Comparing the cost-efficiencies of different methods of evaporation suppression for agricultural reservoirs

Abstract

AbstractEvaporation losses from reservoirs can comprise a substantial proportion of their water budgets. Suppression of evaporation has been investigated mostly in terms of efficiencies but far less so in the costs per unit of water saved. Using a Unit Reference Value (URV) calculation, which is similar to a Net Present Value (NPV) levelised cost approach, the unit costs of water delivered by alternative suppression options were compared. The different technical applications were chemical monolayers, shade cloth, and hard and soft floating covers. The components of the calculation include capital, operating, and maintenance costs over a 20-year term for specified water-saving efficiencies and at different discount and evaporation rates. The unit costs of the water saved by each technology were benchmarked against water delivered by a government water supply scheme tariff and desalination. Monolayers have the lowest unit price, but have the lowest efficiency and are highly vulnerable to wind. Shade cloth covers are competitive with desalination but are limited in extent to relatively small areas. Floating hard and soft covers are more expensive, per unit price of water delivered, than desalination, a result of more frequent capital equipment replacement. Current evaporation suppression technologies are likely infeasible, cost-wise, for agricultural use. The URV provides a useful means for comparing the cost-efficiencies of different water-saving approaches.