Posted by: Deirdre Des Jardins | March 1, 2017

Brown administration cancels state Senate hearings on Oroville, WaterFix

The Brown administration has requested the cancellation of two hearings by the state Senate since the Oroville spillway crisis began.  The Senate Natural Resources and Water Committee scheduled a  joint hearing with the  Joint Legislative Committee on Emergency Management on “The Incident at Oroville Dam: What Happened and What Happens Next”  on February 28, 2017.   It was cancelled at the request of the administration.    The Natural Resources and Water Committee had previously cancelled a February 14, 2017 informational hearing on the California WaterFix at the request of the administration.

The Senate Natural Resources Committee website states that the hearings will be rescheduled.

Posted by: Deirdre Des Jardins | February 27, 2017

Urban Delta – 264,000 people at risk from flooding in Stockton area

The largest cities in San Joaquin County are on the eastern edge of the Sacramento-San Joaquin Delta, and include Stockton (population 292,000), Lathrop (population 18,000), and Manteca (population 72,000.) The Stockton metropolitan area is protected by a system of levees that was built between the gold rush and the 1920s.  Parts of the system were improved by the Army Corps of Engineers after the Flood Control Act of 1944.   After Hurricane Katrina, the San Joaquin Area Flood Control Agency worked with the Army Corps of Engineers to create a plan for upgrading the levees to 200 year levels of protection.  The Corps released the Draft Lower San Joaquin Interim Feasibility Study and Environmental Impact Statement / Environmental Impact Report in February 2015. The final feasibility study for the $803.7 million plan has yet to be completed.

In the interim feasibility study, the Army Corps of Engineers noted that 264,000 people live in floodplains in the Stockton metropolitan area, with $21 billion in damageable property and 23 critical structures:

The existing levee system within the study area protects over 71,000 acres of mixed-use land with a current population estimated at 264,000 residents and an estimated $21 billion in damageable property. In addition to the residents and property, the levee system protects approximately 23 structures considered to be critical infrastructure (hospitals, police and fire stations, etc.) as well as the Interstate 5 and State Highway 99 corridors.

and concluded that “[t]here is significant risk to public health, safety, and property in the project area associated with flooding” (p. 90, emphasis added.)

1Lower San Joaquin plan area levees         Source: Army Corps of Engineers feasibility study, p. 89

Seepage endangers levees

The Army Corps also explained in the feasibility study that the lower San Joaquin levees have problems with seepage, and are at risk of breaching at river stages below flood:

The potential for seepage problems to occur along the existing levees in the project area is created by discontinuous layers of coarse‐grained pervious soils (i.e., sands and gravels)… During high‐water events, water from the river can enter the pervious soil layers and then move laterally through these layers under/through the levee. Excessive seepage can erode soil within the levee and lead to a rapid collapse and subsequent breach… The risk of levee failure is not due to design deficiency or to lack of O&M of the existing levees, but to a better understanding of the mechanics of under‐seepage in the Central Valley. The project levees within the study area do not meet current USACE levee design criteria and are at risk of breach failure at stages considerably less than levee crest elevations. This is evidenced by historical levee boils and heavy seepage at river stages less than design flows.  (p. 90, emphasis added)

Because of these problems, the Army Corps estimated that the “risk and uncertainty” of levee failure was 2% a year for many levees on the lower San Joaquin.  The map below shows the levees that are at risk of failing, and the depth of flooding in a 500 year flood.   While it is extremely unlikely that all the levees would fail simultaneously, the ACE estimated that they are all at risk of failing during high flows and need remediation.

2 500 year flood depths                   Source: Army Corps of Engineers EIS/EIR, p. 86

High water perils

During the high-water periods in January and February of 2017, locals have been patrolling the Stockton metropolitan area and Delta levees, looking for signs of levee seepage or boils. Flooding southwest of Manteca was narrowly averted when a firefighter from the Lathrop-Manteca Fire District spotted a sinkhole as it was occurring.   While these efforts to protect the levees have been heroic, the stressed levees could easily fail in a flood.   Below is a picture of flooding of Stockton in 1955, from the Army Corps, giving an idea of the amount of flooding that would be experienced with major levee breaches.

