Monday, June 21, 2021

Groundwater Dependent Ecosystems and SGMA


Is this a Groundwater Dependent Ecosystem?

People enjoy the last of a drying river on Memorial Day,
Ventura River Preserve 5-31-2021 

Flows rapidly dropped through the Ventura River Preserve this year, leaving the riverbed dry by June.  While this can be a common occurrence in dry years, surface flows are directly related to the groundwater below.  Under the State Groundwater Management Act (SGMA), the local Upper Ventura River Groundwater Sustainability Agency (UVRGSA) has been formed to develop a plan to sustainably manage groundwater into the future.  Draft documents have been released in preparation for a Draft Sustainability Plan later this year.

The question of how to determine whether a reach of the river is "connected" to groundwater, and therefore a "Groundwater Dependent Ecosystem" (GDE) under SGMA, is critical to the future sustainability of our water supply.  When a Groundwater Dependent Ecosystem suffers due to groundwater overdraft, the capacity of the landscape to store water can be compromised.    

The following comments were submitted to the UVRGSA regarding this concern.  The technical documents and other references are linked below. 

DATE: 6-18-2021 RE: Early Comments on Draft Supporting Documents for Upper Ventura River Groundwater Sustainability Plan

This memo is a follow up from our conversation regarding development of the Groundwater Sustainability Plan (GSP). The primary concern we discussed is the elimination of large portions of the basin from SGMA oversight through the assumption that surface water is somehow “disconnected” from groundwater. Apart from the fact that there are fundamental flaws in the methodology used to make this determination, the resulting conclusions and management criteria are not consistent with avoiding undesirable results.

The primary Sustainable Management Criteria (SMC) for the UVRGB is the Depletion of Interconnected Surface Water. The analyses presented to date do not adequately assess the groundwater/surface water interactions within and between the different reaches of the basin, or even acknowledge the impact of groundwater pumping on surface flows.

Screening Groundwater Dependent Ecosystems (GDEs)

The Upper Ventura River Groundwater Basin is a shallow alluvial aquifer integral to the riparian floodplain ecosystem of the main stem Ventura River. Throughout these reaches of the river, groundwater and surface water are connected, and to suggest they are not is to undermine the intent of the Sustainable Groundwater Management Act.

Figure 2. Confirming whether an ecosystem is connected to groundwater, TNC

The Riparian Groundwater Dependent Ecosystems Assessment Report characterizes the Robles reach as a “Losing reach with generally disconnected groundwater- surface water.” This categorization eliminates the majority of this Groundwater Dependent Ecosystem from consideration under SGMA by assuming that it is “disconnected” and thus has too great a depth to groundwater to support riparian habitat. Other reaches are similarly dismissed.

Figure 2 from Riparian Groundwater Dependent Ecosystems Assessment

The analysis presented relies heavily on the Nature Conservancy “Natural Communities (NC) Dataset,” using vegetation communities to eliminate GDE polygons from the Upper Ventura River Groundwater Basin. The NC dataset is a statewide geographic computer database that maps vegetation types in all potential GDEs throughout the State of California. The large geographic scope of this map does not accurately represent current on-the- ground conditions, and more robust ground truthing should be undertaken. Even the aerial photos presented tell a different story than is acknowledged in the narrative (i.e. Figure 6 North Robles Habitat Area Photographs, Aquatic GDE Characterization report)

Figure 6 North Robles Habitat Area Photographs

Unfortunately, the UVRGSA analysis does not fully implement the Best Practices for using the NC Dataset guidance provided by the Nature Conservancy, which presents six best practices for using local groundwater data to confirm whether mapped features in the NC dataset are supported by groundwater. (Best Practices for using the NC Dataset, TNC July 2019)

According to this guidance:  

While depth-to-groundwater levels within 30 feet of the land surface are generally accepted as being a proxy for confirming that polygons in the NC dataset are supported by groundwater, it is highly advised that fluctuations in the groundwater regime be characterized to understand the seasonal and interannual groundwater variability in GDEs. (see Best Practice #2.)

one of the key factors to consider when mapping GDEs is to contour depth-to- groundwater in the aquifer that is supporting the ecosystem (see Best Practice #5).

The GIS Spatial Analysis of Maximum Rooting Depth and Groundwater Level presented in the Riparian GDE document does not present such contour depth-to-groundwater mapping or account for temporal variability.

Figures from Best Practices for using the NC Dataset, TNC

Furthermore, TNC guidance acknowledges that;

In many situations, the hydrologic connection of NC dataset polygons will not initially be clearly understood if site-specific groundwater monitoring data are not available. If sufficient data are not available in time for the 2020/2022 plan, The Nature Conservancy strongly advises that questionable polygons from the NC dataset be included in the GSP until data gaps are reconciled in the monitoring network. Erring on the side of caution will help minimize inadvertent impacts to GDEs as a result of groundwater use and management actions during SGMA implementation.

Many of California’s GDEs have adapted to dealing with intermittent periods of water stress, however if these groundwater conditions are prolonged, adverse impacts to GDEs can result.

