Origin and dynamics of surface water - groundwater flows that sustain the Matusagaratí Wetland, Panamá

Abstract

The Matusagaratí Wetland in the Panamanian Darien develops in fluvial environments associated with the Tuira River. The aim of this research is to determine the origin and dynamics of the water flows that sustain the Matusagaratí Wetland, studying the flows of surface water and groundwater, as well as the contributions derived from precipitation. Understanding the contributions and flows of water within the wetland acquires both hydrological and ecological significance, since flood events contribute to the accumulation of sediments and the transport and dispersal of seeds and fish larvae, playing an important role in the wetland ecosystems and vegetation variability. A monitoring network was designed as perpendicular transects to the Tuira River, encompassing wetland environments with different geomorphology and vegetation. Water flows were studied from the measurement of water levels and sampling in the Tuira River, in groundwater and in streams that drain from Filo del Tallo, also evaluating the influence of rainfall. In addition, the origin of the different sources of water that enter the wetland was assessed using stable water isotopes. The analysis show that different hydrodynamic behaviours exist along the river associated with the levee and floodplain sectors. The dynamics of the water in the Tuira River is determined by the runoff of excess rainfall, which is overlaid by a tidal regime resulting from the propagation of the tide from the estuary. This propagation causes variations in salinity along the river. The study of groundwater levels, water levels in the Tuira River and rainfall, supported by stable isotopes, allowed the identification of different environments, some of which depend mainly on the water contribution of the Tuira River, others on rainwater, and others where the contribution of water to the wetland is mixed. The results presented in this research contribute data to the generation of hydrological baseline for the understanding of the hydrological functioning of the wetland and the generation of management guidelines against the advance of anthropic activities that can modify it.