3 Stockton flooding, 1955                                         Source: Army Corps of Engineers

State funding problems

The federal Water Infrastructure Improvements for the Nation Act (WIIN), passed on December 11, 2016, mandated that the Secretary of the Army expedite and give priority funding for the final Lower San Joaquin feasibility study, and authorized proceeding to planning, engineering, and design once the final feasibility study is completed.

However, there is no similar mandate at the state level for priority funding for completion of the Lower San Joaquin plan.  Proposition 1E accounting shows that line items for Lower San Joaquin planning totaled only $3.8 million in bond funds.    This was slightly more than 1/10th of 1% of the total of $2.895 billion authorized in Prop 1E for improving state plan of flood control facilities, increasing levels of flood protection in urban areas, and reducing risk of failure of Delta levees.   Almost all of the $2.895 billion in Prop 1E flood control funds has been obligated, and there is only $24.6 million in remaining unallocated funds.

Part of the funding issue was that the levees in North Stockton, which are most at risk of failing, were not part of the State Plan of Flood Control when Prop 1E was passed.   Although Prop 1E allowed the non-SPFC levees to be upgraded and added to the State Plan of Flood Control, the 2012 Central Valley Flood Protection Plan committed only to evaluating whether there was a “state interest” in upgrading the levees.   The following is from p. 51 of the 2012 Central Valley Flood Protection Plan:

Stockton Metropolitan Area – Improvements for this area include the following:

»» Improve SPFC levees along the San Joaquin River and tributary channels.

»» Evaluate the potential benefits of and State interest in local floodgates and control structures, as they relate to facilities of the SPFC in and around Stockton, and contribute to achieving an urban level of flood protection.

The Draft 2017 Central Valley Flood Protection Plan now includes upgrading both SPFC and “appurtenant” non-SPFC levees in the Stockton  area in the “urban portfolio” of projects. However, funding for the $803 million project will need to come from other bonds. Governor Brown has proposed to allocate $65 million in Proposition 1 funds for flood control in urban areas in the Delta, but that is the entire amount allocated in Prop 1 for urban flood control, and is likely also needed for emergency repairs.

This post was updated on March 1 at 5:00 pm.

Posted by: Deirdre Des Jardins | February 17, 2017

Repair of Oroville dam’s main spillway in 2009 – 7,000 square feet

Damaged Dam Safety

Part of DWR’s 7,000 square foot spillway repair    October 7, 2009

Kevin Dossey, the Senior Civil Engineer for the Department of Water Resources, Oroville Field Division, indicated in a press conference on Friday, February 10, that Oroville’s main spillway has never had a major repair.

But a May 2009 letter from DWR Deputy Director Raphael Torres to the Federal Energy Regulatory Commission (FERC) shows that DWR needed to repair 7,000 square feet of the main spillway, including large cracks on the spillway surface. Torres stated:

In April 2008, personnel from DWR’s Division of Operations and Maintenance inspected Oroville Dam’s spillway invert and walls for concrete deficiencies. While the overall condition of the spillway is good, the detailed visual and sounding inspection found areas of concrete spalling and delamination. DWR’s Division of Engineering is preparing a construction contract for maintenance repairs that will cover approximately 7,000 square feet of the spillway. The scope of the maintenance repair may include cutting, removing and replacing damaged concrete, sand blasting exposed steel rebar, injecting non-shrink grout into voids, repairing or replacing joint seals as necessary, and placing epoxy adhesive to repair large cracks on the spillway surface. To meet the California Environmental Quality Act requirements a Notice of Exemption will be filed. We anticipate work will begin in August, and should be complete by November 1, 2009. (underlining added.)

