Soil moisture prediction to support management in semiarid wetlands during drying episodes

Wetlands supported by groundwater in semiarid regions are extremely vulnerable to the impacts of droughts, particularly anthropized systems. During drying periods, soil water content arises as the controlling factor for environmental and ecological disturbances such as the spread of invasive plant species, the combustibility of organic soils, nutrient redistribution or soil physical disruption. The presented management tool for semiarid wetlands is supported by the Soil-Water-Atmosphere-Plant (SWAP) model for soil moisture modeling and simulation. Main input data are experimental values of soil physical and hydraulic characteristics, soil moisture measurements, vegetation growth parameters and climatic records. Decision-makers can use the calibrated datasets to predict the evolution of soil moisture under different drying scenarios in order to choose the most efficient management options for preventing soil moisture to reach critical values. The approach has been tested in the anthropized Mediterranean semiarid wetland area of Las Tablas de Daimiel National Park in central Spain. Ten vadose zone water models were successfully calibrated and validated for different soil units. Critical soil moisture conditions for invasive reed overgrowth and peat combustibility have been estimated. Simulations of a typical 2-year drought scenario indicated that critical soil moisture conditions for reed overgrowth are attained 9-10 months after flooding ceased and that peat areas colonized by reed plants become combustible (even 50% probability chance) by the end of the simulated period.