Monterey Peninsula Water Management
District
Technical Memorandum 2006-02
Existing Water Needs of Cal-Am Customers
within MPWMD Boundaries and
Non
Adjusted for Weather Conditions During Water
Years 1996 through 2006
Introduction
This
technical memorandum updates the information that was provided at the Monterey
Peninsula Water Management District (District or MPWMD) Board workshop on March
23, 2006, regarding existing water needs of customers in the California
American Water (Cal-Am) main distribution system[1]
in the
(1)
existing
water needs of customers in Cal-Am’s smaller systems in the Highway 68 corridor
– Ryan Ranch, Hidden Hills, and Bishop Units – that derive their source of
supply from the Laguna Seca Subarea (also known as the Southern Inland Subarea)
of the
(2)
existing
water needs of customers in Cal-Am’s main system in the event that the water
rights recognized by the State Water Resources Control Board (SWRCB) in Order
No. WR 95-10 and held by Cal-Am are reduced to reflect reduced storage capacity
in Los Padres Reservoir due to sedimentation, and
(3)
existing
water needs of non Cal-Am producers that derive their source of supply from the
Coastal Subareas and Laguna Seca Subarea of the
The
purpose of the technical memorandum is to provide reasonable and defensible
estimates of the amount of water currently needed by all customers served by
Cal-Am within District boundaries[2]
and non Cal-Am producers within the Seaside Groundwater Basin. In this context, the memorandum provides an
estimate of the amount of water that Cal-Am must develop to replace supplies
that are either unlawful, exceed Cal-Am’s adjudicated rights, or may be reduced
by further regulatory action and that are needed to meet existing water demand
within the District. These estimates of
existing water demands will be compared to Cal-Am’s recognized rights in the
Carmel River Basin and Cal-Am and non Cal-Am adjudicated rights in the Seaside
Groundwater Basin to determine the amount of “replacement” supplies needed to
meet existing demand.
The
technical memorandum is divided into four sections. In the first section, a technique to adjust
monthly water production values for wet and dry weather conditions is described
and applied to Cal-Am’s monthly production from Carmel River sources and
Seaside Coastal Subarea sources during the selected period of analysis. In the second section, these weather-adjusted
existing demand estimates are compared to Cal-Am’s recognized rights to divert
Carmel River water and Cal-Am’s adjudicated rights to pump groundwater from the
Coastal Subareas and Laguna Seca Subarea of the Seaside Groundwater Basin to
quantify the water supplies that Cal-Am must develop to replace existing
supplies that are being unlawfully diverted from the Carmel River or that
exceed Cal-Am’s adjudicated rights in the Seaside Groundwater Basin, as
specified in the recent adjudication. In
the second section, the loss of storage capacity in Cal-Am’s Los Padres
Reservoir and its possible effect on Cal-Am’s recognized rights and Cal-Am’s
need to develop additional replacement supplies is also discussed. In the third section, weather-adjusted
existing demand estimates are developed for non Cal-Am producers in the Coastal
Subareas and Laguna Seca Subarea of the Seaside Groundwater Basin and compared
to the non Cal-Am adjudicated rights in these subareas to quantify additional
replacement supplies needed to comply with the natural safe yield for the basin
specified in the adjudication. In the
fourth section, the replacement requirements are summarized and “yield targets”
are recommended that should be used to size water supply alternatives being
developed to meet existing water demand in the Monterey Peninsula area.
This
technical memorandum should be read in conjunction with the staff note that was
prepared for the March 23, 2006 workshop.
This staff note includes useful background information on the regulatory
and judicial constraints on water use within the District and is included as
Appendix A.
Unadjusted Cal-Am Water Demand: At the March 23, 2006 Board workshop, a
summary table was presented that compared Cal-Am’s annual production from its
Carmel River sources for the ten-year period from WY 1996 through WY 2005[3]
with the annual production limits set by the SWRCB in Order 95-10 for each of these
water years. The table also indicated
water year type (e.g., “wet”, “normal”, and “below normal”) for each year and
showed the amount of water that Cal-Am produced in excess of its recognized
water rights. This table, updated to include
production data for WY 2006, is included as Table 1 and shows that, on average,
Cal-Am produced 7,639 acre-feet per year (AFY) of water from its
Adjusted Cal-Am Water Demand:
To account for the “wet” weather condition during the period of
analysis, Cal-Am’s actual production was adjusted using a monthly procedure
developed for the District’s operation model, known as the Carmel Valley
Simulation Model (CVSIM). With this
procedure, monthly unimpaired streamflow at the San Clemente Dam site is used
as a proxy value for weather conditions.