According to the U.S. Bureau of Reclamation’s Guide to Concrete Repair, epoxy resins are brittle and don’t withstand movement:

It is often very difficult to attain successful repair of cracks … It is better to leave most types of concrete cracking unrepaired than to perform inadequate or improper repairs (figures 71 and 72). The selection of methods for repairing cracked concrete depends on the cause of the cracking. If improper methods are used, cracks will usually reoccur in the repair material or adjacent concrete, and it may make the initial damage worse.

For some cracks, epoxy or polyurethane resin injection (section 38) can be used…. Epoxy resin injection can sometimes be used to seal low volume water leakage, while structurally rebonding cracked concrete members. Epoxy resins cure to form hard, brittle materials that will not withstand movement of the injected cracks.

It is currently unknown if more recent repairs to the main spillway also used epoxy resins for repair of cracks.   If the crack repairs failed during high flows, it could have caused the large hole in the spillway.   According to a U.S. Bureau of Reclamation document on Dam Safety, “Cavitation Induced Damage of Spillways,” opening of cracks or joints in concrete spillways can exacerbate cavitation, potentially causing spillway failure.

Paul Rogers and Matthias Gafney also reported in the Mercury News that cavitation was a possible failure mode in  Oroville Dam: What Made the Spillway Collapse?    The article quoted  Paul Tullis, a professor emeritus of civil engineering at Utah State University, as saying,  “It’s like a big grinder. It causes concrete to be torn apart.”

nwswarningThe California Department of Water Resources (DWR) has issued an evacuation order downstream of Oroville dam. According to an alert by KRCTV.com,

A hazardous situation has developed with the Oroville Dam auxiliary spillway. Officials say that operation of the auxiliary spillway has lead to severe erosion that could lead to a fa

Failure of the auxiliary spillway structure will result in an uncontrolled release of flood waters from Lake Oroville.

In response to this developing situation, DWR is increasing water releases to 100,000 cubic feet per second. Immediate evacuation from the low levels of Oroville and areas downstream has been ordered.

The Department of Water Resources is now anticipating failure of the auxiliary spillway within the hour.

This is a tragic development, even more so because the possibility of failure of the Oroville auxiliary spillway due to severe erosion was raised repeatedly by environmental groups and local agencies during relicensing of Oroville Dam by the Federal Energy Regulatory Commission.

California Water Research examined a 2005 legal filing in the FERC relicensing by Friends of the River and Sierra Club California which clearly described the risks of the unarmored spillway:

A single operational use or multiple operational uses (with failure to repair any preceding or cumulative damage) of the ungated spillway could result in a loss of crest control of Oroville Dam. A loss of crest control could not only cause additional damage to project lands and facilities but also cause damages and threaten lives in the protected floodplain downstream. An unarmored spillway is not in conformance with current FERC engineering regulations. (emphasis added.)

In response, the Department of Water Resources reportedly denied there was a risk of loss of crest control if the auxiliary spillway was used, but did not provide any geotechnical information for the environmental groups to examine.  The Department of Water Resources also argued that a feasibility study of armoring the auxiliary spillway with concrete should be financed as a flood control project by the US Army Corps of Engineers.  DWR never requested a feasibility study by the Corps for armoring the spillway. The armoring project was also likely ineligible for funding as an Army Corps of Engineers flood control project because DWR has the obligation of controlling releases from the dam.




Posted by: Deirdre Des Jardins | February 10, 2017

Oroville’s auxiliary spillway – crisis engineering

As of Saturday, February 11 2017, the crisis with the damaged main spillway at Oroville is continuing to unfold. The reservoir  began to spill over the 1,703 foot auxiliary spillway lip this morning, and as of 2:00 pm, the California Data Exchange Center elevation sensor shows 0.9 feet of flow over the spillway lip.

Engineers for the Department of Water Resources made a heroic, last-ditch effort to armor the auxiliary spillway.   According to a post by Capitol Public Radio:

Cement trucks have been pouring concrete at the mouth of the emergency spillway since Thursday. It had previously been a simple dirt channel.

