California Department of Water Resources

California consolidation candidate screening

Which California water systems border which, from EPA's own service area boundaries, and what the published figures say across each border. 2,145 bordering pairs, at a 1.11 km tolerance. A screen, not a recommendation.

What this is

Three questions decide whether two utilities are worth looking at together: who borders whom, what the published figures say across that border, and what the two would be if they were one. This page answers all three from public filings, for every pair of California systems whose service areas meet.

It is a screen and not a finding. Nothing here says two utilities should merge, and nothing here is a feasibility result. A consolidation study prices interconnection, tests hydraulics, reconciles debt covenants and asks a governing body what it wants. This page tells a person which pairs are worth starting one about.

What “bordering” means here, exactly

Two systems are listed as bordering when their service area outlines come within 1.11 km of each other. That is a proximity test rather than a touch test, and the reason is a transform this site performed: the boundary layer is simplified by about a kilometre at acquisition, which is a pixel at the scale the state map draws it and which moves every vertex. Two systems that share a boundary in EPA's file come out of that simplification up to two tolerances apart. So an exact touch test on these bytes would be a question about our own simplification, not about the world. The tolerance is one simplification tolerance, the edge count is a function of it, and the artifact records how much the count moves at half and at double.

It is not a statement that two systems share a pipe, an interconnection or a legal service boundary. Nothing in this corpus knows about pipes.

Where the borders were computed, and what a row can say about each side

Over EPA's whole national layer, before anything was filtered to this site. Until #180 the borders were computed on the map's own extract — 585 California shapes out of the 44,643 community water systems EPA draws nationally — which meant a border to a system with no page here did not exist, and a border across a state line did not exist either. The order is now the other way round: every polygon in the layer, once, and then the edges that touch what this site draws.

So 2,145 borders reach California's 585 drawn systems, of which 1,303 name a system this site publishes no page for and 45 cross a state line. Those rows are here because the border is real. A row with an unnamed side carries EPA's name for it, the primacy agency that regulates it and how EPA got its boundary, and nothing else — no loss, no size, no rates — and it sorts below every row this site can describe rather than being ranked as though it were known.

A cross-state pair may not have its loss figures compared, and this page does not compare them. Crossing a state line means crossing a primacy agency, and “water loss” is at least three different quantities across the regulators in this corpus — the licence caveat on every page here says so. The loss gap on such a row reads not comparable, which is a statement about the two regulators rather than about the two utilities.

How EPA got the boundary on each side of the 45 cross-state borders
Primacy agencyEndpoints on a cross-state edgeModelled
CA450 (0%)
94040 (100%)
IL20 (0%)
NV22 (100%)
AZ10 (0%)

The modelled share is a fact about each state and not a national average, so an edge basis is doing more work on a cross-state row than on any other: its two endpoints are drawn from two different modelled populations.

How EPA got these shapes, and why it changes the answer

EPA disclaims the spatial accuracy of this layer and names local government as the accurate source. Some of these boundaries were published by a state agency, a utility or a county; the rest are a machine learning output. The share is a fact about this state and not a national average: of 585 California service areas drawn, 581 are published, 2 are modelled, 2 are unstated.

Neighbours found, by how EPA got the boundary
Boundary basisSystemsWith a neighbourMean neighbours
published581527 (91%)5.08
modelled21 (50%)0.5
unstated22 (100%)16.5

Every pair below says which kind of edge it is. Bordering on a modelled boundary is not bordering, and a pair joined by one is a pair a person should check against a local map before spending anything on it.

The pairs

2,145 bordering pairs, between the 530 of 585 drawn systems that have at least one neighbour. Ordered by how many times larger one side is than the other, and by nothing else — a composite score over size, loss and compliance would be a judgement about how much one is worth against another, and this corpus has none to offer. Every other figure is printed for a person to weigh.

