Investigating the Effect of Land Use Change on Subsurface, Surface and Atmospheric Branches of the Hydrologic Cycle Using Observations from RELAMPAGO field Campaign in Argentina

Abstract:

Plants exert strong controls over the associated hydrologic variables through their influence on water demand and supply. Surface albedo, leaf area seasonality, surface roughness length, stomatal resistance, and root depth determine water demand and evapotranspiration. Since the 1990s, there has been a dramatic expansion of grain production systems in Argentina due to non-tillage techniques, genetically modified crops, and the demand for soybean from Asian countries. This change has had an impact on subsurface, surface and atmospheric hydroclimate variables. In this study, we analyze the meteorological station and flux tower data from a paired soy and alfalfa site at Marcos Juarez, Argentina during the period of the RELAMPAGO field campaign (2018-2019). Intercomparison reveals a higher (lower) daily latent heat (sensible heat) for alfalfa (soy) in all months except February. Water table is shallower at the soy site by more than 1 meter and this difference increases in summer months. Furthermore, specific humidity was higher (lower); outgoing shortwave radiation and soil temperature were lower (higher) in alfalfa (soy) site. State-of-the-art land surface model Noah-MP with a groundwater scheme was calibrated at both soy and alfalfa sites based on ten months of RELAMPAGO data to accurately simulate the sites consisting different vegetation. Two separate long term simulations of the calibrated model confirm that the land use change from alfalfa to soy over the years can lead to a decreasing trend in latent heat flux, increasing trend in sensible heat flux, increase in groundwater recharge, increase in runoff and decrease in water table depth. Changes in groundwater table depth was found to be more sensitive to evapotranspiration in the soy simulation.