Therefore, it is likely that the NC vegetation mapping is representative of conditions in which groundwater levels have been frequently and repeatedly pumped beyond the reach of riparian tree roots. Meanwhile, field observations over the past few wetter years show that the riparian vegetation has rebounded, illustrating how the ecosystem responds with the variation in water years. Receding groundwater levels and corresponding loss of surface flows in the current drought will likely reverse this recent trend, with the potential loss of the many young sycamores.

Determining Groundwater/Surface water interactions

TNC guidance for determining GDEs recognizes the importance of surface flows;

In addition, SGMA requires that significant and undesirable adverse impacts to beneficial users of surface water be avoided. Beneficial users of surface water include environmental users such as plants or animals, which therefore must be considered when developing minimum thresholds for depletions of interconnected surface water.

The Model Results and SMC Implications Presentation (March 25, 2021) reaches the conclusion that:

  • Basin water budget is dominated by streamflow percolation into the Basin and groundwater discharge to Ventura River
  • GW pumping averages only ~10% of the GW Budget As low as 4% in wet years 
Up to 31% in dry years
  • Basin GW levels will be lower in dry seasons, but Basin will still re-fill in normal to wet years

The conclusion that there is no impact from pumping based on the fact that the basin rapidly refills in the wet season points to the likelihood that the surface water is in fact “connected” to groundwater during these periods. Moreover, the fact that pumping represents up to 31% of the budget in the critical dry years raises many questions.

figure from Model Results and SMC Implications Presentation (March 25, 2021)

The Model Results identify four areas of concentrated pumping, three of which directly impact groundwater levels in the “Robles Reach.” This reach is the area with the most storage in the basin, and should be considered as the “primary sub-basin” for water supply. Pumping in this reach directly affects conditions throughout the basin.

The analyses and graphs presented in the Model Results do not provide information on the spacial and temporal surface flow conditions as they relate to groundwater levels. Because the downstream reaches are largely dependent on surface and groundwater flows out of this sub-basin, further analysis is needed to more clearly define the relationship between groundwater levels and surface flows. The analyses should, at a minimum, determine threshold groundwater levels at which surface flows are diminished or eliminated, both in the reach being monitored and downstream.

Groundwater/Surface water interactions
Conjunctive Use Study 1978 

This relationship was established decades ago in the Ventura River Conjunctive Use Report (1978) which states that;

Flows in the live stretch are affected by both the rate of recharge of the upper part of the Ventura River groundwater basin and by the rate of groundwater extraction from wells in the river.

Investigations published in the Conjunctive Use Report identified groundwater elevation thresholds in the upper basin at which flows in the live reach will cease;

when the water level in well 4N23Wl6C4 falls below Elevation 495, surface flow in much of the live stretch stops although some pools remain. A flow of 1 cfs or more in the live stretch corresponds with a water level in this well of greater than about Elevation 507.

Groundwater levels also affect surface flows in the Robles Reach, which frequently dries up despite constant inflows. Unfortunately, the Aquatic GDE Impact Analysis is quick to dismiss the effect of groundwater elevation on surface flows;

No monitoring is recommended at either of the critical riffle aquatic GDEs or the Robles Habitat Area, as impacts from pumping in these areas were determined to be minimal or non-existent.

This conclusion is inconsistent with the guidance provided in Monitoring Networks and Identification of Data Gaps BMP (DWR 2016) which states:

23 CCR §354.34(c))(6): Depletions of Interconnected Surface Water.

Monitor surface water and groundwater, where interconnected surface water conditions exist, to characterize the spatial and temporal exchanges between surface water and groundwater, and to calibrate and apply the tools and methods necessary to calculate depletions of surface water caused by groundwater extractions. The monitoring network shall be able to characterize the following:

(A) Flow conditions including surface water discharge, surface water head, and baseflow contribution.

(B) Identifying the approximate date and location where ephemeral or intermittent flowing streams and rivers cease to flow, if applicable.

(C) Temporal change in conditions due to variations in stream discharge and regional groundwater extraction.

(D) Other factors that may be necessary to identify adverse impacts on beneficial uses of the surface water.

DWR guidance provides detailed information on developing a monitoring network to accurately assess these concerns.

Establishing Minimum Flow Thresholds

As described above, the current GSP analysis incorrectly concludes that groundwater pumping has little to no effect on surface flows throughout the majority of the basin. But even for the identified groundwater dependent “Habitat Areas,” the development of minimum flow thresholds is inadequate. For example;

For the Foster Park Habitat Area, while the City’s low-flow thresholds are based on only one HSI score evaluated in the Padre study (average thalweg depth), we understand this currently provides the best available information to establish minimum thresholds for the depletion of interconnected surface water sustainability criteria.

This statement ignores best available science, including the recently published CDFW Draft Instream Flow Recommendations (2021) as well as the NMFS Draft Biological Opinion for Foster Park Wellfield (2005).

