Gains from trans-boundary water quality management in linked catchment and coastal socio-ecological systems: A case study for the Minho region

In trans-boundary catchments, national welfare maximizing rates of water quality improvement differ across nations as benefits and/or costs from water quality improvement accrue to multiple nations. Hence we need to differentiate between intra- and trans-boundary catchments because benefactors and beneficiaries from water quality improvement are not one and the same. In this paper we develop a deterministic optimal control approach to explore national and trans-national welfare maximizing rates of water pollution abatement in linked catchment and freshwater/coastal socio-ecological systems. For a case study of the Minho region (Iberian Peninsula), we estimate nation-specific water pollution abatement cost functions (based on management practice adoption) to determine and compare national and trans-national welfare maximizing rates of water pollution abatement and corresponding welfare implications. Results show that national welfare maximization leads to increased rates of water pollution (+5%), while trans-national welfare maximization leads to significant reductions in rates of water pollution (−14%) and largest welfare gains (+1.4%). Partial non-cooperation in trans-national water quality management leads to increased rates of water pollution (up to +12%) and welfare losses (up to −0.9%), though providing national welfare gains for defecting nations (up to +3.8%).