Empleo del modelo hidrológico SWAT en regiones de llanuras : Aplicación en una cuenca rural, arroyo Santa Catalina, prov. de Buenos Aires

Las regiones de llanuras son escenarios frágiles ante extremos hídricos que generan conflictos sociales, políticos y económicos. Extensas áreas son afectadas por estos extremos, en el caso de excesos hídricos la incapacidad del relieve para evacuar volúmenes importantes de agua y el aumento de niveles freáticos producen anegamientos, mientras que en sequía la disminución del recurso hídrico afecta más gravemente a la producción. Para cuantificar los procesos de extremos hídricos en la Pampa deprimida, se implementó el modelo SWAT en la cuenca del arroyo Santa Catalina (área 138 Km2). Este modelo matemático semidistribuido continuo permitió modelar el flujo subterráneo y la escorrentía superficial con el fin de analizar los impactos del uso del suelo. Se simuló un periodo de 10 años (2003-2012) con extremos de inundaciones y sequías, considerando un calentamiento de 3 años (2003-2005). La evaluación estadística diaria de los resultado muestra que SWAT puede reproducir el caudal con coeficientes de eficiencia de Nash Suftclife (NSE) de 0.66 para el periodo de calibración (2006-2007) y 0.74 para validación (2011-2012). Con los resultados se construyeron mapas de distribución del escurrimiento superficial y de la recarga del acuífero. A partir este trabajo se proponen recomendaciones a tener en presente para simular procesos hidrológicos en áreas de llanura.Plain landscapes are usually exposed to extreme hydrological events that generate social, political and economic conflicts. Large areas are affected by these extremes. In the case of water excesses, flat relief makes difficult to drain surface water away giving rise to waterlogging and groundwater table rising. Conversely, droughts affect production due to the lack of surface and ground water. To quantify extreme hydrologic processes in the "Depressed Pampa", the SWAT model was evaluated at the Santa Catalina creek Watershed (138 km2). This mathematical, continuous and semi-distributed model allowed modeling groundwater flow and surface runoff, in order to analyze the impact of land use changes. SWAT was used to simulate a 10-year period (2003-2012), with extremes of flood and drought, considering a warming-up period of 3 years (2003-2005). A statistic evaluation showed that SWAT was able to predict daily flows, with a Nash Suftclife Efficiency (NSE) of 0.66 for the calibration period (2006-2007) and 0.74 at validation (2011-2012). Model outputs were used to build maps in order to analyze surface runoff patterns, as well as groundwater recharge areas in the acuifer. In this work, some recommendations are discussed to be taken into account when hydrologic processes are simulated in flat watersheds.Facultad de Ingenierí

A Novel Approach for the Integral Management of Water Extremes in Plain Areas

Due to the socioeconomical impact of water extremes in plain areas, there is a considerable demand for suitable strategies aiding in the management of water resources and rainfed crops. Numerical models allow for the modelling of water extremes and their consequences in order to decide on management strategies. Moreover, the integration of hydrologic models with hydraulic models under continuous or event-based approaches would synergistically contribute to better forecasting of water extreme consequences under di erent scenarios. This study conducted at the Santa Catalina stream basin (Buenos Aires province, Argentina) focuses on the integration of numerical models to analyze the hydrological response of plain areas to water extremes under di erent scenarios involving the implementation of an eco-e cient infrastructure (i.e., the integration of a green infrastructure and hydraulic structures). The two models used for the integration were: the Soil and Water Assessment Tool (SWAT) and the CELDAS8 (CTSS8) hydrologic-hydraulic model. The former accounts for the processes related to the water balance (e.g., evapotranspiration, soil moisture, percolation, groundwater discharge and surface runo ), allowing for the analysis of water extremes for either dry or wet conditions. Complementarily, CTSS8 models the response of a basin to a rainfall event (e.g., runo volume, peak flow and time to peak flow, flooded surface area). A 10-year data record (2003–2012) was analyzed to test di erent green infrastructure scenarios. SWAT was able to reproduce the waterflow in the basin with Nash Sutcli e (NS) e ciency coe cients of 0.66 and 0.74 for the calibration and validation periods, respectively. The application of CTSS8 for a flood event with a return period of 10 years showed that the combination of a green infrastructure and hydraulic structures decreased the surface runo by 28%, increased the soil moisture by 10% on an average daily scale, and reduced the impact of floods by 21% during rainfall events. The integration of continuous and event-based models for studying the impact of water extremes under di erent hypothetical scenarios represents a novel approach for evaluating potential basin management strategies aimed at improving the agricultural production in plain areas.Facultad de Ciencias Agrarias y Forestale

Estimation of fecal coliforms contamination scenarios in a microbasin of the Rolling Pampa of Argentina by using a predictive model