Based on predetermined exceedence frequency values, the monthly
unimpaired flow is classified as wet, normal, dry, or critically-dry[4]. Based on the assumption that the streamflow
values accurately reflect weather conditions that influence water demand (e.g.,
air temperature and rainfall) actual water production is decreased during wet
months, unchanged during normal months, and increased during dry and critically
dry months. The change in actual monthly
production for weather conditions varies by month and was determined by
reviewing historical production records under varying weather conditions.
Table 2 summarizes the monthly adjustments that were made to the
Cal-Am’s production from its sources in the
Columns
8, 9 and 10 show the first adjustment made to the monthly MPWRS production
values. In this first adjustment, all of the values are normalized or adjusted
to the normal range. In this first step,
normal monthly values (e.g., 369 AF in October 1995) are unchanged; wet values
(e.g., 29,961 AF in February 1996) are increased; and dry or critically-dry
values (e.g., 680 AF in December 1999) are decreased. Columns 11, 12 and 13 and columns 14, 15 and
16 show the second adjustment made to the monthly MPWRS production values. In this second step, all of the normalized
monthly MPWRS values are increased as
if all of the months during the period of analysis had been dry (columns
11, 12, and 13) or critically-dry (columns 14, 15, and 16), respectively.
Table 3 summarizes the unadjusted annual production values and the
adjusted normal, dry, and critically-dry year production values by Cal-Am from
the MPWRS for customers in Cal-Am’s main system for the period of
analysis. As shown, Cal-Am’s average
annual unadjusted production from the MPWRS was 14,710 AFY. Cal-Am’s average annual adjusted production
from the MPWRS, assuming each month during the period of analysis had been
normal, would have been 15,095 AFY or approximately 2.5% greater than
reported. Table 3 also shows that Cal-Am’s
average annual adjusted production from the MPWRS, assuming each month during
the period of analysis had been dry, would have been 15,474 AFY or
approximately 5.2% greater than reported.
Similarly, Table 3 shows
that Cal-Am’s average annual adjusted production from the MPWRS, assuming each
month during the period of analysis had been critically-dry, would have been
15,858 AFY or approximately 7.8% greater than reported. While it is unlikely that every month during
the 132-month period of analysis would have been critically-dry, the
critically-dry year values provide a worst-case basis for assessing the effect
of weather on water production during the period of analysis.
If
the adjustment factor for critically-dry years (7.8%) is applied to Cal-Am’s
average annual unadjusted production from Carmel River sources during the
period of analysis (11,015 AFY, see Table
1) and also applied to Cal-Am’s average annual unadjusted production
from sources in the coastal area of the Seaside Groundwater Basin during the
period of analysis (3,695 AFY, see Table 4),
then the weather-adjusted average annual production by Cal-Am from Carmel River
and Seaside Coastal sources during the period of analysis assuming constant
critically-dry conditions would be
11,874 AFY and 3,983 AFY, respectively.
Notably, there are other factors that have affected the amount of water
demanded by customers in Cal-Am’s main system and produced by Cal-Am from its
sources in the Carmel River and Seaside Groundwater Basin during the period of
analysis. These factors include the threat of action by the SWRCB and
significant fines if Cal-Am exceeds the production limit set by Order 95-10,
increased water rates, extensive public outreach regarding the need to conserve
water, resource management by the District, appreciable unaccounted-for-water
losses in Cal-Am’s main distribution system, and new technologies. Notwithstanding, it is believed that the
weather-adjusted production estimates are reasonable and defensible as
conservative values and should be used for water supply planning rather than
the unadjusted production values that do not account for the wetter-than-normal
period of analysis. Thus, in the
following sections the term “weather-adjusted” means that the critically-dry
year factor (i.e., 7.8% increase in normal year demand) has been applied to the
reported production during the period of analysis.
Section 2: Cal-Am Replacement Requirements within MPWMD
Boundaries
Carmel River Replacement Requirement:
Based on the weather-adjusted average annual production estimate by Cal-Am
from Carmel River sources for the period of analysis (11,874 AFY) and Cal-Am’s
recognized rights to divert Carmel River waters (3,376 AFY), Cal-Am needs to
develop 8,498 AFY of replacement supplies to legalize its recent
diversions from Carmel River sources for customers in its main distribution
system.
