Key Issues
- Intensive and economically important agricultural land use
- Generally closed groundwater subbasins
- Naturally elevated TDS in surface water and groundwater
- Burdensome regulatory process for recycled water projects
Solutions
- Technically robust SNMP methodology supports findings
- SNMP quantifies the relative loading of salt and nutrient sources relative to background conditions
- SNMP supports streamlined permitting for recycled water projects
Salt and Nutrient Management Plan
Northern San Benito County
Northern San Benito County faces the salt and nutrient management
challenges of economically-important and intensive agricultural
land use, naturally elevated salt in surface water and groundwater,
and limited outflow of groundwater from the area.
The Northern San Benito County SNMP was approved by the
Central Coast Regional Water Quality Control Board in April 2014.
The San Benito County Water District (SBCWD) manages groundwater resources
throughout San Benito County, including the Bolsa, Hollister, San Juan Bautista, and
Tres Pinos subbasins in the Pajaro River watershed. Todd Groundwater prepared a
Salt and Nutrient Management Plan (SNMP) as part of the Pajaro River Watershed
Integrated Regional Water Management (IRWM) Plan Update and in accordance
with the State Water Resources Control Board’s Recycled Water Policy (Recycled
Water Policy).
Stakeholder Outreach
The Northern San Benito County SNMP included outreach to stakeholders including agricultural interests, wastewater dischargers, recycled water producers, water agencies, well owners, environmental groups, and regulatory staff.Hydrogeologic Conceptual Models
Todd Groundwater developed conceptual models of the subbasins describing the groundwater confinement, flow, and water balances.Salt and Nutrient Loading
Salt and nutrient sources are identified in the SNMP, with assessment of loading and analysis of fate and transport. Irrigated agriculture is an extensive land use, so an important focus was current cropping patterns and irrigation sources and practices. Wastewater percolation ponds and septic systems are other salt and nutrient sources. Recycled water used for landscape and agricultural irrigation is very small but growing.Existing and Future Groundwater Quality
The SNMP scope also includes evaluation of the existing and future assimilative capacity of local groundwater for key parameters including total dissolved solids and nitrate. Assimilative capacity is the difference between existing and predicted average salt and nutrient groundwater quality and Basin Plan water quality objectives. This evaluation was based on a mixing model developed by Todd Groundwater to combine current groundwater quality with projected salt and nutrient loading.Anti-Degradation Analysis
The Todd Groundwater mixing model simulations indicated that current and future increasing use of recycled water for irrigation utilizes less than 1% of the available assimilative capacity for TDS and nitrate. Increasing use of recycled water in northern San Benito County is consistent with the State’s Policy (Resolution 68-16) with respect to maintaining the high quality of waters in California. The SNMP analysis supports streamlined permitting for recycled water projects.Implementation Measures
Implementation measures are identified to manage salt and nutrient loading and to ensure continued attainment of water quality objectives and protection of beneficial uses.SNMP Monitoring Plan
The SNMP monitoring plan builds on SBCWD’s existing groundwater quality monitoring plan developed as part of the ongoing groundwater management activities.Helpful Links
The Northern San Benito County SNMP can be downloaded at: http://www.sbcwd.com/reports/Salt%20&%20Nutrient%20Management%20Planning.pdf">.The State Recycled Water Policy requiring completion of SNMPs for all basins in California can be downloaded at: http://www.waterboards.ca.gov/water_issues/programs/water_recycling_policy/docs/rwp_revtoc.pdf.
The Central Coast Regional Water Quality Control Board’s SNMP guidance document can be downloaded at: http://www.waterboards.ca.gov/centralcoast/water_issues/programs/nutrient_mgmt/docs/snmp_info_doc_trans.pdf.