Abstract
Abstract. Private water supply systems consisting of a domestic well and septic system are used throughout the world where households lack access to public water supply and sewers. In residential areas with a high housing density, septic contamination of private wells is common and associated with multiple health concerns. This situation can give rise to social dilemmas, where individual costs de-incentivize homeowners from investing in enhanced septic systems that would reduce well contamination and bring communal benefits. We combine a stylized game theoretical model with a probabilistic groundwater model to characterize how economic and hydrogeological conditions interact to produce misaligned incentives conducive to social dilemmas. The occurrence of social dilemmas depends on the relative costs of well contamination versus the cost of installing an enhanced septic treatment system and the relative probabilities of cross-contamination versus self-contamination. The game reveals three types of social dilemmas that occur in such systems, with each calling for distinct policy solutions. We demonstrate how the model can be applied to existing systems, using a case study of St. Joseph County, Indiana, where high nitrate contamination rates have raised public health concerns. This analysis represents a step towards identifying alternative policy solutions for a problem that has remained difficult to address for decades.
Highlights
Groundwater plays a critical role in supporting social and ecological systems throughout the world (Gleeson and Richter, 2018)
If neither player contaminates their own well or that of the other player, neither player wishes to upgrade to an enhanced septic system, and the Nash equilibrium is identical to the social optimum (Fig. 2a)
The type of social dilemma can serve as a guideline to understanding barriers to cooperation and policy opportunities to shift from the Nash equilibrium to the social optimum (Fig. 8)
Summary
Groundwater plays a critical role in supporting social and ecological systems throughout the world (Gleeson and Richter, 2018). The management challenge pertaining to household water systems has focused primarily on understanding the water quality, public health, and technical aspects of these systems, including source identification (Zendehbad et al, 2019) and treatment options (Juntakut et al, 2020) These analyses are directly related to questions of the severity, risk (Li et al, 2019), and the extent to which such systems should be regulated (Bremer and Harter, 2012). We re-frame the problem from the perspective of household utility, with the goal of identifying when households may benefit from policy instruments to support solutions that maximize collective welfare To address this challenges, we develop a game theoretical model to understand how social dilemmas might arise in household water systems. We review the different types of social dilemmas that may occur in such household water systems, along with a discussion of barriers and policy opportunities to support effective management strategies (Sect. 5)
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