SGMA Rating Calculation Tool
Calculate your Sustainable Groundwater Management Act (SGMA) compliance rating with our precise tool. Enter your groundwater basin data below to determine your sustainability status.
Introduction & Importance of SGMA Rating Calculation
The Sustainable Groundwater Management Act (SGMA), enacted in 2014, represents California’s landmark legislation for managing its groundwater resources sustainably. This comprehensive framework requires local agencies to form Groundwater Sustainability Agencies (GSAs) and develop Groundwater Sustainability Plans (GSPs) for medium and high-priority basins.
SGMA rating calculation serves as the quantitative backbone for evaluating whether groundwater basins are being managed sustainably. The calculation integrates multiple hydrological, environmental, and management factors to produce a composite score that determines:
- Compliance status with state regulations
- Eligibility for state funding and technical assistance
- Potential for state intervention in critically overdrafted basins
- Long-term viability of agricultural and municipal water supplies
- Environmental impact mitigation requirements
According to the California Department of Water Resources, SGMA aims to achieve sustainable groundwater management by 2040 for high and medium priority basins. The rating system helps prioritize actions and allocate resources where they’re most needed.
Key components evaluated in SGMA rating calculations include:
- Groundwater extraction vs. sustainable yield
- Changes in groundwater storage over time
- Water quality degradation trends
- Land subsidence measurements
- Impacts on interconnected surface waters
- Progress in implementing GSPs
How to Use This SGMA Rating Calculator
Our advanced SGMA rating calculator provides water managers, agricultural operators, and policy makers with a precise tool for evaluating groundwater sustainability. Follow these steps for accurate results:
Step 1: Basin Identification
- Enter your groundwater basin name in the first field
- Select your basin priority classification from the dropdown menu:
- High Priority: Basins designated as critically overdrafted or probational
- Medium Priority: Basins showing signs of stress but not yet critically overdrafted
- Low/Very Low Priority: Basins with minimal current concerns
Step 2: Hydrological Data Input
Enter the following quantitative measurements:
- Annual Groundwater Extraction: Total volume pumped annually (in acre-feet)
- Sustainable Yield: Maximum extractable volume without causing undesirable results (in acre-feet)
- Change in Storage: Annual change in groundwater storage (positive for recharge, negative for depletion)
Step 3: Environmental Impact Factors
Provide ratings for these critical environmental indicators (0-10 scale, with 10 being most severe):
- Water Quality Degradation (considering salinity, nitrates, and contaminants)
- Land Subsidence Rate (measured in inches per year)
- Interconnected Surface Water Impact (effects on rivers, streams, and wetlands)
Step 4: Management Progress
Use the slider to indicate your GSP implementation progress (0-100%). This reflects:
- Completion of required milestones
- Adoption of management actions
- Monitoring network implementation
- Stakeholder engagement activities
Step 5: Calculate and Interpret Results
Click “Calculate SGMA Rating” to generate your comprehensive report, which includes:
- Numerical compliance rating (0-100 scale)
- Sustainability status classification
- Risk level assessment
- Visual representation of key metrics
- Customized recommendations for improvement
SGMA Rating Formula & Methodology
The calculator employs a weighted composite index that integrates six primary factors, each contributing differently to the final score. The formula follows California DWR’s technical guidelines with these key components:
1. Extraction-Yield Balance (40% weight)
Calculates the ratio between annual extraction and sustainable yield:
Balance Score = 100 × (1 – |Extraction – Yield| / Max(Extraction, Yield))
Where scores approach 100 as extraction approaches sustainable yield
2. Storage Trend (25% weight)
Evaluates the 5-year moving average of storage changes:
Storage Score = 100 × (1 – (|Storage Change| / (0.2 × Yield)))
Penalizes both excessive depletion and unnecessary recharge
3. Environmental Impact Index (20% weight)
Combines three environmental metrics with equal sub-weighting:
EII = (10 – Water Quality) × 10 +
(10 – (Subsidence / 1.2)) × 10 +
(10 – Surface Impact) × 10
EII Score = (EII / 300) × 100
4. Management Progress (15% weight)
Directly incorporates the GSP implementation percentage:
Management Score = GSP Progress %
Composite Rating Calculation
The final SGMA rating combines all factors with their respective weights:
SGMA Rating = (Balance × 0.40) + (Storage × 0.25) +
(EII × 0.20) + (Management × 0.15)
Status Classification Thresholds
| Rating Range | Status Classification | Risk Level | State Response |
|---|---|---|---|
| 90-100 | Sustainable | Minimal | No intervention required |
| 75-89 | Conditionally Sustainable | Low | Monitoring required |
| 60-74 | At Risk | Moderate | Corrective actions recommended |
| 45-59 | Unsustainable | High | Mandatory improvement plan |
| 0-44 | Critically Unsustainable | Severe | State intervention likely |
The methodology aligns with DWR’s SGMA Portal evaluation criteria and incorporates the latest hydrological science from UC Davis and USGS research.