Laguna Seca Subarea Replacement Requirement:
In addition to Cal-Am’s replacement requirement in the Coastal Subareas
of the Seaside Basin under the adjudication decision, Cal-Am also needs to
develop replacement supplies for its three smaller systems in the Laguna Seca
Subarea of the Seaside Basin (i.e., Ryan Ranch, Hidden Hills, and Bishop
Units). Table 5 shows annual
production from Cal-Am’s smaller systems in the Laguna Seca Subarea of the
Seaside Groundwater Basin for the period of analysis. Table 5
also shows Cal-Am’s “eventual” allocation from the Laguna Seca Subarea of the
Los Padres Reservoir Replacement
Requirement: Cal-Am’s replacement requirement for the
Carmel River (8,498 AFY) is based on Cal-Am’s water rights that were recognized
by the SWRCB in Order 95-10 (3,376 AFY).
These recognized rights included:
(1) right to divert to storage 2,179 AFY of
water at Los Padres Reservoir, based on a post-1914 appropriative right
(License 11866),
(2) right to divert 1,137 AF directly from the
Carmel River, based on a pre-1914 appropriative right, and
(3) right to divert 60 AFY from the
If these recognized rights are reduced,
then Cal-Am’s replacement requirement for Carmel River sources will increase correspondingly.
In this regard, the continuing
sedimentation and loss of storage capacity in Los Padres Reservoir can affect
the amount of replacement water that Cal-Am is required to develop to cease its
unlawful diversions from the Carmel River.
In Order 95-10, the SWRCB reduced the quantity of water that Cal-Am
could divert to storage in Los Padres Reservoir under Cal-Am’s licensed right
from 3,030 AFY to 2,179 AFY. This
reduction was based on the amount of reservoir storage capacity that Cal-Am had
estimated was available in Los Padres Reservoir in 1984 and had provided to the
SWRCB as part of the water right hearings in 1992 and 1994.
It should be noted that, although used by
the SWRCB in Order 95-10, the 1984 estimate by Cal-Am is inconsistent with previous
and subsequent storage estimates and likely in error. A more accurate estimate was made by the
United States Geological Survey (USGS, 1981[7])
for the District, following the Marble Cone Fire in 1977. The USGS estimated that the total storage
capacity in Los Padres Reservoir was 1,950 AF at elevation 1,040 feet in
1978. Based on this 1978 USGS estimate,
and Cal-Am’s most recent estimate of storage capacity in Los Padres Reservoir
of 1,569 AF at elevation 1,040 feet in 1998, the average annual loss in storage
capacity in Los Padres Reservoir is approximately 19 AFY (381 AF ) 20 years = 19 AFY). Assuming that this rate is correct and that
average sedimentation conditions have continued over the last eight years, the
storage capacity in Los Padres Reservoir is now estimated to be 1,417 AF (1,569
AF – 152 AF = 1,417 AF).
Therefore, if the SWRCB revisited Order
95-10 and applied the same logic regarding current recognized storage rights,
i.e., the legal right to divert water to storage is limited by the physical
capacity to store water, then Cal-Am’s recognized rights for diversion from the
Carmel River could be reduced from 3,376 AFY to 2,766 AFY, based on Cal-Am’s
1998 estimate of storage capacity in Los Padres Reservoir, or 2,614 AFY, based
on estimated storage capacity in 2006.
In the first case, Cal-Am would need to develop an additional 610 AFY of
replacement water. In the second case,
Cal-Am would need to develop an additional 762 AFY of replacement water. Eventually, unless Cal-Am implements some
type of dredging program at Los Padres Reservoir to maintain or recover storage
capacity, Cal-Am will need to develop an additional 2,179 AFY of replacement
water to comply with Order 95-10 and meet its customers needs. For purposes of this memorandum, it is
recommended that a replacement requirement for lost storage capacity in Los
Padres Reservoir of 762 AFY should be used, based on estimated current storage
capacity in Los Padres Reservoir. If
Cal-Am indicates that they do not plan to implement either a maintenance or
recovery dredging program at Los Padres Reservoir, then this requirement will
need to be revised.