The problem is that even rapid hardening cement takes at least two days to cure.   So if the emergency spillway has to be used on Saturday, the concrete and rock band-aid could just wash down into the Feather River.   This is desperation.

Emergency work at base of Oroville auxiliary spillway

The Department of Water Resources has long been informed of this worst-case flood scenario. The issues of the unarmored auxiliary spillway were discussed regularly with the Department of Water Resources during relicensing of Oroville by the Federal Energy Regulatory Commission (FERC), but after several years it became apparent that no action was going to be taken.   Environmental and local groups, including Sutter County, intervened in the FERC relicensing, in part to force DWR to do a study of the adequacy and integrity of the auxiliary spillway and remedy any deficiencies.

The 2007 Environmental Impact Statement for the Oroville FERC relicensing (FERC Project 2100) states:

Sutter County also requests that the Commission issue several relicensing orders, including …(2) direct the licensee to investigate the adequacy and structural integrity of Oroville dam’s ungated auxiliary spillway that may currently pose a risk to the project facilities and downstream levees in Sutter County and take all necessary actions to correct identified deficiencies; and (3) direct the licensee to investigate the levees on the Feather River, in the context of its hydroelectric, water supply and flood control operations and to repair, replace, and maintain those levees to provide appropriate levels of flood protection in light of license operations. (C-21)

The Federal Energy Regulatory Commission declined to even require a study of the adequacy of the unarmored auxiliary spillway, although it is part of the dam’s maximum rated discharge of 250,000 cfs in a maximum flood event.

Post updated on February 11, 2017.

Posted by: Deirdre Des Jardins | February 9, 2017

YCWA concerns about Oroville’s auxiliary spillway

Oroville dam is the tallest dam in the United States, but it has an auxiliary spillway that consists only of a 1,730 foot long spillway lip, that spills directly onto bare hillside.  Yuba County Water Agency (YCWA) raised concerns in 2002 about the damages that could occur from using the auxiliary spillway:

The discharge area below the emergency spillway is not armored and extensive erosion would take place if the emergency spillway were used.  The spillway road and possibly high voltage transmission towers would be impacted. (p. II-1)  Because the area downstream from the emergency spillway crest is an unlined hillside, significant erosion of the hillside would occur. (p. II-5) “The hillside between the emergency spillway and the Feather River would be subject to severe erosion when water flows over the spillway. Depending on the rate of flow, the erodable area . . . could range from 50 to 70 acres. The amount of soil, rock, and debris that would fall into the Feather River could be very large, depending on the depth of erosion. There could be damages to downstream structures, including the Thermalito Diversion Dam and Powerplant, Fish Barrier Dam, and highway bridges. If there is river channel blockage below the spillway, there could be impacts on operation of Hyatt Powerplant. (p. IV-3)

Yuba County Water Agency, Technical Memorandum on Lake Oroville Surcharge, August 2002

These concerns were raised with the California Department of Water Resources almost 15 years ago, during relicensing of Oroville dam by the Federal Energy Regulatory Commission (FERC.)

oroville-spillway

Flow down auxiliary spillway Feb 11, 2017

One of the major impacts of climate change will be on water resources. Many scientists believe that the recent, unprecedented droughts in California and other western states could be the beginning of a permanent transition to a drier climate in the region.

In California, many climate change models project significant drying in the Sacramento and San Joaquin River basins in coming decades. A 2012 study by Randy Hanson and Lorraine and Alan Flint et. al. at the USGS California Water Science Center has one of the clearest illustrations of how much drier these basins could get by the end of the century. The map below shows the projected change in discharge (outflow) from the watersheds.  The map on the far right is color coded by the reduction in discharge between 2010-2020 and the end of the century.   The orange areas show a reduction of 45% or more.

