Land use as possible strategy for managing water table depth in flat basins with shallow groundwater

Abstract

In flat plains groundwater affects agricultural production outcomes and risks. Agricultural land use decisions, however, may strongly impact groundwater levels available for production. This paper explores the scope for managing groundwater levels through land use decisions in a sub-basin of the Salado River in the Argentine Pampas, a very flat area that plays a key role in world agricultural production. A spatially distributed hydrological model implemented with MIKE SHE software was used to establish the impacts of different land uses on groundwater dynamics, and to assess the interdependencies among spatially close decision-makers sharing a water table (WT). Additionally, groundwater level changes in response to climate variability were quantified. We found land use has strong effects on WT levels both for oneself (e.g. pastures can lead to significant decreases (up to 4.5 m) in WT levels) and others, in the form of strong interdependencies that exist between farmers sharing a WT where land use decisions of one farmer effect groundwater level of neighbouring farms and vice versa. However, the effectiveness to control groundwater levels through land use decisions is subject to the rather unpredictable effects of rainfall variability. The results presented in this paper provide key insights in relation to physical and social aspects that should be considered for managing groundwater levels through land use decisions, in order to avoid negative and/or maximize positive effects on agricultural production.

Influencia de los cambios en el uso del suelo y la precipitación sobre la dinámica hídrica de una cuenca de llanura extensa. Caso de estudio: Cuenca del Río Salado, Buenos Aires, Argentina

“…Se dispuso de series de precipitaciones diarias en 12 pluviómetros ubicados en las inmediaciones del área de estudio (Figura 3), las que fueron recopiladas en estudios previos [21,24,32]. Las series tomadas en estas estaciones estaban disponibles simultáneamente solo desde 1911 hasta 2004, ya que luego gran parte de ellas fueron dadas de baja.…”

“…Este trabajo se enmarca bajo el proyecto "From Farm Management to Governance of Landscapes: Climate, Water, and Land-Use Decisions in the Argentine Pampas" financiado por la National Science Foundation (NSF), donde previamente se estudió la posibilidad de manejar la profundidad de napa mediante el uso del suelo (a escala de cuenca y a escala de campo), la eficiencia de ese manejo bajo diferentes climas y si las decisiones de un productor afectan el nivel freático de campos aledaños [21]. En este proyecto se ha desarrollado un modelo integrado (que incluye un generador climático, un modelo hidrológico y un modelo de agentes) con el cual se pretende evaluar las implicancias que tendrían desde el punto de vista hidrológico y económico, cambios en el precio de los diferentes "commodities" o productos, cambios en la política de impuestos y en diferentes tipos de rotación de cultivos [22].…”

Groundwater Sustainability Assessment in Small Islands: The Case Study of San Andres in the Caribbean Sea

“…The world´s largest volume of unfrozen and accessible source of freshwater comes from groundwater [1][2][3], and for most nations is considered as an important resource of drinking water for agricultural and human supply [4][5][6][7]. Approximately, 25 % of humans rely on groundwater for their domestic needs and 50 % use it as potable water supply [8].…”

Ecosystem Resilience on Human Terms

“…As a result, the underlying aquifer has risen and the permeable soil and all associated vegetation, including remaining trees, has been swallowed and sent downstream (Mercau et al 2016;García et al 2018). What began as a network of small runoff channels and drainage trenches initially reported by farmers in 2008 has grown to several large ravines, the largest of which is 25 km long and measures more than 60 m wide and 25 m deep (see The Guardian, 1 April 2018, https://www.theguardian.com/ world/2018/apr/01/argentina-new-river-soya-beans).…”

“…The cause has been traced to land use changes in the watershed from forests that once absorbed increased rain (largely a consequence of climate change) to soya fields with shallow roots. As a result, the underlying aquifer has risen and the permeable soil and all associated vegetation, including remaining trees, has been swallowed and sent downstream (Mercau et al 2016;García et al 2018). This is the natural environment responding-adapting-to the human decision to exchange deep-rooted forests for shallow-rooted transient crops.…”