Bordering pairs, largest size difference first
The largerPeople servedLossThe smallerPeople servedLossSize ratioLoss gapTogetherEdge
Los Angeles Department Of Water And Power3,875,5668.6%Scv Water-regional261.4%149,060×7.2 pp3,875,592one modelled
Los Angeles Department Of Water And Power3,875,5668.6%Vernon Public2005.4%19,378×3.2 pp3,875,766both published
Santa Clarita Valley Water Agency282,7846.8%Scv Water-regional261.4%10,876×5.4 pp282,810one modelled
Scv Water - Santa Clarita135,28112.9%Scv Water-regional261.4%5,203×11.5 pp135,307one modelled
Ventura County Water Works District 8125,7786.3%Scv Water-regional261.4%4,838×4.8 pp125,804one modelled
Eastern Municipal Water District666,5817.3%Wmwd - Rainbow19035.7%3,508×28.4 pp666,771both published
Santa Rosa178,1275.4%Cws Rdv Hawkins8120.0%2,199×14.7 pp178,208both published
Roseville155,6129.6%Placer County Water Agency Bianchi984.2%1,588×5.5 pp155,710 †both published
Victorville135,0005.0%Apple Valley Ranchos Water - Bellview9817.1%1,378×12 pp135,098both published
Modesto Main233,3085.8%Modesto - Ceres17510.4%1,333×4.6 pp233,483both published
Eastern Municipal Water District666,5817.3%Lake Hemet MWD Garner Valley709 EPA10.1%940.2×2.8 pp667,290both published
Rancho California Water District155,0006.1%Wmwd - Rainbow19035.7%815.8×29.6 pp155,190both published
Cws Ela East Los Angeles152,4745.4%Vernon Public2005.4%762.4×0.1 pp152,674both published
Sacramento Department Of520,4074.8%Sacramento County Water Agency - Southwest Tract75913.3%685.6×8.5 pp521,166 †both published
Scv Water - Newhall17,4987.6%Scv Water-regional261.4%673×6.2 pp17,524one modelled
Apple Valley Ranchos63,5149.8%Apple Valley Ranchos Water - Bellview9817.1%648.1×7.2 pp63,612both published
Scv Water - Pinetree15,99812.6%Scv Water-regional261.4%615.3×11.2 pp16,024one modelled
Turlock72,68218.1%Modesto - C Turlock1191.2%610.8×16.9 pp72,801both published
Truckee Donner Public Utility District31,38324.5%Tdpud Hirschdale618.4%514.5×16.2 pp31,444both published
Fresno568,9648.6%Bakman Water - Rolling Hills1,1069.0%514.4×0.4 pp570,070 †both published
East Bay Municipal Utility District1,400,0009.1%Vallejo - Main2,80022.0%500×12.9 pp1,402,800 †both published
East Bay Municipal Utility District1,400,0009.1%Vallejo - Lakes2,80044.4%500×35.3 pp1,402,800 †both published
Turlock72,68218.1%Modesto - N Turlock17211.8%422.6×6.3 pp72,854both published
Los Angeles Department Of Water And Power3,875,5668.6%Scv Water - Castaic9,99911.1%387.6×2.5 pp3,885,565both published
Scv Water - Castaic9,99911.1%Scv Water-regional261.4%384.6×9.7 pp10,025one modelled
Los Angeles Department Of Water And Power3,875,5668.6%Gswc - Willowbrook10,7474.9%360.6×3.8 pp3,886,313both published
Gswc - Florence/graham63,5007.4%Vernon Public2005.4%317.5×2.1 pp63,700both published
Ceres54,51310.4%Modesto - Ceres17510.4%311.5×0.1 pp54,688both published
Gswc - Bell Bell Gardens54,8776.7%Vernon Public2005.4%274.4×1.3 pp55,077both published
San Diego1,400,0007.6%Rincon Del Diablo Municipal Water District5,1059.5%274.2×2 pp1,405,105both published
Los Angeles Department Of Water And Power3,875,5668.6%Huntington Park-city15,4377.7%251.1×0.9 pp3,891,003both published
Scv Water - Tesoro6,49938.0%Scv Water-regional261.4%250×36.6 pp6,525one modelled
Lac Waterworks District 40, Region 4 & 34208,1294.9%Cws Av Leona Valley87818.2%237×13.3 pp209,007both published
Los Angeles Department Of Water And Power3,875,5668.6%El Segundo17,2000.5%225.3×8.1 pp3,892,766both published
Los Angeles Department Of Water And Power3,875,5668.6%Scv Water - Newhall17,4987.6%221.5×1 pp3,893,064both published
Los Angeles Department Of Water And Power3,875,5668.6%Lomita20,2567.5%191.3×1.2 pp3,895,822both published
Desert Water Agency75,5239.0%Mission Springs Water District399 EPA22.0%189.3×12.9 pp75,922both published
Los Angeles Department Of Water And Power3,875,5668.6%California - American Water Company - Los Angeles District - Baldwin Hills20,7248.8%187×0.2 pp3,896,290 †both published
Galt25,76711.7%Cws Vis Mullen13825.7%186.7×14 pp25,905 †both published
Los Angeles Department Of Water And Power3,875,5668.6%Los Angeles County Waterworks District 2922,3004.3%173.8×4.3 pp3,897,866both published
Los Angeles Department Of Water And Power3,875,5668.6%South Pasadena25,329 EPA7.8%153×0.8 pp3,900,895both published
Lac Waterworks District 40, Region 4 & 34208,1294.9%Cws Av Lancaster1,38711.9%150.1×7 pp209,516both published
Los Angeles Department Of Water And Power3,875,5668.6%Liberty Utilities (park Water)26,3715.8%147×2.9 pp3,901,937both published
San Diego County3,300,0000.3%Rainbow Municipal Water District23,5008.5%140.4×8.2 pp3,323,500 †one modelled
Los Angeles Department Of Water And Power3,875,5668.6%San Fernando28,0004.1%138.4×4.5 pp3,903,566both published
Oxnard232,9797.1%California - American Water Company - Rio Plaza (el Rio)1,7099.2%136.3×2.2 pp234,688both published
Sacramento Department Of520,4074.8%California - American Water Company - Sacramento District - Arden4,1917.0%124.2×2.2 pp524,598 †both published
Rainbow Municipal Water District23,5008.5%Wmwd - Rainbow19035.7%123.7×27.1 pp23,690both published
Suburban168,8434.2%Suburban1,4372.8%117.5×1.4 pp170,280both published
Mission Springs Water District43,484 EPA13.4%Mission Springs Water District399 EPA22.0%109×8.6 pp43,883both published
Pasadena170,9507.7%Liberty Utilities (park Water)1,6194.7%105.6×3 pp172,569both published
California - American Water Company - Sacramento District - West Placer8,8612.2%Placer County Water Agency Bianchi984.2%90.4×2 pp8,959both published
Pleasanton75,96010.4%Sunol - Sfpuc84736.4%89.7×26.1 pp76,807both published
Los Angeles Department Of Water And Power3,875,5668.6%Cws Haw Hawthorne44,7186.4%86.7×2.3 pp3,920,284both published
Mission Springs Water District43,484 EPA13.4%Mission Springs Water District517 EPA17.2%84.1×3.8 pp44,001both published
California - American Water Company - Monterey District - Main92,4508.0%California - American Water Company - Monterey District - Hidden Hills1,10615.0%83.6×7.1 pp93,556both published
Huntington Park-city15,4377.7%Vernon Public2005.4%77.2×2.4 pp15,637both published
Sweetwater Springs Water District6,00023.2%Cws Rdv Noel Heights7920.0%75.9×3.2 pp6,079 †both published
Contra Costa Water District208,52814.2%Vallejo - Main2,80022.0%74.5×7.8 pp211,328both published
Contra Costa Water District208,52814.2%Vallejo - Lakes2,80044.4%74.5×30.2 pp211,328both published