Section 3: Non Cal-Am Replacement
Requirements in the Seaside Groundwater Basin
Seaside Coastal Subareas Replacement Requirement: Table 6 shows non Cal-Am annual
standard production from sources in the Coastal Subareas of the
Laguna Seca Subarea Replacement Requirement:
Table 7 shows annual production by the
“Alternative” producers in the Laguna Seca Subarea of the
This
technical memorandum provides reasonable and defensible estimates of the amount
of water that is produced by Cal-Am to meet existing customer demand in
Cal-Am’s water distribution systems within District boundaries. The production estimates have been adjusted
to account for the wetter-than-normal conditions that occurred during the
11-year period of analysis, i.e., Water Years 1996 through 2006. Specifically, based on results from a monthly
analysis, the reported annual production values were increased 7.8% to reflect
critically-dry conditions during the period of analysis. The decision to use
critically-dry conditions was made to provide a worst-case basis for assessing
the effect of weather on reported production during the period of analysis and
is considered appropriate for conservative water supply planning purposes. Based on the adjustments made, Cal-Am’s
reported average annual production for customers in its main system during the
period of analysis increased from 14,710 AFY to 15,858 AFY, an increase of
1,148 AFY. This technical memorandum
also provides weather-adjusted estimates of the amount of water that is
produced by non Cal-Am producers to meet existing needs in the Seaside
Groundwater Basin.
These
weather-adjusted production values for Cal-Am were compared to Cal-Am’s
recognized rights to divert water from the Carmel River and Cal-Am’s
adjudicated rights to produce groundwater from the Coastal Subareas and the
Laguna Seca Subarea of the Seaside Groundwater Basin to quantify the water
supplies that Cal-Am must develop to replace existing unlawful diversions from
the Carmel River or production in excess of its eventual adjudicated rights in
the Seaside Groundwater Basin. To comply
with SWRCB Order 95-10 and the adjudication decision in the Coastal Subareas,
Cal-Am needs to develop 10,987 AFY of replacement supplies. In addition, to continue to serve its
customers in the Laguna Seca Subarea, Cal-Am needs to develop an additional 466
AFY of replacement supplies. Also, if
Cal-Am’s recognized rights to divert Carmel River water were reduced by the
SWRCB to reflect the reduced storage capacity in Cal-Am’s Los Padres Reservoir
due to sedimentation, then Cal-Am’s replacement requirement to comply with
Order 95-10 would increase accordingly.
Based on the current estimated storage capacity in Los Padres Reservoir,
Cal-Am would need to develop an additional 762 AFY of replacement
supplies. Altogether, assuming critically-dry
conditions during the period of analysis, Cal-Am would need to develop 12,215
AFY of replacement supplies to continue to meet existing customer demand for
its systems within the District, comply with SWRCB Order 95-10, and conform
with the natural safe yield that was specified for the Seaside Groundwater
Basin in the adjudication decision. The
replacement requirements for the Cal-Am systems within the District are
summarized in Table 8.
For
this technical memorandum, it was assumed that the project or projects that
Cal-Am develops to provide the required replacement supplies would be sized to
meet existing non Cal-Am water needs in the Seaside Groundwater Basin. While Cal-Am is not directly responsible for
developing replacement supplies for the non Cal-Am producers in the Seaside
Basin, it is reasonable to assume that based on economies of scale, Cal-Am
should be able to provide the least costly replacement supplies for the non
Cal-Am producers in the Seaside Basin as part of the proposed Coastal Water
Project (CWP). This assumption is
consistent with Section III.M.1, California American Obligation to Augment
Water Supply, in the Seaside Basin adjudication decision. In this regard, non Cal-Am production values
for the Coastal Subareas and Laguna Seca Subarea were compiled and adjusted for
weather conditions, using the same factor as used for Cal-Am production. The weather-adjusted production values for
the non Cal-Am standard producers in the Coastal Subareas and the production
values for the non Cal-Am alternative producers in the Laguna Seca Subarea were
compared with the non Cal-Am standard producers’ eventual allocation in the
Coastal Subareas and with the assumed natural safe yield in the Laguna Seca
Subarea to determine non Cal-Am replacement requirements in the Seaside
Basin. These requirements for the
Coastal Subareas and Laguna Seca Subarea are 186 AFY and 86 AFY, respectively,
and are also shown in Table 8. If
these non Cal-Am replacement requirements in the Seaside Basin are summed (272
AFY) and added to Cal-Am’s replacement requirements, the total replacement
requirement is 12,487 AFY.
Based
on the analysis described above, it is recommended that the yield from any
project that is proposed to satisfy the existing water demands within the
District should be sized to provide approximately 12,500 AFY of
replacement water. This quantity,
coupled with Cal-Am’s legal supplies in the Carmel River Basin and Seaside
Groundwater Basin, should be sufficient to serve existing customer demand in
Cal-Am’s systems within the District and provide the necessary amount of
replacement water for non Cal-Am producers in the Seaside Groundwater Basin.
