Measurement of anthropogenic and climatic impacts on groundwater values

Rachid Barry

Groundwater, which represents more than 90% of the world’s freshwater reserves, is increasingly threatened by overexploitation and pollution. However, despite the numerous scientific studies that prove it, awareness of this issue is often difficult because this vital resource is invisible. Nevertheless, it is possible to make everyone understand the stakes by translating them into monetary terms. This would facilitate the implementation of sustainable management actions.

Among the techniques for estimating the value of environmental goods, the contingent valuation method was chosen for application to the open water table of the terminal continental zone in Togo. This method is based on the econometric processing of survey data in which users reveal the value attributed to goods or services. A survey questionnaire is submitted to a sample of households selected in the study area, and the responses allow to relate the willingness to pay of users for a quantity of available water. This relationship defines the water demand function, or the marginal value function of water.

The marginal water value function is an excellent tool to translate anthropogenic and climatic impacts on groundwater into monetary values. This makes them more perceptible and understandable. Based on climate change scenarios, it will be possible to simulate groundwater availability in the future. By updating the marginal value function, the simulated availabilities will make it possible to rank the scenarios from the most expensive (little water available) to the least expensive (maximum water available). This same function will allow benefit-cost analyses to be carried out between several groundwater management options, favouring those that will favour the preservation and sustainable management of the resource.