Implications for the UVR Groundwater Sustainability Plan

According to the Brownstein Water Group, the Cuyama Valley Basin and the Paso Robles Area Subbasin GSPs were recently deemed incomplete for deficiencies in their definitions of sustainable management criteria (SMC), including minimum thresholds and undesirable results. Some of the concerns cited by DWR are that the GSP;

  • provides insufficient detail for how it determined that the selected minimum thresholds . . . are consistent with avoiding undesirable results
  • does not relate different minimum thresholds for different portions of the basin to conditions that could cause undesirable results
  • does not sufficiently discuss expected impacts and therefore “precludes meaningful disclosure to, and participation by, interested parties and residents in the Basin.

It is clear from these recent DWR determinations that much more work is needed to develop and present a clear understanding of the workings of the Upper Ventura River Groundwater Basin, the potential impacts from groundwater pumping, and a plan to better manage the limited resource to ensure future sustainability and a healthy ecosystem.


These initial comments are provided as requested, in good faith, prior to the release of the Draft GSP in the interest of stakeholder engagement and with the hopes that the UVRGSA is able to augment the current analysis and develop a meaningful assessment of the impact of groundwater pumping on surface flows in the Ventura River. It is clear that this will be necessary to successfully develop the Groundwater Sustainability Plan to a level that satisfies the objectives of the Sustainable Groundwater Management Act (SGMA) in order to gain the support of local stakeholders and approval by the California Department of Water Resources.


Upper Ventura River Groundwater Sustainability Agency (UVRGSA) 

Mapping Indicators of GDEs, Groundwater Resource Hub, The Nature Conservancy

IDENTIFYING GDEs UNDER SGMA; Best Practices for using the NC Dataset, The Nature Conservancy, July 2019

Monitoring Networks and Identification of Data Gaps BMP , CA Dept of Water Resources,

DRAFT ENVIRONMENTAL IMPACT REPORT, VENTURA RIVER CONJUNCTIVE USE AGREEMENT,  Report on the Environmental Impacts of the Proposed Agreement Between Casitas Municipal Water District and the City of-San Buenaventura for Conjunctive Use of the VENTURA RIVER - CASITAS RESERVOIR SYSTEM, Prepared for CMWD and the City,  June 1978

GSAs Shooting 50% on GSPs—DWR Releases First GSP Assessment Results for High Priority Basins, Brownstein Water Group, June 4, 2021

More info:

Sustainable Groundwater Management Act (SGMA)California Department of Water Resources

Groundwater Resource Hub, The Nature Conservancy

Natural Communities Commonly Associated with Groundwater, California Department of Water Resources

Groundwater Dependent Ecosystems - How can we manage groundwater to benefit both people and nature? The Nature Conservancy,

On this blog:

Understanding CDFW Instream Flow Recommendations

Thursday, June 10, 2021

Watershed mural website

The "Enlivening The Matilija Watershed" Mural now has an interactive website that contains information on all the plants and animals featured in the artwork installed on the side of a Ojai Unified School District building in Ojai. 

The 30’x14’ mural depicts the Matilija Creek in it’s regenerated state after the Matilija Dam has been removed. The waters flow clear, the wildlife abundant, the flora and fauna vibrant and renewed. The beaver is featured prominently as it is a keystone species whose presence affects the entire whole of the ecosystem. The mural emphasizes the restored watershed which feeds a beaver pond where deer, bear, mountain lion, heron and others come to eat and drink. Oaks, sycamores and willow provide shade and a steady perch for the flyers to come and rest. The steelhead move unimpeded upstream to spawn where once they numbered into the thousands. This pristine and rejuvenated landscape will be framed by the cobbled remains of the Matilija Dam which once held back the waters and marred the mouth of the canyon. It’s removal signifying the steady return of the natural cycles of life.

Visit the website here:


Enlivening The Matilija Watershed" Mural

Santa Ana Bridge replacement groundbreaking

Aerial overview of the existing Santa Ana Bridge
 looking upstream on the Ventura River

A ceremonial groundbreaking event was held on Monday June 7 to kick off the Santa Ana Bridge Replacement Project.  Project sponsors Sam Jenniches (California Coastal Conservancy) and Mary Larson (Ca Dept of Fish and Wildlife) were present along with Supervisor Matt LeVere and representatives from the Ventura County Watershed Protection District and Transportation Department and their contractors.  This is the first major project component of the Matilija Dam Ecosystem Restoration Project.

Design work was sponsored by the California Coastal Conservancy and construction is funded through a $13.4M grant from Ca Dept of Fish and Wildlife.  The project will replace the existing 210-foot long Santa Ana Bridge with a 350-foot bridge to open up a constricted section of the river in Oak View.   Widening the channel by 80 feet will improve water and sediment flows, facilitate natural ecosystem processes through restoration of natural sediment transport and deposition, and reduce the need for channel maintenance in the vicinity of the bridge following large storm events. 

