In the world of corporate water stewardship, Volumetric Water Benefit Accounting (VWBA) is the common language. Developed by the World Resources Institute (WRI) and partners, VWBA gave the industry its first standardized playbook for calculating water benefits. It is the “GAAP” of water, foundational and widely recognized.
For corporations, this was a massive step forward. But as any CFO knows, “accounting” is not the same as “auditing,” and it certainly isn’t the same as “assurance.”
This is where the Blu Diamond Water Standard comes in.
We are often asked if Blu Diamond is a replacement for VWBA. It is not. Blu Diamond is a rigorous, deterministic implementation of VWBA. VWBA provides a broad menu of calculation methods, some based on models and some based on measurement. Blu Diamond restricts that menu to only the most precise, metered methodologies that can be underwritten by third party insurance carriers.
Here is a look into which VWBA methodologies satisfy the Blu Diamond Water Standard, and how they work together in practice.
1. VWBA is the Calculator. Blu Diamond is the Standard.
Think of VWBA as a cookbook. It offers a variety of recipes (methodologies) for calculating water benefits across different types of projects, from reforestation to leak detection. It allows for flexibility because it was designed to be broad and inclusive.
Blu Diamond is a specific certification built on top of those principles. We use the math of VWBA, but we restrict the inputs allowed in that math to ensure certainty.
As our Standard explicitly states:
“This Standard is designed to be compatible with generally accepted methods… such as the VWBA methodology, so long as they are consistent with the Standard’s core principle of quantifying the volume… in a deterministic manner.”
2. The Great Divide: Modeled vs. Deterministic
This is the most critical difference.
The VWBA guidance is pragmatic. It acknowledges that for some projects (like planting trees), you can’t easily meter the water benefit. Therefore, VWBA permits the use of models and estimates (such as the “Curve Number Method” for runoff reduction). These are “best guess” calculations based on scientific assumptions.
Blu Diamond draws a harder line.
To issue an insured Water Certificate, we cannot rely on a model that estimates what might happen. We need to know what did happen.
The Blu Diamond Standard requires deterministic data:
“All measurements… must be deterministic and not modelled or probability-based, based on direct metering and/or independently verifiable data.”
If a project uses a VWBA-approved estimation method (like a model), it is VWBA-compliant, but it would not qualify for Blu Diamond certification. We only certify what we can measure, verify, and ultimately, insure.
3. The “Integrity Layer”: Insurance
VWBA is an accounting protocol; it takes no position on financial risk. If a project fails, such as a if a repaired pipe starts leaking again, VWBA has no mechanism to make the buyer whole. The “accounting” simply changes in the next reporting cycle.
Blu Diamond adds an integrity layer that no accounting method can provide: Performance Insurance.
Every Blu Diamond project is underwritten by an investment-grade carrier. If the project fails to deliver the promised water outcomes, the insurance policy kicks in. This effectively turns the water benefit from a “sustainability claim” into a “financial asset.”
4. Methodology Mapping: What Qualifies?
Below is a breakdown of common VWBA methodologies and their eligibility under the Blu Diamond Water Standard.
| VWBA Methodology | Description | Blu Diamond Status | Why? |
Volume Treated Method | Measures water volume treated by wastewater plants or wetlands. | QUALIFIES | If the influent/effluent is continuously metered, this provides deterministic data suitable for insurance. |
Withdrawal Method | Measures reduction in water withdrawn from a source (e.g., leak repair, efficiency). | QUALIFIES | If based on “metered flows” (Option 1 in VWBA), it meets the standard. Estimates based on pump operating hours are not accepted. |
Volume Provided Method | Measures new water supply (e.g., desalination, new irrigation source). | QUALIFIES | If metered. Blu Diamond specifically covers Desalination and Repurposing under this logic. |
Curve Number Method | Estimates runoff reduction from land restoration/reforestation. | DOES NOT QUALIFY | This is a probabilistic model based on precipitation and soil assumptions, not a direct measurement of water volume. |
Recharge Method | Estimates infiltration based on surface area and soil infiltration rates. | DOES NOT QUALIFY | This calculates a theoretical volume based on “duration of inundation,” not a metered volume of water added to an aquifer. |
5. Hypothetical Industrial Reuse Project
To illustrate how a project can be both VWBA-compliant and Blu Diamond-certified, let’s look at a hypothetical example.
The Project:
A beverage manufacturing facility in a high-stress watershed installs a new on-site wastewater recycling plant. Instead of discharging effluent into the sewer, they treat it to a high standard and reuse it for cooling towers and landscape irrigation, reducing their freshwater withdrawal.
Step 1: The VWBA Calculation Under VWBA, the project developer selects the Volume Treated Method (Appendix A-6).
- Requirement: Confirm influent/effluent quality meets targets and estimate the volume.
- Allowable Data: VWBA allows this to be “estimated based on surface runoff calculations” or design capacity if meters aren’t available.
Step 2: The Blu Diamond “Hardening”
To achieve Blu Diamond Certification, the project adopts the same VWBA Volume Treated Method, but with stricter constraints:
- Metering: The facility installs continuous, tamper-proof flow meters on the treatment system’s output. “Design capacity” estimates are strictly forbidden.
- Baseline: A defensive baseline is established using historical metered freshwater use data to prove the reduction is real.
- Insurance: Because the data is deterministic (metered), Blu Diamond’s insurance carrier underwrites the performance. If the membrane fails and the water isn’t delivered, the insurance pays out.
The Result:
The buyer receives a Blu Diamond Water Certificate.
- Is it VWBA compliant? Yes. It follows the Volume Treated Method perfectly. It can be reported to CDP and GRI as a volumetric benefit.
- Is it better? Yes. Unlike a standard VWBA claim which could have been based on an engineering estimate, this certificate is backed by metered proof and an insurance policy.
The Bottom Line
You do not have to choose between adhering to global standards (VWBA) and demanding financial-grade rigor (Blu Diamond).
By selecting projects that utilize the deterministic methodologies within the VWBA framework, Blu Diamond effectively operationalizes the standard for the enterprise. We take the “accounting” of VWBA and add the “audit and insurance” required for true balance sheet protection.