Hanson2012watershed

 

The study used NOAA’s Global Fluid Dynamics Lab climate model, which is a higher sensitivity climate model, projecting more warming for a given level of C02 in the atmosphere.   The higher sensitivity climate models are consistent with recent increases in global temperature, and generally project more drying.    The study also used the A2 (medium-high) greenhouse gas emissions scenario, which assumes that C02 in the atmosphere continues to increase.

Under the A2 scenario, the GFDL model runs projected that median flows in the entire Sacramento River watershed could decrease by 17% by 2020, and by 34% by 2100. The box and whisker plot below shows the range of projections for the change in median flows for each 20 year period, when compared with 1963-2000.    While there is a fair amount of spread in the projections, the overall trend is strongly down.    This is shown by the dashed line, which gives the mean change over all model projections for each 20 year period.  The change is not uniform, probably because the GFDL climate model captures cycles in sea surface temperatures, including the  Pacific Decadal oscillation.

Hanson2012SacRunoff

 

       Hanson2012SacRunofflabel

 

Not all global climate change models predict as much drying in the Sacramento River basin as the GFDL model used in Hanson’s study, but the ones that do are consistent not only with recent increases in global temperature, but also with the severe droughts in California, Texas, and New Mexico.   A 2009 study by Jessica Oster and Isabel Montanez et. al. at UC Davis may also corroborate the climate change models that project significant drying.   Oster analyzed the composition of layers in stalagmites in Moaning Cavern in the central Sierra Nevada.   The changes in isotopes showed that the last time the climate warmed significantly, at the end of the last ice age, it got much drier.

California is entering a new era of water management, with much greater risk and uncertainty due to climate change. Making conservation a way of life is essential to managing that risk.  For this reason, Governor Brown’s mandate to increase long term conservation targets above the 20×2020 levels is critically important for California’s cities.

Posted by: Deirdre Des Jardins | May 5, 2016

MWD’s Delta Islands Water Transfers

Bouldin Island

Bouldin Island, shown on the right, has been fallowed for dry year water transfers  (UC Davis)

Since Metropolitan Water District announced the purchase of five Delta islands, there has been a lot of speculation about the reasons for the purchase.     Jeff Kightlinger, the CEO of Metropolitan, published an op ed in the San Jose Mercury News, in which he stated that the purpose of the purchase is to preserve Delta farmland and restore wetlands.   Kightlinger also stated that the Delta Wetlands water storage project was not one of the reasons for the purchase, and that the water rights applications for the storage project are being cancelled as part of the purchase.

Kightlinger should clarify exactly which water right applications are being cancelled as part of MWD’s purchase.  The applications to divert water for the storage project were originally filed 1987 and 1993, and the State Water Board issued permits to divert water to storage on Webb tract and Bacon Island as part of Water Rights Decision 1643 in 2001.    As part of that decision, Delta Wetlands withdrew applications to divert water to Bouldin Island and Holland Tract and agreed to cancel them.   But the existing permits do give large diversion rights on Webb Tract and Bacon Island.   In 2010, the State Water Resources Control Board staff estimated the Delta Wetlands Project had the right to divert 312,000 acre feet of water to storage from December to May, and then release it during the summer.    San Joaquin County and Central Delta Water Agency both protested the project, because of issues with seepage and levee stability on neighboring islands.   San Joaquin County entered into a settlement agreement in July 2013, and Central Delta Water Agency also settled in August 2013.    An application for a dredging permit to construct the reservoirs on Webb Tract and Bacon Island is currently pending with the Army Corps of Engineers.   There is currently no indication that this application is being cancelled.

MWD also acquires other water rights with the purchase of the five Delta islands.  In addition to the Delta Wetlands water rights, the islands have more senior water rights, including riparian, pre-1914 and appropriative.  Two  of the islands have previously had acreage fallowed for drought year water transfers.   In 2009, MWD  arranged with Delta Wetlands to fallow up to 5,426 acres on Bouldin Island and 4,189 acres on Webb tract. The fallowing allowed the transfer of up to 17,941 acre feet of water to MWD under water rights licenses 1405 and 1572.    This was about 1.9 acre feet per acre. The State Water Resources Control Board determined that no CEQA analysis of the transfer was required.

