BASIN MANAGEMENT OBJECTIVES ESQUON SUBINVENTORY UNIT Butte County Water Advisory Committee Member Rick Ponciano Contact Information Phone Number: (530) 891-8455 Email Address: rcponciano@hotmail.com Description of the Esquon Sub-Inventory Unit The Esquon Sub-Inventory Unit (SIU) covers an area of about 11,600 acres in the northern portion of the East Butte Inventory Unit. It is bordered by the Pentz SIU to the north, Western Canal SIU to the south, Cherokee SIU to the east, and Durham Dayton to the west. The Esquon SIU almost corresponds to the water service areas associated with the Durham Mutual Water Company. Agricultural land use within the SIU includes production of orchards, rice, and grain crops supported by both surface water and groundwater. In a normal year, about 27% of the Esquon SIU is in summer agricultural production supported by groundwater. Butte Creek supports a population of spring run Chinook salmon. In 1998, Rancho Esquon worked with Ducks Unlimited to install a state of the art fish ladder and screen on an existing diversion. This project was designed according to California Department of Fish and Game standards to help with the passage of spring run Chinook salmon. The biological benefits of the project are improved passage of juvenile and adult fish, and a curtailment of juvenile fish in the diversion. The water from the Rancho Esquon diversion supplies water to the orchards, rice and state, federal and private wetlands within the Esquon sub-inventory unit. The water diverted from Butte Creek is believed to help recharge groundwater in the Durham/Nelson area according to the Department of Water Resources, Northern Region. Current Conditions Land use changes primarily involve orchards with approximately 900 acres of additional almonds and walnuts. Rancho Esquon continuously updates their wells with variable speed drives and moisture probes in all their orchards and other areas to support precise irrigation. Interactions with stakeholders in the sub-unit occurs throughout the year. Management Objective To maintain the groundwater surface elevation during the peak summer irrigation season (July and August) in all aquifer systems at a level that will assure an adequate and affordable irrigation groundwater supply. It is the intent of this management objective to assure a sustainable agricultural supply of good quality water now and into the future, and to assure the water supply can be utilized without injuring groundwater quality or inducing land subsidence. The management objective is also to assure an adequate groundwater supply of adequate quality from the alluvial aquifer system for all domestic users in the SIU. Esquon 2018 BMO 1
Geologic Formations Identified In Sub-Inventory Unit Geologic formations in the Esquon SIU, from youngest (shallowest) to oldest (deepest), include: Basin Deposits Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) Fresh Water-bearing Units. In the Sacramento Valley Region of Butte County, fresh groundwater-bearing units include, from youngest (shallowest) to oldest (deepest), the Modesto, Riverbank, Laguna, Tehama and Tuscan Formations. Those included in the Esquon SIU are: Modesto Formation Tuscan Unit C (Upper Tuscan) Tuscan Unit B (Lower Tuscan) BMO Key Wells Selected for Groundwater Level Monitoring SPRING Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N02E09G01M 2001 Lower Tuscan Monitoring 114.5 99.8 20N02E09L01M 1953 Lower Tuscan Irrigation 125.5 122.7 21N02E20P01M 1995 Upper Tuscan Irrigation 129.4 115.1 FALL Well ID First Aquifer Stage 1 Alert Stage 2 Alert Well Type Record System Elev. (ft) Elev. (ft) 20N02E09G01M 2001 Lower Tuscan Monitoring 108.9 97.5 20N02E09L01M 1953 Lower Tuscan Irrigation 112.1 106.8 21N02E20P01M 1995 Upper Tuscan Irrigation 108.7 87.7 An additional domestic well (SWN 20N02E08H03) was added to the DWR monitoring network in the Esquon Sub-Inventory Unit in 2008. Its hydrograph is included in this report although the period of record is not yet long enough to establish a BMO for it. Esquon 2018 BMO 2
BMO Key Wells Selected for Groundwater Quality Monitoring Annual Groundwater Quality Measurements State Well Number Water Quality Measurement Temp. ( o C) 20N02E09M002M ph E.C. (µs/cm) 2002 19.7 7.3 388 2003 18.9 7.5 526 2004 19.6 7.10 470 2005 20.1 7.40 557 2006 20.7 7.50 507 2007 19.0 7.43 480 2008 19.6 7..24 439 2009 19.0 7.42 419 2010 19.1 7.38 427 2011 20.0 7.55 415 2012 21.4 7.17 408 2013 18.1 7.29 512 2014 20.2 5.92 443 2015 18.9 7.4 417 2016 18.0 7.2 499 2017 19.1 7.3 416 Esquon 2018 BMO 3
BMO Key Well(s) Selected for Land Subsidence Monitoring State Well Number 20N01E18L001M located in the Western Canal Water District. A Sacramento Valley-wide GPS survey was conducted during 2017. Results of the survey will be available in 2018 and will provide additional land subsidence data throughout the county. Subinventory Issues and Recommendations Monitoring Recommendation - Continue to explore options for installing multi-completion monitoring wells to more accurately measure aquifer specific water quality and levels. Supporting Data Hydrographs depicting yearly spring and fall level measurements with established alert levels. QM Questionable Measurement Note: From 2014 to 2016 monthly measurements were taken. measurements (March) should be considered the BMO level. The first of the two Esquon 2018 BMO 4
20N02E09G001M Esquon 2018 BMO 5
20N02E09L001M This well has long been a Key Well highlighted in the Butte Basin Groundwater Users Association Annual report. 20N02E09L001M is an active irrigation well, in the southern portion of the Esquon SIU. The area surrounding the well consists primarily of rice production using both surface and groundwater. The well is a deep irrigation well with shallow casing, and a groundwater level measurement record dating back to the 1950s. Groundwater levels in this well represent a mixture of the unconfined and confined portions of the aquifer system. The groundwater levels in this well were monitored on a semi-annual basis until 1991, and on a monthly basis from 1991 to about 1994. Levels are typically monitored four times a year during March, July, August and October but from 2014 to 2016, levels were monitored monthly, April through October, due to drought conditions. The figure shows that the historical spring to fall fluctuation in groundwater levels ranges 3 to 8 feet during years of normal precipitation and drought periods. Long-term comparison of spring-to-spring groundwater levels shows about a 10 foot decline in groundwater levels associated with the 1976-77 drought, followed by a similar decline between 1990 and 1994, likely associated with the 1987-92 and 1994 drought periods. The last few years show another drought related decline in elevations. Although groundwater levels in this well recovered from the 1987-94 drought to groundwater levels similar to those of the early 1980s, they declined almost 20 feet from about 2000 to 2015. Groundwater levels increased in 2016 and 2017, so the 2017 level is about 12 feet lower than in 2000. Water elevations have been monitored since 1953 at this location and the historical average depth to water, including 2017 data, is approximately 10.1 feet in the spring and 17.7 feet in the fall below ground surface. Hydrographs of spring and fall groundwater levels are on the following page. Esquon 2018 BMO 6
Esquon 2018 BMO 7
21N02E20P001M Esquon 2018 BMO 8
20N02E08H003 This is a domestic well added to the network in 2008. BMOs have not yet been established for this well due to its short record. Esquon 2018 BMO 9