Two publishers on these rows. The loss percentage is DWR's own filing. A population marked EPA is not: it is POPULATION_SERVED_COUNT from EPA's national inventory of community water systems, carried on the rows where DWR published no population of its own — it files one for other systems in this table and not for these — because a screen whose whole argument is “a small system beside a large one” cannot be read without one. DWR did not publish the figures marked EPA. What EPA publishes is the count a system reports to its primacy agency — not a census, not audited, and the retail population for some systems and the total population served for others — collected in a different year and for a different purpose than the loss figure beside it. Such a row is two agencies' figures side by side and not one agency's statement about a system.

† EPA records at least one side of this pair as selling water wholesale to other systems. Two service populations add only where neither system already serves the other, and nothing in this corpus knows who sells to whom — so the combined figure on a flagged row may count some of the same people twice, and is an upper bound rather than a sum.

The 60 pairs at the top of that ordering, of 2,145. Nothing is hidden by a rule: the rest are the pairs the ordering puts lower, which is the whole of what it means.

Borders to systems this site has no page for

1,303 of these 2,145 borders reach a system this site publishes nothing about. They are listed here rather than mixed into the ordering above, because the ordering ranks candidates and a row with one unknown side cannot be ranked — not because the border is less real. EPA drew both shapes; this corpus holds a filing for one of them.

Every cell about the other side is absent on purpose. This site does not know that system's water loss, its size, its rates or its compliance record, and a row that implied otherwise would be the worst thing this page could do. What it knows is the name EPA files it under, which primacy agency regulates it, and how EPA got its boundary.

