Surface water areas significantly impacted 2014 dengue outbreaks in Guangzhou, China.

Dengue transmission in urban areas is strongly influenced by a range of biological and environmental factors, yet the key drivers still need further exploration. To better understand mechanisms of environment-mosquito-urban dengue transmission, we propose an empirical model parameterized and cross-validated from a unique dataset including viral gene sequences, vector dynamics and human dengue cases in Guangzhou, China, together with a 36-year urban environmental change maps investigated by spatiotemporal satellite image fusion. The dengue epidemics in Guangzhou are highly episodic and were not associated with annual rainfall over time. Our results indicate that urban environmental changes, especially variations in surface area covered by water in urban areas, can substantially alter the virus population and dengue transmission. The recent severe dengue outbreaks in Guangzhou may be due to the surge in an artificial lake construction, which could increase infection force between vector (mainly Aedes albopictus) and host when urban water area significantly increased. Impacts of urban environmental change on dengue dynamics may not have been thoroughly investigated in the past studies and more work needs to be done to better understand the consequences of urbanization processes in our changing world.

Physical evolution of the Three Gorges Reservoir using advanced SVM on Landsat images and SRTM DEM data.

The Three Gorges Reservoir (TGR) is one of the largest hydropower reservoirs in the world. However, changes of the important physical characteristics of the reservoir covering pre-, during-, and post- dam have not been well studied. This study analyzed the lengths and water surface areas of the TGR using advanced support vector machine method (SVM) combined Landsat images with the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), which showed an increasing trend of lengths and surface areas with variable growth rates from pre-dam period to post-dam period. The highest water level (ca. 171.5 m) was reported in 1st Jan, 2015, with the longest length of 687.8 km and largest water surface area of 1106.2 km2 during the study period. The lowest increasing magnitude of the reservoir length occurred in the first stage (2000-2005) but with the fastest magnitude of water surface area increase. The third stage (2010-2015) showed highest increase magnitude of length and lowest increase magnitude of water surface area. Meanwhile, the increased reservoir areas were mainly from cultivated land, forest land, and building land, with the biggest increase rate of cultivated land regardless of periods. Specifically, cultivated land contributed 39.1-46.0% to increased reservoir water area; the proportions were 22.6-29.6%, 22.1-24.1%, and 5.6-9.4% for forest, building land, and grassland, respectively. The study provides important data for the TGR physical evolution in the Holocene.

Evaluating water resource maintenance for lakes of the middle Doce river / Avaliação da manutenção dos recursos hídricos dos lagos do médio rio Doce

The importance of water resources to mankind and the threat level these resources have withstood due to regional and worldwide human intervention are undeniable. In the middle stretch of the Doce river basin, there are close to 170 natural lakes, located between an environmental conservation area and monoculture eucalyptus plantations, with social, economic and biological importance. Our objective was to evaluate whether the water surface area in these lakes has remained constant in the last few decades, and make inferences on the result. To that end, we measured the water surface area of 16 lakes, from satellite images obtained between May and August in the years 1977, 1979, 1981, 2000 and 2005. Total water surface area was compared considering these dates the two different areas. We did not find any changes in water surface area for these lakes in the studied images. Likewise, we did not observe reductions in any single lake for any of the studied areas. These results indicate hydrological constancy of the system, as well as of the services this group of lakes provides to society and biodiversity in its vicinity, regardless of whether the environmental matrix consists of old-growth vegetation or eucalyptus plantations.

É inegável a importância dos recursos hídricos ao Homem e o grau de ameaça que vêm sofrendo devido a intervenções humanas regionais e globais. No trecho médio da bacia do rio Doce há cerca de 170 lagos naturais, distribuídos entre área de conservação ambiental e área de monocultivo de eucalipto, com importância social, econômica e biológica. O nosso objetivo foi avaliar se a lâmina d'água total destes lagos vem se mantendo nas últimas décadas e inferir sobre esta resposta. Para isto, aferimos a lâmina d'água de 16 lagos a partir de imagens de satélite obtidas entre maio e agosto dos anos de 1977, 1979, 1981, 2000 e 2005. Esta lâmina d'água total foi comparada considerando estas datas e as duas áreas diferentes. Não encontramos alteração na lâmina d'água destes lagos nas imagens estudadas. Do mesmo modo, não observamos redução em lagos de quaisquer das áreas estudadas, isoladamente. Estes resultados apontam para uma constância hidrológica do sistema, bem como dos serviços que este conjunto de lagos presta à sociedade e à biodiversidade de seu entorno, independente da matriz ambiental ser constituída por vegetação conservada ou cultivo de eucalipto.