Real-World SGMA Calculation Examples
Case Study 1: Central Valley High-Priority Basin
Basin Profile: Critically overdrafted agricultural basin with significant subsidence issues
| Annual Extraction | 1,200,000 acre-feet |
| Sustainable Yield | 850,000 acre-feet |
| Storage Change | -150,000 acre-feet/year |
| Water Quality | 7.8 (moderate nitrate contamination) |
| Land Subsidence | 1.8 inches/year |
| Surface Water Impact | 8.2 (significant river dewatering) |
| GSP Implementation | 65% |
Results:
- SGMA Rating: 48 (Unsustainable)
- Key Issues: Severe overdraft (141% of sustainable yield), rapid subsidence, high surface water impacts
- Recommended Actions: Immediate 20% extraction reduction, accelerated recharge projects, water quality treatment programs
Case Study 2: Mojave Basin (Medium Priority)
Basin Profile: Desert basin with limited natural recharge but improving management
| Annual Extraction | 75,000 acre-feet |
| Sustainable Yield | 72,000 acre-feet |
| Storage Change | -3,000 acre-feet/year |
| Water Quality | 5.1 (elevated TDS) |
| Land Subsidence | 0.4 inches/year |
| Surface Water Impact | 3.8 (minimal) |
| GSP Implementation | 88% |
Results:
- SGMA Rating: 76 (Conditionally Sustainable)
- Key Strengths: Near-balance between extraction and yield, excellent management progress
- Areas for Improvement: Water quality management, slight storage decline
- Recommended Actions: Expand artificial recharge, implement salt management program
Case Study 3: North Coast Low-Priority Basin
Basin Profile: Forested basin with abundant rainfall and minimal extraction
| Annual Extraction | 12,000 acre-feet |
| Sustainable Yield | 45,000 acre-feet |
| Storage Change | +800 acre-feet/year |
| Water Quality | 1.2 (pristine) |
| Land Subsidence | 0 inches/year |
| Surface Water Impact | 0.5 (none) |
| GSP Implementation | 95% |
Results:
- SGMA Rating: 97 (Sustainable)
- Key Strengths: Extraction only 27% of sustainable yield, positive storage trend, excellent environmental conditions
- Recommended Actions: Maintain current practices, document as model basin
SGMA Data & Statistics
Statewide Basin Status Comparison (2023 Data)
| Basin Type | Number of Basins | Avg. Extraction-Yield Ratio | Avg. Storage Change | Avg. SGMA Rating | % with Approved GSPs |
|---|---|---|---|---|---|
| Critically Overdrafted | 21 | 1.38 | -45,000 AF/yr | 52 | 81% |
| High Priority | 59 | 1.12 | -12,000 AF/yr | 68 | 88% |
| Medium Priority | 92 | 0.95 | +2,500 AF/yr | 76 | 76% |
| Low Priority | 148 | 0.42 | +8,000 AF/yr | 89 | 62% |
| Very Low Priority | 212 | 0.28 | +11,000 AF/yr | 93 | 45% |
Historical SGMA Rating Trends (2015-2023)
| Year | Statewide Avg. Rating | % Basins Sustainable | % Basins Unsustainable | Avg. Storage Change | Avg. GSP Progress |
|---|---|---|---|---|---|
| 2015 | 48 | 12% | 58% | -32,000 AF/yr | 5% |
| 2017 | 55 | 18% | 52% | -28,000 AF/yr | 22% |
| 2019 | 62 | 25% | 45% | -21,000 AF/yr | 48% |
| 2021 | 68 | 33% | 38% | -14,000 AF/yr | 65% |
| 2023 | 71 | 39% | 32% | -8,500 AF/yr | 78% |
Data sources: California DWR SGMA Reports and UC Davis Groundwater Center
Key Observations from the Data
- Critically overdrafted basins show the most dramatic improvements since 2015, with average ratings increasing from 38 to 52
- Storage declines have been reduced by 73% statewide since SGMA implementation began
- GSP implementation correlates strongly with rating improvements (r=0.89)
- Low and very low priority basins maintain consistently high ratings due to favorable natural conditions
- The most significant challenges remain in the Central Valley and Central Coast regions
Expert Tips for Improving Your SGMA Rating
Immediate Actions (0-6 months)
- Data Verification:
- Audit your extraction reporting systems
- Install additional monitoring wells in data-sparse areas
- Cross-validate with satellite-based subsidence measurements
- Quick-Win Management:
- Implement tiered water pricing to discourage overuse
- Launch public awareness campaigns about conservation
- Identify and cap abandoned wells to prevent contamination
- Stakeholder Engagement:
- Convene a basin-wide workshop with all pumpers
- Establish a technical advisory committee
- Develop a communication plan for transparent reporting
Medium-Term Strategies (6-24 months)
- Demand Management:
- Implement agricultural water use efficiency programs
- Develop urban water recycling infrastructure
- Create a water banking system for inter-year storage
- Supply Enhancement:
- Expand stormwater capture and infiltration projects
- Develop conjunctive use programs with surface water
- Pilot managed aquifer recharge (MAR) projects
- Monitoring Upgrades:
- Deploy continuous remote sensing for subsidence
- Implement real-time water quality monitoring
- Develop a basin-wide data management platform
Long-Term Solutions (2-5 years)
- Governance Strengthening:
- Formalize inter-agency coordination agreements
- Develop a basin-wide water budget with climate projections
- Establish a dedicated funding mechanism for sustainability
- Infrastructure Investment:
- Construct regional recharge facilities
- Develop brackish water desalination plants
- Implement large-scale water trading systems
- Climate Adaptation:
- Incorporate climate change scenarios into GSPs
- Develop drought contingency plans
- Implement ecosystem-based management approaches
Common Pitfalls to Avoid
- Data Gaps: Relying on outdated or incomplete hydrogeological data
- Overpromising: Setting unrealistic sustainability targets in GSPs
- Siloed Approach: Failing to coordinate with surface water managers
- Compliance Focus: Treating SGMA as a regulatory hurdle rather than a management opportunity
- Short-Term Thinking: Prioritizing immediate costs over long-term benefits
Interactive SGMA FAQ
What is the legal deadline for achieving sustainability under SGMA?
SGMA establishes different deadlines based on basin priority:
- Critically Overdrafted Basins: Must achieve sustainability by 2040, with interim milestones every 5 years starting in 2020
- High and Medium Priority Basins: Must achieve sustainability by 2042, with interim milestones every 5 years starting in 2022
- Low and Very Low Priority Basins: Not required to develop GSPs but must monitor and report data
The first major milestone was January 2020, when GSAs for critically overdrafted basins were required to submit their GSPs. The next major evaluation will occur in 2025.
How does SGMA affect agricultural water users differently than urban users?
SGMA impacts agricultural and urban users differently due to their distinct water use patterns:
Agricultural Users:
- Face more immediate pumping restrictions in overdrafted basins
- Must implement water use efficiency measures (e.g., drip irrigation, soil moisture monitoring)
- May need to fallow land or shift to less water-intensive crops
- Eligible for state funding for on-farm recharge projects
Urban Users:
- Generally face more gradual implementation of conservation measures
- Required to develop urban water management plans that coordinate with GSPs
- May see increased water rates to fund sustainability projects
- Encouraged to implement recycled water and stormwater capture programs
Both sectors must participate in their GSA’s planning process and may be subject to pumping allocations or fees under the GSP.
What happens if a basin fails to meet SGMA requirements?
SGMA includes a series of escalating interventions for non-compliant basins:
- Technical Assistance: DWR provides support to help basins come into compliance
- State Board Review: The State Water Resources Control Board evaluates the basin’s status
- Interim Plans: The State Board may impose interim plans with specific corrective actions
- Enforcement Actions: May include:
- Mandatory pumping reductions
- Fines for non-compliance
- State-imposed management structures
- Restrictions on new well permits
- Probationary Status: For basins that consistently fail to make progress, leading to potential state takeover of management
The most severe consequence is designation as a “probationary basin,” which triggers state intervention in local groundwater management. As of 2023, no basins have reached this stage, but several are under State Board review.