Se evaluó la dinámica de contaminación biológica en una microcuenca con uso ganadero de la Pampa Ondulada de Argentina, mediante el coeficiente de partición bacteriano (BactKdQ) del modelo SWAT (Soil and Water Assessment Tool). Se simularon escenarios de contaminación para dos cargas ganaderas (0,5 y 1 equivalente vaca por ha), utilizando dos valores de actKdQ: el propuesto por el SWAT (175 m3 Mg-1) y uno real medido in situ (10 m3 Mg-1). Para el escenario real se corroboró la íntima relación entre los eventos de precipitaciones escurrimientos y la contaminación biológica de los cursos de agua. Los valores reales de BactKdQ, aún siendo bajos, incidieron de forma significativa en la dinámica de transporte de oliformes fecales. Por ende, es de interés la inclusión de parámetros como el BactKdQ medidos localmente y no de aquellos que el modelo SWAT incluye por defecto. Además, se pudo observar una importante concentración de coliformes fecales en la microcuenca, señalándola como un ambiente de alto riesgo de contaminación biológica, ya que para esta aplicación del SWAT todos los niveles guías fueron sobrepasados. Este trabajo destaca la relevancia de la utilización de modelos computacionales como soporte de decisiones productivas y ambientales.Biological contamination dynamic was assessed in a microbasin of the Rolling Pampa of Argentina trough the study of the bacterial partition coefficient (BactKdQ) of SWAT model (Soil and Water Assessment Tool). Biological contamination sceneries were estimated for two stocking rates (0.5 and 1 Animal Units) using two values of BactKdQ: the value set by default in SWAT model (175 m3 Mg-1) and a real value measured in situ (10 m3 Mg-1). For the real scenery, a close relationship between rainfall and runoff events and biological contamination of water courses was confirmed. Real BactKdQ values, yet still low, significantly influenced the dynamics of transport of fecal coliforms. Therefore it is of interest to include parameters such as BactKdQ measured locally instead of those that the SWAT sets as default. In addition, we observed a high concentration of fecal coliforms in the microbasin, pointing it as an environment with high risk of biological contamination, since for this application of SWAT model all the guidelines were exceeded. This work highlights the importance of using computational models to support both production and environmental decisions.Facultad de Ciencias Agrarias y Forestale

Estimation of fecal coliforms contamination scenarios in a microbasin of the Rolling Pampa of Argentina by using a predictive model

Se evaluó la dinámica de contaminación biológica en una microcuenca con uso ganadero de la Pampa Ondulada de Argentina, mediante el coeficiente de partición bacteriano (BactKdQ) del modelo SWAT (Soil and Water Assessment Tool). Se simularon escenarios de contaminación para dos cargas ganaderas (0,5 y 1 equivalente vaca por ha), utilizando dos valores de actKdQ: el propuesto por el SWAT (175 m3 Mg-1) y uno real medido in situ (10 m3 Mg-1). Para el escenario real se corroboró la íntima relación entre los eventos de precipitaciones escurrimientos y la contaminación biológica de los cursos de agua. Los valores reales de BactKdQ, aún siendo bajos, incidieron de forma significativa en la dinámica de transporte de oliformes fecales. Por ende, es de interés la inclusión de parámetros como el BactKdQ medidos localmente y no de aquellos que el modelo SWAT incluye por defecto. Además, se pudo observar una importante concentración de coliformes fecales en la microcuenca, señalándola como un ambiente de alto riesgo de contaminación biológica, ya que para esta aplicación del SWAT todos los niveles guías fueron sobrepasados. Este trabajo destaca la relevancia de la utilización de modelos computacionales como soporte de decisiones productivas y ambientales.Biological contamination dynamic was assessed in a microbasin of the Rolling Pampa of Argentina trough the study of the bacterial partition coefficient (BactKdQ) of SWAT model (Soil and Water Assessment Tool). Biological contamination sceneries were estimated for two stocking rates (0.5 and 1 Animal Units) using two values of BactKdQ: the value set by default in SWAT model (175 m3 Mg-1) and a real value measured in situ (10 m3 Mg-1). For the real scenery, a close relationship between rainfall and runoff events and biological contamination of water courses was confirmed. Real BactKdQ values, yet still low, significantly influenced the dynamics of transport of fecal coliforms. Therefore it is of interest to include parameters such as BactKdQ measured locally instead of those that the SWAT sets as default. In addition, we observed a high concentration of fecal coliforms in the microbasin, pointing it as an environment with high risk of biological contamination, since for this application of SWAT model all the guidelines were exceeded. This work highlights the importance of using computational models to support both production and environmental decisions.Facultad de Ciencias Agrarias y Forestale

Climate and soil characteristics determine where no-till management can store carbon in soils and mitigate greenhouse gas emissions

Adoption of no-till management on croplands has become a controversial approach for storing carbon in soil due to conflicting findings. Yet, no-till is still promoted as a management practice to stabilize the global climate system from additional change due to anthropogenic greenhouse gas emissions, including the 4 per mille initiative promoted through the UN Framework Convention on Climate Change. We evaluated the body of literature surrounding this practice, and found that SOC storage can be higher under no-till management in some soil types and climatic conditions even with redistribution of SOC, and contribute to reducing net greenhouse gas emissions. However, uncertainties tend to be large, which may make this approach less attractive as a contributor to stabilize the climate system compared to other options. Consequently, no-till may be better viewed as a method for reducing soil erosion, adapting to climate change, and ensuring food security, while any increase in SOC storage is a co-benefit for society in terms of reducing greenhouse gas emissions.Facultad de Ciencias Agrarias y Forestale