L to R: Chris Hooke, Ventura County Transportation Dept; Mary Larson, CDFW; County Supervisor Matt LeVere; Glenn Shephard, VCPWA-WP; Sam Jenniches, Coastal Conservancy; Paul Jenkin, Matilija Coalition  

more info:

Santa Ana Bridge replacement awarded $13.4M grant

in the news:

New Ventura River bridge could help endangered trout, agencies-move-step-closer-tearing-down-matilija-dam-near-ojai, VCStar, June 5, 2021

Start of Santa Ana Bridge replacement project brings Ventura County one step closer to removing Matilija Dam, KEYT, June 6, 2021 

Bridge means end is nearer for dam, Ojai Valley News, June 11, 2021

CI Harbor jetty and breakwater repairs

Over the past few weeks the US Army Corps of Engineers has been working on the jetties and offshore breakwater at Channel Islands Harbor.  Concerned beachgoers contacted Surfrider with concerns that the South Jetty was being extended and could impact the surf conditions at the popular Silver Strand Beach.  Although initially it was hard to find any detailed information on the project, the Corps and Port District ultimately provided drawings that illustrate the work being done.

South Jetty at Channel Islands Harbor, 2013

Over time coastal structures like these degrade as wave action displaces the large boulders and the structure "slumps" into the sea floor.  Periodic maintenance is performed by importing boulders which are placed on the existing structure to bring it back to its design profile.  The illustrations below show this:

More info:

Much Needed Repair Work Starts at Channel Islands Harbor Entrance,  Channel Islands Harbor website

SPL-2021-0512-NLH Channel Islands Harbor Breakwater, US Army Corps of Engineers Los Angeles District

Tuesday, April 27, 2021

Coastal Commission approves Surfers' Point Phase 2

At their April, 2021 meeting, the California Coastal Commission approved (with conditions) modifications to the Surfers Point Managed Shoreline Retreat project in Ventura, CA.   Application No. 4-05-148-A1 (City of Ventura and 31st Agricultural District, Ventura) aims to modify portions of the Managed Retreat project to support the recently completed plans for Phase 2 of the project.

The project was originally approved in 2006, but due to limited funding only about half of it was constructed in 2010-11. These amendments to the original permit No. 4-05-148  reflect a revised layout of the parking lots which will increase the total available spaces for day use, overflow, and temporary surf check parking. (See the prior analysis of parking on this blog here)

"The proposed reconfiguration would result in the addition of approximately 151 total parking spaces, approximately 64 of which would be located in the high frequency parking lot, and approximately 87 in the reduced frequency parking lot. [...] The proposed project reconfiguration would also add approximately three (3) twenty minute parking spaces that allow for drop-off or for the public to check water or surf conditions (these spots are called “surf check” parking spaces), for a total number of approximately 27 “surf check” parking spaces. Shoreline Drive is proposed to be relocated to improve circulation, with its terminus at the parking lot to be further east. The previously approved gatehouse/ticket booth located at the entrance of the parking lot would be relocated approximately 160 feet to the east, and a vehicle turn around would be added. 

"The surface material of the parking lot is also proposed to be changed from a permeable surface to asphalt. This change in surface material would also apply to the portion of the parking lot that was constructed in Phase 1 along with the new portions of parking lot to be constructed in Phase 2. [...] It was determined that the original turf grass parking lot is not feasible in current drought conditions and other permeable surfaces are infeasible as water is unable to adequately infiltrate due to the high ground water table.


Modifications to Parking Layout
Surfers Point phase 2

A separate permit (A-4-SBV-06-037) covers the "tidelands" portion of the project.   Phase 2 includes modifications to the originally approved managed retreat project to extend the cobble berm and vegetated sand dunes to merge with the promenade and recently constructed emergency revetment.  The changes would extend the cobble berm and vegetated sand dunes approximately 150 ft east (14,800 cu.yds. of cobble and 17,825 cu.yds. of sand), reconfigure public access amenities, and revise landscaping plan, at Surfer’s Point, City of Ventura, Ventura County. 

Modifications to Cobble Berm and Dunes
Surfers Point phase 2

The permit will require electric vehicle charging stations to be installed in the new parking lots:

The special condition to require electric vehicle charging stations is consistent with Coastal Act Section 30253 because it will reduce energy use and provide an opportunity for users of electric vehicles to access the coast. 

During discussion of the project, Coastal Commissioners Shelley Luce, Matt O'Malley, Mike Wilson, Mark Gold and Donne Brownsey raised concerns about the change of surface material of the parking lot, citing concerns over potential water quality impacts from runoff and uncertainty around mitigation of those impacts. Based on these concerns, Coastal Commission staff added a required Storm Water Management Plan (SWMP) and water quality monitoring condition into the permit amendment. The permit was approved unanimously.


The Coastal Commission staff report includes an interesting summary of the history of the project dating back to the first bike path, located approximately two to 20 feet seaward of its current location, that had been partially destroyed by storms in the winter of 1982/3.  (Hints of this original bike path are visible along the eroding bluff today)

In 1984, the Commission certified the City of San Buenaventura’s Local Coastal Program (LCP) which created a 250-foot wide oceanfront corridor for recreational use, extending west from Surfer’s Point Park to the Ventura River.  The LCP was amended in 1986 such that "temporary bicycle and hiking trails...and temporary parking which do not require construction of a shoreline protective device, may be permitted within the setback area established by the geotechnical study.” 

In 1988 and 1989, the Commission approved two permits for improvements within the Commission’s original jurisdiction, CDP Nos. 4-88-123 and 4-88-130, that were associated with construction of Shoreline Drive, the 352-space parking lot, and other development in the oceanfront corridor at Surfer’s Point.

