No abstract

Modelos como a Equação Universal de Perdas de Solo (USLE) são utilizados para estimativas de perda de solo. Na análise da USLE, o fator R de erosividade da chuva é de importante determinação, pois é o mais é afetado pela variabilidade climática. Assim, o objetivo do trabalho é determinar a distribuição espacial da erosividade e o potencial erosivo das chuvas com base em dados de 98 e 136 estações pluviométricas distribuídas, respectivamente, no Maranhão e no Pará, no período entre os anos 2000 e 2010. O Índice de Fournier Modificado foi utilizado para determinação da erosividade das chuvas. O software Quantum Gis versão 2.18.3 foi utilizado para interpolar os dados em áreas sem registros e confeccionar os mapas de isoerosividade. A classificação e a distribuição da erosividade das chuvas revelou que 76% da região possui erosividade muito forte. Fato que pode ser explicado pelo alto índice pluviométrico da região. Assim, o estudo desenvolvido pode ser um instrumento importante de informação para o desenvolvimento de tecnologias de prevenção de erosão nos estados do Pará e Maranhão. Principalmente, ao proporcionar estimativas de erosividade através de uma reta, que é função da precipitação média anual, dado de mais fácil obtenção.

Impacts on global water resources may be intensifying due to the growing and differentiated forms of land use and occupation, which influence the water cycle and thus the maintenance of life. In the Amazon, the effect may be even worse, as it is one of the world's most vulnerable regions to these changes. This work aimed to analyze the response of the components of the water balance to changes in land use and cover in the Eastern Amazon over three decades (1980–2013). First, soil texture maps were prepared. These combined with the classes of use in each decade let us estimate the values of storage and variation in storage (ΔS) of water in the soil. The behavior of the components of the water balance [precipitation, potential evapotranspiration, actual evapotranspiration (E), and ΔS] were analyzed according to the Budyko model on the annual scale as a function of the aridity and evaporative indices. For the seasonal scale, a new parameter (y0) was introduced to explicitly represent the additional water available for E, in addition to instantaneous precipitation. The seasonality of the rains and the seasonal dynamics of storage were directly incorporated into the model developed, which allowed us to understand what the dominant control factors of water balance are. In the decade from 2000 to 2009, the remaining forest cover is only 48.91%, while the cover formed by pasture is 50.47%, meaning the water storage capacity in the soil decreased 8.1%. In the 1990s, to 1999, precipitation shows a reduction, probably as a reflection of the very strong events of La Niña and El Niño (1988–1989 and 1997–1998). Observing the sum of the surface area of water bodies in the region and the relationship of forest vs. pasture, it is possible to infer that the elevation in evapotranspiration is more related to the increase in evaporation due to the increase in the pasture area than to the reduction transpiration due to forest loss, reinforcing the hypothesis that evapotranspiration increases with pasture area.

The Itacaiúnas River basin, an important watershed for the mining sector in Brazil, has had 51% of its native forest area deforested in the last forty years. It is in the arc of deforestation of the Amazon. It has protected areas essential to local biodiversity maintenance, in addition to owning ore reserves. Here, we present the first study to assess the mean annual, seasonal, and spatialized hydrological processes, providing results on a detailed scale in the basin, including mining sites. We used five future projections of mean monthly temperature and daily precipitation as input to the MGB hydrological model to simulate how hydrological processes, such as evapotranspiration, water availability, and high flows, may change in the next 30 years. The future decrease in precipitation (−8%) and increase in temperature (10%) may strengthen the monsoon seasonal cycle and lengthen the dry month for evapotranspiration. Furthermore, some parts of the basin expect an increase in the high flows (8.1%) and a decrease in water availability (−93.6%). These results provide subsidies to develop adaptation strategies to ensure the viability of mining operations and safeguard the surrounding environment and communities.