Section 3 – Groundwater

Introduction

This section of the watershed assessment publication is focused on ground water quantity and quality as well as noting rights to ground water usage within the Millerton area watershed.  Publications such as State of California Department of Water Resources’ Bulletin 135[1] (1966) have had an interest in understanding the amount and quality of ground water that may be available in non-basin areas such the foothills of the Sierra Nevada in eastern Madera and Fresno Counties.  Thirty-seven years later, the question still persists – and today there are local communities such as Oakhurst in Madera County who are dependent upon – and struggling to secure reliable and high quality ground water as their primary source.  Like Oakhurst, most – if not all foothill communities rely upon ground water sources.

Ground water management plans as mandated under Assembly Bill 3030 are required for all counties.  In the case of non-basin areas these requirements do not apply.  For Madera County, a Technical Memorandum[2] was developed as an adjunct to the AB3030 Groundwater Management Plan submitted by Todd Engineers.

Figure 21 – Well in Finegold watershed, Madera County

Water Rights

In the state of California, most ground water usage for domestic, agriculture and other uses is not regulated.  There are a few adjudicated ground water basins in the state. However, in most localities within the state, with an issuance of a permit from local authorities and based upon well standards, a property owner can drill a well and have a pump installed for his/her own domestic and agricultural purposes.

Geological Structure

The Millerton area watershed is not within an alluvial ground water basin as defined under the State of California Department of Water Resources’ publication California’s Groundwater – Bulletin 118 Update (October, 2003).  The closest alluvial groundwater basin is within the San Joaquin Hydrologic Region number 5.  Within this hydrologic region is the Madera Sub-basin (5-22.06).  The extent of the basin and the Madera Sub-basin is north of the San Joaquin River and no further east that just out of the valley floor towards Millerton Lake.  South of the San Joaquin River is the Kings Sub-basin (5-22.08) which is designated as a part of the Tulare Lake Hydrologic Region.  Near Millerton Lake the underlying geology becomes less alluvial and much greater in granitic composition.  There is less uniformity of soils formed through alluvial deposition – and a much greater prominence of fractured granitic rock formations and outcroppings, with varying depths of surface soils.

Water Quantity

Determining the amount of ground water in a specific area within the watershed area is a formidable task.  Both Madera and Fresno County attempt to determine not so much the “quantity” of water – rather they try to determine the sustainability or reliability based on well tests that are required.  According to Water Facts[3] publications from the California Department of Resources in respect to the subject of groundwater, the volume of water stored in fractured hard rocks near the surface is estimated to total less than two percent (2 percent) of the rock volume.  This percentage decreases with depth as fractures become narrower and farther apart.  This compares to water volumes stored in alluvial soils which can amount to 10-15 percent of the alluvium.

Table 9 – Porosity (in percent) of soil and rock types[4]

Relevant investigations related to quantifying ground water and determining the reliability or sustainability of sources is fairly extensive – if not conclusive.  The following significant studies have been conducted in which baseline and contemporary data may possibly be developed in order to determine long-term trends.

Comparative analysis may be a possibility as well.  For example, the Coarsegold and Oakhurst areas on the Fresno River watershed may provide potential insight as to predicting future impacts in other similar watersheds such as the adjoining Millerton area watershed.  The most significant area-wide study relevant to the Millerton Watershed is the Todd Engineers Groundwater Conditions (of) Eastern Madera County Technical Memorandum (draft) published and submitted to Madera County in March, 2002.  This study was conducted in conjunction with Madera County’s development of a ground water management plan in compliance with AB3030.  Its primary focus was on the Fresno River and Coarsegold Creek drainage, Upper Finegold Creek, as well as the Bass Lake / Willow Creek watershed which drains into the Upper San Joaquin River above Kerkhoff Reservoir.  Much of the report’s data is included within the appendices.

Within or adjoining the Millerton watershed in Fresno County, there has been basically anecdotal information regarding groundwater conditions.   Fresno County has not undertaken an area wide investigation similar to the Todd Engineers draft Technical Memorandum submitted to Madera County.  Two sessions were conducted with well drillers[5], County, State and private geologists[6] who have extensive experience in the Sierra foothill area of both counties.  These discussions indicate that the ground water situation requires further study and the implementation of a ground water monitoring program. In the Fresno Bee on October 28, 2003[7]  an article suggested that a number of wells are “drying up” in the Cressman area of Pine Ridge just above the Millerton watershed. 

Figure 22 – Interior of well in Finegold watershed, Madera County[8]

Portions of Pine Ridge are in the Kings River drainage – while other portions are a part of the Upper San Joaquin River. More recently in a portion of the Auberry area, property owners have conveyed that they have been experiencing problems with their wells and yield problem.[9]

Based on information provided by the California Department of Water Resources (DWR),[10] there are approximately 2,238 wells within the watershed study area.   The densities based on Sections (640 acres) within Township/Ranges coincide with increased parcel densities within the unincorporated areas of the watershed.  Of those wells, 955 or 43 percent are located within Township/Range 10S23E which constitutes the Big Sandy watershed in the unincorporated communities of Auberry and Tollhouse, Fresno County.  The second greatest concentration of wells (265 or 12 percent) would be in Township/Range 10S22E.  This would coincide with the unincorporated communities of Prather and Auberry, Fresno County.  By far, the greatest numbers of wells are within Fresno County (1,600 or 71 percent) versus Madera County (637 or 29 percent). When viewed in the context of watershed coverage (Madera County 100,000 acres, Fresno County 48,000 acres), the densities in Madera county equates to approximately one well per 157 acres versus one well per 30 acres within the watershed in Fresno County.  However Madera County also has a number of wells concentrated in certain areas such as North Fork.