The oceanfront corridor improvements were constructed in 1989. In the summer of 1991, shoreline erosion began undermining portions of the bicycle path. 

In November 1991, Commission staff received a request from the City of Ventura/31st Agricultural District for an emergency permit to place five to six ton rocks along an approximately 260 foot length of the backshore in order to protect the bicycle path from erosion (CDP No. 4-91-060-G). The emergency request was denied in favor of relocating the undermined section of the bicycle path slightly inland. In explaining the Executive Director’s denial of CDP No. 4- 91-060-G, Commission staff noted that the improvements in the oceanfront corridor had been constructed on the understanding that they were temporary in nature and therefore could not be protected with shoreline protective devices. 

On December 11, 1992, following continued undermining of the bicycle path and parking lot, the City of Ventura issued itself an emergency coastal development permit for construction of a rip-rap revetment, and the revetment was constructed the following week, from December 14 – 16, 1992. Commission enforcement staff issued a stop work order on December 15, 1992, and further pursued removal of the revetment through enforcement and legal measures.

This emergency revetment remained in place until 2010 when it was removed along with the collapsing parking lot during construction of Phase 1 of the Managed Retreat project.


Although the Surfers Point Managed Shoreline Retreat Project has been widely recognized as an innovative and effective approach to coastal management, it is just as much an example of failed coastal management.  Conflicting mandates and the inability to coordinate amongst the multitude of federal, state, and local government agencies has directly impacted this important public trust resource.  It is hard to quantify the benefits lost to decades of crumbling infrastructure and mismanagement at what should be the "crown jewel" of the City of Ventura.  This mismanagement stems from a lack of understanding and respect for the underlying dynamic landform of the Ventura River delta, combined with the bureaucratic failings of fragmented governance.   The fact that this issue has already lingered for four decades is stark foreshadowing to the future impact of sea level rise on the California coast.  In the meantime, we can only watch as the ocean slowly erases the mistakes of the past...


Coastal Commission Staff Report: Application No. 4-05-148-A1 (City of Ventura and 31st Agricultural District, Ventura)

On this Blog

Surfers Point (all posts)

Surfers’ Point Managed Retreat Phase 2 update, Oct 2020 - final plans and costs

Surfers' Point Phase 2 update, Dec 2019 - parking analysis

The Managed Retreat Process at Surfers Point, Nov 2010 - Phase 1 construction

Surfers' Point erosion damage Jan 2021 - current conditions

Natural Shoreline Case Study

Surfers' Point case study (another case study)

US Climate Resilience Toolkit

Friday, April 16, 2021

Comments on CDFW Instream Flow Recommendations

 Via E-mail to

RE: Comments on CDFW Draft Instream Flow Regime Recommendations for the Lower Ventura River (February 2021)

Dear Mr. Pert,

Thank you for the opportunity to provide comments on the Draft Instream Flow Regime Recommendations. This document has been long anticipated amongst stakeholders engaged in ongoing discussions in the watershed. During this time of unprecedented stress from increased population and climate change, guidance is clearly needed to secure instream flows to maintain riverine ecosystems in California. These diverse and delicate ecosystems support not only native fisheries, most of which are now threatened, but also provide for a quality of life and the very foundation of our economy. The endangered southern steelhead serves as an indicator for how well we manage our land and water, and these instream flow recommendations will help inform ongoing management of our watershed.

Flow Recommendations are difficult to understand

The CDFW Instream Flow Recommendations are the result of a combination of different analytical approaches developed over several years and published in multiple documents. This is necessary in developing a standard approach that applies to the entire State of California, but the result can be difficult to unravel. The outcome and implementation of these recommendations depend on a clear understanding of the approach and intent, not only within the scientific and regulatory communities, but most importantly amongst the diverse stakeholders that currently manage and benefit from the resource.

In the course of our review, two graphics were developed to more clearly illustrate the relationships between the various criteria, methodologies, and recommendations. These graphics and a description of the processes are attached with these comments and published online at

The Draft Ventura River Flow Recommendations were derived from Steelhead Passage Flows, Sensitive Period Indicators, and Steelhead Optimum Flows. (The other criteria were developed to provide context based on historical flows in the Ventura River Watershed.)

Therefore, the CDFW Instream Flow Recommendations are primarily based upon the physical properties of the river as determined by Field Methods. The exceptions are two cases where Steelhead Optimum Flows are applied, for Fall Pulse Flows in November (40cfs) and for Adult Migration (80cfs) in Reach 3 only. The latter two recommendations are arbitrary and inconsistent with the other field-based recommendations.

CDFW diverges from established watershed nomenclature

For these studies, CDFW redefined the river and reaches differently from established nomenclature in other watershed planning efforts. For example, much of Reach 3 and all of Reach 4 of CDFW’s “Lower Ventura River” falls within the “Upper Ventura River Groundwater Basin” as defined by the State Groundwater Management Act (SGMA). This nomenclature is likely to create confusion in discussions on implementation of the CDFW Instream Flows Recommendations.