Borders to systems with no page here, by name — 40 of 1,303
System with a filing hereIts lossThe bordering system Regulated byIts boundaryEdge
Alameda County Water District5.3%ZONE 7 WATER AGENCYCAunstatedone modelled
Alameda County Water District5.3%SANTA CLARA VALLEY WATER DISTRICTCAunstatedone modelled
Amador Water Agency - Buckhorn26.4%FOREST POINT MHCCApublishedboth published
Amador Water Agency - Buckhorn26.4%PINE GROVE COMM SERV DISTCApublishedboth published
Amador Water Agency - Buckhorn26.4%FIRST MACE MEADOW # 1CApublishedboth published
Amador Water Agency - Buckhorn26.4%FIRST MACE MEADOWS UNIT NO. 2CApublishedboth published
Amador Water Agency - Buckhorn26.4%CALAVERAS PUDCApublishedboth published
Amador Water Agency - Tanner24.3%CITY OF JACKSONCApublishedboth published
Amador Water Agency - Tanner24.3%PINE GROVE COMM SERV DISTCApublishedboth published
Amador Water Agency - Tanner24.3%CALAVERAS PUDCApublishedboth published
Amador Water Agnecy - Lk Camanche25.0%CAMANCHE NORTH SHORE INC.CApublishedboth published
American Canyon9.8%MEYERS WATER CO.CApublishedboth published
American Canyon9.8%NAPA RIVER RANCHCApublishedboth published
American Canyon9.8%MILTON ROAD WATER COMPANYCApublishedboth published
Anaheim Public5.1%PAGE AVENUE MUTUAL WATER COMPANYCApublishedboth published
Anaheim Public5.1%SERRANO WATER DISTRICTCApublishedboth published
Anderson14.0%CANYON CREEK MHPCApublishedboth published
Anderson14.0%ANDERSON MOBILE HOME PARKCApublishedboth published
Anderson14.0%SUNRISE MOBILEHOME PARKCApublishedboth published
Anderson14.0%EL RIO ESTATESCApublishedboth published
Anderson14.0%ANDERSON PARK VILLAGECApublishedboth published
Anderson14.0%SACRAMENTO RIVER RV PARKCApublishedboth published
Anderson14.0%TUCKER OAKS EAST WATER DISTRICTCApublishedboth published
Anderson14.0%COTTONWOOD WATER DISTRICTCApublishedboth published
Antioch17.3%CASA MEDANOS WATER SYSTEMCApublishedboth published
Antioch17.3%RANDALL-BOLD WATER TREATMENT PLANTCAunstatedone modelled
Antioch17.3%CCWD/BRENTWOOD WTPCAunstatedone modelled
Apple Valley Ranchos9.8%APPLE VALLEY VIEW MWCCApublishedboth published
Apple Valley Ranchos9.8%RIVER RANCH MHPCApublishedboth published
Apple Valley Ranchos9.8%NAVAJO MWCCApublishedboth published
Apple Valley Ranchos9.8%RANCHERITOS MWCCApublishedboth published
Apple Valley Ranchos9.8%THUNDERBIRD CWDCApublishedboth published
Apple Valley Ranchos9.8%PARADISE MOBILE ESTATESCApublishedboth published
Apple Valley Ranchos9.8%APPLE VALLEY VILLAGE MHECApublishedboth published
Apple Valley Ranchos9.8%BEAR VALLEY MHPCApublishedboth published
Arcadia8.4%FOOTHILL MUNICIPAL WATER DIST.CAunstatedone modelled
Arcadia8.4%HEMLOCK MUTUAL WATER CO.CApublishedboth published
Arroyo Grande6.4%CANYON CREST MUTUAL BENEFIT WCCApublishedboth published
Arroyo Grande6.4%HALCYON WATER SYSTEMCApublishedboth published
Arroyo Grande6.4%COUNTRY HILLS ESTATESCApublishedboth published

What “together” can and cannot mean

People and connections add. Prices do not. A combined service population is the sum of two filed service populations and is honest arithmetic. A combined rate is not the average of two rates, and a combined cost of service cannot be computed from two sets of filed figures without the cost allocation neither utility publishes. That is why this table has a combined population column and no combined rate column, and why it never will.

The loss gap is in percentage points between two filed figures for the years each system last filed. Those are not necessarily the same year, and a gap between two years is not a gap between two systems in one year. Both years are on the two pages the row links to.

Is a pair on this list worth a study?

This page says which borders exist and what the filings say across them. It cannot say whether two systems can be physically connected, what it would cost, what either one's debt covenants permit, or whether either governing body would consider it.

Our consolidation candidate screening takes a list like this one, adds the figures no agency publishes, and comes back with the three pairs worth a feasibility study and the reasons the rest are not.

What the screening delivers Email us about California

Sources and corrections. The borders are derived from the US EPA Office of Research and Development community water system service area boundary layer, as this site holds it: a per-state, simplified extract of the national layer. The figures across each border are the filings on the two pages each row links to, except the service populations marked EPA, which are from EPA's own national inventory for the systems DWR published none for. If a border here is wrong, it is either wrong in EPA's layer or wrong in our reading of it — tell us which.

Cite as

Municorn.us, “Consolidation candidate screening — California water systems”, Municorn water loss index, https://municorn.us/consolidation/california-water-systems/ (source filings retrieved 2026-09-12).

CC BY 4.0 — reuse and redistribution are permitted with attribution to Municorn.us and a link to this page. Terms, and the one caveat that must travel with these figures.

"Water loss" is at least three different quantities depending on the jurisdiction, and nothing here supports a comparison between states.