In 2014, land on Bouldin Island and Webb tract was fallowed for another drought year transfer.   This time water was transferred to four Northern California water agencies that had water stored in Semitropic water bank in Kern County.    The banked water was inaccessible without the transfers, and the water agencies stated in the application that the transfer was necessary for “health and safety” supplies.    The Northern California water agencies included Santa Clara Valley Water District, Alameda Zone 7, Alameda County Water District, and the City of Tracy.    For the 2014 transfer, Delta Wetlands estimated that up to 20,734 acre feet of water would be made available by the fallowing of up to 9,550 acres of land, about 2.2 acre feet per acre.  However, an independent report by UC Davis of the 2009 MWD transfer determined that fallowing only yielded about 0.5 acre feet per acre.

The Bureau of Reclamation objected to the 2014 transfer, stating that the calculation of over 2 acre feet per acre obtained from fallowing was not supported by the history or the available science.    The State Water Board approved the transfer, based on salinity modelling by the California Department of Water Resources, and a proposed monitoring program.

 

Posted by: Deirdre Des Jardins | April 22, 2016

Controversy erupts over Santa Clara Water District’s groundwater charges

 

A controversy erupted this week over Santa Clara Valley Water District’s Fiscal Year 2017 forecast of residential and municipal (M&I) groundwater charges. On April 19, Restore the Delta strongly criticized the District for including the WaterFix / Delta tunnels costs in the projected charges, and questioned the District’s forecasts of impacts on cities and residential well users. The District issued its own strong rebuttal on April 20. But the District’s rebuttal raises more questions than it answers.

Groundwater charges are rapidly increasing

The District’s 10 year forecasts of groundwater charges have increased dramatically in recent years. This forecast is from January 13, 2015:

And this forecast is from April 12, 2016:


As the table below shows, between January 2015 and April 2016, there was an increase of 34% in projected out year charges for North County, and 11% in South County.

SCVWD forecast groundwater charges – 2025

 

 Jan 2015   

April 2016

% increase 

North County    

$1695                  

$2332                  

34% 

South County    

$519                    

$604                    

11% 

The main cause of the increase appears to be low “placeholder” cost estimates for the water recycling program in the FY 2016 budget. The estimates for this program went from a $123.9 million placeholder in January 2015, to $924.1 million in April 2016.

Are estimates of the WaterFix impacts on groundwater charges too low?

Restore the Delta expressed strong concerns that the costs used for the California WaterFix in the FY 2017 budget are also too low — “ridiculously rosy.” The District has strongly disputed this. The table below shows the difference between the WaterFix groundwater charges used in the FY 2017 forecast (April 13, 2016 Agenda, p. 52) and the groundwater charges in the WaterFix High Cost Scenario from presented to the County Water Commission as part of the “Business Case.” (April 13, 2016 Agenda, p. 85.)

WaterFix – SCVWD forecast groundwater charges

 

FY 2017 

High Cost Scenario 

North County 

$75 

$316 

South County 

$38 

$229 

Using the numbers from the Business case for the WaterFix, one can estimate the following maximum total groundwater charges by 2026. The current and previous fiscal years are included for comparison.

SCVWD M&I Groundwater charges

 

FY 2015

FY 2016

2026 (FY 2017 forecast)

2026 (w/ High WaterFix costs)

North County

$747 / af 

$894 / af 

$2332 / af 

$2648 / af 

South County 

$319 / af 

$356 / af 

$604 / af 

$795 / af 

These estimates show that under the High Cost Scenario, the total groundwater charges for the South County could rise to 2.5 times the FY 2015 costs. The North County charges could rise to 3.5 times the FY 2015 costs. Between 2016 and 2026, the South County Costs could double, and the North County costs could almost triple.