The DWR data was limited to very finite information due to concerns of confidentiality for owners of wells.  More specific information requires the written permission of the well owner.  Well location by Township/Range-Section was provided without the following data:

· Exact geographical location of well

· Date well placed in service

· Depth of well

· Initial yield

· Re-drilled or new well

There are over 21,000 well logs in Mariposa, Madera and Fresno Counties. Eastern Madera and Fresno County within the Millerton Watershed with approximately 2,238 wells is a subset.  These well completion reports are required to be filled out and submitted to the Department of Water Resources.  The major data categories include:

·   Well Identification

·   Well Location

·   Sanitary Conditions

·   Enclosure/Housing

·   Well Construction

·   Aquifer

·   Well Production

·   Pump

It has been conveyed that DWR intends to develop a database that would provide essential data – and at the same time insure confidentiality requirements.[11]

Figure 23 – Well Count and Average Density Map by Township/Range-Section

Water Quality

The quality of ground water within the watershed study area has not been evaluated in great detail.  Individual wells for private use are not required to be tested for drinking water quality standards.  Therefore, it is difficult to determine if the ground water is naturally affected by drinking water quality constituents – or impacted by man-made sources such as wells in close proximity to septic/leach systems.

In respect to the watershed in eastern Madera County the Todd Report includes water quality test results for primary constituents of interest related to drinking water quality.  The analysis and relevancy to determining the overall quality of well water for domestic purposes is not fully known.  However indirectly, water quality information regarding exceeding drinking water standards for community systems such as Hillview[12] and Broadview Terrace related to Gross Alpha (radioactivity) in the Oakhurst area convey some level of relevance to the Millerton Watershed.

Within the watershed in Fresno County, a list of water systems that are overseen by the Environmental Health Department has been provided and are noted in the Appendices.  Similar to the Oakhurst area, information has been obtained indicating that drinking water standards – in particular Gross Alpha may – or has been exceeded.  The most noteworthy appears to be drinking water quality for Gross Alpha that has exceeded US EPA standards for community wells at the Big Sandy Rancheria in Auberry.[13]

Consumptive Water Use

 Unlike surface water appropriations and allocations, it is very difficult to ascertain what the consumption is of ground water.  Owners of private wells are not required to monitor the amount of water used through metering devices.  Public wells may have data that can be used to estimate water usage.  In the case of the Todd Engineers groundwater report for eastern Madera County, there is information on specific community and county wells and their annual production.

Summary of Findings

1.      The Millerton watershed is exclusively a non-groundwater basin region as recognized by the State of California Department of Water Resources (DWR) Bulletin 118 – California’s Groundwater.

2.      Issues related to groundwater reliability in the area have been recognized and predicted since the publication of Bulletin 135 – Madera Area Investigation in 1966.

3.      State mandated County Groundwater Management Plans under AB3030 do not include non-groundwater basins such as the Millerton area watershed.

4.      The Todd Engineers Technical Memorandum Groundwater Conditions (of) Eastern Madera County provides general principles that could be applied for an area-wide analysis.

5.      Groundwater usage for domestic, agriculture and other uses is not regulated or metered.

6.      The Millerton area watershed geological composition is non-alluvial and consists primarily of fractured granitic “bedrock”.

7.      Less than two percent (2%) of the fractured rock may contain water by volume versus 10-15% for an alluvial ground water basin.

8.      Numerous investigations from 1966 to present have attempted to quantify the amount of ground water available, its sustainability – however, the results of the investigations cannot be generalized throughout the watershed.

9.      Long-term trends may be able to be extrapolated – however, no comprehensive programs have been established to ascertain the baseline and trends.

10.  Comparative analysis may be possible – but, have limited predictive capabilities.

11.  The Oakhurst region of Madera County adjoining the Millerton watershed has significant water quantity and quality issues.

12.  There is some information in the Fresno County portion of the Millerton watershed in which well “problems” appear to be occurring.

13.  Currently, well information available from DWR for analysis is limited due to concerns of confidentiality.

14.  Water quality information is limited to community systems.  Individual systems are not required to be tested for drinking water standards.

15.  Minimum water quality standards are being exceeded for gross alpha by some community systems (Hillview and Broadview Terrace, Oakhurst) adjoining the watershed.  In Fresno County the Big Sandy Rancheria of the Auberry area appears to exceed standards for radiation.

Conclusions

1.      Problems within adjacent areas suggest the potential for problems within the Millerton watershed.

2.      The rate of ground water consumption and its quality has not been ascertained within the Millerton watershed.

3.      There is no area-wide program within the Millerton watershed to baseline, monitor and analyze groundwater quantity trends for community and private wells.

4.      There is no area-wide program within the watershed to analyze and monitor individual private wells for water quality.

5.      While there may be individual wells being monitoring, there is no area-wide program within the watershed that ascertains a groundwater profile for the watershed with emphasis in the more populated clusters.

6.      Even if there were area-wide programs within the watershed for monitoring ground water quantity and quality, there are not structures in place to share this information.

7.      There is no data sharing, educational or outreach program or information clearinghouse that could provide two-way communication to individuals and groups regarding groundwater quality and quantity within the watershed.

Section 4

02/15/06