Hydrological Thresholds for Sustainable Land Use and Land Cover Change in Amazon River Basin

Abstract:

Human interventions in terrestrial hydrological cycle fall into two major categories of flow regulations and land use and land cover change (LULCC). Interventions due to LULCC are an inevitable component of agricultural and industrial development in Amazon. In the past three decades, LULCC occurred all over Amazon River basin and Madeira, Tapajos, Xingu and Tocantins are the four sub-basins with most dramatic changes. The effects of LULCC on terrestrial hydrological cycle are well discussed in previous studies, however, to the best of our knowledge large-scale, interdecadal assessment of the impact of LULCC are rare due to numerous shortcomings in data and physic-based models, and no quantitative implication for sustainability has been proposed. Previous interannual and interdecadal studies on hydrological alteration in Amazon showed an overall long-term increasing trend in terrestrial water storage (TWS), however, the southern and southeastern sub-basins are experiencing significant decreasing trends in TWS and LULCC is known as the primary component contributing to the trend. In this study, we present the hydrological thresholds for elastic changes in hydrological variables using a multi-scale assessment of Amazon River basin based on the results of validated high resolution (~2km) simulations using LEAF-Hydro-Flood model and under static and dynamic land use and land cover scenarios by keeping the other parameters of the model constant. Initial results indicate globality and locality impacts on hydrological variables and suggest that bigger sub-basins have higher thresholds and vice versa. The results suggest that as long as the change in land use and land cover is within the threshold capacity of the system, it will have negligible regional impacts in compare to local impacts and large-scale assessment of energy and water balance would fail to capture the impact of LULCC on hydrological processes. The results indicate strong ground water role in meditating the effect of LULCC on other hydrological variables which causes the change below thresholds to have insignificant effect on the regional terrestrial water cycle. The thresholds provide a rough estimation for sustainable designs in lack of comprehensive simulation of the system which includes hydrology, ecology and human interventions components.