Valuing improvements in the ecological integrity of local and regional waters using the biological condition gradient

Abstract

Scientific knowledge related to quantifying the monetized benefits for landscape-wide water quality improvements does not meet current regulatory and benefit-cost analysis needs in the United States. In this study we addressed this knowledge gap by incorporating the Biological Condition Gradient (BCG) as a water quality metric into a stated preference survey capable of estimating the total economic value (use and nonuse) for aquatic ecosystem improvements. The BCG is grounded in ecological principles and generalizable and transferable across space. Moreover, as the BCG translates available data on biological condition into a score on a 6-point scale, it provides a simple metric that can be readily communicated to the public. We applied our BCG-based survey instrument to households across the Upper Mississippi, Ohio, and Tennessee river basins and report values for a range of potential improvements that vary by location, spatial scale, and the scope of the water quality change. We found that people are willing to pay twice as much for an improvement policy that targets their home watershed (defined as a four-digit hydrologic unit) versus a more distant one. We also found that extending the spatial scale of a local policy beyond the home watershed does not generate additional benefits to the household. Finally, our results suggest that nonuse sources of value (e.g., bequest value, intrinsic aesthetic value) are an important component of overall benefits.

Keywords: Clean Water Act; stated preferences; water pollution; willingness to pay.

Fig. 1.

Upper Mississippi, Ohio, and Tennessee river basins.

Fig. 2.

Graphics depicting six BCG levels, supported human uses, biodiversity, and visual conditions.

Fig. 3.

Visual representation of variation in BCG levels within a four-digit hydrological unit code (HUC4) watershed.

Fig. 4.

Example water quality change scenario.

Fig. 5.

Spatial distribution of local WTP for a minimum BCG level 2 policy ($ per household in the affected watershed, annual payment for 5 years).

Fig. 6.

Spatial distribution of WTP for BCG level 2 in a single watershed (highlighted with a white border) ($ per household, annual payment for 5 years).