential global warming.

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Groundwater Problems In The Foothills of Stanislaus County

come on in, the water's bad

come on in, the water’s bad (Photo credit: scpgt)

By Vance Kennedy

There has been a large increase in planting of trees in the foothills of this county, especially almonds.  There is no flood irrigation to replenish groundwater, which is being pumped by increasingly deep wells.  Rainfall in the area ranges between 12 and about 16 inches per year on average, of which perhaps half recharges groundwater.

Almond trees need about 30 inches of water per year to do well.  Hence, there is on the order of two feet of water deficiency from rainfall alone.  The rest of the needed water must come from pumped groundwater.  That seems fine if you have a ready and easily available groundwater supply.  But therein lies the problem.

In the foothills the rocks are tight and much of the water must come from fractures.  Overall, an estimate of 10 percent porosity is possibly a generous estimate.  So, when one pumps out a foot of water, the water table drops 10 feet.  Since perhaps 2 feet of water must be pumped a year, that means that the water table may drop 20 feet per year or more.  Initially, the trees may do fine and the orchard can be sold to an unsophisticated buyer at a very large profit.  However, in 10 years, the water table will be down about 200 feet, or much more if the porosity is less than 10 percent.  I have heard that some very large pumps are getting water at 300 to 400 feet.  That is very expensive and cannot be justified if prices go down.  One might say that the buyer will lose and that is his problem.  There is a Latin phrase to describe the situation – Caveat Emptor – let the buyer beware.  It is not that simple.

When a well begins removing water from an aquifer, that is a water-bearing rock, there is a “cone of depression” that forms around the well, so that there is a sloping water table toward the well.  As the well goes deeper that cone of depression extends further and further from the well and ultimately will start drawing water from neighboring properties, causing their water table to drop.  California law provides no protection for that adjacent property owner.  He can be ruined, and he has no legal recourse.

There is another problem, for society as a whole.  When the tree grower has removed the groundwater to 400 feet or so and lets his trees die, that property is useless for many decades.  The water table will only be recharged by rainfall and that can raise the water table perhaps 5 feet per year.  That almond grower has literally mined a valuable resources and harmed future generations.  He has actually caused an environmental disaster, and as matters stand, there is no way of stopping him.

Mr. Kennedy is a citrus grower and a retired Hydrologist with the U.S.G.S.

 

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