2025 ANNUAL WATER SUPPLY AND DEMAND ASSESSMENT
FOR
FORTUNA, CALIFORNIA
Prepared for:
City of Fortuna
180 Dinsmore Drive
Fortuna, California 95540
June 2025
Prepared by:
Staff
TABLE OF CONTENTS
LIST OF APPENDICES ....................................................................................... iii
1.0 INTRODUCTION ............................................................................................1
1.1 Decision Making Process ............................................................................1
1.2 Data and Methodologies .............................................................................1
2.0 PRECIPITATION ............................................................................................2
3.0 GROUNDWATER BASIN ...............................................................................3
4.0 MUNICIPAL WELL OBSERVATIONS ............................................................7
5.0 INFRASTRUCTURE CAPABILITIES AND PLAUSIBLE CONSTRAINTS ....10
6.0 PROJECTED WATER DEMAND AND SUPPLY ..........................................10
7.0 CONCLUSIONS............................................................................................11
LIST OF APPENDICES
APPENDIX A Annual Water Supply and Demand Assessment
Reporting Tables
1.0 INTRODUCTION
The City of Fortuna’s (City's) 2025 Annual Water Supply and Demand Assessment is intended to meet the requirements established in Water Code Section 10632(a)(2) which includes the following minimum procedures:
• The written decision-making process that an urban water supplier will use each year to determine its water supply reliability. • The key data inputs and assessment methodology used to evaluate the urban water supplier’s water supply reliability for the current year and one dry year, including all of the following:
o (i) Current year unconstrained demand, considering weather, growth, and other influencing factors, such as policies to manage current supplies to meet demand objectives in future years, as applicable.
o (ii) Current year available supply, considering hydrological and regulatory conditions in the current year and one dry year. The annual supply and demand assessment may consider more than one dry year solely at the discretion of the urban water supplier. o (iii) Existing infrastructure capabilities and plausible constraints. o (iv) A defined set of locally applicable evaluation criteria that are consistently relied upon for each annual water supply and demand assessment.
o (v) A description and quantification of each source of water supply. Water Code Section 10632.1
1.1 Decision Making Process
The City's Annual Water Supply and Demand Assessment follows the methodology provided in the City of Fortuna Water Shortage Contingency Plan (FES, June 2021).
1.2 Data and Methodologies
Fortuna has prepared the 2025 Annual Water Supply and Demand Assessments utilizing the following data:
• Precipitation data from the National Weather Service Scotia Station; • Groundwater elevation data from CASGEM wells within the Eel River Valley Groundwater Basin;
• Projected current year unconstrained demand; and
• Projected current year available supply.
The above data was evaluated with similar methodologies and added to the analysis of water supply reliability contained in the Fortuna Water Shortage Contingency Plan (FES, June 2021).
2.0 PRECIPITATION
The City of Fortuna performed an analysis of annual precipitation totals from the nearest weather station with a near continuous historic record (1926-2025), Scotia, California.
Precipitation % of
Average
1926-2025 Statistics Inches/Year Precipitation
1927 Average Single
Year 47.67 100%
2013 Single Driest Year 16.62 36%
2020-2022 3-year Driest 29.49 63%
2013 Modeled Drought 16.62 36%
June 2024 -
May 2025 Previous 12 Months 59.84 128%
The lowest annual (calendar year) precipitation occurred in 2013 (16.62 inches). The highest annual precipitation occurred in 1998 (73.96 inches). In the previous 12 months the precipitation total is 128% (59.84 inches) of the average annual total. Total annual (calendar year) data is shown below. It is important to note that the precipitation in the past 12 months represents 128% of normal annual rainfall.
3.0 GROUNDWATER BASIN
Groundwater elevations from monitoring wells in the Eel River Valley Groundwater Basin for the annual wettest month (highest) and driest months (lowest) were plotted against annual total precipitation as seen in the examples below:
Well
Station #
Wet Season
Observations
Dry Season
Observations Drought Impacts
23181
Stable, somewhat
responsive to precipitation
trends
Stable, not
responsive to
precipitation
trends
Not apparent
Well
Station #Wet Season
Observations
Dry Season
Observations Drought Impacts
36943
Stable, somewhat
responsive to
precipitation trends
Stable, not
responsive to
precipitation trends
Dry season
groundwater
elevations were
stable before and
after the 3 driest
years
Well
Station
#
Wet Season
Observations
Dry Season
Observations Drought Impacts
36944
Stable, somewhat
responsive to
precipitation trends
Stable, somewhat
responsive to
precipitation trends
Dry season
groundwater elevations
were stable before and
after the 3 driest years
Groundwater elevation observations from the CASGEM wells indicate that groundwater levels are generally stable over the observation period and dry season groundwater elevations are generally not responsive to the periods of historic drought.