Application of Instream Flow Recommendations is unclear

Stakeholders are confused as to the expectations of the Instream Flow Recommendations in the context of SGMA and other ongoing watershed concerns.

The Department understands these flows to be protective of steelhead and the habitat that supports them and recommends applying them across all water year types. In some cases, the recommended flows may not be available due to precipitation variability. When flows naturally fall below the flow recommendations for the lower Ventura River reaches 2,3, and 4, full natural flows should be maintained. Also, flows higher than the recommended criteria may be beneficial to the ecosystem and to steelhead.

It is unclear how to interpret this statement. Given that the existing condition falls short of the recommended flow in many water years, what is the meaning of “full natural flows should be maintained?” Does this refer to the Natural Flow developed in the Criteria Report (but not published in the Flow Recommendations?) (See comments below on Natural Flow)

Reaches 2/3/4 use different criteria for recommended flows

For the dry months, the differing flow recommendations in these reaches is an artifact of the field study protocols which produce slightly different results based on the varied streambed geometry. Indeed, the consistency of these results is a positive indicator of scientific rigor. A margin of error of 1cfs (6%) would be expected in the natural system, and this is also within the margin of error for the existing gage network (see comment below.)

Flow recommendations for the months of December-May are derived from the steelhead passage criteria (40/33 cfs) in reaches 2 and 3 respectively, while adult migration flows are applied only in reach 4 (80 cfs.) Apart from extractions at Foster park and inflows from Coyote Creek, these 3 reaches exist within the continuum of flows in the river, so 80 cfs in reach 4 would naturally translate to approximately the same flow in the reaches downstream.

Recognizing that these reaches are similar and connected, it may make more sense to apply a common denominator within these reaches to the entire reach as a whole. For example, the Sensitive Period indicator analysis for reaches 2, 3, and 4 resulted in 16, 14, and 15 cfs respectively. It is reasonable to conclude that a threshold of 14 or 15 cfs would indicate sensitivity for the reach as a whole.

The Natural Flows Database is flawed

The “Natural Flows” published in the Watershed Criteria Report are based on the Natural Flows Database for California computer model that attempts to predict unimpaired instream flows for the entire State of California. This model may be applicable to watersheds where snowpack and large reservoirs dominate, but appears to fall short in the groundwater dependent ecosystems of Southern California.

The CDFW Overview document states:

Natural Flows represent flows that would be present in the absence of water use or land use impacts to natural hydrology (Zimmerman et al. 2018). Natural Flows are determined using the estimated Natural Flows Database for California (Zimmerman et al. 2020). These data are used to calculate water month type, Ecosystem Baseflows, and Salmonid Habitat Optimum Flows.

The published literature regarding this computer model (Zimmerman 2017) include the disclaimer;

For some models, poor precision limited the sensitivity of our assessment, making
it impossible to determine whether deviation in flows from expected values was an artefact of the model or evidence of human-caused flow modification. This was 
particularly true for minimum and mean models in the dry season, when natural streamflows are low or absent and are controlled by physical processes that are not represented by basin- scale attributes.
For example, the data suggest that in the 
South Coast of Californiaunderstanding and mitigating the effects of inflated discharge in the summer may be critical

Here the authors admit a lack of understanding as to why the computer model predicts less instream flow than the “inflated discharge” evidenced by the stream gage records. In acknowledgement of this flaw, an “Appendix A” was added to the Watershed Criteria Report to provide an alternative Natural Flow estimation;

Natural Flows Database estimates are provided for every Watershed Criteria Report as part of the effort to produce a consistent statewide dataset. Where appropriate (relatively unimpaired) gage records are available, these site-specific data will be included as an appendix to the report. In these cases, the gage data are considered to replace the Natural Flows Database as an estimate of natural flow conditions.

Indeed, Ventura River flows for the dry months are grossly underestimated by the Natural Flows Database. One explanation may be the inability of the model to account for groundwater-surface water interactions, which are fundamental to the Ventura River. The flows published in Appendix A, derived from a statistical analysis of the “synthetic gage” data for the Ventura River, are significantly higher than those predicted by the Natural Flow database.

For this reason, the Draft Instream Flow Recommendation abandoned the Natural Flows Database, instead using the available historic gage data. Yet neither this document or the Watershed Criteria Report clearly explain the limitations of the Natural Flows information.

The Watershed Criteria Report as published states;

Natural Flows are the streamflows (in cfs) that would be expected with no human influence

Unfortunately, the perpetuation of “Natural Flows” in the CDFW publications is already tainting the public discourse. A recent OpEd published in the Ojai Valley News says:

“The new flow recommendation by the California Department of Fish & Wildlife is 15 cubic feet per second at Foster Park for summertime flows. This is dramatically different from the 1 cfs that the Department of Fish and Wildlife calculates for the same area from July to October of dry years as the “natural flows expected with no human influence” (Watershed Criteria Report No. 2020-01).”

Synthetic gage misrepresents Natural Flow

In place of the Natural Flows Database, these analyses use the synthetic least-impaired USGS gage Ventura R NR Ventura + Div 11118501 based on the period of record 1965– 2007

USGS gage Ventura R NR Ventura + Div , takes the historic USGS flow data and adds back the amount of water diverted through the surface diversion at the City of Ventura’s Foster Park wellfield. (Note that the surface diversion is a fraction of what the total wellfield extracts, and is currently out of commission.)

