Ecosystem service change from lost surface water for farming in the Middle Drâa Valley, southern Morocco: an economic valuation through a replacement cost approach

ABSTRACT Water scarcity in the Middle Drâa Valley threatens self-sufficient farming, impacts agricultural production and livelihoods of the oases’ population. To compensate for the lost surface-water resources, farmers increasingly access groundwater resources for irrigation. In this paper, we test the replacement cost approach (RCA) to estimate the monetary value of irrigation water and the minimum amount of ecosystem services’ value lost in the past. A cost-based survey of 107 randomly selected farms was conducted in 2022 to assess the costs of technical substitutes farmers used to replace reduced surface water over the past 20 years. We assess and contrast the average costs across each entire oasis and at the level of each farm. Results show that the losses incurred from the loss of surface water did not follow the aridity gradient, and these losses varied due to water regulation practices, investment capacity, other income-generating activities, and others. Results suggest that the replacement is cheap per unit of metres dug, hectares, and kg of dates, providing an advantage in terms of economy of scale for large farms. The analysis provides insights into the challenges faced by small-scale farmers in accessing water and can contribute to forecasting farmers’ behavior under water scarcity.