The Sustainable Groundwater Management Act (SGMA) requires the Department of Water Resources to prioritize each of California’s 515 groundwater basins and subbasins based on eight components. Basin prioritization is a technical process that utilizes the best available data and information to classify groundwater basins into one of four categories high-, medium-, low-, or very low-priority. The technical process is based on eight components that are identified in the California Water Code Section 10933(b). (1) The population overlying the basin or subbasin.
(2) The rate of current and projected growth of the population overlying the basin or subbasin.
(3) The number of public supply wells that draw from the basin or subbasin. (4) The total number of wells that draw from the basin or subbasin. (5) The irrigated acreage overlying the basin or subbasin. (6) The degree to which persons overlying the basin or subbasin rely on groundwater as their primary source of water.
(7) Any documented impacts on the groundwater within the basin or subbasin, including overdraft, subsidence, saline intrusion, and other water quality degradation.
(8) Any other information determined to be relevant by the department, including adverse impacts on local habitat and local streamflows.
According to the Eel River Valley Groundwater Sustainability Plan, 2022:
“The groundwater sustainability plan alternative (GSP Alternative) submitted to the Department of Water Resources (DWR) in December 2016 (SHN, 2016) showed that groundwater levels within the Eel River Valley Groundwater Basin (Basin) have a relatively narrow range of fluctuation and have remained generally stable over time, including during the droughts of 1976-1977, 1987-1992, and the most recent drought of 2013-2015. Groundwater elevation measurements collected over the course of the 2019 WY indicate that water levels are consistent with historical fluctuations observed in wells associated with the California Statewide Groundwater Elevation Monitoring (CASGEM) program. “
4.0 MUNICIPAL WELL OBSERVATIONS
Annual average static and pumping groundwater elevations from the City of Fortuna wells in the Eel River Valley Groundwater Basin were plotted showing the single driest year, the driest 3 years, and the well bottom as shown below.
All four wells have had damages screens which were corrected after 2002 and fefore 2014 resulting in pumping elevations being much lower than static water levels. Work on City Well # 5 continues and well # 5 is being replaced with a new well.
Observations regarding the above graphs are included in the table below:
City
Well
#
Static Water
Level
Observations
Pumping Water
Level
Observations
Drought
Impacts
Distance from
Pumping Elevation
to the Well Bottom
1 Stable Decrease
Pumping
elevations
decreased
after the driest
3 years
50-60 feet
2 Stable Decreasing
Pumping
elevations
decreased
during the
driest 3 years
50-60 feet
4 Stable Stable Slight
decrease
Pumping
elevations
decreased
during the
driest 3 years
65 -70 feet
5 Stable Decreasing
Pumping
elevations
decreased
during the
driest 3 years
20-35 feet
Conclusions regarding water source reliability include:
• Periods of dry weather appear to have an impact on the seasonally high groundwater elevations in the Eel River Valley Groundwater Basin. • Periods of dry weather appear to have a minimal impact on the seasonally low groundwater elevation trends in the Eel River Valley Groundwater Basin; and • The Fortuna water supply has been reliable even during periods of record low precipitation.
5.0 INFRASTRUCTURE CAPABILITIES AND PLAUSIBLE CONSTRAINTS The City of Fortuna relies on four groundwater wells within the Eel River groundwater basin to supply potable water to the community. This City exercises the pumps in the four wells by using them in a sequence. One plausible constraint is that well casings within the wells can become fouled and reduce their efficiency.
In that case, the City can supply the ongoing water demand of the community by using only one or two of the groundwater wells. This allows for one or two of the wells to be removed from service for maintenance when necessary, The City is in the process of replacing Well # 5 which will further increase the resilience of the Fortuna water distribution system.
6.0 PROJECTED WATER DEMAND AND SUPPLY
Projected water demand for the next 24 months is based on the demand in the previous 12 months (2024-2025) as shown below. Population is not projected to increase, and demand is expected to remain steady reflecting the seasonal trends as shown below:
Based on historical conditions and our understanding of the Eel River Groundwater Basin, water demand is not anticipated to exceed supply over the next 24 months even if historic drought conditions occur over the next 24 months.
7.0 CONCLUSIONS
This Section describes the conclusion of the 2025 Annual Water Demand and Supply Analysis.
Based on the analysis of local precipitation trends, groundwater elevation trends, observations from the City’s Wells, and documented sustainability of the Eel River Groundwater Basin, the water supply will most likely meet the projected demand over the next 24 months even if precipitation in the next 24 months is equal to historic lows.
APPENDIX A
ANNUAL WATER SUPPLY AND DEMAND ASSESSMENT REPORTING
TABLES