District’s internal forecasts for the High Cost scenario

After Restore the Delta released estimates of the potential increases in groundwater charges under the WaterFix High Cost Scenario, the District staff pointed out that the estimates are somewhat high, because the WaterFix Business Case uses cost projections for 2029 rather than 2026. The staff released an internal forecast for the 2026 groundwater charges under the WaterFix High Cost Scenario.

SCVWD forecast M&I Groundwater charges — 2026

 

FY 2017 forecast

w/ High WaterFix

costs 

Difference

North County 

$2,332 / af

$2,510 / af

7.6% 

South County 

$604 / af 

$754 / af 

25 % 

Under the District’s projections for the High Cost Scenario, the 2026 South County M&I groundwater charges would increase by 2.4 times over FY 2015, while the North County charges would increase by 3.4 times. Between the current fiscal year (2016) and 2026, the South County charges would double, and the North Country charges would almost triple. The District has yet to release the full internal groundwater charge forecasts for the High Cost Scenario.

The District’s FY 2017 budget also discloses $124.9 million in unfunded capital projects, including seismic retrofits at two dams. The April 2016 presentation notes that water rates will need to increase to pay for them.

 

Posted by: Deirdre Des Jardins | April 9, 2015

Climate Change Adaptation: Match Crops to Climate

There has been a huge public debate recently about the use of water for agriculture in California, and whether farmers should be growing almonds, alfalfa, and other water-intensive crops in the state.

But California is not all arid desert, as the rainfall map below shows. So the problem is not growing water-intensive crops in California, but growing them in the driest areas in the state. The arid scrubland on the southern floor of the San Joaquin Valley gets about 7-8 inches of rain a year. The farmland in this region was traditionally used for grazing and low-water use crops such as winter wheat. But a huge boom followed the completion of the Central Valley Project and the State Water Project, which brought abundant and cheap Delta water via the Delta-Mendota Canal and the California Aqueduct. The arid land in the southern San Joaquin Valley was relatively inexpensive, and huge tracts became available when the oil companies divested in the 1990s. In the 2000s, a period of relatively wet years and an increase in State Water Project pumping brought even more water to the region. That decade saw an even greater boom in agricultural productivity, farmland value, and farm income. But the 2000s boom was completely unsustainable. The crops that were planted to increase farm income used more water than was available in all but the wettest years. As a result, groundwater levels, which had recovered after the Central Valley Project and State Water Project were completed, began dropping precipitously.


Source: Western Regional Climate Center

 

Source: USGS California Water Science Center

 

A major cause of groundwater depletion was the expansion of permanent crops, including almonds and pistachios. Almonds in the southern San Joaquin Valley need about 46 inches of water a year, and with cover crops, they need about 53 inches. In this very dry region, all but 7 to 8 inches of this water must come from irrigation – from 3 to almost 4 feet of water per acre. The problem is that even in normal years, very few growers get that much surface water. Many get less than two acre feet per acre. So the growers put in wells and pump 1-2 acre feet of water a year, and twice that amount in droughts. Alfalfa, which is grown to feed dairy cows, cattle and sheep in the Tulare Lake region, is also very water intensive. Alfalfa needs about 53 inches of water a year. About 45 inches must come from irrigation – almost four feet of water. Almonds and alfalfa are two of the major crops in the Tulare Lake Region, and have greatly expanded. The result has been an enormous drawdown in groundwater in the area, even before the drought.

In a dry year, these crops need even more water, and almost all of it must come from groundwater. These cropping patterns are completely unsustainable. In the critical drought of 2014-2015, they have resulted in drying up of 1,000 wells in Tulare County alone.

Better crops for this arid region include vegetables, which take 22-30 inches of water, and grain and grain hay, which take 23 inches of water. The net irrigation requirement for these crops is about 14-23 inches in a normal year. This would require no extra groundwater in most years, and allow groundwater levels to recover. Switching to row crops, which are more labor intensive, would also increase farmworker employment in the area.

 

 

« Newer Posts - Older Posts »

Categories

%d bloggers like this: