Hydrochemical Insight and Groundwater Supply: A Case Study of Patagonia’s Chubut River

Abstract

The aim of this chapter is to assess the groundwater discharge component in the hydrological budget of NE Patagonia’s Chubut River (CHR), using 222Rn as a quantitative groundwater tracer. The main hydrological characteristics of CHR are also presented. The annual mean discharges at Valle Inferior have decreased at a mean rate of 10 m3 per decade. Anthropogenic impacts—such as wastewater discharge—are observed in surface waters. The 222Rn mass balance indicated that the groundwater inflow to the CHR ranged between 2.0 and 5.4 m3 s −1 . Thus, such groundwater inputs may account for approximately 6–24% of the total water delivered by CHR to the SW Atlantic Ocean. However, a negative flux (−1.3 m3 s −1 ) was recorded in another sampling site suggesting that the river is losing water to the aquifer. The nutrient fluxes toward the ocean were higher in winter than in spring. The silicic acid flux (1.175 106 mol d−1 ) was the highest, followed by the total inorganic nitrogen (0.08 106 mol d−1 ) and then by phosphorus (0.024 106 mol d−1 ). Such nitrogen flux would support a production rate of 7.42 106 gCd−1 . The results presented in this study indicate that SGD represents a relevant process, which takes place in the CHR’s estuarine zone.