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Abstract
Land managers in upper catchments are being asked to make expensive changes in
land use, such as by planting trees, to attain environmental service targets, including
reduced salt loads in rivers, to meet needs of downstream towns, farms and natural
habitats. End-of-valley targets for salt loads have sometimes been set without a
quantitative model of cause and effect regarding impacts on water yields, economic
efficiency or distribution of costs and benefits among stakeholders. This paper
presents a method for calculating a ‘menu’ of technically feasible options for changes
from current to future mean water yields and salt loads from upstream catchments
having local groundwater flow systems, and the land-use changes to attain each of
these options at minimum cost. It sets the economic stage for upstream landholders to
negotiate with downstream parties future water-yield and salt-load targets, on the
basis of what it will cost to supply these ecosystem services.