In
closing, it should be noted that while the replacement requirement (12,500 AFY)
recommended in this technical memorandum to meet existing water needs is within
770 AFY or 7% of the replacement requirement proposed by Cal-Am in their
application to the California Public Utilities Commission (CPUC) for a
Certificate of Public Convenience and Necessity (CPCN) to build, own, and
operate the proposed CWP (11,730 AFY), the derivation of the replacement
requirement recommended in this technical memorandum is significantly different
and represents current conditions and constraints. Specifically, the recommended requirement
provides 2,232 AFY less water for legalizing unlawful diversions by
Cal-Am from the Carmel River (10,730 AFY – 8,498 AFY = 2,232 AFY) consistent
with reduced customer demand in Cal-Am’s main distribution system during the
recent period of analysis compared to the earlier period that was used by the
SWRCB to illustrate the extent of Cal-Am’s unlawful diversions based on average
historical conditions between 1979 and 1988.
Conversely, the recommended requirement provides 2,227 AFY more
water for balancing existing Cal-Am and non Cal-Am production from the Seaside
Groundwater Basin with the natural safe yield of the Seaside Basin than
proposed by Cal-Am to address overdraft conditions in the Seaside Basin (3,227
AFY – 1,000 AFY = 2,227 AFY). Lastly,
the recommended requirement includes 762 AFY more water to replace a
portion of Cal-Am’s recognized right to store Carmel River water in Los Padres
Reservoir. This portion, which
represents the storage capacity in Los Padres Reservoir that is estimated to
have been lost to sedimentation between 1984 and 2006, was not considered in
Cal-Am’s CWP application.
U:\Darby\wp\techmemo\2006_02_demand_oct06.doc
Draft 2, November 1, 2006
[1] Cal-Am’s “main distribution system” in the Monterey Peninsula area refers to Cal-Am’s largest water distribution system in its Monterey Division. The service area for Cal-Am’s main system encompasses approximately 44 square miles and includes the cities of Carmel-by-the Sea, Del Rey Oaks, Monterey, Sand City, Seaside, and Pacific Grove, and portions of unincorporated Monterey County in the Carmel Valley, Del Monte Forest, and Carmel Highland areas. Cal-Am produces water from the Carmel River, the Carmel Valley Alluvial Aquifer, and the Coastal Subareas of the Seaside Groundwater Basin to serve customers in its main system. In 2005, Cal-Am served approximately 37,400 active connections in its main distribution system.
[2] There are approximately 40 parcels within the service area of the main Cal-Am distribution system in the Yankee Point area that are outside the District boundaries.
[3] A Water Year runs from October 1 through September 30 of the following calendar year. For example, Water Year 1996 began on October 1, 1995, and ended on September 30, 1996.
[4] A month is classified as “wet” if the unimpaired flow at the San Clemente Dam site in that month is equal to or greater than the 75% exceedence flow value. Similarly, a month is classified as “normal” if the unimpaired flow at the San Clemente Dam site is between the 75% and 25% exceedence flow values for the specified month. The month is classified as “dry” if the unimpaired flow at the San Clemente Dam site is between the 25% and 12.5% exceedence flow values. Finally, the month is classified as “critically-dry” if the unimpaired flow at the San Clemente Dam site in that month is less than the 12.5% exceedence flow value.
[5] “Wet” conditions are represented by “1”, “normal” conditions by “2”, “dry” conditions by “3”, and “critically-dry” conditions by “4”.
[6] In the Seaside Basin adjudication decision, two types of “allocations” were defined for the various producers in the basin. The first type, i.e., “Alternative Production Allocation”, referred to a fixed amount of water that could be pumped by each “Alternative Producer” from the basin each year. This first type is analogous to an “overlying” groundwater right. The second type, i.e., “Standard Production Allocation”, referred to the amount of water that a “Standard Producer” could pump each year, calculated as a percentage of the safe yield of the basin available after subtracting the Alternative Producers’ allocations. This second type is analogous to an “appropriative” groundwater right.
In California, overlying rights allow property owners to pump water from beneath their properties for use on their overlying properties. In contrast, appropriative rights allow producers to use groundwater produced from the basin on non-overlying properties or for municipal supply, which is not considered an overlying use. Overlying rights are considered prior and paramount to appropriative rights. Usually, appropriators can only pump the amount of groundwater in the basin that is surplus to the cumulative production of the overlying producers.
The “Alternative Producers” in the Laguna Seca Subarea include Pasadera Country Club, Laguna Seca Golf Ranch, York School, and Laguna Seca County Park.
[7] Letter report from Richard M. Bloyd, USGS District Chief, to Bruce Buel, MPWMD General Manager, regarding sediment deposition studies at Los Padres Reservoir in 1977, 1978, and 1980, dated February 10, 1981.