This “synthetic gage” data is used to develop many of the Watershed Criteria. The historic flow record from the past 40 years is useful in describing the general qualitative flow characteristics in the watershed such as Flow Variation, and to a lesser degree Functional Flows. However, the use of the synthetic gage as currently defined is extremely problematic when attempting to establish a baseline for unimpaired, or “Natural Flows.”

There are three primary concerns with the use of the historic USGS gage data;

First, this data is a record of surface flows just downstream from Foster Park from 1965-2007, which fundamentally represents the developed watershed. Most of the major modifications in the Ventura River Watershed occurred prior to 1965, including the construction of MatiIija Dam in 1948 and Casitas Dam in 1958. It is also important to note that by 1890, before stream gages existed, 4,000 acres of agriculture had already been developed in the Ojai Valley.

Second, a synthetic gage that solely accounts for a single surface diversion disregards the multitude of wells throughout the watershed upstream, all of which detract from the total discharge at Foster Park. The importance of the interaction between groundwater and surface water is recognized by the State of California in the Sustainable Groundwater Management Act. Studies and governance are underway to better define these effects within the Ventura River Watershed. Coordination with the State Water Board’s surface water/groundwater model analysis of unimpaired flows would have been helpful in providing a more robust baseline for instream flows.

Third, stream gaging was historically focused on recording flood events rather than maintaining low flow accuracy. Each flood causes geomorphic alterations to the streambed profile which necessitates re-staging, or re-calibrating, the gages for accuracy. However, until recently very little attention was given to low flows, which are notoriously difficult to measure accurately (i.e. the margin of error may meet or exceed the measured flow.) Other uncontrolled variables such as vegetation growth or human activity can significantly affect gage accuracy. Unfortunately, these variables are not quantifiable in hindsight, so the low flow record has a very high margin of error.

It is important to recognize that the “synthetic gage” does serve as a baseline for the current condition based upon the hydrology of the past 40 years. This 20th century baseline will become most relevant in the coming decades with the increasing pressures of population growth and climate change, as well as to monitor progress with enhanced watershed management.

However, by no means does the synthetic gage represent “the flow that would be present in the absence of land use and water diversion impacts to natural hydrology.” Indeed, it is not only misleading to call these “Natural Flows,” this also undermines any discussion of maintaining or enhancing base flows in the river.

Most importantly, the “Natural Flows” assessment perpetuates the Shifting baseline syndrome“an incremental lowering of standards that results with each new generation lacking knowledge/ observation of the historical (or previous) condition of the environment being observed.”


  • Consolidate flow recommendations for the similar and contiguous reaches 2, 3, and 4.
  • Revise the flow recommendations based on Steelhead Optimum Flows to maintain consistency with flow recommendations based on field methods.
  • Eliminate the flawed Natural Flows Database results from the Criteria Report and revise Natural Flows to reflect the stream gage analysis used in the Flow Recommendations report.
  • Replace the term “Natural Flows” with “Historic Flows” to better represent conditions in the watershed.
  • Update the Natural Flow Criteria as more information comes available from the State Water Board analysis of groundwater-surface water interactions and estimates of unimpaired flow.

We appreciate the opportunity to comment on the Draft Instream Flow Regime Recommendations for the Lower Ventura River and hope these comments are helpful in finalizing these documents.


A.Paul Jenkin
Coordinator, Matilija Coalition
Surfrider Foundation - Ventura County Chapter

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Understanding CDFW Instream Flow Recommendations

Ecosystem flows

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   Ojai leaders don't go with the flow, Ojai Valley News, 5 March 2021 

“These humongous flows by Fish and Wildlife would totally disrupt life in the Ojai Valley,” said Rapp, adding he was particularly alarmed by the agency’s statement that full, natural flows should be maintained when flows fall below the recommendations. “That’s a huge impact. That means for many months of the year, no one should pump their wells, or if someone has diversion rights they should not divert water from the river.”

The decision on what type of instream flow regime is necessary to support a healthy Ventura River is essentially a scientific one, and will not, and should not, be decided by authors of letters to the editor or guest columnists. However, the political will to support and implement whatever scientifically defensible instream flow regime is identified, is very much a matter of public awareness and understanding. Ultimately, the question raised by the current controversy over dividing the waters of the Ventura River is, “What kind of a community do we want to be?” The residents of the Ojai and Ventura River Valleys have an opportunity to set an example for other communities in California and beyond. 

The new flow recommendation by the California Department of Fish & Wildlife is 15 cubic feet per second at Foster Park for summertime flows. This is dramatically different from the 1 cfs that the Department of Fish and Wildlife calculates for the same area from July to October of dry years as the “natural flows expected with no human influence” (Watershed Criteria Report No. 2020-01). 

Three of the largest water users in the Ventura River Watershed — the city of Ventura, Ventura River Water District and Meiners Oaks Water District — have all sent response letters to CDFW regarding the recommendations. All three letters state there’s not enough water in the river to meet Fish and Wildlife’s recommendations.

