不断变化的国家财富 — — 为不断变化的国家财富添水

Adding Water to the Changing Wealth of Nations

Introduction

Water consumption is increasing globally due to population growth and economic expansion. This increase is compounded by the impact of climate change, historical overuse of groundwater, and declining water quality. Understanding the uses and values of water and how these are changing is crucial for developing effective water policies and management strategies.

Objective

The objective of this report is to assess the feasibility of valuing water as a natural capital asset in at least 150 countries for possible inclusion in The Changing Wealth of Nations (CWON).

Types of Water Assets

Water is categorized into several types:

• Surface Water: Freshwater found in rivers, lakes, and reservoirs.
• Groundwater: Freshwater found beneath the Earth's surface.
• Soil Water ("Green" Water): Water stored in soil that supports vegetation.
• Recycled Water ("Gray" Water): Water derived from extracting water from the environment and circulating within the economy.
• Ocean Water: Not considered for valuation as it is essentially limitless and requires industrial processes for most uses.

Valuation Approaches

Three main approaches for estimating the value of water are identified:

1. Asset-by-Asset Approach: This involves assessing the value of specific water assets (e.g., water rights) and separating water value from land value. This method is currently not feasible due to limited data on water rights trade and the complexity of separating water and land values.
2. Use-by-Use Approach: This assesses the use of water by different industries, considering water as an input to production. The value of water used is embedded in the value added of each industry. This approach requires detailed data on water usage by industry, which is currently only available for a small number of countries.
3. Service-by-Service Approach: Based on the supply of water-related ecosystem services, this approach is the most feasible at a large scale. However, it relies on incomplete environmental and economic data, meta-analyses of valuation studies, and global models with numerous assumptions, leading to low-quality estimates. New data sources and models are expected to improve these estimates in the future.

Conclusion

The three valuation approaches are consistent with the System of National Accounts (SNA) and the System of Environmental-Economic Accounting (SEEA). While the asset-by-asset and use-by-use approaches face challenges due to limited data, the service-by-service approach offers the most feasible path forward. Continued development of data sources and models will enhance the quality of estimates, making it increasingly possible to integrate water valuation into the CWON framework.