Modelling the Effects of Historical and Future Land Cover Changes on the Hydrology of an Amazonian Basin

Camila Abe,Maycira Costa,Felipe Lobo,Evlyn Novo,Vanessa Dos Santos,Yonas Dibike

doi:10.3390/w10070932

Abstract

Land cover changes (LCC) affect the water balance (WB), changing surface runoff (SurfQ), evapotranspiration (ET), groundwater (GW) regimes, and streamflow (Q). The Tapajós Basin (southeastern Amazon) has experienced LCC over the last 40 years, with increasing LCC rates projected for the near future. Several studies have addressed the effects of climate changes on the region’s hydrology, but few have explored the effects of LCC on its hydrological regime. In this study, the Soil and Water Assessment Tool (SWAT) was applied to model the LCC effects on the hydrology of the Upper Crepori River Basin (medium Tapajós Basin), using historical and projected LCC based on conservation policies (GOV_2050) and on the “Business as Usual” trend (BAU_2050). LCC that occurred from 1973 to 2012, increased Q by 2.5%, without noticeably altering the average annual WB. The future GOV_2050 and BAU_2050 scenarios increased SurfQ by 238.87% and 300.90%, and Q by 2.53% and 2.97%, respectively, and reduced GW by 4.00% and 5.21%, and ET by 2.07% and 2.43%, respectively. Results suggest that the increase in deforestation will intensify floods and low-flow events, and that the conservation policies considered in the GOV_2050 scenario may still compromise the region’s hydrology at a comparable level to that of the BAU_2050.

Highlights

Over the last four decades, the Brazilian Amazonian ecosystem has been impacted by logging, pasture ranching, mining, expansion of the road network, and agricultural exploration [1,2,3]
The calibrated values for soil bulk density (SOL_BD), available water capacity (SOL_AWC), and saturated hydraulic conductivity (SOL_K) agrees with values indicated by Tomasella and Hodnett [36] for Amazonian soils (0.7–1.2 Mg/m3 for bulk density, around 0.7 mm·H2 O/mmsoil for available water capacity, and values up to 1000 mm/h for saturated hydraulic conductivity)
It is reported that the amount of water that infiltrates into the soil decreases from 130 mm to 60 mm throughout the dry season, rarely reaching more than 1m of Amazonian soil depth [92], which contributes to the critical reduction of GW in that season

Summary

Introduction

Over the last four decades, the Brazilian Amazonian ecosystem has been impacted by logging, pasture ranching, mining, expansion of the road network, and agricultural exploration [1,2,3]. In the Tapajós Basin (southeastern Amazon), these small-scale clearings are associated with small-scale gold mining activities, which compromise the water quality in the river [5,6]. Water 2018, 10, 932 quality and quantity of water resources, in addition to flooding indigenous lands and conservation areas, making this region a focal point for research on the impacts of river damming and land cover change (LCC) on the local hydrology [8]. Other studies in the Amazon have demonstrated the impacts of LCC on several aspects of the ecosystem, such as water quality [9,10], biodiversity [11,12], habitat fragmentation [13,14], and hydrology [15,16,17]. On the effects of LCC on the hydrology, for instance, Dos Santos et al [15]

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Conclusion