“The flows that they’ve recommended for steelhead are not available in the river most of the time, so they set these recommended flows that we cannot achieve,” said James Kentosh, vice president of Meiners Oaks Water District.

CDFW’s recommended flows significantly exceed natural, historic flows during all but four months of even the wettest of years, Kentosh told the Ojai Valley News. “If every human being stopped using water in the valley, those flow recommendations would still only be enough a fraction of the time,” he said.  Furthermore, the amounts of water necessary to supplement natural flows to reach recommended flows are too large, according to Bruce Kuebler, board president of VRWD.

Thursday, April 15, 2021

Understanding CDFW Instream Flow Recommendations

The California Department of Fish and Wildlife (CDFW) released Draft instream flow recommendations for the lower Ventura River and Coyote Creek in February 2021.   According to CDFW, "This information will be used to enhance flows in the watershed in several ways, including the development of flow criteria and identification of important flow thresholds for conservation, restoration, and protection of southern steelhead in the Ventura River watershed."

The Draft Flow Recommendations are summarized in the table from the draft document below:

Understanding CDFW Instream Flow Recommendations 

The CDFW Instream Flow Recommendations are the result of a combination of different analytical approaches developed over several years and published in multiple documents.  This is necessary in developing a standard approach that applies to the entire State of California, but the result can be difficult to unravel.  The outcome and implementation of these recommendations depend on a clear understanding of the approach and intent, not only within the scientific and regulatory communities, but also amongst the diverse stakeholders that currently manage and benefit from the resource.  

In order to better understand the origin of these flow recommendations, two graphics were developed to more clearly illustrate the relationships between the various criteria, methodologies, and recommendations.  These graphics and a description of the processes are shown below.

The Summary Chart consolidates all of the values published in the Draft instream flow recommendations document, each aligned by month so that they can be easily viewed and cross referenced.  At the top of this chart is the general Functional Flow diagram from the Watershed Criteria Report with the Ventura River specific values inserted for each functional flow component.  The other watershed criteria are shown in the boxes below, color coded for consistency with the CDFW documentation.  

But where did this information come from?  

The Summary of Watershed Criteria Methodology table illustrates how each of the watershed criteria were derived.  
  • Stream gage records are used to develop a statistical analysis of flows in the Ventura River which become the basis for understanding Flow Variation and Functional Flow.  
  • A computer model was used to develop the Natural Flows criteria, from which Ecosystem Baseflow and Salmonid Habitat Optimum Flows were derived.   
  • Field methods were applied to  determine Sensitive Period Indicators and Steelhead Passage Flows.

Note that due to obvious inaccuracies in the statewide "Natural Flows Database" computer model, the analysis for the Ventura River use the "synthetic least-impaired USGS gage Ventura R NR Ventura + Div 11118501 based on the period of record 1965–2007."  This data is included in Appendix A of the Watershed Criteria Report No. 2020-01 Version 2, updated May 2020.

As illustrated in the Summary Chart above, the Ventura River Flow Recommendations were derived from Steelhead Passage Flows, Sensitive Period Indicators, and Steelhead Optimum Flows.   (The other criteria were developed to provide context based on historical flows in the Ventura River Watershed.) 

Therefore, the CDFW Instream Flow Recommendations are primarily based upon the physical properties of the river as determined by Field Methods.  The exceptions are two cases where Steelhead Optimum Flows are applied, for Fall Pulse Flows in November (40cfs) and for Adult Migration (80cfs) in Reach 3 only.

Field Methods Overview

CDFW Staff surveyed a total of 22 riffle transects on San Antonio Creek and the lower Ventura River. Fifteen of the original riffle transects surveyed for this project were included in the final analysis. These transects were used to develop both Sensitive Period Indicators and Steelhead Passage Flows. 

The Wetted Perimeter Method is a field survey used to determine the Sensitive Period Indicator, which is "threshold flows below which the ecosystem is likely to be particularly sensitive to additional flow reductions and other stressors." 

Once wetted perimeters and associated flows for the streambed cross-sections are obtained for the range of important flows, a wetted perimeter discharge curve is developed by plotting wetted perimeter against discharge. The breakpoint and incipient asymptote, as thresholds of important habitat conditions, are then identified to determine instream flow needs necessary for maintaining ecological and riffle productivity flows.  The Sensitive Period Indicator flow must produce a wetted perimeter that covers at least 50% of the bankfull channel perimeter in streams up to 50 feet wide and 60–70% in wider streams.

An example of this method is shown below (taken from AppendixB) for a transect of the Ventura River.  In this location it was determined that 16 cfs is the breakpoint below which the river is sensitive to flow reduction and other stressors.

The Habitat Retention Method is used to determine Salmonid Passage Flows. This method seeks to identify flows required to permit salmonid passage across the shallowest part of a channel, the hydraulic control.  Passage Flows for juvenile steelhead must produce a mean depth of 0.4 feet at the hydraulic control, while also meeting additional criteria for wetted perimeter or flow to preserve connectivity between mesohabitat units.


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