Participatory Water Resources Modeling in a Water-Scarce Basin (Rio Sonora, Mexico) Reveals Uncertainty in Decision-Making

The Rio Sonora Basin (RSB) in northwest Mexico has a semi-arid and highly variable climate along with urban and agricultural pressures on water resources. Three participatory modeling workshops were held in the RSB in spring 2013. A model of the water resources system, consisting of a watershed hydrology model, a model of the water infrastructure, and groundwater models, was developed deliberatively in the workshops, along with scenarios of future climate and development. Participants were asked to design water resources management strategies by choosing from a range of supply augmentation and demand reduction measures associated with water conservation. Participants assessed water supply reliability, measured as the average daily supply divided by daily demand for historical and future periods, by probing with the climate and development scenarios.

Pre- and post-workshop-surveys were developed and administered, based on conceptual models of workshop participants’ beliefs regarding modeling and local water resources. The survey results indicate that participants believed their modeling abilities increased and beliefs in the utility of models increased as a result of the workshops. The selected water resources strategies varied widely among participants. Wastewater reuse for industry and aquifer recharge were popular options, but significant numbers of participants thought that inter-basin transfers and desalination were viable. The majority of participants indicated that substantial increases in agricultural water efficiency could be achieved. On average, participants chose strategies that produce reliabilities over the historical and future periods of 95%, but more than 20% of participants were apparently satisfied with reliabilities lower than 80%. The wide range of strategies chosen and associated reliabilities indicate that there is a substantial degree of uncertainty in how future water resources decisions could be made in the region.