"Evaluation of DRAINMOD Model to study Groundwater table dynamics and N load in Western Pampas, Argentina"

Abstract

<abstract> <bold>Abstract.</bold> DRAINMOD, a process-based, distributed and field-scale hydrological model , was used to study the groundwater table dynamics and Nitrogen load in agricultural fields, in western Buenos Aires Province, Argentina. The model was calibrated and validated for groundwater table depth, at 12 farm fields located within a radius of 100 km, using records from 2004 to 2012. Study sites included different soil types and groundwater table behavior was analyzed for Typic, Entic and Thapto-hapludolls. Pedotransfer functions were evaluated and applied to setup soil model inputs. A second set of observation wells were installed in 2011 to take monthly groundwater samples for studying Nitrate concentration under different crops, at three landscape positions (upper, middle and lower hill) in seven farm fields. Model performance was evaluated in order to be used as a decision support system to estimate the impact of potential management and climate scenarios, on groundwater table dynamics and N loads for different sandy and well drained to excessive well drain soils. DRAINMOD predicted Daily groundwater table depth with a Nash-Sutcliffe efficiency(NSE) values from 0.23 to 0.75, and an average RMSE of 24.9 cm. At Validation, the model presented an averagae RMSE of 39.4 cm and NSE from to 0.44 to 0.90 in seven of the eigth validation sites. As for NO3-N concentration, most of wells presented variable concentration depending on monthly precipitation and landscape position. Considering 10 mg/L NO3-N as a standard limit, 52% of the observations exceed this value, regardless N fertilization rates and mostly related to unusual precipitations events during winter 2012. Drainmod N-II validation for groundwater N will be the next step to estimate N and groundwater dynamics under different potential climatic and management scenarios.