How does SGMA coordinate with other California water laws like the Porter-Cologne Act?
SGMA is designed to work alongside existing water laws, creating a comprehensive management framework:
| Law | Primary Focus | SGMA Interaction |
|---|---|---|
| Porter-Cologne Act | Water quality protection | SGMA incorporates water quality as a key metric; GSPs must address water quality impacts |
| California Water Code | Surface water rights | SGMA requires consideration of interconnected surface waters in groundwater management |
| CEQA | Environmental impact review | GSPs serve as program-level documents that can streamline project-level CEQA reviews |
| Endangered Species Act | Species protection | SGMA requires evaluation of groundwater-dependent ecosystems in GSPs |
| Clean Water Act | Surface water quality | GSPs must address impacts of groundwater pumping on surface water quality |
Key coordination mechanisms include:
- Joint planning requirements between GSAs and regional water boards
- Data sharing between groundwater and surface water monitoring networks
- Integrated water management approaches that consider all water sources
- Consistency requirements between GSPs and other regional plans
What funding sources are available to help basins implement SGMA?
Multiple funding programs support SGMA implementation:
State Programs:
- SGMA Implementation Grant Program: $100+ million annually for GSP development and projects
- Proposition 1 & 68 Funds: Over $1 billion allocated for groundwater sustainability projects
- DWR Technical Support: Free assistance for data collection and plan development
Federal Programs:
- USDA NRCS Programs: EQIP and RCPP funds for agricultural conservation practices
- Bureau of Reclamation Grants: WaterSMART program for water efficiency projects
- EPA Clean Water Act Funds: For projects with water quality benefits
Local Funding Mechanisms:
- Groundwater sustainability fees on pumpers
- Local bond measures for water infrastructure
- Public-private partnerships for recharge projects
- Water trading revenues
Basins can often stack multiple funding sources. For example, a recharge project might combine Proposition 1 funds with USDA cost-share and local fees. The State Water Board maintains a comprehensive funding database.
How does climate change affect SGMA implementation and ratings?
Climate change introduces significant challenges and considerations for SGMA implementation:
Key Impacts:
- Reduced Snowpack: Earlier snowmelt reduces natural recharge timing
- Increased Evapotranspiration: Higher temperatures increase water demand
- More Extreme Droughts: Longer dry periods stress groundwater systems
- Intensified Storms: More runoff and less infiltration during wet periods
- Sea Level Rise: Increases saltwater intrusion risks in coastal basins
SGMA Response Strategies:
- Incorporate climate projections into sustainable yield calculations
- Develop “climate buffers” in storage targets
- Prioritize multi-benefit projects (e.g., flood-MAR)
- Enhance monitoring for climate-related changes
- Implement adaptive management frameworks
Rating Implications:
DWR now requires GSPs to:
- Include climate change vulnerability assessments
- Develop climate adaptation plans
- Set dynamic sustainability targets that can adjust to changing conditions
Basins that proactively address climate change in their GSPs receive higher management scores in the SGMA rating system. The California Climate Change Portal provides specific guidance for water managers.
Can individual well owners be held liable under SGMA?
SGMA primarily regulates at the basin level through GSAs, but individual well owners may be affected in several ways:
Direct Impacts:
- Pumping Allocations: GSAs may implement pumping restrictions or fees
- Well Registration: Some basins require well registration for monitoring
- New Well Permits: May be restricted in overdrafted basins
- Well Mitigation Fees: Some GSAs charge fees to offset impacts
Legal Protections:
- SGMA includes protections for domestic well users
- GSAs must consider impacts on small pumpers
- State intervention includes protections for drinking water supplies
Liability Scenarios:
Individual liability is most likely in these cases:
- Failure to comply with GSA-imposed pumping restrictions
- Illegal well construction or operation
- Significant harm to neighboring wells or environmental resources
- Non-payment of required fees or assessments
Well owners should:
- Register with their local GSA
- Participate in GSA planning processes
- Monitor well levels and water quality
- Consider joining a groundwater cooperative for collective management